Antimatter propulsion

"Dr. O" wrote in
:

I'm personally not a fan of antimatter propulsion at this time as
there's no safeguarding technology for when the launch or a component
during flight fails. Even milligrams of antimatter can result in an
explosion that can destroy a sizeable portion of the planet.

Where'd you learn that nonsense? Per Einstein, E=m*c^2, so energy per unit
mass E/m = c^2 = (3e8 m/s)^2 = 9e16 m^2/s^2 = 9e16 J/kg, so a 100%
efficient 1 kg matter/1 kg antimatter reaction would release 1.8e17 J.
Since one megaton of TNT releases 4.2e15 J, that's equivalent to a 43
megaton bomb. That's a citybuster bomb, but not nearly big enough to
"destroy a sizeable portion of the planet." And a milligram would produce
an explosion a million times smaller.

--
JRF

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I'm personally not a fan of antimatter propulsion at this time as there's
no safeguarding technology for when the launch or a component during
flight fails. Even milligrams of antimatter can result in an explosion
that can destroy a sizeable portion of the planet.

Utter rubbish. It would take more than a few milligrams to destroy a part of
earth.....

The only way to
encapsulate antimatter at this time is through magnetic containment, which
needs power and a complex control system. If these fail during launch or
at any time during the flight the result will be an explosion which dwarfs
that of a hydrogen bomb.

IIRC there is now a stable system for transport of antimatter using
permanent magnets that doesn't require power. In any case antimatter could
be produced in space, for use in space so as not to require launch from
earth.

Let's not go this route untill we get these things sorted out.

Duh! Thanks,

David

I'm personally not a fan of antimatter propulsion at this time as there's
no safeguarding technology for when the launch or a component during
flight fails. Even milligrams of antimatter can result in an explosion
that can destroy a sizeable portion of the planet.

Utter rubbish. It would take more than a few milligrams to destroy a part of
earth.....

The only way to
encapsulate antimatter at this time is through magnetic containment, which
needs power and a complex control system. If these fail during launch or
at any time during the flight the result will be an explosion which dwarfs
that of a hydrogen bomb.

IIRC there is now a stable system for transport of antimatter using
permanent magnets that doesn't require power. In any case antimatter could
be produced in space, for use in space so as not to require launch from
earth.

Let's not go this route untill we get these things sorted out.

Duh! Thanks,

David

"Dr. O" wrote in message ...

Even milligrams of antimatter can result in an explosion that can
destroy a sizeable portion of the planet.

The dino-killing asteroid that hit at Chicxulub, Mexico, was
equivalent to 100 million megatons of TNT. To get that yield out of
anti-matter, you would need ~2000 metric tons of anti-matter.

Now, if by "sizable portion of the planet", you mean "football field"
areas or "a couple of city blocks," milligrams of anti-matter can
certainly manage that.

If these fail during launch or at any time
during the flight the result will be an explosion which dwarfs that of a
hydrogen bomb.

Kinda depends on the amount of anti-matter, doesn't it? A few grams of
anti-matter would be useful for low thrust deep space applications,
and would have a yield of tens of kilotons if something went wrong.
That's not so much worse than the chemical energy stored in a Saturn
V, IIRC, though the gamma ray pulse is a new twist.

Mike Miller, materials Engineer

"Dr. O" wrote in message ...

Even milligrams of antimatter can result in an explosion that can
destroy a sizeable portion of the planet.

The dino-killing asteroid that hit at Chicxulub, Mexico, was
equivalent to 100 million megatons of TNT. To get that yield out of
anti-matter, you would need ~2000 metric tons of anti-matter.

Now, if by "sizable portion of the planet", you mean "football field"
areas or "a couple of city blocks," milligrams of anti-matter can
certainly manage that.

If these fail during launch or at any time
during the flight the result will be an explosion which dwarfs that of a
hydrogen bomb.

Kinda depends on the amount of anti-matter, doesn't it? A few grams of
anti-matter would be useful for low thrust deep space applications,
and would have a yield of tens of kilotons if something went wrong.
That's not so much worse than the chemical energy stored in a Saturn
V, IIRC, though the gamma ray pulse is a new twist.

Mike Miller, materials Engineer

In article , Mike
Miller writes
"Dr. O" wrote in message news:3fe199
...

Even milligrams of antimatter can result in an explosion that can
destroy a sizeable portion of the planet.

The dino-killing asteroid that hit at Chicxulub, Mexico, was
equivalent to 100 million megatons of TNT. To get that yield out of
anti-matter, you would need ~2000 metric tons of anti-matter.

Now, if by "sizable portion of the planet", you mean "football field"
areas or "a couple of city blocks," milligrams of anti-matter can
certainly manage that.

I recall reading that a matter/antimatter annihilation reaction would
NOT be a catastrophic explosion, because the reaction cross section is
small (since matter is mostly empty space) and the energy release would
proceed relatively slowly. It would obviously depend on the density of
the reactants. There were also some issues about getting the reactants
mixed well enough to explode.

What's the thinking on this? I can't recall where I read about it, so I
don't know how reliable this analysis is.
--
Jonathan Griffitts
AnyWare Engineering Boulder, CO, USA

David Findlay wrote in message . au...
IIRC there is now a stable system for transport of antimatter using
permanent magnets that doesn't require power. In any case antimatter could
be produced in space, for use in space so as not to require launch from
earth.

Given the massive energy requirements for large velocities, and hence
for antimatter production, production would have to be in space.

The waste heat from producing antimatter to accelerate a 1000 ton ship
to .3c (5E21 Joules, or 160,000GW for a year) would overheat a
continent.

