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.
I posted a description of the gear operation earler in this thread, but basically it's hydrauliclly-operated, with pyro backup.
This one is scaled...
to fit into the other 640x480 AF photo. The asymmetry in the AF photo is due to the orbiters yaw and the resulting temp buildup on the rightside. This is how it looks:
To get this I cut out the scaled pic overlay it, then scan it. If you make your changes to the scaled one, half.jpg, then post it I'll overlay it. You'll should print one then cut it out and overlay it. If you want the long axis, or the wingspan changed give me a %, + or -.
The opposing forces: bureaucratic inertia and other aids to complacency.
I'm 12 hours behind so this may have been answered. On day one Dittemore said the temps they had over Ca were not enough to trigger the pyros. Of course that was early assessment.
Process, process standards and in this particular case "fault tree analysis". Responsibility and responsible judgement are independent of the particular set of processes chosen, used, standard. When the judgement became, "Was the process followed?"' -- responsibility was defeated, annihilated. Better that the judgement must be along the lines of: "Is this safe, is this change safer? Will this work?"
There are questions that are process-inward, self-referential about the set process followed -- these must be distinquished from questions that are external to the process, driven in from, answering to hard reality, rather then to a construct of process and practise.
Private enterprise is used to asking, to answering such outward-directed questions -- "Is this something the customer will buy?", " Is this something that wll break and be returned, or worse, cause us to be sued?" Such questions are independent of any internal process used by an organization. They are responsible, they encourage responsibility, they breed a responsible mindset.
Then, to such orgnaizations when questions about safety get asked, when they arise, it is the natural flow to answer them responsibly -- to answer what reality asks, rather than to filter and divert through a internal construct of artificial process.
A Government bureaucracy is immune to lawsuits, has little or no requirment to sell to a customer -- that breeds a culture where all questions are framed to set process -- not reality -- but some artificial construct that comes to replace reality.
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