Space Shuttle Challenger disaster
Disintegration of the entire vehicle began after an O-ring seal in its right solid rocket booster (SRB) failed at liftoff. The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized hot gas from within the solid rocket motor to reach the outside and impinge upon the adjacent SRB attachment hardware and external fuel tank. This led to the separation of the right-hand SRB's aft attachment and the structural failure of the external tank. Aerodynamic forces promptly 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. Although 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. However, the shuttle had no escape system and the astronauts did not survive the impact of the crew compartment with the ocean surface.
The disaster resulted in a 32-month hiatus in the 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 a key contributing factor to the accident. NASA managers had known that contractor Morton Thiokol's design of the SRBs contained a potentially catastrophic flaw in the O-rings since 1977, but they failed to address it properly. They also disregarded warnings from engineers about the dangers of launching posed by the low temperatures of that morning and had failed to adequately report these technical concerns to their superiors. The Rogers Commission offered NASA nine recommendations that were to be implemented before shuttle flights resumed.
Many viewed the launch live due to the presence on the crew of Christa McAuliffe, the first member of the Teacher in Space Project. 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. The Challenger disaster has been used as a case study in many discussions of engineering safety and workplace ethics.
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[edit] Pre-launch conditions and delays
For more details on this topic, see Space Shuttle Challenger launch decision.
The launch was delayed the next day by problems with the exterior access hatch. First, one of the microswitch indicators used to verify that the hatch was safely locked malfunctioned.[1] Then, a stripped bolt prevented the closeout crew from removing a closing fixture from the orbiter's hatch.[2] When the fixture was finally sawn off, crosswinds at the Shuttle Landing Facility exceeded the limits for a Return to Launch Site (RTLS) abort.[3] The crew waited for the winds to die down until the launch window finally ran out, forcing yet another scrub.
Forecasts for January 28 predicted an unusually cold morning, with temperatures close to 31 °F (−1 °C), the minimum temperature permitted for launch. The low temperature had prompted concern from engineers at Morton Thiokol, the contractor responsible for the construction and maintenance of the shuttle's SRBs. At a teleconference on the evening of January 27, Thiokol engineers and managers discussed the weather conditions with NASA managers from Kennedy Space Center and Marshall Space Flight Center. Several engineers—most notably Roger Boisjoly, who had voiced similar concerns previously—expressed their concern about the effect of the temperature on the resilience of the rubber O-rings that sealed the joints of the SRBs. Each SRB was constructed of six sections joined in three factory joints and three "field joints"[citation needed]. The factory joints were welded, but the field joints—assembled in the Vehicle Assembly Building at Kennedy Space Center—each used two rubber O-rings, a primary and a secondary (backup), to seal them. (Since the accident, SRB field joints now use three O-rings.) The seals of all of the SRB joints were required to contain the hot high-pressure gases produced by the burning solid propellant inside, forcing it out the nozzle at the aft end of each rocket. Thiokol engineers argued that if the O-rings were colder than 53 °F (12 °C), they did not have enough data to determine whether the joint would seal properly. This was an important consideration, since the SRB O-rings had been designated as a "Criticality 1" component—meaning that there was no backup if both the primary and secondary O-rings failed, and their failure would destroy the Orbiter and its crew.
One argument of NASA personnel in contest to Thiokol's concerns was that if the primary O-ring failed the secondary O-ring would still seal. This was unproven, and was in any case an illegitimate argument for a Criticality 1 component. (As astronaut Sally Ride cited in questioning NASA managers before the Rogers Commission, it is forbidden to rely on a backup for a Criticality 1 component. The backup is there to provide redundancy in case of unforeseen failure, not to replace the primary device, leaving no backup.) The engineers at Thiokol also argued that the low overnight temperatures (18 degrees F the evening prior to launch) would almost certainly result in SRB temperatures below their redline of 40 °F (4 °C). Ice had accumulated all over the launch pad, raising concerns that ice could damage the shuttle upon lift-off.
