Space Shuttle Challenger disaster

Forecasts for January 28 predicted an unusually cold morning, with temperatures close to −1 °C (30 °F), the minimum temperature permitted for launch. The Shuttle was never certified to operate in temperatures that low. The O-rings, as well as many other critical components, had no test data to support any expectation of a successful launch in such conditions.[14][15]

By mid-1985, Thiokol engineers worried that others did not share their concerns about the low temperature effects on the boosters. Engineer Bob Ebeling in October 1985 wrote a memo—titled "Help!" so others would read it—of concerns regarding low temperatures and O-rings. After the weather forecast, NASA personnel remembered Thiokol's warnings and contacted the company. When a Thiokol manager asked Ebeling about the possibility of a launch at 18 °F (−8 °C), he answered "[W]e're only qualified to 40° [40 °F or 4 °C] ... 'what business does anyone even have thinking about 18°, we're in no-man's land.'" After his team agreed that a launch risked disaster, Thiokol immediately called NASA recommending a postponement until temperatures rose in the afternoon. NASA manager Jud Lovingood responded that Thiokol could not make the recommendation without providing a safe temperature. The company prepared for a teleconference two hours later during which it would have to justify a no-launch recommendation.[14][15]

At the 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 Allan McDonald, Ebeling and Roger Boisjoly) reiterated their concerns about the effect of low temperatures on the resilience of the rubber O-rings that sealed the joints of the SRBs, and recommended a launch postponement.[15] They argued that they did not have enough data to determine whether the joints would properly seal if the O-rings were colder than 54 °F (12 °C). 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 could destroy the Orbiter and kill its crew.

Thiokol management initially supported its engineers' recommendation to postpone the launch, but NASA staff opposed a delay. During the conference call, Hardy told Thiokol, "I am appalled. I am appalled by your recommendation." Mulloy said, "My God, Thiokol, when do you want me to launch—next April?"[15] NASA believed that Thiokol's hastily prepared presentation's quality was too poor to support such a statement on flight safety.[14] One argument by NASA personnel contesting 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 argument that did not apply to a "Criticality 1" component. As astronaut Sally Ride stated when questioning NASA managers before the Rogers Commission, it is forbidden to rely on a backup for a "Criticality 1" component.

NASA claimed that it did not know of Thiokol's earlier concerns about the effects of the cold on the O-rings, and did not understand that Rockwell International, the shuttle's prime contractor, additionally viewed the large amount of ice present on the pad as a constraint to launch.

According to Ebeling, a second conference call was scheduled with only NASA and Thiokol management, excluding the engineers. For reasons that are unclear, Thiokol management disregarded its own engineers' warnings and now recommended that the launch proceed as scheduled;[15][16] NASA did not ask why.[14] Ebeling told his wife that night that Challenger would blow up.[17]

Ken Iliff, a former NASA Chief Scientist who had worked on the Space Shuttle program since its first mission (and the X-15 program before that), stated this in 2004:

Not violating flight rules was something I had been taught on the X-15 program. It was something that we just never did. We never changed a mission rule on the fly. We aborted the mission and came back and discussed it. Violating a couple of mission rules was the primary cause of the Challenger accident.[18]

Ice on the launch tower hours before Challenger launch

The Thiokol engineers had also argued that the low overnight temperatures of 18 °F (−8 °C) projected on the day[16] prior to launch would almost certainly result in SRB temperatures below their redline of 39 °F (4 °C). Ice had accumulated all over the launch pad, raising concerns that ice could damage the shuttle upon lift-off. 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 9 °F (−13 °C). This was believed to be the result of supercooled air blowing on the joint from the liquid oxygen (LOX) tank vent. It was much lower than the air temperature and far below the design specifications for the O-rings. The low 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.

