Conference noted::sf

    TAU ZERO was by Poul Anderson, not Ben Bova.
    
    The Niven book is A WORLD OUT OF TIME.
    
    --- jerry

Who are you, Jerry, that you know everything!!  ( 'E's inhuman, 'E is! )

Jim.  :-)

    
    There's an extensive discussion of Bussard ramjets elsewhere in
    this conference.  Anybody remember where it is?  I think the note
    contained discussions of other drives too - i.e., this (324)
    may be a redudant note.
    
    len.
    

    Well, if you can't readily recall where the other note is, this
    one can't be very redundant.
    
    In the universe of Nicholas van Rijn, David Falkayn, and Dominic
    Flandry, Poul Anderson uses a "quantum hyperjump" drive.  Like most
    FTL drives, this one is never explained very clearly, but I gather
    the general idea is to make the whole ship teleport from point A
    to point B, rather in the manner of an electron tunneling through
    a potential barrier that it has insufficient energy to penetrate,
    or popping from one energy level to another without occupying any
    intervening states.
    
    Anderson's ships made thousands of short-range jumps every second,
    cruising along at about a light-year per day, or about 365 c.  Also,
    when you turned off the drive, you found that you had retained an
    "intrinsic velocity" left over from your launch site.  So, for
    instance, if your departure-point was traveling at 10,000 kph relative
    to your arrival point, and if you were at rest with respect to your
    departure point when you turned on the hyperdrive, you would be
    moving at the same 10,000 kph with respect to the arrival point.
    So you had to apply breaks before landing.
    
    This "intrinsic velocity" trick was lifted from the inertialess
    drive of E. E. Smith, which he used in the Lensman series.  That
    drive anulled the inertial relations between the ship and the rest
    of the universe.  The ship then accelerated by plain old reaction
    drive (or gravity drive or something, I forget) and sailed smoothly
    through the speed of light, unhindered by the various Lorenz
    transformations because it was massless.  The only limit to velocity
    was the viscocity of interstellar hydrogen.
    
    I don't think that would work.  The Anderson quantum jump sounds
    less fishy, but I'm not at ease about it either.
    
    My personal favorite is turning the ship into tachyons.  Tachyons
    have imaginary proper mass and so look mathematically reasonable
    to us when they move faster than light, but cannot move SLOWER than
    light.  Of course, they have imaginary values as measured in their
    own frame of reference, but I suppose it seems normal if you grew
    up that way...
    
    Asimov usually employs Ye Olde Hyperspaysse Jumpe, and for years
    resolutely refused to discuss what hyperspace was or how the jump
    worked.  In his recent fourth Foundation book (the title escapes
    me), he identifies it with tachyon conversion.
    
    This is certainly not the usual meaning of hyperspace.  that usually
    means a system of more than four dimensions in which our own spacetime
    is embedded.  General relativity suggests that system would have
    at least ten dimensions.  Recent theories of particle physics would
    push the number up to fourteen or so.  The general idea is that
    our spacetime is really rather wrinkled, or can be MADE to wrinkle,
    and by stepping out into hyperspace you can hop from one fold to
    another quickly, bypassing the intervening distance.
    
    But you probably knew that already.
    
    Hyperspace is also known as subspace, superspace, overspace, and
    <name>space, where <name> is some scientist, usually fictitious.
    
    Earl Wajenberg

    Re .3, .4:
    
    DIR/TITLE=JET shows note 211.  DIR/TITLE=DRIVE shows note 224.
    
    
    				-- edp

    
    How 'bout the probability drive in the Heart of Gold?
    
    :-)

     Harry Harrison's satire , BILL, THE GALACTIC HERO.

     They employed something called the "BLOATER DRIVE". The drive supposedly
     decreased the adhesion of the molecules of the ship and its contents
     so that the ship increased in size and became very tenuous. When one end
     of the ship reached the destimation, you anchored that end, and shrank the
     ship back down to size. As the story pointed out sometimes the wrong end
     got anchored end and you 'snapped' back to where you started.

     Of course they didn't explain how the ship expanded faster than the
     speed of light, and what happened when you swept up all that cosmic 
     debris upon the contraction, but technical feasibility wasn't the point 
     of the story.


     Likewise from STAR SMASHERS OF THE GALAXY RANGERS, a Tom Swift satire,
     the 'heros' employed a star drive that used a dried piece of cheese
     in a vacuum tube application which provided all sorts of wonderful
     properties. It was of course called "CHEDITE" (sp?).

     /jim

I am well aware of the other two notes having to do with space drives.  One
deals exclusively with the limitations of the Bussard ramjet, the other deals
with some sort of gravity drive.  This note is intended to eventually have a
brief description of every type of space drive, of which there are more then you
can shake a light pen at!  This note is not redundant!  RTFNT! 

Now, back to the topic...

Piers Anthony has a good one in MACROSCOPE.  It entails a model of the universe
which is a N dimensional bowl of 3 dimensional sphagetti.  To move from noodle
to noodle is a small distance, if you can leave the noodle.  Black Holes are
leaks in the surface of the noodles.  So, what you do, is turn your ship into a
black hole at the right place, and you will arrive at a place closer to your
destination.  From any noodle there are usually several other noodles you can
jump to, you just have to pick the one which will get you closest to your
destination, if you're not close enough, you jump again.  Needless to say, there
are some technical difficulties. (Ghod!  I am going to have to explain the whole
book at explain this!) 

First off, living bodies do not survive black hole compression very well, so
what you do, it break down the crew into a cell soup.  The process of
reconstruction recapitulates ontogeny. :-)  After it's soup, you turn on the
stasis field which holds everything in place, relative to everything else, and
then turn on your black hole generator, and turn the ship into a black hole.
*PoP*  You're someplace else. 

Jim.

    Re .8:
    
    I thought the discussion of anti-gravity in topic 224 was only the
    opening drive topic.  The topic also discusses magnetic drives.
    
    
    				-- edp

    OK, I got the RTFN part (no need to get huffy, I'll be the first
    to admit to a defective memory, I just wanted to mention that we've
    been at least approximately here before), but what's the last T
    for?  Turkey?  Gobble gobble gobble.  And my recollection (defective
    as it might be) is along the same lines as edp's, so there!!!
    
    But who cares anyway, it's a notable tradition to digress and repeat.
    
    len.
    

There are several wormhole drives, where you dive down a black hole
and come up somewhere else.  Tidal forces would probably destroy you 
on the way in, though.  Also, you'd probably come out in the middle 
of a quasar, which could be unpleasant.  The most notable use of this
was in "The Forever War", where they just happened to find a black 
hole within a light year of the solar system.
/jlr

One drive that might actually work was described by James Tipler, a 
genuine relativistic physicist.  Apparently you can get 
"multiply-connected space-time" by spinning an infinitely long 
cylinder of sufficient density up to near the speed of light.  This 
gives you a time machine as well as a star drive.  Actually, any form 
of faster-than-light travel amounts to a time machine.  Poul Anderson 
used it in "Avatar", and Larry Niven used it to destroy a 
civilization that didn't realize that time machines are impossible.

/jlr

In an STL drive you can either take your power source with you
(conventional Daedalus-style ships), pick it up as you go along
(Bussard ramjets), or leave it back home and carry a very long
extension cord.   This last is what Niven and Pournelle used in "The 
Mote in God's Eye".  The Moties built an interstellar light sail and 
propelled it with giant lasers mounted in the asteroid belt. 
Focussing the lasers over interstellar distances is a problem, of course.
The lasers will have some recoil, too, which would eventually knock 
anything but a serious asteroid out of orbit.  One could also imagine 
powering the ship with some kind of particle beam.  Any such scheme 
of course, has problems when you want to decelerate at the destination.  

Andrew Offut wrote a novel (whose exact name escapes me, but it was 
serialized in Analog as something like "The Galactic Railway"), that 
also used laser propulsion.  He claimed, though, that a sufficiently 
intense beam of light was self-focussing, so he could run his laser 
beams right across the galaxy.  Could this be true?  A normal light 
guide works by having a higher index of refraction in the middle of 
the guide than at the edges, thus bending the light back in by total 
internal reflection.  Don't see how that could work in a vacuum.  Is there
some odd non-linear effect at high enough intensities that might do it?
Maybe spontaneous electron-positron creation?  Or is this is just a 
story hook?

/jlr

Gravity slings are a good way to get up respectable speeds.  That's
how our first interstellar craft, Pioneer 10, was able to leave the
solar system. If you want to get up to light-speeds, though, you've
got to get reeeeally close to something going reeeeally fast.  A close
pair of neutron stars would do it.  Because of their density you can
dip down right next to them,  and they can orbit each other so closely
that their orbital velocity is a good fraction of c.  Gregory Benford
used this in "Deeper than the Darkness".  Of course, you have to find
such a handy structure to begin with.  There was another problem with
it too that made the system unstable.  I think it was that they would
lose energy through gravitational waves and so eventually collide. 

If you could do a gravity sling around every planet in the solar 
system, how fast could you go?  Something reasonable?

/jlr

Two space drives I remember (but only partly, I lost some
brains cells in the cellular soup on that last jump :-)   :

An FTL drive which would make you insane if you looked
outside of the ship while the drive was turned on.
I think this is from one of Niven's Known Space stories,
as I recall the drive took up almost all the space inside a 
#4 hull (?) which was the largest hull made. Leaving only
enough room for one pilot.

The other drive I partially recall was designed by an intelligent
super computer which almost went insane during the process of its
design.  The reason was that the computer had been programmed to
never allow humans to die as a result of its actions.  Unfortunately
the FTL drive it had designed required everyone on the the ship
to 'die' while the drive was turned on, only to return to the
world of the living on arrival.

Does anyone with a better memory than mine have any pointers to
theze stories?

    The distortion and tidal effects of black holes can be avoided by
    making them large enough and spinning them.  Spinning a black hole
    fast enough makes it form a ring; a spaceship could fly through
    a large enough black hole without going too near the hole.  I guess
    it would go through the hole in the hole.
    
    
    Re .13:
    
    When was that written?  It sounds vaguely like phase-conjugation.
    Light can be reflected in a manner that sends it directly back to its
    source, instead of the normal reflection.  For example, light coming
    from an object and passing through a frosted piece of glass (and
    becoming distorted in the process) has been reflected so that it passes
    back through the glass almost exactly, losing its distortion, and
    hitting the object again.  This may be utilized in self-targeting
    systems: Release a bubble of hydrogen into a chamber.  Shine a laser in
    the vicinity, without actually pinpointing the hydrogen (the laser is
    not enough at this point to fuse the hydrogen).  Some of the light
    hitting the hydrogen reflects to an area where is passing through an
    amplifier (becoming distorted), is reflected, passes through the
    amplifier again (becoming undistorted and more amplified!), and hits
    the hydrogen, causing it to undergo fusion.  No lenses!  The advantages
    are the target does not need to be tracked as it moves (It's
    automatic!), and almost _all_ of the energy coming from the amplifier
    hits the target; there is almost no loss because of a mismatch between
    beam size and target size or shape. 
    
    The effect can be produced in at least two ways.  One involves a
    gas (many gases will serve) and two laser beams.  When light enters
    the device, the effect is something as if one of the laser beams
    records a hologram in the area of the gas, and the other beam reads
    the hologram out.  But since the reading beam is opposite to the
    writing beam, the "copied" light leaves in a manner opposite the
    way the original light entered.
    
    There has been some talk of using an atmosphere to perform
    phase-conjugation.  I suppose it might be theoretically possible
    to take a planet nobody is using and turn it into a phase-conjugating
    mirror.  I don't know how you would control it though; since it
    is self-targeting and you will have to make it powerful enough to
    hit a dim spaceship very far away, it will also aim at anything
    else brighter in the vicinity.  Make sure you paint anything you
    don't want blown away very black!
    
    
    				-- edp

    re: -.15
    
    The second story you cite is by Isaac Asimov, most usually found
    in his collection I, Robot.  I forget the exact title of the story,
    but I believe it is the third-to-last-one in the book.  The name
    of the supercomputer is Brain, and is the brains of many Einsteins
    with the psyche of a six year old.  An interesting story.
    
    Dave "Gee, Miss Susan" Wall

    re:.17 re:.15
    
    Gee, I don't recall that story from I, ROBOT.
    
    re:.15
    
    The Niven story is "At the Core", to be found in his collection
    NEUTRON STAR.
    
    --- jerry

    re: .15, .17, & .18
    
    The story is part of I, ROBOT. (In fact, as Dave said, it is the
    third from the last in the collection.)
    
    The basic plot is pretty much as described in previous replies.
    
    					andrew

    Re .4:
    
    Earl is uncomfortable with bDoc Smith's inertialess (Bergenholm)
    drive.  Well, Doc figured it out only after a lot of careful research
    in the literature, as it was.  A lot of it he chronicled in the
    anthology _Of Worlds Beyond_, which was a collected series of
    "articles" on writing science fiction by authors.  It was originally
    published by Lloyd Arthur Esbach's Fantasy Press in the late 1940s
    in a rather limited run.  In the 1960s, Advent:Publishers reprinted
    it.  It's well worth investing in, if you can find a copy.
    
    Doc was very aware of the klimitations of relativity; he specifically
    put an apologia at the head of his first edition of _Skylark of
    Space_, since he knew his space drive violated relativity;
    consequently, he never really considered the Skylark books as science
    fiction.
    
    Steve Kallis, Jr.
    

re: .16 - phase conjugate mirrors

I don't think conjugate mirrors would help you to keep a laser on a 
distant spacecraft.  You have to bounce a tracking laser off the 
target, and by the time the tracking beam gets back to you, the 
spacecraft has moved substantially.  Over a distance of light-years, 
the spacecraft has moved by billions of miles, and your return power 
beam would miss completely.  

The self-focussing beams in Offut's story were supposedly focussed as 
they flew along, and didn't use any mirrors.

/jlr

    I am surprised no one mentioned my all time favorite: 

        	The Improbablity Drive from HHGTTG.
    

    I think it was Arthur C. Clarke who used a slower than light drive
    to power space yachts through our solar system.  They used some
    kind of sail that moved in response to light (as in visible radiation)
    pressure.  I remember reading a short story about an annual race
    using this drive.  Something like the Americas Cup races.
    
    RE: -.1
    
    .6 mentioned it but referred to it as the probablity drive.

    Re .23:
    
    Another solar sail story (one of my favorites) is "sail 25" by Jack
    Vance.
    
    [There was also "Sunjammer" by "Winston P. Sanders" in _Analog_
    in the 60s, but I forget whose pen-name that was.]
    
    Steve Kallis, Jr.
    
