On 02/05/07, Roger Burton West <[EMAIL PROTECTED]> wrote:
On Wed, May 02, 2007 at 04:02:37AM -0400, DataPacRat wrote:
>I've recently purchased GVB, and have been playing around with it. My
>most recent idea was to see if I could put together a design with the
>criteria: TL8, no superscience, carrying at least two people in a
>luxury suite from the Solar System to Alpha Centauri. To make it more
>interesting, I wanted to do so in as little time as possible - which,
>effectively, means maximizing the delta-vee.
In other words, picking the engine with the highest specific impulse
(see VxII).
Indeed.
>After some experimenting, the drive that seems to offer the most
>delta-vee per pound of fuel at TL8 is the Orion...
That has an (American-style) specific impulse of 400,000seconds at TL8
(maximum - you can't quite reach this, but you can get arbitrarily
close). A fission fragment rocket from VxI has a specific impulse of
1,000,000seconds. Worth considering? (One "2% of drive mass" fuel load
per 8,000 hours of operation.)
Hm, interesting. I'd missed that one - probably because I was skimming
through GVB's listings instead of the books, and didn't see any
fuel-loads for that.
Let's see, rather than building the whole thingamajig in GVB, with 2.5
times the Isp, and assuming a similar fraction of fuel, the
flight-time is reduced to something on the order of 200 years...
definitely getting closer.
The current design I'm fiddling with is 83% fuel. I suppose if the
fission-fragment has the best Isp, the only options I have left are to
increase the fuel-to-payload ratio, and/or use some staging to get rid
of some of the unnecessary structural mass in mid-thrust.
>(Fully-loaded LWt times
>burn time giving a delta-vee of 3,204,600 metres/second.)
(My mistake in typing that out - that's supposed to be fully-loaded
sAccel times burn-time.)
Um, no. The whole point is that you lose mass as you go along.
I'm quite aware, but the 'Simplified Delta-V' is a bit quicker for an
order-of-magnitude comparison between different drives.
See VxII again:
delta_v=21.8 * ISp * ln (1 + (fuel weight / dry weight)) in mph.
GVB can handle this - you just need to set vTOTAL_FUEL (I think) to the
fuel mass, with a link node.
I'm not quite up to fiddling with GVB's formulas in that manner yet. :)
You might want to think about a spin habitat too.
Once I get travel time down to less than a century, then I'll worry
whether mechanical or chemical (ie, Ursaline) means are best to
prevent biological zero-gee problems. :)
Thank you for your time,
--
DataPacRat VA3BOS
"You shall not accept any information, unless you verify it for
yourself. I have given you the hearing, the eyesight, and the brain,
and you are responsible for using them." -- Qur'an 17:36.
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