IIRC they were forced to redesign the O Rings in order to conform to some EPA mandate.
The O Rings that would have kept the Challenger crew alive were banned because they contained some chemical that the extremists at the EPA didn’t like.
You are confusing the o-ring issue with the brake away foam which caused the second disaster. The foam had been changed due to environmental concerns to a foam that tended to break away in larger chunks. BTW, I designed a small piece of the shuttle in about 1976.
You’re thinking about the glue that held the heat tiles on and that has been dispelled.
No. Wrong shuttle, wrong fault. It was the foam insulation on the external fuel tank that caused the Columbia crash that the EPA was responsible for.
The O Rings that would have kept the Challenger crew alive were banned because they contained some chemical that the extremists at the EPA didn’t like.
It sounds like you're confusing the Challenger's SRB O-rings with Columbia's insulation and ice impact problems. The latter was the one where NASA had a waiver and could have used the older formula (with non-EPA-approved chemicals), but chose to use the "green" formula.
I don't recall any discussion of the o-ring material being compromised by EPA meddling (though of course, I wouldn't really be surprised at such a revelation).