Re: Starship design revamping

[email removed] writes:

>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.

No, it isn't. I did similar calculations for High Guard back in the bad
old days
and came to the same conclusion: the power plant/manuver drive did not use
enough fuel to account for the kinetic energy of the ship after
accellerating at
say, 1G for a month.
	The problem is that the MT manuver drives are not rockets! The fact
that they are reactionless has a fundamental effect on how much energy can be
given to the ship in the form of velocity. See below.

 [email removed] writes:

>I looked fusion up in a physics textbook and...

[lots of calculations deleted]

>This translates to about 99E12 MWatts per per kl of plant per hour or, in
>other words, 99,000,000 MW per kl of plant...

Your physics looks fine to me. The way the rules stand, fusion powerplants
are hideously inefficient. It is even worse than your calculations show,
because
you assume the hydrogen has not been enriched in deuterium in any way --
meaning that more than 99.9% of the fuel is just thrown away, or vented for
cooling, or whatever.
	The problem with the Mega-Traveller power plants and manuver
drives is very subtle. The inefficiency of the power plant is masked by the
remarkable (read: physically impossible) efficiency of the manuver drive.
Having a reactionless manuver drive not only lets you violate Newton's
3rd law (reaction for action), but conservation of energy as well! As far as I
can tell, it is impossible to have a reactionless drive without this property.

Example: Take a standard scoutship, which masses 916 tons full, has drives
that require 350 Mw to accellerate it at 2G's, and has enough fuel for a month.
Suppose it accellerates for a month in one direction. At the end of the
month, it
is travelling at 5.08E8 meters per second, giving it a kinetic energy of
1.182E23 Joules.  During that month, the drives have used 3.5E8 * 3600 * 24
* 30 = 9.072E14 Joules, giving an effective efficiency of 1,303,000,000%
(I want a drive like that for my car...)
	The energy to power the drive doesn't have to come from a fusion
plant. It could just as easily come from batteries, or lots of people
riding bicycle
generators. The fact that it usually comes from fusion plants just helps
to hide
their extravagant fuel use.
	The fundamental problem is that the manuver drive uses energy
at a constant rate, but gives the ship kinetic energy that goes up as
the square
of the time, assuming constant accelleration. This means there is NO fixed
number for drive power consumption that won't eventually start giving you
free energy, after going in one direction for long enough.  Sooooo.... if you
want your system to be consistent, you have to give up either reactionless
drives or conservation of energy. I personally favor keeping the drives,
because
they work in game terms, which is really the important part.
	The powerplant problem is more serious, because fusion plants are
used for things other than powering ship drives.  The MT fusion plant outputs
and fuel usage are lifted directly, unchanged, from Striker. This bothers me,
since it makes fusion plants not much better than fuel cells in terms of fuel
use per unit of output. Since they just took the numbers from Striker, and
made them apply to starships as well, I would prefer to go back to the
numbers from High Guard, which worked better (1 kl of fuel to power 1 kl
of plant per month at TL15, instead of 6.48 kl fuel per kl of plant as
it is now.)
If you think things are bad for starships, try designing a robot with a fusion
power source....

	Anyway, I thought people might be interested in the results I got.
Comments and error corrections welcome.

					W. Dow Rieder
				alias Capt. Kagariilian Grant

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