    P.S.: There's one technical flaw in "Sail 25," though by changing
    one word it'd be fixed.  It's Vances "hardest" "hard-sf" story.
    
    -s
    

    re:.24
    
    Winston P. Sanders was Poul Anderson.
    
    re:.23
    
    The Clarke story you're thinking of is, if memory serves, the title
    story in THE WIND FROM THE SUN. If memory serves again, it originally
    appeared in BOYS' LIFE under the title "Sunjammer" (no, not the
    same story that Steve refers to).
    
    --- jerry

        the Wind From the Sun starred in one of Clarke's collections
        of the same name.  Excellent story.
        
        Furthermore, solar sailing spaceships are a great example
        of true "hard" science fiction.  The concept stretches the
        imagination and yet is a proven scientific concept, not in
        any way fantasy.
        
        What do you expect from the guy who invented the concept
        of communications satellites!
        
        	/dave

I don't know if Clarke really invented communication satellites (the 
only profitable form of space industry), but he did get the orbit right.
I once went back and read his original article in Wireless World in 
the mid-forties; it's pretty impressive.  Not only did he figure out 
the geosynchronous orbit, but he got the transmission frequency right
(3 GHz, the optimum between atmospheric absorption and background 
radio noise.  Present-day satellite TV runs between 4 and 6 GHz.)  He 
did think, however, that ground-based TV would be impractical.  Think 
of the expense of having to set up transmission towers every 60 miles 
across an entire country!  Ridiculous.  
/jlr

    Some additions/amplifications to the collection ...
    
    Larry Niven
    
    (1) Outsider Drive (Puppeteer Drive) -- Only crazy puppeteers would
    ride in this, since they didn't understand the technology.
    
    (2) Puppeteer Drive Version 2.0 EFT -- Beowulf Shaefer field-tested
    this version for the Puppeteers (they were too smart/cowardly to do it
    themselves) at their urging and threat of blackmail in _At the Core_.
    It went faster than Version 1.0 (because it was bigger?).  I think
    Louis Wu and his mottley crew used it again in _Ringworld_.
    
    (3) Bussard Ramjet -- an oldie but goodie ... Niven certainly did
    more research on this than most SF writers.  _Protector_, _A Gift
    from the Stars_, _Footfall_, _A World out of Time_, _The Integral
    Trees_, numerful short stories.
    
    (4) Light Sail -- I believe that humans were flying one of these
    when they made first contact with the Kzin.  Used the laser to fry
    the little kitties.  Or were the Kzin flying it?  I'll research
    and fill in if this note continues.
    
    (5) Teleport Drive -- You just put your teleport transmitter in
    the tail of whatever it is you're trying to push and put the receiver
    in the nose.  Turn it on, and you pop the tail out the nose.  Leave
    it on and you go somewhere.  Not sure what happens if there is
    something in your way.  Guess this depends on the physics involved in 
    your teleporter.  I wouldn't ride in one of the darn things.  He
    use this in one story and in one tongue-in-cheek lecture at someplace
    like MIT.  
    
    Robert Forward has a good workout of Light Sails in _Flight of the
    Dragonfly_ (this book might have been written by a computer --
    certainly not by a human being).  He describes focusing a 1300 terawatt
    laser array through a 100 km plastic fresnel lens.  Later in the
    book, government funding runs out and they have to expand the lens
    to 300 km because the laser source has to be dropped back to .5um
    light (green) from 1.5 um (IR).  Forward also has the most plausible
    explanation of how you stop one of these contraptions ... by dropping
    the outside of the sail (which is mirrored on the leeward side)
    and using the resulting ring to focus back on the payload sail.
    You lose the mainsail this way ... "no deposit, no return".
    
    In _Starquake_, Forward also describes the long, ultra-dense cylinder
    method of time travel mentioned earlier in this note, a gravity
    catapault that works by generating a gravity field with an upward
    resultant and the Kerr-Metric spacewarp generator (ultra-dense rotating
    matter in a torus).
    
    Arthur Clarke describes a black-hole powered STL drive in _Imperial
    Earth_ ?-), as well as a factory for making the black holes. 
    
    Norman Spinrad, in _The Void Captain's Tale_ describes a space drive
    that is not suitable for a family notes file (probably wouldn't
    work anyway, but half the fun is trying).

    Lets get this right.  HHGTTG describes the Infinite Improbability
    Drive, as installed in the Heart of Gold.  Note that:  Infinite
    Improbability.  It works like this:
    
    IMprobability is the reverse of probability.  When the probability
    of your being at a given point in space (and if you like, time)
    is 1, theres no chance of you being anywhere else.  Lower that
    probability a bit and theres a chance that you're actally somewhere
    else.  Reverse that.  If the IMprobability of you being at point
    A is 1, you sure as hell ARE somewhere else.  Raise that improbability
    to infinity and you're eveywhere, simultaneously.  Lower the
    improbability back to 1, and you're back where you started (i.e.
    somewhere else, then take it down to 0 and you have probability
    1 that you're now where you wanted to be.  Easy huh?
    
    Problem: manufacturing the first infinite improbability generator
    to power the drive with.  Lotsa guys with string of degrees as long
    as your arm had tried, to no avail.  Then one night, a student though
    to tie the inupt of a finite improbability generator to a very strong
    Brownian motion generator, say a nice hot cup of tea, a _lo_ the
    following morning there it was:  the infinite improbability generator.
    The guy was eventually lynched by the degree holders cos they realised
    that though they didn't like not having produced it themselves,
    they realised that what they _really_ couldn't stand was a smart-arse.
    
    What Adams probably (note that too) didn't realise, is that what
    he thought was a work of fiction when he wrote it, is rooted in
    the well known and loved Heisenberg Uncertanty Principle, which
    goes along the lines of "How can we ever be sure that <hypothesis>
    is, or isn't as appropriate, <actual>?".  Answer: we can't.
    
    Throwing_down_of_the_glove_dept.:  I defy anyone to DISprove the
    Infinite Improbability Drive.
    
    _terry_ (I think)

    I wouldn't dream of trying to disprove it.  I even know how to
    implement it (in theory).  All anyone has to do is determine a 
    cargo's moment to a sufficiently exquisite degree of accuracy 
    and the cargo's position becomes correspondingly vague.
    
    		dp dx > h
                
    On the other hand, I can't figure out how to aim the thing and make
    the cargo come out in a particular desired spot.
    
    Earl Wajenberg

    re .30 - something like that is used in Rudy Rucker's "Master of
    Space and Time".  He increases the quantum length until it's big enough
    for something and then something else happens...  you know what
    I mean.  It also allows him to travel in time.
    
    len the forgetful of details.
     

    re .29, .30:
    
    Aspects of this also were treated in John W. Campbell's _The Incredible
    Planet_ and in Doc Smith's _The Galaxy Primes_.
    
    Steve Kallis, Jr.
    

    The quantum length, also known as the Planck length, is the distance
    at which the geometry of space-time becomes uncertain.  At least,
    you'd think so after making some plausible calculations involving
    both quantum mechanics and general relativity (two theories that
    have never yet seen eye to eye).  The Planck length is proportional
    to Planck's constant, which is the proportionality constant of all
    those uncertainty Principle equations.  So Rucker's mad scientist
    (Harry Gerber) was making things grossly uncertain in his
    miracle-machine.  We then add the unstated assumption that when
    the universe is uncertain, we can determine things to be as we'd
    like them rather than by chance.  Ta-da: instant cut-rate omnipotence.
    It was a fun book.
    
    Earl Wajenberg

    Thanks Earl for recalling the relevant details for me.  It was indeed
    a fun book.
    
    len.
    

    re .28, section (4) Larry Niven's use of Solar Sail
    
    In the story refered to, where humans first met those 'lovable'
    kitty cats (Kitzn or whatever) the human ship is not a solar sail
    type ship, rather it used a laser (very high power) as the method
    of propulsion - in a simliar fashion to the old ion drives.
    
    I think I remember the story correctly as I remember chuckling when
    the humans turned the ship around to cut the aliens ship in half
    with the drive-laser. The alien commander did not realise the threat
    until too late.
    
    This also resulted in the humans salvaging the alien ship and therefore
    'discovering' the drive mechanism used by the aliens and adapting
    it for their own use.
    
    Mr Magoo

    I've just checked up on the short story. Its called 'The Warriors'
    and its in the 'Tales of Known Space' collection. And the aliens
    are Kzin. Just skim reading the story it looks like the laser drive
    was powered using a bussard-ram.
    
    Mr Magoo

    Do any of you Trekkies that are keeping up with the new novels
    remember the one novel, the title slip my mind, that introduced
    a rather new concept in space drives.
    
    This was a rather unique drive.  The race the Enterprise encountered
    called it the Inversion Drive.  It worked like this:
    
    The entire mass of the ship, including everything contained within
    it was "inverted".  What this meant is that the mass became negative,
    thus allowing its existence in a negative space-time continuum.
    The mass was then accelerated along a predetermined curve in negative
    space.  This curve turned out to be the shortest distance between
    two points in our continuum.  The end result, which I still don't
    understand was "instant travel".
    
    The scary thing about this drive was that the inversion process
    started by compressing the mass of the ship into an infinitely small
    space.  Kirk describes the transport process as though somebody
    ripped away his body and left his soul behind.  He also mentioned
    that during the transport he had no sense of anything (i.e. sight,
    smell, etc.), but he could think.
    
    This is my favorite in space drives.
    
    

    re .37:
    
    I'm sure that I will be reprimanded if my memory is failing but
    I believe the novel you refer to is "The Wounded Sky" by Diane Duane.
    The reason for the title has something to do with inversion drive
    ripping the space/time continuum (been a while since I read the
    book so that is the best I can do).
    
    Do I get a gold star for answering the question first? :-) :-)
    
    Mike

    re .38
    
    Yes, I remember now.  That was one of my favorites, along with 
    the Final Reflection.  Anybody out there read this book and understand
    the inversion drive.  If so I would like to hear your opinions and
    comments about its operation.  It did fascinate me so that I am
    open for other person's views.
    

    	In the awful ST episode "Spock's Brain", the Sigma Draconis
    starship that visited the Enterprise impressed Scotty because it
    ran on ion propulsion, with our favorite engineer adding that the
    Federation could learn a thing or two from those aliens.
    
    	I know ion power is good, but I am not aware that it could be
    used in any way for light or FTL velocities.  Does anyone know how?
    
    	Larry
    

    re .40
    
    	Excuse my ignorance, but I keep seeing the term FTL.  I have
    never seen this mentioned in a SF story before, what is it?
    

    Re .41:
    
    Faster Than Light.
    
    
    				-- edp

    Re .40
    
    So far as I am aware, the only kind of ion drive made up in any
    detail is a kind of rocket, a reaction drive that spits out high-energy
    ionized gas instead of just hot gas.  No such drive has ever been
    built.  In theory, it would have high efficiency but low thrust.
    You'd use it on long trips.
    
    Anyone who could dart about on ion drive would indeed be a remarkable
    engineer, but you couldn't use the drive to exceed light-speed.
    No faster-than-light drive is more than a mixture of highly speculative
    physics and wishful thinking.  Yet.
    
    Earl Wajenberg

    I believe small prototype ion drives have in fact been built as
    part of NASA research programs.  They have been considered for
    deep space missions where their efficiency (extremely high specific
    impulse, if you're into rocketry) is a virtue because the mission
    has a long time to build up speed at very low accelerations (because
    the thrust is so low).
    
    len.
    
    

    Yes NASA has built ion drives - my cousin has been involved in the
    program for many years but all I know is that they have been built.

    Thank you for the information.  I thought they were pipe-dreams.
    
    ESW

  What do you do with all the electrons that get stripped off the reaction
  mass?  Or do you just land your ship in the middle of a lightning bolt?

  JP

    This is just a guess, but I would suppose that the electrons get
    ejected with the main reaction mass, to re-combine at their leisure,
    so that the engine leaves a trail of thin, hot, but electrically
    neutral gas.
    
    Earl Wajenberg

re:47
>  What do you do with all the electrons that get stripped off the reaction
>  mass?

Fire them out an electron gun.

Phil

    	I think your answer is correct, because that is how the Enterprise
    was able to find the Sigma Draconis starship, by following its ion
    residue trail.
    
    	Larry
    

RE: .35

I thought that mankind was losing the First Kzin War, untill the Outsiders
sold the humans on <x> an FTL drive?

Jim.

  But didn't Louis Wu always claim that the Kzin attacked before they were
ready?  That's why "the Kzin never won a war against Men".

John

    re .51 wasn't it the humans on Wonderland?
    n.b. why doesn't Niven ever mention that Luois Wu is Beowulf Schaefer's
    son (by adoption) even tho wu flies this father's ship and interacts
    with the same puppetier??

    re:.51
    
    You're correct. The story .35 relates is "The Warriors" which tells
    of mankind's first encounter with the Kzinti. It was shortly after
    that incident that Kzin went to war against mankind. And, yes, it
    the Outsiders selling the FTL drive to Wunderland that enabled
    mankind to win the first War.
    
    re:.53
    
    My memory is fuzzy, but I'm sure that it's mentioned somewhere.
    But regardless, Bey and Louis did not interact with the same
    puppeteer. There's no indication that the puppeteer that recruited
    Bey is Nessus. Nessus has only appeared in "The Soft Weapon" and
    RINGWORLD.
    
    --- jerry

    Maybe my memory is fuzzy - I'd always thought I remembered that
    Bey traveled with Nessus. Guess I'll have to go back and re-read
    my old books.

    Going back a few years here, but, I think it was Clifford Simak
    that wrote "Cities in flight" in which there was a drive called
    'spindizzies'. These devices were an anti-gravity drive with which
    whole cities could lift off the Earth to go about the universe plying
    their trade. I.E. Pittsburg left the Earth when it ran out of Iron
    ore and went to the outer colonies where the technology was needed
    and ore was plentiful.
    
    /Pete

    Actually, it was James Blish who invented the spindizzy and wrote
    the "Cities in Flight" tetralogy.  As I recall, Pittsburgh had staked
    out Mars and the first novel depicts the take-off of Scranton, leaving
    the solar system.  The other three novels concern Mayor Amalfi,
    captain of New York City.
    
    The spindizzy was an interesting gizmo.  It did nothing but control
    gravity, but it did just about everything concerned with controlling
    gravity.  As a result, it acted as a hyperdrive, as a sub-light-speed
    antigravity drive, and as a protective force field to hold air around
    the itinerant cities.
    
