RE: starship-design: Thoughts on antimatter and fusion...

["L. Parker" <lparker@cacaphony.net>]

> Actually, I think I've said much the same thing in the past.  The
> theoretically maximally efficient reaction drive would
> convert fuel mass
> entirely to photons.  In fact, matter/antimatter reactions aren't 100%
> efficient at converting mass to photons, partly because it's
> hard to get
> a complete reaction and even if the reaction is complete not
> all of the
> reaction products are photons.
>
> I'm not expert enough at particle physics to know if there's any deep
> reason why converting a quantity of mass (as opposed to equal
> quantities
> of matter and antimatter) entirely to photons would be difficult or
> impossible.  I suspect that some of the more subtle
> conservation laws in
> particle physics may prevent 100% complete conversion.  In fact, there
> are things that probably also come into play like the charge-parity
> asymmetry which makes matter more prevalent in the universe than
> antimatter.

I'm guessing here, but besides the obvious thermodynamic problems, I believe
that there is also a chaotic component of most reactions that make them
inherently inefficient.

But what I was getting at is that it may be possible once we understand the
nature of matter a little better, to simply coerce it into changing states
in an organized manner to produce nearly  one hundred percent efficient
thrust. Of course, I have no idea now how that might be done...

However, I'm still with Marc Millis on the precept that true interstellar
flight requires a "breakthrough" in propulsion physics, that reaction drives
are NOT the answer. What I just described is an evolutionary approach, not a
revolutionary approach.

 My personal favorite has always been inertia, which seems to be yielding a
few hints of being manipulable based on recent theoretical work. One can
always hope, meanwhile, we keep whittling away at what we know works to make
it better...

Lee