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The Space Shuttle Challenger disaster was a fatal incident in the United States' space program that occurred on January 28, 1986, when the Space Shuttle Challenger (OV-099) broke apart 73 seconds into its flight, killing all seven crew members aboard. The crew consisted of five NASA astronauts, and two payload specialists. The mission carried the designation STS-51-L and was the tenth flight for the Challenger orbiter.

The spacecraft disintegrated over the Atlantic Ocean, off the coast of Cape Canaveral, Florida, at 11:39 a.m. EST (16:39 UTC). The disintegration of the vehicle began after a joint in its right solid rocket booster (SRB) failed at liftoff. The failure was caused by the failure of O-ring seals used in the joint that were not designed to handle the unusually cold conditions that existed at this launch. The seals' failure caused a breach in the SRB joint, allowing pressurized burning gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB aft field joint attachment hardware and external fuel tank. This led to the separation of the right-hand SRB's aft field joint attachment and the structural failure of the external tank. Aerodynamic forces broke up the orbiter.

The crew compartment and many other vehicle fragments were eventually recovered from the ocean floor after a lengthy search and recovery operation. The exact timing of the death of the crew is unknown; several crew members are known to have survived the initial breakup of the spacecraft. The shuttle had no escape system,[a][1] and the impact of the crew compartment at terminal velocity with the ocean surface was too violent to be survivable.[2]

The disaster resulted in a 32-month hiatus in the Space Shuttle program and the formation of the Rogers Commission, a special commission appointed by United States President Ronald Reagan to investigate the accident. The Rogers Commission found that NASA's organizational culture and decision-making processes had been key contributing factors to the accident,[3] with the agency violating its own safety rules. NASA managers had known since 1977 that contractor Morton-Thiokol's design of the SRBs contained a potentially catastrophic flaw in the O-rings, but they had failed to address this problem properly. NASA managers also disregarded warnings from engineers about the dangers of launching posed by the low temperatures of that morning, and failed to adequately report these technical concerns to their superiors.

Approximately 17 percent of the US population witnessed the launch on live television broadcast because of the presence of high school teacher Christa McAuliffe, who would have been the first teacher in space. Media coverage of the accident was extensive; one study reported that 85 percent of Americans surveyed had heard the news within an hour of the accident.[4] The Challenger disaster has been used as a case study in many discussions of engineering safety and workplace ethics.

NASA and Air Force responseAfter the Challenger accident, further shuttle flights were suspended, pending the results of the Rogers Commission investigation. Whereas NASA had held an internal inquiry into the Apollo 1 fire in 1967, its actions after Challenger were more constrained by the judgment of outside bodies. The Rogers Commission offered nine recommendations on improving safety in the space shuttle program, and NASA was directed by President Reagan to report back within thirty days as to how it planned to implement those recommendations.[75]

When the disaster happened, the Air Force had performed extensive modifications of its Space Launch Complex 6 (SLC-6, pronounced as "Slick Six") at Vandenberg Air Force Base in California, for launch and landing operations of classified Shuttle launches of satellites in polar orbit, and was planning its first polar flight for October 15, 1986. Originally built for the Manned Orbital Laboratory project cancelled in 1969, the modifications were proving problematic and expensive,[76] costing over $4 billion (equivalent to $9.3 billion today). The Challenger loss motivated the Air Force to set in motion a chain of events that finally led to the May 13, 1988, decision to cancel its Vandenberg Shuttle launch plans in favor of the Titan IV uncrewed launch vehicle.

In response to the commission's recommendation, NASA initiated a total redesign of the space shuttle's solid rocket boosters, which was watched over by an independent oversight group as stipulated by the commission.[75] NASA's contract with Space Launch Complex 6 (SLC-6, pronounced as "Slick Six") at Vandenberg Air Force Base in California, for launch and landing operations of classified Shuttle launches of satellites in polar orbit, and was planning its first polar flight for October 15, 1986. Originally built for the Manned Orbital Laboratory project cancelled in 1969, the modifications were proving problematic and expensive,[76] costing over $4 billion (equivalent to $9.3 billion today). The Challenger loss motivated the Air Force to set in motion a chain of events that finally led to the May 13, 1988, decision to cancel its Vandenberg Shuttle launch plans in favor of the Titan IV uncrewed launch vehicle.

