Conference noted::sf

    I thought we'd had ati-matter around in sub-atomic quantities for
    some time, but my physics is somewhat rusty and I may just be dreaming
    it.  Someone in the know?
    
    Dave W.

    Greetings....
    
    It was a while ago that I read the article, however I thought I
    kept a copy of it, so I'll endeavour to find it so that I may supply
    futher details....
    
    Mr Magoo

    Yes, we've had antimatter around in single-particle amounts for
    some times.  I think Dirac first predicted the existence of the
    positron, and it was duly discovered, which was a nice feather in
    the caps of Dirac personally and quantum theory generally.  The
    same reasoning predicts an antiparticle for every particle (though
    some particles, like photons, are their own antiparticles).  They
    found anti-protons next, then anti-neutrons.  So far, every particle
    either has a known antiparticle or is confidently expected to have
    one.
    
    I think the article that spawned this note was the announcement
    that someone had managed to get antiprotons and positrons together
    to form a small quantity of anti-hydrogen.  I don't know what the
    newspaper article meant by "usable quantities," but I suspect they
    would be usable primarily to particle physicists, not to the military
    or the energy industry.
                                                            
    Earl Wajenberg

    I believe bthat there's been anti-hydrogen around for several years
    now (though the individual atoms of it have had short lives); there's
    also a kind of additional "matter" where a particle and an antiparticle
    (say, an electron and a positron) orbit each other around a common
    center.  It isn't mastter or antimatter.  "gray matter?"
    
    Steve Kallis, Jr.
    
    P.S.: "Usable quantities" has to wait until we danswer the question,
    "Usable to whom?"
    
    -S
    

    The positron-electron pairs are called "positronium."  There is
    also "muonium," but I can't recall if that is muon-antimuon pairs,
    or a muon orbiting a nucleus in lieu of an electron.  I think both
    have been produced.
    
    Earl Wajenberg

    re .4, .5:
    
    <Whimper...>
    
    Nobody got the "gray matter" pun.  At least, I don't _think_ anyone
    did. ;-)
    
    Steve Kallis, Jr.
    
    P.S.:  Rather than "positronium" a better name would have been
    "electropositrum."
    
    -S
    

    The "gray matter" pun crossed my mind, but it didn't stay there.
    
    I agree, "positronium" isn't the best choice of name.  I also don't
    think much of "quark," "gluon," "up," "down," "strange," "top,"
    "bottom," "charm," or "color" as terms in elementary particle physics.
    There's a fashion for deliberately dumb names in particle physics
    these days; if the supersymmetry people have predicted correctly,
    there are an assortment of particles that they have thoughtfully
    named in advance as "squarks," "selectrons," and "gluinos."  Bleah.
    
    I don't know that any of the exotic atoms ever lasted long enough
    to form gases.  I'm sure there's someone out there who'd be delighted
    to get a PhD out of the attempt, if it hasn't been made already.
    
    Earl Wajenberg

    Were we supposed to comment?
    

    	Yes, indeed, antimatter would make a great power source by
    combining it with matter (prefeably hydrogen), as a matter-antimatter
    collision produces 100% conversion to energy (the best atomic fission
    and fusion reactions we currently have produce less than ONE PERCENT
    conversion to energy!):  A kilogram of matter combined with one
    kilogram of antimatter would equal the energy released by a 43-megaton
    hydrogen bomb detonation.
    	Sadly (for the feasibility of mass-producing Enterprise-like
    starships), creating antimatter is still a VERY
    time-and-energy-consuming process, with only a few atoms (antiatoms?)
    being produced at a time, and none of them lasting more than a matter
    of hours at best (the record is 10 hours).  In fact, all of the
    antimatter EVER produced in the laboratory would not fill a fraction
    of an ordinary flask.
    	The other "sad" fact is that antimatter has not yet been found
    existing naturally anywhere in the Universe - it does NOT mean that
    it doesn't exist, it's just that we haven't found anywhere in the
    relatively general vicinity of space.  There have been theories
    by reputable scientists that an entire antimatter universe exists
    somewhere in the parallel realities, but of course there is no proof
    of it, and getting there would be a bit tricky at present.
    	Even if we COULD produce enough antimatter to make starship
    travel under that kind of power practically possible, new problems
    would arise:
    	How do you contain antimatter onboard a matter starship?  One
    solution would be to place it in a magnetic "bottle", a magnetic
    field which would cause the antimatter to "float", thereby not touching
    any matter (Heaven help the crew if the power generator to the magnetic
    field shuts down!).
    	The other major problem is the matter-antimatter reaction itself;
    one could magnetically channel some antimatter into a spacial chamber
    on the ship to react with some stored matter (hydrogen).  The problem
    is that matter-antimatter explosions produce among other things
    gamma radiation and neutrons.  No magnetic fields can deflect or
    channel electrically neutral neutrons, and the shielding needed
    to protect the ship's crew and instruments from the gamma rays would
    be so huge as to be both mass and weight prohibitive!
    	These are the problems and challenges facing present technology
    in trying to harness the power of antimatter.  Far be it from me,
    an SF fan, to say that future technology could not overcome some
    or all of these hurdles, but they are present reality.  
    	
