Challenger — What Happened
, Why the Shuttle Broke Apart, and What NASA Learned
On the morning of 28 January 1986, the Space Shuttle Challenger lifted off from Kennedy Space Center in Florida.
Seventy-three seconds later, the vehicle broke apart high above the Atlantic Ocean.
All seven crew members were killed.
Millions of people watched the disaster unfold live on television.
Among them were schoolchildren across the United States, many following the mission because teacher Christa McAuliffe was aboard as part of NASA’s Teacher in Space Project.
The loss of Challenger became one of the most shocking moments in the history of human spaceflight.
But the disaster was not caused by a mysterious or completely unforeseen technical malfunction.
The weakness that destroyed Challenger was known.
Engineers had warned about it.
The unusually cold launch conditions made the danger worse.
And the decision-making process that allowed the shuttle to launch became almost as important as the physical failure itself.
What Was Space Shuttle Challenger?
Challenger was the second operational spacecraft in NASA’s Space Shuttle fleet.
Officially designated OV-099, it began operational service in 1983.
Unlike earlier spacecraft that were used once and discarded, the Space Shuttle was designed as a partially reusable transportation system.
The orbiter carried astronauts and cargo into space while two enormous solid rocket boosters provided much of the thrust during launch.
Between them sat the large external fuel tank supplying liquid hydrogen and liquid oxygen to the orbiter’s main engines.
Challenger successfully completed nine missions before its final flight.
Mission STS-51-L was intended to become its tenth.
Who Was Aboard Challenger?
Seven people were aboard:
- Commander Francis R. “Dick” Scobee
- Pilot Michael J. Smith
- Mission Specialist Ronald McNair
- Mission Specialist Ellison Onizuka
- Mission Specialist Judith Resnik
- Payload Specialist Gregory Jarvis
- Teacher-in-Space participant Christa McAuliffe
McAuliffe’s presence gave the flight unusual public attention.
She had been selected from thousands of teachers and was expected to conduct lessons from orbit.
For many Americans, Challenger therefore represented not simply another NASA mission but an opportunity to bring ordinary citizens closer to the space programme.
The Mission
STS-51-L was scheduled to deploy communications satellites and conduct scientific experiments.
The mission had already suffered several delays.
By the morning of 28 January, NASA faced increasing pressure to get Challenger into the air.
The weather, however, presented a serious concern.
Florida was experiencing unusually cold conditions.
Temperatures overnight had fallen below freezing.
Ice had formed around parts of the launch structure.
More importantly, engineers working for Morton Thiokol, the company responsible for the shuttle’s solid rocket boosters, were deeply concerned about what the cold might do to critical seals inside the booster joints.
The Solid Rocket Boosters
The Space Shuttle’s two solid rocket boosters were built from several cylindrical segments joined together.
Each joint needed to prevent extremely hot combustion gases from escaping.
This sealing system depended upon rubber rings known as O-rings.
When pressure built inside the booster after ignition, the O-rings were supposed to move rapidly into position and create a gas-tight seal.
Engineers had already seen evidence from earlier shuttle flights that hot gases could partially erode these seals.
This phenomenon was known as O-ring erosion or blow-by.
The problem was not entirely new.
What became critical before Challenger’s launch was the relationship between O-ring performance and temperature.
The Cold Weather Problem
Rubber becomes less flexible when it is cold.
For the booster O-rings, that mattered enormously.
If the seals responded too slowly after ignition, hot gas could escape through the joint before the rings properly sealed.
Morton Thiokol engineers had become concerned that lower temperatures increased this risk.
The predicted temperature at launch was far colder than temperatures experienced during previous shuttle launches.
On the evening before launch, Thiokol engineers participated in a conference call with NASA officials.
They recommended delaying the launch.
The Engineers’ Warning
Among those most concerned was engineer Roger Boisjoly, who had previously warned that a booster joint failure could result in catastrophic loss of the shuttle.
During the pre-launch discussions, Thiokol initially recommended that Challenger should not launch below approximately 53°F — 12°C.
The expected launch temperature was much lower.
NASA managers challenged the reasoning and asked Thiokol to reconsider.
