Early in the history of the Shuttle Program, a Thermal Protection System (TPS) patch kit was developed. This patch kit was a spray-on ablator. The idea was if a "killer tile" pop off the structure, an astronaut could do an EVA and then fix the hole left by the popped off tile with the patch kit. The concept got abandoned later on (don't know why). My guess is the added mass of hauling into orbit a complete EVA kit (pressure suit, rocket pack, etc.) for every Shuttle mission was "not cost effective". This probably was another example of the same sort of cost analysis used in determining not to design in an escape capsule for the Shuttle (too much mass).

I remember years ago, we visited the Rockwell manufacturing facility in Palmdale, California where they were manufacturing Columbia. We all flew down in small private planes (Cessnas) and landed at the runway near the Shuttle manufacturing facility. It was fantastic seeing Columbia in its semi-constructed state, walking through its cargo bay, watching the technicians install the TPS tiles, etc. While I was there, I argued with one of the Rockwell engineers about the wisdom of not having an escape system in the Shuttle. He responded by asking me whether of not I carried a parachute when I flew down to Palmdale or whether parachutes were provided with commercial jets (of course, we had no parachutes). He then went on to say the Shuttle's prime mission was to make access to space, safe, routine, and inexpensive (just like commercial aviation). I accepted his comment at the time even though it was clear (even then) that this was "sacred rhetoric". With the wisdom of greater years, I think we need less "sacred rhetoric" inside NASA and more engineers willing to risk their careers to fight against it.

Gary