USAF Imagery Confirms Columbia Wing Damaged

Aviation Week and Space Technology ^ | February 7, 2003 | Craig Covault

[jpthomas]

High-resolution images taken from a ground-based Air Force tracking camera in the southwestern U.S. show serious structural damage to the inboard leading edge of Columbia's left wing, as the crippled orbiter flew overhead about 60 sec. before the vehicle broke up over Texas killing the seven astronauts on board Feb. 1.

According to sources close to the investigation, the images, under analysis at the Johnson Space Center in Houston, show a jagged edge on the left inboard wing structure near where the wing begins to intersect the fuselage. They also show the orbiter's right aft yaw thrusters firing, trying to correct the vehicle's attitude that was being adversely affected by the left wing damage. Columbia's fuselage and right wing appear normal. Unlike the damaged and jagged left wing section, the right wing appears smooth along its entire length. The imagery is consistent with telemetry.

The ragged edge on the left leading edge, indicates that either a small structural breach--such as a crack--occurred, allowing the 2,500F reentry heating to erode additional structure there, or that a small portion of the leading edge fell off at that location.

Either way, the damage affected the vehicle's flying qualities as well as allowed hot gases to flow into critical wing structure--a fatal combination.

It is possible, but yet not confirmed, that the impact of foam debris from the shuttle's external tank during launch could have played a role in damage to the wing leading edge, where the deformity appears in USAF imagery.

If that is confirmed by the independent investigation team, it would mean that, contrary to initial shuttle program analysis, the tank debris event at launch played a key role in the root cause of the accident.

[TomServo]

Already posted here.

[coloradan]

My back-of-envelope analysis of telescope is here.

[Slyfox]

Have they found out yet at what point in the re-entry was the shuttle when NASA recieved the last verbal transmission from the crew?

[montag813]

Why can't we see the picture? If we so much as touch the actual debris of the left wing we will be sent to Camp X-Ray, but we aren't even allowed to see the damn photo?

[aShepard]

I've wondered whether the excessive heat in the landing gear pods picked up by the sensors, could have overheated the tires, which I understand are filled with liquid nitrogen; causing the tire to blow, exploding the wing structure.

[Paleo Conservative]

Perhaps you want Saddam and all the other enemies of the US to know exactly what our technical capabilities are so they can take countermeasures. If a camera in a ground based telescope is able to take clear pictures of a space shuttle flying overhead, imagine what a similar camera in low Earth orbit would be able to see on the ground.

[Steely Tom]

Having seen the televised video of the foam-impact event, I have been skeptical of the view (given in FR discussions) that the foam was travelling too slowly when it hit the Orbiter to have done any great damage.

I submit that it is hard for any of us to imagine the amount of force that chunk of foam would have experienced as it entered the slipstream around a craft going more than two thousand miles per hour.

I am thinking here of something I read as a seventh or eighth grader, reading a book about test pilots. One chapter of the book (I wish I knew the name) described the experience of the first pilot to eject at a speed greater than mach 1. Can't remember his name; I don't think he was a test pilot, but rather a regular Air Force pilot who ejected from an F-100 or F-101.

He said that the force of the air blast was "like hitting a brick wall." The book described how he was nearly killed by the impact. His watch, shoes, and wedding ring were all removed while he fell unconcious to the ground; his parachute opened automatically. He suffered many broken bones.

As I recall, his speed was under 800 miles per hour when he ejected; the shuttle was going at least two and a half times faster. Keep in mind that the amount of energy available to do mechanical work increases as the square of the speed.

Our aerospace technology does not have very much experience handling situations that arise when supersonic aircraft start shedding pieces, hitting objects, etc.

Also, the shuttle is primarily a spacecraft, not an aircraft, and is designed for minimum weight at every possible point. It's design has therefore been optimized to be strong only in the directions necessary for normal operation. I'm thinking here of that weather-satellite launch (back in the '80's) where the center engine (on a multi-engine booster) cut out a minute or two into the flight. Telescopic imagery showed how the booster started to tilt (yaw) immediately upon engine shut-down, and how the shroud protecting the satellite disintegrated just a second or two later, when the rocket was only a few degrees off its correct heading. The designers had made the shroud only just as strong as it needed to be for a correct flight path.

(steely)

[jpthomas]

Special ground-based Air Force space imaging systems were used to capture these photos of the shuttle as it was passing through the ionosphere. The original, full-resolution images may be classified. Why? Because they could reveal the accuracy at which we can resolve space objects from the ground. The images may eventually be publicly released after going through an evaluation for that purpose. If they are eventually released to the public, they may be slightly degraded in resolution to prevent our potential enemies from knowing the precise accuracy of these ground-based imaging systems.

We may learn more about when and if these images will be released to the public at this afternoon's NASA briefing (begins at 1630 EST).

[ecomcon]

Remember that both pieces (the piece of foam, and the wing)are moving at the same speed when the foam piece left the booster. How hard the foam piece hit the wing is dependant on a number of things.

