vaneyck
Thanks for the interesting NY Times article. The reason for the seeming discrepancy in the dates is given in the article: “They did their study for NASA in 1990 and published three academic papers on their work in 1993 and 1994.”
The diagram seems to have been omitted from the on-line version you linked to.
The NY Times article seemed to me to be somewhat misleading in that it did not specifically say that improvements were made to the doors as a result of the study:
--- Start quote from the 1994 paper ------
… tiles in some particularly hot areas had to be redesigned. For example, the tiles in the elevon cove (the gap between the rear flaps) and on the edges of the main landing doors had to be reinforced. After these adjustments, normal heat loads were not considered a problem for well-bonded tiles. This is why our analysis focuses mostly on the possibility of tile debonding because of a weak bond or the impact of controllable debris. …
--- End quote -----------------------------------
One of the surprising findings in the 1994 paper was that a few (e.g. 12) tiles were found installed with no bond at all. They were only kept in place by friction with adjacent components. Also, workers were given a quota of tiles to install in each shift. They found they could speed up the cure of the adhesive by spitting on the adhesive, and this aided them in meeting the quota. However, once in space, resin which had been spat on reverted back to a liquid! The paper implied that all these aspects were taken care of long ago as a result of the study.
Another interesting NY Times
article says that roughness can trigger turbulence at much higher speeds than normal (e.g. Mach 18) and lead to much higher than normal heating, and that this had happened to Columbia before. Apparently a much-studied phenomenon. It can happen on one or both sides of the a/c.
