Conference 7.286::space

    	Please give us more details on this type of starship, and also
    see SPACE Topic 212.
    
    	Larry
    

    	It's interesting to note that while the trip may take 14 years
    Earth time.  The astronauts would age very little during the trip.
    This due to the velocity attained.  So they actually save weight
    cause now they don't have to bring so many paperback books with
    them to pass the time! :-)
    
    Rich (Who's always looking for the positive side of things...)

        Note -1:
        It's interesting to note that while the trip may take 14 years
        Earth time.  The astronauts would age very little during the
        trip.
        This due to the velocity attained.  So they actually save weight
        cause now they don't have to bring so many paperback books with
        them to pass the time!
        
    
    Depends on rate of acceleration!
    
    Tally-ho,
    
    Ray.
    

    There was a young fellow called Bright
    Who could cycle at the speed of light
    He set off one day
    In a relative way
    And came home the previous night!

    Re 313.4.The second line doesn't scan.
    
    	      			Cheers,
    					Dennis				
    
    				

    Mr. Moderator, if this isn't the right location for this reply,
    please feel free to move it where it belongs....
                                                                   
    The following article appeared in Tuesday's (May 17, 1988) Natural Science
    Column of "The Christian Science Monitor" and was written by Robert
    C. Cowen.  I apologize for the lateness of this reply, but feel
    that the content of the article still has relevance today.
    
    Reprinted without permission from "The Christian Science Monitor".
    I accept all responsibility for all typo's that follow.
    
    

    ---------------------------------------------------------------------------
    
    The Starship Enterprise would boldly go nowhere without its antimatter
    fuel.  But in the "real world," this most powerful of all possible
    energy sources has remained a plaything for experimenters and a
    gimmick for sci-fi authors.
    
    Perhaps it's time to take it more seriously.  What farsighted engineer
    can ignore a substance that, upon contact with normal matter, induces
    the total transformation of both forms of matter into pure energy?
    
    That's why the United States Air Force has been sponsoring studies
    of antimatter uses as part of a $5 million-a-year high-energy materials
    program.  Col. Ross Nunn, who commands the USAF Astronautics
    Laboratory, says "the 'giggle factor' is over" in considering
    antimatter applications, according to the industry journal Aviation
    Week.
    
    Engineers like antimatter, in theory, because, with it, they can
    store more energy in a smaller mass and volume than with any other
    substance.  If it could be used to power the US space shuttle system,
    engineers could pack the energyequivalent of the liquid and solid
    propellent into a mass the size of a sugar cube.
    
    Antimatter is just like ordinary matter, except that certain
    properties, such as electric charge, are reversed.  British physicist
    Paul Dirac introduced the concept six decades ago when he brought
    the then young theory of quantum physics into line with Einstein's
    theory of special relativity.  Since then, physicists have found
    it in cosmic rays and created it in particle accelerators.  There
    is now no doubt that they could produce whole atoms of antimatter
    - for example, antihydrogen.  The challenge is to learn how to make
    it, store it indefinitely, and control it in safe and economically
    practical ways.
    
    Since antimatter can't touch container walls, physicists at accelerator
    laboratories control it with magnetic forces inside large evacuated
    rings.  Practical applications need more compact, efficient methods.
    Concepts now under investigation include using laser light as well
    as electromagnetic fields to help manipulate antimatter - perhaps
    in the form of antihydrogen ice - within vacuum containers.
    
    The European Laboratory for Particle Physics (CERN), in reviewing
    such propsects last year, observed that it still "would be pure
    science fiction to try to stock even a millionth of a gram [of
    antihydrogen] in volumes that were both feasible and transportable."
    
    Robert L. Forward, who recently retired as senior scientist at Hughes
    Research Laboratories, and science writer Joel Davis take a more
    visionary approach in their new book, "Mirror Matter" (New York:
    John Wiley & Sons), saying: "No physical laws will be violated.
    Mirror matter, in some form, will someday be made and stored in
    enough quantity to produce megawatts and gigawatts of prime power
    and propulsion needed for space travel."
    
