[DoughtyOne]

For the last couple of days they have talked about a zippering effect. I'm not sure what would precipitate that occurance. Others have stated correctly, that many shuttles have lost tiles. The loss of a few didn't translate into a failure. I imagine the position, plus the manner of loosening etc, would determine the loss of one, more or many tiles.

[Jhoffa_]

They have to adhere to the shuttle somehow..

I guess if the adhesive failed (and aerodynamics might have helped this along) you could see a "zippering" effect..

Like running a water hose over pebbles.

[meyer]

For the last couple of days they have talked about a zippering effect. I'm not sure what would precipitate that occurance. Others have stated correctly, that many shuttles have lost tiles. The loss of a few didn't translate into a failure. I imagine the position, plus the manner of loosening etc, would determine the loss of one, more or many tiles.

Its conjecture on my part, but I think that the zipper effect would be a problem when there was a loss of several tiles in a single area. If that happens, then the heat protection in that area would be lost and the underlying metal would eventually melt, given the heat involved. As it melted, it would soften and start to peel back exposing an ever increasing interior of the ship to the intense heat of re-entry. The ship would essentially "unzip" or peel apart from that point.