Space Shuttle Challenger disaster
Overview
 
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger
Space Shuttle Challenger
Space Shuttle Challenger was NASA's second Space Shuttle orbiter to be put into service, Columbia having been the first. The shuttle was built by Rockwell International's Space Transportation Systems Division in Downey, California...

 broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 disintegrated over the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, off the coast of central Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 at 11:38 am EST
North American Eastern Time Zone
The Eastern Time Zone of the United States and Canada is a time zone that falls mostly along the east coast of North America. Its UTC time offset is −5 hrs during standard time and −4 hrs during daylight saving time...

 (16:38 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...

). Disintegration of the entire vehicle began after an O-ring
O-ring
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...

 seal in its right solid rocket booster
Space Shuttle Solid Rocket Booster
The Space Shuttle Solid Rocket Boosters were the pair of large solid rockets used by the United States' NASA Space Shuttle during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or...

 (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
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

.
Encyclopedia
The Space Shuttle Challenger disaster occurred on January 28, 1986, when Space Shuttle Challenger
Space Shuttle Challenger
Space Shuttle Challenger was NASA's second Space Shuttle orbiter to be put into service, Columbia having been the first. The shuttle was built by Rockwell International's Space Transportation Systems Division in Downey, California...

 broke apart 73 seconds into its flight, leading to the deaths of its seven crew members. The spacecraft
Spacecraft
A spacecraft or spaceship is a craft or machine designed for spaceflight. Spacecraft are used for a variety of purposes, including communications, earth observation, meteorology, navigation, planetary exploration and transportation of humans and cargo....

 disintegrated over the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, off the coast of central Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...

 at 11:38 am EST
North American Eastern Time Zone
The Eastern Time Zone of the United States and Canada is a time zone that falls mostly along the east coast of North America. Its UTC time offset is −5 hrs during standard time and −4 hrs during daylight saving time...

 (16:38 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...

). Disintegration of the entire vehicle began after an O-ring
O-ring
An O-ring, also known as a packing, or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a disc-shaped cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.The O-ring...

 seal in its right solid rocket booster
Space Shuttle Solid Rocket Booster
The Space Shuttle Solid Rocket Boosters were the pair of large solid rockets used by the United States' NASA Space Shuttle during the first two minutes of powered flight. Together they provided about 83% of liftoff thrust for the Space Shuttle. They were located on either side of the rusty or...

 (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
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

. This led to the separation of the right-hand SRB's aft attachment and the structural failure
Structural failure
Structural failure refers to loss of the load-carrying capacity of a component or member within a structure or of the structure itself. Structural failure is initiated when the material is stressed to its strength limit, thus causing fracture or excessive deformations...

 of the external tank. Aerodynamic
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...

 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
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....

 Ronald Reagan
Ronald Reagan
Ronald Wilson Reagan was the 40th President of the United States , the 33rd Governor of California and, prior to that, a radio, film and television actor....

 to investigate the accident. The Rogers Commission found NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's organizational culture
Organizational culture
Organizational culture is defined as “A pattern of shared basic assumptions invented, discovered, or developed by a given group as it learns to cope with its problems of external adaptation and internal integration" that have worked well enough to be considered valid and therefore, to be taught to...

 and decision-making processes had been key contributing factors to the accident. NASA managers had known contractor Morton Thiokol's design of the SRBs contained a potentially catastrophic flaw in the O-rings since 1977, but 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.,

What Rogers did not highlight was the fact the vehicle 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. Bob Ebeling from Thiokol gave this severely succinct analysis:
"we’re only qualified to 40 degrees ...‘what business does anyone even have thinking about 18 degrees, we’re in no man’s land’".


Many viewed the launch live because of the presence on the crew of Christa McAuliffe
Christa McAuliffe
Christa McAuliffe was an American teacher from Concord, New Hampshire, and was one of the seven crew members killed in the Space Shuttle Challenger disaster....

, the first member of the Teacher in Space Project
Teacher in Space Project
The Teacher in Space Project was a NASA program announced by Ronald Reagan in 1984 designed to inspire students, honor teachers, and spur interest in mathematics, science, and space exploration....

. 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.

Pre-launch conditions and delays

Challenger was originally set to launch from Kennedy Space Center (KSC)
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

 in Florida at 2:42 pm Eastern Standard Time (EST) on January 22. However, delays suffered by the previous mission, STS-61-C
STS-61-C
-Mission parameters:*Mass:**Orbiter liftoff: **Orbiter landing: **Payload: *Perigee: *Apogee: *Inclination: 28.5°*Period: 91.2 min-Mission background:...

, caused the launch date to be pushed back to January 23 and then to January 24. Launch was then rescheduled to January 25 due to bad weather
Storm
A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather...

 at the Transoceanic Abort Landing (TAL)
Space Shuttle abort modes
A Space Shuttle abort was an emergency procedure due to equipment failure on NASA's Space Shuttle, most commonly during ascent. A main engine failure is a typical abort scenario. There are fewer abort options during reentry and descent...

 site in Dakar
Dakar
Dakar is the capital city and largest city of Senegal. It is located on the Cap-Vert Peninsula on the Atlantic coast and is the westernmost city on the African mainland...

, Senegal
Senegal
Senegal , officially the Republic of Senegal , is a country in western Africa. It owes its name to the Sénégal River that borders it to the east and north...