However, they were overruled by Morton Thiokol management, who recommended that the launch proceed as scheduled.[4] Despite public perceptions that NASA always maintained a "fail-safe" approach, Thiokol management was influenced by demands from NASA managers that they show it was not safe to launch rather than prove conditions were safe. It later emerged in the aftermath of the accident that NASA managers frequently evaded safety regulations to maintain the launch manifest (schedule).
Due to the low temperature, a significant amount of ice built up on the fixed service structure that stood beside the shuttle. The Kennedy Ice Team inadvertently pointed an infrared camera at the aft field joint of the right SRB and found the temperature to be only 8 °F (−13 °C). This was believed to be the result of supercooled air blowing on the joint from the liquid oxygen tank vent. It was much lower than the air temperature and far below the design specifications for the O-rings. However, the 8 °F (−13 °C) reading was later determined to be erroneous, the error caused by not following the temperature probe manufacturer's instructions. Tests and adjusted calculations later confirmed that the temperature of the joint was not substantially different from the ambient temperature.[5]
Although the Ice Team had worked through the night removing ice, engineers at Rockwell International, the shuttle's prime contractor, still expressed concern. Rockwell engineers watching the pad from their headquarters in Downey, California, were horrified when they saw the amount of ice. They feared that during launch, ice might be shaken loose and strike the shuttle's thermal protection tiles, possibly due to the aspiration induced by the jet of exhaust gas from the SRBs. Rocco Petrone, the head of Rockwell's space transportation division, and his colleagues viewed this situation as a launch constraint, and told Rockwell's managers at the Cape that Rockwell could not support a launch. However, Rockwell's managers at the Cape voiced their concerns in a manner that led Houston-based mission manager Arnold Aldrich to go ahead with the launch. Aldrich decided to postpone the shuttle launch by an hour to give the Ice Team time to perform another inspection. After that last inspection, during which the ice appeared to be melting, Challenger was finally cleared to launch at 11:38 a.m. EST.[4]
[edit] January 28 launch and failure
Further information: STS-51-L Mission timeline
[edit] Liftoff and initial ascent
Until liftoff actually occurs, the Space Shuttle main engines (SSMEs) can be safely shut down and the launch aborted if necessary. At liftoff time (T=0, which was at 11:38:00.010 EST), the three SSMEs were at 100% of their original rated performance, and began throttling up to 104% under computer control. At this moment, the two SRBs were ignited and hold-down bolts were released with explosives, freeing the vehicle from the pad. With the first vertical motion of the vehicle, the gaseous hydrogen vent arm retracted from the External Tank (ET) but failed to latch back. Review of film shot by pad cameras showed that the arm did not re-contact the vehicle, and thus it was ruled out as a contributing factor in the accident.[7] The post-launch inspection of the pad also revealed that kick springs on four of the hold-down bolts were missing, but they were similarly ruled out as a possible cause.[8]
Later review of launch film showed that at T+0.678, strong puffs of dark gray smoke were emitted from the right-hand SRB near the aft strut that attaches the booster to the ET. The last smoke puff occurred at about T+2.733. The last view of smoke around the strut was at T+3.375. It was later determined that these smoke puffs were caused by the opening and closing of the aft field joint of the right-hand SRB. The booster's casing had ballooned under the stress of ignition. As a result of this ballooning, the metal parts of the casing bent away from each other, opening a gap through which hot gases—above 5,000 °F (2,800 °C)—leaked. This had occurred in previous launches, but each time the primary O-ring had shifted out of its groove and formed a seal. Although the SRB was not designed to function this way, it appeared to work well enough, and Morton-Thiokol changed the design specs to accommodate this process, known as extrusion.
Unfortunately, while extrusion was taking place, hot gases would leak past, a process called blow-by, damaging the O-rings until a seal was made. Investigations into the matter by Morton-Thiokol engineers determined that the amount of damage to the O-rings was directly related to the time it took for extrusion to occur, and that cold weather, by causing the O-rings to harden, lengthened the time of extrusion. (The redesigned SRB field joint used subsequent to the Challenger accident uses an additional interlocking mortise and tang with a third O-ring, mitigating blow-by.)