The temperature on the day of the launch was far lower than had been the case with previous launches: below freezing at 28.0 to 28.9 °F (−2.2 to −1.7 °C); previously, the coldest launch had been at 54 °F (12 °C). Although the Ice Team had worked through the night removing ice, engineers at Rockwell 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. 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 cleared to launch at 11:38 am EST.[16]

Gray smoke escaping from the right-side solid rocket booster

The following account of the accident is derived from real time telemetry data and photographic analysis, as well as from transcripts of air-to-ground and mission control voice communications.[19] All times are given in seconds after launch and correspond to the telemetry time-codes from the closest instrumented event to each described event.[20]

The Space Shuttle main engines (SSMEs) were ignited at T −6.6 seconds. The SSMEs were liquid-fueled and could be safely shut down (and the launch aborted if necessary) until the solid rocket boosters (SRBs) ignited at T=0 (which was at 11:38:00.010 EST) and the hold-down bolts were released with explosives, freeing the vehicle from the pad. At lift off, the three SSMEs were at 100% of their original rated performance, and began throttling up to 104% under computer control. 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.[20] 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.[21]

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 attached 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 (2,760 °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.

While extrusion was taking place, hot gases leaked past (a process called "blow-by"), damaging the O-rings until a seal was made. Investigations 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 used 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 could not seal in time. The temperature had dropped below the glass transition temperature of the O-rings. Above the glass transition temperature, the O-rings display properties of elasticity and flexibility, while below the glass transition temperature, they become rigid and brittle. 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. Aluminum oxides from the burned solid propellant sealed the damaged joint, temporarily replacing the O-ring seal before flame passed 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, per normal operating procedure. At T+35.379, the SSMEs throttled back further to the planned 65%. Five seconds later, at about 19,000 feet (5,800 m), 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.

Plume on right SRB at T+ 58.788 seconds

Beginning at about T+37 and for 27 seconds, the shuttle experienced a series of wind shear events that were stronger than on any previous flight.[22]

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 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 passing 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 burning through the joint and impinging on the external tank.[19]

At T+64.660, the plume suddenly changed shape, indicating that a leak had begun in the liquid hydrogen (LH2) 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 LH2 tank began to drop at T+66.764, indicating the effect of the leak.[19]

At this stage the situation still seemed normal both to the crew and to flight controllers. At T+68, the CAPCOM Richard O. Covey informed the crew that they were "go at throttle up", and Commander Dick Scobee confirmed, "Roger, go at throttle up"; this was the last communication from Challenger on the air-to-ground loop.[19]

Challenger begins to disintegrate

At T+72.284, the right SRB 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."[23] 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 rammed the hydrogen tank into the LOX 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 external tank at this point suffered a complete structural failure, the LH2 and LOX tanks rupturing, mixing, and igniting, creating a fireball that enveloped the whole stack.[24]

The breakup of the vehicle began at T+73.162 seconds and at an altitude of 48,000 feet (15 km).[25] 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 airflow, resulting in a load factor of up to 20 g, well over its design limit of 5 g and was quickly ripped apart by abnormal aerodynamic forces (the orbiter did not explode as is often suggested, as the force of the external tank breakup was well within its structural limits). The two SRBs, which could withstand greater aerodynamic loads, separated from the ET and continued in uncontrolled powered flight. The SRB casings were made of half-inch-thick (12.7 mm) 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.[21]

The more robustly constructed crew cabin also survived the breakup of the launch vehicle, as it was designed to survive 20 psi (140 kPa) while the estimated pressure it had been subjected to during orbiter breakup was only about 4–5 psi (28–34 kPa). While the SRBs were remotely ordered destroyed by the Range Safety Officer, the detached cabin continued along a ballistic trajectory and was observed exiting the cloud of gases at T+75.237.[21] Twenty-five seconds after the breakup of the vehicle, the altitude of the crew compartment peaked at a height of 65,000 feet (20 km).[25] The cabin was stabilized during descent by the large mass of electrical wires trailing behind it. At T+76.437 the nose caps and drogue parachutes of the SRBs separated, as designed, and the drogue of the right-hand SRB was seen by a tracking camera, bearing the frustum and its location aids.[26]

