Conference 7.286::space

Look  for  a past issue of a New York Times Sunday Special Section on
Star Wars. There was a section in  there  about  a  magnetic  cannon,
though as a weapon rather than a orbital boost assist.
���
	-SES

Newsgroups: net.sf-lovers
Path: decwrl!amdcad!cae780!weitek!sci!daver
Subject: Re: More on _Alien(s)'_ weaponry
Posted: 17 Sep 86 20:19:08 GMT
Organization: Silicon Compilers, Inc., San Jose, CA
 
Actually, i never considered electromagnetic launchers in the guns
(partly because of the muzzle flash--i didn't think there should be
any in an em launcher).  However.  There was an article in the local
paper yesterday saying that the army was investigating putting rail
guns in tanks.  Wow.  So if the rifles were portable rail guns, you
might see a muzzle flash from the escaping plasma.  I'ld think the
barrel would have a different design if it were a rail gun, but it's
hard to say.  Certainly it fits in with the compact electric power
supply that's been implied by other bits of technology in the movie. 
 
So.  Has anyone figured out where the fuel for the flame throwers is
kept?
 
 
david rickel
cae780!weitek!sci!daver

    As I recall railguns, the payload would have to be restricted to
    strong raw materials (like lumps of metal) since the acceleration
    is in the 300+ G range. There certainly won't be any launches of
    computerized vehicles :-)
    					-Brian
    

    Re: .3
    
    The Copperhead guided artillery shell is subjected to a 6000G kick
    at launch.  Granted, any spacecraft would be much more
    complex than a guided projectile, but hardened electronics and optics
    can be made to survive a very-high-G launch.
    
    Unfortunately people are another matter, although Jochen Mass, the
    German race driver, was subjected to a 216G (instantaneous) deceleration in 
    an accident in 1980 or '81.  He really got his bell rung, but lived to
    tell about it. 

    There used to be a program on tv in the early '60s that was about
    a human factors researcher.  It was a turkey, but in the opening
    sequence, they showed some footage of a decelleration test at
    Almagordo (I think that's where the sled was [is]).  Anyway, the
    footage was real enough, and I believe the subject was an Air Force
    major; his chest literally *collapsed* in the film.  I read an article
    about it that said that he walked away from the test.  Any idea
    how many G's he got?

    That was AF Col. John Paul Stapp.  He was an MD (I think) doing
    research on the human body's G tolerance.  He was subjected to 42-50G,
    over several seconds.  The rocket sled was accelerated to ~650mph,
    then decelerated to a stop, within about five miles.  The test track
    was at Holloman AFB, right near the White Sands Missile Range.
    
    Col. Stapp sustained some pretty serious eye damage (large numbers
    of burst blood vessels), but was able to recover.
    
    Major trivia note: legend holds that Northrop engineer Jack Murphy,
    who worked on the project, was the originator of Murphy's Law.
    
    -George

    	Whether someone could survive high-G's or not does not seem
    to be as important to launching manned spaceships on a railgun as
    is the question of who would WANT to risk painful injury by flying
    on a railgun?
    
    	Unless the railgun engineers could think of a way to cushion
    the G-forces, I do not think the railgun would be very practical
    for anything other than cargo or probe launches, both unmanned.
    
    	Larry
    

    When I first posted the note I wasn't considering manned launching,
    just a cheap system to get raw material into space. A manned system
    would probably be a few miles long assuming a "confortable"
    accelaration of about say 6 gees. 

    Actually, most of the stuff I've read on rail guns (or accelerators)
    assumed they would be placed on the moon where the lack of atmosphere
    plus the lower gravity would make them reasonable to use.  Somewhere
    I got the idea it would be prohibitive in terms of energy to launch
    some payload via rail gun from the Earth.
    

  How about this for getting people into orbit based on a rail gun?

  Fire some *huge* mass in the proper trajectory with a massive rubber band
strapped across it with the other end attached to a ship.  The rubber band's
expansion and contraction could be regulated to avoid killing the people
in the ship.  I assume that all the energy imparted to the *huge* mass
originally fired at hight accelerations/energies would be transferred to
the ship, causing the mass to return to Earth based on the energy required
to get it going in the first place, trajectory, etc.

  I don't know my physics, but this is a crude model of an idea off the top
of my head.  I suppose portions of the energy imparted to the original mass
could be transferred to the ship with the remaining energy left in the large
mass so that the ship and mass could rendezvous in orbit.  I like it.  Any
comments on whether it could be done?

  Of course, this applies to any solar body with gravity that is a pain in
the neck to overcome - Earth, Moon, etc.

John

    re: .10--Would you like to be the first to test it?  I betcha the
    vehicle would slam into the mass on the first launch.  On the second
    launch, the rubber band would break.  On the third, the mass would
    some down in some embarassing place, like the middle of Red Square.
    I think this idea needs more thought.  :-)
        John Sauter

    	In Joe Haldeman's SF novel, THE FOREVER WAR, he had the crews
    of spaceships which had to accelerate and decelerate at high speeds
    (and thus high-G forces) go into special pressure suits immursed
    in huge tanks of liquid, which cushioned the otherwise killing forces.
    
    	Haldeman was dealing with starships in combat situations in
    this scenario, but he seemed to have done his homework, and I think
    the basic principles apply.
                                