On the morning of the disaster, the primary O-ring had become so hard due to the cold that it couldn't seal in time. The secondary O-ring was not in its seated position due to the metal bending. There was now no barrier to the gases, and both O-rings were vaporized across 70 degrees of arc. However, aluminum oxides from the burned solid propellant sealed the damaged joint, temporarily replacing the O-ring seal before actual flame rushed through the joint.
As the vehicle cleared the tower, the SSMEs were operating at 104% of their rated maximum thrust, and control switched from the Launch Control Center (LCC) at Kennedy to the Mission Control Center (MCC) at Johnson Space Center in Houston, Texas. To prevent aerodynamic forces from structurally overloading the orbiter, at T+28 the SSMEs began throttling down to limit the velocity of the shuttle in the dense lower atmosphere, as per normal operating procedure. At T+35.379, the SSMEs throttled back further to the planned 65%. Five seconds later, at about 5,800 metres (19,000 ft), Challenger passed through Mach 1. At T+51.860, the SSMEs began throttling back up to 104% as the vehicle passed beyond Max Q, the period of maximum aerodynamic pressure on the vehicle.
[edit] Plume
At T+58.788, a tracking film camera captured the beginnings of a plume near the aft attach strut on the right SRB. Unknown to those on Challenger or in Houston, hot gas had begun to leak through a growing hole in one of the right-hand SRB's joints. The force of the wind shear shattered the temporary oxide seal that had taken the place of the damaged O-rings, removing the last barrier to flame rushing through the joint. Had it not been for the wind shear, the fortuitous oxide seal might have held through booster burnout.
Within a second, the plume became well defined and intense. Internal pressure in the right SRB began to drop because of the rapidly enlarging hole in the failed joint, and at T+60.238 there was visual evidence of flame coming through the joint and impinging on the external tank.[6]
At T+64.660, the plume suddenly changed shape, indicating that a leak had begun in the liquid hydrogen tank, located in the aft portion of the external tank. The nozzles of the main engines pivoted under computer control to compensate for the unbalanced thrust produced by the booster burn-through. The pressure in the shuttle's external liquid hydrogen tank began to drop at T+66.764, indicating the effect of the leak.[6]
At this stage the situation still seemed normal both to the astronauts and to flight controllers. At T+68, the CAPCOM Richard Covey informed the crew that they were "go at throttle up", and Commander Dick Scobee confirmed the call. His response, "Roger, go at throttle up," was the last communication from Challenger on the air-to-ground loop.
[edit] Vehicle breakup
At T+72.284, the right SRB apparently pulled away from the aft strut attaching it to the external tank. Later analysis of telemetry data showed a sudden lateral acceleration to the right at T+72.525, which may have been felt by the crew. The last statement captured by the crew cabin recorder came just half a second after this acceleration, when Pilot Michael J. Smith said "Uh oh."[10] Smith may also have been responding to onboard indications of main engine performance, or to falling pressures in the external fuel tank.
At T+73.124, the aft dome of the liquid hydrogen tank failed, producing a propulsive force that pushed the hydrogen tank into the liquid oxygen tank in the forward part of the ET. At the same time, the right SRB rotated about the forward attach strut, and struck the intertank structure.
The breakup of the vehicle began at T+73.162 seconds and at an altitude of 48,000 feet (14.6 km).[11] With the external tank disintegrating (and with the semi-detached right SRB contributing its thrust on an anomalous vector), Challenger veered from its correct attitude with respect to the local air flow and was immediately torn apart by abnormal aerodynamic forces, resulting in a load factor of up to 20 (or 20 g), well over its design limit of 5 g. The two SRBs, which can withstand greater aerodynamic loads, separated from the ET and continued in uncontrolled powered flight for another 37 seconds. The SRB casings were made of half-inch (12.7 mm) thick steel and were much stronger than the orbiter and ET; thus, both SRBs survived the breakup of the space shuttle stack, even though the right SRB was still suffering the effects of the joint burn-through that had set the destruction of Challenger in motion.[8]
[edit] Post-breakup flight controller dialog
At T+110.250, the Range Safety Officer (RSO) at the Cape Canaveral Air Force Station sent radio signals that activated the range safety system's "destruct" packages on board both solid rocket boosters. This was a normal contingency procedure, undertaken because the RSO judged the free-flying SRBs a possible threat to land or sea. The same destruct signal would have destroyed the External Tank had it not already disintegrated.[12]
"Flight controllers here looking very carefully at the situation," reported public affairs officer Steve Nesbitt. "Obviously a major malfunction. We have no downlink." After a pause, Nesbitt said, "We have a report from the Flight Dynamics Officer that the vehicle has exploded."