The Thiokol engineers, who had opposed the decision to launch, were watching the events on television. They had believed that any O-ring failure would have occurred at liftoff, and thus were happy to see the shuttle successfully leave the launch pad. At about one minute after liftoff, a friend of Boisjoly said to him "Oh God. We made it. We made it!" Boisjoly recalled that when the shuttle was destroyed a few seconds later, "we all knew exactly what happened".[15] Veteran astronaut Robert Crippen was preparing to command STS-62-A, scheduled for mid-year, when his crew stopped training to watch the launch. Pete Aldridge recalled, "I was waiting for the orbiter, as we all were, to come out of the smoke. But as soon as that explosion occurred, Crippen obviously knew what it was. His head dropped. I remember this so distinctly".[27]

Jay Greene at his console after the breakup of Challenger

In Mission Control, there was a burst of static on the air-to-ground loop as Challenger disintegrated. Television screens showed a cloud of smoke and water vapor (the product of hydrogen+oxygen combustion) where Challenger had been, with pieces of debris falling toward the ocean. At about T+89, flight director Jay Greene prompted his Flight Dynamics Officer (FIDO) for information. FIDO responded that "the [radar] filter has discreting sources", a further indication that Challenger had broken into multiple pieces. Moments later, the Ground Control Officer reported "negative contact (and) loss of downlink" of radio and telemetry data from Challenger. Greene ordered his team to "watch your data carefully" and look for any sign that the Orbiter had escaped.

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.[28] The SRBs were close to the end of their scheduled burn (110 seconds after launch) and had nearly exhausted their propellants when the destruct command was sent, so very little, if any, explosive force was generated by this event.

Public affairs officer Steve Nesbitt reported: "Flight controllers here are looking very carefully at the situation. Obviously a major malfunction. We have no downlink."[19]

On the Mission Control loop, Greene ordered that contingency procedures be put into effect; 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.[29]

Nesbitt relayed this information to the public: "We have a report from the Flight Dynamics Officer that the vehicle has exploded. The flight director confirms that. We are looking at checking with the recovery forces to see what can be done at this point."[19]

The crew cabin after breakup, indicated by the arrow

The crew cabin was made of particularly robust reinforced aluminum and detached in one piece from the rest of the orbiter.[30] At the time of separation, the maximum acceleration is estimated to have been between 12 and 20 g. During vehicle breakup, the cabin detached in one piece and slowly tumbled into a ballistic arc. Within two seconds after breakup the cabin had dropped below 4 g, and was in free fall within 10 seconds. The forces involved at this stage were probably insufficient to cause major injury to the crew.[25]

At least some of the crew were alive and at least briefly conscious after the breakup, as three of the four recovered Personal Egress Air Packs (PEAPs) on the flight deck were found to have been activated.[25] PEAPs were activated for Smith[31] and two unidentified crewmembers, but not for Scobee.[25] The PEAPs were not intended for in-flight use, and the astronauts never trained with them for an in-flight emergency. The location of Smith's activation switch, on the back side of his seat, indicated that either Resnik or Onizuka likely activated it for him. Investigators found their remaining unused air supply consistent with the expected consumption during the post-breakup trajectory.[31]^:245–247

While analyzing the wreckage, investigators discovered that several electrical system switches on Smith's right-hand panel had been moved from their usual launch positions. The switches had lever locks on top of them that were required to be pulled out before the switch could be moved. Later tests established that neither the 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.[31]^:245

On July 28, 1986, NASA's Associate Administrator for Space Flight, former astronaut Richard H. Truly, released a report on the deaths of the crew from physician and Skylab 2 astronaut Joseph P. Kerwin. Kerwin's report concluded that it is unknown whether the crew remained conscious until ocean impact, because it is unknown whether the crew cabin remained pressurized. Depressurization would have caused the crew to quickly lose consciousness, as the PEAPs supplied only unpressurized air. Pressurization could have enabled consciousness for the entire fall until impact. The crew cabin hit the ocean surface at 207 mph (333 km/h) approximately two minutes and 45 seconds after breakup. The estimated deceleration was 200 g, far exceeding structural limits of the crew compartment or crew survivability levels. The middeck floor had not suffered buckling or tearing, as would result from a rapid decompression, but stowed equipment showed damage consistent with decompression, and debris was embedded between the two forward windows that may have caused a loss of pressure. Impact damage to the crew cabin was severe enough that it could not be determined if the crew cabin had been previously damaged enough to lose pressurization.[25]

