Greetings to all...
I've just recently subscribed to the list, so please forgive me if these
questions have been addressed before.
(1) I join my voice to Lucifer's in asking for equations for the Hull
Size table. I have a pretty good idea of how they SHOULD be worked out,
but some of the figures don't seem to match. For example: a rate 1 hull
has a volume of 14 m^3. Given V=4/3 x PI x r^3, this gives r = 1.495 m
or so, so the diameter ought to be 2.99 m. Taken against the 3.2 m
given in the book, this is a 7% error - too high for implementation.
What gives? Similar problems arise for the material volume
calculations; I'm assuming you take the volume of a (x) metre sphere,
and subtract it from the volume of a (x + 0.01) metre sphere, but again
it doesn't seem to work.
(2) Thermonuclear pulse drives. Fuel efficiency is not "one order of
magnitude higher". It's 0.000333 tonnes per tonne-hour of thrust,
just a little better than the fusion rocket's 0.0005 tonnes per
tonne-hour. Is there a standard erratum for this?
(3) AZHRAE. Has anyone managed to design a tech 9 AZHRAE ship that can
reach orbit? My assumptions:
* I'm using the ramjet fuel consumption figures, since the turbojet mode
isn't used for long, and the rocket mode consumes a LOT more fuel.
* I'm ignoring such things as hull mass and controls, and just working
out whether the engine can get itself into orbit, given that it has to
accelerate all the fuel it'll be using.
* I'm assuming I need 0.64 G-hours to reach orbit (p.71).
* Rather than integrate a fuel consumption equation, I'm splitting the
burn time into tenths (p.71 again).
Variables
mf = mass of fuel (tonnes; assumed HCD @ 1 tonne/m3)
me = mass of engine (tonnes)
T = thrust evolved (tonnes)
= 6 x me
FC = fuel consumption per hour
= 2 x T
= 12 x me
BT = burn time (hours)
= mf / FC
= mf / (12 x me)
So far, so good.
m* = fuel mass remaining at time t
= mf - FC x t
A = acceleration (g) at time t
= T / (me + m*)
= 6 x me / (me + mf - (12 x me x t))
So if I integrate this from t = 0 to BT, I should get the total g-hours
of thrust. Right? Well, taking specific cases, I've found that the
total thrust seems to peak at 0.614371 g-hours, when mf/me = 7.23 or so.
(Note that the ratio seems to be the only important part - well, that's
fair enough.) Also, this thing can only burn for 0.6 hours, making it
pretty much useless for long-distance flights. What I'm aiming for is a
NASP as in Dark Con; I realise that I'm never going to get Mach 25
performance under the existing rules, but this problem seems very odd.
Any thoughts?
Roger
- --
Roger Burton-West <> Reality hacker <> Economics student <> The Last Romantic
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