    One may be skeptical about the timing.  But it's no longer a prospect
    to giggle at.

    	For those of you interested in reading about the actual
    possibilities of antimatter (mirror matter) being used to propel
    future interplanetary and interstellar spaceships, 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 those both involved and just studying future 
    space travel plans, as it discusses antimatter physics and its use as 
    a spacecraft fuel in a manner which neither insults nor overwhelms the 
    average reader's intelligence.  The authors' consensus is that 
    antimatter could make a wonderfully fast and efficient interplanetary 
    and sublight starship power source someday, but that using it for 
    faster-than-light (FTL) propulsion is impossible regardless, based 
    on the scientific knowledge we currently have in this area.
 
        Forward also publishes MIRROR MATTER, a newsletter which is 
    mailed out every few months detailing the latest advancements in 
    antimatter physics and technology.  The address for receiving MIRROR 
    MATTER can be found in the book.
                                                            
    	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 devotes itself to numerous currently SF-type ideas 
    on future science and technology.
    
    	Larry
    

    Anti-matter is  V E R Y  easy to contain.  As long as we stick to
    sub-atomic particles with the property of electric charge(positrons/anti-
    electrons, negatrons/anti-protons) all we have to do is make sure
    that our containment vessel is charged with a like charge. Since like
    charges repel, positrons would be repelled by the walls of a positively
    charged vessel, and negatrons/anti-protons would avoid contact with a
    negatively charged vessel.  Since we don't have a 100% efficient
    insulator, a system would have to be in place to replenish any charge
    lost by the vessel to insulator leakage.  But the replenishment of
    lost charge would not require nearly as much energy as constantly
    generating a high powered magnetic field for containment.
    
    So much for the containment problem, now for the starship.  The base
    of the ship would be a large (relative to the ship) parabolic mirror
    backed by a heavy duty radiation shield with heat exchange coils
    imbedded in the rad-shield.  The circumference of the mirror would
    have exit nozzles for rear firing charged partical beams mounted
    around it.  Every other beam would be a proton partical beam, and
    every other beam would be a negatron partical beam.  All beams would
    be focused on a common center point some optimum distance behind the
    ship directly below the center of the mirror.  Causing the beams to
    converge at the focal point will not be a problem as they are made
    up of equal numbers of unlike charges and will converge due to
    electrostatic attraction.  When the matter and anti-matter beams
    converge, mutual anilation will result, causing the equivalent of
    a very small star to be formed directly behind ship.   Radiant
    pressure from the pseudo-star will then propel our starship along
    its way.  Of course all this radiation is going to really heat up
    the mirror and the rad-shield behind it, which will provide lots
    of heat to the heat exchange coils imbedded in the rad-shield.
    The heat exchange coils will power steam turbin generators which
    will supply all the electrical needs of the starship. The steam
    would then pass through heat sink fins protruding from the main
    body of the ship, be condensed back into water and pumped back
    into the boilers.  The cooling fins will work because they will
    be in the shadow of the rad-shield, in interplanetary space they
    will be very cold, in interstellar space they would be very, V E R Y
    cold.
    
    The partical beam accelerators would be fed by negatively charged
    containment vessels for the negatrons, and positively charged
    containment vessels for the protons.
    
    Since this system yields large supplies of heat and electricity
    life support systems should be simple to come up with.
    
    With a constant one gee thrust, you would have earth normal gravity
    aboard ship, and it would take only about six months to get very
    close to the speed of light (99.5c ?).  A round trip to any star
    we might want to visit in the near future should take no more than
    about two years ships relative time, and no more than 25 to 30 Yr
    earth relative time (I'm guesstimating but I bet I'm real close).
    
    Hope I've given you something to think about.  Please try to shoot
    me down, as this it the way we discover new truths.
    
    Thanks a big bunch,
    
    John (Why do people make things so complicated) Layne
     
    

    Take a look at the electric field inside your containment vessel.
    I don't think it is what you think it is. If your containment system
    worked, then Van DeGraf generators would not.
                                          Bill

    You speak of the fact that the inside of the containment vessel
    is field free no matter how it is charged - Faraday did the
    experiment to prove this.
    