. NASA decided to use Casablanca
Casablanca
Casablanca is a city in western Morocco, located on the Atlantic Ocean. It is the capital of the Grand Casablanca region.Casablanca is Morocco's largest city as well as its chief port. It is also the biggest city in the Maghreb. The 2004 census recorded a population of 2,949,805 in the prefecture...

 as the TAL site, but because it was not equipped for night landings, the launch had to be moved to the morning (Florida time
North American Eastern Time Zone
The Eastern Time Zone of the United States and Canada is a time zone that falls mostly along the east coast of North America. Its UTC time offset is −5 hrs during standard time and −4 hrs during daylight saving time...

). Predictions of unacceptable weather at Kennedy Space Center
Kennedy Space Center
The John F. Kennedy Space Center is the NASA installation that has been the launch site for every United States human space flight since 1968. Although such flights are currently on hiatus, KSC continues to manage and operate unmanned rocket launch facilities for America's civilian space program...

 caused the launch to be rescheduled for 9:37 am EST on January 27.

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. Then, a stripped bolt prevented the closeout crew from removing a closing fixture from the orbiter's hatch. When the fixture was finally sawn off, crosswinds at the Shuttle Landing Facility exceeded the limits for a Return to Launch Site (RTLS)
Space Shuttle abort modes
A Space Shuttle abort was an emergency procedure due to equipment failure on NASA's Space Shuttle, most commonly during ascent. A main engine failure is a typical abort scenario. There are fewer abort options during reentry and descent...

 abort. 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 (-.6 °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
Marshall Space Flight Center
The George C. Marshall Space Flight Center is the U.S. government's civilian rocketry and spacecraft propulsion research center. The largest center of NASA, MSFC's first mission was developing the Saturn launch vehicles for the Apollo moon program...

. Several engineers—most notably Roger Boisjoly
Roger Boisjoly
Roger M. Boisjoly is a mechanical engineer, fluid dynamicist and an aerodynamicist who worked for Morton Thiokol, the manufacturer of the solid rocket boosters for the Space Shuttle program...

, 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". The factory joints had asbestos-silica insulation applied over the joint, while the field joints—assembled in the Vehicle Assembly Building at Kennedy Space Center—depended on 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 (11.7 °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
Sally Ride
Sally Kristen Ride is an American physicist and a former NASA astronaut. Ride joined NASA in 1978, and in 1983 became the first American woman—and then-youngest American, at 32—to enter space...

 cited in questioning NASA managers before the Rogers Commission
Rogers Commission Report
The Rogers Commission Report was created by a Presidential Commission charged with investigating the Space Shuttle Challenger disaster during its 10th mission, STS-51-L...

, 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 °F (-7.8 °C) the evening prior to launch) would almost certainly result in SRB temperatures below their redline of 40 °F (4.4 °C). Ice had accumulated all over the launch pad, raising concerns that ice could damage the shuttle upon lift-off.

However, the engineers were overruled by Morton Thiokol management, who recommended that the launch proceed as scheduled. 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 (-13.3 °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 (-13.3 °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.

Although the Ice Team had worked through the night removing ice, engineers at Rockwell International
Rockwell International
Rockwell International was a major American manufacturing conglomerate in the latter half of the 20th century, involved in aircraft, the space industry, both defense-oriented and commercial electronics, automotive and truck components, printing presses, valves and meters, and industrial automation....

, the shuttle's prime contractor, still expressed concern. Rockwell engineers watching the pad from their headquarters in Downey, California
Downey, California
Downey is a city located in southeast Los Angeles County, California, United States, southeast of downtown Los Angeles. The city is best known as the birthplace of the Apollo space program, and is the city where folk singer Karen Carpenter lived and died...

, 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
Jet (fluid)
A jet is an efflux of fluid that is projected into a surrounding medium, usually from some kind of a nozzle, aperture or orifice. Jets can travel long distances without dissipating...

 of exhaust gas
Exhaust gas
Exhaust gas or flue gas is emitted as a result of the combustion of fuels such as natural gas, gasoline/petrol, diesel fuel, fuel oil or coal. According to the type of engine, it is discharged into the atmosphere through an exhaust pipe, flue gas stack or propelling nozzle.It often disperses...

 from the SRBs. Rocco Petrone
Rocco Petrone
Rocco Anthony Petrone was an American engineer who was the third director of the NASA's Marshall Space Flight Center, from 1973 to 1974...

, 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 am EST.

Liftoff and initial ascent


The following account of the accident is derived from real time telemetry
Telemetry
Telemetry is a technology that allows measurements to be made at a distance, usually via radio wave transmission and reception of the information. The word is derived from Greek roots: tele = remote, and metron = measure...

 data and photographic analysis, as well as from transcripts of air-to-ground and mission control
Mission Control Center
A mission control center is an entity that manages aerospace vehicle flights, usually from the point of lift-off until the landing or the end of the mission. A staff of flight controllers and other support personnel monitor all aspects of the mission using telemetry, and send commands to the...

 voice communications. All times are given in seconds after launch and correspond to the telemetry time-codes from the closest instrumented event to each described event.

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)
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

 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. 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.