    Blish even invented a highly plausible-looking "fundamental equation"
    for the gravitics involved, relating gravitic and electromagnetic
    characteristics.  He re-used this equation in "Jack of Eagles" as
    part of the patter "explaining" what Danny, the psychic hero, did
    when he levitated things.
    
    The spindizzy ran off the mass of its cargo, in some sense, so it
    became more efficient the larger the cargo.  Hence it was economical
    to throw cities around, but smaller, more ordinary starships had
    to use a different form of hyperdrive, I believe.  Because of this
    size-efficiency relation, it was just barely practical to build
    giant planet-moving spindizzies.  Amalfi does this for the planet
    of He, intending only to give the colonists a bit of change to their
    axial tilt by way of climate control.  Both Amalfi and the colonists
    were very startled when He flashed out of the galaxy at more multiples
    of the speed of light than anyone had ever seen before.
    
    Later, Amalfi repeats this trick deliberately, using the spoindizzies
    of New York itself to fly a small moon.  And later still the Hevians,
    having learned how to STEER their runaway world, come back to the
    Milky Way and look up Amalfi....
    
    Earl Wajenberg
                                        
    

    Danny Caidan acting as a human spindizzy in "Jack of Eagles" reminds
    me of a couple of other psychic hyperdrives.
    
    In "Startide Rising," by David Brin, there are several hyperdrives
    popular in different parts of the galaxy.  One of them depends on
    having a powerful and well-trained Episiarch.  The Episiarchs are
    sort of an intelligent race.  Their intelligence and psychic potential
    were massively increased by another race, at the expense of sanity.
    About the only thing an Episiarch likes to do is deny things.
    Forciblly and telekinetically.  If you suggest the right things
    to deny (like distance), the Episiarch will tear open spacetime
    and drop-kick the ship to the desired (or undesired in its case)
    destination by sheer force of naked will.  Everyone considers
    Episiarchs insane, and most races consider insane the people who
    created and use them.
    
    With less angst and more whimsy, James Schmidt invented the Sheewash
    drive and gave it to the "Witches of Karres" in the book of the
    same name.  This handy drive is faster than anything known to mundane
    technology and can be produced by any telekinetically talented and
    trained child equipped with some old coat hangers.  The entire adult
    population of Karres can band together and move their planet using
    the same methods.
    
    For REAL emergencies, the witches used the Egger Route, a form of
    teleportation that could take one anywhere in space or time but
    unfortunately gave you fits immediately after use.
    
    Earl Wajenberg

In re .28 et. al.:

As I recall, Louis Wu (or was it Chmee?) eventually realizes that the
Puppeteers lured a starseed (and thus the Outsider ship that was following
it*) to the vicinity of Known Space, specifically so that Man would learn
the secret of FTL travel from the Outsiders and win the First Man-Kzin War.
The Puppeteers' motive was to breed tame Kzin by having the warlike ones
killed off in the wars with men.

					-- Roger

* So you want to know why Outsiders follow starseeds?  That information will
  cost you a trillion Stars (Credits?).

    re:.59
    
    Sorry, but I *already* know why Outsiders chase starseeds.
    
    --- jerry

    Q:  Why *do* outsiders chase starseeds?
    	
    A:  Same reason dogs chase car wheels.  Ask any dog.
    			:-)
                                                   
    		OK, why *do* outsiders chase starseeds?

    
    Because starseeds are non-sentient female Outsiders.
    
    --- jerry

re: .-1

Very nice!  But what makes you so sure?  How do you know that the 
Outsiders aren't interstellar zoologists, who want to observe the 
full life cycle of starseeds in situ?  Or that starseeds aren't the 
larval form of Outsiders and they're just watching over the brood?  
Or that starseeds aren't a malignant extra-galactic virus which 
will swarm all over the galaxy if not constantly watched?  Or that...
Come on Jerry, spill.  Do you have inside info?

/jlr

Are we a little bit off topic? (Who cares?)  Unless of course starseeds are
considered living space drives. ...  It seems to me that I've run across a few
living or sentient space drives, but I don't know if I'd call it SF...  Perhaps
Mr Jerry KIA knows of a few. :-)

Jim YODA::BARANSKI

    Re .64
    
    Well, starseeds *do* cross interstellar space via lightsail, so
    I guess you could consider them living stardrives.
    
    Dogs chase cars because of the challenge of trying to read the
    lettering on the spinning hubcaps.  At least that's what Snoopy
    claims.
    
    Earl Wajenberg

    re:.63
    
    Actually, that solution was thought up by Larry Todd, an under-
    ground_comics artist who some years back was trying to put together
    a comic book adaptation of RINGWORLD, and was at the time immersing
    himself in Known Space material. He said the idea just popped into
    his head, and when he broached it to Niven, Niven said something
    to the effect of, "Not a bad solution." I don't think Niven ever
    thought up an "official" answer.
    
    --- jerry

    Good.  I thought you had the *Outside* track on this one.
    
    						Don

    	In an attempt to *gently* get back on the topic of this note,
    what POWER(S) did the Puppeteers use in RINGWORLD to actually MOVE
    five whole PLANETS out of the Milky Way Galaxy?! 
    
    	Larry
    

    Perhaps economic powers.  The Outsiders have a nifty sub-light drive
    they are willing to sell for a trillion stars.  The puppeteers may
    have bought it and used it to accelerate their planets.  Or they
    might have hired all the Outsiders in the galaxy to come and push,
    but that would probably be even more expensive, even if there were
    enough Outsiders.  Also, it might be difficult (=expensive) to get
    the Outsiders to condescend to hyperdrive speeds so as to arrive
    at the puppeteer worlds before the nova wave does.
    
    But an Outsider drive seems likely, one way or another.
    
    Earl Wajenberg

I seem to remember that Puppeteers were afraid of hyperspace/hyperspeeds/
hyperdrives.  That was why they were starting their trip out of the galaxy now,
untill waiting for it to explode in a couple of million years.  I thought that
they had used the gravity tug method, the same that they used to modify their
solar system the first time.  IE put a large mass near the mass that you want to
move, and then move the larger mass.  Of course that still begs the question of
what was used to move the larger mass.  I seem to recall they used simple
reaction drives.

Jim. 

    The humans had, if I remember correctly, an inertialess drive,
    so the Puppeteers probably did, too. They likely used this to
    form the rosette and get it moving.
    
    --- jerry

    	How does one operate an INERTIALESS drive?!
    
    	Larry
    

    Very easily!
    
    But seriously, more or less, I think Jerry may have meant a
    reactionless drive -- something violating Newton's Third Law.  I
    recall such devices in the Known Space stories.  They were just
    there, without explanation.
    
    E. E. Smith had an intertialess drive.  It could operate at sub-
    or super-light speeds.  You turned it on and then ran your rockets.
    The only thing limiting your motion was the viscocity of the
    surrounding medium, which is mighty low in interstellar space. 
    Smith let them pass lightspeed.  This might be plausible if you
    manage to screw around with mass.  But if you just set mass to zero,
    special relativity requires that you go AT the speed of light, neither
    faster nor slower.  However,Special Relativity might be obsolete
    in Smith's universe.
    
    Earl Wajenberg

    Re .72:
    
    Dr. Charles Sheffeld wrote about an interesting drive which is
    physically possible if we can find the necessary building materials
    (actually, I should say the engines are not known to be physically
    impossible, but the rest of the drive is okay).  In his stories, the
    drive is often wrongly called inertialess, but it does possess the
    property that passengers do not feel any acceleration (unless they wish
    to, in which case they can adjust their local gravity).
    
    The fictional inventor of the drive insists that the proper description
    is that the drive is balanced.  A very large mass is placed in front of
    the passengers (defining front by direction of acceleration).  The
    passengers are gravitationally attracted to the mass.  By adjusting
    the distance between the mass and the passengers (moving them up and
    down in the passenger compartment which is sort of like an elevator on
    a large pole), the gravitational effect can be adjusted to compensate
    for acceleration from the engines, making large accelerations possible
    with no harmful effects on the passengers. 
    
    
    				-- edp 

    	I have come up with a concept for a near-lightspeed drive:
    
    	Physics states that if one could drop an object through a tunnel
    which extended through the entire planet Earth, its velocity would
    reach 0.99 lightspeed.
    	Disregarding the difficulty of digging a 7,926 mile-long tunnel
    through solid rock and a molten iron core, one problem which would
    be encountered is that the object could not simply fly out through
    the other end of the hole in Earth into space at nearly the velocity
    of light because Earth's gravity would have pulled it back to the
    planet's center long before it could pass far enough away from the
    core at its tremendous speed to gain enough momentum to escape Earth's
    gravity.
    
    	My solution is to *somehow* negate Earth's gravitational pull
    just AFTER the object reaches the core, so that the object could
    then continue falling at its high velocity out the other end into
    space at 0.99 lightspeed.
    
    	Since negating Earth's gravitational pull might be a bit difficult
    - not to mention causing a lot of people and other objects on Earth's
    crust ot float away - perhaps a somewhat smaller artificial planet
    could be constructed, say from many asteroids, to launch the objects
    through with controls set on the artificial planet's gravity.
    
    	What I find ironic about this theory is that instead of starships
    being launched FROM the surface of the planet into space, they are
    instead launched INTO the surface into space!
                                                 
    	Larry
    

    re reactionless drives:
    
    and don't forget Superman. Just how does the light from a yellow
    sun give him the ability to fly? Not just jump real far but really
    fly. Maybe it's a form of telekinesis.
    
    sm

    re LARRYDRIVE!:
    
    > Physics states that if one could drop an object through a tunnel
    > which extended through the entire planet Earth, its velocity would
    > reach 0.99 lightspeed. 
    
    I think you'd better check your math again. I calculate that the
    object's final velocity can be *no greater than* 7miles/sec, and in
    fact will be much less.
    
    the final velocity of an object accelerated over some distance is
    given by the formula:
    
    	v^2 = 2*a*x
    
    a = 32ft/sec^2
    x = radius of the earth = ~4000miles = 20.51e+6 ft
    
    Now this assumes a constant acceleration for the entire distance.
    Well, this is not true, at the center, the acceleration will be zero,
    and the acceleration during the fall will be a function of depth.
    
    anyway this upper limit number turns out to be mearly
    
    .0038% of the speed of light.
    
    need a bigger planet.
    
    sm

    	Okay, then we build an 88,000-mile tunnel through Jupiter (or
    an equivalent-mass artificial planet)!
    
    	Larry
    

    re: Larrydrive
    
    Actually, turning off the planet's gravitational field is less of a
    problem (side-effects-wise, I mean; sheesh!) than you suppose,
    Larry. If the ship was indeed going at lightspeed, you wouldn't
    need to turn off the field for very long (on the order of milli-
    seconds, I think, I'm too lazy to do the math).
    
    re: Superman
    
    Funny you should mention this. DC Comics (that should be a redundancy,
    but it isn't) is presently in the process of "redefining" Superman's
    origin and powers. His flight is now telekinetic in nature, and
    his invulnerability is from a psionic force fiel very close to his
    skin.
    
    --- jerry

        I recall hearing that the original Superman (the *original*
        original Superman, that is!) really did just jump long distances
        with his super-powered muscles, as opposed to actually flying
        (you know, "able to leap tall buildings in a single bound").
        It just got blown up over the years (like most any story
        which gets told over and over) until he was flying through
        time warps and intergalactic space...
        
        	/dave

    	I suppose our descendants could build a very thick and strong
    asbestos tunnel!
    	Plus a super solar gravity-null device in the Sun's core!
    
    	Larry
    

    The grand-daddy of all starship, in terms of mere bulk, was made
    up by Arthur C. Clarke for "The City and the Stars," aka "Against
    the Fall of Night."
    
    All the intelligent races of the galaxy discovered something
    indescribably nifty beyond the event horizon, reminiscent of the
    poet's line, "There's a hell of a good universe next door.  Let's
    go."  Accordingly, they all piled into a radically re-designed 
    GLOBULAR CLUSTER and shot off to better cosmoi.  Thousands of suns
    died in the instant of launch and every surviving star of the galaxy
    lost some sizable fraction of its energy.
    
    Deathstars, pooh!  Ringworlds, ha!  You need hyperdrive just to move
    around *inside* this ship.
    
    Earl Wajenberg

    	HOW, praytell, did they operate a "radically redesigned" globular
    cluster?!  I'm sure Clarke must have described it in some detail.
      
     	Larry
    
    	PS-
    	Did they use Larrydrive? :^)
    

    No, he described it in no detail whatever.  It was ancient history
    when the story began and was unearthed by the characters as a piece
    of research.
    
    The story, by the way, concerns the remote decendants of those humans
    who were too pusilanimous to leave with the rest of humanity when
    they evacuated the galaxy.  The story is placed four billion years
    in the future, when humanity has relapsed into the barbarism of...
    three billion years in the future.  So of course it still looks
    mighty fancy from where WE stand.
    
    Earl Wajenberg

There was an interesting story called the "Mother of Invention", about a ship
that landed and blew up because some diamond carbon dust got into the ship's
reactor, where it acted like a catlyst.  The crew decided that it would be
easier to design a new type of space drive, rather then try to build a
conventional space drive...

Perhaps Jerry knows/remembers more of the details...

Jim. 

        .85: The society of City and the Stars wasn't exactly barbarism
        by any means... it was just a highly static civilization.
        Nothing had changed in billions of years: even the people
        were continuously recycled.  It had been deliberately designed
        to be---and stay---*exactly* as it was... forever.  If you
        haven't read the story, do so... it's great.
        
        	/dave

    I was being ironic when I described Diaspar as barbarism.  They
    ARE supposed to be a back-sliding from the heroic days of yore,
    but are also a portrait of refinement to the Nth.
    
    Earl Wajenberg

Stanley Schmidt had a novel (whose name escapes me) about evacuating
the Earth from the galaxy.  A violent explosion was coming out from
the galactic core, and some benevolent (actually guilt-ridden) aliens
were trying to rescue any civilizations in its path.  There was no
time to build spaceships for billions of people, so the whole Earth
was moved.  Since only the top couple of miles of the crust is useful,
they used the Earth's core for reaction mass.  They fused or fissioned
all the elements in the core except iron (which will do neither), and
shot them out the South Pole. The acceleration was pretty gentle
(about 1/100 of a gee I think), because otherwise buildings would fall
down.  The oceans all flowed towards the Southern hemisphere and
flooded it.  Everybody (except those at the North Pole) felt a slight
tilt southward.  Once they left the Solar System the air froze out, so
everybody had to vacuum-proof their houses. They got up pretty close
to lightspeed and ultimately wound up in the Magellanic Clouds.

/jlr

    re:.89
    
    Funny that you brought this one up, because I was just thinking
    about it myself after mentioning the Puppeteer rosette.
    
