I recollect, that after each of the early shuttle launches, 100 or so thermal control tiles were found missing. These had to be replaced before each subsequent flight. I remember wondering why the lost tiles were there in the first place if they apparently weren't necessary for thermal protection in the area of the shuttle where they were placed.

Now, I am wondering whether it was just dumb luck that more shuttles weren't lost during re-entry. Was it just luck that these tiles just happened to come off in areas where their thermal control was not necessary? Perhaps they came off after the major portion of the re-entry was completed and the thermal loads were not very high? Was the fly-off of these tiles a potential source of vehicle impact damage during re-entry?

Also, as this problem seemed to go away, how were fixes made?

Anyone have any detailed knowledge (damage reports, analysis reports) of the impact these lost tiles could have had to the vehicle?

closed as too broad by Organic Marble, Deer Hunter, Rory Alsop, Nathan Tuggy, mins Aug 12 '15 at 5:40

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

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    I count 6 questions in the body of that post, and one in the title. What should I do if I can answer one or two out of the six questions?(1) My tendency would be to skip to the next question where there is a single, specific question.. 1) And that was hypothetical. In reality I can answer none of the questions well, but that's not the point, given I was thinking about how others have been known to act in that situation.. – Andrew Thompson Aug 3 '15 at 16:40
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    I disagree about it being too much in one question. The primary question is about the likelihood of issues related to the loss of the tiles. The next couple "questions" were just guesses at the reasons this wasn't an issue earlier. Then it asks about other potential damage from the tiles, and what was done to try to resolve these issues. In other words, there are a lot of question marks, but this question as a whole is really only asking about the damage caused by, and related to, these tiles, and what was done to fix it. Maybe it could be reworded, but I don't think it should be closed. – duzzy Aug 3 '15 at 22:10
  • It would seem obvious to me that loss of a small number of tiles (100 out of approximately 25000) would not allow significant heating of the metal skin, and even if it did, the heat would spread fairly evenly throughout the structure: aluminium is highly conductive, the low density air in the upper atmosphere is not. Even if part of the skin were to fail, this would not constitute a structural failure. It would however allow decompression to occur. I'm not an expert but I would assume only the crew area of the shuttle would be pressurized, and in any case they would all be wearing spacesuits. – Level River St Aug 3 '15 at 22:50
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    Your basic premise is false: STS-1 (the mission with the worst tile loss) lost only 16 tiles, all of which were on the OMS pods (the coolest part of the Shuttle during re-entry). The second-worst, STS-27, lost one tile. – Mark Aug 4 '15 at 7:57
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    The tiles were not ablative. Ablative heat shielding is consumed during use; the tiles were designed for reuse. – Organic Marble Aug 4 '15 at 11:12

This question is too broad IMHO but if you want to learn about the history of tile problems and the organizational response, there is no better starting place than Chapter 6 of the CAIB report, "Decision Making at NASA".

Here's a very pertinent graph to pique your interest. It shows a count of tile damage sites of greater than one inch diameter per mission.

enter image description here

Edit: I can address a couple more of your questions. There is information about all these points in the CAIB report.

Perhaps they came off after the major portion of the re-entry was completed and the thermal loads were not very high?

This seems to be incorrect. From the reference above, most of the known tile damage was caused by impacts during ascent. This is determinable by looking at the resulting thermal damage.

Also, as this problem seemed to go away, how were fixes made?

If you are referring to the decrease in damage after the 2nd return to flight, an enormous amount of effort was expended to reduce foam shedding from the External Tank, a primary source of tile-damaging debris during ascent.

  • The axis labels and arrows don't match up in that illustration. e.g. "STS-17" image clearly pointing to bar labelled "STS-16". This in itself may not be a big problem but it shows that we cannot trust any of the labels. – Lightness Races in Orbit Aug 4 '15 at 11:02
  • Interesting. I'm not sure why they included the pictures anyway. – Organic Marble Aug 4 '15 at 11:08

Lets break this down to specific questions:

after each of the early shuttle launches, 100 or so thermal control tiles were found missing. These had to be replaced before each subsequent flight. Why [were] the lost tiles were there in the first place if they apparently weren't necessary for thermal protection in the area of the shuttle where they were placed.

There are several assumptions here, which are not supported in fact. There were many spots of tile damage greater than 1 inch (25mm) in diameter. That's not the same as a missing tile, and the design of the tiles may have included increased thickness to allow for expected abrasions, dents, etc.

I would be surprised if there were hundreds of missing tiles. Hundreds of spots of damage greater than 1 inch in diameter is quite a different thing. Each tile was several inches thick and its likely they could meet specification even with some amount of damage on the exposed side.

There are multiple books about the detailed design of the shuttle and the operating regimes they were expected to face, and actually faced. Perhaps the first step is identifying kinds of tile damage (<1% of depth affected, >1 inch skin face affected <10% of depth affected, tile missing, tile and adjacent tile missing.) you care about, or that someone has already studies. Then you need to get the title damage survey data. Chart damage kind or instance by launch date. Columbia, the Shuttle lost from surface damage, was not destroyed by tile damage. It had its carbon-carbon leading edge damaged. Different material, common damage mechanism (foam falling off the booster tank).

was just dumb luck that more shuttles weren't lost during re-entry?

A very large question, but almost certainly luck, aka capable design, competent manufacturing, responsive operators, redundant systems, conservative rules, occasional reasonable management, played a role.

Was it just luck that these tiles just happened to come off in areas where their thermal control was not necessary?

Objection. Presumes hundreds of tiles damaged == hundreds missing. Missing is different and far more dangerous. If you can get tile damage and tile missing data, a composite plot of the locations which lost tiles, which suffered damage > 1 inch diameter, > 1% of tile thickness, > 10% tile thickness, and lost tiles AND adjacent tiles would be worthy reductions of fact, on the way to information.

Perhaps they came off after the major portion of the re-entry was completed and the thermal loads were not very high?

Earlier response indicates majority lost during ascent, which makes sense because: Fast in dense air, tank shedding insulation not present on re-entry, water, ice, bird exhaust, etc, more likely from Earth rather than orbit.

Was the fly-off of these tiles a potential source of vehicle impact damage during re-entry?

Another respondant says, "No"

this problem seemed to go away, how were fixes made?

meaning tiles, not including leading edges? As noted, big efforts to keep foam from shedding from booster.

Anyone have any detailed knowledge (damage reports, analysis reports) of the impact these lost tiles could have had to the vehicle?

You might adjust this question once you know more of what actually happened.

Yes, in fact. STS-27 was impacted at the solid booster release, leaving a large hole. In fact, the aluminum structure holding the shuttle was damaged, as is show in the below photo.

enter image description here

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