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
Aft
Aft, in naval terminology, is an adjective or adverb meaning, towards the stern of the ship, when the frame of reference is within the ship. Example: "Able Seaman Smith; lay aft!". Or; "What's happening 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 5000 °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
Extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section...

.

While extrusion was taking place, hot gases leaked 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 could not 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
Launch Control Center
The Launch Control Center is a four-story building located at NASA's Kennedy Space Center on Merritt Island, Florida used for the supervision of launches from Launch Complex 39. In practice, this means that the LCC handles all American manned space flights...

 (LCC) at Kennedy to the Mission Control Center (MCC) at Johnson Space Center in Houston, Texas
Houston, Texas
Houston is the fourth-largest city in the United States, and the largest city in the state of Texas. According to the 2010 U.S. Census, the city had a population of 2.1 million people within an area of . Houston is the seat of Harris County and the economic center of , which is the ...

. To prevent aerodynamic
Aerodynamics
Aerodynamics is a branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. Aerodynamics is a subfield of fluid dynamics and gas dynamics, with much theory shared between them. Aerodynamics is often used synonymously with gas dynamics, with...

 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
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....

, as per normal operating procedure. At T+35.379, the SSMEs throttled back further to the planned 65%. Five seconds later, at about 5800 metres (19,028.9 ft), Challenger passed through Mach 1
Mach number
Mach number is the speed of an object moving through air, or any other fluid substance, divided by the speed of sound as it is in that substance for its particular physical conditions, including those of temperature and pressure...

. At T+51.860, the SSMEs began throttling back up to 104% as the vehicle passed beyond Max Q
Max Q
In aerospace engineering, the maximum dynamic pressure, often referred to as maximum Q or max Q, is the point at which aerodynamic stress on a vehicle in atmospheric flight is maximized...

, the period of maximum aerodynamic pressure on the vehicle.

Plume

Beginning at about T+37, the shuttle experienced a series of wind shear events over the next 27 seconds that were the strongest recorded to date in the shuttle program.

At T+58.788, a tracking film camera captured the beginnings of a plume
Plume (hydrodynamics)
In hydrodynamics, a plume is a column of one fluid or gas moving through another. Several effects control the motion of the fluid, including momentum, diffusion, and buoyancy...

 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.

At T+64.660, the plume suddenly changed shape, indicating that a leak had begun in the liquid hydrogen
Liquid hydrogen
Liquid hydrogen is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.To exist as a liquid, H2 must be pressurized above and cooled below hydrogen's Critical point. However, for hydrogen to be in a full liquid state without boiling off, it needs to be...

 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.

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
Dick Scobee
Francis Richard "Dick" Scobee was an American astronaut. He was killed commanding the Space Shuttle Challenger, which suffered catastrophic booster failure during launch of the STS-51-L mission.-Early life:...

 confirmed the call. His response, "Roger, go at throttle up," was the last communication from Challenger on the air-to-ground loop.

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
Uh-oh (expression)
Uh-oh is a ubiquitous interjection or expression of dismay in the English language, usually said in anticipation of something bad about to happen, with the sly admittance of guilt that one may have caused something bad to happen, or perceiving that something bad has already happened...

." 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). 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 quickly 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.

The more robustly constructed crew cabin and SRBs survived the breakup of the launch vehicle; while the SRBs were subsequently detonated remotely by the RSO
Range Safety Officer
In the field of rocketry, Range Safety Officer is a generic term referring to an individual who monitors the performance of rockets in flight, and who is responsible for their remote destruction if it should be judged that they pose a hazard...

, the detached cabin continued along a ballistic
Ballistics
Ballistics is the science of mechanics that deals with the flight, behavior, and effects of projectiles, especially bullets, gravity bombs, rockets, or the like; the science or art of designing and accelerating projectiles so as to achieve a desired performance.A ballistic body is a body which is...

 trajectory, and was observed exiting the cloud of gases at T+75.237. Twenty-five seconds after the breakup of the vehicle the trajectory of the crew compartment peaked at a height of 65,000 feet (19.8 kilometres (12.3 mi)).

Post-breakup flight controller dialog

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 combustion) where Challenger had been, with pieces of debris falling toward the ocean. At about T+89, flight director Jay Greene
Jay Greene
Jay H. Greene is a retired NASA engineer. He worked as a FIDO flight controller during the Apollo Program and a flight director from 1982 to 1986, most notably as ascent flight director during the Challenger accident in 1986...

 prompted his flight dynamics officer (FIDO) for information. FIDO responded that "...the (radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...

) filter has discreting sources", a further indication that Challenger had broken into multiple pieces. A minute later, the ground controller 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
Range Safety Officer
In the field of rocketry, Range Safety Officer is a generic term referring to an individual who monitors the performance of rockets in flight, and who is responsible for their remote destruction if it should be judged that they pose a hazard...

 (RSO) at the Cape Canaveral Air Force Station
Cape Canaveral Air Force Station
Cape Canaveral Air Force Station is an installation of the United States Air Force Space Command's 45th Space Wing, headquartered at nearby Patrick Air Force Base. Located on Cape Canaveral in the state of Florida, CCAFS is the primary launch head of America's Eastern Range with four launch pads...

 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.

"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.

