Author Topic: Space Shuttle Abort Evolution  (Read 8861 times)

Offline rdale

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Space Shuttle Abort Evolution
« on: 09/24/2011 02:49 am »
This paper documents some of the evolutionary steps in developing a   
rigorous Space Shuttle launch abort capability. The paper addresses the abort strategy during the design and development and how it evolved during Shuttle flight operations. The Space Shuttle Program made numerous adjustments in both the flight hardware and software as the knowledge of the actual flight environment grew. When failures occurred, corrections and improvements were made to avoid a reoccurrence and to provide added capability for crew survival. Finally some lessons learned are summarized for future human launch vehicle designers to consider.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015564_2011016321.pdf

Offline brahmanknight

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Re: Space Shuttle Abort Evolution
« Reply #1 on: 09/24/2011 02:57 am »
Oh hell yes!

I've always wanted more info on shuttle aborts.

Offline brahmanknight

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Re: Space Shuttle Abort Evolution
« Reply #2 on: 09/24/2011 05:17 am »
From the report, conclusion number 1.
1. Include aborts as part of the launch/crew vehicle design and development

I never understood why this wasn't focused on more during design.   

Offline AS-503

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Re: Space Shuttle Abort Evolution
« Reply #3 on: 09/24/2011 05:39 am »
Did anyone else notice (page 3) that the Orbiter has "evelons", NOT elevons?

At least they did not list the body falp, or wigns, or speed barke..okay i'll stop.

Offline DT1

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Re: Space Shuttle Abort Evolution
« Reply #4 on: 09/25/2011 08:53 am »
This paper documents some of the evolutionary steps in developing a   
rigorous Space Shuttle launch abort capability. The paper addresses the abort strategy during the design and development and how it evolved during Shuttle flight operations. The Space Shuttle Program made numerous adjustments in both the flight hardware and software as the knowledge of the actual flight environment grew. When failures occurred, corrections and improvements were made to avoid a reoccurrence and to provide added capability for crew survival. Finally some lessons learned are summarized for future human launch vehicle designers to consider.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015564_2011016321.pdf

I can remember hearing the ATO abort of STS-51F live on Voice of America. If that engine shut-down would have ocurred around half a minute earlier they had to make a landing around midnight local time in Spain.
Even more furtunately it was a Spacelab mission and the kind of orbit or altitude was not so important for the mission. An ISS mission would have had to bring the payload back to earth.
BTW this was the only SSME in-flight shut-down out of 405 -3x 135 - flights - extraordinary accomplishment!!!
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Offline mtakala24

Re: Space Shuttle Abort Evolution
« Reply #5 on: 09/25/2011 09:07 pm »
an ISS mission would have at least considered the joint underspeed recovery prosedure (JURe), wouldn't it?

Offline Jorge

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Re: Space Shuttle Abort Evolution
« Reply #6 on: 09/25/2011 09:17 pm »
an ISS mission would have at least considered the joint underspeed recovery prosedure (JURe), wouldn't it?

Yes.
JRF

Offline joema

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Re: Space Shuttle Abort Evolution
« Reply #7 on: 09/26/2011 09:41 pm »
I never understood why this wasn't focused on more during design.   
Abort systems (in the sense of launch escape) are heavy, complex and only cover a small portion of a launch vehicle flight envelope. It's not like a fighter plane ejection seat that can cover most of the envelope.

Early the in shuttle development they planed on a cabin ejection system but as in most aerospace development programs weight problems happened. A cabin ejection system was just too much weight.

The next choice was SRB thrust termination, where the nose caps would be blown off and jettisoned early. If an impending failure threatened the SRBs or the ET, they'd just terminate the SRBs do a fast sep from the ET if needed and land or ditch the orbiter.

Unfortunately more thorough structural studies showed about 20,000 lbs of reinforcement was needed to allow the stack to survive SRB thrust termination, so that was shelved.

For comparison the Apollo launch escape rocket was 33 ft x 4 ft and weighed 8,000 lbs. The Apollo capsule itself weighed only 12,000 lbs, so the LES was 66% of the spacecraft weight.

