Impact Test Supports Shuttle Foam Theory

Associated Press ^ | June 7, 2003 | Marcia Dunn

[DoughtyOne]

Science - AP

Impact Test Supports Shuttle Foam Theory

2 hours, 41 minutes ago

By MARCIA DUNN, AP Aerospace Writer

SAN ANTONIO - A pair of space shuttle wing parts cracked and were shoved out of alignment when a chunk of foam slammed into them in a high-speed test, bolstering the theory that the stiff, lightweight insulation brought down Columbia.

"We demonstrated for the first time that foam at the speed of the accident can actually break" reinforced carbon wing pieces, said NASA (news - web sites) executive Scott Hubbard, the member of the Columbia Accident Investigation Board in charge of the testing.

"To me, that's a step forward, maybe even a significant step forward in our knowledge and we need to complete the test series... to understand the whole story."

Friday's test was the latest and most crucial in a series of firing experiments meant to simulate what accident investigators believe happened when foam struck the shuttle's left wing during liftoff.

Nearly 100 observers, including two shuttle astronauts, watched under sunny skies as the brief countdown ended with the word "zero"and the loud pop of a nitrogen-pressurized gun.

The 1 1/2-pound piece of foam, shot at 525 mph, cracked the reinforced carbon panel and seal and knocked both out of alignment, creating a gap of less than one-tenth of an inch between them. The crack in the panel was at least 3 inches long.

Hubbard said more analysis would be needed to show that the damage would have allowed hot atmospheric gases to enter the wing during re-entry, as investigators believe happened to Columbia.

A suitcase-size piece of foam insulation broke off the shuttle's big external fuel tank during the January liftoff. Investigators suspect it damaged the leading edge of the left wing enough to cause the ship's destruction. Seven astronauts died when the
shuttle broke up over Texas on Feb. 1.

The outdoor test was conducted at the independent Southwest Research Institute. To recreate the conditions at Columbia's launch, the foam was fired through the 35-foot barrel of a gun normally used to shoot debris at airplane parts. Most of the key pieces tested — slanted at a 20-degree angle — were taken from another shuttle, Discovery.

Twelve high-speed cameras documented the experiment, six of them inside the wing, six of them outside. Some of the footage was later played back in slow motion. It showed the 22-inch-long piece of foam skidding across the panel and shattering — which is also what happened to the chunk that hit Columbia.

On close examination, the crack in the panel was visible to the naked eye.

"If such a crack had been found on an inspection, you would not fly with it. You would not take a piece that is this damaged into space," Hubbard said.

The crack in the seal, also made of reinforced carbon, was not noticed until later.

The test, originally planned for Thursday, was delayed twice, first by thunderstorms and then by a brief electrical problem Friday.

The investigation board plans to complete its report by the end of July, and some elements of the latest draft outline were reported in Friday's Orlando Sentinel. Among the board's concerns were poor risk management, questionable policy decisions and constant budget battles.

Board spokeswoman Laura Brown declined to provide any copies of the draft, and emphasized that the outline was "a work in progress" and probably would change. She said the draft, dated May 23, was already the sixth revision and stressed that it had no findings or recommendations.

Friday's test was the first in which foam was shot at the panels and seals that form the leading edge of shuttle wings.

 Last week, a similar-size piece of foam was fired at a wing replica made up of fiberglass panels and seals taken from the never-launched shuttle prototype Enterprise (news - web sites). The parts that took the brunt of the impact were deformed by the foam.

But reinforced carbon is more brittle than fiberglass. And Hubbard predicted before the test that the foam might even shatter the reinforced carbon.

[DoughtyOne]

 

                                                                Fri Jun 6,11:39 PM ET

                          A crack is seen on an internal rib of reinforced carbon in panel 6 of a
                          space shuttle wing replica following a foam-impact test on Friday June
                          6, 2003 in San Antonio, Texas. The crack is located on the side
                          closest to panel 7. A chunk of foam fired at high speed cracked a pair
                          of space shuttle wing parts Friday, offering what investigators said was
                          the most powerful evidence yet to support the theory that a piece of the
                          stiff, lightweight insulation doomed Columbia. (AP Photo/Columbia
                          Accident Investigation Board)

