Re: [gundam] Civilian Space Travel


Mark Simmons (scorpio@best.com)
Wed, 31 Mar 1999 01:27:00 -0800


Matt Hanyok asks,

>now I know you went on to explain why this was hideously resource-wasting but
>think about it: if its gonna be a one-way trip, then why the HELL hasn't
>anybody tried it yet? I'm quite sure if people actually wanted to they could
>work for a year or so, come up with some designs, build a spaceship and get
>some real progress made.

  The limiting factor with rockets of any kind is the amount of
propellant they can carry. Sustaining a constant thrust of one gee for
three and a half hours is hella resource-intensive, since you have to
push all that propellant as well. Depending on the efficiency of your
propellant, certain velocities may be simply impossible to reach - your
vessel would have to consist entirely of fuel, which is a neat trick
since the propellant tanks themselves aren't exactly massless. That's why
Saturn V rockets come in stages, so they can dump each stage's propllant
tanks and lose a bit of extra weight.

  I've loaned out all my rocket scince books, so I can't run through some
sample math for you at the moment, but the upshot is that the
constant-thrust school of space travel is simply impossible with chemical
rocket engines. Ion engines can reach much higher velocities thanks to
their higher efficiency, but they yield pretty low acceleration, so you
have to be very patient...

-- Mark

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