Re: [FT] Railgun/Fuel Chat Results

>On Fri, 27 Nov 1998, Sean Bayan Schoonmaker wrote:
[snip]
>executive summary: fusion fuel is not an issue. reaction mass is
probably 
>an issue.
>
[snip]
>the question is, how are you going to turn this energy into thrust? if
>you have grav drives or photon drives, then it is complicated but just
>requires some machinery. if you are going to use a reaction drive (ie a
>nuclear rocket), you will need reaction mass. you may well need a lot
of
>reaction mass, depending on how fast you can accelerate it. if you go
for
>boiling water with the fusion energy and venting it into space, you
will
>need an immense amount, and will need to replenish frequently - icy
>comets, asteroids, planetary ring bodies, etc, are possible sources. if
>you are using a super-high-velocity ion drive, then your reaction mass
>needs will be more modest.

Probably the easiest way to create reaction "mass" is to use a 
very powerful lamp with a parabolic reflector. If you could find 
a way to get a high efficiency from fusion reaction to photon 
production, such a drive could actually be quite powerful. Of 
course heat is always a problem, so you would need both an 
efficient lamp and an efficient reflector at the frequencies 
you would want to deal with. Importantly, with the exception 
of the fusion part, this is possible using today's technology.

Photon may not be very "massive", but you get a lot of them for 
your money, and they tend to stick together, allowing for a 
very high density. Incidentally, the fact that photons are 
bosons makes them far more suitable for such applications than 
most other practical particles such as ionized atoms and electrons.

>Tom
>

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