I recall reading that a matter/antimatter annihilation reaction would
NOT be a catastrophic explosion, because the reaction cross section is
small (since matter is mostly empty space) and the energy release would
proceed relatively slowly. It would obviously depend on the density of
the reactants. There were also some issues about getting the reactants
mixed well enough to explode.

What's the thinking on this? I can't recall where I read about it, so I
don't know how reliable this analysis is.

I actually think that antimatter in a bottle would be self isolating
to a small extent because the annihillation reactions at the walls
would heat the gas at the interface thereby reducing its density. So
if we could make enough of say anti hydrogen and we put it into a
bottle, it would release a steady amount of heat and last a relatively
long time.

Zoltan

Jonathan Griffitts wrote in message ...
I recall reading that a matter/antimatter annihilation reaction would
NOT be a catastrophic explosion, because the reaction cross section is
small (since matter is mostly empty space) and the energy release would
proceed relatively slowly. It would obviously depend on the density of
the reactants. There were also some issues about getting the reactants
mixed well enough to explode.

What's the thinking on this? I can't recall where I read about it, so I
don't know how reliable this analysis is.

This was hashed out a substantial amount over in rec.arts.sf.science a
while back (and several times, I'm sure), search google groups for
"antimatter explosion" or somesuch*.

With regard to the reaction cross-section, it almost doesn't matter
how small it is because it's a positive feedback loop when at the
scale of atoms. When you get two neutral atoms near each other
(e.g. when rebounding due to kinetic interactions in a gas) they
induce small changes in average electron density in each other which
result in an attractive force between them, these forces are called
Van Der Waals forces or London Dispersion forces. They are the reason
why butter is solid and oil is not, the molecules of butter can pack
closer together so that the atoms of the molecules can experience
higher Van Der Waals attractive forces, and thus stay solid at higher
temperatures. Anywho, the same thing will occur with anti-atoms,
except without limit. In normal atoms there is a limit to Van Der
Waals forces because as you bring atoms closer together eventually
they
start penetrating through each others' electron shells, which
normally neutralize the charge of the nucleus. With two atoms deep
within each others' electron shells there will be a strong repulsive
force due to the, unshieled, charges on the nuclei. But in the case
of
one anti-atom and one atom the attractive force simply increases as
the
separation decreases. Unshielding the nuclei from the electrons
and/or
positrons will reveal opposite charges that attract one another.
Furthermore, the electron "clouds" around the atoms will interact in a
somewhat similar fashion, at somewhat far distances Van Der Waals
forces will induce a greater density of electronic/positronic charge
at
the "leading edges" of the atoms (the parts of the atoms which are
toward each other), and thus a higher probability of electron or
positron presence and, when the atom / anti-atom approach close
enough,
a higher probability of electron / positron encounter and
annihilation.
Most aspects of this process are self-reinforcing. Van Der Waals
forces
can bring the atoms close together, annihilation of electrons and
positrons will result in an "ionic bond" of sorts which simply
increases the attractive force between atom and anti-atom. The only
likely thing that could throw the mix apart would be contact between
the nuclei, which would probably send the fragments off (positive and
negative) at high kinetic energies. Nevertheless, a charged nuclear
fragment won't get far (note the penetration depths and whatnot of
alpha particles or protons in air, or solid, for exaple).

The short of it is that if you have a lump of anti-matter and it's in
contact with the atmosphere it's going to explode, rapidly. The
annihilation of just the tiny amount of air which contacts the
antimatter physically in a fraction of a second will release a
substantial amount of heat, if even a small portion of that heat is
deposited in the neutral/inert anti-matter lump then it will take only
a very small amount of time before the anti-matter is vaporized, at
which point it begins mixing with the air. Subsequent annihilations
with air molecules, mean free path/time in air at STP is ~nanometers /
nanoseconds, as the gaseous anti-matter becomes hotter and hotter,
accelerate the process until the air/anti-gas cloud expands
sufficiently so that all of the anti-matter comes into contact with
and
annihilates with air molecules. This process is estimated to take
microseconds or less for macroscopic sized objects. After the first
round of annihilation has completed the result will be an enormous
ball
of superheated gas and plasma and energetic particle fragments, much
like the detonation of a nuclear weapon, depending on energy release.

Anti-matter annihilation is unlikely to generate as much fallout as
even the cleaner brands of nuclear weapons, in my opinion, but Paul F.
Dietz has convinced me that there's a reasonable chance for a
substantial amount of fallout due to activation of in-situ materials
by
spallation generated neutrons.


(*) It's link-o-rific:
http://www.google.com/groups?selm=TE...ps.asp.att.net

http://www.google.com/groups?threadm... ng.google.com

(Zoltan Szakaly) wrote in message . com...
I actually think that antimatter in a bottle would be self isolating
to a small extent because the annihillation reactions at the walls
would heat the gas at the interface thereby reducing its density. So
if we could make enough of say anti hydrogen and we put it into a
bottle, it would release a steady amount of heat and last a relatively
long time.

Density isn't the issue though, temperature and pressure
is. The higher the temperature and pressure the greater
"mass flux" against the walls of the container (i.e. the
more numerous the rebounds). But anti-atoms colliding
with the walls of a container made of matter atoms will
result in annihilations, which will release a heck of a
lot of energy and further accelerate the process. Also,
the heat from the annihilation reactions will come out
initially in two forms: gamma rays and high velocity
nuclei/anti-nuclei fragments. Both of these will be
more likely to deposit more heat in the *walls* of the
container than the gas itself, which may actually be a
good thing in terms of containment, but not by much.