    The novel was THE SINS OF THE FATHERS, originally serialized in
    ANALOG back in 1973-74. The novel really followed the events up
    through Earth starting its trip, if I recall. There were some
    later novelettes that took place during the journey that were
    collected into LIFEBOAT EARTH.
    
    --- jerry

    Re Larrydrive:
    
    Sorry; won't work.  Since I didn't see a ":-)" or equivalent logo,
    I assume it was entered seriously.  Assuming a homogenous body,
    the gravitational attraction falls off linearly below the surface
    until it reaches zero at the center.  (Each shell of matter has
    zero potential inside)  If you dropped a rock from the surface through
    a north_pole-south_pole tunnel (to keep consideration of so-called
    "Coriolus forces" from clouding this further), neglecting air
    resistance, the best you'd do would be to reach the surface at the
    opposite pole, according to the laws of the conservation of energy.
    
    Steve Kallis, Jr.
    

    
    Asimov used thiotimoline for a neat space drive. A good pilot could
    "trick" the stuff into dragging itself and the ship into the future.
    Now dragging the ship into the future is equivalent to dragging
    the universe into the past. So if you were travelling at relativistic
    velocities, you could balance the time effects so that the universe
    experiances the same time dialation as the ship. Thus, a trip to
    Alpha Centauri at nearly light-speed may seem to the ship to take
    only a few months, and the "endochronic" effect would make the rest
    of the universe only experiance a few months. This also had the
    effect of cancelling inertia.
    
    sm

    	No, I am serious about Larrydrive as a possible near-lightspeed
    drive - especially given human capabilities. I am also curious as
    to its feasibility, that's also why I presented it in SF Notes,
    to get technical reactions like yours.
    
    	I have also come up with a way for a starship being sent flying
    into space at near-lightspeed through my method to STOP at its
    destination.  If a Larrydriven starship is sent, say, to another
    star system that has been found to have planets (and presumably
    asteroids), when the ship is approaching the system, it could scan
    for an appropriately-massed asteroid, where it would launch highly
    sophisticated missles to "surgically" blast a tunnel through the
    asteroid, but WITHOUT negating the small planet's gravity.  The
    ship would then fly into the tunnel, where the asteroid's gravity
    would slow down the ship, which at the proper point would boost
    itself out of the tunnel onto its surface, and begin leisurely
    exploring the system.  
    	When the mission is completed, the starship crew (either himans
    or robots) would then somehow negate the asteroid's gravity and
    send the ship through the tunnel again, this time having it reach
    near-light velocity, where it could then either return to Earth
    or head on to explore another star system.
    
    	Larry
    
    

    re .93:
    
    > The ship would then fly into the tunnel, where the asteroid's gravity
    > would slow down the ship,...  
    
    Unless you come up with negative gravity I don't see how it is going
    to slow it down. Gravity will just attract the ship, adding energy
    to the ship (which may or may not manifest itself as velocity).
    Falling through such a tunnel will pop you out at exactly the same
    speed with which you entered.
    
    sm

    I kept wondering where I'd seen the idea of a tunnel through the
    center of the earth before. It was in Tick-toc-of-Oz one of my
    *early* favorites. A bunch of people slid "down" a tunnel through
    the earth and exited the other side with just enough speed to flip
    them through the air a short distance. (Of course Baum wasn't too
    great on the science side - any discrepancies he explained as "being
    magic".)

    	RE 324.95-
    
    	That is not where I got my idea from.  My tunnel is designed
    primarily as a starship accelerator, not an Earth transporter.
    
    	RE 324.94-
    
    	But wouldn't a LARGE ENOUGH planet (or star whynot), adding
    the gravity cutoff, give the starship the proper amount of speed
    to achieve near-lightspeed?  Just how large would the planet have
    to be?
    
    	Larry
    

    re .96 - let me take a shot at it.
    
    The acceleration is going to be a function of the distance from
    the center.  It will be maximal at the surface, and zero at the
    center.  I assume you're going to "turn off" gravity as you pass
    through the center and go shooting out the other side with your
    velocity-at-the-center unreduced.
    
    OK, the acceleration as a function of radius is going to be:
    
    	a(r) = (G * M(r)) / r^2
    
    I'll ignore the sign of the acceleration - it's not going to change
    during this exercise and all we really care about is the magnitude
    of the velocity, as its direction is "obvious".
    
    Note that the acceleration is depdendent only on the mass "under"
    the "falling" object - the gravitational effects of the surrounding
    mass shell sum to zero (freshman physics exercise).
    
    The mass as a function of the radius is just the density times the
    volume.  Assume constant density, so
    
    	M(r) = k1 * r^3, with k1 = 4*pi*d/3, with d the density.
    
    Thus
    
    	a(r) = k2 * r, with k2 = k1 * G
    
    This is a description of a simple harmonic oscillator - the "restoring
    force" is a linear function of position (like a spring), but we're
    only interested in one quarter of a cycle's worth of the oscillation
    - from zero velocity (one extreme) to maximum velocity (corresponding
    to the positional "zero crossing").
    
    The solution to this differential equation (which I can't figure
    out right now how to recast in terms of time - freshman physics
    was over 20 years ago, and I haven't used any of these brain cells
    since then...) is a sine or cosine (just a matter of phase).
    
    Who wants to take it the rest of the way?
    
    len.
    
    

    continuing .-1:
    
        a(r) = (G * M(r)) / r^2
    	M(r) = k1 * r^3, with k1 = 4*pi*d/3, with d the density.
    	a(r) = k2 * r, with k2 = k1 * G
        
    	substituting for k2 and k1
    
    	a(r) = G * 4/3 * pi * d * r
    
    	v^2 = 2*a*x
    
    	so let's integrate 
                R
               /
    	v^2 =  | 2*a(r)*dr
               /
              0
        
                R
               /
    	v^2 =  | 2*G*4/3*pi*d*r*dr
               /
              0

                              R
                             /
    	v^2 =  2*G*4/3*pi*d* | r*dr
                             /
                             0       
                                   |R
        v^2 =  2*G*4/3*pi*d*(r^2/2)|
                                   |0
    
        v^2 =  2*G*4/3*pi*d*(R^2/2)
        
         v^2 =  G*4/3*pi*d*R^2
    
    	 v = R * SQRT(G * 4/3 * pi * d)
    
    now just plug in the suitable density, the velocity you want to
    go, and there you are.
    
    (god, I hope this is correct!)
    
    sm
        

    Re .97, .98:
    
    I don't know how you got an equation for v^2.  The equations should
    be quite simple:
    
                                r cos wt = x,
                           -rw sin wt = x' = v, and
                         -rw^2 cos wt = x'' = v' = a.
    
    r is the radius of the Earth (or other spherical body).  x is the
    distance of the ship/object from the center of the body at various
    times, v is its velocity, and a is its acceleration.  Obviously, a = g
    when the object is at the surface of the Earth, so -rw^2 = g (g is -9.8
    m/s^2 for Earth).  w (omega) has the units 1/time, and 2pi/w is
    the period of the motion, the time it would take the object to fall
    through, stop, and come back.  The maximum speed is rw.
    
    
    				-- edp 

    re .99:
    
    Well, I may not have done the math correctly but
    
    v^2 = 2 * a * x
    
    is the equation for a body undergoing constant acceleration over
    distance x.
    
    so I figured that for an acceleration that is a function of x,
    the acceleration is constant over dx and the total will be the integral
    over the desired distance. Is that wrong?
    I like your way better. Do we get the same numeric answer?
    
    sm

    re .91
    	I have to agree with this note, and not only that but:
    
    As the object falling through the earth passed the centroid, it
    would experience a force due to gravity (as it always was 
    experiencing); however, now it is working against the object's
    velocity vector.  Thus the object will begin to slow down.
    It is just like throwing a ball in the air, it will sooner or
    later come down.  First, assume there is NO air friction, drag,
    or any other forces acting on the object.  Given this assumption,
    the object will fall to the center, pass it, and proceed to the
    other end of the tunnel reaching its orginal rest velocity at the
    rim of the hole (assuming the ball was released at the rim of
    the other side).  If there is nothing there to catch it, then
    the the object will fall back to the center.  The end results
    are a pendulum.  Now, figure in effects due to forces such as
    drag, the ball will never reach the other end unless some initial
    velocity was given to the object which would eventually propel
    it to the other end.  However, at any rate, if the object was
    just allowed to do its thing, then a pendulum would again be 
    created.  This time though, the "swing" of the object from one
    end to the other would decay due to the damping effect of the
    forces we often assume neglible.  The steady-state of the object
    would be at rest at the centroid of this planet.  The long term
    steady-state would be a burned up object.
    
    

    Yes, but the Larrydrive depends on the magical ability to turn off
    the gravity after reaching the center.
    
    ESW

        Another Larrydrive concideration: you need a planet with
        a well defined and stable pole of rotation (or a non rotating
        object, which would be harder to find).
        
        You'd lose about 30km of radius by making your Earth tunnel
        through the poles... but at the equator you'd need something
        like a 20km wide tunnel to avoid running into the sides during
        your voyage through the planet (based on rough calculations).
        
        Although I'd say that the gravity neutrilizer should be enough
        to keep us busy for quite a while without worrying about how to
        excavate a tunnel 20km wide (or even 20m wide!) and nearly
        13000km long...
        
        Another "minor" point which may blow away the Larrydrive... we
        can already make an acceleration of several g's.  In fact,
        enough g's that we have trouble protecting the humans from its
        effects.  The planetary acceleration of 1g (much less for a
        smaller planetoid) just isn't a significant addition. The only
        real advantage of the Larrydrive is in fuel consumption,
        since that 1g is "free".
        
        However, unfortunately, it's really *not* free.  What sort of
        energy does it take to run this gravity neutrilizer? Well, we
        don't know, but we can reasonably assume that it'll probably be
        quite a bit, assuming the gadget ever proves possible at all.
        That's not even considering the substantial engineering costs
        associated with such a tunnel... particularly on something large
        enough that the "free" acceleration becomes significant: like
        Jupiter; or the sun, where the 1.3 million km long tunnel itself
        is the *least* of your problems!
        
        	/dave 

    Re .100:
    
    Oh, I see.  v^2 = 2ax is an unusual equation, and I didn't know
    whether the variables were constants, functions of time, or what.
    
    I checked your answer, and it is the same as mine when the appropriate
    values are put in.  An object reaches 7,883 meters per second at
    the center of the Earth, which is about 1/38,000 the speed of light.
    
    
    				-- edp

        Although it doesn't really make much difference, I believe
        the tunnel width I gave in .103 was something over an order
        of magnitude too small... in any case, knowing the constants
        involved, you could always excavate a much narrower curved
        tunnel to follow the actual course through the rotating planet.
        
        	/dave

    	As I said earlier, instead of using Earth or any other "natural"
    planet, let's construct an "artificial" planet composed of numerous
    combined asteroids - or would even building an artificial planet
    out of materials from Earth, the Moon, and the asteroids (instead
    of just melding planetoids).  Then we could shape the planet to
    our specifications, stop any rotation, and have a tunnel and
    gravity-null device already built in.
    
    	Also, how about my ideas on stopping a Larrydrive starship?
    (Note 324.96 I believe).
    
    	Larry
    

    re .106:
    
    now that your considering building your own planet, the larrydrive
    is beginning to resemble much more somebody else's "drive" (maybe
    Forward?)
    The idea is to build an exceedingly massive "smoke ring" in space
    somewhere. I say smoke ring, because you have to "spin" it the same
    way that a smoke ring does, i.e. through (as opposed to "around")
    the center. To illustrate what I mean, imagine a cross section through
    a torus, so you see two circles: o==o, the left circle rotates
    clockwise, the right circle counter-clockwise. Now if the ring is
    made of something like neutronium, you get wicked gravitational
    effects. Shoot your space-ship through the hole and it gets accelerated
    wicked fast (or decelerated, depending on which side of the ring
    you enter.) This way you don't need to invent a gravity canceller,
    but you do need some way to keep the passengers from being flattened
    by the acceleration.
    
    sm
    
                        
                  
    
    

    If the acceleration is effected by gravitational forces, you don't
    have to worry at all about flattening the passengers.  They will
    be accelerated along with the ship and perceive no relative motion
    at all.  Unless there are tidal effects, which is quite likely.
    But that's a different problem.
    
    Earl Wajenberg

I have moved this discussion to the note on spacedrives because I really don't 
feel it belongs in the SF-myth category.  Most of the people who use FTL 
travel know that they are doing something irregular according to normal 
physics.  That's why they frequently invoke undiscovered entities like 
hyperspace and subspace.  They aren't making careless blunders.

Re 362.203

Yes, the causality argument would work just as well -- or just as poorly -- in
general relativity as in special.  I just went to the MK library and looked up 
the postulates of special relativity.  They are:

1: The analytical forms of physical laws are the same in all inertial frames.

2: The speed of light is the same in all inertial frames.

However, the basic laws of physics are unaltered by time-reversal.  (They 
mentioned this in the encyclopedia article.)  This is true of all known
physical phenomena except the decay rates of certain K-mesons, and the CTP
theorem takes care of them by adding the parity and terrene-sign reversals. 

Moving backward through time automatically reverses terrene sign, as Feynman 
found out.  If it or FTL speed reverses parity as well, there isn't much to 
complain about.

If you want to attack FTL travel on theoretical grounds, I would recommend 
concnetrating your attention on the imaginary values that turn up over light 
speed.  Those have no ready physical interpretation.


Re 362.204

If the results are not in fact random, then that is still significant, since 
according to QM it is SUPPOSED to be random.

I double-checked on "spacelike" and "timelike."  Timelike is the one that 
allows normal causal connection.

I must have lost something along the way...

Why do some people think going from point A to Point B and back quickly entails
time travel, despite A & B being a long distance apart?

I hazily understand that you can't *observe* something moving FTL, but who
cares?  If I want to look at the view, I'll stop...

Jim.

    re .109:
    
    I still don't understand how the CTP time reversal experiment bears
    on the discussion at hand, i.e. that the laws of physics must look
    the same to all observers. If the entire universe were time reversed
    then all observers would still agree on their observations.
    
    > If you want to attack FTL travel on theoretical grounds, I would 
    > recommend concnetrating your attention on the imaginary values 
    > that turn up over light speed.  Those have no ready physical 
    > interpretation.
                      
    1) The fact that they have no ready physical interpretation is exactly
    	why I am avoiding using them as an argument.
    2) I believe that the physical interpretation of those imaginaries
    	is exactly this "causal confusion" that crops up with FTL. (but
    	since I can not prove that, I've tried to avoid bringing it
    	up.)
                                                              
    Re 110:
    
    Exactly the question I've been asking for a long time. I think it
    is confusion concerning the interpretation of the experiment which
    is the basis of this discussion.
            