    Chuck

Correct. This assumes that the surface is a conductor or that the deposited
charges on the containment vessel(if bound) are evenly distributed about the
surface. This was the intent of note .8 I am sure. The only electric field
inside the vessel would be do to the charges placed inside it. This would
produce a repulsive force on the charges. The antimatter will then be 
deposited on the inside of the containment vessel with explosive results.
                                               Bill

>    Please try to shoot
>    me down, as this it the way we discover new truths.

Ok, howzabout this? I had heard that the big stumbling block for
matter/antimatter drives was the fact that most of their energy is released as
gamma rays. This means it would mostly pass right through the mirror, I assume
the radiation shield would be large/dense enough to absorb it (which means it
would get very radioactive very fast).
-Tom R.

    I was just struck by the thought that X-ray and gamma ray optics
    are designed as grazing angle optics - efficiency is higher.  The
    problem is to design grazing angle optics to get the gamma rays
    all going more or less one direction.  Something of the sort might
    be possible.  The gamma rays will give you momentum just as well
    as hurling rubbish in an ordinary rocket.
    
    Chuck 

    Ooops!  I forgot about the good Dr.Faraday's Exp. REF.8.  I can only
    say that I need more rest.  As I recall Faraday's Exp. delt with a 
    negatively charged copper sphere with an opening to give access to the
    inside.  When Faraday charged the sphere with an excess of electrons,
    the electrons repeled each other and collected on the outside of the
    sphere as far apart as possable.  Thier was no charge inside because
    the charge moved to the outside.  I have no problem with this (except
    forgetting it sometimes).  But what about the reverse case where
    electrons are 'drained from' rather than 'added to' the sphere.
    It would seem to me that since the positive charges left behind
    cannot move, the inside and outside of the sphere would have to
    show positive charge.  If this is the case, we might still use pos+
    charged containment vessels for positrons/anti-electrons at least.
    
    Gamma-rays would be absorbed by the rad-shield where they would show
    up as heat and momentum.  This would be true of any energy that wasn't
    reflected by some layer of the mirror.  More heat equals more electricity
    and momentum is what we want to begin with.  
    
    Before I get into alternate containment vessels will someone please
    explain why a positively charged vessel wont work, given that positive
    charges bound up in a solid can't move.
    
    thanks
    
    John (The humble) Layne
    

    
    Re .14:
    
    I am afraid that the electric field inside a conductive sphere is always
    zero no matter how much the sphere is charged.  The explanation
    goes something like this:
    
    	There is a point charge Q inside the sphere and a tiny sliver S of
    	the sphere and its projection S' around the point Q back onto the
    	sphere.  Because of the geometry, the area of s is proportional
    	to the square of the distance from the point charge q.  Likewise,
    	the area of s' is proportional to the square of the distance
    	from q.  Supposing that the sphere is uniformly charged, the
    	electrical force of S on Q is equal and opposite to that of S'
    	on Q since the electrical forces on Q are proportional to the 
    	square of the distances (charges on S and S')  as well as to the
    	inverse of the square of the distances.  Thus, there is not net
    	electrical force on the point charge Q, which means that there is
    	no electric field inside a sphere.
    
    Masamichi
    
    
    

    Re .15:
    
    Can this argument be extended to containers of non-spherical shape?
    With what results?  Is the field always zero everywhere inside ANY
    closed container?  If not, are there general and/or useful results
    on how the shape of the container affects the field?  What about
    containers with varying, rather than constant, charge distribution
    (on the surface of the container)?
    
