So I once saw a talk by one of the Steve K. Robinson, a mission specialist on the STS-114 where a gap filler came loose from one of the tiles and was protruding

So I once saw a talk by one of the Steve K. Robinson, a mission specialist on the STS-114 where a gap filler came loose from one of the tiles and was protruding near the front of the shuttle. Accord to him, this was a very scary situation. The reason being that the gap filler could trip the flow near the front of the shuttle from laminar to turbulent. This would be very very bad. So if you haven't taken fluid dynamics, turbulent flow transfers heat a lot better than laminar flow and once flow becomes turbulent it tends to stay that way. So what this meant is that pesky gap filler could have made almost all of the flow trailing it turbulent, creating a region of increased heat transfer across much of the shuttle, which could have destroyed the shuttle. And unfortunately poor Steve knew about all of this because he did some work on hypersonic flow in grad school. So NASA engineers went all apollo 13 and macgyvered some procedures on how to turn the hack saw aboard the station into filler slicer-offer. Steve Robinson himself decided to perform the mission, this was the first and probably only time a spacewalk was performed under the shuttle's heat shield. This was a very risky mission where a small mistake could do more damage than the gap filler could do. Luckily in the end, the gap filler was loose and easily removed by pulling. All that caused by a tiny piece of ceramic sticking out about a centimeter! Now the interesting thing is that a couple missions later, NASA engineers decided to put a turbulent trip on the shuttle on purpose, because we don't understand hypersonic boundary layer transition all that well[1]. It was near the end of the shuttle, so the region of increased heat transfer couldn't do much damage, but still performing such an experiment on the shuttle, almost right after the Columbia disaster, was pretty nuts. Necessary though, because experiments on hypersonic flow are difficult to perform in wind tunnels. One of the reasons capsules are so compelling is that there is less distance for this laminar to turbulent transition to occur. [0]http://www.nasa.gov/returntoflight/crew/EVA_gapfiller.html http://www.nasa.gov/returntoflight/crew/EVA_gapfiller.html [1]http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110013660.pdf http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/2011001...