                                                   
                  /
                 (  ___
                  ) ///
                 /
    

    Re .110 & .111
    
    The relation of FTL to time-travel comes about because of the
    relativity of simultaneity.
    
    Take three observers, A, B, and C.  We'll take B to be "at rest."
    A moves past B heading east, C moves past B heading west.  As they
    all move past each other, two events happen to the east, one near,
    one far.
    
    B sees these events happening at the same time.
    A will see the far event happen first, then the near event.
    C will see the near event happen first, then the far event.
    
    All of this is what happens with special relativity and slower-than-
    light speeds, and it is strange enough.  But notice that the two
    events were not at the same place.  Suppose the two events happen
    at B, e.g. B claps its hands twice.  Then A, B, and C will all agree
    which clap happened first.
    
    BUT, if you allow an observer D moving faster than light in the
    proper direction and proper speed, D will observe B running backwards
    like a movie threaded wrong end first through the projector.  D
    will not agree with A, B, and C about which handclap was first.
    That is how FTL gets mixed up with time travel.  Not ever FTL trip
    would result in time-travel but allowing for the one possibility
    forces one to allow the other if you stick to the rules of special
    relativity.
    
    By the way, whenever I say that some observer sees something happen
    at time T, I am allowing for the observer to subtract the time the
    light signal takes to get to him.  The times are the times the observer
    really calculates the event takes place, not just the time the observer
    gets word of the even.
    
    Re .111
    
    One more try:  I didn't mean to imply reversing the whole universe.
    It's just that, if we have an FTL object that sees the universe
    as time revered, then presumably IT looks time-reversed to the
    universe.  The CTP theorem means that time-reversed objects are
    physically possible, so neither FTL pilot nor cosmos sees something
    that breaks natural law.
    
    Seeing something with an imaginary mass might very well be considered
    as breaking a natural law (though I haven't stopped to think it
    through).  And a body moving FTL must either have an imaginary mass
    in its own rest-frame or have an imaginary mass in any subluminal
    frame.  A friend of mind proposed that it should have an imaginary
    mass in its own frame and, since any other FTL bodies it meets are
    also imaginary, there is no observable effect of being imaginary.
    I'm not sure that works either.
    
    Earl Wajenberg

             <<< LDP::SYS$SYSDEVICE:[NOTES$LIBRARY]SPACE.NOTE;1 >>>
             -< General Space and Space Shuttle Discussions/News >-
================================================================================
Note 212.57                       STAR PROBE                            57 of 57
EDEN::KLAES "Mostly harmless."                       43 lines   6-OCT-1986 17:41
                      -< SOME STARSHIP PLANS FROM USENET >-
--------------------------------------------------------------------------------

Newsgroups: net.space
Path: decwrl!ucbvax!slb-test.CSNET!DIETZ
Subject: Bootstrap Starships
Posted: 2 Oct 86 21:22:00 GMT
Organization: The ARPA Internet
 
Here are a couple of ideas for engines for interstellar travel. Both
are based on the idea of generating energy by interacting with ambient
matter, and using that energy to eject reaction mass, much like the
tether/engine combination mentioned previously. 
 
In the first design, a collector is used to generate energy from
passing interstellar gas.  I assume the vehicle is travelling at a
good clip (.1 c, say) before this engine is turned on.  The generator
is a thin foil a few atoms thick.  On either side of the foil I place
a sparse grid negatively charged with respect to the foil.
Interstellar hydrogen atoms will hit the foil and be ionized. Their
nuclei will pass unhindered through the trailing grid. The electrons,
which are much less energetic, will oscillate between the grids,
losing energy in the foil, eventually stopping there.  Electrons can
be drawn off the foil to do useful work, like driving an ion engine. 
The electrons are eventually ejected out the back to neutralize the
gas atom nuclei. 
 
Some problems: the foil will lose mass by sputtering, and the vehicle
will have to travel light years to get significant acceleration
because the interstellar gas is thin.  However, the idea does seem
more feasible than ramjets of various kinds. 
 
By turning off the ion engine and the electron gun we can let the
generator become very negatively charged.  Gas nuclei will be
accelerated up to the vehicle's speed.  The generator acts as a
parachute. 
 
 
A second design is for ultrarelativistic flight.  It interacts with
the cosmic background radiation.  At high speeds the spacecraft
perceives a temperature gradient: the radiation is hotter in front
than behind.  This gradient can be used to drive a heat engine, and
the energy used to expel reaction mass.  The low density of the CBR
means this engine is best used for long trips at very high speeds (for
intergalactic travel). 

Newsgroups: net.space
Path: decwrl!nsc!voder!aitnet!evp
Subject: Re: Bootstrap Starships
Posted: 8 Oct 86 06:52:20 GMT
Organization: American Information Technology, Cupertino, CA
 
 
$ 
$ Here are a couple of ideas for engines for interstellar travel.
$ 
$ In the first design, a collector is used to generate energy from
$ passing interstellar gas....
$ Interstellar hydrogen atoms will hit the foil and be ionized.
$ Their nuclei will pass unhindered through the trailing grid.
$ The electrons, which are much less energetic, will oscillate
$ between the grids, losing energy in the foil, eventually stopping
$ there.  Electrons can be drawn off the foil to do useful work...
$ 
$ A second design is for ultrarelativistic flight.  It interacts with
$ the cosmic background radiation.  At high speeds the spacecraft
$ perceives a temperature gradient: the radiation is hotter in front
$ than behind.  This gradient can be used to drive a heat engine...
 
TANSTAFFL. Both schemes ignore the momentum of the particles you are
extracting energy from.  Both electrons and photons deposit their
momentum in the spacecraft they strike the collection surface.  The
energy extracted is really coming from the spacecraft velocity as it
slows downdue to "equal and opposite" reaction to the impinging
particles.
-- 
Ed Post   {hplabs,voder,pyramid}!lewey!evp
American Information Technology
10201 Torre Ave. Cupertino CA 95014
(408)252-8713

    The second drive (a velocity difference causing a temperature
    difference in the cosmic background) would also violate the second
    law of thermodynamics.  It extracts energy from a system at a constant
    temperature.
    
    On the other hand, didn't they find a slight anisotropy in the cosmic
    background?  This works out to mean that the solar system has a
    velocity relative to the center of mass of the universe.  You could
    theoretically extract energy from that by slowing the whole solar
    system down.  It's kind of tough to build a heat engine that operates
    off of millionth of a degree differences at 4 degrees Kelvin, but
    that's merely engineering.
    
    /jlr

Newsgroups: net.space
Path: decwrl!decvax!ucbvax!DFVLROP1.BITNET!ESG7
Subject: Re: Bootstrap Starships
Posted: 13 Oct 86 17:40:19 GMT
Organization: The ARPA Internet
Posted: Mon Oct 13 13:40:19 1986
 
In Vol. 7, No. 9 of Space Digest, Paul Dietz proposed some "Bootstrap
Starship" ideas.  I am very reluctant to criticize this sort of
article because this is **exactly** the sort of thing I like to see in
Space Digest.  I compliment Paul for using his head.  However I don't
think his idea will work.  My embarassing question about his design is
"where does the energy come from?".  Paul's obvious answer would be
that it is coming from the surrounding interstellar medium.

I shall focus on his second design since it's easiest to criticize. 
You have a vehicle going at about 10 psol (percent speed of light). 
The front is interacting with the interstellar medium (hydrogen at
about 0.1 particles per cubic centimeter).  The front will heat up. 
In Project Daedalus it was assumned that the front of the vehicle
would have a temperature of around 200 deg. Kelvin.  We could assume
that the rear would be at almost 0 deg. Kelvin.  In theory the Carnot
efficiency would be near perfect.  However all of your energy would
actually be coming from original kinetic energy lost due to drag.  We
can calculate power by assuming a disc of 55 meters radius travelling
at 10 psol (relativistic effects are insignificant), and assume an
interstellar medium as originally described.  From the vehicle's frame
it sees particles streaming in at 10 psol.  The mass of intersellar
medium impacted on the forward shield of the vehicle for one second
would be 1.118e-8 grams.  From this we may estimate the energy
available in one second based on KE=(1/2)*M*(V**2).  This calculates
to be 5.355 kilowatts. This would be very useful for powering such on
board systems as a navigation computer.  However it is insignificant
in terms of the vehicle's total kinetic energy.  This is extremely
**fortunate** by the way, for if drag was significant then
intersteller travel would indeed be impossible.  A side point is
**if** the 1.118e-8 grams/sec. could be converted entirely into energy
by some magic way then you would have approximately  one megawatt of
power, or 1350 horse power, which is remarkably little.  You might use
this to push out a reaction mass but then you have the embarassing
question of where do you get the reaction mass from?  It was a good
attempt Paul, but you'll have to try again. 
 
                       Gary Allen



Newsgroups: net.space
Path: decwrl!decvax!ucbvax!LLL-MFE.ARPA!ATTENBERGER%ORN.MFENET
Subject: fusion engines
Posted: 14 Oct 86 15:49:00 GMT
Organization: The ARPA Internet
 
Posted: Tue Oct 14 11:49:00 1986
  
Paul Koloc writes:
   What we need is to develop the technology of fusion to do really
   significant things beyond LEO.  DoE has demonstrated it can't make a
   workable commercial fusion power generator...
   ... prototype fusion engines could be operating just after
   three years.  These engines if based on PLASMAK(TM) technology, would
   burn hydrogen(protium) boron (eleven) which generates pure helium(four)
   and no radiation.

Actually DOE has done a responsible job of allocating scarce funds. 
The main problem is that congress lost interest in fusion when the the
oil glut began.  Also it is a long way from a prototype fusion engine
(just a hydrogen-boron pellet being hit by a laser) to an engine which
can actually lift a payload.  We need better lasers and a good way to
keep the containment vessel from eroding.  I would prefer to see all
of our pennies for space research being spent on shorter term
missions, with fusion engines developing as best they can via military
funding for laser research. 

Newsgroups: net.space
Path: decwrl!ucbvax!DFVLROP1.BITNET!ESG7
Subject: Nuclear Fusion Pulse Propulsion Systems -- available literature
Posted: 17 Oct 86 13:26:45 GMT
Organization: The ARPA Internet
 
    Someone asked about source material on Nuclear Fusion Pulse rockets
for interstellar travel.  The best source is the Project Daedalus
final report produced by the British Interplanetary society.  To
acquire a copy write: 
 
 
               The British Interplanetary Society 
               27/29 South Lambeth Road
               London SW8 1SZ
               England
  
 
    Also the Journal of the British Interplanetarey Society (JBIS),
Interstellar Studies (red cover series) often describes this style of
propulsion along with Bussard ram scoop and antimatter propulsion
schemes.  The JBIS is hands down, the best source of information about
the engineering on interstellar travel. 

    There is also a paper floating around entitled: "A Laser Fusion Rocket
for Interplanetary Propulsion" by Roderick A. Hyde, 27 Set. 1983 from
Lawrence Livermore National Laboratory (Larry Labs), reprint number
UCRL-88857.  Roderick Hyde is a nuclear weapons designer who designs
starships when he isn't designing a bigger and better thermonuclear
warhead.  Supposably, most of his major innovations on starship design
are classified (Q-Clearance).
    Also "Astronautica ACTA" will on occasion produce something on
interstellar travel.  The most exciting stuff with respect to
interstellar travel is being done by Sandia National Labs.  Sandia is
working on an inertial confinement scheme based on high energy neutral
particle beams rather than lasers.  This sort of system could easily
be adapted into a one million sec. specific impulse propulsion system.
    Word has it that the Nova, Novette inertial confinement scheme at
Larry Labs is a loser and only good for bomb work.  It'll never be
useful for producing electrical power or propelling a spacecraft. 
 
                                   Gary Allen

    I not sure I understand this stuff:
    
    	1/ Why is the speed of light a limiting factor.
    	   I dont mean the theory part I mean why should
    	   nature impose a speed limit?
    	2/ Why should we not travel faster than light or
    	   at the speed of light?
    
    I know this note is about to get shot down in flames, all
    I ask is stop and question current theories.  At the moment
    someone has stated that nothing can travel at the speed of
    light.  Why not challange this idea.
    
    Chris
    
    

re: Note 324.118 by OPG::CHRIS 
>    	1/ Why is the speed of light a limiting factor.
>    	   I dont mean the theory part I mean why should
>    	   nature impose a speed limit?

>    	2/ Why should we not travel faster than light or
>    	   at the speed of light?

>    Why not challange this idea.

Why should nature do or be anything?  Was it Einstein who also said
the the most incomprehensible thing about the universe is that it 
is comprehensible?
The basis of the c-limit is the observation that the observed speed 
of light is constant regardless of the speed of the observer (in an inertial
frame of reference).
That leads to the Lorenz contraction, mass amplification, and the like.
The wall is mass amplification, that is, mass increases as speed increases
and would reach infinity at c.
One proposed hole in the theory is that quantum tunnelling may be able
to skip the c boundary, going from just under to just over c without
going through it, avoiding the singularity.
So we can hope....

- tom]

    Re .118
    
    "Why should nature impose a speed limit?" is a rather metaphysical
    question, as Mr. Powers suggested in .119.  Without getting technical,
    or trying to offer a definitive answer where NOBODY has one, I'll just
    mention this:  The speed limit can be regarded as a side effect of the
    way space and time fit together to make a larger, more comprehensive
    whole.
    
    Vague enough?
    
    Earl Wajenberg

    A simple way to look at it is that a body's mass increases as its speed
    increases (this has been verified).  The more mass a body has, the
    harder it is to accelerate.  At the speed of light, a body's mass
    becomes infinite.  Therefore the closer to the speed of light you
    get, the harder it is to accelerate.  That's why the limit is there...
    
                        Roak
    
    I know this isn't complete, but just one facet of the restriction... 

    Also, these effects are not just theoretical predictions; they're seen
    all the time on subatomic particles.  It's not hard to make an 
    electron go 99% of the speed of light, but no one yet has made one
    go 101% of C (in vacuum).  I don't know if people have seen 
    the mass increase on
    macroscopic objects, but they have observed the time dilation effect,
    which is another consequence of the same principle.
    
