[AR] Re: DARPA responsive launch challenge
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 22 Apr 2018 19:51:01 -0400 (EDT)
On Sun, 22 Apr 2018, Henry Vanderbilt wrote:
I'm not greedy - I'd settle for injection velocity around 20,000 m/s...
And that'd also be about 2000 seconds Isp even before you combust the
propellant...
Reminds me of several of Heinlein's 1950s space-travel stories, in which
the propulsion systems are solid-core nuclear-thermal rockets whose
propellant is stabilized atomic hydrogen (just how it's stabilized is, of
course, never explained).
If you could actually do that, the first thing that would happen is that
when somehow-stabilized H hits your hot reactor core, the stabilization
pretty much inevitably comes undone.
The second thing that would happen is that your very expensive reactor
core melts and washes out the nozzle.
And the third thing would be that engine performance improves as a result,
because all that graphite and uranium was just getting in the way.
2H->H2 all by itself is good for about 2000_s Isp (if the stabilization
doesn't add a significant inert component) -- *much* hotter than you're
going to get out of any solid-core reactor.
But may the gods have mercy on your soul if your fuel tank ever takes a
micrometeorite hit, because no conceivable escape system will get you
away from *that*. Stabilized or not, that stuff would be the
great-grandmother of all energetic monoprops, with all that implies...
Henry
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