Re: Starship design revamping

Sorry, but GURPS is wrong, and Traveller is much closer to being correct.
For the drives alone it can easily be shown that the "thousand miles to
the gallon" is correct.

First of all, there was a paragraph buried in the original rules that
gave fuel consumption as an option. I worked it out and it gave an Isp
of 600,000 for the drive. (which incidentally matches the figure given
for a "fusion drive" on a chart that NASA seems to have put in 90% of the
secondary school classrooms in the US during the 60's) Isp relates thrust
and fuel consumption as follows: Isp =thrust(in pounds)/fuel consumption
(in pounds per second). Astute readers will notice slight problems with
dimensionality in this calculation. More astute readers will realize
that this is expected when one uses the same unit for mass and force.
Anyway, to get 6 million pounds opf thrust with such a drive (same as a
Saturn V) you need 10 pound per second of fuel. This is enough to move
a 3000 ton ship at 1g. So much for 200 years of fuel...

If you want to figure it yourself, the standard rule of thumb is that a
fusion reaction converts .1% (.001) of the reaction mass into energy. So
you can figure from that how much fuel in needed to get how much energy.
This gives an lower limit for fuel consumption. It'll likely take more as
the equipment isn't going to be 100% efficient at turning the energy released
by the reaction into power or thrust, or whatever.

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