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 . The crew cabin in particular is a very robust section of the shuttle because of its design and construction of reinforced aluminum. During vehicle breakup, the crew cabin detached in one piece and slowly tumbled into a ballistic arc
External ballistics
External ballistics is the part of the science of ballistics that deals with the behaviour of a non-powered projectile in flight. External ballistics is frequently associated with firearms, and deals with the behaviour of the bullet after it exits the barrel and before it hits the target.-Forces...

. 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
Free fall
Free fall is any motion of a body where gravity is the only force acting upon it, at least initially. These conditions produce an inertial trajectory so long as gravity remains the only force. Since this definition does not specify velocity, it also applies to objects initially moving upward...

. 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
Personal Egress Air Packs
Personal Egress Air Packs, or PEAPs, were devices on board a Space Shuttle which provided crew members with approximately six minutes of breathable air in the case of a mishap while the vehicle was still located on the ground...

 (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. Fellow Astronaut Richard Mullane
Richard Mullane
Richard Michael "Mike" Mullane is a retired USAF officer and a former NASA astronaut.-Personal:Mullane was born September 10, 1945, in Wichita Falls, Texas, but considers Albuquerque, New Mexico, to be his hometown. He was a Second Class Scout in the Boy Scouts of America. He graduated from St...

 wrote, "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.

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 (333.1 km/h), with an estimated deceleration at impact of well over 200 g
Earth's gravity
The gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface. In SI units this acceleration is measured in metres per second per second or equivalently in newtons per kilogram...

, far beyond the structural limits of the crew compartment or crew survivability levels.
On July 28, 1986, Rear Admiral Richard H. Truly
Richard H. Truly
Richard Harrison Truly is a retired Vice Admiral in the United States Navy, Naval Aviator, former astronaut, and was the eighth Administrator of the National Aeronautics and Space Administration from 1989 to 1992...

, NASA's Associate Administrator for Space Flight and a former astronaut, released a report from Joseph P. Kerwin
Joseph P. Kerwin
Joseph Peter Kerwin, M.D. is an American physician and former NASA astronaut. Kerwin was the first physician to be selected for astronaut training....

, biomedical specialist from the Johnson Space Center
Lyndon B. Johnson Space Center
The Lyndon B. Johnson Space Center is the National Aeronautics and Space Administration's center for human spaceflight training, research and flight control. The center consists of a complex of 100 buildings constructed on 1,620 acres in Houston, Texas, USA...

 in Houston, relating to the deaths of the astronauts in the accident. Kerwin, a veteran of the Skylab 2
Skylab 2
-Backup crew:-Support crew:*Robert L. Crippen*Richard H. Truly*Henry W. Hartsfield, Jr*William E. Thornton-Mission parameters:*Mass: 19,979 kg*Maximum Altitude: 440 km*Distance: 18,536,730.9 km...

 mission, had been commissioned to undertake the study soon after the accident. According to the Kerwin Report:



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.

Crew escape was not possible

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
SR-71 Blackbird
The Lockheed SR-71 "Blackbird" was an advanced, long-range, Mach 3+ strategic reconnaissance aircraft. It was developed as a black project from the Lockheed A-12 reconnaissance aircraft in the 1960s by the Lockheed Skunk Works. Clarence "Kelly" Johnson was responsible for many of the...

 ejection seats and full pressure suit
Pressure suit
A pressure suit is a protective suit worn by high-altitude pilots who may fly at altitudes where the air pressure is too low for an unprotected person to survive, even breathing pure oxygen at positive pressure. Such suits may be either full-pressure or partial-pressure...

s 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
Space Shuttle Columbia disaster
The Space Shuttle Columbia disaster occurred on February 1, 2003, when shortly before it was scheduled to conclude its 28th mission, STS-107, the Space Shuttle Columbia disintegrated over Texas and Louisiana during re-entry into the Earth's atmosphere, resulting in the death of all seven crew members...

, 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."

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
Gliding (flight)
Gliding flight is heavier-than-air flight without the use of thrust. It is employed by gliding animals and by aircraft such as gliders. The most common human application of gliding flight is in sport and recreation using aircraft designed for this purpose...

; however, this system would not have been usable in the Challenger situation.

Aftermath

Tributes

On the night of the disaster, President
President of the United States
The President of the United States of America is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces....

 Ronald Reagan
Ronald Reagan
Ronald Wilson Reagan was the 40th President of the United States , the 33rd Governor of California and, prior to that, a radio, film and television actor....

 had been scheduled to give his annual State of the Union address
State of the Union Address
The State of the Union is an annual address presented by the President of the United States to the United States Congress. The address not only reports on the condition of the nation but also allows the president to outline his legislative agenda and his national priorities.The practice arises...

. 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
Oval Office
The Oval Office, located in the West Wing of the White House, is the official office of the President of the United States.The room features three large south-facing windows behind the president's desk, and a fireplace at the north end...

 of the White House
White House
The White House is the official residence and principal workplace of the president of the United States. Located at 1600 Pennsylvania Avenue NW in Washington, D.C., the house was designed by Irish-born James Hoban, and built between 1792 and 1800 of white-painted Aquia sandstone in the Neoclassical...

. It was written by Peggy Noonan
Peggy Noonan
Peggy Noonan is an American author of seven books on politics, religion, and culture and a weekly columnist for The Wall Street Journal...

