Responding to Nick's comments:

>Interesting image that Daniel Crotty has compiled from the raw
>filters. I was interested in this one because it showed less of the
>odd red glint on the surface - a much more natural looking
>brightness, with just a hint of orange."

The color of the unablated SLA-561V looks right to me. My compliments to Daniel Crotty.

>The image is quite useful for details of the heatshield, too. It
>appears to show the texture of the "hot" side of the heatshield
>as well as a nice X-section through the broken material,
>showing a lighter brown altered layer on the surface about 1/4
>or 1/3 the thickness of the whole TPS."

I agree. The outer surface is about 0.6 inches of SLA-561V (cork dust and glass microballoons mixed in resin) injected into a graphite composite honeycomb. The SLA-561V was attached to a graphite polyimide face sheet that was glued on aluminum honeycomb (3/4 inch thick). There was an identical graphite polyimide face sheet on the inner surface of the aluminum honeycomb. Finally there was a layer of plastic film, mylar(?) that was loosely attached to the inner surface (that white plastic sheet hanging loose over the wreckage). You can see the SLA-561V is partially ablated. You can also see the cross section of the aluminum honeycomb. If you look at the lip of the heat shield, you can see some of the SLA-561V in the flow expansion region remained unablated and retained its original orange color (they use SLA-561S with the same color to cover the external tank of the Space Shuttle and it might have been a chunk of SLA-561S that killed Columbia).

>There will be closer shots in the next week or so

Looking forward to that.

>but for now, it looks as if the TPS material is distinctly >over-engineered for this job. Next time we can land more
>useful mass and less protection?

Actually, I originally designed for a lower mass TPS. However the center-of-mass was too far aft (the rover got too heavy). The center-of-mass must be forward of the center-of-pressure or the aeroshell will be statically unstable and tumble. There were also dynamic pressure and heat shield separation issues (the free stream might have blown back the headshield onto the vehicle). Somebody suggested using metal ballast but fortunately that idea was hooted down. The bosses told me to use a heavier aluminum honeycomb and be super conservative with the TPS. Essentially we used TPS as ballast to shift the center-of-mass forward.

Gary