Discovery has launched!!!
Posted: Mon Jul 25, 2005 10:02 pm
Article in Tomorrow's New York Times:
NASA Puts Shuttle Mission's Risk at 1 in 100
By WILLIAM J. BROAD
With a new realism born of disaster, NASA says that the risk of catastrophic failure during the space shuttle Discovery's mission is about 1 in 100, more than twice as great as an upbeat estimate issued before the loss of the Columbia in 2003.
While the space agency is still working on an official estimate, a spokesman, Allard Beutel, said, it has devised a rough one that will be refined by insights from the investigation of the Columbia disaster, in which seven astronauts died as the ship broke up during its re-entry into Earth's atmosphere.
The rise in estimated danger, Mr. Beutel said, came about "because we have a better understanding" of the craft's workings and limitations. He emphasized, though, that "it's a statistical probability, as opposed to what is going to happen." (The actual rate of catastrophic failure - as opposed to the calculated risk - now stands at 2 flights in 113, or 1 in 57.)
The estimate, known formally as the shuttle's Probabilistic Risk Assessment, combines the findings of flight experience, computer simulations and expert judgment to assess how the shuttle's millions of parts will work or fail in varying situations.
The most dangerous times are seen as the shuttle's ascent, when its powerful engines fire, and the descent, when it plunges though the atmosphere and maneuvers to a landing.
The risk estimate has swung sharply over the years.
Before the explosion of the shuttle Challenger in January 1986, agency officials regularly put the odds of disaster at 1 flight in 100,000, much closer to that of commercial jets. The Air Transport Association has estimated the chance of an airline disaster at 1 flight in 2,000,000.
After the Challenger disaster, the National Aeronautics and Space Administration was widely faulted for lack of candor.
"NASA exaggerates the reliability of its product to the point of fantasy," Richard P. Feynman, the Nobel Prize-winning physicist, wrote in a federal report on the disaster.
When shuttle missions resumed in September 1988, NASA officials estimated the overall risk of catastrophic failure at 1 flight in 50.
But over the years, as the agency regained confidence in the spaceships and worked hard at improving their performance, it slowly decreased its estimates for the odds of catastrophe: 1 flight in 145, 1 in 161, then, in 1998, 1 in 254.
Early this decade, a wave of new, more realistic assessments brought the figure back down to 1 in 123.
The Columbia disaster threw all those estimates into question. Mr. Beutel of NASA said the agency now put the odds of disaster at roughly 1 flight in 100, adding that engineers were still working to refine their risk calculations.
Private experts note that NASA's desire to retire the shuttles as soon as possible because of their riskiness has led to the cancellation of some plans for safety upgrades. For instance, last year the agency dropped a program to toughen spaceship surfaces that endure the highest heats during re-entry.
Seymour C. Himmel, a retired engineer who served for more than two decades on the Aerospace Safety Advisory Panel, a group that advises NASA on the shuttle, said that lack of adequate financing constantly undercut agency plans for improving shuttle reliability.
But Mr. Himmel cautioned that no matter how much money went into the spaceships, their temperamental nature meant that the risk of disaster would always remain high.
"You'd like to go to 1 in 1,000," he said in an interview. "But you're never going to get there. Too many things can go wrong."
NASA Puts Shuttle Mission's Risk at 1 in 100
By WILLIAM J. BROAD
With a new realism born of disaster, NASA says that the risk of catastrophic failure during the space shuttle Discovery's mission is about 1 in 100, more than twice as great as an upbeat estimate issued before the loss of the Columbia in 2003.
While the space agency is still working on an official estimate, a spokesman, Allard Beutel, said, it has devised a rough one that will be refined by insights from the investigation of the Columbia disaster, in which seven astronauts died as the ship broke up during its re-entry into Earth's atmosphere.
The rise in estimated danger, Mr. Beutel said, came about "because we have a better understanding" of the craft's workings and limitations. He emphasized, though, that "it's a statistical probability, as opposed to what is going to happen." (The actual rate of catastrophic failure - as opposed to the calculated risk - now stands at 2 flights in 113, or 1 in 57.)
The estimate, known formally as the shuttle's Probabilistic Risk Assessment, combines the findings of flight experience, computer simulations and expert judgment to assess how the shuttle's millions of parts will work or fail in varying situations.
The most dangerous times are seen as the shuttle's ascent, when its powerful engines fire, and the descent, when it plunges though the atmosphere and maneuvers to a landing.
The risk estimate has swung sharply over the years.
Before the explosion of the shuttle Challenger in January 1986, agency officials regularly put the odds of disaster at 1 flight in 100,000, much closer to that of commercial jets. The Air Transport Association has estimated the chance of an airline disaster at 1 flight in 2,000,000.
After the Challenger disaster, the National Aeronautics and Space Administration was widely faulted for lack of candor.
"NASA exaggerates the reliability of its product to the point of fantasy," Richard P. Feynman, the Nobel Prize-winning physicist, wrote in a federal report on the disaster.
When shuttle missions resumed in September 1988, NASA officials estimated the overall risk of catastrophic failure at 1 flight in 50.
But over the years, as the agency regained confidence in the spaceships and worked hard at improving their performance, it slowly decreased its estimates for the odds of catastrophe: 1 flight in 145, 1 in 161, then, in 1998, 1 in 254.
Early this decade, a wave of new, more realistic assessments brought the figure back down to 1 in 123.
The Columbia disaster threw all those estimates into question. Mr. Beutel of NASA said the agency now put the odds of disaster at roughly 1 flight in 100, adding that engineers were still working to refine their risk calculations.
Private experts note that NASA's desire to retire the shuttles as soon as possible because of their riskiness has led to the cancellation of some plans for safety upgrades. For instance, last year the agency dropped a program to toughen spaceship surfaces that endure the highest heats during re-entry.
Seymour C. Himmel, a retired engineer who served for more than two decades on the Aerospace Safety Advisory Panel, a group that advises NASA on the shuttle, said that lack of adequate financing constantly undercut agency plans for improving shuttle reliability.
But Mr. Himmel cautioned that no matter how much money went into the spaceships, their temperamental nature meant that the risk of disaster would always remain high.
"You'd like to go to 1 in 1,000," he said in an interview. "But you're never going to get there. Too many things can go wrong."
. I'm more used to sleeping in these summer days. Now if I wake up at 8:00 AM and find out the shuttle's not launching I'm going to be PISSED!!!
