Author Topic: New NASA Report on Loss of Columbia  (Read 29073 times)

Offline joema

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Re: New NASA Report on Loss of Columbia
« Reply #120 on: 01/03/2009 04:50 PM »
...You would only need for the escape system for covering certain parts of the flight envelope, which, by coincidence, also happen to be the most dangerous - early phase ascent and re-entry.
The entire ascent phase is dangerous. STS-51F nearly ditched in the Atlantic (which would have been non-survivable) due to an SSME failure late in the ascent. To a lesser degree the reentry phase is. An F-111-style cabin ejection system would cover only a fraction of the ascent and descent. Just doing that would incur a huge mass penalty.

You can hypothesize ever more sophisticated abort systems covering ever larger flight envelopes -- essentially an ejectable mini-spacecraft with its own independent RCS and thermal protection. The mass penalty for those would be even greater.

We have the technology to build those; however it would consume most of the shuttle payload ability. Even if the shuttle flew 20 more years it wouldn't be worthwhile, as the escape system would limit the shuttle payload to a trivial amount.

To have a cabin escape system AND a useful payload would require a total redesign. The entire system -- propulsion, ET, orbiter, etc, would have to be re-sized for a 15-20,000 lb payload increase.

The only feasible escape method with the current design is ejection seats. Those were used on the first four flights. In theory they could be used for the four upper deck seats, with limited design changes. That would restrict subsequent flights to a crew of four. Those would cover about the same envelope as STS-1 through 4, roughly 100,000 ft and Mach 3. They wouldn't help any during reentry, and there's some doubt about ejecting during stage 1 due to hitting the SRB exhaust.

Offline Rusty_Barton

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Re: New NASA Report on Loss of Columbia
« Reply #121 on: 01/03/2009 09:11 PM »
Quote
The only full cabin depressurisation scenarios I can think of where the overall structural integrity of the cabin wouldn't be automatically compromised are:

1) Debris impact shattering one or more of the cabin windows;

2) The main hatch being jettisoned in flight due to a malfuction.

Both of these would be catastrophic failures during either launch or re-entry.  Hot gas would enter the crew compartment.  (During an RTLS- or TAL-type abort scenario, the orbiter actually reenters the atmosphere, so there would still be significant heating.)


Jeff

What about a penetration from the payload bay by some loose object during reentry? Couldn't that cause a rapid decompression without entry of hot gas?
« Last Edit: 01/03/2009 09:13 PM by Rusty_Barton »

Offline Skylon

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Re: New NASA Report on Loss of Columbia
« Reply #122 on: 01/03/2009 09:32 PM »

The entire ascent phase is dangerous. STS-51F nearly ditched in the Atlantic (which would have been non-survivable) due to an SSME failure late in the ascent. To a lesser degree the reentry phase is. An F-111-style cabin ejection system would cover only a fraction of the ascent and descent. Just doing that would incur a huge mass penalty.



I thought the SSME shut-down far enough into the flight that a TAL, not an outright ditch, was the position the STS 51-F crew was nearly put in (ultimately going with the ATO).
« Last Edit: 01/03/2009 09:32 PM by Skylon »

Offline psloss

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Re: New NASA Report on Loss of Columbia
« Reply #123 on: 01/03/2009 10:15 PM »
I thought the SSME shut-down far enough into the flight that a TAL, not an outright ditch, was the position the STS 51-F crew was nearly put in (ultimately going with the ATO).
That's correct.  As noted in one of the Q&A threads, they got past the single-engine TAL performance call before engine limits were reset; in fact, as mkirk noted, the limits weren't re-enabled until after "single-engine TAL"...only to go back to inhibit shortly thereafter:
http://forum.nasaspaceflight.com/index.php?topic=2030.msg36704#msg36704

Offline joema

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Re: New NASA Report on Loss of Columbia
« Reply #124 on: 01/04/2009 02:53 AM »
...I thought the SSME shut-down far enough into the flight that a TAL, not an outright ditch, was the position the STS 51-F crew was nearly put in...
The shutdown happened about 1 min 9 sec before single-engine TAL capability. If they'd lost a 2nd SSME during that period, it would have resulted in a ditching. And there was risk of that -- two engines had sensor problems, but fortunately only one shut down.

This illustrates the entire ascent is dangerous, not just stage 1. That in turn impacts choice of ejection system.

Offline madscientist197

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Re: New NASA Report on Loss of Columbia
« Reply #125 on: 01/04/2009 08:35 AM »
What if the landing gear does not deploy? Perhaps it would be survivable, but not a situation you want to be in, so the "per the book" plan is to bailout.

With prior knowledge, yes. But the landing gear is deployed quite late, so I suspect the best they could do if it failed to deploy is a belly landing  :-[  That wouldn't be very survivable.
« Last Edit: 01/04/2009 08:37 AM by madscientist197 »
John

Offline psloss

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Re: New NASA Report on Loss of Columbia
« Reply #126 on: 01/04/2009 11:45 AM »
With prior knowledge, yes. But the landing gear is deployed quite late, so I suspect the best they could do if it failed to deploy is a belly landing  :-[  That wouldn't be very survivable.
There was some discussion prior to entry about effects of hot gas in the MLG wells, more focused on flats; links noted in the forums here a while ago (not sure if they're still live):
http://forum.nasaspaceflight.com/index.php?topic=8549.msg157729#msg157729

Offline jgoldader

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Re: New NASA Report on Loss of Columbia
« Reply #127 on: 01/04/2009 12:20 PM »
Quote
The only full cabin depressurisation scenarios I can think of where the overall structural integrity of the cabin wouldn't be automatically compromised are:

1) Debris impact shattering one or more of the cabin windows;

2) The main hatch being jettisoned in flight due to a malfuction.

Both of these would be catastrophic failures during either launch or re-entry.  Hot gas would enter the crew compartment.  (During an RTLS- or TAL-type abort scenario, the orbiter actually reenters the atmosphere, so there would still be significant heating.)


Jeff

What about a penetration from the payload bay by some loose object during reentry? Couldn't that cause a rapid decompression without entry of hot gas?


Hmmm... yes, I would guess.  Obviously, that's a pretty unlikely event.  And anything big enough to breach the crew compartment pressure vessel might do so in a big way, not a small one.  Let's hope we never find out.

Jeff
Recovering astronomer

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