[AR] Re: Faster Space Transport?
- From: Keith Henson <hkeithhenson@xxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 28 Aug 2019 22:24:39 -0700
On Tue, Aug 27, 2019 at 10:07 PM Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
snip
This is simply fundamental to using chemical rockets without staging.
Going anywhere from LEO takes at least a few km/s of delta-V, and since
the exhaust velocity of chemical rockets is also in that vicinity, the
rocket equation says 2/3 or more of a fully-loaded ship's mass has to be
fuel.
That's almost true. The one exception I can think of is hauling power
satellite parts from 300 km LEO to a 2000 km construction orbit. The
delta-V is 827 m/s and the fuel mass (including return fuel for the
tug) is close to 20%. It does not matter much if you use hydrogen or
methane.
But a 2000 km construction orbit has not often been considered a destination.
Incidentally, an ISP of 2000 (Ve of 20 km/s) seems reasonable for the
move from 2000 km to GEO. You have 10 GW available and two GW fed to
arcjets seems to be enough to move a 32,500-ton power satellite out to
GEO with 10,000 tons of reaction mass and a transit time of around 2
weeks.
While there doesn't seem to be any reason to use nuclear propulsion to
move a power satellite from 2000 km to GEO, a nuclear engine might be
really useful for the 300 km to 2000 km leg. I wonder if 300 km is
too low to operate such an engine?
Keith
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