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  STS-51L: Myths about the Challenger disaster

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Author Topic:   STS-51L: Myths about the Challenger disaster

Posts: 3115
From: San Diego
Registered: Feb 2002

posted 01-26-2006 07:42 PM     Click Here to See the Profile for FFrench     Edit/Delete Message   Reply w/Quote
An interesting article by Jim Oberg on Challenger.
Twenty years ago, millions of television viewers were horrified to witness the live broadcast of the space shuttle Challenger exploding 73 seconds into flight, ending the lives of the seven astronauts on board. And they were equally horrified to learn in the aftermath of the disaster that the faulty design had been chosen by NASA to satisfy powerful politicians who had demanded the mission be launched, even under unsafe conditions. Meanwhile, a major factor in the disaster was that NASA had been ordered to use a weaker sealant for environmental reasons. Finally, NASA consoled itself and the nation with the realization that all frontiers are dangerous and to a certain extent, such a disaster should be accepted as inevitable.

At least, that seems to be how many people remember it, in whole or in part. That’s how the story of the Challenger is often retold, in oral tradition and broadcast news, in public speeches and in private conversations and all around the Internet. But spaceflight historians believe that each element of the opening paragraph is factually untrue or at best extremely dubious. They are myths, undeserving of popular belief and unworthy of being repeated at every anniversary of the disaster.

I'm pleased he repeats the point that Challenger did not "explode" - an error that is printed in many otherwise flawless accounts - but broke apart due to wind shear. It's important to remember that the shuttle itself has never failed - it's the results of the booster tank and SRBs on the shuttle during launch that have led to its loss on two occasions.


Posts: 400
From: Union, New Jersey
Registered: Jan 2001

posted 01-27-2006 02:55 PM     Click Here to See the Profile for Hawkman   Click Here to Email Hawkman     Edit/Delete Message   Reply w/Quote
I read that article today. Mr. Oberg as usual does a fine job.

I, too, was glad that he points out that the Challenger did not 'explode'. I'm amazed that there are press people who continue to put forth that view.

Robert Pearlman

Posts: 31720
From: Houston, TX
Registered: Nov 1999

posted 01-27-2006 03:03 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Mike Mullane devotes a chapter of his new book Riding Rockets to sharing the astronaut's view (at the time) of what happened to the Challenger crew. Its difficult to read, especially if you haven't heard the fine details before. The media most often cites the PEAPs (emergency oxygen packs) as evidence of at least some of the crew's awareness during their 2.5 minute fall to the ocean. Mullane writes about other conditions within the recovered cockpit, some I have not heard or read about anywhere else.


Posts: 1947
From: U.K.
Registered: Jul 2009

posted 09-16-2009 11:45 AM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
Apologies for coming late to this thread as I've only just found it.

I had a long talk with Bob Overmyer about Challenger. He said that the PEAPs were able to be shaken free from their mountings on the back of the seats by a sudden jolt and that once released the air mix flowed automatically. This would seem to contradict what Mullane says in his book 'Riding Rockets'. So, who does one believe? The fact that the PEAPs were depleted does not necessarily prove the crew survived the break-up if there was an automatic release of their air supply.

Which leads me to a hypothetical question. As I understand it, an abnormal wind shear factor played a part in the accident. If this hadn't been present, would the crew have had time to recognise the anomaly in the thrust from the SRB and jettison them to make a return to launch site abort?

Finally, I seem to remember reading in the early days of the shuttle that a NASA risk assessment was expecting a 'critical one' failure involving possible crew loss every 25 launches. Yes, they may have become complacent, but the fact that they have done far, far better than this surely is to their credit as well.


Posts: 638
From: Ridgecrest, CA USA
Registered: Sep 2000

posted 09-16-2009 12:29 PM     Click Here to See the Profile for OV-105   Click Here to Email OV-105     Edit/Delete Message   Reply w/Quote
The PEAPs could have been active but even if they were pressure or demand system when a person takes a breath more air would go into the helmet. One other thing two that were found and used were the CDR Scobee's and PLT Smith's since the were still mounted to the back of each seat.

