They probably didn't suffer much. The investigation after the disaster found that none of the astronauts had sealed their helmets on re-entry and some weren't w

They probably didn't suffer much. The investigation after the disaster found that none of the astronauts had sealed their helmets on re-entry and some weren't wearing their gloves. They would have passed out in seconds when the shuttle lost pressure. The launch and re-entry suits for the space shuttle crews were derived from the pressure suits the SR-71 and U-2 pilots wore. One pilot actually managed to survive the breakup of an SR-71 traveling at Mach 3 at 85,000 ft, although the suit was shredded when the pilot regained consciousness. The shuttle was traveling at Mach 18 at 200,000 ft when it broke up, so surviving the breakup would have been next to impossible anyhow. I think being on Challenger would have probably been worse. When the crew cabin was found, some of the emergency air tanks that have to be activated manually were found activated. It's possible the shock of the explosion activated them, but it's also equally possible that at least some of the astronauts remained conscious through the breakup and didn't die until the cabin hit the water...