The Challenger Disaster - Prelaunch Situation

The Prelaunch

Situation

The following will detail the occurences relating to and prior to the STS-51-L Space Shuttle mission.

Weather Delays

The STS-51-L mission was originally scheduled for launch on January 22nd 1986 at 14:42 EST. But delays from the previous mission forced STS-51-L's launch date back one, and then two days. Then due to bad weather at the Transoceanic Abort Landing (TAL) site in Senegal, the mission was rescheduled to January 25th. Along with this change, NASA also moved the TAL site to Casablanca, where there were no night lighting, delaying the launch time even further to the morning thereafter.

But after this 4-day delay, due to bad weather at the launch site, Kennedy Space Centre (KSC) itself, NASA pushed back the launch date to January 27th. Finally, technical malfunctions and high winds forced yet another delay. This time, NASA was determined to launch no matter the situation. Unfortunately, their stubbornness led to the inevitable disaster.

Problem with the O-Rings

O-Rings were pieces used in the construction of the Solid Rocket Boosters (SRBs) to seal the joints between the field joint sections. Each SRB had 6 sections concatenated together using either factory joints or field joints. Morton Thiokol manufactured these O-Rings, which were of the utmost importance, labeled as 'Criticality 1' components. The O-Rings ensured that the high-pressured combustion gases were sealed inside the SRB and will only escape through the nozzle at the bottom end of the SRB. However tests back in 1977 have shown that the O-Rings could be damaged from the combustion inside, as well as the air pressure and temperature outside. At first the engineers and Thiokol simply dismissed this critical problem without consulting NASA to avoid bad reputation. But things changed when NASA decided to launch the STS-51-L mission despite predictions of cold temperatures on the 28th.

Engineers at Thiokol quickly raised this concern with NASA in a teleconference after the January 27th delay, believing that the forcasted cold weather would be particularly damaging and will lower the efficiency of the O-Rings. They suggested for the mission to be once again delayed. Growing impatience from the continuous delays, NASA refused to do so, unbeknownst of the safety hazards. However by ignoring this issue with a 'Criticality 1' component, NASA violated many safety regulations.

On the day of the launch, temperatures were indeed far below the standard winter in Florida, at an unusual -2°C. This was below the minimum temperature authorised for launch and over 14°C lower than the original low. Ice was present at and around the launch site in the morning. The Challenger was finally cleared to launch at 11:38 EST after the ice had began to melt. I issues with the O-Rings remained unsolved among other problems, such as the still relatively low temperature.