                                        Foam chunks (R) break apart after being shot from a cannon and
                                        hitting a space shuttle wing replica during testing at the Southwest
                                        Research Institute in San Antonio, Texas, June 6, 2003. According to
                                        investigators, the foam chunk cracked the wing replica (skid marks
                                        visible on lower portion) offering the most powerful evidence yet to
                                        support the theory that foam cracked the wing on the Space Shuttle
                                        Columbia that broke apart over Texas, Feb. 1. Photo by Pool/Reuters

[DoughtyOne]

Same topic...

http://www.freerepublic.com/focus/f-news/924747/posts

[DoughtyOne]

[bonesmccoy]

Thanks for the great posting (re: CAIB) It is interesting that the foam block fractured into chunks. The flight film clearly shows clouds of smaller particles emerging from the various impact events. Although our thread has always noted the possibility that multiple chunks of ice/foam hit the wing. I would also note that the impact test appears to have tested only foam and not the possibility that the object in the flight video was composed of ice AND foam. I have always conjectured that the cloud of debris in the flight film was in fact composed of ice particles.

[Thebaddog]

Has it been reported anywhere that the foam makeup had been changed in the past to make it more environmentally friendly? I heard that factoid right after the accident.

[DoughtyOne]

Thank you. I would suggest that the particles we saw were in fact rather large objects. We were seeing them in relation to a very large object at great distance. While it appeared like particles to us, I'll bet we were actually seeing significant debris. If it were truly small particles we'd probably not been able to see it.

[NormsRevenge]

Thanks for re-post. Im gonna tack this thread on as well from yesterday.

Test Results Back Columbia Foam Theory

Yahoo! News ^ | 6/6/03 | Marcia Dunn - AP
Posted on 06/06/2003 4:40 PM PDT by NormsRevenge

[DoughtyOne]

Thanks. I scanned for 'shuttle' and didn't see the article. Oh well.

[NormsRevenge]

LOL.. My error. I used to do a much better job of keywording, but lately I am lacking the attention to some details.

No problem , this needs to be out there in multiple anyway. I see some posts about significant events that get posted late at night and don't get as many hits, replies as they warrant.

Keep crankin'! ;-)

[Arkinsaw]

I have always conjectured that the cloud of debris in the flight film was in fact composed of ice particles.

I agree, for the test to be even more accurate I think they need to get the foam down to the appropriate temperature and humidity. I, IMHO, suspect the shuttle wing damage was more extensive than we are seeing here due to ice.

[aristeides]

FYI.

[TLBSHOW]

Thanks for the heads up my friend~

[Lawgvr1955]

Could someone tell me how the speed the foam was traveling came to be over 500 miles an hour? Weren't the foam and the tank traveling at the same speed as the shuttle when the foam came loose? I assume that the 500 miles an hour was the speed the shuttle accelerated between the time the foam came loose and the wing struck it? It seems to me that the shuttle couldn't have accelerated that much in the brief instance of time between the foam coming loose and the wing striking it.

Isn't escape velocity somewhere around 12,000 miles per hour?

[poindexter]

"Could someone tell me how the speed the foam was traveling came to be over 500 miles an hour?"

The foam is light compared to it's surface area, and thus drag. Imagine a piece of styrofoam sheet flying out of the bed of a pickup truck. It wouldn't go 50 feet before it decelerated to 0. Same with the foam on the shuttle, except the drag on the foam chunk was many times greater, due to the great speed the shuttle was flying. Drag increases as the _square_ of velocity!

[bonesmccoy]

That type of test would require the test rig and firing mechanism to be placed in a vacuum chamber.

I've not heard of a test rig that is capable of being at the correct atmospheric PSI and the right temp.

We need to do the right test.

The only vacuum chamber that might be capable of performing this test is the one at JPL.

[bonesmccoy]

In addition to the deceleration of atmospheric drag, the vehicle is accelerating due to thrust. This factor is far less than the deceleration vector, but does need to be included in the approximation.

[Rockitz]

The drag coefficient and area are changing as the piece of foam tumbles as well.

[bonesmccoy]

actually, we discussed it in great detail in the other thread which I started in early February 2003.

For some reason the thread does not appear in the search engine, but has attained over 3500 postings.

http://www.freerepublic.com/focus/f-news/835531/posts