Columbia Tragedy 2

[EnglishMuffin]

Does anyone know the current status of the Columbia investigation ? I saw some time ago that they had physically simulated the foam impact and found that it could have penetrated the wing. I recall reading that an engineer had done a study during the flight, using a "spreadsheet", and concluded that the foam impact was negligable. If so where did they go wrong ? Was it because :
a. The mass of the foam was underestimated
b. The impact velocity of the foam was underestimated
c. The strength of the tiles or their attachment quality was overestimated
d. The hardness/strength of the foam was not correctly accounted for
e. The part of the wing that was impacted was not the same as that assumed in the calculation
f. A combination of the above
g. The person who did the calculation was asked to calculate the wrong thing
h. A caveat in the person's answer was ignored
i. None of the above
Of course, I doubt if anyone reading this who really knows the answer, even if they exist, would be allowed to comment. But it seems to me that the Challenger investigation was a little more open than this one. Is this my imagination, or was it perhaps due to the presence on the committee of Richard Feynman the first time around ? I know one thing - I would not have wanted to be placed in the position of doing that quick spreadsheet calculation for management during the flight.

 

[evelrod]

If you can believe the telly (?) then it's "f", it now appears that 'ground control' was aware of a problem well before re-entry---I suspect there is a bit more to the story than we are being told (what else is new?). My brother in law was a big wig on the "escape device" team at China Lake before his death. He had a lot of stories to tell about the Shuttle and it's components. A lot of them we now know but, many that were kept secret (from the U.S. taxpayer, at least).

Rod

 

[TheTick]

There is one thing the investigation into the Columbia accident is sure to reveal: who is most expendable. Those are the people sure to shoulder the blame.

All this machinery making modern music can still be open-hearted.

 

[CWIC]

Something about "Go Fever" (The desire by those who make decisions on the ground to get the thing in the air and on schedule despite any "minor" problems...) was mentioned on the History channel.

 

[IRstuff]

Note that f includes g, which is that the "calculation" used to determine strike force of the insulation had never been validated nor intended for the application used.

TTFN

 

[Sparweb]

I would venture that the best sources for following the investigation (on the web) are the website of the investigation board itself, and the magazine group Aviation Now. Aviation Week & Space Technology is part of the publishing group, so I expect they have knowledgeable reporters working on the story.

http://www.aviationnow.com/avnow/spSec/sts107.jsp

That will link you to the index of their stories on the subject, but note that the list stops at May 12. I've seen stories published since then, but they don't seem to be in the index.

The ultimate conclusion, for lack of any contrary evidence, seems to be that the insulation impact is the major cause, though the board resisted (they claim) jumping to that conclusion all along. Many of the board's recommendations revolve around closer monitoring of the launch phase (to identify damage) and inspections on the ground (of course).

I would add that I saw a photo taken by Ilan Ramon that shows a big dent in the wing, which doesn't seem to have been given the amount of "coverage" that I expected. When I saw the picture, it looked like the smoking gun to me, but I haven't heard about it since.


STF

 

[dgallagher]

Other interesting Columbia links:

http://www.nasa.gov/columbia/foia/index.html

http://spaceflight.nasa.gov/shuttle/investigation/

 

[griffengm]

The last I heard was a blurb on PRN saying that a group using an air cannon fired an appropriate size and weight chunk of foam at a mock-up of the wing and inflicted considerable damage.
Have not yet heard of a final report.
While Raytheon may have built the O-ring that failed in Challenger, it was the "do it at whatever cost" mindset at NASA in those days that enabled the failure.

 

[davefitz]

Unfortunately, it is always possible to shop around for an answer; there is no shortage of engineers who will develope a calculation that exactly reflects the desired conclusion of management. This is certainly not limited to NASA; it is a generic problem with all engineering bureaucracies.

 

[EnglishMuffin]

Having read portions of

http://spaceflight.nasa.gov/shuttle/investigation/,

it appears that the investigators are now convinced that something like 1.67lbs of debris hit the wing at 775 ft/sec or thereabouts. Now that's a hell of an impact! They also are now saying (not surprisingly) that this probably caused "catastrophic damage", based on testing. But I distinctly recall the guy who was in charge of the program (who has since "resigned" - can't recall his name), saying within the first few days after the accident that the impact could not possibly have caused any significant damage. So somewhere between then and now, they have completely reversed themselves. I'm not saying that I or anyone else could have done any better, but I'm still fascinated to know where the error was made in the original "back of the envelope" calculation, details of which appear conspicously absent in all the above references . Whether such a calculation could have saved the crew members, even if carried out correctly and acted upon, will probably never be known of course.

 

[CoryPad]

EnglishMuffin,

The guy you recall is Ron Dittemore - more info here:

http://spaceflight.nasa.gov/spacenews/releases/2003/H03-149.html

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Maui]

Can we be certain that any calculations were even performed prior to the tragedy? No one seems to present any details about this critical step in the analysis process. Did they just shrug off the possibilty of damage to the wing, and neglect to perform any analysis at all? Mr. Dittemore's initial statements recalled by Englishmuffin seem to support such a viewpoint.

 

[frenchorse]

Perhaps a slight diversion but I don't believe microsoft garantee the validity of safety critical calculations using Excel. Perhaps it was another vendors "spreadsheet".

 

[EnglishMuffin]

The "spreadsheet" comment was something I read in the press, or heard on TV - can't remember which. I don't think I ever heard the word Excel mentioned. Someone in the press had said that they had initially "computer analyzed" the problem , but then it later turned out that this just amounted to "someone using a spreadsheet". But I also recall Dittemore saying in the first few days after the tragedy that they had re-analyzed the impact theory (or something like that), and had concluded that it was impossible, and it "had to be something else". I can't believe that this didn't involve some sort of calculation. Perhaps we'll have to wait for the movie version, if there ever is one. Come to think of it, I don't recall seeing a movie version of the Challenger disaster. I wonder why ? Legal reasons or respect for the astronaut's families maybe ? But perhaps I just missed it.