    Actually, I don't know why people complain about the light barrier.
    You CAN travel at more than speed of light in your reference frame;
    you just can't do it in the home frame.  At .99c you go about seven
    light-years in one year of ship time.  In fact, it takes less energy
    to go this fast than it would if Newton's ordinary laws applied.
    In Newtonian mechanics, the kinetic energy is �mv�.  In Einsteinian
    mechanics, kinetic energy is expressed as extra mass above the rest
    mass.  If the time dilation factor is D 
    (where D = (1 - v�/c�)�), then the ship has D times
    more mass than it would at rest, and the apparent velocity is v * D.
    For v close to c, v * D ~= c * D
    So,
    
    Newtonian KE =  �mv�         = � * m * D� * c�
    ------------                  ----------------  = � * D� / (D - 1)
    Einsteinian KE = (Dm - m)c�  = m * (D - 1) * c�

    If D = 7, as above, then it would take about 3 times as much energy
    in a Newtonian universe to go 7c than it would in an Einsteinian 
    universe.  If you want to jaunt over to Andromeda at, say, 1,000,000c,
    then Einstein saves you a factor of 500,000 in energy.  Several Ice
    Ages will have passed by the time you get home, but that's the 
    perils of travel.
    
    /jlr

    How about this... (I know I'll get shot down in flames, but this
    is fun!  (yes, even the flames...))
    
    I have a ship that carries X ammount of fuel.  As I approach the
    speed of light my mass increases and my volume decreases approaching
    infinity and zero, respectivly.
    
    Now, I am *so* close to the speed of light that my mass is effectivly
    infinite.  Theory has it that in order to accelerate to c I would
    need an infinite ammount of energy to accelerate my infinite mass.
    
    Now, inside my infinitly massive ship I still have 'Y' fuel left
    over.  Let's say that this represents 10% of the mass of the ship.
     The mass of the ship is infinite, therefore the mass of the remaining
    fuel is also infinite (10% X infinity = infinity).  Seems to me
    that I should be able to get a lot of energy out of an infinite
    ammount of fuel.  Say, about an infinite ammount of energy, that
    should just about do it.
    
    Now, where'd I slip up?  Seems to sound good.
    jim
    

    Nope, nope.  The problem is that you are ALMOST infinite (is that
    like Mostly Dead?).  And the ALMOST infinity of your fuel is
    sufficiently smaller than the ALMOST infinity of the mass of the
    ship that you'll never break even.
    
    The highest possible speed in the universe can be achieved if you
    convert the mass of the universe into energy (except for one electron
    that you keep in your back pocket) and then apply that energy to
    accellerate that electron.  Someone did some number crunching on
    this once, and it turned out to be VERY VERY VERY close to C, but
    of course, below it.
    
    				=ELB=

    re:123
    
    Also, I'd add that you don't have an infinite amount of fuel, you
    have a set amount of fuel that weighs (almost) an infinite amount.

    				=ELB=

    re: .125
    
    But energy is a function of MASS, not volume.  So if I have a can
    of fuel that represents a set ammount of fuel that has infinite
    mass I can obtain an infinite ammount of energy.  Although I agree
    with .124, for the moment...
    
    jim
    

    The question that has bugged me for a long while (maybe someone
    here can explain it) is not why there is a speed limit -- I can
    comprehend that (infinities give me problems anyway), but why is
    it the value it is...  Why ~300K km/s and not a few orders of
    magnitude higher or lower?  A few orders of magnitude higher and
    intersteller (if not intergalactic) travel becomes attainable for
    realistic lifespans - a few lower and its not even worth
    discussing.

    Is there some characteristic of space-time (e.g. the vacuum energy
    level) that could be modified to change the limit?  We know that
    light travels *slower* through a medium (although masses can still
    travel faster, hence Cherenkov radiation...), is there a way to
    *increase* the limit and still maintain the Einstein-Lorentz
    transformations relative to that limit?

	Mike

    The value of c is a fundamental natural constant.  Meaning that it is
    not known to depend on any other physical properties.  Why c, or h, or
    G or any other constants, have the particular values they do is one of
    the deep and unanswered questions of physics.
    
    On the flip side, people have calculated from time to time that, if the
    fundamental constants deviated only slightly from the values they have,
    the universe would not be habitable.  So, the fact that we are here
    talking about it is proof that the constants fall in that narrow band. 
    What forces placed them in that narrow band are unknown.
    
    Earl Wajenberg

    And no, there is no known medium in which the speed of light is faster
    than it is in a vaccuum.  I suspect it would be a very interesting
    medium, and would probably have a negative or imaginary energy density. 
    
    Earl Wajenberg

	Take heart .118 - look back on the history of science and see how
	many laws have turned out to be false or at least incomplete. If
	we can imagine it we might just be able to do it. Warp speed c,
	Scotty. liesl

    There are a couple of problems with using your nearly infinite mass
    of fuel to accellerate your ship:
    
    1)	The mass of the fuel is very large because it's travelling in
    the forward direction at a very large velocity.  When you push it
    out the back, it's forward velocity drops, as does its mass-equivalent.
    
    2)	The time dilation effect is going to get you too.  If you push
    fuel out the back at what is to you a very large velocity, the rest
    of the universe (since it sees you moving very slowly) will see
    the velocity of the fuel as being lower than you think it is.
    
    I suspect that getting to light-speed from this side of the barrier
    is impossible, and I have my doubts about being able to tunnel thru
    the barrier or get there without getting too near it.  I know,
    converting everything to tachyons will do it, but that's kind of
    like "locally reducing the value of Planks' constant.  Sure it will
    have many wondrous and varied effects, but how do you do it?
    
    Willie

    re:.127
    
    Why does c=~300K km/s? Why not higher or lower?
    
    That's the same as asking why pi=3.1415962... rather than 3 or
    3.5. It just *is* what it is.
    
    --- jerry

    Looks like someone has the right idea -- we're now discussing
    relativity.  Over to note 605 we go....
    
                                 Roak

	Could someone point me to a/the note in SF that discusses 
Impulse Drive (if there is a note), ie. from Star Trek?

If there is no note, could someone take a stab at explaining it 
to me?

-Mike

    Re .134
    
    Well, there is a whole Star Trek notefile which might discuss it.  Last
    I heard, which was some time ago, it was at THEBAY::STAR_TREK.
    
    All I was ever able to gather about impulse drive was that it was their
    sub-light drive and located in the saucer section, whereas the warp
    drive was located in the two long pods.  (I always wondered what would
    happen if only one pod blew out.  Would the ship reduce to half speed? 
    Spin around in a tight circle at hundreds of times the speed of light?
    Rip itself to flinders?  Or would they just pause for a commercial?)
    
    I always figured it was a gravity drive, but I have no proof of this.
    
    Earl Wajenberg

    	Impulse Drive (in the STAR TREK Universe) is "simply" a very
    sophisticated fusion engine, capable of only sublight speeds up
    to 99 percent of the speed of light.  Only Warp Drive can go at
    FTL velocities.  Impulse Drive is great for manuevering through
    planetary systems.
    
    	And to give a very brief explanation of fusion power, it is
    energy derived from the forcing *together* of atoms, as opposed
    to fission power, which is the energy derived from the *splitting*
    of atoms.  Fusion power is generally "cleaner" (less radiation)
    than fission, but with our present real technology, is difficult
    to build and use.  Hydrogen bombs have so far been our most 
    successful (in relative terms) fusion device yet built.
            
    	Larry
    

	
re -2.  I already scanned the entire Star Trek Notefile... not 
there

re -1.  Thank you for answering me Larry...


BUT!  

In the Star Trek: TNG magazine, they state that the Impulse Drive 
is an Inertialess Drive.  Also, Why the 'Impulse' in the name?  
And lastly, the Warp Engines do not propel the vessel, from what 
I have derived from all of my ST resources, The Impulse Drive is 
the SOLE source of thrust.  The Warp Engines merely create a warp 
envelope.

If I'm wrong, slap me and tell me so, but I have this insatiable 
curiousity about the workings of the Impulse Drive...


-Mike



PS- In fact, in the magazine, they refer to it as the 'Tandem 
	Impulse' deck...

PPS_  Thanks Larry!  I know what Fusion energy is!!!  ;^)
	
    

    The Star Trek Novel "The Final Frontier" has a very believable 
    explanition of the impluse drive.  I recommend the novel highly
    
    Tony

	One other little thing (I hope this is appropriate!  The 
people in Star Trek Referred me to SF), on all of the federation 
starships I have seen, the Impulse engine exhaust vents are 
facing astern.  How do they reverse engines short of swinging 
about 180 degrees?   You can't reverse a fusion reaction ( that 
is to say, in a manner that would result in negative thrust).  I 
would have to go with repl -3, that it must be some type of 
gravity drive...


Mike	
    

	Thanks Tony, I'll pick it up tonight...

Mike

    Re .137 (Mike):
    
>In the Star Trek: TNG magazine, they state that the Impulse Drive 
>is an Inertialess Drive. ...
 
    BUT!
    
    As amply demostrated by Doc Smith, an inertialess drive would allow
    you to go faster than light.  In fact, the limiting speed factor
    was thrust versus the equivalent of friction.
    
    "Inertialess" sounds trendy, though, to people who don't understand
    its implications ...
    
    Steve Kallis, Jr.       

< Note 324.141 by MARKER::KALLIS "loose ships slip slips." >
                           -< "inertialess" indeed! >-

    
>    As amply demostrated by Doc Smith, an inertialess drive would allow
>    you to go faster than light.  In fact, the limiting speed factor
>    was thrust versus the equivalent of friction.



I have been given the explanation of how the Impulse engines 
work.  I'm paraphrasing a paraphrase but "The impulse engines act 
on the fabric of space in such a way that they produce a ripple 
or wave that carries the starship along with it, like a 
surfboard is carried by an ocean wave..."  that's not exactly how 
it was told to me, but close enough.  
    
this (of course) raises another question in my mind.  Obviously, 
it's some sort of 'gravity drive', or nearly equivalent to one.  
So, it can't really be inertialess, BUT, it COULD carry the 
vessel, and it's contents along with it in sucha way that it 
feels inertia free, by effecting the immediate space around the 
ship, as well as inside it.  Right?  Maybe??

>    "Inertialess" sounds trendy, though, to people who don't understand
>    its implications ...

They should be more careful about what they write in these 
publications...


-Mike

    Re .142
    
    I agree.  It's very plausible that, if you grant a gravity drive, it is
    a small step to imagining that it can cancel inertial effects in the
    ship's cabins.  In fact, it had better, given the massive accelerations
    Star Trek ships go through as they hop into and out of different levels
    of warp and perform tricky maneuvers.  I was always bemused when Kirk
    and Scotty would crank the old ship up to warp 7 or 8 and everybody
    would lean back in their chairs as if accelerating from 0 to 60 mph in
    ten seconds.  Were the inertial dampers leaking or something?
    
    Earl Wajenberg

    Yah, but the problem with Doc Smith's Bergenholm (inertial mass
    canceler) was that it could never decide whether it was canceling
    just "inertial" mass, or "gravitational" mass as well :-)
    				- HBM

	
	Maybe they could find tune it, to give them that 
'accelerating' effect!  :^)

Mike

    Re .144 (HBM):
    
    > ..............it could never decide whether it was canceling
    >just "inertial" mass, or "gravitational" mass as well :-)
     
    Even with the smileyface, "huh?"  Where did it say in the Lensman
    stories something implying gravitation?  In _Galactic Patrol_, it
    was clear (going to the Overlords) that gravitaional mass was
    unaffected; in _Gray L:ensman_ Medon went "free" without loss of
    gravity, etc. ...
    
    Are you confusing this with the shield in _Skylark III_ where gravity
    was cut off?
    
    Steve Kallis, Jr.

    This week's issue of Science News has a one-column article on a new
    wrinkle from theoretical physics.  (May 12, 1990, issue, No. 19, 
    Vol. 137.)  The report is on two articles appearing in the Feb.22 and 
    Mar.22 Physics Letters B, by Klaus Scharnhorst of Humboldt-Universit�t 
    zu Berlin in East Germany and Gabriel Barton of the University of
    Brighton, England.

    It seems that, if you take the energy density of pure, plain vacuum to 
    be zero, then the energy density between a pair of parallel conducting 
    plates is very slightly negative.  And it also appears that light moving 
    perpendicular to the plates, through this zone of negative energy, moves 
    faster.
    
    That is, the speed of light between these plates is higher, in one
    direction.
    
    True, the predicted change of velocity is only one part in 10 to the 36th 
    for plates one micron apart, much too small to measure, so this is pure 
    theory so far.  But I know what to do with the theory, and so do most 
    of you....

    The next questions are: Does this effect occur with all kinds of negative
    energy density? Is there a limit to how dense the negative energy can get?
    How does the speed of light vary with the density? and Will there be a
    frequent-flier plan?

    Earl Wajenberg
    
    P.S. See .129 for a lucky guess on my part.

        The May 1992 issue of ANALOG SCIENCE FICTION AND FACT magazine
    has a somewhat technical article by Robert M. Zubrin on magnetic 
    sail spacecraft.  The article discusses the concept of vehicles 
    which use celestial magnetic fields to move in space.

        Larry

    That was an interesting article.  Basically, you form a
    superconducting cable into a ring, run current through it to get
    a magnetic field, and catch the charged particles of the solar wind.
    For a five-ton cable (200 km long) carrying 50,000 A you could get 
    accelerations of about a cm/sec/sec.  Not much, but it doesn't
    cost you much either and it builds up over time.  The cable is a lot 
    easier to deploy than a photon sail.  The author was from
    Martin-Marietta and was proposing it as a way to get cargo to Mars.
    /jlr

        "We have for the first time imagined a way to use the huge
    stockpiles of our bombs for better purpose than for murdering people. 
    My purpose, and my belief, is that the bombs which killed and maimed
    at Hiroshima and Nagasaki shall one day open the skies to man...."

             - Freeman Dyson, MANKIND IN THE UNIVERSE, 1970

Article: 79370
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space
Subject: Propulsion FAQ (was Re: Journey to A-Centauri) (long)
Date: 9 Dec 93 11:00:35 -0600
Organization: Fermi National Accelerator Laboratory
 
In article <[email protected]>, <[email protected]> writes:

> Suppose funding is not a problem.  Based on our existing knowledge/technology,
> is there anyway for earthlings to set foot on A-Centauri or any other systems?
> Clearly, our existing vechicle couldn't handle interstellar travels.
> 
> Can anyone recommend me some books/info on this subject?
> 
> Thanks.
> 
> Ken Tai.
 
[Oh, boy.  I get to use my recently developed "boilerplate FAQ answer."]
 
The Frequently Asked Questions (FAQ) list for the Usenet newsgroup
sci.space has information relevant to your question.  It is posted
every month to sci.space with a long expiration time, so you can
probably find it on your system.  If not, there are other ways to
obtain it.
 
