Space Shuttle Challenger Disaster (1986): What Went Wrong

The Space Shuttle Challenger disaster occurred on 28 January 1986, when the orbiter broke apart 73 seconds after lifting off from Kennedy Space Center in Florida, killing all seven people on board. The cause was the failure of rubber O-ring seals in a solid rocket booster on an unusually cold morning. Watched by millions, including schoolchildren following the first teacher in space, the accident exposed deep flaws in how NASA weighed risk.

Background: the shuttle and the teacher in space

By early 1986 NASA’s Space Shuttle had flown 24 missions since the first flight in 1981. The agency had promised a reliable, almost airline-like space truck that would fly frequently and cheaply, and it was under pressure to increase the launch rate. Fifteen flights were planned for 1986.

In 1984 President Ronald Reagan announced the Teacher in Space Project, intended to show that ordinary citizens could fly. More than 11,000 teachers applied. In July 1985 NASA chose Christa McAuliffe, a social studies teacher from Concord, New Hampshire, with Barbara Morgan as her backup. McAuliffe planned to give lessons broadcast from orbit.

Mission STS-51-L was to be Challenger’s tenth flight. Its main tasks were to deploy a NASA tracking and data relay satellite and to fly a small free-flying satellite to observe Halley’s Comet.

The crew

• Francis “Dick” Scobee: commander, a former Air Force test pilot.
• Michael J. Smith: pilot, a Navy aviator on his first spaceflight.
• Judith Resnik: mission specialist, electrical engineer, the second American woman in space.
• Ellison Onizuka: mission specialist, the first Asian American in space.
• Ronald McNair: mission specialist, physicist and the second African American in space.
• Gregory Jarvis: payload specialist, an engineer from Hughes Aircraft.
• Christa McAuliffe: payload specialist, the Teacher in Space.

The O-ring problem

Each shuttle launch used two solid rocket boosters, built in segments by Morton Thiokol in Utah. The joints between segments, called field joints, were sealed by two rubber O-rings designed to stop hot combustion gas escaping.

Inspections of recovered boosters had shown erosion and “blow-by” of the O-rings on several earlier flights. The worst damage had followed the coldest previous launch, in January 1985, when the air temperature was about 12 degrees Celsius (53 degrees Fahrenheit). Cold rubber is stiffer and slower to seal. In 1985 Thiokol engineer Roger Boisjoly had written internal memos warning that a joint failure could lead to the loss of a shuttle.

Instead of grounding the fleet, NASA and Thiokol came to treat the damage as an acceptable risk because earlier flights had survived it. The sociologist Diane Vaughan later called this pattern the “normalization of deviance”.

The launch decision

The launch had been postponed several times from 22 January, because of delays to the previous mission, bad weather and a problem with a hatch handle. A severe cold front then hit Florida, with forecasts of overnight temperatures well below freezing.

On the evening of 27 January, Thiokol engineers, including Boisjoly and Allan McDonald, told NASA managers in a teleconference that they should not launch below about 12 degrees Celsius. Officials at NASA’s Marshall Space Flight Center challenged the data. During an off-line caucus, Thiokol’s senior managers reversed their engineers’ recommendation and approved the launch. Concerns about ice on the launch pad were also raised the next morning, but the countdown continued.

What happened on 28 January 1986

Challenger lifted off at 11:38 a.m. local time. The air temperature was about 2 degrees Celsius (36 degrees Fahrenheit), far colder than any previous launch, and parts of the right booster were colder still.

Less than a second after ignition, puffs of black smoke came from the aft field joint of the right booster, showing that the O-rings had failed to seal. Burnt aluminium oxide from the propellant temporarily plugged the gap. About 58 seconds into the flight, after the vehicle passed through strong wind shear, a plume of flame appeared at the joint.

The flame burned into the strut attaching the booster to the large external fuel tank, and into the tank itself. At about 72 seconds the lower strut failed, the booster swung inward and the tank’s structure broke up, releasing liquid hydrogen and oxygen that burned in a huge fireball. At 73 seconds, at an altitude of about 14 kilometres (46,000 feet), Challenger was torn apart by aerodynamic forces. The two boosters flew on erratically until they were destroyed by the range safety officer.