, and finished with the following statement, which quoted from the poem "High Flight" by John Gillespie Magee, Jr.
John Gillespie Magee, Jr.
John Gillespie Magee, Jr. was an American aviator and poet who died as a result of a mid-air collision over Lincolnshire during World War II. He was serving in the Royal Canadian Air Force, which he joined before the United States officially entered the war. He is most famous for his poem "High...

:
Three days later, Reagan and his wife Nancy
Nancy Reagan
Nancy Davis Reagan is the widow of former United States President Ronald Reagan and was First Lady of the United States from 1981 to 1989....

 traveled to the Johnson Space Center to speak at a memorial service honoring the astronauts where he stated:
It was attended by 6,000 NASA employees and 4,000 guests,
as well as by the families of the crew. During the ceremony, an Air Force band led the singing of "God Bless America
God Bless America
"God Bless America" is an American patriotic song written by Irving Berlin in 1918 and revised by him in 1938. The later version has notably been recorded by Kate Smith, becoming her signature song ....

" as NASA T-38 Talon
T-38 Talon
The Northrop T-38 Talon is a twin-engine supersonic jet trainer. It was the world's first supersonic trainer and is also the most produced. The T-38 remains in service as of 2011 in air forces throughout the world....

 jets flew directly over the scene, in the traditional missing-man formation
Missing man formation
The missing man formation is an aerial salute performed as part of a flyover of aircraft at a funeral or memorial event, typically in memory of a fallen pilot. The missing man formation is often called "the missing man flyby"...

. All activities were broadcast live by the national television networks.

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
Search and rescue
Search and rescue is the search for and provision of aid to people who are in distress or imminent danger.The general field of search and rescue includes many specialty sub-fields, mostly based upon terrain considerations...

 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.

The search and rescue operations that took place in the first week after the Challenger accident were managed by the Department of Defense
United States Department of Defense
The United States Department of Defense is the U.S...

 on behalf of NASA, with assistance from the United States Coast Guard
United States Coast Guard
The United States Coast Guard is a branch of the United States Armed Forces and one of the seven U.S. uniformed services. The Coast Guard is a maritime, military, multi-mission service unique among the military branches for having a maritime law enforcement mission and a federal regulatory agency...

, and mostly involved surface searches. According to the Coast Guard, "the operation was the largest surface search in which they had participated." 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
Marine salvage
Marine salvage is the process of rescuing a ship, its cargo, or other property from peril. Salvage encompasses rescue towing, refloating a sunken or grounded vessel, or patching or repairing a ship...

 debris that would help in determining the cause of the accident. Sonar
Sonar
Sonar is a technique that uses sound propagation to navigate, communicate with or detect other vessels...

, divers, remotely operated submersible
Submersible
A submersible is a small vehicle designed to operate underwater. The term submersible is often used to differentiate from other underwater vehicles known as submarines, in that a submarine is a fully autonomous craft, capable of renewing its own power and breathing air, whereas a submersible is...

s and manned submersibles were all used during the search, which covered an area of 480 square nautical miles (1600 kilometres (994.2 mi)²), and took place at depths of up to 370 metres (1,213.9 ft). On March 7, divers from the USS Preserver
USS Preserver (ARS-8)
USS Preserver was an commissioned by the U.S. Navy for service in World War II. She was responsible for coming to the aid of stricken vessels....

 identified what might be the crew compartment on the ocean floor. 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.

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. The recovery operation was able to pull 15 short tons (13.4 LT) of debris from the ocean; 55% of Challenger, 5% of the crew cabin and 65% of the satellite cargo is still missing. Some of the missing debris still washes up on Florida shores, such as on December 17, 1996, nearly 11 years after the incident, when two large pieces of the shuttle were found at Cocoa Beach
Cocoa Beach, Florida
Cocoa Beach is a city in Brevard County, Florida, United States. The population was 12,482 at the 2000 census. According to the U.S. Census Bureau estimates of 2008, the city had a population of 11,920...

. Under it is against the law to be in possession of Challenger debris, and any newly discovered pieces must be turned in to NASA. All debris is currently maintained in a sealed former underground missile silo at Cape Canaveral Air Force Station Launch Complex 31
Cape Canaveral Air Force Station Launch Complex 31
Launch Complex 31 is a former launch complex at Cape Canaveral Air Force Station, Florida.It was built in 1959 with LC-32 for the U.S. Air Force to conduct test launches of the first LGM-30 Minuteman missiles. LC-31 was built next to Navaho complex LC-9, requiring LC-10 to be demolished...

.

On board Challenger was an American flag, dubbed the Challenger flag
Challenger flag
The Challenger flag is an American flag that was in the flight kit of the final, disastrous Challenger mission. It was sponsored by Boy Scout Troop 514 of Monument, Colorado...

, that was sponsored by Boy Scout
Scouting in Colorado
Scouting in Colorado has a long history, from the 1910s to the present day, serving thousands of youth in programs that suit the rugged, mountainous environment in which they live.-Early history :Scouting got a brisk start in Colorado...

 Troop 514 of Monument, Colorado
Monument, Colorado
Monument is a growing town situated on the Rampart Range in El Paso County, Colorado, United States. Monument is bordered by Pike National Forest on the west, Colorado Springs and the United States Air Force Academy to the south, foothills and rock outcroppings to the north and rolling plains to...

. It was recovered intact, still sealed in its plastic container.

