NASA budget to increase dramatically...

Dan Foster wrote in
:

In article , Joe D.
wrote:
"Michael R. Grabois ... change $ to "s""
wrote in message ...

STS-51F had the engine shut down, resulting in an abort-to-orbit
(ATO).

Interestingly the media often depicts the 51-F ATO as not a big deal.
Many times I've heard media commentaries say had they lost a
2nd SSME (which they almost did) it would have forced a "risky"
trans-Atlantic abort (TAL).

In actuality, close examination of the time/velocity chart vs
pre-51L abort options shows loss of a 2nd SSME within about 15-20 sec
of the 1st would have probably resulted in loss of crew and
vehicle. This is somewhat counter-intuitive since the 1st
SSME was lost at 345 sec, at a pretty high velocity, very roughly
13k ft/sec.

Before about 360 sec there's insufficient energy for TAL, and
they had no bailout capability, and ditching wasn't survivable.

Slight clarification - before 360 there's insufficient energy for a
*single-engine* TAL. That was clear from context in Joe's original post,
but with people replying to it I fear the context will be lost.

Interesting. Why wouldn't RTLS have had been an option (even if not a
real desirable one, ordinarily) in such a scenario with two SSMEs out?

In the case of 51-F, it was because the first SSME failure occurred after
Negative Return, the point beyond which an RTLS is not possible.

Just curious. Seems to me that if it had enough energy to almost make
it for the TAL case, it would theoretically have more than sufficient
energy margin to make it for a RTLS or ECAL landing.

Keep in mind that an RTLS requires a *reversal* of course, so there comes a
point (Negative Return) where the shuttle has too much momentum going
downrange for it to make it back to KSC, especially with two SSMEs out.

(I'm not sure if ECAL abort capability was pre or post-51L, though.)

Post-51L, and only for high-inclination launches at that. Low-inclination
launches can do a kind of pseudo-ECAL to Bermuda, though.


--
JRF

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