    	But that shouldn't stop someone from figuring something out!
    
    	Larry
    

    re .8:
    
    Well, I was hoping someone would build on it.
    
    Steve Kallis, Jr.
    

    re .9
    
    "An' so cap'n I kenna give ya warp drive, yoo'll have 'a make do
    with impulse power...."

    re. 11
    
    Another problem is 'we dinna seem to have impulse power either !!!'

        

Path: muscat!decwrl!labrea!rutgers!uwvax!umn-d-ub!umn-cs!hall!pww
From: [email protected] (Paul Wells)
Newsgroups: rec.arts.startrek
Subject: The future is now.
Message-ID: <[email protected]>
Date: 22 Mar 88 01:18:37 GMT
Organization: Cray Research, Inc., Mendota Heights, MN
Lines: 16
Posted: Mon Mar 21 19:18:37 1988
  
    An article in this week's AVIATION WEEK & SPACE TECHNOLOGY (March
21, page 19) magazine seems relevant to this group.  The title is
"USAF Predicts Antimatter Propellants Could Be in Use by Early 21st
Century." 
 
    The article quotes a USAF/Rand Corporation study which determined
that "relatively near-term methods exist to produce and store
antimatter at approximately $10 million per milligram."  Another study
by the Brookhaven National Laboratory indicated that gram-size
quantities of antiprotons could be produced for around $1 million per
milligram. 
 
    The article goes on to note that a shuttle-like space vehicle
would need about 35 milligrams of antimatter per flight. 
 
    It would seem that "impulse power" may soon be within our grasp.
All we need now is Warp Drive... 

    I saw an article recently which claimed that a Positron microscope is
    now available.  It functions the same way as an electron microscope
    except it uses the antimatter electron (aka positron) for the imaging.
    The positrons are generated by an isotope of Sodium (if I remember
    right).
    
    So much for the idea that the interaction of matter and antimatter
    will cause an explosion? 

    Well, it WILL cause little tiny explosions, at least.  Those positrons 
    eventually encounter electrons and annihilate, producing X-rays.
    
    Earl Wajenberg

    	For those of you interested in reading about the actual
    possibilities of antimatter (mirror matter) being used to propel
    future starships, I highly recommend the following book:
    
    	MIRROR MATTER: PIONEERING ANTIMATTER PHYSICS (1988 - HC, $18.95)
 	Robert L. Forward and Joel Davis
    	John Wiley & Sons, Incorporated
    	ISBN 0-471-62812-3
    
    	This book, which is available in any good general bookstore,
    will be of interest to science fiction fans because it not only 
    discusses antimatter physics and its use as a starship fuel in a 
    manner which neither insults nor overwhelms the average reader's
    intelligence, but it also devotes several chapters to antimatter
    as used in numerous SF books and films.  Their consensus is that 
    antimatter might really make a wonderful sublight starship power 
    source someday, but that faster-than-light (FTL) travel is impossible 
    regardless, based on the scientific knowledge we currently have in 
    this area.
                                                            
    	Another book by Forward on antimatter which I also recommend:
    
    	FUTURE MAGIC (1988 - Paperback, $3.95)
    	Dr. Robert L. Forward
    	Avon Books
    	ISBN 0-380-89814-4
    
    	FUTURE MAGIC also devotes itself to numerous currently SF-type 
    ideas on future science and technology (See SF Topic 667).
    
