Posted on 02/04/2003 1:34:19 AM PST by 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.
The small plume appears to be about the orientation and momentum of the original object.
Exactly what I thought. That small plume maintains the origional trajectory, or seems to.
Does the larger plume appear to originate from a more lateral or port origin than the smaller plume that you see in frame 10 or 11?
I can't tell just where the larger piece seems to origionate from. I have looked at that sequance any number of times and can't really tell. However, it seems to origionate from a slightly more inboard area.
What puzzles me is that after impact, the plume from the large piece of debris does not look to follow the origional trajectory but appears to take a slightly outboard (port) track.
I'm not saying it does, it could be nothing more than an illusion, or my eyes playing tricks on me.
Is it possible that a heaveier piece of debris could change direction slightly after impact at that speed, and if so, would it be noticable?
Yes, I would think the Owens Valley photos might have exact time of the first sighting of debris falling off which would be needed for triangulation from the boys video (who were in Wupatki National Monument (NE of Flagstaff) in northern Arizona). The boys video only has time from the camera, which seems to coincide with NASA tempature off scale low. Wouldn't they need exact times for triangulation?
On another note, Justa (in post 87) says the plume is steam. If that is the case then that was a large chunck of ice/TPS, and may account for the (seeming) deviation in trajectory.
Comments?
Keep the thread going.
You mean you don't freep at work?
Memo to all: I spoke of the ET LH2 repress line earlier. We in the business called it that (I've also heard it called "pre-press"). Apparently, the correct name is ET LH2 pressurization line. Also, the forward orbiter-et attach point is called the bi-pod.
Would anybody be interested if I posted the tile drawing of the bottom of the orbiter?
Yes!
Wish me luck.
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