Observation on TPS damage on Orbiter

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.

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.

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.

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.

Columbia unsolved puzzle, 08:52:32 Off-nominal Supply water dump nozzle temperature sensors A and B.

Perhaps the explaination is:

a) 08:52:32 a.m. Temperature rising: Enough plasma "raced right and left down the hollow RCC leading-edge panels" finally reaching sensors 33 & 34, enough to start showing the measured temperature increases.

b) 08:52:47 a.m. Temperature falling: The wing spar has been significantly breached and the plasma is no longer forced "UP" the RCC-panels toward sensors 33 & 34, but the plasma instead has an "easier" path continuing thru the wing.

Once the plasma is in the RCC leading-edge "channel" the plasma has picked up the shuttle's forward velocity and can now travel a few feet per second "faster" than the shuttle in order to travel up to the nose (even at 18,000mph there are no relativistic effects preventing velocity increases to the plasma).

These times are very close to what CAIB had determined that the wing spar had been breached...

http://www.ksc.nasa.gov/columbia/caib0506brief.htm
"Next chart. All right. These are the first measurements that we start to see go off line. So at this point here, 5216, we know the wing spar has been breached and that we are burning wire bundles."

http://www.aviationnow.com/avnow/spSec/sts107_03143.jsp
Investigators believe if tile was knocked off a carrier panel at the lower RCC/wing interface, the hot plasma could have eaten away the aluminum plate and entered the wing leading edge, where it would have raced right and left down the hollow RCC leading-edge panels, eroding the steel RCC attach points-allowing the RCC to fall off or cave back into the large wing box.

08:52:32 Supply water dump nozzle temperature sensors A and B show temporary increase in temperature rise rate, then return to normal profile.

08:52:47 a.m. Supply water dump nozzle temperature sensors A and B return to normal rise rate.

http://www.ksc.nasa.gov/columbia/caib0506brief.htm
Next chart. Now, this is something different; and we can't really explain this yet. We've tried to get our thermal folks to explain it; they can't. We've tried to get our instrumentation folks to explain this instrumentation failure, and they can't. We did not see this data until we got the MADS data, but there is a temperature measurement up where the chin panel and the nose cap attach and one of those measurements began an off-nominal rise. If you look at the plot of the data, you'll see it going on a normal kind of slope and then it takes a jump, a higher heating rate, and then for some reason it cools back down and joins where it would have been at that time if it had just kept going and continues on its way.

So we don't know what to make of that either physically -- it's hard to explain something heating up and then cooling down and getting back to exactly where it would have been if it had kept on its same rise rate -- but instrumentation-wise it's also difficult to explain it. It's different than the vent nozzle temperatures that we talked before from the OI data. There when you see a higher heating rate and they cool back down again, they're offset from their slope where they would have been. So that extra heat stayed there and they're a higher temperature but at the same rate. Here it actually comes back to the same temperature it would have been and then resumes. So it's kind of odd, and we don't know how to explain that.

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