[AR] Re: Ozone layer was Re: Removing Coking Deposits
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Mon, 26 Sep 2016 22:39:25 -0400 (EDT)
On Wed, 21 Sep 2016, Peter Fairbrother wrote:
And wrong about that. Oh dear.
Is there no hope for horizontalists?
Perhaps some faint hope. :-) There are some advantages to be had there,
even though they are often overstated.
I hope you haven't joined the SSTO club though :)
I hate to disappoint you, but I'm a lifetime member. :-)
Indeed, "very poorly populated" is probably an understatement. Mach 6
at 100km is beyond anything ever done with a WWJ. Even the X-15
couldn't do that (either one, but not both simultaneously).
One saving grace, perhaps - it's not a Mach 6 aircraft. By the time it
reaches ~ Mach 4 it's operating as a pure rocket, in near-vacuum.
Helpful though that is in some ways, it's a disadvantage in others. In
particular, I think it means you'll need rocket thrust vectoring (or a
very hefty RCS) for control. I don't think that's ever been done in a
rocket aircraft before; the X-15 high-altitude flights were all ballistic
trajectories, with the noisy flamey part :-) finishing at much lower
altitude where aerodynamic controls still worked. Nothing fundamentally
hard about it, but it's another design complication (and potentially a
heavy one).
And it doesn't cruise supersonically either, it's all just brief spurts.
Agreed; my SST example was just an example of the sort of unexpected issue
you can run into when a straightforward-seeming WWJ is actually pretty
much outside past experience for such things.
Hmmm if the X-!6 could do 2kps... a larger, more modern, craft should have
room for some more fuel...
Remember that the X-15 was air-launched. If you do likewise, you'll need
a pretty hefty launch aircraft. If you want to operate from the ground,
you'll need considerably more fuel just to match the X-15.
Mind you, you could boost performance quite noticeably just by using a
better fuel. Basically by historical accident, the X-15 burned ammonia,
which is not great on either density or Isp. Switching to some nice dense
hydrocarbon like RJ-5 (and adjusting tank proportions for the changed
mixture ratio) would help significantly.
Henry
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