    
    Jeff

    
    RE .16:
    
    I'm affraid RE .15 shows that any further consideration of 'closed
    electrostatic containment' is of no value to us here. I believe it 
    would also rule out a very short cylinder with a very large diameter
    (very large relative to its height), and no top or bottom. My idea
    was that given a charged cylinder, a group of like charged particals
    could be repeled twords the center of the cylinder as they ordited
    around its center just inside the cylinder walls.  Magnetic fields
    would be used to prevent the ring of charged particles from moving
    up and down or to store kinetic energy by accelerating the charged
    particles.    Since acceleration would cause the particles to come
    closer and closer  to the cylinder walls as their speed increased,
    there would be a limit to the amount of kinetic energy which could
    be stored this way,  but if the containment vessel is used to feed
    a 'linear charged particle accelerator'(LCPA) this store of kinetic
    energy is most welcome, since it decreases the energy requirements
    of the LCPA.  Its a nice thought but it seems   RE .15  shows that
    there would be no field inside even a  'positively'  charged 'open'
    cylinder such as the one I just described. I mention it in the hope
    that I am incorrect in this conclusion.  I hope someone more learned
    in this field than I, will please address this issue. 
    
    Now if we take this same cylinder and use magnetic fields to hold
    the charged particles in orbit and accelerate them, then we use a
    charged plate on top and bottom to keep the CP ring from moving
    up or down, I believe we might have something that will work based
    on accepted theory. I believe this sort of containment vessel would
    be a type of cyclotron, designed to achieve a somewhat different
    objective, with the emphasis being on containment rather than
    acceleration.  OK come and get me if you can.
    
    The only remaining objection to my star ship design seems to be
    that I haven't worked out a proper Anti-matter containment system.
    I hope this note answers this (last?) objection.  How about a 
    little more input about the rest of the ship.  Other objections ?
    
    Thanks sincerely,
    
    John (still at it !) Layne
    
    

    
    RE: World Book Encyclopedia; Gamma Rays
    
    Gamma Ray is an electromagnetic radiation of the same character
    as an X Ray, but it has a much shorter wave length. Members of the
    uranium-radium series of radioactive elements give off gamma rays
    when they disintegrate to form new elements. When a nucleus emits
    a gamma ray it remains unchanged - all that happens is that it loses
    a certian amount of energy. But it gives a very penetrating ray
    if it loses a very large amount of energy, say, 5 million electron
    volts(Mev). A sheet of iron about 1 inch thick will stop 50% of
    gamma rays of this energy. But it takes about 9 inches of water
    to equal the absorbing ability of 1 inch of iron. A heavy element
    such as lead is very good for stopping gamma rays. About 1/2IN 
    of lead equals 1 inch of iron in absorbing power.
    
    Gamma rays lose energy by colliding with atoms in passing through
    water, air, lead, iron, or any other material. High-energy gamma
    rays may create matter by completely disappearing and forming an
    electron/anti-electron pair. The positive anti-electron is called
    a positron. This creative process is the opposite of what occurs
    when the particle called a positron dies or is destroyed to form
    two gamma rays.
    
    This seems to be the part of this article which applies here.
    
    I assume the gamma rays in question would be this "high-energy"
    sort that would produce positrons.  I assume this is what was
    ment by the statement in an earlier note that the Rad-shield
    would become radioactive very fast. I think we all agree that
    a starship is going to be rather large.  The Rad-shield in this
    design is going to have to be VERY heavy duty (No surprise here).
    Maybe something on the order of one meter(two maybe?) thick
    slab of alloy made up of 50% lead (shielding) and 50% aluminum
    (to speed heat transfer). I have read that such alloys can be
    made under zero-g conditions.  This ship is NOT going to have
    ANY shortage of electricity if we can design heat transfer
    coils in the Rad-shield that can handle this much heat.
    It looks like this Rad-shield will have to be treated like a 
    reactor core analog, which means the ground work for the
    ships onboard power system has already been done.
    
    more later
    
    John

    re: .17 by WALLAC::LAYNE
    
    Ok, Electrostatics are out.
    