    	Larry
    

	The Air Force has plucked from science fiction an idea to blast 
rockets into space by using the power of antimatter. Just 35 milligrams of 
antimatter - smaller than a thumb tack - could put into orbit something as big
as NASA's space shuttle.
	Antimatter is the mirror image of matter. It consists of subatomic 
particles whose electric charges are opposite to those in matter. instead of 
negative electrons, for example, antimatter has positrons.
	When antimatter meets matter, they annihilate one another in a tre-
mendous burst of energy. Scientist hope to build rocket engines that use this 
energy.
	Antimatter in bulk does not exist yet, although physicists have made 
positrons and a few other constituents.  The stuff is difficult to store
because it explodes on contact with ordinary matter.  "You don't want to walk
around with this in your briefcase," says Robert Corley, manager of the anti-
matter development project of the U.S. Air Force Astronautics Laboratory at 
Edwards Air Base, Ca.  He says the storage problem may be solved by using
electromagnets to suspend antimatter in the middle of its container.

Newsgroups: sci.space,sci.energy
Subject: Charged Dark Matter
Date: 13 Sep 89 20:20:50 GMT
Reply-To: [email protected] (Paul Dietz)
Organization: U of Rochester, CS Dept, Rochester, NY
 
    I noticed the following abstract in the 9/89 Bull. APS:
 
   Charged Dark Matter    S. L. Glashow, Harvard Uuniversity
 
   We introduce as dark-matter candidates massive stable singly-charged
   particles (CHAMPs).  Relic champs and antichamps in equal numbers
   may provide critical density for the Universe and be the non-baryonic
   component of galactic halos.  Cosmological arguments constrain
   its mass to be between 0.1-1 million amu.  The flux of champs
   incident upon Earth should be ~0.1 grams/cm^2 Gy.  Its abundance
   by mass in the crust should be ~0.1 ppm, and in lunar material
   ~ 100 ppm.  Champs mimic superheavy isotopes.  At least half should
   appear as hydrogen, the rest should be bound to light nuclei.  We
   advocate the search for isotopes in this mass range in unrefined
   terrestrial, meteoritic and lunar samples.  This work was done with
   A. De Rujula and Uri Sarid.
 
    While I had thought that massive hydrogen-like atoms had been
ruled out at these densities by mass spec searches, it would be
extremely interesting if these particles actually exist. 
 
    If both positive and negative champs have accumulated in the
crusts of the solid bodies of the solar system (the negative ones in
light nuclei), they would form a readily storable matter-antimatter
fuel for energy generation, rocketry and weaponry; the energy needed
to dislodge a negative champ from its nucleus (and thus make it
available for annihilation) would be on the order of 1 billionth of
its rest energy. 
 
    I note that at the hypothesized rate (1e-10 grams/cm^2 year),
Earth is accumulating champs at the rate of 500 tonnes/year, which (if
continuously annihilated) would liberate 1500 terawatts of energy.
This exceeds the power of sunlight striking the entire Earth.
Renewable energy, indeed. 
 
	Paul F. Dietz
	[email protected]

    	In the March 1990 issue of SKY & TELESCOPE magazine, there is
    an article by Paul Davies on the attempts to find antimatter in
    the Universe.
    
        Larry
    

Re: early notes on silly subatomic particle names...

Anyone come across John Sladeks "absent particles" ?: subatomic entities which
exist but are absent in every model, F'rinstance the absent semi-nullitron, a
wooden billiard ball about yay big.

Mark.

RE: < Note 349.19 by WRKSYS::KLAES "N = R*fgfpneflfifaL" >
    -< Antimatter article in the March SKY & TELESCOPE >-

So for those of us who don't subscribe to this particular rag, what's the
answer?

RDWHAHB

Article: 1673
From: [email protected] (Henry Spencer)
Newsgroups: sci.space.tech
Subject: Re: Possibilties
Date: Wed, 4 May 1994 20:58:41 GMT
Organization: U of Toronto Zoology
 
In article <[email protected]>
[email protected] (Ryan Pehrson) writes: 

>What are the possibilities - in the far future, I grant you - of using 
>matter-antimatter reactions for propulsion?
 
Quite good, in the relatively near future, if anybody funds it properly.
 