In response to the commission's recommendation, NASA initiated a total redesign of the space shuttle's solid rocket boosters, which was watched over by an independent oversight group as stipulated by the commission.[75] NASA's contract with Morton-Thiokol, the contractor responsible for the solid rocket boosters, included a clause stating that in the event of a failure leading to "loss of life or mission", Thiokol would forfeit $10 million (equivalent to $23.3 million today) of its incentive fee and formally accept legal liability for the failure. After the Challenger accident, Thiokol agreed to "voluntarily accept" the monetary penalty in exchange for not being forced to accept liability.[39]:355

NASA also created a new Office of Safety, Reliability and Quality Assurance, headed as the commission had specified by a NASA associate administrator who reported directly to the NASA administrator. George Martin, formerly of Martin Marietta, was appointed to this position.[77] Former Challenger flight director Jay Greene became chief of the Safety Division of the directorate.[78]

The unrealistically optimistic launch schedule pursued by NASA had been criticized by the Rogers Commission as a possible contributing cause to the accident. After the accident, NASA attempted to aim at a more realistic shuttle flight rate: it added another orbiter, Endeavour, to the space shuttle fleet to replace Challenger, and it worked with the Department of Defense to put more satellites in orbit using expendable launch vehicles rather than the shuttle.[79] In August 1986, President Reagan also announced that the shuttle would no longer carry commercial satellite payloads.[79] After a 32-month hiatus, the next shuttle mission, STS-26, was launched on September 29, 1988.

Although changes were made by NASA after the Challenger accident, many commentators have argued that the changes in its management structure and organizational culture were neither deep nor long-lasting.

After the Space Shuttle Columbia disaster in 2003, attention once again focused on the attitude of NASA management towards safety issues. The Columbia Accident Investigation Board (CAIB) concluded that NASA had failed to learn many of the lessons of Challenger. In particular, the agency had not set up a truly independent office for safety oversight; the CAIB decided that in this area, "NASA's response to the Rogers Commission did not meet the Commission's intent".[80] The CAIB believed that "the causes of the institutional failure responsible for Challenger have not been fixed", saying that the same "flawed decision making process" that had resulted in the Challenger accident was responsible for Columbia's destruction seventeen years later.[81]

While the presence of New Hampshire's Christa McAuliffe, a member of the Teacher in Space program, on the Challenger crew had provoked some media interest, there was little live broadcast coverage of the launch. The only live national TV coverage available publicly was provided by CNN.[82] Los Angeles station KNBC also carried the launch with anchor Kent Shocknek describing the tragedy as it happened.[83] Live radio coverage of the launch and explosion was heard on ABC Radio anchored by Vic Ratner and Bob Walker.[84] CBS Radio broadcast the launch live then returned to their regularly scheduled programming just a few seconds before the explosion, necessitating anchor Christopher Glenn to hastily scramble back on the air to report what had happened.[85]

NBC, CBS, and ABC all broke into regular programming shortly after the accident; NBC's John Palmer announced there had

NBC, CBS, and ABC all broke into regular programming shortly after the accident; NBC's John Palmer announced there had been "a major problem" with the launch. Both Palmer and CBS anchor Dan Rather reacted to cameras catching live video of something descending by parachute into the area where Challenger debris was falling with confusion and speculation that a crew member may have ejected from the shuttle and survived. The shuttle had no individual ejection seats or a crew escape capsule. Mission control identified the parachute as a paramedic parachuting into the area but this was also incorrect based on internal speculation at mission control. The chute was the parachute and nose cone from one of the solid rocket boosters which had been destroyed by the range safety officer after the explosion.[86] Due to McAuliffe's presence on the mission, NASA arranged for many US public schools to view the launch live on NASA TV.[87] As a result, many who were schoolchildren in the US in 1986 had the opportunity to view the launch live. After the accident, 17 percent of respondents in one study reported that they had seen the shuttle launch, while 85 percent said that they had learned of the accident within an hour. As the authors of the paper reported, "only two studies have revealed more rapid dissemination [of news]." One of those studies is of the spread of news in Dallas after President John F. Kennedy's assassination, while the other is the spread of news among students at Kent State regarding President Franklin D. Roosevelt's death.[88] Another study noted that "even those who were not watching television at the time of the disaster were almost certain to see the graphic pictures of the accident replayed as the television networks reported the story almost continuously for the rest of the day."[89] Children were even more likely than adults to have seen the accident live, since many children—48 percent of nine- to thirteen-year-olds, according to a New York Times poll—watched the launch at school.[89]

Following the day of the accident, press interest remained high. While only 535 reporters were accredited to cover the launch, three days later there were 1,467 reporters at Kennedy Space Center and another 1,040 at the Johnson Space Center. The event made headlines in newspapers worldwide.[64]

The Challenger accident has frequently been used as a case study in the study of subjects such as engineering safety, the ethics of whistle-blowing, communications, group decision-making, and the dangers of groupthink. It is part of the required readings for engineers seeking a professional license in Canada and other countries.[90] Roger Boisjoly, the engineer who had warned about the effect of cold weather on the O-rings, left his job at Morton-Thiokol and became a speaker on workplace ethics.[91] He argues that the caucus called by Morton-Thiokol managers, which resulted in a recommendation to launch, "constituted the unethical decision-making forum resulting from intense customer intimidation."[92] For his honesty and integrity leading up to and directly following the shuttle disaster, Roger Boisjoly was awarded the Prize for Scientific Freedom and Responsibility from the American Association for the Advancement of Science. Many colleges and universities have also used the accident in classes on the ethics of engineering.[93][94]

