Nasa is concerned the dangling material - called gap fillers - could cause part of the shuttle to overheat as it re-enters the atmosphere.
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The underside of the shuttle is exposed to the most intense heating during its re-entry to Earth's atmosphere. Protrusions on this otherwise smooth belly could disturb the air flow during re-entry, causing turbulence that raises temperatures on heat shield tiles downstream.
Give me a break. They've landed the Shuttle with this problem before. No failures so far.
The official line is that Engineers don't have any clue about the "aerodynamics" involved... I think physical on site testing should be given the priority when it comes to evidence. In this case the evidence says this is bogus.
A Public Relations strategy? Probably. Though there could be something unique about this situation that's different than previous Shuttle missions that had dangling fillers... Unless I see that different "thing", this is just a space walk for appearances as far as I'm concerned.
It's not a PR strategy. As the shttle reenters the atmosphere, a cushion of air is trapped in a boundary layer; this cushion of air acts as a sort of insulation, so that the shuttle tiles never exceed 3000 degrees Fahrenheit. Just a few inches away, however, the air exceeds 10000 degrees, enough to burn through the shuttle tiles.
ReplyDeleteThis boundary layer effect is the same air layer that forms in the dimples of a golf ball, for similar reasons.
The "[we've had] this problem before. No failures so far" argument is very weak. It is the same argument that lost two orbiters so far. They cannot afford another loss like that... but I think they will have another loss like that anyhow, before 2010 (assuming this isn't the last shuttle mission; hey, I was wrong about that, I could be wrong about this, but I don't think so).
Do the fillers actually exceed the boundary layer? I think the whole jist of the problem is that the boundary layer thickness in this flow case is not known - at least that's what I'm hearing on TV. It would be neat to see how they model fluid flow for re-entry in any analysis they do - but I bet it aint easy.
ReplyDeleteI don't know Ed, I still think this is a PR stunt. This problem is pretty much a fail or pass situation - either the fillers exceed the boundary layer or they don't. If they don't then there is no problem.
They've flown the shuttle before with dangling fillers - nothing happened. This isn't something like falling foam striking the orbiter, where they can get away with it a few times before something finally happens. Either it's a problem, or it isn't.
Of course these fillers could be hanging out more than previous occurences, and then it would be a serious problem. But NASA hasn't said that. Until something like that gets said, I'm going to be skeptical.