I believe the Orion launch escape rocket weighted 17,000 lbs. So while it's possible to have launch escape, the weight penalty is great.

The shuttle is designed to a 140% structural safety margin, and the SRBs have a 200% structural safety margin. After the above weight issues became clear, NASA felt the best approach was take advantage of this robustness and focus on intact ascent abort options. There's actually a rational logic to this.

As shown in the Abort Evolution document, continued enhancements to shuttle ascent abort procedures made it much safer over time, especially after Challenger STS-51L. E.g, after these enhancements and ET strut reinforcement in the 90s, in theory the crew could survive a triple engine failure right off the pad, the so-called "three out blue" case. The SRBs alone retained sufficient thrust-to-weight and steering authority to reach a bailout configuration.

By contrast the Saturn V could not withstand a *single* engine failure before about T+15 sec. The 4-engine thrust/weight was below 1:1, so if a single engine failed it would fall back onto the pad. Yes they had launch escape but this illustrates why it was needed.

Another issue: even if astronauts are saved via an ejection system, a loss of vehicle disaster will shut down the program for a long time while it's studied. It's still a huge program impact.
« Last Edit: 09/26/2011 09:43 pm by joema »

Offline simonbp

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Re: Space Shuttle Abort Evolution
« Reply #8 on: 09/27/2011 04:59 pm »
Several of the final-round Shuttle proposals (e.g. Lockheed comes to mind) had solid abort motors on top of the wing root. North American Rockwell won out, despite not having the abort rockets.

As always see Jenkins for more info...

Offline TFGQ

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Re: Space Shuttle Abort Evolution
« Reply #9 on: 10/07/2011 03:08 am »
sts 93  columbia was a real close one  they were one failure away from performing some kind of abort mode
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Offline dbaker

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Re: Space Shuttle Abort Evolution
« Reply #10 on: 10/07/2011 07:14 am »
Several of the final-round Shuttle proposals (e.g. Lockheed comes to mind) had solid abort motors on top of the wing root. North American Rockwell won out, despite not having the abort rockets.

Good points brahmanknight but the NAR design proposal for Phase C/D did have ASRMs (Abort Solid Rocket Motors), mandated at that time for both MDAC and NAR contenders by JSC. My early design iteration change documents for 1972/73 track its demise. One attractive line of argument for carrying the ASRMs lay in the mass offset thru using the delta-V inherent in the ASRM to compensate for the reduced ascent velocity imparted by the SSME/SRB combination due to higher GLOW. In other words, by burning the ASRMs after ET jettison (when they had no possible use as abort motors) they would perform the function of the OMS burn for orbit insertion and compensate for dragging them all the way up. As you say, structural beefup for all of these modes made nonsense of the payload promise. Apart from which there were separation problems with the ASRMs.

Offline Phillip Clark

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Re: Space Shuttle Abort Evolution
« Reply #11 on: 10/07/2011 07:24 am »
I have just tried to access the link given in the first posting of this thread, and it no longer exists.
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Offline dbaker

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Re: Space Shuttle Abort Evolution
« Reply #12 on: 10/07/2011 07:40 am »
I have just tried to access the link given in the first posting of this thread, and it no longer exists.

Works for me Phillip...just tested.

And by the way, my preceding message should have attributed comment reply to simonbp - sorry for that!

Offline alk3997

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Re: Space Shuttle Abort Evolution
« Reply #13 on: 10/07/2011 02:35 pm »
Did anyone else notice (page 3) that the Orbiter has "evelons", NOT elevons?

At least they did not list the body falp, or wigns, or speed barke..okay i'll stop.

To be fair to the authors, once the paper is submitted for ITAR approval, it is submitted.  So, even if later you find a typo, it cannot be changed, unless you want to go through the ITAR approval process again.  At that point the author has to decide to present the paper as-is or to risk another approval process where there is a possibility of the paper not being approved on time and you have nothing.

Another unfortunate side-effect of ITAR is that late typo catches in papers can't be fixed easily.

Andy
« Last Edit: 10/07/2011 02:36 pm by alk3997 »

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