Thiokol management then held a private discussion.
The company’s recommendation changed.
Despite the concerns raised by its engineers, Thiokol ultimately advised that the launch could proceed.
Challenger remained cleared for flight.
Launch Morning
The morning of 28 January was extraordinarily cold for a Florida shuttle launch.
Ice was visible around the launch pad.
NASA teams monitored the conditions and assessed whether falling ice might damage the shuttle.
The launch was delayed while temperatures rose.
Eventually, at 11.38am Eastern Time, the countdown reached zero.
The main engines ignited.
Then the solid rocket boosters fired.
Challenger lifted away from Launch Pad 39B.
For the first minute, the flight appeared largely normal.
But almost immediately after ignition, something dangerous had happened inside the right-hand solid rocket booster.
The O-Ring Failure
The extreme cold had reduced the ability of the O-rings in one joint of the right solid rocket booster to seal quickly.
Hot combustion gases escaped through the joint.
For a short period, aluminium oxides and other combustion products appear to have temporarily sealed the opening.
Challenger continued climbing.
Then the shuttle encountered strong aerodynamic forces.
Movement in the booster joint disrupted the temporary seal.
A flame began escaping from the side of the right booster.
The plume was visible in launch imagery.
The crew had no way of knowing what was happening behind them.
The External Tank
The escaping flame struck the shuttle’s enormous external fuel tank.
The tank contained liquid hydrogen and liquid oxygen.
Eventually, the flame damaged the structures connecting the booster to the tank and contributed to failure of the tank itself.
Approximately 73 seconds after launch, Challenger was travelling at high speed through the atmosphere when the vehicle broke apart.
The familiar image often described as an explosion was actually a rapid structural breakup involving enormous quantities of propellant.
The orbiter was destroyed by aerodynamic forces.
Debris spread across the Atlantic.
What Happened to the Crew?
The crew cabin separated from the disintegrating orbiter.
Evidence recovered later indicated that several emergency oxygen packs had been activated, suggesting that at least some crew members survived the initial breakup.
The exact condition of the astronauts during the descent cannot be established with certainty.
The crew compartment continued falling for more than two minutes before striking the Atlantic Ocean at very high speed.
The impact was unsurvivable.
All seven crew members died.
The Immediate Aftermath
The launch broadcast fell silent.
Mission Control initially struggled to understand what had happened.
Within moments, however, the scale of the disaster became apparent.
NASA suspended shuttle operations.
Search vessels and aircraft moved into the Atlantic to recover wreckage.
Large sections of Challenger were eventually retrieved from the sea.
The recovery operation was both technically important and emotionally difficult.
Investigators needed the debris to reconstruct the sequence of failure.
The Rogers Commission
President Ronald Reagan established the Presidential Commission on the Space Shuttle Challenger Accident, commonly known as the Rogers Commission.
It was chaired by former Secretary of State William P. Rogers.
Its members included astronauts, scientists, engineers and other specialists.
One of the most famous members was physicist Richard Feynman.
The commission investigated not only the physical cause of the disaster but also NASA’s management culture and decision-making.
Its findings transformed public understanding of Challenger.
Richard Feynman’s Demonstration
During a televised commission hearing, Feynman carried out a simple but memorable demonstration.
He placed a sample of O-ring material into a glass of ice water.
After cooling it, he compressed the rubber and showed that it recovered its shape much more slowly.
The demonstration made an immensely complicated engineering problem immediately understandable.
Cold rubber did not respond as quickly.
And a delayed response in a solid rocket booster joint could allow hot gas to escape.
The physical vulnerability of the O-rings had become impossible to ignore.
The Cause of the Disaster
The Rogers Commission concluded that Challenger was destroyed because the seals in a joint of the right solid rocket booster failed.
The unusually cold temperature contributed directly to that failure.
But the commission went further.
The accident was also the product of serious weaknesses in NASA’s decision-making processes.
Evidence of O-ring erosion had been seen during earlier flights.
Instead of treating that evidence as proof of an unacceptable design problem, the organisation gradually came to regard it as manageable.
A warning sign had become normalised.