During powered flight of the Space Shuttle, crew escape was not possible. Launch escape systems were considered several times during shuttle development, but 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 for the two-man crews on the first four shuttle orbital missions, which were considered test flights, but they were removed for the "operational" missions that followed. The Columbia Accident Investigation Board 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. The multideck design of the crew cabin precluded use of such ejection seats for larger crews. Providing some sort of launch escape system had been considered, but deemed impractical due to "limited utility, technical complexity and excessive cost in dollars, weight or schedule delays".[28][lower-alpha 1]

After the loss of Challenger, the question was reopened, and NASA considered several different options, including ejector seats, tractor rockets, and emergency egress through the bottom of the orbiter. 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, but this system would not have been usable in the Challenger situation.[32]

Wikisource has original text related to this article: Ronald Reagan Announces the Challenger Disaster

President Ronald Reagan had been scheduled to give the 1986 State of the Union Address on the evening of the Challenger disaster. After a discussion with his aides, Reagan postponed the State of the Union, and instead addressed the nation about the disaster from the Oval Office of the White House. Reagan's national address was written by Peggy Noonan, and was listed as one of the most significant speeches of the 20th century in a survey of 137 communication scholars.[33][34] It 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.'[35]

Memorial service on January 31, 1986, at Houston, Texas, attended by President Reagan and First Lady Nancy Reagan (left)

Three days later, Ronald and Nancy Reagan traveled to the Johnson Space Center to speak at a memorial service honoring the crew members, where he stated:

Sometimes, when we reach for the stars, we fall short. But we must pick ourselves up again and press on despite the pain.[36]

It was attended by 6,000 NASA employees and 4,000 guests,[37][38] as well as by the families of the crew.[39]^:17 During the ceremony, an Air Force band led the singing of "God Bless America" as NASA T-38 Talon jets flew directly over the scene, in the traditional missing-man formation.[37][38] All activities were broadcast live by the national television networks.[37]

Rumors surfaced in the weeks after the disaster that the White House itself had pressed for Challenger to launch before the scheduled January 28 State of the Union address, because Reagan had intended to mention the launch in his remarks.[40] Three weeks before the State of the Union address was to have been given, NASA did suggest that Reagan make callouts to the assumed successful Challenger launch, and to mention Christa McAuliffe's shuttle voyage as "'the ultimate field trip' of an American schoolteacher".[40] In March 1986, The White House released a copy of the original State of the Union speech as it would have been given before the disaster. In that speech, Reagan intended to mention an X-ray experiment launched on Challenger and designed by a guest he'd invited to the address, but he did not plan any other specific discussion about the launch or NASA in the address.[40][41] Inclusion of extensive discussion of NASA, the launch, or McAuliffe in the State of the Union address effectively stopped at the desk of Cabinet Secretary Alfred H. Kingon.[40] In the rescheduled State of the Union address on February 4, President Reagan did mention the deceased Challenger crew members, and modified his remarks about the X-ray experiment as "launched and lost".

In the first minutes after the accident, recovery efforts were begun by NASA's Launch Recovery Director, who ordered the ships normally 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, since debris was still falling, 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.[42]

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."[42] This phase of operations lasted until February 7. In order to discourage scavengers, NASA did not disclose the exact location of the debris field and insisted on secrecy, utilizing code names such as "Target 67" to refer to the crew cabin and "Tom O'Malley" to refer to any crew remains.[43] Radio Shack stores in the Cape Canaveral area were soon completely sold out of radios that could tune into the frequency used by Coast Guard vessels.[43] 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 crewed submersibles were all used during the search, which covered an area of 486 square nautical miles (1,670 km²), and took place at water depths between 70 feet (21 m) and 1,200 feet (370 m).[44] On March 7, divers from the USS Preserver identified what might be the crew compartment on the ocean floor.[45][46] 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.[47] The crew cabin was severely crushed and fragmented from the extreme impact forces; one member of the search team described it as "largely a pile of rubble with wires protruding from it". The largest intact section was the rear wall containing the two payload bay windows and the airlock. All windows in the cabin had been destroyed, with only small bits of glass still attached to the frames. Impact forces appeared to be greatest on the left side, indicating that it had struck the water in a nose-down, left-end-first position.

