Cold Night at the Cape 27 January 1986

You are on an evening teleconference between NASA managers and engineers from Morton Thiokol, the contractor that builds the Space Shuttle’s solid rocket boosters.

Space Shuttle Challenger is due to launch the next morning after several postponements. Temperatures at the Florida launch site are forecast to fall well below freezing overnight, colder than for any previous shuttle launch.

Known information

Forecasts suggest about 22°F (−6°C) overnight and about 26°F (−3°C) at the planned launch time.
Rubber O-ring seals in the booster joints have shown erosion and hot gas ‘blow-by’ on some earlier flights.
Thiokol engineers recommend not launching below 53°F (12°C), the lowest temperature of any previous flight.
The data linking cold temperatures to seal problems is limited, and some NASA managers question whether it proves a connection.
The mission, which includes teacher Christa McAuliffe, has already been delayed several times.

Reveal what happened (spoilers: decide first)

Fact

What actually happened

After a management caucus, Thiokol reversed its engineers’ recommendation and the launch went ahead. (Launch as scheduled)

During a break in the call, Thiokol managers reconsidered and then recommended launch, despite objections from engineers including Roger Boisjoly and Arnold Thompson. Challenger lifted off on the morning of 28 January 1986 with the air temperature at about 36°F (2°C). Seventy-three seconds into the flight the vehicle broke apart, killing all seven crew members. The presidential Rogers Commission found that an O-ring seal in the right-hand booster had failed.

Important

Possible consequences · Analysis and speculation, not fact

A delay to warmer weather would very likely have reduced the risk from the cold-stiffened seals, although the underlying joint design problem would have remained until it was identified and redesigned.

History does not reveal what would definitely have happened under the other choice. Many factors could have changed the outcome.

Context · Why it was decided this way

The Rogers Commission criticised the decision-making process, finding that concerns about the seals had not been passed up to the most senior launch officials. It reported that one Thiokol manager was asked to “take off his engineering hat and put on his management hat.”

Later analyses, including sociologist Diane Vaughan’s study of the decision, argue that repeated seal damage on earlier flights had gradually come to be treated as an acceptable risk, a pattern she called the “normalisation of deviance.” Others emphasise schedule pressure and communication failures between organisations.