The Legendary Shuttle Foam Saga...

Shuttle's a go:
"'We have found no show stoppers. We believe we have made significant improvements since last year in the elimination of many of the hazards from foam,' said shuttle program manager Wayne Hale."

But that doesn't mean that there won't be foam falling off the Shuttle:
"But one of the things I don't want to hear when I go home and turn on the TV tonight is that we've fixed the tank and no foam is going to come off. Because that is not the case. ... There will continue to be foam coming off the external tank. What we have done in a very systematic manner is eliminate the largest hazards."

Gotcha. It's all about eliminating risk. A certain amount of risk is acceptable. You don't want to chasing chunks of foam that couldn't hurt your grandma let alone a Space Shuttle tile.

But you need to show some sort of metric that you've improved by. Like a method of calculating probabilities, that shows a reduction in the probably loss of a shuttle based on the improvements you've made... Or else how in the crap do you know if you've improved anything?
"While today's Debris Verification Review, or DVR, did not generate any formal probabilities regarding the actual threat posed by ice/frost ramp 'foam shedding,' Hale said he believes the IFR foam should be listed in a threat matrix as 'probable/catastrophic,' meaning that over the life of the shuttle program, debris from the bracket insulation, in a worst-case scenario, could lead to a disaster."

That's... what we had... already! The foam insulation falling of the shuttle was considered a minor threat, of minor significance to most shuttle flights for years. If anything the threat of falling foam affected the shuttle over the long duration of its lifetime.

Not every flight resulted in a loss - only one. So there's bupkis for difference as far as I'm concerned.
"Even so, Hale believes NASA is justified in pressing ahead with near-term shuttle flights while engineers devise a bracket redesign that eventually will allow them to remove the ice/frost ramp foam altogether."

Great. So why didn't they do that in the FIRST PLACE.
"While the IFR foam represents a clear long-term threat, the risk on any given flight is in line with dangers posed by other systems."

That's not re-assuring.
"With the very worst-case assumptions, there were some numbers down as low as 1-in-75 and for some of the better-case assumptions, you're talking about numbers on the order of 1-in-400 for ice/frost ramp foam losses," Hale said.

"I hate to quote probability numbers without context because it depends so much on what the assumptions were and how conservative or how fine the calculations were that went into the case. But we're talking, basically, something on the order of 1-in-a-few hundred, or 1-in-100, which is consistent with the entire overall risk we fly with the space shuttle."

Again is this an improvement or not? And as to the "context", let me fix that problem up with you. Take the most conservative estimate as the God given truth. Work with the worst case scenario and hope for the best.

Though I find it a little perplexing... They already have a shuttle program to gage where there statistics are sound or not. I mean they had 1 bad flight in over a hundred. That should indicate to me, that any estimate that comes near or close to a 1 in 100 chance is probably a good estimate. But the whole point of this exercise was to decrease or eliminate that chance. Doesn't sound quite like they've done that.
"While the PAL ramp debris lost during Discovery's flight didn't hit anything, NASA managers ultimately decided to remove the ramps on the assumption computer modeling and wind tunnel tests would show the pressurization lines and cable tray are tough enough to endure the ascent environment.

Then why were they put on in the first place? This sounds like incredibily wasteful engineering. Who was in charge of the PAL ramp design? Didn't someone think about testing it in the beginning of the program? How much money would it have really cost when you consider the hassles they're going through now?
"'Today we have a tank on the pad that has lost 34 pounds, the largest amount of foam that we've ever taken off the tank, to reduce the hazard,' Hale said. 'We have put on a special set of sensors, both accelerometers and force measurements on that tank, as well as a suite of six new cameras on the solid rocket boosters that will be monitoring the performance of the vehicle during ascent to ensure that we have done our job properly in the removal of that protuberance air-load ramp. But we do expect to see foam come off.'"

Now that can be seen as progress. That's the first real measure I've seen quoted that I think can be considered an improvement. A reduction of 34 pounds of foam out of a total of what though? That's the other thing to consider.

I'll give Hale one thing: he's honest. This quote proves it:
"Basically, this vehicle, and you can take this to the bank, is about a 1-in-100 vehicle..."

And there you have it folks. That's what the Shuttle has been, and so far will continue to be: a 99% safe vehicle. Give it a hundred flights and something will go wrong.

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