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SpaceShipOne and reentry heat



 
 
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  #41  
Old July 16th 04, 09:50 AM
Jan Vorbrüggen
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Default 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  
Old July 17th 04, 03:07 AM
Jorge R. Frank
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Default 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

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check "Organization" (I am not assimilated) and
think one step ahead of IBM.
  #43  
Old July 19th 04, 03:19 AM
Cameron Dorrough
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Default 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  
Old July 19th 04, 07:58 AM
Jan Vorbrüggen
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Default 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  
Old July 21st 04, 07:12 PM
David Harper
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Default 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  
Old July 21st 04, 08:23 PM
Andrew Gray
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Default 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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