1. The speed of the shuttle at the time of foam detatchment.
2. The speed of the shuttle at the moment of impact.
3. The amount of time that elapsed between detatchment of foam and impact.
4. The weight, volume, and shape of the foam piece.

It is the relative speed between the foam and the wing that is important.

[jpthomas]

I think you are correct in estimating a rapid deceleration of the piece of insulation. In fact, the shuttle program manager himself mentioned a relative speed of 750 ft/sec when it impacted with the orbiter. A low-density, flat object like this chunk of insulation would experience rapid deceleration due to aerodynamic drag.

Another freeper came up with this same estimate for the speed of impact by reviewing the video of the impact. He estimated there was a closing distance of 25 ft in the two frames just prior to impact. At 30 frames per sec, that yields a 25 x 30 = 750 ft/sec relative speed between the insulation and orbiter upon impact. Dittemore stated they actually used a 1500 ft/sec impact speed when they analyzed the effect of the impact of the insulation, just to be conservative.

One factor Dittemore did not address (and which I believe could be very very significant) was NASA's assessment of the orientation of the insulation at impact. If it hit the orbiter wing edge-on, the force of the impact would have been more like a karate-chop, with greater potential for serious local damage. If it hit broadside, the force of the impact would have been more like a hand-slap, with a distributed impact.

[SierraWasp]

Thank you for posting this. It may have already been posted, but I missed those posts.

The Full Article is the best technical explanation I've seen anywhere and is something EVERY FReeper should read.

Especially the part about the wing's "glove" and the leading edge made from Reinforced Carbon Carbon (RCC)! Some experts have told Tom Sullivan who has been filling in for Rush that that stuff shatters much more easily than tiles, expecially at cold temperatures!!!

I flagged him at his website TomSullivan.com and suggested he refer to the full article during his local show, today, here in the Sacramento Region on KFBK from 1:PM to 4:PM.

[jpthomas]

Dittemore was asked a similar question during one of the NASA press conferences. He didn't seem to believe this was the cause of the loss of the orbiter. Consider the following excerpt from the article:

* 7:58 a.m. CST: Still over New Mexico, the elevons began to move to adjust orbiter roll axis trim, indicating an increase in drag on the left side of the vehicle. That could be indicative of "rough tile or missing tile but we are not sure," Dittemore said. At the same time, the elevons were reacting to increased drag on the left side of the vehicle, the left main landing gear tire pressures and wheel temperature measurements failed. This was indicative of a loss of the sensor, not the explosion or failure of the left main gear tires, Dittemore believes. The sensors were lost in a staggered fashion.

[Mat_Helm]

At 30 frames per sec, that yields a 25 x 30 = 750 ft/sec relative speed between the insulation and orbiter upon impact

750 ft/sec = 511.5 mph.....not even. There is no way that piece of foam acquaried a delta V of over 500mph upon separation and impact on the shuttle. Possibly 100 mph is more likely and the foam was more than 25 feet away from point of separation and point of possible impact.

What is more likely to have caused damage was ice. It may have been ice forming under the foam panel upon filling the tank with LOX and hydrogen that caused the panel to bulge and or pull off from the tank. A one foot chunk of ice moving at 100-200mph would have the mass to cause structural damage to the leading edge. In the 5 frames of video the panel appears to split into two pieces just prior to impact. Half ice and half foam panel separating?

[Dog Gone]

Interesting article. I hope we see the photo soon.

[jpthomas]

Loss of voice communication and all other data took place abruptly at approximately 7:59 CST when the orbiter was traveling over Texas at a speed of Mach 18.3 and altitude of 207,000 ft. Some "garbled" data was received for another 30 seconds, but no further voice communications. NASA engineers are analyzing the additional data to see what useful information they might obtain from it.

[aShepard]

Dittemore was asked a similar question during one of the NASA press conferences

Thanks, I didn't catch that!

[jpthomas]

I know it seems implausible, but I was watching the press conference when the shuttle program manager (Dittemore) stated that NASA engineers determined a 750 ft/sec relative velocity between the insulation and the orbiter. He said they actually used a 1500 ft/sec impact velocity in their analysis to be conservative.

[Slyfox]

Thanks. I'd been wondering about it.

I saw a video once that someone made inside the shuttle as it was in re-enter. All the occupants were belted in their seats, all had their suits on and the entire outside was engulfed in flame. They couldn't see out the window in front. And, because they were dependent upon their instruments, they were flying essentially blind. They probably had no idea of what was happening except for an indication of overheating on the control panel and the attempt of the computer to correct the yaw.

[Lessismore]

Aerodynamic drag increases as the square of the velocity. Since the shuttle was traveling at 1900 mph, the drag on the insulation would be very high -- probably hundreds or even thousands of pounds of force accelerating the 2.5 lb piece of foam back towards the shuttle. An accurate calculation of drag would require knowing the shape and orientation of the foam piece with respect to the air stream. Furthermore, the calculations have to be done for the supersonic regime, since initially the foam is moving at about Mach 2.5.