Normalisation of Deviance
Challenger later became a classic example of what sociologists call the normalisation of deviance.
Small departures from expected performance occur.
Nothing catastrophic happens.
The departure is therefore gradually accepted as safe.
The next departure becomes easier to tolerate.
Eventually, abnormal behaviour becomes treated as normal.
Previous shuttle missions had shown O-ring erosion without causing catastrophe.
Success therefore created confidence.
But successful survival of an abnormal condition did not mean the condition was safe.
It meant the system had been fortunate.
On 28 January 1986, that margin disappeared.
Schedule Pressure
NASA was attempting to operate the Space Shuttle at a demanding flight rate.
The shuttle programme had originally been promoted as a reusable and relatively routine means of reaching orbit.
By the mid-1980s, the agency faced political, financial and scheduling expectations.
Challenger had already been delayed several times.
None of this means someone consciously decided to sacrifice safety for a timetable.
The danger was subtler.
Pressure can change how uncertainty is interpreted.
Instead of asking whether the launch had been proven safe, the discussion increasingly centred upon whether engineers could prove it was unsafe.
That reversal became one of the most troubling aspects of the Challenger decision.
Why Did NASA Launch?
There was no single explanation.
The launch resulted from several interacting factors:
- confidence built from previous successful missions;
- incomplete understanding of the relationship between temperature and O-ring performance;
- weaknesses in communication between engineers and managers;
- pressure to maintain the shuttle schedule;
- management acceptance of previously observed O-ring erosion;
- the reversal of Morton Thiokol’s initial recommendation not to launch.
The physical failure occurred inside the booster.
The organisational failure occurred before ignition.
Were the Engineers Ignored?
Several engineers had repeatedly raised concerns about the booster joints.
Roger Boisjoly had been particularly forceful in warning that the problem could lead to disaster.
On the evening before launch, Thiokol engineers recommended postponement because of the cold.
Their concerns were not simply dismissed without discussion.
They were debated.
But the management process eventually overrode the engineers’ initial recommendation.
That distinction matters.
Challenger was not a disaster where nobody recognised the danger.
The danger was recognised but inadequately acted upon.
Could Challenger Have Been Saved?
Once the booster joint began leaking significantly during launch, the crew had virtually no practical means of escaping.
The Space Shuttle did not possess a full launch escape system comparable with those used on some earlier and later crewed spacecraft.
At certain stages of flight, emergency procedures existed, but the Challenger failure happened too quickly and under conditions that made meaningful crew intervention impossible.
The most effective opportunity to save the astronauts existed before launch.
The mission needed to remain on the ground.
Was Challenger an Explosion?
The description is understandable, but technically the shuttle did not simply detonate like a bomb.
The failure of the booster and external tank produced a massive release of fuel and structural breakup.
Aerodynamic forces then destroyed the orbiter.
The enormous clouds visible in photographs and television footage were formed largely from propellants released as the vehicle disintegrated.
To observers, it looked like an explosion.
Operationally, however, the key event was catastrophic structural failure.
The Public Shock
Challenger was different from earlier spaceflight accidents because millions witnessed it live.
Schools had organised viewings because of Christa McAuliffe’s participation.
Children watched the launch expecting to see a teacher travel into space.
Instead, they saw the shuttle disappear.
President Reagan postponed his planned State of the Union address and spoke to the nation that evening.
The disaster became embedded in American public memory.
The Shuttle Programme Stops
NASA grounded the Space Shuttle fleet for nearly three years.
The solid rocket booster joints were extensively redesigned.
Management structures and safety procedures were also changed.
NASA created stronger mechanisms for independent safety oversight.
The shuttle did not return to flight until 29 September 1988, when Discovery launched on mission STS-26.
The return was deliberately cautious.
Challenger had demonstrated that successful previous flights could never be treated as proof that unresolved engineering concerns were acceptable.
What Changed in the Boosters?
The solid rocket booster field joints underwent major redesign.
The new design improved sealing and incorporated additional features intended to prevent the type of failure that destroyed Challenger.
Heaters were also added in critical areas to reduce sensitivity to cold conditions.
Testing procedures became more rigorous.
The engineering solution was important.
