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#41
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SpaceShipOne and reentry heat
And in the end, it *won't* *save* *you*. Post-Columbia RCC tests have shown
that even cracks or quarter-inch pits that don't completely penetrate the RCC can be fatal. Is there a press release or somesuch available somewhere that summarizes these experiments? If your conclusion above is correct, then it seems to me that previous flights have been lucky in that, for instance, those paint flecks made their pits in the windows and not some piece of RCC. Jan |
#42
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SpaceShipOne and reentry heat
Jan Vorbrüggen wrote in
: And in the end, it *won't* *save* *you*. Post-Columbia RCC tests have shown that even cracks or quarter-inch pits that don't completely penetrate the RCC can be fatal. Is there a press release or somesuch available somewhere that summarizes these experiments? Not directly, alas. The Implementation Plan for Return To Flight has the implications of the results: http://www.nasa.gov/pdf/58541main_RTF_rev2.pdf See Figure 6.4-1-1 on p. 1-23 (p. 55 of the PDF), which summarizes the resolution requirements for TPS damage inspection. Note that the resolution requirement on the lower surface of the wing leading edge RCC panels is 0.25 inch. What the report *doesn't* say is that this requirement is the result of RCC tests at the NASA/JSC arcjet facility that show that a 0.25 inch pit (or a 1.5 by 0.03 inch crack) on those panels results in burnthrough of the panel during entry. (Incidentally, these tests also provide the final nail in the coffin for the theory that in-flight repair of STS-107's wing damage could have saved the crew. If Columbia's panel was cracked or delaminated anything like the test panel in Figures 3.8-9 and 3.8-10 of the CAIB report, the burnthrough would have quickly propagated along those cracks and delaminated areas.) If your conclusion above is correct, then it seems to me that previous flights have been lucky in that, for instance, those paint flecks made their pits in the windows and not some piece of RCC. Indeed. -- JRF Reply-to address spam-proofed - to reply by E-mail, check "Organization" (I am not assimilated) and think one step ahead of IBM. |
#43
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SpaceShipOne and reentry heat
"Jorge R. Frank" wrote in message
... "Cameron Dorrough" wrote in : "Henry Spencer" wrote in message ... In article , Keith F. Lynch wrote: How difficult would it be to mount lots of lights inside the wings, and paint the inside white, so that any hole in the wing can easily be detected from a great distance? A lot of work if you want to get them into every nook and cranny, plus the question of whether structural damage might also happen to cut the wiring. And detection from a great distance requires a lot of light... Much better, on the whole, to improve close-up inspection technology by using things like lidar imaging. I know that I've asked this before a long time ago, on an NG far, far away, but what about using a robotic camera to do this - something like AERCam/Sprint?? It's been discussed ad nauseam over on s.s.shuttle. Here is the most recent word on it: http://www.google.com/groups?selm=Xns951054C2BFC8jrfrank%40204.52.135.40 (watch URL word wrap) Thanks, Jorge (and Henry). I concur with Adrian. :-) Cameron:-) |
#44
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SpaceShipOne and reentry heat
What the report *doesn't* say is that this requirement is the result of RCC
tests at the NASA/JSC arcjet facility that show that a 0.25 inch pit (or a 1.5 by 0.03 inch crack) on those panels results in burnthrough of the panel during entry. Thanks for the background information. Pretty bad situation - I'd call that an TPS design problem, wouldn't you? However, it's not clear to me from the above whether the burnthrough from a ~6 mm pit would necessarily translate into LOV, or just a scary descent and landing. Jan |
#45
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SpaceShipOne and reentry heat
Jake wrote in message ...
One last thing: the heating isn't caused by "friction". If that was the case, skydivers would burn. The heating is caused by hypersonic objects supercompressing the air before it could move out of the way. The supercompression heats up the air and the heat is transferred to the object via radiation. Not so much radiation as convection. Not until you hit really high velocities does radiation become a significant factor. Radiation transfer is a function of T^4. Furthermore, objects travelling around Mach 2 or 3 experience only a few hundred degrees delta-T from ambient. Radiation at these temperatures is pretty low by comparison. Dave |
#46
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SpaceShipOne and reentry heat
[copied to .shuttle, followups set]
On 2004-07-17, Jorge R. Frank wrote: If your conclusion above is correct, then it seems to me that previous flights have been lucky in that, for instance, those paint flecks made their pits in the windows and not some piece of RCC. Indeed. A related query: In a study of orbital debris I have at home, it shows a graph of the statistically expected number of window replacements - due to impact pitting, I believe - against the orbital attitude of the Orbiter. (tail-first getting less damage than nose-first, for example). It comments that flight rules require that, all other factors (mission requirements, say) considered, the attitude should be planned to minimise window damage. Is there plans to develop a similar rule regarding RCC "exposure", or is the expected flux low enough that attitude isn't a significant factor? (I suppose this is a lot less relevant now that most on-orbit time will be docked to ISS, where attitude is pretty much mandated by the station, but...) -- -Andrew Gray |
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