Funeral ceremonies

The remains of the crew that were identifiable were returned to their families on April 29, 1986. Two of the crew members, Dick Scobee
Dick Scobee
Francis Richard "Dick" Scobee was an American astronaut. He was killed commanding the Space Shuttle Challenger, which suffered catastrophic booster failure during launch of the STS-51-L mission.-Early life:...

 and posthumously promoted Capt. Michael J. Smith, were buried by their families at Arlington National Cemetery
Arlington National Cemetery
Arlington National Cemetery in Arlington County, Virginia, is a military cemetery in the United States of America, established during the American Civil War on the grounds of Arlington House, formerly the estate of the family of Confederate general Robert E. Lee's wife Mary Anna Lee, a great...

 at individual grave sites. Mission Specialist Lt Col Ellison Onizuka
Ellison Onizuka
was a Japanese American astronaut from Kealakekua, Kona, Hawaii, who successfully flew into space with the Space Shuttle Discovery on STS-51-C, before losing his life to the destruction of the Space Shuttle Challenger, where he was serving as Mission Specialist for mission STS-51-L...

 was buried at the National Memorial Cemetery of the Pacific
National Memorial Cemetery of the Pacific
The National Memorial Cemetery of the Pacific is a cemetery located in Honolulu, Hawaii that serves a memorial to those men and women who served in the United States Armed Forces...

 in Honolulu, Hawaii. Unidentified crew remains were buried communally at the Space Shuttle Challenger Memorial in Arlington on May 20, 1986.

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". In the absence of reliable sources, the press turned to speculation; both The New York Times
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

 and United Press International
United Press International
United Press International is a once-major international news agency, whose newswires, photo, news film and audio services provided news material to thousands of newspapers, magazines and radio and television stations for most of the twentieth century...

 ran stories suggesting that a fault with the space shuttle external tank
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

 had caused the accident, despite the fact that NASA's internal investigation had quickly focused in on the solid rocket boosters. "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."

Rogers Commission

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
William P. Rogers
William Pierce Rogers was an American politician, who served as a Cabinet officer in the administrations of two U.S. Presidents in the third quarter of the 20th century.-Early Life :...

, Vice Chairman Neil Armstrong
Neil Armstrong
Neil Alden Armstrong is an American former astronaut, test pilot, aerospace engineer, university professor, United States Naval Aviator, and the first person to set foot upon the Moon....

, David Acheson
David Acheson
David Campion Acheson is an American lawyer and the son of former US Secretary of State Dean Acheson.David Acheson was born in Washington, D.C. He graduated from Yale University, where he was President of the Yale Political Union and a member of Skull and Bones, with a B.A. in 1942. After serving...

, Eugene Covert, Richard Feynman
Richard Feynman
Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

, Robert Hotz, Donald Kutyna, Sally Ride
Sally Ride
Sally Kristen Ride is an American physicist and a former NASA astronaut. Ride joined NASA in 1978, and in 1983 became the first American woman—and then-youngest American, at 32—to enter space...

, Robert Rummel, Joseph Sutter
Joe Sutter
Joseph F. "Joe" Sutter was an engineer for the Boeing Airplane Company and chief engineer for the development of the Boeing 747 under Malcolm T. Stamper.-Early life:...

, Arthur Walker
Arthur B. C. Walker, Jr.
Arthur Bertram Cuthbert Walker, Jr. was a solar physicist and a pioneer of EUV/XUV optics. He is most noted for having developed normal incidence multilayer XUV telescopes to photograph the solar corona...

, Albert Wheelon, and Chuck Yeager
Chuck Yeager
Charles Elwood "Chuck" Yeager is a retired major general in the United States Air Force and noted test pilot. He was the first pilot to travel faster than sound...

. 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
Space Shuttle external tank
A Space Shuttle External Tank is the component of the Space Shuttle launch vehicle that contains the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplies the fuel and oxidizer under pressure to the three Space Shuttle Main Engines in the orbiter...

, 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 temperature on the day of launch.
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. The report also strongly criticized the decision making process that led to the launch of Challenger, saying that it was seriously flawed.
One of the commission's most well-known members was theoretical physicist Richard Feynman
Richard Feynman
Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

. During a televised hearing, he famously 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. He was so critical of flaws in NASA's "safety culture" 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. 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."

U.S. House Committee hearings

The U.S. House Committee on Science and Technology
United States House Committee on Science
The Committee on Science, Space and Technology is a committee of the United States House of Representatives. It has jurisdiction over non-defense federal scientific research and development...

 also conducted hearings, and on October 29, 1986 released its own report on the Challenger accident. 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.

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
Apollo 1
Apollo 1 was scheduled to be the first manned mission of the Apollo manned lunar landing program, with a target launch date of February 21, 1967. A cabin fire during a launch pad test on January 27 at Launch Pad 34 at Cape Canaveral killed all three crew members: Command Pilot Virgil "Gus"...

 fire in 1967, its actions after Challenger were more constrained by the judgment of outside bodies. The Rogers Commission offered nine recommendations on improving safety in the space shuttle program, and NASA was directed by President Reagan to report back within thirty days as to how it planned to implement those recommendations.

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. 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.

