Heatshield Options

[akuo]

Heatshield AHOY!

:-)

[djellison]

HAPPY CHRISTMAS EVERYONE!!!



Now sod off and eat Turkey

Doug

[volcanopele]

Turkey not done yet :mad: But look at all that junk strewn around. I remember when there were some cranks thinking they were seeing machine parts and springs in the Spirit images and well, there are some real springs How big is that large one on the lower left side of the main heat shield part?

[Guest_cassioli_*]

I'm no more reading this forum since several months... <:-)
Your images are very interesting! Maybe Opportunity took enough pictures so somebody can produce 2 color photos of the heatshield taken from close angles, so I could combine them in a 3d-color-anaglyph? It would be cool!

I also would like to build a little animation of the heatshield: are there enough different angles pictures to allow this? Can you give the links, or just link the thumbnails?


BTW, what is the "Genesis" you are talking about?

[Guest_Analyst_*]

"Genesis" ist the poor little solar wind sample return spacecraft that crashed into the Utah desert in September 2004. BTW, is there any news on the sample quality yet?

Analyst

[pioneer]

BTW, is there any news on the sample quality yet?

I heard some samples were salvagable, but I haven't heard about any results from them.

[Guest_BruceMoomaw_*]

Opinions seem to vary on whether the Genesis samples are scientifically retrievable. The team itself is insisting that many of the collectors for oxygen and nitrogen isotopes in the solar wind -- the top two science goals of the mission, by far -- are indeed retrievable, and that the same may be true of many of the lesser goals (such as noble gas analysis). Others -- such as SpaceDaily's professional curmudgeon Jeffrey Bell -- say that, since the solar wind atoms are embedded only 1/50 of a micron deep in the collector plates (that's less than 1 millionth of an inch) and the latter were exposed to atmosphere, humidity and dust, no scientist in his right mind will trust the results. However, I've talked personally with Donald Brownlee -- the PI for the Stardust comet-dust retrieval mission -- and he thinks that it may very well be possible to adequately clean the top surfaces of the collector plates of contamination without removing such shallowly embedded solar wind atoms; as he points out, anyone who washes a glass window with a non-abrasive substance routinely does just that. So, until I learn more, I reserve judgment.

Brownless, by the way, also says that an examination of the construction records for the Stardust capsule make it pretty certain that the upside-down parachute switch error in the Genesis capsule has not been repeated for the Stardust capsule -- but he also says that, since the dust grains in Stardust are embedded 1 to several cm deep in a sheet of relatively nonbrittle aerogel, they are more likely to come through a crash in scientifically acceptable shape, unless the capsule crashes onto the salt flats after the latter have been recently rained on. However, finding and retrieving the capsule quickly would be vital -- and the Stardust capsule will land at night.

[tedstryk]

This is all good to hear. After reading his recent article, my suggestion to Mr. Bell is that he seek therapy, as he seems generally angry at the world. However, his concerns are often not born out by more reputable scientists. My suggestion is that he sometimes look on the bright side of things, or he find some private place to go and be really, really sad where he can't bother anyone else.

[jamescanvin]

That picture is a great Christmas present Doug. Thanks, how did you know what I wanted!

James

[Guest_BruceMoomaw_*]

In my own experience, Bell is right about 80-90% of the time. ANYONE who has to deal habitually with NASA naturally turns into a cynic (including Reagan's science advisor George Keyworth, who called it "the only governmental agency which lies not just sometimes but most of the time"). As for Genesis, we have yet to see who's really correct.

[Guest_BruceMoomaw_*]

Latest shots fo the heatshield at http://qt.exploratorium.edu/mars/opportuni...cam/2004-12-27/ . Is that white sheet which overlays the biggest fragment the actual heat-resistant cloth layer? If so, it came through Martian entry pristine-looking, with no visible sign of charring.

Also some nice closeups of the actual impact crater, such as http://qt.exploratorium.edu/mars/opportuni...A3P2360L4M1.JPG -- confirming again that the shield, despite coming down fast enough to shatter itself, barely punched into the solid rock layer covered by just a few cm of sand -- and some more of the second-largest shield fragment, such as http://qt.exploratorium.edu/mars/opportuni...A3P2360L7M1.JPG .

[Guest_Sunspot_*]

Do you think it would be safe enough to drive the rover into the "crater"? Perhaps they could perform a trenching operation inside the impacted area to see how far down the bedrock is.

Looking at the heatshield in it's current state.....I think it may literally be "inside out"... the shiny layer we see was part of an insulating layer on the inside of the heatshield.

You can just make out a kind of rough textured surface on the other side which I think might be the abaltive material on the front of the heatshield.

It's a little easier to see in this image:

[ilbasso]

Anybody have a guess at the heatshield's approximate speed when it impacted?

Going back through the timeline, it looks like the heatshield separates from the backshell at somewhere between 25,000 and 30,000 feet in alitutde, 20 seconds after chute deployment (the chute deploys at 30,000 feet and 1,000 mph). I wonder what the terminal velocity is for such an object...relatively flat and light - how much would wind resistance have slowed it down even though there is less air than on earth, but counteracted somewhat by lower gravity? Genesis came in pretty hot and didn't even have the benefit of a parachute, but it impacted at "only" 200 mph.

I agree that it looks like the big piece is turned inside-out. I would bet that the thermal blankets go on the inside. The schematic on the MER website also indicates that there is a "radar absorber" in the heatshield - is that part of the blanket's function?


Piece "B" looks like it has some charred surfaces readily visible.

[Guest_BruceMoomaw_*]

Yes, I have since been taken to the woodshed by another member of my Planetary Science webgroup (who shall remain nameless) regarding my misinterpretation of what I was looking at:

"The 'white' sheet is the base layer of a series of sheets of material,
capped by a reflective mylar layer - the innermost part of a
multi-layer thermal protection system. This consists of a structural
frame, an outside ablative layer of what Gary Allen advises is
ground-up cork and resin binder, and an inner thermal blanket to stop
residual heat getting through to the rover.

"What is perhaps confusing you is that the piece of the wreckage that
is standing up on its side has been almost flipped inside out.

" http://www.lyle.org/~markoff/processed/1P1...78L234567M1.JPG

"The dark 'knobbly' material is the heated and partly ablated TPS. The
broken edge at the left shows the paler-brown surface that has been
altered by re-entry heat compared to the thicker dark unaltered
material. You can see parts of the mylar layer, and the underlying
white blanket that has been everted over it."

Well, that's what I get for not actually looking up the structure of the heat shield -- I was thinking vaguely of the flexible entry-thermal blankets that cover those parts of the Shuttle exposed to minimum heating.

[Guest_BruceMoomaw_*]

Has the rover rolled right up to one of the heat shield fragments? I find it impossible to interpret the little thingie at the top of this Forward Hazcam image any other way: http://qt.exploratorium.edu/mars/opportuni...FRR2761R0M1.JPG .

Also, what's with the spot on the left front wheel where some of the aluminum tread is missing? I know that there was one patch on each wheel where it was deliberately omittted -- but this missing patch seems irregularly bordered, and there's what looks like a crack leading away from one of its edges.

[mhoward]

Has the rover rolled right up to one of the heat shield fragments? I find it impossible to interpret the little thingie at the top of this Forward Hazcam image any other way: http://qt.exploratorium.edu/mars/opportuni...FRR2761R0M1.JPG .

The image in question is actually from Sol 54, or thereabouts; you're looking at the egress ramp on the lander and part of an airbag. I know, it threw me for a minute, too! I guess Oppy is clearing out its memory banks for some reason.