    How about Electromagnetics (eg Torus) - a doughnut shaped magnetic
    field, with the charged negitrons running around in circles.
    you need a decent electricity supply, and you're away. even easier
    with the new superconductors.
    just make durn sure that the power supply's uninteruptable.
so: John Layne is , i think, on the right track.
    as for firing a neutron/proton beam to intercept the negitron beam,why
    bother ? - mass of any sort will do.

    the problems would be :
    Waste heat;
    radiation,
    drive control,
    
    
    and as for .995 of the speed of light ! well, even in deep space,
    someone calculated that there is 1 molecule if hydrogen per cubic
    metre. -
    at those speeds, the Hydrogen molecule would be not nice to hit,
    - don't know what would happen, but i suspect it would be a "cosmic
    ray" or some form of EM Wave, at very short wavelength. Unhealthy
    
    at .995c, a target 1m^3 would impact with approx 2.9 x 10^8 molecules
    - each at about 3x10^-27 Kg. - every second.
    using Newton's laws, energy of a moving body is 1/2 Mv^2
    = in region of .1 watts. - not a lot, I agree, but might have "unwanted
    effects"
    ( someone's going to say that newton doesn't apply, as we're reaching
    relativistic speeds)
    
    
I don't know how to navigate at relativistic speeds - anyone have any
    ideas????
    
    P.s. wasn't there a design project about throwing "H" bombs under
    a hemispherical shield????

    	The hydrogen bomb starship is called ORION, and is discussed
    in Topic 467.
    
    	Larry
    

    
    RE: .19 by FOOT::OTTEN
    
    > How about Electromagnetics (eg Torus)...
    > ...even easier with new superconductors.
    
    This is the sort of thing I ment when I said we need a small modified
    cyclotron.  The charged particles traped in the containment Torus
    could be accelerated to relativistic speeds, by superconducting magnets,
    as they circled the inside of the Torus.  This means that they would
    already be moving close to the speed of light before being injected
    into the linear charged particle accelerator, which would also be
    superconducting. Since we will have a BUNCH of electricity, the combined
    acceleration of the TORUS and the LCPA should cause the particles to
    be fired rearward with a speed VERY close to the speed of light.
    The charged particles are also reaction mass, but F=1/2 Mv^2 does
    not apply because this reaction mass has been accelerated to relativistic
    speed. I will have to look up the correct formula, but I recall that
    it yields a MUCH higher value than F=1/2 Mv^2 this close to the speed
    of light, because of the relativistic increase of the mass of the
    reaction mass relative to the mass of the ship.  I believe that the
    thrust produced by the LCPA will represent a substantial portion of
    the total thrust of the system.
    
    > Just make darn sure that the power supply's uninteruptable.
    
    Since the magnetic containment field in the Torus can be constant( it
    need only be powerful enough to trap the maximum number of particals
    you wish to store in the Torus) I see no reason why permanent magnetism
    could not be used to perform this function, in which case it would
    be uninteruptable.
    
    Thank you all for your interest !
    
    More later ! for sure !
    
    John Layne
    

    Sorry, but I think that permenant magnetism is a no-no. The strength
    of a permenant magnetic field is low (with present technology) compared
    with that of an electromagnetic field. Also, "permanance" is relative
    - I wouldn't trust a perm. magnet to keep the antimatter stuff in.
    
    Anyhow - enough about engines.
    
    How about a "biosphere" for waste recycling - may mean that the
    astronauts have to be buddist monks, but i'm sure we can find some
    from somewhere.
    
    Navigation.
    Trying to navigate at .95 c poses it's own problems, too. Stopping
    wouldn't be fun for the "target" planet, either.
    
    
    Back to work......
    
    d
    

    re .17 and so on.  It is worth noting that both "weak focusing"
    (like the Bevatron in Berkeley) and "strong focusing" (like the
    200 GeV machine near Chicago) synchrotrons use only magnetic fields
    for containment.  Particle storage rings are the same.
    
    About reaction mass - really you want to work with momentum in your
    equations rather than mass.  At relativistic speeds, momentum increases
    without a "corresponding" change in speed.  In any case, momentum
    is still conserved.
    