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
Martin Marietta
Martin Marietta Corporation was an American company founded in 1961 through the merger of The Martin Company and American-Marietta Corporation. The combined company became a leader in chemicals, aerospace, and electronics. In 1995, it merged with Lockheed Corporation to form Lockheed Martin. The...

, was appointed to this position. Former Challenger flight director Jay Greene
Jay Greene
Jay H. Greene is a retired NASA engineer. He worked as a FIDO flight controller during the Apollo Program and a flight director from 1982 to 1986, most notably as ascent flight director during the Challenger accident in 1986...

 became chief of the Safety Division of the directorate.

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
Space Shuttle Endeavour
Space Shuttle Endeavour is one of the retired orbiters of the Space Shuttle program of NASA, the space agency of the United States. Endeavour was the fifth and final spaceworthy NASA space shuttle to be built, constructed as a replacement for Challenger...

, 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. In August 1986, President Reagan also announced that the shuttle would no longer carry commercial satellite
Satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

 payloads. After a 32-month hiatus, the next shuttle mission, STS-26
STS-26
STS-26 was the 26th NASA Space Shuttle mission and the seventh flight of the Discovery orbiter. The mission launched from Kennedy Space Center, Florida, on 29 September 1988, and landed four days later on 3 October. STS-26 was declared the "Return to Flight" mission, being the first mission after...

, 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
Space Shuttle Columbia disaster
The Space Shuttle Columbia disaster occurred on February 1, 2003, when shortly before it was scheduled to conclude its 28th mission, STS-107, the Space Shuttle Columbia disintegrated over Texas and Louisiana during re-entry into the Earth's atmosphere, resulting in the death of all seven crew members...

 in 2003, attention once again focused on the attitude of NASA management towards safety issues. The Columbia Accident Investigation Board
Columbia Accident Investigation Board
The Columbia Accident Investigation Board was convened by NASA to investigate the destruction of the Space Shuttle Columbia during STS-107 upon atmospheric re-entry on February 1, 2003. In addition to determining the cause of the accident, the panel also recommended changes that should be made...

 (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". 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 Columbias
Space Shuttle Columbia
Space Shuttle Columbia was the first spaceworthy Space Shuttle in NASA's orbital fleet. First launched on the STS-1 mission, the first of the Space Shuttle program, it completed 27 missions before being destroyed during re-entry on February 1, 2003 near the end of its 28th, STS-107. All seven crew...

 destruction seventeen years later.

Media coverage

While the presence of New Hampshire
New Hampshire
New Hampshire is a state in the New England region of the northeastern United States of America. The state was named after the southern English county of Hampshire. It is bordered by Massachusetts to the south, Vermont to the west, Maine and the Atlantic Ocean to the east, and the Canadian...

 schoolteacher Christa McAuliffe
Christa McAuliffe
Christa McAuliffe was an American teacher from Concord, New Hampshire, and was one of the seven crew members killed in the Space Shuttle Challenger disaster....

 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
CNN
Cable News Network is a U.S. cable news channel founded in 1980 by Ted Turner. Upon its launch, CNN was the first channel to provide 24-hour television news coverage, and the first all-news television channel in the United States...

; 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
NASA TV
NASA TV is the television service of the United States government agency NASA. NASA TV is broadcast by satellite with a simulcast over the Internet. Local cable television systems across the U.S. and amateur television repeaters may carry NASA TV at their discretion, as NASA-created content is...

. 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
Dallas, Texas
Dallas is the third-largest city in Texas and the ninth-largest in the United States. The Dallas-Fort Worth Metroplex is the largest metropolitan area in the South and fourth-largest metropolitan area in the United States...

 after President John F. Kennedy
John F. Kennedy
John Fitzgerald "Jack" Kennedy , often referred to by his initials JFK, was the 35th President of the United States, serving from 1961 until his assassination in 1963....

's assassination
John F. Kennedy assassination
John Fitzgerald Kennedy, the thirty-fifth President of the United States, was assassinated at 12:30 p.m. Central Standard Time on Friday, November 22, 1963, in Dealey Plaza, Dallas, Texas...

, while the other was the spread of news among students at Kent State
Kent State University
Kent State University is a public research university located in Kent, Ohio, United States. The university has eight campuses around the northeast Ohio region with the main campus in Kent being the largest...

 regarding President Franklin D. Roosevelt's
Franklin D. Roosevelt
Franklin Delano Roosevelt , also known by his initials, FDR, was the 32nd President of the United States and a central figure in world events during the mid-20th century, leading the United States during a time of worldwide economic crisis and world war...

 death.) 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." 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
The New York Times
The New York Times is an American daily newspaper founded and continuously published in New York City since 1851. The New York Times has won 106 Pulitzer Prizes, the most of any news organization...

 poll — watched the launch at school.

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.

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
Groupthink
Groupthink is a psychological phenomenon that occurs within groups of people. It is the mode of thinking that happens when the desire for harmony in a decision-making group overrides a realistic appraisal of alternatives. Group members try to minimize conflict and reach a consensus decision without...

. It is part of the required readings for engineers seeking a professional license in Canada and other countries. Roger Boisjoly
Roger Boisjoly
Roger M. Boisjoly is a mechanical engineer, fluid dynamicist and an aerodynamicist who worked for Morton Thiokol, the manufacturer of the solid rocket boosters for the Space Shuttle program...