The particle-physics people are making antimatter now, in infinitesimal
quantities at horrendous expense.  Re-optimizing their hardware for bulk
antimatter production (which probably means building new accelerators,
not just modifying old ones) would give us enough -- with prolonged
production runs -- to start test-firing antimatter-powered rocket engines.
More efficient production techniques would help a lot, but brute-force
scaling of existing ones would work.
 
Understand, we're talking here about engines that use very small amounts
of antimatter to heat large amounts of reaction mass (liquid hydrogen, 
probably).  That's the most effective way to use antimatter if all you
want to do (for starters) is explore the solar system.  For interstellar
use, if you can make really large amounts of antimatter, pure annihilation
engines that exploit the annihilation products directly begin to become
interesting.
 
Handling antimatter involves a lot of engineering, but no real technical
breakthroughs.  Cooling it down to near absolute zero can be done with
essentially off-the-shelf technology; physicists are doing this sort of
thing all the time now, to study low-energy atoms in isolation.  Once
you've got it cool, you can move it around with electric or magnetic
fields.  The details need a lot of working out but no fundamental obstacles
are apparent.
 
Nobody is supplying significant funding for any of this right now.
 
>...  Anyway, when you 
>slam a particle and its opposite together, you release all of that energy,
>not just a fraction...
 
Actually, that's true with electron-positron annihilation, but 
proton-antiproton reactions are messier.  They go via various intermediate
stages involving (mostly) charged particles, and even after all is said
and done there are some neutrinos left over.
 
This is actually a good thing.  Making practical use of energetic gamma
rays is tricky.  Charged particles are a lot easier to handle.  Much (not
all) of the energy of the proton-antiproton reaction is embodied in charged
particles for long enough that a magnetic nozzle is practical.
 
>On another note, where is research as far as resisting gravity?  I mean 
>actively repulsing from it like two magnets put S-pole to S-pole.  (I know 
>gravity isn't exactly the same mechanism.)
 
Well, that last is an understatement.
 
There are some theoretical possibilities for manipulating gravity to be
found in general relativity.  Unfortunately, they require equipment that
is many orders of magnitude beyond today's engineering -- things like
neutronium rotors spun up to a significant fraction of the speed of light
in a big hurry.  Whether these possibilities will ever be of practical
use is hard to say; they certainly aren't today.
 
We need major new physics before antigravity can be had with hardware
we can actually build.  There are no particularly good indications that
such physics might be just around the corner.  There have been a few
false alarms, but nothing that has held up on close examination.
-- 
"...the Russians are coming, and the    | Henry Spencer @ U of Toronto Zoology
launch cartel is worried." - P.Fuhrman  |  [email protected]  utzoo!henry

Article: 2366
From: [email protected] (Geoffrey A. Landis)
Newsgroups: sci.space.tech
Subject: Re: Anti-Matter Engine
Date: Thu, 30 Jun 1994 15:26:14 -0400
Organization: NASA Lewis Research Center
 
In article <29JUN199421524205@mich1>, Chip McVey <[email protected]> 
writes:

> So when is the anti-matter engine going to be ready to go? 
 
The latest data I have is that Fermilab now has the capability to
produce 2 nanograms of antimatter per year.  The upgrade expected in
1998 will allow production of 20 ng of antimatter per year.  The cost
of running the facility to produce 20 ng per year will be $15 million.
 
At the moment, the record for *storing* antimatter is 2 picograms in
an electromagnetic ("penning") trap. 
 
Geoffrey A. Landis, mercenary scientist
Nyma, Incorporated
 

    Interesting -- of course, since they generate the energy levels they
    need by collide protons and anti-protons, I suspect they're able to
    create more than 20 nanograms of anti-protons per year.  

Article: 4174
From: [email protected] (Bruce       Scott          TK  )
Newsgroups: sci.astro,alt.sci.planetary,sci.space.policy
Subject: Re: Storing Antimatter
Date: 22 Aug 1994 14:05:07 GMT
Organization: Rechenzentrum der Max-Planck-Gesellschaft in Garching
Sender: bds@slcbds (Bruce       Scott          TK  )
 
In article <[email protected]>, [email protected]
(Mr M P Hughes) writes: 

|> 'Scuse the slight irrelevance to this group - I don't get sci.physics!!
|> 
|> If one were to construct a spacecraft propulsion system based on 
   matter/antimatter
|> reaction, how would the energy of reaction be prevented from destroying 
   the ship?
|> Approx. how efficient is this method (ie what % of energy is
   converyed to ship's kinetic energy)? And what's the easiest way to
   stare the antimatter? 
 