The fate of the crew

The reinforced crew cabin separated from the orbiter largely intact and continued upward before falling into the Atlantic Ocean, which it struck at more than 300 kilometres per hour about two and three-quarter minutes after the break-up. Several of the crew’s emergency air packs had been activated, suggesting that at least some crew members were alive after the break-up. NASA’s investigation could not determine the exact cause or time of death.

The cabin was located on the seabed in March 1986, and the crew’s remains were recovered. Much of the debris recovered from the ocean was later sealed in disused missile silos at Cape Canaveral.

The nation’s response

The launch was carried live by NASA’s own television feed, which many schools had tuned in to because of McAuliffe, and by the cable news channel CNN. Replays were broadcast repeatedly, and most Americans had heard of the accident within hours.

Reagan postponed his State of the Union address, planned for that evening, and spoke to the nation from the Oval Office. He ended by quoting the poem “High Flight”, saying the crew had “slipped the surly bonds of earth” to “touch the face of God”.

The Rogers Commission

Reagan appointed a presidential commission chaired by former Secretary of State William P. Rogers. Its members included Neil Armstrong as vice-chairman, the astronaut Sally Ride, Air Force General Donald Kutyna, the test pilot Chuck Yeager and the physicist Richard Feynman.

At a televised hearing in February 1986, Feynman dropped a piece of O-ring material clamped in a small C-clamp into a glass of iced water to show that it lost its resilience in the cold. In his personal appendix to the report he wrote that “reality must take precedence over public relations, for nature cannot be fooled.”

The commission’s report, delivered in June 1986, concluded that the accident was caused by the failure of the pressure seal in the aft field joint of the right booster. It also found a “flawed” decision-making process: concerns had not reached NASA’s top managers, and the launch had gone ahead despite engineers’ objections. It criticised NASA’s flight schedule as unrealistic and its safety organisation as weak.

Consequences and legacy

The shuttle fleet was grounded for about 32 months. The booster joints were redesigned with a third O-ring, a capture feature to limit joint movement and heaters. NASA created a new Office of Safety, Reliability and Quality Assurance, gave astronauts a greater role in management and added a pole-based bailout system for some flight phases.

The government also decided that the shuttle would no longer launch most commercial satellites, which helped the growth of expendable rockets. A replacement orbiter, Endeavour, was ordered and first flew in 1992. Flights resumed with Discovery on mission STS-26 on 29 September 1988.

Legacy

The families of the crew founded the Challenger Center for Space Science Education, which runs learning centres for students. Memorials stand at Arlington National Cemetery and at Kennedy Space Center. Barbara Morgan, McAuliffe’s backup, flew to the International Space Station as a mission specialist in 2007.

Challenger became a standard case study in engineering ethics and organisational behaviour. Its lessons were tested again in 2003, when the Columbia disaster investigators found that many of the same cultural problems had returned.

Myths and facts

• Myth: Challenger exploded like a bomb. The external tank broke up and its propellants burned, but the orbiter was destroyed by aerodynamic forces; there was no detonation in the usual sense.
• Myth: the whole nation watched live on television. The major broadcast networks were not showing the launch live; most people saw replays. Many schoolchildren did see it live through NASA’s feed.
• Myth: the crew died instantly. Evidence suggests some crew members survived the break-up, though the exact cause and moment of death could not be determined.

By the numbers

Timeline

• 1985, July: Christa McAuliffe is chosen as the Teacher in Space.
• 1986, 22 January: The originally scheduled launch date passes after delays.
• 1986, 27 January: Thiokol engineers argue against a cold-weather launch; managers approve it.
• 1986, 28 January: Challenger breaks apart 73 seconds after liftoff; all seven crew die.
• 1986, 3 February: Reagan establishes the Rogers Commission.
• 1986, 11 February: Feynman’s iced-water demonstration at a public hearing.
• 1986, March: The crew cabin is found on the ocean floor.
• 1986, June: The Rogers Commission delivers its report.
• 1988, 29 September: Discovery launches on STS-26 and shuttle flights resume.

Why it matters

The Challenger disaster showed that a known technical flaw, combined with schedule pressure and poor communication, could turn into catastrophe. It reshaped NASA, ended the idea of the shuttle as a routine space truck and remains one of the most studied failures in engineering history.