The FAQ postings are available by anonymous FTP from the Ames SPACE
archive in ames.arc.nasa.gov:pub/SPACE/FAQ/faq*, along with more
information expanding on topics in the FAQ.
 
I append some useful sections, but you might like to read the entire
FAQ list.
 
     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     [email protected]
   -   -       Internet:  [email protected]
     ~         SPAN/Hepnet:      43011::HIGGINS 
 
===================
[At this point I append a chunk of the FAQ that seems to be helpful to Ken.]
 
From: [email protected] (Jon Leech)
Newsgroups: sci.astro,sci.space,sci.answers,news.answers
Subject: Space FAQ 05/13 - References
Supersedes: <[email protected]>
Followup-To: poster
Date: 1 Dec 1993 23:15:29 -0500
Organization: University of North Carolina, Chapel Hill
Lines: 700
Approved: [email protected]
Distribution: world
Expires: 6 Jan 1994 04:15:26 GMT
Message-ID: <[email protected]>
References: <[email protected]>
NNTP-Posting-Host: watt.cs.unc.edu
Keywords: Frequently Asked Questions
Xref: fnnews.fnal.gov sci.astro:33646 sci.space:44709 sci.answers:689
      news.answers:15536 
 
[...the following is only an excerpt from tfile , which is itself part 5 of
the 13-part FAQ compiled by Jonathan Leech.]
 
    ESOTERIC PROPULSION SCHEMES (SOLAR SAILS, LASERS, FUSION...)
 
    This needs more and more up-to-date references, but it's a start.
 
    ANTIMATTER:
 
	"Antiproton Annihilation Propulsion", Robert Forward
	    AFRPL TR-85-034 from the Air Force Rocket Propulsion Laboratory
	    (AFRPL/XRX, Stop 24, Edwards Air Force Base, CA 93523-5000).
	    NTIS AD-A160 734/0	   PC A10/MF A01
	    PC => Paper copy, A10 => $US57.90 -- or maybe Price Code?
	    MF => MicroFiche, A01 => $US13.90
 
	    Technical study on making, holding, and using antimatter for
	    near-term (30-50 years) propulsion systems. Excellent
	    bibliography. Forward is the best-known proponent
	    of antimatter.
 
	    This also may be available as UDR-TR-85-55 from the contractor,
	    the University of Dayton Research Institute, and DTIC AD-A160
	    from the Defense Technical Information Center, Defense Logistics
	    Agency, Cameron Station, Alexandria, VA 22304-6145. And it's
	    also available from the NTIS, with yet another number.
 
	"Advanced Space Propulsion Study, Antiproton and Beamed Power
	    Propulsion", Robert Forward
 
	    AFAL TR-87-070 from the Air Force Astronautics Laboratory, DTIC
	    #AD-A189 218.
	    NTIS AD-A189 218/1	  PC A10/MF A01
 
	    Summarizes the previous paper, goes into detail on beamed power
	    systems including " 1) pellet, microwave, and laser beamed power
	    systems for intersteller transport; 2) a design for a
	    near-relativistic laser-pushed lightsail using near-term laser
	    technology; 3) a survey of laser thermal propulsion, tether
	    transportation systems, antiproton annihilation propulsion,
	    exotic applications of solar sails, and laser-pushed
	    interstellar lightsails; 4) the status of antiproton
	    annihilation propulsion as of 1986; and 5) the prospects for
	    obtaining antimatter ions heavier than antiprotons." Again,
	    there is an extensive bibliography.
 
	    "Application of Antimatter - Electric Power to Interstellar
	    Propulsion", G. D. Nordley, JBIS Interstellar Studies issue of
	    6/90.
 
    BUSSARD RAMJETS AND RELATED METHODS:
 
	G. L. Matloff and A. J. Fennelly, "Interstellar Applications and
	Limitations of Several Electrostatic/Electromagnetic Ion Collection
	Techniques", JBIS 30 (1977):213-222
 
	N. H. Langston, "The Erosion of Interstellar Drag Screens", JBIS 26
	(1973): 481-484
 
	C. Powell, "Flight Dynamics of the Ram-Augmented Interstellar
	Rocket", JBIS 28 (1975):553-562
 
	A. R. Martin, "The Effects of Drag on Relativistic Spacefight", JBIS
	25 (1972):643-652
 
    FUSION:
 
	"A Laser Fusion Rocket for Interplanetary Propulsion", Roderick Hyde,
	LLNL report UCRL-88857. (Contact the Technical Information Dept. at
	Livermore)
 
	    Fusion Pellet design: Fuel selection. Energy loss mechanisms.
	    Pellet compression metrics. Thrust Chamber: Magnetic nozzle.
	    Shielding. Tritium breeding. Thermal modeling. Fusion Driver
	    (lasers, particle beams, etc): Heat rejection. Vehicle Summary:
	    Mass estimates. Vehicle Performance: Interstellar travel
	    required exhaust velocities at the limit of fusion's capability.
	    Interplanetary missions are limited by power/weight ratio.
	    Trajectory modeling. Typical mission profiles. References,
	    including the 1978 report in JBIS, "Project Daedalus", and
	    several on ICF and driver technology.
 
	"Fusion as Electric Propulsion", Robert W. Bussard, Journal of
	Propulsion and Power, Vol. 6, No. 5, Sept.-Oct. 1990
 
	    Fusion rocket engines are analyzed as electric propulsion
	    systems, with propulsion thrust-power-input-power ratio (the
	    thrust-power "gain" G(t)) much greater than unity. Gain values
	    of conventional (solar, fission) electric propulsion systems are
	    always quite small (e.g., G(t)<0.8). With these, "high-thrust"
	    interplanetary flight is not possible, because system
	    acceleration (a(t)) capabilities are always less than the local
	    gravitational acceleration. In contrast, gain values 50-100
	    times higher are found for some fusion concepts, which offer
	    "high-thrust" flight capability. One performance example shows a
	    53.3 day (34.4 powered; 18.9 coast), one-way transit time with
	    19% payload for a single-stage Earth/Mars vehicle. Another shows
	    the potential for high acceleration (a(t)=0.55g(o)) flight in
	    Earth/moon space.
 
	"The QED Engine System: Direct Electric Fusion-Powered Systems for
	Aerospace Flight Propulsion" by Robert W. Bussard, EMC2-1190-03,
	available from Energy/Matter Conversion Corp., 9100 A. Center
	Street, Manassas, VA 22110.
 
	    [This is an introduction to the application of Bussard's version
	    of the Farnsworth/Hirsch electrostatic confinement fusion
	    technology to propulsion. 1500<Isp<5000 sec. Farnsworth/Hirsch
	    demonstrated a 10**10 neutron flux with their device back in
	    1969 but it was dropped when panic ensued over the surprising
	    stability of the Soviet Tokamak. Hirsch, responsible for the
	    panic, has recently recanted and is back working on QED. -- Jim
	    Bowery]
 
	"PLASMAKtm Star Power for Energy Intensive Space Applications", by
	Paul M. Koloc, Eight ANS Topical Meeting on Technology of Fusion
	Energy, special issue FUSION TECHNOLOGY, March 1989.
 
	    Aneutronic energy (fusion with little or negligible neutron
	    flux) requires plasma pressures and stable confinement times
	    larger than can be delivered by current approaches. If plasma
	    pressures appropriate to burn times on the order of milliseconds
	    could be achieved in aneutronic fuels, then high power densities
	    and very compact, realtively clean burning engines for space and
	    other special applications would be at hand. The PLASMAKtm
	    innovation will make this possible; its unique pressure
	    efficient structure, exceptional stability, fluid-mechanically
	    compressible Mantle and direct inductive MHD electric power
	    conversion advantages are described. Peak burn densities of tens
	    of megawats per cc give it compactness even in the
	    multi-gigawatt electric output size. Engineering advantages
	    indicate a rapid development schedule at very modest cost. [I
	    strongly recommend that people take this guy seriously. Bob
	    Hirsch, the primary proponent of the Tokamak, has recently
	    declared Koloc's PLASMAKtm precursor, the spheromak, to be one
	    of 3 promising fusion technologies that should be pursued rather
	    than Tokamak. Aside from the preceeding appeal to authority, the
	    PLASMAKtm looks like it finally models ball-lightning with solid
	    MHD physics. -- Jim Bowery]
 
    ION DRIVES:
 
	Retrieve files pub/SPACE/SPACELINK/6.5.2.* from the Ames SPACE
	archive; these deal with many aspects of ion drives and describe the
	SERT I and II missions, which flight-tested cesium ion thrusters in
	the 1960s and 70s. There are numerous references.
 
    MASS DRIVERS (COILGUNS, RAILGUNS):
 
	IEEE Transactions on Magnetics (for example, v. 27 no. 1, January
	1991 issue). Every so often they publish the proceedings of the
	Symposium on Electromagnetic Launcher Technology, including hundreds
	of papers on the subject. It's a good look at the state of the art,
	though perhaps not a good tutorial for beginners. Anybody know some
	good review papers?
 
    NUCLEAR ROCKETS (FISSION):
 
	"Technical Notes on Nuclear Rockets", by Bruce W. Knight and Donald
	Kingsbury, unpublished. May be available from: Donald Kingsbury,
	Math Dept., McGill University, PO Box 6070, Station A, Montreal,
	Quebec M3C 3G1 Canada.
 
    SOLAR SAILS:
 
	Starsailing. Solar Sails and Interstellar Travel. Louis Friedman,
	Wiley, New York, 1988, 146 pp., paper $9.95. (Not very technical,
	but an adequate overview.)
 
	"Roundtrip Interstellar Travel Using Laser-Pushed Lightsails
	(Journal of Spacecraft and Rockets, vol. 21, pp. 187-95, Jan.-Feb.
	1984)
 
    TETHERS:
 
	_Tethers and Asteroids for Artificial Gravity Assist in the Solar
	System,_ by P.A. Penzo and H.L. Mayer., _Journal of Spacecraft
	and Rockets_ for Jan-Feb 1986.
 
	    Details how a spacecraft with a kevlar tether of the same mass
	    can change its velocity by up to slightly less than 1 km/sec. if
	    it is travelling under that velocity wrt a suitable asteroid.
 
	"Tethers in Space Handbook, 2nd Edition", Paul A Penzo & Paul W
	Ammann. NASA Office of Advanced Program Development, 1989.
	    NTIS N92-19248/3	  PC A12/MF A03
 
	    It may be possible to obtain this handbook from:
		NASA Office of Advanced Program Development
		NASA HQ Code DD
		Washington, DC 20546
 
	NASA Conference Publication 2422
	Applications of Tethers in Space
	Workshop Proceedings Vols 1 and 2.
	[Proceedings of a workshop held in Venice, Italy, Octover 15-17, 1985]
 
    GENERAL:
 
	"Alternate Propulsion Energy Sources", Robert Forward
	    AFPRL TR-83-067.
	    NTIS AD-B088 771/1	  PC A07/MF A01   Dec 83 138p
 
	    Keywords: Propulsion energy, metastable helium, free-radical
	    hydrogen, solar pumped (sic) plasmas, antiproton annihiliation,
	    ionospheric lasers, solar sails, perforated sails, microwave
	    sails, quantum fluctuations, antimatter rockets... It's a wide,
	    if not deep, look at exotic energy sources which might be useful
	    for space propulsion. It also considers various kinds of laser
	    propulsion, metallic hydrogen, tethers, and unconventional
	    nuclear propulsion. The bibliographic information, pointing to
	    the research on all this stuff, belongs on every daydreamer's
	    shelf.
 
	Future Magic. Dr. Robert L. Forward, Avon, 1988. ISBN 0-380-89814-4.
 
	    Nontechnical discussion of tethers, antimatter, gravity control,
	    and even futher-out topics.
 
[Hey, Jon, how come this book isn't in the General section?
 
      Eugene F. Mallove and Gregory L. Matloff, THE STARFLIGHT
       HANDBOOK: A PIONEER'S GUIDE TO INTERSTELLAR TRAVEL, 1989
 
It's probably the best semi-technical introduction to interstellar
flight.  It's buried in Larry Klaes's list of interPLANETARY flight books in
part 8/13.]

From:	US4RMC::"[email protected]" "belbruno" 25-MAY-1994 16:04:45.53
To:	[email protected]
CC:	
Subj:	Conference: "PRACTICAL ROBOTIC INTERSTELLAR FLIGHT: ARE WE READY?"

                ************  ANNOUNCEMENT  **************

      The conference entitled,

      PRACTICAL ROBOTIC INTERSTELLAR FLIGHT: ARE WE READY? 

      will be held at New York University and the United Nations

      from August 29 - September 1, 1994. 

      The principal sponsor is The Planetary Society.

      Other sponsors include The British Interplanetary Society, The
      United Nations Outer Space Office, Jet Propulsion Laboratory,
      Mission From Planet Earth Study Office - NASA HQ,
      Geometry Center, National Space Society, Space Studies Institute,
      World Space Foundation, American Astronautical Society, New York
      University, American Astronomical Society, Mondo-tronics, Inc.

      The two topics focused on are 1.) Feasibility of performing a robotic
      interstellar mission in the near term that is both affordable and has
      a short flight time, and 2.) The search of planets orbiting nearby
      stars.

       ***************************************************************
        The keynote speakers are Dr. Robert Forward, and Dr. Carl
        Pilcher, Chief, Mission From Planet Earth Study Office, NASA HQ.
       ***************************************************************

      Other main speakers include Dr. Michael Klein of JPL, Dr. Richard
      Terrile also of JPL, and Dr. David Brin.

      Sessions are divided into 1. Interstellar Flight Concepts( Astro-
      dynamics, Propulsion), 2. Engineering Aspects(Miniturization,
      Electronics, Communications, Attitude Control) 3. Extra-solar
      Planetary Systems(Results, Methods), 4. Intermediate Prestellar
      Destinations(Heliopause, Oort Cloud, Gravitational Lense of the Sun)

                              *******
      A public event is planned to be held at the United Nations on the
      evening of the 30th which is sponsored by The Planetary Society.
      It will be held in the Dag Hammarskjold Auditorium at 6-9:00 PM.
      All technical sessions will be held at New York University in
      Greenwich Village.
                              *******

      The Organizing Committee is Edward Belbruno(Chair, Geometry Center),
      Louis Friedman(Planetary Society), William McLaughlin(JPL),
      Gregory Matloff(NYU), Thomas McDonough(Caltech), Gary Bennett(NASA),
      Bruno Augustine(Rand),Giovanni Vulpetti(British Interplanetary Society),
      Seth Potter(NYU)
      *****************************************************************

      For information on registration, abstract submittal, program, please
      contact Dr. Edward Belbruno at The Geometry Center; University of
      Minnesota; 1300 South Second Street; Minneapolis MN 55101, or
      call (612)626-1845, FAX (612)626-7131, e-mail [email protected].