Greene ordered that contingency procedures be put into effect at Mission Control; these procedures included locking the doors of the control center, shutting down telephone communications with the outside world, and following checklists that ensured that the relevant data were correctly recorded and preserved.
[edit] No "explosion"
[edit] Cause and time of death
The shuttle was designed to withstand a load factor of 3 (or 3 g), with another 1.5 g safety factor built in.[13] The crew cabin in particular is a very robust section of the shuttle because of its design and construction of reinforced aluminum.[13] 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. 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.[14]
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.[11]
“Scob fought for any and every edge to survive. He flew that ship without wings all the way down....they were alive”
Robert Overmyer, NASA Lead Investigator[13]
Some experts, including one of NASA's lead investigators Robert Overmyer, believed most if not all of the crew were alive and possibly conscious during the entire descent until impact with the ocean.[13]The findings are inconclusive. The impact of the crew compartment with the ocean surface was so violent that evidence of damage occurring in the seconds which followed the disintegration was masked. Our final conclusions are:
- the cause of death of the Challenger astronauts cannot be positively determined;
- the forces to which the crew were exposed during Orbiter breakup were probably not sufficient to cause death or serious injury; and
- the crew possibly, but not certainly, lost consciousness in the seconds following Orbiter breakup due to in-flight loss of crew module pressure.[11]
[edit] Crew escape was not possible
Further information: Shuttle ejection escape systems, Post-Challenger abort enhancements
During powered flight of the space shuttle, crew escape was not possible. While launch escape systems were considered several times during shuttle development, NASA's conclusion was that the shuttle's expected high reliability would preclude the need for one. Modified SR-71 Blackbird ejection seats and full pressure suits were used on the first four shuttle orbital missions, which were considered test flights, but they were removed for the "operational" missions that followed. (The CAIB later declared, after the 2003 Columbia re-entry disaster, that the space shuttle system should never have been declared operational because it is experimental by nature due to the limited number of flights as compared to certified commercial aircraft.) Providing a launch escape system for larger crews was considered undesirable due to "limited utility, technical complexity and excessive cost in dollars, weight or schedule delays."[15]After the loss of Challenger the question was re-opened, and NASA considered several different options, including ejector seats, tractor rockets and bailing out through the bottom of the orbiter. However, NASA once again concluded that all of the launch escape systems considered would be impractical due to the sweeping vehicle modifications that would have been necessary and the resultant limitations on crew size. A system was designed to give the crew the option to leave the shuttle during gliding flight; however, this system would not have been usable in the Challenger situation.[16]
[edit] Aftermath
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[edit] Tributes
On the night of the disaster, President Ronald Reagan had been scheduled to give his annual State of the Union Address. He initially announced that the address would go on as scheduled, but then postponed the State of the Union Address for a week and instead gave a national address on the Challenger disaster from the Oval Office of the White House. It was written by Peggy Noonan, and finished with the following statement, which quoted from the poem "High Flight" by John Gillespie Magee, Jr.:| “ | We will never forget them, nor the last time we saw them, this morning, as they prepared for their journey and waved goodbye and 'slipped the surly bonds of Earth' to 'touch the face of God.'[17] | ” |
| “ | Sometimes, when we reach for the stars, we fall short. But we must pick ourselves up again and press on despite the pain.[18] | ” |
The families of the Challenger crew organized the Challenger Center for Space Science Education as a permanent memorial to the crew. Fifty-two learning centers have been established by this non-profit organization.
