| FootnoteTV, Footnote Fahrenheit, and more | By Stephen Lee |
The Explosion What caused the explosion? Despite concerns from a major contractor the night before the launch, NASA launched the space shuttle in temperatures too cold for the joints in the solid-fuel rocket boosters to seal properly; a leak developed and an explosion resulted. Space shuttles were designed in four components. There was the Orbiter module that contained the crew cabin and payload bay, the external tank that the shuttle was directly connected to, and the two solid-fuel rocket boosters (SRBs) that connected to the external tank's sides and provided most of the initial thrust at launch. The following diagram is from the Rogers Commission report.   What was the sequence of the launch and explosion? Most of the morning was spent waiting for the temperature to reach the minimum 31ºF necessary as a launchpad team removed ice from the platform (there had even been concerns that the falling ice would hit the shuttle and cause problems). The countdown finally began at 11:29 a.m., and at 11:38:00:010 EST the Challenger began its flight. With a speed of 2,900 feet per second, at 11:39:10 the Challenger was at an altitude of 50,800 feet when a camera showed a glow on one of the rocket boosters. Two seconds later, 73 seconds after launch, the last utterance of any crew member was uttered: co-pilot Michael Smith saying "Uhh ... oh!" Then the shuttle exploded. The two booster rockets began flying in different directions and were then detonated by remote control to prevent crashing into the ground; smoke and debris filled the sky. The Orbiter itself, containing the crew, was not capable of an emergency landing until later stages; two minutes and 45 seconds later after the explosion, the crew cabin hit the waters off Florida at a speed of 200 times the force of normal Earth gravity, hard enough to kill the crew instantly if they had not already died. When did people start suspecting problems with the O-rings? Some people at NASA knew from the planning stages in the late 1970s that the O-rings were less safe than some more expensive alternatives, but specific problems with the O-rings definitely came to light about a year before the fatal launch. The SRBs had been showing scorching after launches, with the worst after a flight in January 1985 (not by coincidence, this flight took place on the coldest launch preceding the Challenger's fatal launch). Thiokol was asked to analyze the scorching and began seeing low temperature as contributing to greater scorching. In July 1985, Marshall Flight Space Center head Lawrence Mulloy issued a "launch constraint" because of the O-ring erosion but waived it on each succeeding flight. Also at this time, Thiokol engineer Roger Boisjoly wrote a letter to his superiors about "my honest and very real fear that if we do not take immediate action to dedicate a team to solving the problem, with the field joint having the number one priority, then we stand in jeopardy of losing a flight." In August 1985, Thiokol and NASA officials held a meeting to discuss the problem but decided to keep with the systems they had in place. Effectively, Thiokol and NASA officials kept recognizing the problem but dismissing it because nothing bad had happened. During public hearings on the explosion, Caltech physicist Richard Feynman described this decision-making process as "a kind of Russian roulette ... You got away with it [before the explosion], but it shouldn't be done over and over again like that." On January 27, 1986, the night before the launch, Boisjoly and other Thiokol engineers tried in two teleconference meetings to persuade Mulloy to delay the launch until the temperature was at least 53ºF (the temperature of the January 1985 launch, the coldest launch preceding the Challenger's final launch). They failed, partly because they could not explain how some launches in warm temperatures also showed some scorching (the crucial fact was not that temperature was the only cause of scorching, but that every single launch in cold temperatures showed damage). Finally, Thiokol management got the engineers to accept a launch recommendation. The launch took place the next morning. Did the Challenger astronauts die instantly and what was the cause of death? We still do not know precisely. The crew cabin did make it through the explosion intact. Because of this, combined with the facts that the force of the explosion was not enough to cause death in and of itself and there may have been some oxygen consumption, some have speculated that the Challenger crew may have survived the immediate explosion. In addition, there is some evidence that copilot Smith's air pack was turned on by another astronaut. But even if the astronauts did not lose consciousness with the explosion, they would have died two minutes and 45 seconds later, when the crew cabin hit the sea at a speed of 204 miles per hour, a force of 200 g (200 times the normal force of gravity). Source: report by Dr. Joseph Kerwin, director of Life Sciences at the Johnson Space Center. Could better graphic-design sensibilities have prevented the explosion? Probably. The Rogers Commission discusses this point indirectly in its five-volume report. It presents a chart of the data that Thiokol engineers used, and then shows what a more detailed chart would have presented. These charts follow; note how adding more data points allows you to see more clearly that warmer temperatures are usually much safer. 
