Spaceships and Solar Systems

Hi gang,

I wanted to thank everyone who responded to my questions about fusion
drives, etc. and, for those who are interested, pass on my general
conclusions.  I have drawn, in addition, on the work of Dean Ing,
Charles Sheffield, and Robert L. Forward for some of the technical
information; I am grateful to you people for filling in some of the
gaps they left unexplained.

I have ended up with a system that, for fusion drives, uses .5 g/sec
per ton of thrust at one gravity (i.e., acceleration of one ton of mass
at one gee).  This means that if a spacecraft is 30% fuel, it can thrust
at one gee for 600000 seconds, giving the spacecraft a terminal velocity
of 2% c, although what most ships do, since they want to be able to stop,
is to boost to about 2500 km./sec. and then coast until they need to
decelerate; about 20% of the fuel supply operates as reserves for mid-
course corrections and that kind of thing.  Matter-antimatter drives
can do about 12 times better.  This means that the best a fusion-driven
spacecraft could do, without being a multi-stage vehicle, is about 5% c
(terminal velocity; 2% c and maybe a little more if you want to be able
to stop at the end of the voyage).

What all this means is that it takes a few days to get to Mars, a bit more
than a week to get to Jupiter, and a few weeks to get to the outer planets.
If you coast for a year, you find yourself in the inner reaches of the
cometary halo.

Some people have been talking about solar system generating, etc.  One
thing I have always wondered about is why the Traveller system, especially
Megatraveller, has not assumed a space-industrialized society.  You do not
have to worry about whether or not there are Earth-like planets in a solar
system, or terraforming candidates, if you have either an asteroid belt or
gas giants with moons (and preferably both).  Instead, you built habitats
(even conservative estimates show that you could build microworlds that
could house a million people, and you have enough materials in almost every
solar system to build hundreds of thousands to millions of those habitats).

What I've ended up with are solar systems that have populations in the
hundreds of billions, living in hundreds of "archipeligos," each cluster
of habitats (usually hundreds or thousands in each one) centered around a
fair-sized airless body, like a big asteroid or the moon of a gas giant.
If you're interested in adventures that involve trade, politics, corporate
misbehavior, espionage, privateering, terrorism, and a whole range of
criminal activities, I recommend this kind of universe.  (I also
recommend Bruce Sterling's SCHIZMATRIX as source material...wonder when
Steve Jackson will get around to making a GURPs version  :)  )  My
experience running this kind of universe is that the possiblities are
pretty much limitless, even if you never travel beyond a single solar
system!

Anyway, take care, please feel free to respond to the subjects I've
brought up, and have fun.

   Mark

P.S. I would have liked to join the PBM game, it sounds interesting, but
I am simply too busy to do it this time around.  If another one is played,
I would be interested.


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