 

[GregLocock]

Can we just clear something up?

As the foam peels off the rocket it is travelling at rocket speed, ie at zero speed relative to the shuttle. At that altitude/speed how quickly would it accelerate up to the relative speed they used in the test? Does that add up?



Cheers

Greg Locock

 

[EnglishMuffin]

It took .161 seconds between the foam separation and impact, determined from visual imaging. The velocity was also found from the visual imagary, but in addition they ran a calculation based on the drag coefficient to find the deceleration rate and impact velocity, and it agreed within 20% of the optically determined value. See

http://www.caib.us/news/documents/impact_velocity.pdf

 

[dvd]

I quickly read the impact velocity.pdf mentioned above. I can believe most of the physics I read, and the low ballistic number argument makes sense. But I don't get the impression that the effect of the insulation piece "punching through" the bow shock on the shuttle wing is taken into account. It seems like there are plenty of assumptions made to slow the insulation down because of drag force and boundary effects, but none of these same effects are taken into account as the insulation piece came very near to the wing and encountered that boundary layer. I certainly haven't calculated the boundary layer thickness at the leading edge of the wing and could not say what the pressure gradient is across the leading edge shock wave, but it seems like it ought to affect the physics of the problem to some degree.

My apologies if I didn't read thoroughly enough to catch this.

 

[EnglishMuffin]

dvd - I'm somewhat skeptical, but if you are right it means that maybe they should be doing their impact testing in a large wind tunnel.

 

[EnglishMuffin]

Well, having read the report which has just come out, it seems to me that it was mainly "a", with a bit of "e" and "g" thrown in. They (Boeing) had the velocity about right, but although they did know the approximate actual size of the foam, the semi-empirical formula that Boeing used was developed for a much smaller projectile (400 times smaller). It's the old story of blind reliance on ready made formulae whose derivation we don't really understand, a failing which we have probably all been guilty of at one time or another. There is also an old engineering saying that when someone does a calculation, everyone has a tendency to believe it but the person who did it, although when someone makes a measurement, nobody believes it except the person who made it. You can see evidence of this phenomenon even on engineering tips threads.
It also looks like shuttle manager Linda Ham is getting hung out to dry (among others) for not pursuing the possibility of imaging the damage:
"Linda Ham said it was no longer being pursued since even if we saw something we couldn't do anything about it".
It is sad to see how things have changed since the glory days of the Apollo 13 rescue.

 

[CusterWilson]

A Foam cube broke the wing.
So what ?
SOFI Foam - often described as the consistancy of Shaving foam -- always breaks up into a fine mist when hit with a 1500 mph wind.
The Cameras showed this.
The Commission ignored that several percent of the Upper wing surface blew away long before any significant heating (and I mean even just 6 degrees -- the thermostats read in 6 degree steps).
Effect before Cause.
And ignored that a stress sensor went wild first, and temperature increases only occur to its left until AFTER the stress changes sign to a peak 4 times the magnitude, or that the temperature rises 4 times as fast to the right, a QUANTITATIVE agreement that Stress CAUSES the problem.
They ignored that all wires die from Top down (except the ones that drop in temperature to a cryo-death: the 7 rearmost. These die in order from the rearmost, forward --obviously a LH2 fuel leak from the fuel cells (in fact the Astronauts regained control 30 seconds after a third of 1 wing broke off and stabilized the satelite connection with 2 sensors in the Left wing still reporting good data -- then 2 seconds later EVERY electrical system blew at once).
They ignore the elevon actuator hole (so similar to Challenger's Right wing pre-breakup burnthrough).
Or to the melting of all wires in the back of STS-90, notable for sharing Wind Shears with the 2 Disasters -- which photos have proven are actually gouts of flame out of the O-ring joints (at least for Challenger (see Spaceflight May 1988: made the Cover in England but BANNED in the U.S.), but Ali AbuTaha's calculations imply locales just above the Struts are metal-fatigued at Launch thus the flames hitting the same target (control surfaces of the wing), roughly
-- and every time "they" cancel NASA's internal Accident teams and convene "unbiased" (read: ignorant, politically correct) Panels with Zero Rocket Scientists to claim (with No evidence) that they are reentry events).
-- and why do we only lose Shuttles just after a Government agency with a grudge against NASA, is allowed to "take over" NASA, gutting the budget, firing so many Scientists they have to farm out every question to companies (eg the contract to Boeing to look at the foam, or, Thiokol's to have their people "put on another hat" in order to get a second opinion (although there NASA had no SRB experts -- Mulloy was a liquid man serving under protest because all Solid Rocket Experts in the World boycotted NASA as long as the Budget people insisted Solids were "safe" when they never figured out WHY the 260 inch failed.
And of course, all 3 Shuttle hardware losses - on STS-4 both Solids sank - were drought Missions.
The 110 non-drought had a perfect record.
And the normally 1% explosion //2% overall loss rate Delta lost 2 to explosions & ran 1 into a Low orbit (of 3 just prior to Columbia's launch) due to low SRB performance from the fuel being spat out in chunks (guess which Shuttle missions had that? STS-4, Challenger Loss (not a low orbit but lots of impact damage showing chunks of fuel, though the Panel voted a violation of Conservation of energy explanation that Ice falls might break a wrist-thick steel bar & throw it several times the Fall distance, out of the search area), and the Columbia Loss.
Coincidence?
Hardly.