A revised, better version by the Rogers Commission
Background What was the original thinking behind the space shuttle? The Apollo program brought man to the moon (Neil Armstrong did his famous walk on July 20, 1969, and the program continued for several more years and several more landings). After Apollo, NASA wanted to go further and proposed to go to Mars, build a space station, and use a space shuttle. But the country's mood had shifted and the federal government cut back on the space program, leaving only the space shuttle as a means of launching satellites, as long as it was cheap and reusable. NASA developed the space shuttle in the 1970s with an eye always, always on costs, and made decisions that would later come back to haunt the organization. How many shuttle launches had there been before Challenger? The fatal launch was to be the 25th of any of NASA's four space shuttles, and the 10th for Challenger. The first space shuttle, Columbia, went into earth orbit for the first time in April 1981. Challenger itself debuted in 1983, followed by Discovery and Atlantis. After the Challenger explosion, NASA did not launch another shuttle for two-and-a-half years (Discovery launched on September 29, 1988). Who made up the Challenger crew? Seven people, five professional astronauts, one industrial client, and one civilian teacher. Captain Dick Scobee and copilot Michael Smith commanded the mission. Ellison Onizuka, Judith Resnik, Ronald and McNair were mission specialists. Finally, there were Christa McAuliffe (officially a payload specialist) and Greg Jarvis (a payload specialist from NASA client Hughes Aircraft). Not only did this crew contain the first ordinary civilian, but it had two women and two minorities (Onizuka was Hawaiian of Japanese descent, and McNair was black).  Why was a civilian like Christa McAuliffe on board? Politics and public relations. NASA wanted to show that the space shuttle was safe and even routine, and it wanted to rekindle public interest in space exploration. It initially proposed bringing a journalist on board, but the Reagan administration wanted to use a teacher as a symbol of its commitment to education, particularly science education (assuming the launch had gone well, Reagan even planned to talk with her during this State of the Union speech later that night). Thus, NASA began its Teacher-in-Space Program and chose McAuliffe from 11,000 applicants in July 1985. If the program had continued, NASA planned to bring a journalist on board next and then possibly a union representative. How did NASA make its decision to launch and how did it go wrong? This question has spawned much literature in management and systems organization. NASA divided the launch-decision process (otherwise known as a readiness review) into four levels, a structure that was designed to handle small details at lower levels and then bring information together at the end. Here is the structure as drawn in the Rogers Commission report.  The Aftermath What happened in the post-explosion investigation? President Reagan quickly appointed a commission to investigate. The head of the commission was William Rogers, a lawyer who served as Secretary of State for Nixon and as Attorney General for Eisenhower (New York lawyers might know him best as a named partner of the firm then known as Rogers & Wells, now merged into Clifford Chance Rogers & Wells). Neil Armstrong and Sally Ride also served on the commission. But the most important member was Nobel Prize-winning theoretical physicist Richard Feynman, who demonstrated the O-rings' failure to expand properly in cold temperatures before a public hearing and wrote about his experiences (including his frustration with Rogers and admiration for Major General Donald Kutyna) on the commission in his book, What Do You Care What Other People Think? The commission had 120 days to investigate and conducted public hearings, sometimes sparked by media reports of possible causes and earlier warning signs. The five-volume report identified the explosion's causes, criticized management at every level, and made major recommendations for change. It is a major source for the information in this site. What happened afterwards? Several families sued various NASA personnel who had approved the launch, and many of these and other potential claims were settled for reportedly between $2 and 3.5 million per family. Four families settled for around $2.2 million in long-term tax-free annuities, with Morton Thiokol paying 60 percent and the federal government the remainder; others settled for undisclosed amounts believed to be commensurate. Many of the astronauts' wives were also involved in a network of space-education centers. Roger Boisjoly, the Morton Thiokol engineer who tried hardest to delay or abort the launch and who testified to this before Congress, sued Thiokol for personal damages and under a federal whistleblowing statute, but these suits were dismissed (see Boisjoly v. Morton Thiokol, 706 F.Supp 795 (D. Utah 1988)). He left the company, underwent therapy for post-traumatic stress disorder, was awarded the Prize for Scientific Freedom from the American Association for the Advancement of Sciences, and now lectures on workplace ethics issues. Morton Thiokol gave up $10 million from its incentive fee but did not sign a document admitting to legal liability. Transfers and resignations took place in NASA and Thiokol. Several NASA officials involved resigned or were transferred or both. Government pressure on NASA to make the shuttle cost-effective died off (though budgets remained tight), and commercial or military payloads were banned from the shuttle and were instead launched on unmanned rockets, thus easing some of the factors involved in NASA's rush. NASA scaled back its plans for two years and has shifted direction to unmanned, more efficient operations, though I am not capable of fully answering that question at this time. |
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