Bob,
You are missing the point I was making in this
thread. The argument went something like this:
P1: Look at this link for an antimatter rocket to Mars!
P2: WTF?! That quantity of antiprotons only gives you
25 megajoules of energy. Must be a small spacecraft!
P3: But it uses fission too! Maybe that's where the extra
energy is coming from.
Me: Adding fission increases the total energy output
only marginally, if at all.
Now, to address some of your points...
> Injecting a small amount of anti-protons can greatly increase the
> fission rate. For comparison, imagine adding a very short half-life
> substance (like Americium) to a longer-half-life substance (like
> plutonium). The aggregate would have a reduced half-life with only a
> tiny amount of Americium.
What injecting the antimatter *CANNOT* do is change the
criticality of a mass of fissionable material. If the assembly
is very subcritical -- as it would have to be in this case --
then any neutrons (or other energetic particles) emitted by
the antimatter-fissioned nuclei will not have much additional
effect; most will just escape. In this situation, you're going
to get roughly 1 fission per injected antiproton, so the extra
energy yield is small (10% at most, as I argued before; perhaps
less if energy is soaked up in nuclear spallation instead of
fission).
If the mass *is* critical (or supercritical) then injecting
antiprotons will also have no substantial effect; you could
start the chain reaction just as easily by adding neutrons.
It's also far too big for this scheme.
If the mass is just subcritical (so that substantial multiplication
occurs without a self-sustaining chain reaction) then it is still
too big, and you might as well make it slightly larger so that it
is truly critical.
> As you said, they create atomic fragments/isotopes that slam into other
> fissile material, thus reducing the aggregate's half-life, and
> increasing heat output.
No. Fission fragments, btw, do diddlysquat in inducing fission
in other nuclei (the Coulomb barrier is just too high); it's neutrons
that propagate a chain reaction.
> You shoot the anti-protons in while the engine is running to increase
> the heat output. Think it as the opposite of the carbon control rods
> used in reactors.
Control rods change the criticality of a reactor; injecting antimatter
does not. So this analogy is completely confused.
Control rods are also typically not made of carbon, which doesn't
absorb neutrons very well.
Paul
_______________________________________________
ERPS-list mailing list
[EMAIL PROTECTED]
http://lists.erps.org/mailman/listinfo/erps-list