The shuttle crew has no way to really watch the pressure of the SRBs during launch. The pressure difference was not too great between the two SRBs that it would have alarmed anyone. It would be a crap shoot to do a fast separation from the SRBs. That is the big draw back of the SRBs, once they are lit you have them until the are spent. The RTLS Abort is going to be hard to do even if it is just with a SSME if it goes down.

I think the risk number you heard is what came out after the loss of Challenger.


Posts: 1502
From: Greensboro, NC USA
Registered: Feb 2006

posted 09-16-2009 12:32 PM     Click Here to See the Profile for ilbasso   Click Here to Email ilbasso     Edit/Delete Message   Reply w/Quote
You can't jettison the SRBs, even if you know there's a potential disaster building. None of the abort scenarios occur until after the SRBs are separated. Once they're ignited, you have to let them burn out. If you cut them loose, they'd fly right past the Shuttle and cook everyone in the crew compartment - not to mention super-heating the ET fuel tanks and probably causing an explosion.

Jay Chladek

Posts: 2270
From: Bellevue, NE, USA
Registered: Aug 2007

posted 09-16-2009 02:02 PM     Click Here to See the Profile for Jay Chladek   Click Here to Email Jay Chladek     Edit/Delete Message   Reply w/Quote
The main thing about the PEAPs as I've understood it wasn't so much that the air bottles were depleted, but rather that on at least a pair of them the switch was physically moved from off to on (which MS Judy Resnik probably did on instinct to stabilize the CDR and PLTs O2 flow). I imagine once they hit the ocean, the contents more then likely would have bled out, so I find it unlikely there was any pressure left to read once they had been recovered.

I've felt after gathering more information about Challenger in recent years that if the crew was alive during the plunge that they probably weren't conscious, given the breakup occurred at about 40,000 feet with the cabin going uphill for a bit before it began its descent. Given the extreme nature of the breakup, an intact crew cabin doesn't mean it can hold pressure, given that air lines would have ruptured. Even with Columbia, according to the crew survivability report, micro fractures in the floor below the mid-deck would have depressurized the cabin quick. Loss of consciousness would have been within 10 seconds as Payne Stewart's Lear Jet crash showed (depressurization was at over 40,000 feet in that case). The PEAPs don't deliver pressurized O2 as they aren't intended to be used in loss of pressure situations.

As for the wind shear, that was the straw that broke the camel's back with the SRBs. The o-rings sealed okay after the initial failure at liftoff until the wind shear hit them and that is what opened up the leak again, and it thus blowtorched the aft SRB strut and the rest is history. Of course, post mission analysis would have revealed the serious primary and secondary O-ring leak, meaning the problem would have been a ticking time bomb for another mission.

I am glad Jim mentioned the vehicle didn't explode as the LOX and LHX mixing didn't produce a concussive force as it were (it would be a combustion rather then an explosion) and it was the slipstream that ripped the orbiter apart. I have heard speculation that the orbiter might have been hit on the right wing by the pivoting SRB, but I am not sure about that. So much crap was coming out of that fireball, who knows for certain what caused that wing to part company and if it was before or during the rest of the vehicle breakup?


Posts: 1962
From: Worcestershire, England, UK.
Registered: Apr 2008

posted 03-03-2015 06:31 AM     Click Here to See the Profile for Tykeanaut   Click Here to Email Tykeanaut     Edit/Delete Message   Reply w/Quote
If the flame retardent foam had still been in use on the External Tank would that have helped avert the huge explosion?

Jim Behling

Posts: 765
From: Cape Canaveral, FL
Registered: Mar 2010

posted 03-03-2015 07:05 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
The foam doesn't burn as it is. The flame from the SRB would have eroded any kind of foam and melt the metal tank's skin.


Posts: 366
From: Seneca, IL, US
Registered: Jan 2009

posted 03-03-2015 10:30 PM     Click Here to See the Profile for dabolton     Edit/Delete Message   Reply w/Quote
How confident are they that if the SRBs had been cut loose they would have scorched the cockpit? They are both below and to right/left of the cockpit centerline. Why couldn't an abort scenario have steered the boosters out and away as they accelerated forward.

It would also depend on how quickly the SRBs accelerate away as to how much exposure the orbiter would have had.

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