<blockquote><font class="small">In reply to:</font><hr /><p>The risk of foam shedding is 100%. It already happened. I just hope that the progressive cooling and rewarming does not dislodge large chunks of foam. To me that could simulate the cold temperatures of January.<p><hr /></p></p></blockquote><br /><br />Actually, the temperature issues here are a bit different than winter temps. The External Tank gets filled with cryogenic propellants -- we're talking waaaaay below zero. You'll never get atmospheric temps anywhere near this low. It's actually a much bigger stress on the materials than a mere January morning. Fortunately, the External Tank is built to handle it. For instance, the LOX feedline is designed to flex during detanking, rather than shattering. As a consequence of that, there isn't any foam on the feedline itself, so it gets very cold. If water gets into the joint (as is suspected happened in this case), the water will definitely freeze, and then as the joint flexes, it could snap a chunk of foam off during detanking, which is what happened in this case.<br /><br />The cold weather in January isn't likely to aggravate this particular problem much; the only thing I can think of that might aggravate it is rain -- a source of water to freeze in the joint.<br /><br />The big danger with cold ambient air has nothing to do with the tank or the foam; it's the SRB joints that are worrisome in that case. However, NASA has introduced a number of fixes since STS-51L (the Challenger disaster) to keep those joints toasty. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em> -- The Tenth Doctor, "Blink"</font></p> </div>