Recovered right solid rocket booster showing the hole caused by the plume

Inside the twisted debris of the crew cabin were the bodies of the astronauts which, after weeks of immersion in salt water and exposure to scavenging marine life, were in a "semi-liquefied state that bore little resemblance to anything living". However, according to John Devlin, the skipper of the USS Preserver, they "were not as badly mangled as you'd see in some aircraft accidents". Lt. Cmdr James Simpson of the Coast Guard reported finding a helmet with ears and a scalp in it.[48] Judith Resnik was the first to be removed, followed by Christa McAuliffe, with more remains retrieved over several hours. Due to the hazardous nature of the recovery operation (the cabin was filled with large pieces of protruding jagged metal), the Navy divers protested that they would not go on with the work unless the cabin was hauled onto the ship's deck.

During the recovery of the remains of the crew, Gregory Jarvis's body floated out of the shattered crew compartment and was lost to the diving team. A day later, it was seen floating on the ocean's surface. It sank as a team prepared to pull it from the water. Determined not to end the recovery operations without retrieving Jarvis, Crippen rented a fishing boat at his own expense and went searching for the body. On April 15, near the end of the salvage operations, the Navy divers found Jarvis. His body had settled to the sea floor, 101.2 feet (30.8 m) below the surface, some 0.7 nautical miles (1.3 km; 0.81 mi) from the final resting place of the crew compartment. The body was recovered and brought to the surface before being processed with the other crew members and then prepared for release to Jarvis's family.[49]

Navy pathologists performed autopsies on the crew members, but due to the poor condition of the bodies, the exact cause of death could not be determined for any of them. The crew transfer took place on April 29, 1986, three months and one day after the accident. Seven hearses carried the crew's remains from the Life Sciences Facility on Cape Canaveral to a waiting MAC C-141 aircraft. Their caskets were each draped with an American flag and carried past an honor guard and followed by an astronaut escort. The astronaut escorts for the Challenger crew were Dan Brandenstein, James Buchli, Norm Thagard, Charles Bolden, Tammy Jernigan, Dick Richards, and Loren Shriver. Once the crew's remains were aboard the jet, they were flown to Dover Air Force Base in Delaware to be processed and then released to their relatives.

It had been suggested early in the investigation that the accident was caused by inadvertent detonation of the Range Safety destruct charges on the external tank, but the charges were recovered mostly intact and a quick overview of telemetry data immediately ruled out that theory.

The three shuttle main engines were found largely intact and still attached to the thrust assembly despite extensive damage from impact with the ocean, marine life, and immersion in salt water. They had considerable heat damage due to a LOX-rich shutdown caused by the drop in hydrogen fuel pressure as the external tank began to fail. The memory units from Engines 1 and 2 were recovered, cleaned, and their contents analyzed, which confirmed normal engine operation until LH2 starvation began at T+72 seconds. Loss of fuel pressure and rising combustion chamber temperatures caused the computers to shut off the engines. Since there was no evidence of abnormal SSME behavior until 72 seconds (only about one second before the breakup of Challenger), the engines were ruled out as a contributing factor in the accident.

Other recovered orbiter components showed no indication of pre-breakup malfunction. Recovered parts of the TDRSS satellite also did not disclose any abnormalities other than damage caused by vehicle breakup, impact, and immersion in salt water. The solid rocket motor boost stage for the payload had not ignited either and was quickly ruled out as a cause of the accident.

The solid rocket booster debris had no signs of explosion (other than the Range Safety charges splitting the casings open), or propellant debonding and cracking. There was no question about the RSO manually destroying the SRBs following vehicle breakup, so the idea of the destruct charges accidentally detonating was ruled out. Premature separation of the SRBs from the stack or inadvertent activation of the recovery system was also considered, but telemetry data quickly disproved that idea. Nor was there any evidence of in-flight structural failure since visual and telemetry evidence showed that the SRBs remained structurally intact up to and beyond vehicle breakup. The aft field joint on the right SRB did show extensive burn damage.

