Nels who is not Florin:
The point is—I think—fairly simple: unless you can be some large number of
nine’s certain that the rocket will always shut down when ordered, you must
design the LES to get away while the engines are still running.
Your other points are valid but (just) solvable given a fast enough system
activation and sufficient acceleration.
Bill
On Fri, Feb 9, 2018 at 5:59 AM <Nels.Anderson@xxxxxxx> wrote:
Gesendet: Donnerstag, 08. Februar 2018 um 21:36 Uhr
Von: "William Claybaugh" <wclaybaugh2@xxxxxxxxx>
In designing an escape system one can not rely on the rocket(s) shutting
down.
I'm struggling a bit with this point, especially since a common liquid
failure mode is shutdown or loss of thrust. If one is really worried about
it, how about a backup shutdown system.
As to the best escape trajectory being off to the side, as long as the
crew capsule is mounted on top, even with a lateral abort trajectory,
you're going to have to outrun the rocket initially. But I see a couple of
other problems here. For one thing, if you want to abort sideways, you're
still going to need one heluvan acceleration if you want to get far enough
sideways to avoid passing through the still-burning booster's exhaust
plume. IIRC, non-survivability of passing through the plume is what led
NASA to abandon a Shuttle abort scenario whereby the SRBs would be let go
(not so much the crew vehicle escaping the rocket, but the rocket escaping
the crew vehicle).
The other point is that you can't assume you know which way the booster is
going: a very plausible abort scenario is that the booster has developed
excessive attitude rates.
-- Nels (aka Florin)