This was covered in an issue of the Planetary Report a few years ago. I
remember only the gist.
 
[By the way, please use carriage returns in your lines. If you are using
DOS, throw it away.]
 
The problem with straight matter-antimatter reactions is that you get
gamma rays as a product, and you cannot focus gamma rays. Lets use the
reaction e + ep --> 2 gamma as an example, where ep is a positron and you
get two gamma rays because you have to conserve momentum in the center-of-
mass reference frame. You could in principle get a 100 percent efficient
thrust out of this since the exhaust velocity is c, the speed of light.
Unfortunately, you cannot focus the gammas: they come out in all directions
with a net thrust of zero. You have to use a "working fluid", a medium
which absorbs the gammas as heat energy and then expands thermally from
the rocket nozzle. I do not remember the best figure of the various
proposals to do this, but it is on the drawing board. It was claimed
that with _present_ technology these could outperform fusion rockets
with _forseeable_ technology. I cannot evaluate this, but it translates
to a good fraction of a percent worth of mc2 for available energy. Of
course, the rub is that only a very low thrust is available with present
technology. Nevertheless, one can access the outer Solar System quite
readily even with a thrust capability of 0.0001 g, and you begin to
seriously outperform the _ideal_ limit for chemical rockets if you can
get a thrust of 0.001 g, if you need a very large change in velocity.
The reason is that you need carry much less of the total percentage as fuel
to get a given velocity change, and the thrust level doesn't matter so
much if you can smear that change out over a period of a few years.
 
Note: with a continuous thrust of 0.00015 g, accelerating the first half
of the trip, you can get a one-way trip to Saturn (10 AU away) in 2 years.
 
In round numbers, 1 g is 10 m/sec2, or 0.5 AU/day2, and 
10 AU/year2 is 0.00015 g. The time taken for a nonrelativistic trip,
stop to stop, over a distance s with a continuous acceleration/deceleration
A, is t = 2 sqrt(s/A).
 
-- 
Gruss,
Dr Bruce Scott                             The deadliest bullshit is
Max-Planck-Institut fuer Plasmaphysik       odorless and transparent
[email protected]                               -- W Gibson

Article: 4175
From: [email protected]
Newsgroups: sci.astro,alt.sci.planetary,sci.space.policy
Subject: Re: Storing Antimatter
Date: Mon, 22 Aug 94 16:24:00 SET
Organization: In2p3
 
One may store antimatter (say antiprotons to fix the ideas) in a
suitable combination of magnetic and electric fields. This is called
(if I can trust my memory) a Penning trap. It has actually be done at
the Low Energy Antiproton Ring at CERN, where a group from (among
others) Harvard, stored antiprotons this way, in order to measure its
mass. The record was something like two months. 
 
One might speculate about molecules that my contain antiprotons, just
like buckyballs may contain ordinary metal atoms and hemoglobin stores
oxygen molecules.
 
This is not so farfetched. Many proteins fulfill there function because of
the way they are shaped, rather than because of there chemical `makeup'.
 
One may imagine a protein, shaped such that the combination of magnetic and
electric fields is such that it is a miniature Penning trap.
 
Opening this trap would liberate immediately 1 GeV of energy: it's a sort
of 1 GeV battery.
 
Applications could for instance be the clean-up of cancercells.
 
>Approx. how efficient is this method (ie what % of energy is
converyed to ship's kinetic energy)? And what's the easiest way to
stare the antimatter? Hmm, that's a problem.... 
 
The experiment at CERN uses a burst of 10^8 antiprotons to fill the trap
and than manages to catch a few handfulls.
 
Ronald

Article: 4177
From: [email protected] (Tom Clarke)
Newsgroups: sci.space.policy,sci.astro,alt.sci.planetary
Subject: Re: Storing Antimatter
Date: 22 Aug 1994 16:16:48 -0400
Organization: University of Central Florida
 
In article <[email protected]> [email protected] writes:
 
> One might speculate about molecules that my contain antiprotons, just
> like buckyballs may contain ordinary metal atoms and hemoglobin stores
> oxygen molecules.
 