    	Larry
    

re: -1

I'm not sure I see how a pressure suit is going to effect the parts of your
body that want to "... stay at rest until acted up by an outside force". 

Won't your eyeballs get slammed against the back of your head no matter what
you do to pressurize you body?

-mark

  So there a few kinks to be worked out...

  Take *two* large masses and put the rubber band between them and launch
the ship like a slingshot?

  And the mass would set down in Red Square on the second try - the rubber
band broke that time.

  The idea could just be used to send up things which can stand lesser
acceleration than bulk mass, like computers.

John

    I seem to recall an Arthur C. Clark book either profiles of the
    future or the promise of space where he mentions the use of astronauts
    being submerged in a viscous fluid for acceleration to high gee
    about 20.  Sounds like it would be real easy to choke on a broken
    mouthpiece for air.

    	Using liquid tanks to cushion hig-G's on astronauts goes back
    as far as the Russian space pioneer Tslivosky, who designed a manned
    rocket with the suggestion that the passenger be put in a "bathtub"
    of water to survive the increased gravitational forces of the rocket's
    take-off thrust, and the astronaut would also be wearing a pressure
    suit.
    
    	Larry
    

    Aside from the possibility that full or partial liquid immersion
    might provide good distribution of pressure forces over the body
    (but I'd expect that our specially molded seats should come close),
    it's not clear what other advantages might accrue.
    
    o  As mentioned, simple immersion does not itself change the fact
       that the body is being accelerated, and there will still be a
       major whop in the backside.
    
    o  Complete immersion might, however, have another undesirable side-
       effect.  Though the liquid would likely be incompressible, its
       effective weight would go 'way up.  Pressure likewise.  Sort
       of like a very sudden descent to depth - followed by a sudden
       "return to the surface" when the acceleration cuts out.
    
       If the acceleration went on for any appreciable length of time,
       seems as if there would be a problem with the bends when it
    stopped...
    		- Bill
    

    An object immersed in liquid would be partially isolated from the
    acceleration force since, depending on the viscosity of the liquid,
    the object would tend to stay in place (remember inertia?).  There
    would be a "shock absorber" effect if the liquid was compressible.
    Eventually the object would be subject to the full acceleration
    force, but the gradual (in comparison) build-up of force would
    seem to me to be less damaging to a person's body than a sudden
    acceleration would be.  Of course, I'm glossing over pressure
    distribution of the liquid and lots of other important considerations,
    but the idea has some general merit.
    

As  I recall reading about this (about 15 years ago) part of the deal
that has not been mentioned before was total imersion. This  includes
a  liquid  that  coul substitute for air! Getting O2 into the body is
not a big problem, but getting the CO2 out is pretty tough.

Anyway,  the  point  was  to  take   advantage   of   the   lack   of
compressability  of  most  fluids  to  cushion  the  accleration. For
instance, a single fluid mass (as a chest with lungs full too)  would
not tend to get crushed (as described in a earlier reply).

This  does not say anything about the eye problems by that particular
person.

Though this may present a method of withstanding high  G  forces,  it
would make space travel much less appealing to me.
���
	-SES

An interesting thought comes to mind to simulate what might happen to internal
body parts...

Take a box (make belive body), immerse it in water, put it in your car and go
out for a spin.  Will the eggs (organs) inside be protected by the water?  :-) 

-mark

    I'd like to inject a little physics:
    
    1) re: low G rail launchers. Accelerating from rest to 18,000 mph
           at 6 Gs would require a rail launcher just shy of 400 miles
           long.
    
    2) The change in acceleration due to staying put in the fluid is
       negligible. Take a simple case of an object in a 40 foot fluid
       filled vessel accelerating over 2 seconds at 10 G. The vessel
       travels 640 feet in 2 seconds, so even if the body started at
       one end of the vessel and slid all the way down, it can stay
       inside the vessel only if it undergoes acceleration of at least
       9.5 G to travel 600 feet in 2 seconds.
    
    							-Brian
    

RE: 21, etc.

The idea is to have the density of the object (person) be the
same as the density of the fluid.  In that case you will not move
at all relative to the fluid.

The problem with high Gs is that some of your parts that should
be on top of other parts tend to move down.  The result is that
you tend to be flattened.  If you were in a fluid that was the
same density as you and if all of the parts of your body were the
same density you would be OK no matter how high the Gs. 

The problem is that your body is not all the same density.  You
will not tend to flatten out but your bones will try to settle
through the rest of you.  The eyeball problem will not exist.  In
air the soft parts tend to be pushed down.  The eyeballs settle
into your head.  With enough Gs your eyeballs and brain will be
forced down through your neck or ears. This will happen because
there is no counterbalancing force.  If you are immersed in a
fluid that is as dense as your tissue your eyeballs, brains, etc.
will be floating in the fluid.  They will not be forced down in
your skull. 

The opposite problem will exist.  Your bones will tend to settle
through your flesh.  This will be a smaller force because the
density difference between your bones and flesh is less than the
difference between your flesh and air.  The result is that you
should be able to experience larger accelerations.  The exact
amount depends on the range of densities in your body and the
separation forces that the parts of different densities can
withstand.  Putting a fluid in the lungs eliminates the least
dense part of you body.  The air.  For very high accelerations
you would have to make sure that your sinuses and inner ear were
filled as well. 