Telemetry proved that the right SRB, after the failure of the lower struts, had come loose and struck the external tank. The exact point where the struts broke could not be determined from film of the launch, nor were the struts or the adjacent section of the external tank recovered during salvage operations. Based on the location of the rupture in the right SRB, the P12 strut most likely failed first. The SRB's nose cone also exhibited some impact damage from this behavior (for comparison, the left SRB nose cone had no damage at all) and the intertank region had signs of impact damage as well. In addition, the orbiter's right wing had impact and burn damage from the right SRB colliding with it following vehicle breakup.

Most of the initially considered failure modes were soon ruled out and by May 1, enough of the right solid rocket booster had been recovered to determine the original cause of the accident, and the major salvage operations were concluded. While some shallow-water recovery efforts continued, this was unconnected with the accident investigation; it aimed to recover debris for use in NASA's studies of the properties of materials used in spacecraft and launch vehicles.[42] The recovery operation was able to pull 15 short tons (14 t) of debris from the ocean; this means that 55% of Challenger, 5% of the crew cabin and 65% of the satellite cargo are still missing.[50] Some of the missing debris continued to wash up on Florida shores for some years, such as on December 17, 1996, nearly 11 years after the incident, when two large pieces of the shuttle were found at Cocoa Beach.[51] Under 18 U.S.C. § 641 it is against the law to be in possession of Challenger debris, and any newly discovered pieces must be turned over to NASA.[52]

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.[53]

A soccer ball from the personal effects locker of Mission Specialist Ellison Onizuka was also recovered intact from the wreckage, and was later flown to the International Space Station aboard Soyuz Expedition 49 by American astronaut Robert S. Kimbrough. It is currently on display at Clear Lake High School in Houston, which was attended by Onizuka's children.[54]

All recovered non-organic debris from Challenger was ultimately buried in a former missile silo at Cape Canaveral Air Force Station Launch Complex 31.

The remains of the Challenger crew are transferred to a C-141 at the NASA KSC Shuttle Landing Facility, bound for Dover Air Force Base, Delaware.

The remains of the crew that were identifiable were returned to their families on April 29, 1986. Three of the crew members, Judith Resnik, Dick Scobee, and Capt. Michael J. Smith, were buried by their families at Arlington National Cemetery at individual grave sites. Mission Specialist Lt Col Ellison Onizuka was buried at the National Memorial Cemetery of the Pacific in Honolulu, Hawaii. Ronald McNair was buried in Rest Lawn Memorial Park in Lake City, South Carolina. Christa McAuliffe was buried at Calvary Cemetery in her hometown of Concord, New Hampshire.[55] Gregory Jarvis was cremated, and his ashes scattered in the Pacific Ocean. Unidentified crew remains were buried communally at the Space Shuttle Challenger Memorial in Arlington on May 20, 1986.[56]

As a result of the disaster, several National Reconnaissance Office (NRO) satellites that only the shuttle could launch were grounded because of the accident. This was a dilemma the NRO had feared since the 1970s when the shuttle was designated as the United States' primary launch system for all government and commercial payloads.[57][58] Compounding NASA's problems were difficulties with its Titan and Delta rocket programs which suffered other unexpected rocket failures around the time of the Challenger disaster.

The launch attempt of the Delta 3914 carrying the GOES-G, ends in failure 71 seconds later, May 3, 1986.

On August 28, 1985, a Titan 34D[59] carrying a KH-11 Kennen satellite exploded after liftoff over Vandenberg Air Force Base, when the first stage propellant feed system failed. It was the first failure of a Titan missile since 1978. On April 18, 1986, another Titan 34D-9[59][60] carrying a classified payload,[60] said to be a Big Bird spy satellite, exploded at about 830 feet (250 m) above the pad after liftoff over Vandenberg AFB, when a burnthrough occurred on one of the rocket boosters. On May 3, 1986, a Delta 3914[59] carrying the GOES-G weather satellite[61] exploded 71 seconds after liftoff over Cape Canaveral Air Force Station due to an electrical malfunction on the Delta's first stage, which prompted the range safety officer on the ground to decide to destroy the rocket, just as a few of the rocket's boosters were jettisoned. As a result of these three failures, NASA decided to cancel all Titan and Delta launches from Cape Canaveral and Vandenberg for four months until the problems in the rockets' designs were solved.

