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  First shuttle flights had 1 in 9 chance of tragedy

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Author Topic:   First shuttle flights had 1 in 9 chance of tragedy
Robert Pearlman
Editor

Posts: 42988
From: Houston, TX
Registered: Nov 1999

posted 02-13-2011 07:27 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
Florida Today reports that NASA seriously underestimated the dangers astronauts faced when the shuttle fleet began flying according to a new internal safety study.
At the time, managers thought there was only a 1-in-100,000 chance of losing a shuttle and its crew. Engineers thought the probability was closer to 1 in 100. But in reality, the odds of a disaster were much higher.

On each of the shuttle's first nine missions, there was a 1 in 9 chance of a catastrophic accident, according to the new risk analysis. On the next 16 flights that led up to and included the January 1986 Challenger disaster, the odds were 1 in 10.

...NASA's Shuttle Program Safety and Mission Assurance Office at Johnson Space Center in Houston performed the assessment to gauge the progression of risk -- increases and decreases -- over three decades of fleet operations.

Doing so could help next-generation rocket and spaceship operators better understand the real level of risk involved in flying astronauts on inherently dangerous missions.

"The instructive piece of this is that over 30 years of operations, two accidents, countless engineering tests and all those things -- looking back at it, (now) we understand what the real risk was. But there was no way to know at the time," NASA shuttle program manager John Shannon said in an interview with Florida Today.

Among the study's key conclusions:
  • The shuttle now is 10 times safer than it was during the first flight in April 1981. The odds of a catastrophic failure now are 1 in 90.

  • The increase in flight safety was the result of safety improvements, the most significant of which were made after major events such as the Challenger disaster and the 2003 Columbia accident.

  • Not all safety modifications reduce total risk. Risk can increase if managers trade safety margin for increased vehicle performance, or as a result of external events.

MCroft04
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Posts: 1634
From: Smithfield, Me, USA
Registered: Mar 2005

posted 02-13-2011 09:38 AM     Click Here to See the Profile for MCroft04   Click Here to Email MCroft04     Edit/Delete Message   Reply w/Quote
Very interesting. In my experience risk is very difficult to quantify, more so than many engineers will lead one to believe (and I've worked with a bunch of good ones). There will always be a qualitative or judgmental aspect to risk analysis, and in my opinion any risk assessment must be taken with a grain of salt.

But, given this latest analysis, what I really wonder is will anyone believe NASA's risk assessment of any future project? Is it inherent in the process to under estimate risk at the beginning of a project? Will any risk assessment of future projects be construed as "sandbagging" just to get the program approved?

Could this new "hind sight" assessment hurt NASA's chances of getting future projects approved?

Blackarrow
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Posts: 3120
From: Belfast, United Kingdom
Registered: Feb 2002

posted 02-13-2011 01:46 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
Bill Anders is on record as saying that he thought his chance of dying on Apollo 8 was about one in three (with mission failure/crew survival also having a one in three chance, so 66.67% probability of mission failure)

GoesTo11
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Posts: 1309
From: Denver, CO
Registered: Jun 2004

posted 02-13-2011 02:36 PM     Click Here to See the Profile for GoesTo11   Click Here to Email GoesTo11     Edit/Delete Message   Reply w/Quote
At the time, managers thought there was only a 1-in-100,000 chance of losing a shuttle and its crew. Engineers thought the probability was closer to 1 in 100.
1-in-100,000?!? Really? Did anyone in the program actually believe this? 1-in-100 was optimistic to the point of delusion. 1-in-100,000 suggests engineering experience overridden by a belief in divine provenance.

NASA has NEVER been (publicly) honest about risk assessments. I've long been of the belief that the fact that America flew 32 manned spaceflights before the Shuttle without losing a crew in flight was (given the unknowns and the immaturity of the technology involved) nothing short of miraculous.

Then there's the Shuttle. I accept that so many aspects of NASA's public promises were smoke-and-mirrors from the beginning, and if the Agency had been honest about risk and cost, the thing would never have flown. NASA oversold the reliability and undersold the risk from Day One.

Objectively, given the complexity of the Shuttle system, two catastrophic failures (loss of vehicle and crew) in 132 flights, would in the pioneering days have been seen as an acceptable, even ideal, failure rate... for an experimental vehicle. Which is what it was. But no one could say that... the Shuttle was supposed to be routine. Operational.

Even given NASA's public charade about the Shuttle's expected reliability, though, I have difficulty believing that anyone within the program could conceivably have bought into the notion of a 1-in-100,000 failure rate. That's almost airliner-safe.

Hart Sastrowardoyo
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Posts: 3445
From: Toms River, NJ
Registered: Aug 2000

posted 02-13-2011 03:23 PM     Click Here to See the Profile for Hart Sastrowardoyo   Click Here to Email Hart Sastrowardoyo     Edit/Delete Message   Reply w/Quote
Which the Shuttle was initially touted as: airline-safe. Though it's fiction, "Shuttle Down" is a neat example of how routine and safe the shuttle was supposed to be: a launch from Vandenberg so routine that people barely looked up; Atlantis being "squirrely" but acceptable to fly; and an intact abort to a landing strip unprepared to receive a shuttle.

Rusty B
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Posts: 239
From: Sacramento, CA
Registered: Oct 2004

posted 02-14-2011 01:07 AM     Click Here to See the Profile for Rusty B   Click Here to Email Rusty B     Edit/Delete Message   Reply w/Quote
Wikipedia: List of spaceflight-related accidents and incidents

Hart Sastrowardoyo
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Posts: 3445
From: Toms River, NJ
Registered: Aug 2000

posted 02-14-2011 05:07 AM     Click Here to See the Profile for Hart Sastrowardoyo   Click Here to Email Hart Sastrowardoyo     Edit/Delete Message   Reply w/Quote
As for never being public with risk assessments, much to my surprise I heard a NASA administrator say in a public speech (a year or so before Columbia), that the risk was 1 in 250 of losing a shuttle with crew.

garymilgrom
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Posts: 1966
From: Atlanta, GA
Registered: Feb 2007

posted 02-14-2011 06:39 AM     Click Here to See the Profile for garymilgrom   Click Here to Email garymilgrom     Edit/Delete Message   Reply w/Quote
I have never heard the 1 in 100,000 figure but I have heard 1 in 10,000 as the probable accident rate for an SRB as designed for the Shuttle. This from an internal NASA study. They commissioned an outside engineering firm who came up with an accident risk rate of 1 in 50. As you know the Shuttle uses 2 SRBs per launch and STS-51L was the 25th launch. I'd say the outside engineers had a more accurate process for measuring risk.

moorouge
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Posts: 2454
From: U.K.
Registered: Jul 2009

posted 06-02-2011 01:30 PM     Click Here to See the Profile for moorouge   Click Here to Email moorouge     Edit/Delete Message   Reply w/Quote
Under another thread, John Charles posted:
A fascinating calculation of the risk of loss of crew and vehicle (LOCV) during shuttle missions was recently done by the JSC Safety and Mission Assurance Directorate.

If one accepts their calculations, then each of the final shuttle missions are flying with about 1 chance in 90 of LOCV, while each of the first 25 missions had about 1 chance in 10 of LOCV!

Assuming that NASA's worst fears of the risks involved in the shuttle programme were realised i.e. a LOCV loss of 1 every 10 launches (or even the most optimistic 1 every 25 launches), where would the programme be now and where would the ISS be?

Editor's note: Threads merged.

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