Just think of it as a centrifuge being used to separate a mixture
of liquids of different densities. 

RE: 20

If the egg is in a fluid that is at the same density as the egg
and if the box is strong enough that it is not deformed you
should be able to drive your car into a bridge abutment at high
speed without breaking the egg.  I don't plan to try that one.
Maybe dropping it off of a high building...  It might help to
have something in the box that would tend to keep the egg
centered in the box.  Whatever you used would have to be the same
density as the fluid.

	Tony 

    That makes more sense, but it bears repeating that only when all
    body cavities (lungs, stomach, sinuses, ...) are filled with the
    fluid can you begin talking about really high accelerations.
    
    And it also bears repeating that the pressures involved may be higher
    than would be experienced with a really good couch (where the only
    pressure comes from your own mass - though this could be approached
    if you were floating JUST below the liquid surface).  The difference
    is that the pressure is VERY evenly distributed, and - to the degree
    that your body is, or becomes under pressure, incompressible - everything
    will stay in balance.
    				- Bill
    

    re:.19
    
    I was going to mention this, but you beat me to it, Steve.
    
    If I remember correctly, the liquid was an oxygenated
    fluorocarbon.
    
    --- jerry

VNS TECHNOLOGY WATCH:                           [Mike Taylor, VNS Correspondent]
=====================                           [Nashua, NH, USA               ]

          SDI Railguns Could Also Launch Small Space Probes

    Scientists at the Jet Propulsion Laboratory (JPL) are proposing a 
    novel scheme that would use railgun technology developed for SDI to
    launch small space probes.  The plan is of interest because of
    rising backlog of experiments caused by delays in the Space Shuttle 
    program.  Advances in microelectronics have reduced the weight of
    conventional spaces probes from hundreds of pounds to less than 3. 
    A 2.2 pound spacecraft launched by an orbiting railgun would achieve
    an exit velocity of about 6 miles/sec., scientists say, allowing it 
    to travel the 750 million miles between Earth and Saturn in just
    two years.

    {Electronics - January 21, 1988}

    [This sounds like they are grasping at straws.  Has anyone even
    figured out how to aim the dumb thing, never mind turn it to
    point at Saturn?  But using military equipment for useful
    things is not a bad idea:  Maybe the DoD will let Federal Express
    use the B-2 stealth bomber. - MJT]

  <><><><><><><>   VNS Edition : 1501    Thursday  4-Feb-1988   <><><><><><><>

VNS Letters to the Editor:
==========================

From: Bob Stetson ............................................. Maynard, MA, USA

    SDI Railguns could launch probes to Saturn and beyond?

    How can you fire a probe at Saturn from orbit without altering the
velocity and direction of travel of the Railgun that fired the
projectile?  Newton said that it would alter the course of the Space
Platform, in one of his laws of motion.  Can I assume that the
platform is a temporary one with its own retro and propulsion systems?
The net result would be like firing a cannon.  The recoil would be amazing. 

================================================================================
From: Jody Bobbitt ........................................... Marlboro, MA, USA

    In re: queries on railgun technology in VNS

    I studied railgun technology when I did a report on it several
years ago.  Apparently there is no problem with aiming it (it's like a
"gun" that way).  But the experiments they were doing at the time were
with 9 mm lexan cubes (very small and light), and even then they were
having trouble creating enough electromagnetic force to give it the
thrust it might need to reach "escape velocity".  One way they
increase the force is, after creating an electromagnetic field behind
the projectile, they set off explosives in the end of the barrel,
which compresses the field and increases the thrust.  Doesn't make the
whole gizmo too reusable, though (one drawback for space-based railguns...) 

    Jody Bobbitt
    Marlboro, MA

================================================================================
From: Andy Vesper ............................................ Marlboro, MA, USA

    From the VNS TECHNOLOGY WATCH:

          SDI Railguns Could Also Launch Small Space Probes

    Scientists at the Jet Propulsion Laboratory are proposing a novel
    scheme that would use railgun technology developed for SDI to
    launch small space probes.  ...
    {Electronics Jan 21, 1988}

    [This sounds like they are grasping at straws. Has anyone even
    figured out how to aim the dumb thing, never mind turn it to
    point at Saturn?  But using military equipment for useful
    things is not a bad idea, maybe the DoD will let Federal Express
    use the B-2 stealth bomber. --mjt]

    Actually, railgun technology was originally thought up as a cheap
way of launching spaceships, space probes, and satellites.  The concept
has been used for this purpose in science fiction for many years;
probably before Ronald Reagan was even in the movies.  Aiming it is no
harder than aiming a rocket, and much cheaper since you only need to
build the hardware once for the launcher, instead of once per payload.

    Using military *technology* (not equipment) for useful things is
indeed a good idea, but increasing military spending is a very
inefficient way of improving civilian technology.  The other way
around works much better:  Fund basic research and both civilian and
military technology will benefit.  The U.S. electronics industry
(military and civilian) was greatly helped by the *public domain*
research done at Bell Labs before the breakup of A.T. & T.  Where would
we be now if only one company could build transistors? 