Since antiprotons don't react with valence electrons, it is also
conceivable that an ionic crystal, like table salt, consisting of
antiprotons and some positive ions like lithium or sodium would be
stable against annihilation.  The person who pointed this out to me
also said they wouldn't want a crystal of antiprotide salt on their desk. 
 
Lithium!  It must be lithium.  Then lithium anitprotide would
obviously be "dilithium" :-) 
 
Tom Clarke
 
-- 
Tom Clarke, [email protected]
 
He that complies against his will,
Is of his own opinion still.       Samuel Butler 1612-1680.

Article: 4179
From: [email protected] (Jon Leech)
Newsgroups: sci.astro,alt.sci.planetary,sci.space.policy,sci.space.tech
Subject: Antimatter engines (was Re: Storing Antimatter)
Date: 22 Aug 1994 10:48:32 -0400
Organization: The University of North Carolina at Chapel Hill
 
In article <[email protected]>,
Bruce	    Scott	   TK	<[email protected]> wrote:

>The problem with straight matter-antimatter reactions is that you get
>gamma rays as a product, and you cannot focus gamma rays.
 
    I thought you got pions for a short time first. Forward's design uses a
magnetic nozzle to channel the charged pions.

    Followups to sci.space.tech.
    Jon
    __@/

Article: 4181
Newsgroups: sci.astro,alt.sci.planetary,sci.space.policy
From: [email protected] (Jerzy Tarasiuk)
Subject: Re: Storing Antimatter
Sender: [email protected]
Organization: Warsaw University Physics Dept.
Date: Tue, 23 Aug 1994 14:58:47 GMT
 
>>>>> On 22 Aug 1994 09:45:57 GMT, [email protected] (Mr M P
Hughes) said: 

H> Approx. how efficient is this method (ie what % of energy is converyed to
H> ship's kinetic energy)? And what's the easiest way to stare the antimatter?
 
1. the % is _very_ small if photons are emitted (unless ship speed
   is comparable to speed of light) - need some matter to heat it;
   in some SF stories ships were collesting matter from space...
   it is a chance to solve fuel mass problem (can you imagine how
   much fuel needs ship to be able to travel with speed about 0.1c?
   using anti-matter allows fuel mass < ship mass).

2. to store _large_ amount of anti-matter need make some solid state
   magnet or superconductor of it and keep it moving in high vacuum
   in magnetic field (allows A-M amount comparable with total mass);
   maybe idea of molecules with anti-proton catched in miniature
   Penning trap (from Ronald <[email protected]>) is good, too;
   question what anti-matter/matter ratio can obtain? 0.01? more?

Article: 4182
Newsgroups: sci.space.policy,sci.astro,alt.sci.planetary,fuw.talk
From: [email protected] (Jerzy Tarasiuk)
Subject: Re: Storing Antimatter
Sender: [email protected]
Organization: Warsaw University Physics Dept.
Date: Tue, 23 Aug 1994 15:14:49 GMT
 
>>>>> On 22 Aug 1994 16:16:48 -0400, [email protected] (Tom
Clarke) said: 

> One might speculate about molecules that my contain antiprotons, just
> like buckyballs may contain ordinary metal atoms and hemoglobin stores
> oxygen molecules.
 
Tom> Since antiprotons don't react with valence electrons, it is also
Tom> conceivable that an ionic crystal, like table salt, consisting
Tom> of antiprotons and some positive ions like lithium or sodium
Tom> would be stable against annihilation.  The person who pointed
Tom> this out to me also said they wouldn't want a crystal of 
Tom> antiprotide salt on their desk.
 
I doubt if it is possible: there is a theorem that single charged
particle cannot be held be electrostatic field. Note that, unlike
ionic crystal (where all atoms have positively-charged nuclei), need 
keep _negatively_ charged particle between electrons...

Article: 68926
From: [email protected] (Chris Thompson)
Newsgroups: sci.astro
Subject: Re: Storing Antimatter
Date: 22 Aug 1994 16:55:08 GMT
Organization: University of Cambridge, England
 
In article <[email protected]>, [email protected]
(Bruce Scott) writes:

[...]
|> 
|> Note: with a continuous thrust of 0.00015 g, accelerating the first half
|> of the trip, you can get a one-way trip to Saturn (10 AU away) in 2 years.
|> 
|> In round numbers, 1 g is 10 m/sec2, or 0.5 AU/day2, and 
|> 10 AU/year2 is 0.00015 g. The time taken for a nonrelativistic trip,
|> stop to stop, over a distance s with a continuous acceleration/deceleration
|> A, is t = 2 sqrt(s/A).
 