A separate related accident occurred at the Pacific Engineering and Production Company of Nevada (PEPCON) plant in Henderson, Nevada. Due to the shuttle fleet being grounded, excess ammonium perchlorate that was manufactured as rocket fuel was being kept on site. This excess ammonium perchlorate later caught fire and the magnitude of the resulting explosion destroyed the PEPCON facility and the neighboring Kidd & Company marshmallow factory.[62]

Simplified cross section of the joints between rocket segments SRB; outside to left.
Legend:
A – steel wall 0.5 inches (12.7 mm) thick
B – base O-ring gasket,
C – backup O-ring gasket,
D – Strengthening-Cover band,
E – insulation,
F – insulation,
G – carpeting,
H – sealing paste,
I – fixed propellant

The Presidential Commission on the Space Shuttle Challenger Accident, also known as the Rogers Commission after its chairman, was formed to investigate the disaster. The commission members were Chairman William P. Rogers, Vice Chairman Neil Armstrong, David Acheson, Eugene Covert, Richard Feynman, Robert Hotz, Donald Kutyna, Sally Ride, Robert Rummel, Joseph Sutter, Arthur Walker, Albert Wheelon, and Chuck Yeager. The commission worked for several months and published a report of its findings. It found that the Challenger accident was caused by a failure in the O-rings sealing a joint on the right solid rocket booster, which allowed pressurized hot gases and eventually flame to "blow by" the O-ring and make contact with the adjacent external tank, causing structural failure. The failure of the O-rings was attributed to a faulty design, whose performance could be too easily compromised by factors including the low ambient temperature on the day of launch. The O-rings would not work properly at ambient temperatures below 50 °F (10 °C)—and it was 36 °F (2 °C) on the morning of the launch.[66][67] According to the report in July 1985, a memorandum was sent to Michael Weeks, the agency's No. 2 shuttle official, and Jesse W. Moore, the associate administrator in charge of the shuttle program, raising attention to the "failure history" of the O-rings and recommending a review of the matter.

Members of the Rogers Commission arrive at Kennedy Space Center.

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. 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.[10] The report also strongly criticized the decision-making process that led to the launch of Challenger, saying that it was seriously flawed:[16]

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.[16]

One of the commission's members was theoretical physicist Richard Feynman. Feynman, who was then seriously ill with cancer, was reluctant to undertake the job. He did so at the encouragement of his wife, Gweneth Howarth. She convinced him to go, saying he might discover something others overlooked. He also wanted to find the root cause of the disaster and to speak plainly to the public about his findings.[68] Before going to Washington, D.C., Feynman did his own investigation. He became suspicious about the O-rings. “O-rings show scorching in Clovis check,” he scribbled in his notes. "Once a small hole burns through generates a large hole very fast! Few seconds catastrophic failure."[69] At the start of investigation, fellow members Dr. Sally Ride and General Donald J. Kutyna told Feynman that the O-rings had not been tested at temperatures below 50 °F (10 °C).[70] During a televised hearing, Feynman demonstrated how the O-rings became less resilient and subject to seal failures at ice-cold temperatures by immersing a sample of the material in a glass of ice water. While other members of the Commission met with NASA and supplier top management, Feynman sought out the engineers and technicians for the answers.[71] He was critical of flaws in NASA's "safety culture", so much so that he threatened to remove his name from the report unless it included his personal observations on the reliability of the shuttle, which appeared as Appendix F.[71][72] In the appendix, he argued that the estimates of reliability offered by NASA management were wildly unrealistic, differing as much as a thousandfold from the estimates of working engineers. "For a successful technology," he concluded, "reality must take precedence over public relations, for nature cannot be fooled."[73]

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.[74] 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. 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.[74]

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 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 University 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 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 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, Space Shuttle fleet was grounded for two years and eight months while the investigation, SRB redesign and other technical and management changes were taking place. On September 29, 1988, Discovery lifted off on STS-26 mission from Kennedy Space Center pad 39-B with a crew of only five veteran astronauts;[99] its pilot was Richard O. Covey, who had served as the capsule communicator to the Challenger, and the payload was a U.S. Tracking and Data Relay Satellite (named TDRS-3 after deployment), a substitute for the one lost with Challenger. The "Return to Flight" launch represented a test of the redesigned boosters and a shift to a more conservative stance on safety (the crew started again to wear pressure suits, not used since STS-4, the last of the four initial Shuttle test flights); it was a success with only two minor system failures, of a cabin cooling system and a Ku band antenna. A schedule of STS flights was resumed, about 6 per average year until the Columbia disaster on 1 February 2003, which led to a hiatus of two years and six months.