    Andy V 

  <><><><><><><>   VNS Edition : 1502      Monday  8-Feb-1988   <><><><><><><>

    Just a tangent to the rail gun discussion (one of several in the
    conference): while returning to NRO from Hudson along one of the
    back roads that run parallel to 290, I noticed a sign in front of
    a building under construction:
    
    		 Future Site
    
    		 KAMAN
    
    		 Electromagnetic Launch Research
    
    Right in our own backyard . . .
    

    The April '90 issue of Scientific American has a brief article on a
    proposed electromagnetic launcher to be built at Barking Sands on Kaui
    island.  This widget would be capable of delivering about 100kg into a
    polar orbit.  The article mentions a couple of applications like
    resupplying a space station with consumables such as water, (in polar
    orbit?), or launching a fleet of small satellites as part of a space
    based cellular phone system.  It should be noted though that AvLeak
    reports the SDI Brilliant Pebbles vehicle would weigh in at about 100kg.
    
    Mike H 

    Why a polar orbit.
    
    Is it because Russia is up that way or because polar orbits intersect 
    all points - so to speak - above the planet and consequently an object 
    in orbit will cross over the others path. 
    
    Question: what sort of energy factors are involved in capturing an object
    launched into polar orbit. Be it up down or across the axies. 
    
    What I do know is taht I read an article in Space Markets about Polar  
    orbits being used in LEOs for small comsats known as 'store and
    sends' and these are pretty low cost sats. Developed by Uni's and
    schools and the Russians.  They can deliver a message anywhere in the
    world within 24hrs. Great for low priority and startup companys.
    
    It would be great if you could photocopy and send me the article by    
    intermail. We only got Sci Am January yesterday in Australia.   
    - SIMON MANSFIELD SNO 10/1.
    
    many thanks,
    
    simon
    

    You've hit the nail on the head.  The ICBMs are expected to be coming
    over the pole, so a high inclination orbit is necesary for the
    interceptors intended to hit them.  It costs more energy to put
    mass into high inclination orbits however so the space station orbit
    will have a much lower inclination.  This makes the suggestion quoted
    in the article of delivering consumables to the space station via
    the barking sands launcher pretty funny.  The article follows.
    
    Mike H
    
    [Copied without permission from Scientific American, April 1990.]
    
    ZAP! - Coil guns offer to orbit small cargoes on a regular schedule.
    -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
    Decades ago, in teh heyday of pulp science fiction, there was the
    mass driver: an electromagnetic accelerator that shot vehicles into
    outer space without benefit of rocket engines.  Futurist Gerard
    K. O'Neill envisioned mass drivers on the moon slinging supplies
    to space colonies.  In the early 1980's, with the advent of the
    Strategic Defense Initiative, or "Star Wars," the mass driver begot
    the rail gun: a supposedly cheap, simple version of the electromagnetic
    propulsion that could be used to fire interceptors at rising Soviet
    missiles.  As strategic peace breaks out and Star Wars continues
    its long slide, the rail gun has begotten a new generation of mass
    driver, poised to deliver small packages to orbit for a fraction
    of the cost imposed by rocket technology.
    
      A group of researchers from Sandia National Laboratories, best
    known for such projects as the maneuvering nuclear warhead, has
    proposed the construction of an 800-meter-long electromagnetic
    accelerator at Barking Sands on the Hawaiian island of Kauai.  The
    site, says M. Bill Cowan of Sandia, is perfectly situated for
    delivering small satellites to polar orbit: the ground track of
    the launch vehicle would pass largely over ocean, thus alleviating
    safty concerns.  In Sandia's design -- a coil gun, not a rail gun
    -- electromagnets wuld induce a current in a 450-kilogram aluminum
    armature and accelerate it through a series of coils.  The armature
    would carry with it a 400-kilogram projectile, which would depart
    the coil gun's barrel at about six kilometers per second.  Once
    above the atmosphere, the projectile would fire a rocket to kick
    about 100 kilograms of payload into orbit.  In contrast, big boosters
    such as the Titan place only a small percentage of the launch mass
    in orbit.
    
      What has changed since the days when mass drivers were pulp science
    fiction?  Power storage for one: the capacitors that will provide
    enormaous bursts of power for the fraction of a second it takes
    the coil gun to fire have improved more than tenfold in the past
    five years and could well do so again, Cowan says.  For another,
    Sar Wars experiments with coil guns, rail guns and light gas guns
    have advanced the technology in many areas.  Before the SDI-funded
    boom in electromagnetic propulsion, the largest experimental systms
    built were a factor of a million short of what was needed to put
    payloads in orbit; current systems will merely have to ber scaled
    up by a factor of 1,000.
    
      Certain problems still need to be worked out, Cowan notes.  The
    satellites that the coil gun fires will have to be redesigned to
    survive acceleration forcs more than 1,000 times that of gravity.
    Although proximity fuzes and other simple circuits have been built
    to withstand more than 100,000 g's, the standard for modern
    communications satellites is closer to 10 g's.
    
     Engineers will also have to make progress in aerodynamic shields:
    current nose cones are designed for ultra-high speeds only in very
    thin air, not at sea level.  And designers will have to cope with
    the superheated plasma that forms whenever the armature bumps against
    the barrel of the gun at six kilometers per second.
    
      If a couple of years of funding show that such obstacles can be
    overcome, Cowan says, Kauai could have an operating coil gun by
    the turn of the century.  The estimated $1.3-billion price tag is
    cheap compared with the $20 billion or more projected for the
    development of successors to the space shuttle.  Both could loft
    roughly the same amount of material into space during their operting
    lives, although the cil gun would do so in much smaller pieces.
    