But changing hardware was easier than changing organisational culture.
The Management Lessons
The Rogers Commission criticised serious shortcomings in communication within NASA.
Critical engineering concerns did not always travel effectively through management structures.
The organisation had also become too accepting of risk.
The central lesson was uncomfortable.
Highly capable institutions can still make dangerous decisions when experience gradually persuades them that warning signs are less serious than they appear.
Technical expertise alone is not enough.
Organisations must create conditions in which unwelcome information can travel upwards without being weakened, filtered or rationalised away.
The Columbia Connection
Seventeen years later, NASA suffered another shuttle disaster.
Space Shuttle Columbia broke apart during re-entry on 1 February 2003, killing all seven astronauts aboard.
The physical cause was entirely different.
A piece of insulating foam had struck Columbia’s wing during launch, creating damage that allowed superheated gases to enter during re-entry.
Yet investigators again identified disturbing similarities in organisational behaviour.
Warnings had become normalised.
Previous survival had created confidence.
Uncertainty had been interpreted optimistically.
The fact that NASA encountered comparable organisational weaknesses after Challenger demonstrated how difficult cultural lessons can be to preserve over time.
The Legacy of Challenger
Challenger changed human spaceflight.
It ended any illusion that Space Shuttle launches had become routine.
It demonstrated the danger of allowing repeated success to redefine unacceptable technical behaviour as normal.
And it became a powerful lesson in the importance of listening to engineers closest to a problem.
The seven crew members became symbols of exploration and public service.
But their loss also carries a more uncomfortable legacy.
The accident was preventable.
The physical weakness was known.
The launch conditions were unusually hazardous.
Warnings were given.
The failure was therefore not simply a tragedy of space exploration.
It was a tragedy of decision-making.
Frequently Asked Questions
When did Challenger break apart?
Space Shuttle Challenger broke apart on 28 January 1986, approximately 73 seconds after launch.
How many people died?
All seven crew members were killed.
What caused the Challenger disaster?
A seal in the right solid rocket booster failed, allowing hot gases to escape. Extremely cold weather reduced the ability of the O-rings in the booster joint to seal properly.
Why was the launch allowed to proceed?
Engineers had raised concerns about the effect of cold temperatures on the O-rings, but management discussions eventually resulted in approval to launch.
What temperature was it?
The temperature at launch was approximately 36°F, or about 2°C, considerably colder than during previous shuttle launches.
Who was Christa McAuliffe?
Christa McAuliffe was a New Hampshire teacher selected for NASA’s Teacher in Space Project. She was intended to teach lessons from orbit.
Did the astronauts survive the initial breakup?
Evidence suggests that at least some crew members survived the immediate vehicle breakup, but their exact condition during the subsequent descent cannot be known with certainty. The impact with the Atlantic Ocean was unsurvivable.
Was Challenger destroyed by an explosion?
The vehicle suffered catastrophic structural breakup after the booster failure damaged the external tank and surrounding structures. The event appeared as a huge explosion because large quantities of propellant were released.
Who investigated the disaster?
The principal presidential investigation was conducted by the Rogers Commission.
When did the Space Shuttle fly again?
NASA returned the shuttle fleet to flight on 29 September 1988 with Space Shuttle Discovery.
Read the Full Book
For a deeper examination of the engineering warnings, launch decision, O-ring failure and organisational culture behind the Challenger disaster, read the full investigation by Bill Stewart.
Available on Amazon.
https://www.amazon.com/dp/B0H6WQLF6G
Read More
Explore more What Happened? investigations on Billy’s Book Club, examining maritime disasters, aviation accidents, spaceflight tragedies, industrial catastrophes and historical events where technical failure and human decision-making combined with devastating consequences.
About the Author
Bill Stewart is an author and former seafarer whose career included service in the Royal Navy and Merchant Navy, followed by work in marine auditing and accident investigation.
His nonfiction writing examines major disasters, unexplained events, intelligence operations and historical investigations, with particular emphasis on separating documented evidence from speculation.
His books and What Happened? Investigation Pages form part of the nonfiction archive at Billy’s Book Club — Books Worth Talking About.