[AR] Re: Space shot and it flight profile.
- From: Ben Brockert <wikkit@xxxxxxxxx>
- To: "arocket@xxxxxxxxxxxxx" <arocket@xxxxxxxxxxxxx>
- Date: Fri, 15 Nov 2013 18:22:49 -0700
On Fri, Nov 15, 2013 at 4:19 PM, <qbert@xxxxxxxxxxxxxxx> wrote:
> After going through several space blog updates I ran into a Sugar Shot to
> Space blog which then led me to Bens Brokets assessment of heat vs speed and
> altitude. The question I have, would it not be better to go slower though
> the lower atmosphere, say up to 40,000, or even 60,000 feet until
> approaching mach lessening both the dynamic forces and heating.
>
> Robert
SS2S is unguided. The rocket begins gravity turning as soon as it
comes off the rail; if you wait too long for the second burn then
it'll land in the next state. Could add some steerable fins and a
guidance system and fire the second burn when the vehicle senses that
it's going mach 0.2 or so to get the maximum altitude, but that's a
significant step up in complexity of the system and the waiver.
A simpler approach would be to launch it as straight up as possible
and put in a flight computer that fires the second burn when the
rocket reaches some minimum velocity or tilts over to some angle,
whichever happens first. This is closer to off the shelf hardware.
The most realistic approach is to just launch a two stage rocket, then
the drag isn't as big of an issue and you get higher performance with
a shorter coast.
That analysis was very much a first pass; the mesh is mediocre and
it's looking at steady state. I've done better ones since with time
dependent properties more appropriate to a rocket traveling up, rather
than cruising sideways. Unfortunately I never got material properties
for the nose cone so I wasn't able to answer the question they were
asking, which is what temperature the nose would end up getting heated
to.
If the thought "would it not be better to go slower though the lower
atmosphere" is run as far as possible, the usual conclusion is "let's
build a rockoon" or "let's build a space elevator". But going
hypersonic at 13km isn't impossible, it just takes some attention to
materials and design.
Ben
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