[AR] Re: supersonic retro (was Re: Re: Falcon 9 flight today)
- From: "Monroe L. King Jr." <monroe@xxxxxxxxxxxxxxxxxx>
- To: arocket@xxxxxxxxxxxxx
- Date: Wed, 02 Oct 2013 10:54:18 -0700
Hummm I might be able to simulate a mars landing like that HIL using
X-Plane. Or do you consider that not good enough?
Monroe
> -------- Original Message --------
> Subject: [AR] supersonic retro (was Re: Re: Falcon 9 flight today)
> From: Henry Spencer <henry@xxxxxxxxxxxxxxx>
> Date: Wed, October 02, 2013 10:32 am
> To: Arocket List <arocket@xxxxxxxxxxxxx>
>
>
> On Wed, 2 Oct 2013, Aplin Alexander T wrote:
> > Musk pointed out during the post-flight Q&A that "I believe the first
> > time that any rocket stage has attempted to do a supersonic
> > retro-propulsion." Apparently it was successful (this was the 1st
> > stage's initial 3-engine re-entry burn).
>
> If you interpret "retro-propulsion" in the specific sense of firing main
> engines forward while still in detectable atmosphere, yeah, I think
> that's true. Kistler was going to do it, but they never flew. Nor did
> the shuttle ever do an RTLS abort.
>
> The Apollo LM did supersonic retro-propulsion down to landing, but that
> was in vacuum. And many rocket stages have fired small solid-fuel retros
> as part of stage separation, but that's not quite the same thing either.
>
> > IIRC super-sonic retro-propulsion is one of the unknowns encountered in
> > planning manned (and other large-payload) landings on Mars.
>
> Yes, there's a problem with the Martian atmosphere just not being thick
> enough to brake a big lander (with a lot of mass behind every square
> meter of forward surface) adequately. Supersonic retro-propulsion seems
> to be the current favorite answer to this.
>
> (One caveat: I've never seen a detailed analysis of the problem with the
> assumptions explicitly stated and justified. I have a faint suspicion
> that possibly-feasible alternatives may have been neglected because
> supersonic retro-propulsion was the pre-chosen winner.)
>
> > I've always been surprised than no one's tried it before - is it
> > something amateur rocketry could investigate here on earth?
>
> If you mean doing tests that would actually be relevant to stage return
> and/or Mars descent, I think it would be a considerable challenge, because
> you have to start high up, in thin air, moving fast. Just getting to
> those initial conditions isn't easy for amateurs.
>
> Henry Spencer
> henry@xxxxxxxxxxxxxxx
> (hspencer@xxxxxxxxxxxxx)
> (regexpguy@xxxxxxxxx)
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