     The coil gun could put 10,000 small payloads in orbit at a cost
    per pound significantly lower than that of the cheapest big rockets,
    according to Miles R. Palmer, a physicist at defense contractor
    Science Applications International Corporation.
    
      That brings up the question of why anyone might want to put 10,000
    small payloads in orbit.  Palmer contends that a mass driver could
    send supplies -- such as air, water, food and other acceleration-hardy
    items -- into orbit to provision a mission to Mars or resupply a
    space station far more cheaply than conventional rockets could.
    He also envisions a global cellula-telephone network, based on
    thousands of satellites in low Earth orbit, which could attract
    20 to 30 percent of worldwide spending for telecommunications by
    the turn of the century.  Perhaps Dick Tracy's two-way wrist radio
    will join the mass driver in the ranks of pulp visions come to life.

    
    [Illustration showing a map of Kauai with the location of the launcher
    marked in red.
    
    Caption - Barking Sands on the island of Kauai is the proposed site
    for the eltromagnetic launcher. In addition to the 800-meter gun,
    the launch facility (red) would also require as much electricity
    as the island's total present generating capacity.  Sonic booms
    fromt he launches, occurring as often as every 10 minutes, could
    be audible as far as 30 kilometers from teh line of flight (as
    indicated by shaded area).  The island location has a precedent"
    Project HARP, a proram that fired shells as high as 180 kilometeres
    during the 1960's sited its gun in Barbados.]

    
    	What are the problems that would occur with soft acceleration of a
    projectile.  Could not a circular design be made with an opening
    to release the package for orbit ?  
    
    Chris

From:	ARGUS::VINO::LEROUF::CASEE::VNS "The VOGON News Service  29-Oct-1992
To:	VNS-Distribution
CC:	
Subj:	VNS #2694  Thu 29-Oct-1992

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VNS TECHNOLOGY WATCH:                           [Mike Taylor, VNS Correspondent]
=====================                           [Littleton, MA, USA            ]

                                   Supergun

    Essentially a giant BB gun, the prototype Super High altitude Research
    Project (SHARP) launcher is being assembled in the hills east of
    California's Lawrence Livermore National Laboratory, which has spent
    three years and $4 million developing it. The first SHARP gun will shoot
    an 11 lb. projectile into a mound of sand at 9,000 mph. Instead of
    gunpowder, the "bullet" will be propelled by hydrogen gas that is
    compressed by a 1-tom piston in a 270 foot long, 14 inch diameter
    barrel and blow the projectile out. If this test goes well, John
    Hunter, the Livermore physicist who heads SHARP, hopes to build
    bigger guns that eventually launch 7-ton payloads into orbit. Hunter
    figures such a device could deliver payloads for $500 per kilogram, vs.
    $20,000 per kilogram using the space shuttle.

    {Business Week Oct 12, 1992}

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<><><><><><><><>   VNS Edition : 2694    Thursday 29-Oct-1992   <><><><><><><><>

Anybody out there care to estimate how loud this would be? (e.g., it'll
kill everything within a 2 mile radius)   I'm not up to the physics involved.

Somehow the thought of a large amount of hypersonic gas hitting the
quiet morning sky conjurs up big bangs!   I assume that some amount of the
energy will be emitted as sound/pressure waves -- but can that be quantified
at all?


The Saturn V was once called the loudest man-made object ever made (I can't
remember the "stereo system wattage" equivalent -- big numbers though).  They
had to schedule F-1 firings at Marshall so the wind wasn't blowing towards
Huntsville or the sound of the engines running would blow out store windows
downtown.   I've been there -- it's quite a ways to Huntsville from MSFC.
I wonder how this'll compare?


- dave

    Gerald Bull lives!  The pyromaniac in me would love to see this
    work, but I really can't see this as a better means into orbit. 
    The acceleration would destroy all but the toughest payloads.
    /jlr

From:	DECWRL::"[email protected]" "Dani Eder"  1-FEB-1993 14:11:02.17
To:	[email protected]
CC:	
Subj:	Livermore gun launcher

On Jan 27th, 1993 I visited Dr. John Hunter, of the Lawrence Livermore
National Laboratory, to discuss gas gun launchers and in particular the
large gun he has in testing.  His ultimate goal is to build guns that
can fire useful-sized payloads into space.  The present gun is a scaled
down version to demonstrate the technology, and which can be used for
hypervelocity testing later.

The gun is located in the 'back lot' test area in the mountains near
Livermore, CA, several miles from the Laboratory itself, which is
where the offices are.  The design goal of the gun is to fire a
5 kg projectile at 4 km/s.  Using a lighter projectile, 1.5 kg, it
should get 6 km/s.  These are 1/2 and 3/4 of orbital velocity.

It was intended to be a 1/10 linear scale version of a large 'space
gun', which would launch several ton projectiles at the same speed
(mass scales as L^3).  The projectiles would then use on-board
rocket propulsion to make up the rest of the velocity to Earth
orbit, leaving some hundreds of kg of useful payload in orbit.