In Huntsville, Alabama, a city known for its strong association with NASA, the newest[clarification needed] public middle school in the Huntsville City Schools system was named Challenger Middle School. The City of Palmdale, the birthplace of the entire shuttle fleet, and its neighbor City of Lancaster, California, both renamed 10th Street East, from Avenue M to Edwards Air Force Base, to Challenger Way in honor of the lost shuttle and its crew. This was the road that the Challenger, Enterprise, and Columbia all were towed along in their initial move from U.S. Air Force Plant 42 to Edwards AFB after completion since Palmdale airport had not yet installed the shuttle crane for placement of an orbiter on the 747 Shuttle Carrier Aircraft. In addition, the City of Lancaster has built Challenger Middle School, and Challenger Memorial Hall at the former site of the Antelope Valley Fairgrounds, all in tribute to the Challenger shuttle and crew.
In 1987, the TV series Star Trek: The Next Generation began. In two of its episodes, a shuttlecraft dubbed Onizuka was featured, named after Ellison Onizuka.
In March 1986, NBC aired the second season finale of Punky Brewster, which saw Punky, who was dreaming to be an astronaut, and her class, trying to deal with the Challenger tragedy, after watching the launch in school. The episode was immediately scripted soon after the crash, as NBC executives knew a lot of children would be devastated by the loss of Christa McAuliffe, a teacher, as the launch was shown in many schools.
In Cocoa, Brevard County, FL (the county Cape Canaveral, and KSC is located), Challenger 7 Middle School is named in memory of the seven astronauts who lost their lives. A middle school in Boynton Beach, Florida is named after deceased teacher/astronaut, Christa McAuliffe. The McAuliffe-Shepard Discovery Center, a science museum and planetarium in Concord, New Hampshire, is also partly named in her honor.
In 2004, President George W. Bush conferred posthumous Congressional Space Medals of Honor to all 14 astronauts lost in the Challenger and Columbia accidents.
In the 2002 space based MMORPG created by Westwood, "Earth & Beyond" there were memorials in the Glory's Orbit sector for Apollo 1, the Challenger, and the Columbia.
[edit] Recovery of debris
In the first minutes after the accident, recovery efforts were begun by NASA's Launch Recovery Director, who ordered the ships used by NASA for recovery of the solid rocket boosters to be sent to the location of the water impact. Search and rescue aircraft were also dispatched. At this stage, however, debris was still falling, and the Range Safety Officer (RSO) held both aircraft and ships out of the impact area until it was considered safe for them to enter. It was about an hour until the RSO allowed the recovery forces to begin their work.[22]The search and rescue operations that took place in the first week after the Challenger accident were managed by the Department of Defense on behalf of NASA, with assistance from the United States Coast Guard, and mostly involved surface searches. According to the Coast Guard, "the operation was the largest surface search in which they had participated."[22] This phase of operations lasted until February 7. Thereafter, recovery efforts were managed by a Search, Recovery, and Reconstruction team; its aim was to salvage debris that would help in determining the cause of the accident. Sonar, divers, remotely operated submersibles and manned submersibles were all used during the search, which covered an area of 480 square nautical miles (1,600 kilometres (990 mi)²), and took place at depths of up to 370 metres (1,210 ft). On March 7, divers from the USS Preserver identified what might be the crew compartment on the ocean floor.[23][24] The finding, along with discovery of the remains of all seven crew members, was confirmed the next day and on March 9, NASA announced the finding to the press.[25]
On board Challenger was an American flag, dubbed the Challenger flag, that was sponsored by Boy Scout Troop 514 of Monument, Colorado. It was recovered intact, still sealed in its plastic container.[29]
[edit] Funeral ceremonies
[edit] Investigation
In the aftermath of the accident, NASA was criticized for its lack of openness with the press. The New York Times noted on the day after the accident that "neither Jay Greene, flight director for the ascent, nor any other person in the control room, was made available to the press by the space agency".[31] In the absence of reliable sources, the press turned to speculation; both the New York Times and United Press International ran stories suggesting that a fault with the space shuttle external tank had caused the accident, despite the fact that NASA's internal investigation had quickly focused in on the solid rocket boosters.[32][33] "The space agency," wrote space reporter William Harwood, "stuck to its policy of strict secrecy about the details of the investigation, an uncharacteristic stance for an agency that long prided itself on openness."[32][edit] Rogers Commission
Main article: Rogers Commission