    Chuck

    Without sounding too much like an ignoramus, why are most if not
    all propulsion system theory/design talks concerned with a system
    that throws matter behind you? Is it just possible, that we are
    missing the point? Could we theorize/design a system that we pull
    towards something else?

Actually when a space craft is approaching a planet or a star, you are
doing just that. The force you are using is gravity.
                                         Bill

    What else could we use? - a piece of string, perhaps.
    
    Seriously, though, there has been some speculation (mainly in SF)
    of a "drive" that 'pulls' on "the Fabric of the Space-time continuum"
    
    also some that actually generate a "warp" in space-time (ie a gravity
    well) in front of the craft, that it continuously "falls" into.
    
    You'd have to have a disk-shapes craft, going base-first , otherwise
    the tidal effects would be worrysome.
    
    Of course, an advantage of this would be that you'd be able to
    accelerate extremely fast, as you'd be in "free-fall" the whole
    time.
    
    Um.
    
    now where've i left my skyhook?
    
    David

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]

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
 

    	Are we missing something here.  What process produces an antimatter
    particle in our dimensional universe without affecting an alternate
    demensional universe?  I'm not talking 3 headed monsters here, what I
    am refering to is the production of a particle which does not exist 
    in our normal space.  If in fact this is what is happening, then any
    addition or change in energy/mass in this space would also produce some
    gravitational effect, albeit quite small, probably not measureable in
    the quantities produced in the lab.  It's annihalation should also
    produce a minute gravitational change, as both particles (with a
    definite measurable mass) will produce pure energy.  By the same
    reasoning, the energy produced would have to be split between the two
    normal space dimensions for these particles, otherwise additional
    energy would be added to our normal space, altering the structure of
    our universe.  Besides the associated bang, heat and light that would 
    be part of the annihalation process, would also be changes in
    gravitational fields.  My point being, would we not be better off
    exploring the use of gravitational field modulation as a propulsion
    method, as opposed to the basic reaction type of propulsion sytems we 
    now envision.  I realize I'm not talking science facts here, I'm just
    attempting to stimulate conversation along another avenue.  Sometimes 
    the strangest concepts have some merit.
    
    
    Regards
    Rod
     

    2
E=mc

Still holds true. The antimatter is created out of high energy collisions and
the conservation laws still apply. The energy released through annilation is
accounted for in the masses consumed. It's just VERY efficient 8^)

Yeah, there's some minute grav effects but the blast from the energy release
would somewhat offset them 8^)

    Agreed as to small gravitational effects, however...Gravitational
    fields are in theory infinite, as opposed to an explosion.  If a
    controlled reaction could be maintained without causing total
    destruction of all surrounding material, then perhaps gravitational
    effects could be a factor.  Another point to ponder.  Does
    gravitational fields as we now define them behave according to
    classic physics.  In other words, If the sun was to disappear tomorrow,
    would the gravitational ripples in space move outward at the speed of
    light.  In other words does gravity as we know it propogate it's
    influence at the speed of light?
    	This brings to mind another pet peeve of mine with regards to the
    speed of light.  Why is the speed of light 186,000 miles per hour?
    Why not 300,000 miles per hour, or 3000 miles per hour for that matter?
    What is the controlling mechanism that limits light to the standard
    defined speed in a vaccuum of 186,000 miles per hour?  What is the
    effect of gravity on the speed of light?  We now theorize that Gravity
    in the extreme (black holes) are capable of infuencing the path of
    light.  Does it also affect it's velocity?  If so then is the speed of
    light that we presently hold as fixed, change for a given gravitational
    field change.  Now the effects would be hard to observe in our solar
    system, due to the massive field produced by the sun, and collectively
    by the solar system as a whole.  And in fact the Milky Way exerts a
    gravitational influence on all of the above.  What is the speed of
    light once you are between gravitational infuences. (ie. half way
    between here and the next star, or half way between galaxies.) 
    Something is limiting light, and it's not the math in the equation,
    there is another factor.  
    
    Regards
    Rod

    re .32
    
    I believe that "gravity" propagates at the speed of light.
    