, 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. He argues that the caucus
Caucus
A caucus is a meeting of supporters or members of a political party or movement, especially in the United States and Canada. As the use of the term has been expanded the exact definition has come to vary among political cultures.-Origin of the term:...

 called by Morton Thiokol managers, which resulted in a recommendation to launch, "constituted the unethical decision-making forum resulting from intense customer intimidation." 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
Engineering ethics
Engineering ethics is the field of applied ethics and system of moral principles that apply to the practice of engineering. The field examines and sets the obligations by engineers to society, to their clients, and to the profession...

.

Information designer Edward Tufte
Edward Tufte
Edward Rolf Tufte is an American statistician and professor emeritus of political science, statistics, and computer science at Yale University. He is noted for his writings on information design and as a pioneer in the field of data visualization....

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

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 am on September 29, 1988, Space Shuttle Discovery lifted off with a crew of five 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
STS-26
STS-26 was the 26th NASA Space Shuttle mission and the seventh flight of the Discovery orbiter. The mission launched from Kennedy Space Center, Florida, on 29 September 1988, and landed four days later on 3 October. STS-26 was declared the "Return to Flight" mission, being the first mission after...

, 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
Barbara Morgan
Barbara Radding Morgan is an American teacher and a former NASA astronaut. She participated in the Teacher in Space program as the backup to Christa McAuliffe for the ill-fated STS-51L mission of Space Shuttle Challenger. She then trained as a Mission Specialist, and flew on STS-118 in August 2007...

, 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
STS-118
- Crew notes :Astronaut Clayton Anderson originally was slated to be launched to the ISS on this mission, but was moved to STS-117. His replacement was Alvin Drew....

 as a Mission Specialist in August 2007.

Legacy

The families of the Challenger crew organized the Challenger Center for Space Science Education
Challenger Center for Space Science Education
' is a nonprofit educational organization with its headquarters in Alexandria, Virginia, and an international network of Challenger Learning Centers. The organization was founded in April 1986 by the families of the astronauts who died in the Space Shuttle Challenger disaster on January 28,...

 as a permanent memorial to the crew. Fifty-two learning centers have been established by this non-profit organization.
In Huntsville, Alabama
Huntsville, Alabama
Huntsville is a city located primarily in Madison County in the central part of the far northern region of the U.S. state of Alabama. Huntsville is the county seat of Madison County. The city extends west into neighboring Limestone County. Huntsville's population was 180,105 as of the 2010 Census....

, a city known for its strong association with NASA, the next-opened public middle school in the Huntsville City Schools system was named Challenger Middle School. The City of Palmdale
Palmdale, California
Palmdale is a city located in the center of northern Los Angeles County, California, United States.Palmdale was the first community within the Antelope Valley to incorporate as a city on August 24, 1962; 47 years later, voters approved creating a charter city in November, 2009. Palmdale is...

, the birthplace of the entire shuttle fleet, and its neighbor City of Lancaster, California
Lancaster, California
Lancaster is a charter city in northern Los Angeles County, in the high desert, near the Kern County line. Lancaster currently ranks as the 30th largest city in California, and the 148th largest city in the United States. Lancaster is the principal city within the Antelope Valley...

, both renamed 10th Street East, from Avenue M to Edwards Air Force Base
Edwards Air Force Base
Edwards Air Force Base is a United States Air Force base located on the border of Kern County, Los Angeles County, and San Bernardino County, California, in the Antelope Valley. It is southwest of the central business district of North Edwards, California and due east of Rosamond.It is named in...

, 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
Plant 42
Air Force Plant 42 is a federally owned military aerospace facility under the control of the Air Force Material Command in Palmdale, California...

 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
Shuttle Carrier Aircraft
The Shuttle Carrier Aircraft are two extensively modified Boeing 747 airliners that NASA uses to transport Space Shuttle orbiters...

. 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 Cocoa, Brevard County, Florida (the county where Cape Canaveral and KSC are located), Challenger 7 Elementary School is named in memory of the seven astronauts who lost their lives. There is also a middle school in neighboring Rockledge, McNair Magnet School, named after astronaut Ronald McNair. A middle school in Boynton Beach, Florida is named after deceased teacher/astronaut, Christa McAuliffe. There is also a school in Lowell, Massachusetts and Lenexa, Kansas named in honor of Christa McAuliffe. The McAuliffe-Shepard Discovery Center, a science museum and planetarium in Concord, New Hampshire
Concord, New Hampshire
The city of Concord is the capital of the state of New Hampshire in the United States. It is also the county seat of Merrimack County. As of the 2010 census, its population was 42,695....

, is also partly named in her honor. There is also an elementary school in Germantown, MD named after Christa McAuliffe.

In 2004, President George W. Bush
George W. Bush
George Walker Bush is an American politician who served as the 43rd President of the United States, from 2001 to 2009. Before that, he was the 46th Governor of Texas, having served from 1995 to 2000....

 conferred posthumous Congressional Space Medals of Honor
Congressional Space Medal of Honor
The Congressional Space Medal of Honor was authorized by the United States Congress in 1969 to recognize "any astronaut who in the performance of his duties has distinguished himself by exceptionally meritorious efforts and contributions to the welfare of the Nation and mankind." The highest award...

to all 14 astronauts lost in the Challenger and Columbia accidents.

External links

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