RE: starship-design: Modular Ship Design

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

Kelly,

> -----Original Message-----
> Actually I think the hab centrafuge ring makes more sence.  After
> all the ship
> will have to spend its time at varing accelerations as it burns
> off fuel, and
> zero G as it floats in the target system.  These can't be delt
> with by a fixed
> hab floor no mater how much you flip it.

Granted, once you get there you will probably still have to spin the hab
ring anyway.

> A lithium block can be cut and pressed into pellets, but a mile
> long tank of
> pellets would be a serious structural problem under acceleration.

Probably true.

> You missed the part of my statement about fuel constraint.  A
> given weight of
> fuel, only has the energy to accelerate the ship to a given delta-V.  It
> doesn't make much difference (speed wise) if it burns all the
> fuel quickly, or
> slowly.  So I figure at 1 g my fusion systems could get you about
> 4-5 months of total thrust.

No I didn't miss it. I wasn't holding the mass of the fuel constant, I was
adding MORE fuel to compensate which is whay I said it required more engine
since adding fuel increases vehicle mass, in order to maintain a constant
acceleration you have to increase thrust, which means you consume more fuel,
etc. but it does work out in the math.

> If we didn't have the fuel/delta-V limitation then a continuous
> 1-G burn for
> the flight would be great. In about a year you'ld be presses
> light speed, and
> Alph-C would be under 3 years away ship time.

BINGO! That was my point.

> But we don't have that kind of power.

It isn't about power, it is about fuel.

> Given we haven't come up with anyway other then fusion that we
> could really
> decelerate into or out of the target system.  (I'm very dubious
> about anti-
> matter, and the limited details of its control and use I've heard.)  We're
> limited by the credable delta-V a fusion powered drive can give us.

Again, it isn't about power, it is fuel, delta v is NOT acceleration, which
is a limit of the engine. delta v is how long you can MAINTAIN that
acceleration which is a function of how much fuel you can burn. The thing to
remember is that we CAN get there today, at an outrageous fuel cost, using
nothing more than fusion engines. We might be able to get there tomorrow, at
a lower fuel cost with a hybrid engine.

Lee Parker

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What happens if a big asteroid hits the Earth?  Judging from realistic
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