The gun consists of a pump tube and barrel mounted at right angles
to each other.  It was designed this way so the barrel could be
elevated for altitude shots without moving the pump tube, which
is bigger and heavier.  At the current location, all the shots will
be horizontal into filled plastic water jugs, backed by sandbags,
backed by a large hillside.  This is because the Livermore test
area is much too small to do altitude shots.  If Hunter gets some
more money, he wants to move the gun to Vandenberg, where he
can shoot over the ocean.  The expected range will be 400km vertical
with an 88 degree elevation and 700 km downrange when firing for
maximum range (near 45 degrees elevation).  You don't want to
shoot at 90 degrees, because then the projectile falls back on you.

The pump tube is about 75 meters long, 14 inches in ID, and 17-20
inches in OD.  It is thicker at the ends.  In operation, the pump
tube has a 1 ton piston (about 1 meter long) located near the
far end from the barrel intersection.  A methane-air mixture is
pumped in to 10 atmospheres.  In front of the piston, the volume
is filled with hydrogen gas.  The methane-air mix is ignited,
and the piston drives down the pump tube at several hundred m/s.

The hydrogen is compressed and heated until a rupture disk gives
way, somewhere over 10,000 psi.  The rupture disk is a stainless
steel plate with an x-shaped groove cut in it.  The depth of the
groove is controlled so that the plate ruptures and opens in four
petals.  The hydrogen gas then accelerates the projectile.

The piston is shrinking the volume in the pump tube faster than
the projectile is creating volume by moving in the barrel, so
for a while the pressure continues to rise, reaching a peak of
50,000 psi.

The barrel is 30m long and 10cm in ID, and about 20-25 cm in
OD.  The end is covered by a polyethelyne sheet (about 10 mils)
that keeps air out of the barrel.  Most of the air is pumped
out before firing.  The residual air blows away the plastic
film before the projectile gets there.  

The test projectiles are made of Lexan, about 50cm long, 10
cm in diameter, and mass 5 kg.  The early tests were with 
compressed air driving compressed air, and reached 400 m/s,
the most recent tests were compressed air behind the piston
driving hydrogen gas, and reached 800 m/s.  For comparison,
this is about the speed of an artillery shell.  These early
tests are to make sure the mechanical parts work okay, the
instrumentation works, etc.  They are starting now on the
combustion-driven shots, which will start at about 10% of
a full propellant load, and ramp up in small steps, in case
something starts to give.  It is a real experimental mode.
They will also get data on speed vs. gas load to use in
later, less than full power shots.

Among the things to fire out of this gun, after the gun itself
is tested, is heat shield designs, and scramjet combustors.
There is currently no other way to test above Mach 8 for
more than a few milliseconds in a shock tunnel.  Firing
scramjet parts into real air at high speed and at reasonable
scale has excited some interest already.

Hunter's next gun would be one that uses a heat echanger rather
than a driven piston to create the hot, high pressure hydrogen.
This concept comes from the work done at Brookhaven on particle-
bed nuclear rockets (Timberwind project).  The gun would have
no nuclear parts, but uses the same principle of small particles
with lots of surface area to get high heating rates.  By going
with a particle bed heat exchanger, the pump tube, which is
the biggest piece of hardware, goes away, shrinking the gun
cost by 50%.  This would be a small gun to demonstrate the
design, then later guns would scale up to useful payloads.

The reason Hunter didn't start with this type of gun was the
Timberwind work was highly classified until after he had started
building the current gun.

Testing up to full power should take until late Feb. or Early Mar,
it takes about 3 days to clean the gun and prepare for another
shot, plus whatever glitches turn up.  The gas gun that belongs
to the University of Alabama at Huntsville, which I visited
a month ago, can get about 1 shot per day, and has been doing
that for 25 years.

Dani Eder

% ====== Internet headers and postmarks (see DECWRL::GATEWAY.DOC) ======
% Received: by enet-gw.pa.dec.com; id AA25555; Mon, 1 Feb 93 11:11:52 -0800
% Date: Mon, 1 Feb 93 11:22:30 CST
% From: Dani Eder <[email protected]>
% To: [email protected]
% Subject: Livermore gun launcher
% Sender: [email protected]

From:	DECWRL::"[email protected]" "Bruce Dunn"  6-FEB-1993 17:10:28.80
To:	[email protected]
CC:	
Subj:	Project HARP

Dr. G. Bull was murdered several years ago in Europe.  He was probably
killed as a result of his activities related to military weapons in
the Middle East.  In the 1960s, Dr. Bull was associated with project
HARP (High Altitude Research Project), run out of McGill University in
Montreal, with U.S. Army funding.  Project HARP involved the use of
large guns to fire instrumented ballistic projectiles and rockets to
high altitudes.  The program seems to have been terminated in
approximately the mid 1960s.   Bull later became an arms designer and
arms broker, who had dealings with Iraq among other countries.
Following are some notes on the HARP project, which make an
interesting comparison with the light gas gun launcher recently
described by Dani Eder. 

Paper 1:  Bull, G.V. (1964) Development of Gun Launched Vertical Probes for
Upper Atmosphere Studies.  Canadian Aeronautics and Space Journal 10:236-247.

This paper was written to accompany a speech made by Bull in Toronto in May
1964.

In the Introduction to the paper:

"During the past several years, both theoretical and experimental
investigations have been undertaken to determine the applicability of guns to
scientific studies of the ionosphere.  Such possibilities have intrigued
ordnance workers for many years, but involve a complex mixing of advanced
gunnery techniques, scientific experiment considerations and economics.