Information designer Edward Tufte has claimed that the Challenger accident is an example of the problems that can occur from the lack of clarity in the presentation of information. He argues that if Morton-Thiokol engineers had more clearly presented the data that they had on the relatio

Information designer Edward Tufte has claimed that the Challenger accident is an example of the problems that can occur from the lack of clarity in the presentation of information. He argues that if Morton-Thiokol engineers had more clearly presented the data that they had on the relationship between low temperatures and burn-through in the solid rocket booster joints, they might have succeeded in persuading NASA managers to cancel the launch. To demonstrate this, he took all of the data he claimed the engineers had presented during the briefing, and reformatted it onto a single graph of O-ring damage versus external launch temperature, showing the effects of cold on the degree of O-ring damage. Tufte then placed the proposed launch of Challenger on the graph according to its predicted temperature at launch. According to Tufte, the launch temperature of Challenger was so far below the coldest launch, with the worst damage seen to date, that even a casual observer could have determined that the risk of disaster was severe.[95]

Tufte has also argued that poor presentation of information may have also affected NASA decisions during the last flight of the space shuttle Columbia.[96]

Boisjoly, Wade Robison, a Rochester Institute of Technology professor, and their colleagues have vigorously repudiated Tufte's conclusions about the Morton-Thiokol engineers' role in the loss of Challenger. First, they argue that the engineers didn't have the information available as Tufte claimed: "But they did not know the temperatures even though they did try to obtain that information. Tufte has not gotten the facts right even though the information was available to him had he looked for it."[97] They further argue that Tufte "misunderstands thoroughly the argument and evidence the engineers gave."[97] They also criticized Tufte's diagram as "fatally flawed by Tufte's own criteria. The vertical axis tracks the wrong effect, and the horizontal axis cites temperatures not available to the engineers and, in addition, mixes O-ring temperatures and ambient air temperature as though the two were the same."[97]

The Challenger disaster also provided a chance to see how traumatic events affected children's psyches. The large number of children who saw the accident live or in replays the same day was well known that day, and influenced the speech President Reagan gave that evening.

I want to say something to the schoolchildren of America who were watching the live coverage of the shuttle's takeoff. I know it is hard to understand, but sometimes painful things like this happen. It's all part of the process of exploration and discovery. It's all part of taking a chance and expanding man's horizons. The future doesn't belong to the fainthearted; it belongs to the brave. The Challenger crew was pulling us into the future, and we'll continue to follow them.

At least one psychological study has found that memories of the Challenger explosion were simi

At least one psychological study has found that memories of the Challenger explosion were similar to memories of experiencing single, unrepeated traumas. The majority of children's memories of Challenger were often clear and consistent, and even things like personal placement such as who they were with or what they were doing when they heard the news were remembered well. In one U.S. study, children's memories were recorded and tested again. Children on the East Coast recalled the event more easily than children on the West Coast, due to the time difference. Children on the East Coast either saw the explosion on TV while in school, or heard people talking about it. On the other side of the country, most children were either on their way to school, or just beginning their morning classes. Researchers found that those children who saw the explosion on TV had a more emotional connection to the event, and thus had an easier time remembering it. After one year the children's memories were tested, and those on the East Coast recalled the event better than their West Coast counterparts. Regardless of where they were when it happened, the Challenger explosion was still an important event that many children easily remembered.[98]

After the accident, NASA's Space Shuttle fleet was grounded for almost three years while the investigation, hearings, engineering redesign of the SRBs, and other behind-the-scenes technical and management reviews, changes, and preparations were taking place. At 11:37 on September 29, 1988, Space Shuttle Discovery lifted off with a crew of five, all veteran astronauts,[99] from Kennedy Space Center pad 39-B. Its crew included Richard O. Covey, who had given the last status callout to Challenger before its breakup, "Challenger, go at throttle up". The shuttle carried a Tracking and Data Relay Satellite, TDRS-C (named TDRS-3 after deployment), which replaced TDRS-B, the satellite that was launched and lost on Challenger. The "Return to Flight" launch of Discovery also represented a test of the redesigned boosters, a shift to a more conservative stance on safety (being the first time the crew had launched in pressure suits since STS-4, the last of the four initial Shuttle test flights), and a chance to restore national pride in the American space program, especially crewed space flight. The mission, STS-26, was a success (with only two minor system failures, one of a cabin cooling system and one of a Ku band antenna), and a regular schedule of STS flights followed, continuing without extended interruption until the 2003 Columbia disaster.

Barbara Morgan, the backup for McAuliffe who trained with her in the Teacher in Space program and was at KSC watching her launch on January 28, 1986, flew on STS-118 as a Mission Specialist in August 2007.

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