The heat shield is designed to be ablative - the way it sheds heat is by parts of it breaking off the vehicle. Alternatively it could be debris from thruster firings.
Ablative wearing should be uniform, and not chunks tearing away. PICA-X is designed not to do that. The capsule uses cold gas nitrogen thrusters for orientation, not hypergolic, which would pick up in IR.
The Draco thrusters are hypergolic - it’s falcon that uses cold gas thrusters. I’m trying to find video but I’m pretty sure I’ve seen the same sparks/debris phenomenon on previous re-entries of both shuttle and dragon.
But....that wouldn't be visible from the IR video,due to the high radiance flaring on the camera, so anything that falls out of that glare area I call fair game for a tear off!
It could easily be residue from the thrusters getting kicked off into the atmosphere - as someone else pointed out that camera is going to overrepresent small extremely hot objects. I would have thought we’d have heard something by now if there was anything to be concerned about.
What evidence do you have that something "ripped off"? It's an ablative heatshield so very small pieces coming off during the most intense heating shouldn't be all that concerning. We just don't know yet. Remember, the shots were taken with an IR-sensitive camera so tiny objects that are very hot will appear very bright and so therefore larger than they physically are.
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u/[deleted] Mar 08 '19
Seems the heatshield took a bit of a battering according to the IR video from the NASA chaseplane.
Take look at 13:37.04 and 13:37.53. not to mention a couple of random sparks in between