Maneuver drives

Jim Baranski writes:
>Subject: (1866) TDR reviewers, drives, etc

RE: TDR drives

>I don't like having to have three drives, but they seem to be
>necessary. Assuming that the maneuver drive is a reaction drive, you
>need some other sort of drive to land without destroying the place.
>Are there other ways to land ships?  Are there reaction drives that
>are not destructive?  Some scenarios have space ports have gravitic
>landing platforms, and scorched earth wilderness landings.  I kind of
>like that.

Well, a fusion drive flame will be *very* concentrated. Check any of
the Med Ship stories by Leinster. When landing or taking off
unassisted, the drive flame will cheerfully burn holes in the ground.
But they'll be *small* holes, compared with the size of the ship.

>I like the idea of maneuver drives being reaction drives.
>Traditionally spacecraft have always had some kind of jets or
>exhaust, even the highest TL, and I don't want to change that.
>However, it seems that the physics doesn't work, if I'm following the
>TML discussion correctly.

No, reaction drives will work just fine. It's just that some people
hear "reaction drive" and think of our current *chemical* rockets. A
fusion rocket uses 1/1500 of the fuel. So they *do have reasonable fuel
requirements, and endurance. I checked the original rules, and a type-S
scout would *still* be able to run it's manuever drive at full throttle
for a week if you assume it is a fusion rocket! Or ships should have
similar endurances.

>There are other possibilities for maneuver drives other then a
>reaction drive or a 'rabbit out of a hat' drive, and I hope we can
>decide on one that fits for TDR maneuver drives...

Excuse me? I know of *no* other alternatives.

Anyway, here are some figures that should put this in perspective.

Using the "standard" figure of 600,000 for the specific impulse of a
fusion drive, a 1000 ton *mass* ship (not 1000 tons displacement, which
is what Traveller uses) would need 864 tons of fuel to run it's drive
at 6 gs for an entire day. Or only 144 tons at 1g.

Re: unrefined fuel

Please note that since the Pioneer and Voyager missions, the outer
planet are now considered to have atmospheres of impure hydrogen. Ie
hydrogen with methane, ammonia, etc present as *impurities*. The reason
we used to think they were *mostly* methane and ammonia, is that those
are the only components that show up easily on a spectrogram of the
planet taken from Earth.

There's just enough *non* hydrogen in Jupiter's atmosphere to be a
nuisance. I think Neptune and Uranus may actually have moderate
percentages of compounds as atmospheric components at high altitudes,
but even there, you are still dealing mostly with hydrogen.

Leonard Erickson			[email removed]