      Abstract submittal deadline is July 15, 1994.
      Early Registration Deadline is July 15, 1994.

      The Registration fee prior to July 15 is $150, and $190 after July 15.
      Registration includes four days of technical sessions at NYU, Public
      event at the UN, and a dinner.  Checks made payable to Innovative Orbit
      Design at the above address.(10% discount if a member of a cosponsoring
      organization.)      

% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% From: [email protected] (belbruno)
% Newsgroups: sci.space.news
% Subject: Conference: "PRACTICAL ROBOTIC INTERSTELLAR FLIGHT: ARE WE READY?"
% Date: 25 May 1994 12:35:28 -0700
% Organization: The Geometry Center, University of Minnesota
% Approved: [email protected]
% Distribution: world
% Originator: [email protected]
% Apparently-To: [email protected]

Article: 2131
From: [email protected] (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space,alt.history.what-if,sci.space.tech
Subject: Re: Spaceflight in _1939_ was Re: Spaceflight in 1951
Date: 6 Jun 94 13:55:25 -0600
Organization: Fermi National Accelerator Laboratory
 
In article <[email protected]>, [email protected] (Bruce
Grubb) writes: 
 
[Crossposting to sci.space, a group which has been superseded by several
others; in this case, a historical discussion of the technology, I would
suggest sci.space.tech, and I've set followups there.]
 
> In article <[email protected]> [email protected] 
> (Daniel M Silevitch) writes:                                            
>>There was one technology available in 1951 that could have done the job:
>>the Orion system. 
 
No, Orion was not "available" in 1951.  In his book *Adventures of a
Mathematician* Stanislaw Ulam says he and C. Everett cooked up the
idea around 1955.  Freeman Dyson and Ted Taylor, with others,
developed it as an Air Force project a few years later (1958?) and
worked on it for several years.  You can read about it in Dyson's
*Disturbing the Universe*, in John McPhee's *The Curve of Binding
Energy*, and in Dyson's *Science* article "Death of a Project" (1965?
Check indexes around that time.) 
 
The original thread sprouted from a discussion of the novel *When
Worlds Collide* by Wylie and Balmer.  This book actually appeared in
the late Thirties, though the poster was reading a "new" paperback
edition published with the movie release in 1951.  I can say with
great authority that neither Orion nor any other nuclear rocket drive
was available before 1940!  But science fiction writers knew that
rocket travel beyond the earth, and release of "atomic" energy, were
possible and likely to be developed in the near future.
 
> As Carl Sagan pointed out in his series Cosmos Orion is a interSTELLAR ship.
 
I don't know what he said, but it really doesn't have the performance
to be a good interstellar drive.  James Nicoll has commented on this
in alt.history.what-if, and he is usually reliable in such matters.
 
> Using Orion in the space race which was to go the moon, Venus/Mars, other 
> planets, THEN interstellar flight would be like using a cross town bus to go 
> across the street.
 
Not true. Orion was intended (see the references I gave) to make the
solar system our neighborhood, with flights to other planets lasting a
few days to a few months.  Other stars are *much* further away-- tens
of thousands of times the distance of Pluto.
 
> Why not talk about a spacecraft designed by the British Interplanetary 
> Society?  You know the 1939 ship designed to go to the moon using 1939 
> technology?  The only information I have is that the thing existed.
 
This would make it roughly contemporaneous with *WWC*.  The BIS did a
paper study and published it in a 1939 issue of *Journal of the
British Interplanetary Society*.  A review of the design may be found
in *Smithsonian Annals of Flight #10*; I've forgotten the proper
title, but it's a collection of papers from a symposium on the history
of rocketry. 
 
Another place to read about it is the way-the-future-was book *High
Road to the Moon*, published by the BIS in the early Eighties and
written, if memory serves, by Robert Parkinson. I think this book
would be interesting to alternate-history buffs since it looks at the
milestones of space development envisioned by BIS members in the
Thirties, Forties, and Fifties, and contrasts them to the real events
of the Space Age.  It's a good place to find lovely paintings by R.A.
Smith... I've seen some of the originals hanging in the BIS's Lambeth
Road headquarters.
 
-- 
     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     [email protected]
   -   -       Internet:  [email protected]
     ~         SPAN/Hepnet:      43009::HIGGINS 

Article: 2140
From: [email protected] (Henry Spencer)
Newsgroups: sci.space.tech,alt.history.what-if
Subject: Re: Spaceflight in _1939_ was Re: Spaceflight in 1951
Date: Tue, 7 Jun 1994 17:01:58 GMT
Organization: U of Toronto Zoology
 
In article <[email protected]> [email protected]
(Bill Higgins-- Beam Jockey) writes: 

>....  You can read about it [Orion] in Dyson's
>*Disturbing the Universe*, in John McPhee's *The Curve of Binding
>Energy*, and in Dyson's *Science* article "Death of a Project" (1965?
>Check indexes around that time.)
 
Also of interest is the brief account in Herbert F. York's "Building
Weapons, Talking Peace" (I think that's the title).  He was the
unnamed man mentioned in Dyson's account, the one making the funding
decisions.  He basically thought Orion was a *very* long shot, with a
lot of major unsolved problems.  In particular, an independent review
said that General Atomic's estimates for development cost and schedule
were grossly optimistic.  He also notes that getting an Orion into
orbit would have required about a megaton of *fission* explosions, and
even in those days of atmospheric H-bomb tests, people were not happy
about that. 
 
>> As Carl Sagan pointed out in his series _Cosmos_ Orion is a interSTELLAR 
>>ship.
>
>I don't know what he said, but it really doesn't have the performance
>to be a good interstellar drive...
 
Sagan appears to be almost entirely ignorant of the extensive
technical literature on interstellar propulsion.  In particular, Bill
is correct:  Even a greatly scaled-up Orion (Orion gets better as it
gets bigger) is only marginally feasible for interstellar use. 
-- 
"...the Russians are coming, and the    | Henry Spencer @ U of Toronto Zoology
launch cartel is worried." - P.Fuhrman  |  [email protected]  utzoo!henry

Article: 2147
From: Aaron P Teske <[email protected]>
Newsgroups: sci.space.tech
Subject: Re: Spaceflight in _1939_ was Re: Spaceflight in 1951
Date: Wed,  8 Jun 1994 00:30:34 -0400 (EDT)
Organization: CRL Dialup Internet Access
 
Excerpts from netnews.sci.space.tech: 6-Jun-94 Re: Spaceflight in _1939_
w.. by Bill H. B. Jockey@fnalv. 

> > Using Orion in the space race which was to go the moon, Venus/Mars, other 
> > planets, THEN interstellar flight would be like using a cross town
> > bus to go across the street.
>  
> Not true. Orion was intended (see the references I gave) to make the
> solar system our neighborhood, with flights to other planets lasting a
> few days to a few months.  Other stars are *much* further away-- tens
> of thousands of times the distance of Pluto.
 
Actually, I recall reading (somewhere -- possibly nowhere serious, but
it seemed like a valid idea) that Orion could make for a fairly good
Moon base.  Build a superstructure, etc, whatever you need/want for a
basic Moon base, put on any equipment that can stand the strain, or
build the equipment to last, and then launch from Earth.  Before you
land, you drop a few (very very very clean) bombs below you, and
presto! you have a flat/slightly concave landling site.  Plus a Moon
base, which can then be expanded.  Any delicate equipment can be
brought over seperately... but then, how much thrust *is* there from
the blasts? Acceleration would presumably be jerky, but not too great.

  Anyone have some numbers to play with? 
 
                    Aaron Teske
                    [email protected]
-------------------------------------------------------------------------------
   "There can be no thought of finishing, for 'aiming for the stars,' both
    literally and figuratively, is a problem to occupy generations, so that
    no matter how much progress one makes, there is always the thrill of
    just beginning." - Dr. Robert Goddard (in a letter to H. G. Wells)
-------------------------------------------------------------------------------

Article: 2150
From: [email protected] (Glenn T. McDavid)
Newsgroups: sci.space.tech
Subject: Re: Spaceflight in _1939_ was Re: Spaceflight in 1951
Date: 8 Jun 1994 08:43:52 -0500
Organization: Another MCSNet Subscriber, Chicago's First Public-Access Internet!
 
[email protected] (Bill Higgins-- Beam Jockey) writes:
 
>You can read about it [Orion] in Dyson's
>*Disturbing the Universe*, in John McPhee's *The Curve of Binding
>Energy*, and in Dyson's *Science* article "Death of a Project" (1965?
>Check indexes around that time.)
 
"Death of a Project " was reprinted in Dyson's recent book From Eros to Gaia.
 
Glenn McDavid

Article: 2198
From: [email protected] (Henry Spencer)
Newsgroups: sci.space.tech,alt.history.what-if
Subject: Re: Spaceflight in _1939_ was Re: Spaceflight in 1951
Date: Sun, 12 Jun 1994 03:15:19 GMT
Organization: U of Toronto Zoology
 
I wrote:

>>....  You can read about it [Orion] in Dyson's *Disturbing the Universe*...
>Also of interest is the brief account in Herbert F. York's "Building
>Weapons, Talking Peace" (I think that's the title)...
 
The correct title is "Making Weapons, Talking Peace".  Basic Books, 1987.
 
However, having now read the book completely, I have to say that I don't
recommend it.  It sheds an interesting light on various events early in
the US space program -- York was one of the key people in US military
science+technology policy at the time -- but you don't want to read it
without considerable independent knowledge of what was going on.  There is
nothing much in this book that's actually *wrong*, but a lot of things
have been left out, sometimes to the point of giving a rather distorted
picture.  (For example, he mentions the embarrassment of the early Pioneer
program, with its five consecutive failures, and nearby he lauds the
military Discoverer program for achieving a successful mission two years
after program start, without mentioning that said mission followed
*twelve* consecutive failures, and was itself only a partial success.)
 
A frustrating, disappointing book.  Not worth your time unless you're
a serious space historian.
-- 
"...the Russians are coming, and the    | Henry Spencer @ U of Toronto Zoology
launch cartel is worried." - P.Fuhrman  |  [email protected]  utzoo!henry

Date: 8 Jun 1994 10:50:01 GMT
From: Tor Houghton <[email protected]>
Subject: Spaceflight in 1951
Newsgroups: sci.space,alt.history.what-if

Chris Owen ([email protected]) wrote:

:> Would this have actually *worked*? Surely the people inside the thing would
:>have been fried by the radiation, shattered by the blasts or squashed by the
:>acceleration? I certainly wouldn't want to bet on the astronauts surviving...

I think even they developed an experimental craft and launched it; gained
about 100m of altitude, I think.

"Put-Put" I think the name of the vessel was called.

;)

Tor.

-----------------------------------------------------------------------------
email: [email protected]                         "Old England is dying."
                                                      - The Waterboys
-----------------------------------------------------------------------------

Date: 8 Jun 94 11:11:24 GMT
From: Steve Linton <[email protected]>
Subject: Spaceflight in 1951
Newsgroups: sci.space,alt.history.what-if

Indeed. Of course it was powered by conventional explosives, not
nukes. Also the physics of this drive in air are quite different from
those in vacuum. 

To make Orion behave you:

(a) use small bombs: 1-2 ktons at most
(b) build the ship very big, with the manned bits standing on
    a very big shock absorber. The usual design has a domed 'pusher
    plate', which carries the bomb delivery system and not much more
    and then a set of huge shock absorbers which carry the rest of the
    ship (and possibly a second set of shock absorbers under the actual crew).

Date: Wed, 8 Jun 1994 13:13:47 GMT
From: Peter Venetoklis <[email protected]>
Subject: Spaceflight in 1951
Newsgroups: sci.space,alt.history.what-if

>>Chris Owen ([email protected]) wrote:
>
>>:> Would this have actually *worked*? Surely the people inside the thing would
>>:>have been fried by the radiation, shattered by the blasts or squashed by the
>>:>acceleration? I certainly wouldn't want to bet on the astronauts surviving.

Nuclear bombs are not infinitely destructive and do not emit infinite
radiation.  A properly sized shield and shock absorber can counter the
radiation and shock of a pulse.  Plus, you'd be using smaller devices,
in the 100's of tons or in the low kilotons. 

There was also a concept called HELIOS, which used a spherical
containment vessel with a throat and nozzle.  Small nukes would heat
reaction mass that would eject through the nozzle.  The nuke-e in the
office next to me did some work on the idea, and the physics and
materials are sound.  You can get about 1300 seconds of Isp out of it.
However, the pressure vessel is REALLY heavy (1000+ t) so the
benefits only become apparent for moving large masses around. 
____________________________________________________________________
Peter Venetoklis                           [email protected]
Senior Engineer - Mission Analysis      Northrop Grumman Corporation
Opinions are mine, not Grumman's, not Northrop's, not anyone else's.

Date: Wed, 8 Jun 94 10:19:04 EDT
From: [email protected] (Operator)
Subject: Test Ban and O. (was Re: Orion Ships (Was: Spaceflight)

>There was a drawing of the Orion spacecraft (by STAR TREK artist
>Rich Sternback) in Carl Sagan's COSMOS...the accompanying article stated
>that Daedalus *AND* Orion would be capable of 0.10c. I thought it sounded
>a bit unlikely, since the Orion spacecraft clearly was designed for MANNED
>missions within the solar system. Unlike Daedalus, it was 100% SSTO
>(oops: "Single Stage To Interstellar Space"-sorry:-).
>---
>Could anyone shed some light on this?
>
>MARCU$

The original Orion proposal (1958) was for a SSIPS
(single-stage-to-interplanetary-space) vehicle using 2000 small atomic
bombs.  For various (mainly political) reasons this was redesigned in
the early 1960s into an upper stage for the Saturn V for planetary
missions; the total number of "pulse units" would have been several
hundred (the exact # would depend on the mission, of course). After
Orion's cancellation, Dyson still championed the nuclear-pulse
technology and proposed (in a 1968 paper) a starship using several
MILLION (10e6) hydrogen bombs that would have reached an appreciable
fraction of c. 

Michael Flora
NASA - Marshall Space Flight Center

    It would probably help, in discussions of this sort, to distinguish
    between Orion A, Orion B, and Orion C.  I got that set of distinctions
    from Dr. uh, oh, it's on the tip of my tongue.  He named his children
    Cassandra, Pendragon, etc.  What *was* his name?
    
    							Ann B.