1. CHALLENGER DISASTER : CASE STUDY
Samiul A. Chowdhury [ ]
EMSE-6361 Fall Dr. Lawrence Chung Term paper – Interim

2. Overview
Space Shuttle Challenger was second reusable orbiter of NASA's space shuttle program
Disaster occurred on January 28, 1986
Challenger Broke apart 73 seconds into its flight and exploded in midair
Which led the deaths of its all seven crew members

3. Space Shuttle
The Space Shuttle orbiter was the reusable spaceplane component of the Space Shuttle
Orbiter is attached to the large External Tank—the middle cylinder with the sharp-pointed end shown in the figure; the external Tank contains 143,000 gallons of liquid oxygen and 383,000 gallons of liquid hydrogen for the Orbiter's engines.
The two smaller cylinders on the sides of the External Tank are the Solid Rocket Boosters (SRBs).

4. Space Shuttle Challenger
Country: United States
Named after: HMS Challenger (1858) steam-assisted Royal Navy warship
First flight: April 4–9, 1983
Status: Destroyed January 28, 1986
Number of missions: 10
Time spent in space 62 days 07:56:22
Number of orbits: 995
Satellites deployed: 10

5. Solid Rocket Boosters (SRBs).
SRB was almost 150 feet, it was too large to ship as a single unit by rail from Utah to the Kennedy Space Center launch site in Florida.
For this reason it was manufactured from individual cylindrical segments.
SRBs fire for about two minutes after liftoff, and then, their fuel exhausted, are separated from external tank.

6. O-Ring Seals Field joint was sealed with two rubber O-rings
O-rings designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.
Prevents pressurized hot gases and flame to leak

7. Organizations Involved
Marshall Space Flight Center was in charge of booster rocket development
Morton Thiokol - Contracted by NASA to build the Solid Rocket Booster
The shuttle was built by Rockwell International's Space Transportation Systems Division

8. Key People Involved Roger Boisjoly
The engineer who knew challenger has a problem and tried to stop the launch
Larry Mulloy
Marshall’s manager for SRB project.
Challenged the engineers decision not to launch
Alan McDonald
Director of the SRB project at Morton Thiokol

9. The astronauts: seven crew members, which included five NASA astronauts and two Payload Specialists. One of the Payload Specialist Christa McAuliffe, who would have been the first schoolteacher in space.

10. What Happened?
Disintegration of the vehicle began after an O-ring seal in its right SRB failed at liftoff.
The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized burning gas from within the solid rocket motor to reach the outside external fuel tank.
This led to the separation of the right-hand SRB's aft field joint attachment and the structural failure of the external tank.

11. Cont.
Tank exploded and aerodynamic forces broke up the orbiter.
Loss of 7 astronauts (entire crew)
Loss of Challenger
Where?
Over the Atlantic Ocean, off the coast of Cape Canaveral, Florida

12. What Failed?
O-rings were designated as "Criticality 1"—meaning that their failure would result in the destruction of the Orbiter
Joint rotation phenomenon: O-ring joints were supposed to close more tightly due to forces generated at ignition, but due to the effects of booster combustion, the metal parts bent away from each other, opening a gap through which gases leaked
First and Second(safety backup) O-ring seals both failed to prevent the leak
Simplified cross section of the joints
between SRB segments.
Legend: A - steel wall 0.5 inches (12.7 mm) thick B - base O-ring gasket, C - backup O-ring gasket, D - Strengthening-Cover band, E - insulation, F - insulation, G - carpeting, H - sealing paste, I - fixed propellant

13. Why Did it Happened?
SRB temperatures below their redline of 40 °F (4 °C).
The temperature on the day of the launch was far lower than had been the case with previous launches: below freezing at 28 to 29 °F (−2.2 to −1.7 °C)
O-rings were not tested at temperatures below 50 °F (10 °C).
Causing the O-rings to harden
Opening a gap through which hot gases—above 5,000 °F (2,760 °C)—leaked
Right SRB producing a propulsive force that rammed the hydrogen tank into the liquid oxygen tank

14. Key Dates Morton Thiokol awarded contract to build SRBs
1974
1976
1977
1981
1985
Jan 27, 1986
Jan 28, 1986
Morton Thiokol awarded contract to build SRBs
NASA- accepts Morton- Thiokol's booster design.
Morton- Thiokol discovers joint rotation problem. 
O-ring erosion discovered after second shuttle flight. 
NASA Level I management briefed on booster problem. 
Teleconferen ce to discuss effects of cold temperature on booster performance.
Challenger explodes 73 seconds after liftoff.

15. Root Cause
Direct cause of the explosion was technical – faulty design of the SRB, insufficient low temperature testing of the O-ring material that the O-ring sealed
Indirect cause:
The Rogers Commission* found NASA's decision-making processes and lack of communication between different levels of NASA management had been key contributing factors to the accident.
The unrealistically optimistic launch schedule also possible contributing cause to the accident
*Rogers Commission, a special commission appointed by United States President Ronald Reagan to investigate the accident.

16. Problem - Organizational Communication and Ethics
Engineers at Morthon-Thiokol vigorously opposed the launching of Challenger(even before night before launch) , but their warning had not Been heeded by management
Same O-rings engineers had been concerned about for more than eight years
Even O-rings designated "Criticality 1” - no one at Marshall suggested that the shuttles be grounded until the flaw could be fixed.
Top NASA decision makers(at levels I and II) told the commission that they had no knowledge that these had been the subject of intense controversy between Thiokol and Marshall Space Flight Center(level IV and III in the decision-making chain)

17. Cont.
Although O-ring failure was the immediate cause, a flawed decision-making process was an equal, if not more important factor
More than 30 people were in at least 25 communication situations during 1977 – 1982 discussing the O-ring problem, yet none reached Level I or II
While NASA worked on solving the problem, it continued to fly and it defined the Criticality-1 feature as “acceptable” and “unavoidable”.
Mulloy said, “My God, Thiokol, when do you want me to launch – next april?’
Boisjoly recalled that when the shuttle was destroyed a few seconds later, "we all knew exactly what happened.“
NASA officials said they would not have given the final approval to launch if they had heard the views of Thiokol engineers

18. Aftermath
In the first minutes after the accident, recovery efforts were begun Search and rescue aircraft were also dispatched
It took 3 months to recover bodies of crew members
After the Challenger accident, further shuttle flights were suspended, pending the results of the Rogers Commission investigation.
Two-and-a-half year grounding of the shuttle fleet; flights resumed in 1988

19. References
Engineering Ethics: The Challenger Disaster [

20. Thank You