More broadly, the report also considered the contributing causes of the accident. Most salient was the failure of both NASA and Morton Thiokol to respond adequately to the danger posed by the deficient joint design. However, rather than redesigning the joint, they came to define the problem as an acceptable flight risk. The report found that managers at Marshall had known about the flawed design since 1977, but never discussed the problem outside their reporting channels with Thiokol—a flagrant violation of NASA regulations. Even when it became more apparent how serious the flaw was, no one at Marshall considered grounding the shuttles until a fix could be implemented. On the contrary, Marshall managers went as far as to issue and waive six launch constraints related to the O-rings.[35] The report also strongly criticized the decision making process that led to the launch of Challenger, saying that it was seriously flawed.[36]
| “ | ...failures in communication... resulted in a decision to launch 51-L based on incomplete and sometimes misleading information, a conflict between engineering data and management judgments, and a NASA management structure that permitted internal flight safety problems to bypass key Shuttle managers.[37] | ” |
[edit] U.S. House Committee hearings
The U.S. House Committee on Science and Technology also conducted hearings, and on October 29, 1986 released its own report on the Challenger accident.[40] The committee reviewed the findings of the Rogers Commission as part of its investigation, and agreed with the Rogers Commission as to the technical causes of the accident. However, it differed from the committee in its assessment of the accident's contributing causes.| “ | ...the Committee feels that the underlying problem which led to the Challenger accident was not poor communication or underlying procedures as implied by the Rogers Commission conclusion. Rather, the fundamental problem was poor technical decision-making over a period of several years by top NASA and contractor personnel, who failed to act decisively to solve the increasingly serious anomalies in the Solid Rocket Booster joints.[41] | ” |
[edit] NASA response
After 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 judgement 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.[42]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.[42] 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 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.[43]
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.[44] Former Challenger flight director Jay Greene became chief of the Safety Division of the directorate.[45]
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.[46] In August 1986, President Reagan also announced that the shuttle would no longer carry commercial satellite payloads. After a 32-month hiatus, the next shuttle mission, STS-26, was launched on September 29, 1988.
Although significant 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 felt that in this area, "NASA's response to the Rogers Commission did not meet the Commission's intent".[47] 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.[48]
[edit] Media coverage
While the presence of New Hampshire schoolteacher Christa McAuliffe 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; although several radio networks were also live. Due to McAuliffe's presence on the mission, NASA arranged for many U.S. public schools to view the launch live on NASA TV.[49] As a result, many who were schoolchildren in the US in 1986 did in fact have the opportunity to view the launch live. After the accident, however, 17% of respondents in one study reported that they had seen the shuttle launch, while 85% 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 was of the spread of news in Dallas after President Kennedy's assassination, while the other was the spread of news among students at Kent State regarding President Franklin D. Roosevelt's death.)[50] 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."[51] Children were even more likely than adults to have seen the accident live, since many children—forty-eight percent of nine to thirteen-year-olds, according to a New York Times poll—watched the launch at school.[51]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 1467 reporters at Kennedy Space Center and another 1040 at Johnson Space Center. The event made headlines in newspapers worldwide.[32]
[edit] Use as case study
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[52] and other countries. 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.[53] 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."[54] 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.[55][56]Information designer Edward Tufte has used the Challenger accident as 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.[57] Tufte has also argued that poor presentation of information may have affected NASA decisions during the last flight of Columbia.[58]
[edit] Continuation of the Shuttle Program
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 a.m. on September 29, 1988, Space Shuttle Discovery lifted off with a crew of five[59] from Kennedy Space Center pad 39-B. It 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 (e.g., it was 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 manned 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 astronaut 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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