Yeah, the poor astronauts were dommed by the f... Murphy Law.
As stated above, the flame leaked at the worst place. It leaked on the side of the booster facing the tank; and it leaked at a place were it broke the SRB - tank attach.
If we might suppose that the bloody flame leaked on the other side of the SRB, what happens ?
No explosion but having TWO exhausts (not one) makes the right SRB lose power. Something like 4%, but the thrust is 1200 tons...
Seconds before the explosion, Chalenger already veered from its trajectory. The orbiter computers had oriented the SSME to face the deviation, and the shuttle battled to keep its trajectory on limits.
SRB combustion last 120 seconds; they were at 60 seconds when the leak started.
Other hypothesis : the cold, then intense heat, broke the O-ring right from take-off. But the flame leaked only 60 seconds into the flight.
Why ?
The join partially melt, and the resulting "putty" (that's the word I've red) filled the hole.
No kidding; that's happened at half the flights before STS-51L ! And they did not exploded...
So why did the "putty" broke this time ?
Because after enduring -5°C on the pad, then 2000°C at launch, poor O-ring (or what was left of it) had to endure a THIRD calamity : WIND.
At 40s and 9000m, Challenger crossed the worst jet-stream ever met by a Shuttle.
These wind gusts shaked the shuttle, and are the reason why the O-ring finally broke.
According to the NASA board, had the Shuttle flown 25 to 60 times a year as planned before STS-51L, we would have lost a Shuttle... every 18months.
And the Centaur would not have helped either. It would have been a bomb ready to explode...
Challenger does not explode ? ok.
On May 15th 1986, Discovery is on the launch pad. On May 20th, come Challenger, on the other pad (not sure of the Shuttle involved aside Challenger)
Both Shuttles are loaded with Centaur stages; one will launch the Ulysse probe toward the sun, the other Galileo to Jupiter.
NASA has to launch the two shuttles at a 5-day interval otherwise launch windows will close...
So the agency is twice as much in the hurry it was on January 28 1986.
A Centaur leaks in the payload bay... kaboom!