"In late 1961, with material support from the US Army, McGill
University undertook the development of a 16 inch gun system.  In
early 1962 this program came under full support of the US Army through
the Army Research Office and the Ballistic Research Laboratories" In a
section on sub-caliber ballistic projectiles, Bull says: 

"For example, in the case of a 16 inch naval gun which normally fires
shells in the 3,000 lb. class at velocities of 2,800 fps, velocities
as high as 6,000 fps can be obtained with shot weights of the order of
400 lb., the sub-caliber vehicle in this case having a ballistic
coefficient considerably higher than the normal shell.  By re-design
of the gun (i.e. extending the chamber and barrel) to optimize at this
lighter shot weight, velocities approaching 7,000 fps are possible." 

     A series of sub-caliber "Martlet 2" vehicles were built, which
were sub-caliber and rode the barrel in a fall-away sabot.  Canted
fins on the projectile maintained aerodynamic stability, and spun the
projectile up so that it was stable once leaving the atmosphere. 
These were fired at elevations of from 60 to 90 degrees from a 16 inch
naval gun (on loan from the U.S.) which was located in Barbados.  The
gun was bored out to 16.5 inches and made into a smooth-bore cannon. 
Altitudes of approximately 500,000 to 600,000 feet (100 miles, 160 km)
were projected for this arrangement, and early trials reported in the
reference cited went as high as 112 km.  Martlet vehicles carried
instruments made from discrete solid-state electronics - they were
potted in a mix of epoxy and sand (!) and the designers did not seem
to have any real trouble getting the electronic to survive the launch
acceleration which peaked at approximately 20,000 g.  Martlet vehicles
also routinely carried a liquid mixture of trimethyl-aluminum and
triethyl-aluminum to be released at high altitudes for ionosphere
studies.  Another option was to carry sodium-thermite mixes which when
ignited would release sodium vapor (a type of experiment similar to
the Pegasus satellite barium releases). 

     If projectiles of a similar weight were fired for range rather
than height then ranges of up to 150 to 200 miles were calculated,
depending on the ballistic coefficient. 

Shots from the gun were routine and relatively inexpensive.  Bull states:

"Normally, loading of the gun can be accomplished in under one half hour,
allowing a firing rate of one an hour."

"Standard service propellant available as surplus (WM/.245) has been
used, and the gun geometry has not been modified.  Firing programs are
planned for the summer and fall of this year [1964] when the gun
barrel will be extended and lighter sabots used with propellant
designed to match the light projectiles, which should extend the
Martlet 2A apogee to 200 km." 

[if I remember correctly, the gun was fitted with a fiberglass muzzle
extension which was successful in improving the performance]. 

"The economics of the gun launched probe has been as predicted, with the
Martlet 2A airframes loaded with TMA/TEA and a flare in the nose cone varying
in price between $2500 and $3500, with gun launch costs (propellant and gun
wear) included."

After having discussed ballistic projectiles, Bull discusses gun-
launched rockets:

"Gun fired artillery rockets have been developed extensively since
World War II and normally must withstand barrel acceleration loads of
the order of 30,000 g along with the rotational loads superposed by
shell spin.  The performance of this type of rocket is only of
marginal interest in the vertical probe application where non-spinning
(from a stress viewpoint) vehicles are flown at acceleration levels of
less than 10,000 g and relatively very large rocket motors are desired
with high mass fractions. 

     In May of 1963, work was started on what was designated as the
Martlet 3A rocket assist vehicle as part of the HARP program.  The
objective of this activity was the development of a 16 inch gun
launched probe which would carry some 40 lb. of payload to altitudes
in the 500 km range." 

     The Martlet 3A and later 3B rocket vehicles were sub-caliber and
used various solid propellants in various configurations. The main
problem with gun launched rockets is supporting the solid propellant
during the launch acceleration so that it does not collapse into the
internal cavities molded into the propellant grain, and a lot of
development work was performed to investigate the performance of
various solid propellant grains. 

          From their knowledge of the performance of the 16 inch gun
system and general information about the specific impulse and mass
fraction of solid fuel rockets, it was calculated that it would be
fairly easy to put a payload into orbit using the HARP gun and a
multistage solid fuel rocket.  Orbital Launch Vehicle Characteristics
from Figure 31 in the Bull paper: 

Total launch weight:     2000 lb.
Stage 1 weight:          1440 lb.
Stage 2 weight:           403 lb.
Stage 3 weight:           117 lb.
Payload:                   40 lb.

Muzzle velocity          4500 fps
Mass fraction             0.8
Specific impulse          300 sec (vacuum)

[Note from B.D.:  I think that the Isp estimate of 300 sec is overly
optimistic, and would be happier believing 280 with the limited
expansion ratio nozzle which could be fitted onto a gun launched
rocket ; the mass fraction however is probably less than could be
achieved using modern composite materials for the motor case -
overall, the calculations probably hold up ok] 

     The first and second stages were to be fired at relatively low
altitude, but clear of the atmosphere.  The third stage was to
circularize the orbit, and would be fired horizontally at orbital
altitude. 

