Observation on TPS damage on Orbiter

NASA photos | 2-3-03 | BoneMccoy

[bonesmccoy]

In recent days the popular media has been focusing their attention on an impact event during the launch of STS-107. The impact of External Tank insulation and/or ice with the Orbiter during ascent was initially judged by NASA to be unlikely to cause loss of the vehicle. Obviously, loss of the integrity of the orbiter Thermal Protection System occured in some manner. When Freepers posted the reports of these impacts on the site, I initially discounted the hypothesis. Orbiters had sustained multiple impacts in the past. However, the size of the plume in the last photo gives me pause.

I'd like to offer to FR a few observations on the photos.

1. In this image an object approximately 2-3 feet appears to be between the orbiter and the ET.

2. In this image the object appears to have rotated relative to both the camera and the orbiter. The change in image luminosity could also be due to a change in reflected light from the object. Nevertheless, it suggests that the object is tumbling and nearing the orbiter's leading edge.

It occurs to me that one may be able to estimate the size of the object and make an educated guess regarding the possible mass of the object. Using the data in the video, one can calculate the relative velocity of the object to the orbiter wing. Creating a test scenario is then possible. One can manufacture a test article and fire ET insulation at the right velocity to evaluate impact damage on the test article.

OV-101's port wing could be used as a test stand with RCC and tile attached to mimic the OV-102 design.

The color of the object seems inconsistent with ET insulation. One can judge the ET color by looking at the ET in the still frame. The color of the object seems more consistent with ice or ice covered ET insulation. Even when accounting for variant color hue/saturation in the video, the object clearly has a different color characteristic from ET insulation. If it is ice laden insulation, the mass of the object would be significantly different from ET insulation alone. Since the velocity of the object is constant in a comparison equation, estimating the mass of the object becomes paramount to understanding the kinetic energy involved in the impact with the TPS.

3. In this image the debris impact creates a plume. My observation is that if the plume was composed primarily of ET insulation, the plume should have the color characteristics of ET insulation. This plume has a white color.

Unfortunately, ET insulation is orange/brown in color.

In addition, if the relative density of the ET insulation is known, one can quantify the colorimetric properties of the plume to disintegrating ET insulation upon impact.

Using the test article experiment model, engineers should fire at the same velocity an estimated mass of ET insulation (similar to the object seen in the still frame) at the test article. The plume should be measured colorimetrically. By comparing this experimental plume to the photographic evidence from the launch, one may be able to quantify the amount of ET insulation in the photograph above.

4. In this photo, the plume spreads from the aft of the orbiter's port wing. This plume does not appear to be the color of ET insulation. It appears to be white.

This white color could be the color of ice particles at high altitude.

On the other hand, the composition of TPS tiles under the orbiter wings is primarily a low-density silica.

In the photo above, you can see a cross section of orbiter TPS tile. The black color of the tile is merely a coating. The interior of the tile is a white, low-density, silica ceramic.

[Resolute]

"but how did it slow to 500mph"

Here's a way for low-density draggy foam to slow down from 1570 mph to 1064 mph in 300 milliseconds . . .

Time since separation (s)	Relative axial velocity (mph)	Relative axial displacement (ft)
0.000	0.00	0.00
0.030	70.59	0.79
0.060	135.25	3.06
0.090	194.68	6.70
0.120	249.52	11.60
0.150	300.27	17.65
0.180	347.38	24.78
0.210	391.24	32.91
0.240	432.16	41.97
0.270	470.45	51.91
0.300	506.35	62.66

[Resolute]

Assumptions:

Alt = 28 km

Rho = 0.02439 kg/m^3

Sref = 0.120492 m^2 (spherical approx for 1920 in^3 -- is very conservative)

V0 = 710.8 m/s (1570 ft/s)

Mass = 1.211 kg

Cd = 1.8 (is 45% more draggy than small steel cubes)

Shuttle accelerates at 1.5 gees

Vertical ascent (is conservative Alt, Rho relative to non-vertical ascent)

[Resolute]

Correction: 711 meters/sec = 1570 miles per hour.

[XBob]

What we cavalierly call the 'tank' is actually the tank container. It contains 2 tanks inside of it. One for LOX and another for hydrogen.

Look at a diagram of the tank.

As a tank 'container' the volume discrepency becomes moot.

The 'tank' is so light, and holds so much weight, sort of like a 2 liter soda bottle. I think it gets both shorter and 'fatter' because of the light structure - it only weighs agout 66,000 lbs and carries what, 1.5 million pounds. So, IMO, non-engineering opinion, it sort of 'squooshes' down, like a full soda bottle vs an empty one.

[XBob]

speed at 81 seconds - someone posted it here on the thread, and I seem to remember about 1250mph or knots, somewhere around mach 2.3 or so, but then NASA apparently figures mach differently, and this is just my memory.

[tubebender]

Thanks for all the replys...I'm in this way over my head.

And the deceleration interval was not a couple of milliseconds. The debris clearly required several video frames to transverse from point of detachment to point of impact. From the links that I saw here on FR, the frame rate was 30 frames/s. (I advanced the video one frame per step, and counted 30 per each 1 second advance of the movie clock). This translates to 33-1/3 milliseconds between video frames, not a "couple of milliseconds."

