double aught said:
Yeah, they kept sending them up after Columbia even though they never fully solved the problem, just mitigated it to an extent.
I think that's a bit of an understatement regarding "mitigated it to an extent". There were many changes, upgrades, and additional tools NASA made as part of their SSP Return to Flight program. My first project at NASA was one of those: micro-wireless impact detection system for the wing leading edge RCC panels. Many accelerometers were bonded to the inside of the RCC panels to detect impacts. There were also a number of methods for visualizing and inspecting any damage.
NASA did make changes to the foam on the external fuel tank as well, even replacing some foam with heaters.
NASA also developed many tools, materials and components to repair thermal tiles and RCC panels on-orbit, testing them extensively at the arc jet facility and testing the repair techniques on-orbit.
In addition, they made some changes to how the shuttle orbited, access to the ISS for rescues, and had a pre-planned rescue mission already drawn up and ready.
The root problem was the configuration of the shuttle next to the external tank. Short of a complete redesign or possibly scrapping the shuttle program (and ISS build), there was no true solution. Removing foam would lead to a build up of ice, which does dislodge and would also impact the shuttle with far greater damage.
https://www.nbcnews.com/id/wbna7068622 Mike Shaw - Class of '03