    Such a vehicle was never built, although motors of the first stage
size were developed.  The HARP group was also involved in exploring
the possibilities of launching liquid fueled rockets from the gun. 
These could be thin-shelled as long as they had no gas spaces in them
(you can accelerate a balloon full of water at any g force you like,
as long is it is fully supported during the acceleration). 

Paper 2: Eyre, F.W. (1966) The Development of Large Bore Gun Launched
Rockets.

Canadian Aeronautics and Space Journal 12:143-149.

"The concept of a rocket launched from a gun is not new.  It will
suffice to affirm in this paper that the gun launched artillery rocket
was in full development during the Second World War and this
investigation still continues. Like so much work in allied fields, a
great deal of what has been done and is being done is classified and
cannot here be repeated." 

"The conventional solid propellant gun, firing meaningful projectiles,
currently appears able to develop a maximum muzzle velocity of some
6000 to 9000 fps.  Allowing an 80% recovery of muzzle kinetic energy
as potential energy, this corresponds to a ceiling for sounding work
of some 800,000 to 1,000,000 ft. (say 160 to 200 statute miles).
Significant improvements beyond this level must come either from use
of a different type of gun or from rocket boost during vehicle flight,
which is here considered." 

"Figure 3 shows muzzle velocity vs. shot weight for the Barbados gun. [HARP]"

"Assumed conditions:  Max. pressure 60000 psi
                      Fixed charge, 1000 lb. M8M propellant
                      Web size optimized."

[some approximate data points from Figure 3 graph, and from Figure 4 showing
acceleration vs. shot weight]

Shot weight  Muzzle velocity  Max. acceleration

 500  lb.          7700 fps       13,000 g
1000  lb.          6400 fps        9,000 g
1500  lb.          5700 fps        6,500 g
2000  lb.          5200 fps        5,000 g

Eyre then goes into a long technical discussion related to how to
support propellants of various types in a solid fuel rocket during the
gun acceleration.  Perhaps the neatest concept is to simply fill all
empty spaces in the rocket with a fluid which then can support the
propellant grain hydrostatically during launch (sort of a rocket
water- bed).  The rocket is then accelerated using some form of pusher
plate, which seals the liquid in.  The plate drops away after launch,
and the fluid is then vented or drained before ignition. 

With regard to practicality and performance, Eyre writes:

"It has transpired in design studies that although structural problems
do arise due to the acceleration loads, and additional problems are
posed by the necessity to use a folding stabilizer assembly, mass
fractions almost as high as conventional rockets can be achieved and
the design problems are partially alleviated by an all supersonic
flight regime. 

     Given this condition the advantage of the gun can be seen in that
a typical vehicle of mass fraction 0.8 would have an apogee of 176
miles used conventionally, 257 miles at 1000 fps launch, 342 miles at
2000 fps, 435 miles at 3000 fps, 529 miles at 4000 fps and so on." 

     Eyre then discusses the fabrication of a full-scale, full bore
(16 inch) motor with a weight of 1450 lb., designated the Martlet 4A
and designed for the Barbados gun.  At the time of writing of the
paper, it does not appear as if this had yet been test launched - I do
not know how far the program was carried before it was canceled. 

"Current work is directed towards development and application of a
thin plastic wear resistant coating [they were worried about excessive
wear on the rocket casing], and launching of 16 inch motors to
investigate scale factor effects. At the time of writing  [1966] full
bore Aerojet General Corp. grains are awaiting launch. ... At the
present time a heavy test program is about to commence with many
agencies participating and for the most part full scale hardware ready
for launch." 

     In summary, up until the time of writing of the later of the two
quoted papers in the mid 1960s, HARP under Dr. Bull appeared to have
been highly successful using a surplus 16 inch naval cannon in firing
projectiles to high altitudes and in firing solid fueled rockets.  His 
comment on vehicle design for guns of different scales is interesting: 

"Obviously since launch weight (ie payload) is increasing roughly as
the cube of the scale, while peak accelerations are decreasing
linearly, the larger the gun the simpler the vehicle engineering
problem." 
--
Bruce Dunn    Vancouver, Canada   [email protected]

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% Message-Id: <[email protected]>
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% Subject: Project HARP
% From: Bruce Dunn <[email protected]>

In .35, the comment is made:-

>					      You don't want to
> shoot at 90 degrees, because then the projectile falls back on you.

This clearly neglects to consider the rotation of the earth from the time the 
projectile is fired until it falls back to surface level again. The distance 
between the gun and the impact point would depend primarily on latitude and 
elapsed time between the two events. At the equator a 1-minute `flight' would
mean an approximately 500 yard range. (unless my calculations are suspect!)

  In addition to that you have to figure in Coriollis (sp?) effect which may
shift the flight of the projectile slightly to the side. I'm sure they
considered all of that. 

  The reason I say that was that just before WWII when the last Battle Ships
were designed there were no computers to calculate the effects of Coriollis
effect on a shell. The new 16" guns that were being manufactured for the
Iowa class Battle Ships and what ever class proceeded the Iowas, had so much
additional range that they would miss if all of these things were not
considered. 

  To solve this problem they invented a large electro mechanical computational
device to do the calculations that were necessary to factor in effects of the
rotation of the earth on the ballistic flight of the shell. 

  I believe that in the last refit of the Iowa class Battle Ships, the devices
were replaced with modern computers. 

  George