    Current physics would hold that the speed of light is constant (.).
    The presence of a gravitational field would not affect that.
    
    Matter/AntiMatter creation and annihilation does not to my knowledge
    make any difference to the gravitational field because energy interacts
    gravitationally to the same degree that the equivalent (E=mc�) mass would.
    
    As to why the speed of light is what it is...that's too deep for me. I
    imagine you could invoke the Anthropic Principle but that isn't really
    an explanation as such.
    
    re .30
    
    I didn't quite grok what you were saying. By all means speculate though.
    
    There is a common misconception that anti-matter is somehow special.
    The term anti-matter is probably the cause of this. To the best of our
    knowledge anti-matter behaves exactly like matter in respect of all
    currently formulated theories. (There is a "model" oft-repeated in
    which an anti-particle is treated as the particle but travelling
    backwards in time. This is valid to the extent that observations may
    not be able to distinguish the two interpretations but this is not an
    actual suggestion that anti-particles really do travel backwards in
    time whatever "really" means.)

  If gravity 'propogates' at the speed of light, then 'ripples' (gravity waves)
should exist. These have ben looked for, but not yet definitely found. An atomic
explosion should produce them; however, they are very weak, and tend to be lost
among the other rather more dramatic effects.

  Light (or more properly, electromagnetic radiation) loses energy when climbing
out of a gravitational field just the same as matter does. The difference is
that matter loses kinetic energy by slowing down; the speed of light is constant,
so the photons lose energy by being redshifted. In the case of a black hole,
which has an escape velocity greater than the speed of light, the photons are
effectively redshifted to an infinite wavelength. It is not in principle possible
to tell the difference between redshift caused by motion away from the observer
(Doppler effect) and gravitational redshift by just looking at the photons.

  As to WHY the speed of light is what it is, I don't think we can tell that
any more than we can tell why other constants have particular values. They just
do. We can speculate on what the Universe might be like if any of these
fundamental values were different. In many (possibly nearly all) cases, if 
they were changed more than marginally, the Universe would be so radically
different that we would not be here to observe it. The significance of this is
a matter for philosophical and theological debate.

Ken

    re.32 "Why 3.0 x 10^8 m/s ?"
    
    Me too, I often wondered about the mechanism involved, how can
    an electron so easily capture or produce photons, with different
    frequencies/energies but always at the same velocity !!! !!! !!!
    
    Not only that, but in general what happens to the 4 forces inside
    particles. Acording to the regular mathematical formulas the 
    forces go to infinity as the distance to the center aproches 
    zero ... clearly not true, but it just goes to show that we need
    to find out and quantify what exactly goes on inside particles.
    
    Only then will we be able to produce and control such things as 
    anti-matter in the quantities and ways we need for space ships
    and other things.
    
    This reminds me, I just saw an article saying that Fermilab had
    at long last found evidence of top-quarks. (or almost there still
    is one change in 400 that they maybe wrong...)
    
    Now lets hope that this discovery will "eventualy" lead to
    something usefull such as economic anti-matter production.
    I got to admit that personally I am still a bit in the dark as
    far as quarks are concerned ... combined this or that way they
    make up ordinary particles, but what I want to know is how 
    that helps us manipulate things in order to do the things we
    want ???
    
    Gil 
    

    re .34
    
    Or strengthening the last bit, more than "we would not be here to
    observe it" but rather "we could not be here to observe it". For some
    changes to physical constants or laws, the big bang might never have
    happened, or matter might not be possible or, less radically, galaxies/stars
    /planets/life might not be possible to form.
    
    re .35
    
>    Me too, I often wondered about the mechanism involved, how can
>    an electron so easily capture or produce photons, with different
>    frequencies/energies but always at the same velocity !!! !!! !!!
    
    One way of looking at it is that light as a wave phenomenon has a speed
    of propagation that depends in some way on the nature of the universe
    even though there is no medium through which it propagates. Viewed as a
    wave, light is but a disturbance in the electric and magnetic fields. It is
    then not really surprising that the speed is independent of the frequency.
    I agree it is harder to reconcile intuitively a particle model with the
    constancy of the speed of light. Such is duality...