Bear in mind that solar gravity is about 0.00060 g at the earth's
orbit, so there is no way that you are going to achieve anything like
a straight-line trajectory with these accelerations. Or, to put it
another way, it would be a serious mistake to start by cancelling out
the earth's orbital motion and then try blasting directly away from
the sun! 
 
Chris Thompson
Internet: [email protected]
JANET:    [email protected]

Article: 69059
Newsgroups: sci.astro
From: [email protected] (Jonathan Jeremy Silverlight)
Date: Tue, 23 Aug 1994 23:45:08 GMT
Subject: Re: Storing Antimatter
 
There's a 'Science Fact' article in the July 1992 'Analog' magazine
- 'The Demon under Hawaii' - by Geoffrey A Landis which mentions this
idea.  He says all that dilithium is what powers the hot-spot!
 
>Lithium!  It must be lithium.  Then lithium anitprotide would
>obviously be "dilithium" :-)
>
>Tom Clarke
 
Jonathan Silverlight           Internet: [email protected]
5 Portugal Road,
Woking,
Surrey GU21 5HB
UK
(+44) 0483 721464

Article: 69095
From: [email protected] (Bruce       Scott          TK  )
Newsgroups: sci.astro
Subject: Re: Storing Antimatter
Date: 24 Aug 1994 10:26:49 GMT
Organization: Rechenzentrum der Max-Planck-Gesellschaft in Garching
Sender: bds@slcbds (Bruce       Scott          TK  )
 
In article <[email protected]>, [email protected] (Chris
Thompson) writes: 

|> In article <[email protected]>, [email protected]
|> (Bruce Scott) writes:
|> [...]
|> |> 
|> |> Note: with a continuous thrust of 0.00015 g, accelerating the first half
|> |> of the trip, you can get a one-way trip to Saturn (10 AU away) in 2 years.
|> |> 
|> |> In round numbers, 1 g is 10 m/sec2, or 0.5 AU/day2, and 
|> |> 10 AU/year2 is 0.00015 g. The time taken for a nonrelativistic trip,
|> |> stop to stop, over a distance s with a continuous 
      acceleration/deceleration
|> |> A, is t = 2 sqrt(s/A).
|> 
|> Bear in mind that solar gravity is about 0.00060 g at the earth's orbit,
|> so there is no way that you are going to achieve anything like a straight-
|> trajectory with these accelerations. Or, to put it another way, it would be
|> a serious mistake to start by cancelling out the earth's orbital motion and
|> then try blasting directly away from the sun!
 
Good point; I forgot about this.  But once you are out to Jupiter, the
solar gravity would be negligible.  And it is still true that the outer
Solar System is readily accessible with 0.001 g. 
-- 
Gruss,
Dr Bruce Scott                             The deadliest bullshit is
Max-Planck-Institut fuer Plasmaphysik       odorless and transparent
[email protected]                               -- W Gibson

Article: 4188
From: [email protected]
Newsgroups: sci.astro,alt.sci.planetary,sci.space.policy,sci.space.tech
Subject: Re: Antimatter engines (was Re: Storing Antimatter)
Date: Tue, 23 Aug 94 10:57:14 SET
Organization: In2p3
 
In article <[email protected]>
[email protected] (Jon Leech) writes:
 
>>The problem with straight matter-antimatter reactions is that you get
>>gamma rays as a product, and you cannot focus gamma rays.
>
>    I thought you got pions for a short time first. Forward's design uses a
>magnetic nozzle to channel the charged pions.
 
One proton-antiproton annihilation at rest produces on average about five
pions, half charged and half neutral. The roughly 2 GeV of available energy
is shared equally between them.
 
The charged pions can be focussed, but the neutral ones decay almost
instanteneously into gamma rays. The latter fly off in all directions
and there effect cancels out.
 
Ronald

    "Most of our so-called reasoning consists in finding arguments for
  going on believing as we already do."  -James Robinson-