Barbara Morgan, the backup for McAuliffe who trained with her in the Teacher in Space program and was at KSC watching her launch, became a rank-and-file astronaut candidate in 1998 and flew as a Mission Specialist on STS-118 in August 2007.

NASA had intended to send a wide range of civilian passengers into space on subsequent flights. These plans were all scrapped immediately following the Challenger disaster.

NBC News's Cape Canaveral correspondent Jay Barbree was among 40 candidates in NASA's Journalist in Space Program. The first journalist was due to fly on the shuttle Challenger in September 1986. In 1984, prior to establishing the Teacher in Space Program (TISP), NASA created the Space Flight Participant Program whose aim was "to select teachers, journalists, artists, and other people who could bring their unique perspective to the human spaceflight experience as a passenger on the space shuttle." Notable among early potential passengers was Caroll Spinney who, from 1969 to 2018, played the characters Big Bird and Oscar the Grouch on the children's television show Sesame Street. In 2014, after the situation was mentioned in the documentary I Am Big Bird, NASA confirmed the revelation, stating this:

A review of past documentation shows there were initial conversations with Sesame Street regarding their potential participation on a Challenger flight, but that plan was never approved.

Spinney went on to say that the Big Bird costuming was prohibitive in the tight quarters of the NASA Space Shuttles and they had moved on.[100]

Until 2010, the live broadcast of the launch and subsequent disaster by CNN was the only known on-location video footage from within range of the launch site. As of March 15, 2014, eight other motion picture recordings of the event have become publicly available:

• a professional black-and-white NASA video recording closely showing the breakup and the subsequent remote detonation of one of the booster rockets.[141]
• a video recording by Jack Moss from the front yard of his house in Winter Haven, Florida, 80 miles (130 km) from Cape Canaveral[142][143]
• a video recording by Ishbel and Hugh Searle on a plane leaving from Orlando International Airport, 50 miles (80 km) from Cape Canaveral, was posted by their daughter Victoria on January 30, 2011, along with an interview taken on the couple two days earlier.[144]
• a Super 8 film recorded by then-19-year-old Jeffrey Ault of Orange City, Florida, at the Kennedy Space Center, 10 miles (16 km) from the launch[145]
• a video recording by Lawrence Hebert of Electric Sky Films, also filmed at the Kennedy Space Center, released in March 2012[146]
• a video recording by Steven Virostek, uncovered in May 2012[147]
• a video recording by Michael and Frances VanKulick of Melbourne, Florida, was made public in 2014.[148]

An ABC television movie titled Challenger was broadcast on February 24, 1990. It stars Barry Bostwick as Scobee, Brian Kerwin as Smith, Joe Morton as McNair, Keone Young as Onizuka, Julie Fulton as Resnik, Richard Jenkins as Jarvis, and Karen Allen as McAuliffe.[149][150][151]

A BBC docudrama titled The Challenger Disaster was broadcast on March 18, 2013, based on the last of Richard Feynman's autobiographical works, What Do You Care What Other People Think? (1988). It stars William Hurt as Feynman.[152][153]

A film produced by Vision Makers was released on January 25, 2019. It stars Dean Cain and Glenn Morshower and tells the story of the evening before the disaster where one engineer tried to stop the mission from launching.[154]

The first episode of History Channel's documentary titled Days That Shaped America is about Challenger.[155]

The four-part docuseries Challenger: The Final Flight, created by Steven Leckart and Glen Zipper, was released by Netflix on September 16, 2020.

 This article incorporates public domain material from websites or documents of the National Aeronautics and Space Administration.