Author: nasashuttle
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STS 51-L Launch 01/28/1986 filmed from TV Van #2 at the Shuttle Landing Facility (SLF) on site at Kennedy Space Center. This video was made from a copy of a ¾ videotape received from NASA under provisions of the Freedom of Information Act. This video is not copyrighted. Its wide distribution is welcome as an aid in understanding the experience of watching the disaster unfold in person. STS-51-L crew: Dick Scobee, Michael J. Smith, Ronald McNair, Ellison Onizuka, Christa McAuliffe, Gregory Jarvis & Judith Resnik. The shuttle was designed to withstand a load factor of 3 (or 3 g), with another 1.5 g safety factor built in. The crew cabin in particular is a very robust section of the shuttle because of its design and construction of reinforced aluminum. During vehicle breakup, the crew cabin detached in one piece and slowly tumbled into a ballistic arc. NASA estimated the load factor at separation to be between 12 and 20 g; however, within two seconds it had already dropped to below 4 g and within ten seconds the cabin was in free fall. The forces involved at this stage were likely insufficient to cause major injury. At least some of the astronauts were likely alive and briefly conscious after the breakup, as three of the four Personal Egress Air Packs (PEAPs) on the flight deck were found to have been activated. Investigators found their remaining unused air supply roughly consistent with the expected consumption during the 2 minute 45 second post-breakup trajectory. While analyzing the wreckage, investigators discovered that several electrical system switches on Pilot Mike Smith's right-hand panel had been moved from their usual launch positions. Fellow Astronaut Richard Mullane wrote, "These switches were protected with lever locks that required them to be pulled outward against a spring force before they could be moved to a new position." Later tests established that neither force of the explosion nor the impact with the ocean could have moved them, indicating that Smith made the switch changes, presumably in a futile attempt to restore electrical power to the cockpit after the crew cabin detached from the rest of the orbiter. Whether the astronauts remained conscious long after the breakup is unknown, and largely depends on whether the detached crew cabin maintained pressure integrity. If it did not, the time of useful consciousness at that altitude is just a few seconds; the PEAPs supplied only unpressurized air, and hence would not have helped the crew to retain consciousness. The cabin hit the ocean surface at roughly 207 mph (333 km/h), with an estimated deceleration at impact of well over 200 g, far beyond the structural limits of the crew compartment or crew survivability levels. The explosion 73 seconds after liftoff claimed crew and vehicle. The cause of explosion was determined to be an o-ring failure in the right solid rocket booster. Cold weather was determined to be a contributing factor.