I missed the 1570 mph somehow. I have seen from 30fps to 90fps for the film/video. Dittemore said it was high resolution ? He also showed a lesser quality film/video of the underside of the left wing after the strike that did not show any obvious tile damage but it was fuzzy compared to the one of the foam.

[tubebender]

BTW...I think dittemore said there were 17 frames in the clip from seperation to exit under the wing.

[Budge]

2398 -

The photo John Jamieson speaks of in 2398.

[NCC-1701]

A question I have regaurding the color issue. Just for coversation's sake I'll call the color reddish-orange. Is the reddish-orange color of the ET foam insulation a consistant color throuout, or is the foam covered with a reddish-orange weather-proof application? I believe that would provide a clue as to what is being looked at and help the ivestigative team. I haven't read all the posts on this thread yet so that question may have been answered. I await comments. May the Crew of STS-107 Columbia rest in peace and the families, relatives, friends and NASA community find comfort from the support they are recieving. And may the shuttle program return to flight. We need it.

[NCC-1701]

Why not equip the remaining orbiters with a similar pod. Put a camera in it so it can record the climb to orbit and possibly re-entry. I feel if there had been such a camera on STS-107, the investigatorive teams would have a better view of what happened. Cameras have been routinely used on unmanned Titan, Atlas, etc. launches and have provided some unique views. Why not do it with manned vehicles. If nothing happens, the views it captuers would be great. There was a camera mounted on the ET durung a recent shuttle launch. About the engineering films of the launch, I am thankfull that the left wing angle was caught. Had it been the right wing, nothing would have been seen. I hope the most likely cause will be found and the remaining fleet returns to flight.

[Cold Heat]

Put a camera in it so it

I agree totally.

[Cold Heat]

BTW, is that a bloody "A" or a "B" in that NCC-1701?:-)

[Budge]

2398 - Once the hole is there, the edges of the carbon should burn away slowly because the silicon carbide is only a very thin surface coating and carbon burns very well. The hole would slowly grow as the airjet also starts to penatrate any insulation and aluminum and copper wires in it's way. I suspect the defect in Columbia started this small or maybe even smaller. The jet would be very well defined and would just start eating away, much like water jets can be used to cut steel.

To my untrained eye this is what I think happened. I posted way back in this thread that I thought the foam/ice that hit the wing might have cracked or shifted either the RCC or a locking "T" there, causing a 'pin hole,' just enought to cause what you described here. I, of course, had no way to prove it, it was a hunch based only on having watched my next door neighbor use a plasma torch to cut heavy steel.

As I have followed this thread, you, xBOB, Bones and several others have shown how this could well have been the case.

In your photo (2408) that is far more damage than I would have expected.

[DonnerT]

Surely NASA has filmed the entire re-entry of some previous flights inside the cocpit. Has anyone ever seen one?

[NCC-1701]

I have seen many of those videos. It's just like crews have said. It's like flying inside of a neon tube. On vid I've seen shows the slow plasma build-up. Really neat. Wish I could see that. If the camera is mounted on the aft bulkhead, you would see the lighting increase, much like a dimmer switch being tuned up. During that, you can see the crew getting shaken around. Not roughly, but enough to make them move. If one of the crew in the rear of the flight deck has camera pointed out the overhead window, you'll dee the trailing tail of the plasma plume, occassionaly litup by the firing of the reaction control system (RCS) thrusters. As the orbiter starts coming out of all that, you can see the last flames of re-entry licking around the windows, sort of like a propane burner going out slowly. The shaking smooths out and if it's light at the landing site, look out the windows and you can see the groung. All in all, neat and impressive. I've been watching NASA Select Television for years and suggest eveyone get it. There are other equally interesting programs there, all space related, of course. And the beauty of NASA TV is there is no on-screen logos to mess with the images presented, as there is in CNN.

[Cold Heat]

Yes, they did and have. If fact, Columbia was the test vehicle used. The equipment had been largely removed during the overhaul. I made a post regarding this project somewhere near the beginning of this thread.

[DonnerT]

I have NASA tv on sattelite but have never seen more than a few second clips. I would like to watch the whole thing from beginning to end.

[Thud]

Photos of meteoriod strike on the leading edge of another shuttle.

[Dark Wing]

NASA will have to develope some sort of manuevering, controlled, unmanned sensor platform to launch off the shuttle for a post lift off visual inspection of the TPS. You could call it a USV, "unmanned space vehicle."

I don't see NASA letting this thing be tethered for fear it would tangle in the control surfaces. Nor do I see them wanting it propelled so it comes back to the shuttle afterwards for fear of a TPS strike with it.

I guess they could put a gyroscope on a CCD camera and eject them out of the payload bay. The shuttle could rotate under it for a visual inspection. The camera USV would then deploy a light solar sail/drag chute to deorbit quickly.

[Dark Wing]

Perhaps the plasma path inside the left wing changed from not immediately fatal in the right bank to rapidly fatal once it was in a left bank? As an example: The plasma path in the right bank caused it to eat upper wing honeycomb and exit the wing. While in the the left bank caused the plasma path to eat primary support structure.

Changes in venting of interior plasma from the wing as it shifted from right to left bank could also explain changes in drag.

This could explain Thud's objections about Columbia lasting to Texas.