On January 28, 1986, Space Shuttle Challenger broke apart 73 seconds into its flight, killing all seven crew members. The spacecraft disintegrated about On January 28, 1986, Space Shuttle Challenger broke apart 73 seconds into its flight, killing all seven crew members. The spacecraft disintegrated about 46,000 feet (14 km) above the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 16:39:13 UTC (11:39:13 a.m. EST, local time at the launch site). It was the first fatal accident involving an American spacecraft while in flight. The missi On… On January 28, 1986, Space Shuttle Challenger broke apart 73 seconds into its flight, killing all seven crew members. The spacecraft disintegrated about 46,000 feet (14 km) above the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 16:39:13 UTC (11:39:13 a.m. EST, local time at the launch site). It was the first fatal accident involving an American spacecraft while in flight. The mission, designated STS-51-L, was the 10th flight for the orbiter and the 25th flight of the NASA's Space Shuttle program. The crew was scheduled to deploy a commercial communications satellite and study Halley's Comet while they were in orbit, in addition to taking schoolteacher Christa McAuliffe into space under the Teacher in Space Project. This latter task resulted in a higher-than-usual media interest in and coverage of the mission, and the launch and subsequent disaster were seen live in many schools across the United States. The cause of the disaster was the failure of the primary and secondary O-ring seals in a joint in the right Space Shuttle Solid Rocket Booster (SRB). The record-low temperatures on the morning of the launch had stiffened the rubber O-rings, reducing their ability to seal the joints. Shortly after liftoff the seals were breached, and hot pressurized gas from within the SRB leaked through the joint and burned through the aft attachment strut connecting it to the external propellant tank (ET), then into the tank itself. The collapse of the ET's internal structures and the rotation of the SRB that followed propelled the shuttle stack, traveling at a speed of Mach 1.92, into a direction that allowed aerodynamic forces to tear the orbiter apart. Both SRBs detached from the now-destroyed ET and continued to fly uncontrollably until the range safety officer (RSO) sent a signal to destroy them. The crew compartment containing human remains, and many other fragments from the shuttle, were recovered from the ocean floor after a three-month search and recovery operation. The exact timing of the deaths of the crew is not known, but several crew members are thought to have survived the initial breakup of the spacecraft. The orbiter had no escape system, and the impact of the crew compartment at terminal velocity with the ocean surface was too violent to be survivable. The disaster resulted in a 32-month hiatus in the Space Shuttle program. President Ronald Reagan created the Rogers Commission to investigate the accident. The commission criticized NASA's organizational culture and decision-making processes that had contributed to the accident. Test data since 1977 had demonstrated a potentially catastrophic flaw in the SRBs' O-rings, but neither NASA nor SRB manufacturer Morton Thiokol had addressed this known defect. NASA managers also disregarded engineers' warnings about the dangers of launching in low temperatures and did not report these technical concerns to their superiors. As a result of this disaster, NASA established the Office of Safety, Reliability, and Quality Assurance, and arranged for deployment of commercial satellites from expendable launch vehicles, rather than from a crewed orbiter. The construction of a new Space Shuttle orbiter, Endeavour, was approved in 1987 to replace Challenger, and the new orbiter first flew in 1992. Subsequent missions were launched with redesigned SRBs and their crews wore pressurized suits during ascent and reentry. In February 2003 the Space Shuttle Columbia disintegrated during re-entry. The Columbia Accident Investigation Board concluded that NASA had failed to learn lessons from the Challenger disaster, which resulted in the second disaster. At T+72.284, the right SRB pulled away from the aft strut that attached it to the ET, causing lateral acceleration that was felt by the crew. At the same time, pressure in the LH2 tank began dropping. Pilot Mike Smith said "Uh-oh", which was the last crew comment recorded. At T+73.124, white vapor was seen flowing away from the ET, after which the aft dome of the LH2 tank fell off. The resulting release and ignition of all liquid hydrogen in the tank pushed the LH2 tank forward into the liquid oxygen (LOX) tank with a force equating to roughly 3,000,000 pounds (13 MN), while the right SRB collided with the intertank structure. The failure of the LH2 and LOX tanks resulted in a boiling liquid expanding vapor explosion (BLEVE), with a large part of the liquid evaporating back into gas almost instantly. These events resulted in an abrupt change to the shuttle stack's attitude and direction, which was shrouded from view by the vaporized contents of the now-destroyed ET. As it traveled at Mach 1.92, Challenger took aerodynamic forces it was not designed to withstand and broke into several large pieces: a wing, the (still firing) main engines, the crew cabin and hypergolic fuel leaking from the ruptured reaction control system were among the parts identified exiting the vapor cloud. The disaster unfolded at an altitude of 46,000 feet (14 km). Both SRBs survived the breakup of the shuttle stack and continued flying, now unguided by the attitude and trajectory control of their mothership, until their flight termination systems were activated at T+110. The debris from the SRBs was widely distributed due to the detonation of their linear shaped charges. The identification of SRB material was primarily conducted by crewed submarines and submersibles. The