You wouldn't happen to be forgetting that gravity is an inverse square effect so
the miniscule effect is lost at measurable distances (even though the effect
NEVER truely reaches zero at any distance...)

    I probably posed a trick question.  The speed of light is a factor of
    the refractive index of the medium.  This is why the speed is 3.0 x
    10^8 in a vacuum, and slightly less for other mediums.  Now bearing
    this in mind, theoretically a true vacuum contains nothing....
    ...except it is influenced by fields ie. magnetic, electrical and
    gravitational.  We have a reasonable understanding of magnetic and
    electrical fields, and for the most part could produce a true vacuum in
    space and isolating the vacuum from magnetic and electrical fields by
    various methods (location, shielding etc.)  The one force which we know
    little about, and which although relatively week seems to propogate
    itself to infinity is gravity.  Since we theorize (supported by
    observation) that strong gravitational fields do influence light, it is 
    conceivable that this influence is universal.  However gravitational
    field strength is not.  Is there a point in space where the
    gravitational field is at it's weakest, and if so what effect will
    this have on light.  This is mere speculation, but maybe we can
    generate some discussions around this, including a method of proving
    this.  One thought I have is if gravity can effect the speed of light,
    then the voyager spacecraft that is now leaving our solar system, may
    be able to shed some light (no pun intended) on this.  In particular,
    Voyagers on board clock will have been calibrated prior to departure. 
    Assuming that the clock has kept it's accuracy this long, and taking
    into account relativistic time changes, does the math work out.  In
    other words, is there a discrepency in the calculated and actual time
    of the onboard clock.  If for instance the speed of light was even
    slightly different once the craft has escaped the major influence of
    our solar systems gravitational field, then this would show up in an
    unpredicted time change of the onboard clock.
    
    Regards
    Rod 

These questions would probably get more discussion in decwet::physics

many of us so inclined people read both...

    .38
    
    Good point, I will extract the major points made by everyone on this,
    and enter it into a note in Physics.  Kind of short for time this a.m.
    but will try to get this done before the end of the day
    
    
    Regards
    Rod

I just read this string, the answer will almost certainly be that VOYAGER's 
velocity is so slow (relative to the speed of light) that any such variation 
as may exist would probably be much to small to measure.

	John Travell.

    re .41
    
    I think the question re Voyager was whether in its current position far
    from the Sun it could be used to detect dependence of the speed of
    light on the local gravitational field. Most likely though we would be
    involved in the experiment and any signal reaching us travels through
    regions of space with a stronger g-field. Perhaps the Voyagers or Pioneers
    could talk to each other.
    
    On the surface this seems reasonable but experimental design would be
    tricky. We usually measure round trip time, assume a constant speed of
    light and use that to compute the distance. We can measure time very
    very accurately. Somehow we would have to establish the distance
    independently. Account would have to be taken of the fact that the
    probes are moving. How fast? Well most of our techniques for answering
    that implicitly assume constancy of the speed of light. Catch 22.
    Furthermore, since a gravitational field is supposed to "bend" light (i.e.
    change the "distance") it gets trickier. Ideas welcome.
    
    (Voyager's speed is quite high enough as a fraction of the speed of
    light for first order effects to be measurable but its speed was not
    the point being made. I'm not sure about second order effects.) 
    
    re .?
    
    In an earlier note I stated that the speed of light was a constant. As
    was implicitly corrected by a later note, I should have said "speed of
    light in a vacuum". I believe Quantum ElectroDynamics (QED) provides
    some insight into why the speed of light in a medium is different.
    Furthermore I have a vague recollection that QED makes some interesting
    predictions about the speed of light in a vacuum that is in a very
    confined space and that those predictions actually contradict my
    statement that the speed of light in a vacuum is a constant. Thus it
    could be said that while there is no known experiment or theory that
    predicts dependence of the speed of light on the gravitational field, the
    speed of light could be said to depend on the electromagnetic field.

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-