Introduction
This case study reviews the loss of the NASA Space Shuttle “Challenger” STS Mission 51-L in 1986, when it exploded shortly after launch, resulting in the deaths of all seven astronauts on board. The research looks at the causes of the accident, the structural and mechanical factors involved, other contributory factors, and the findings of the Investigation Board.
The Research
Causes of the Accident. The main cause was found to be a failed O-ring seal in the right side Solid Rocket Booster (SRB), resulting from exceptionally low ambient temperatures at launch (“Space Shuttle Challenger Disaster”, updated Feb 2013).
Although that seal failure was recorded as the primary cause of the accident, there had been issues that caused engineers involved to express concerns regarding the already much-delayed launch, but those concerns were overruled by the senior NASA people in charge of the already-postponed launch, which eventually took place on a really cold January morning (“Space Shuttle Challenger Disaster”, updated Feb 2013).
Structural and Mechanical Factors. The principal mechanical factor involved in the sense that it was the trigger for all that followed was the failure of the SRB O-ring seal, which should have prevented the SRB hot gases leaking at that joint. According to “Space Shuttle Challenger” (n.d.) published by the Frostburg State University, two reasons for that leak were: a) The low temperature of the air at launch (36 degrees F.; some 15 degrees less than any previous launch and cold enough that ice had formed on the vehicle and on the pad), and b) at that joint, there were “significant out-of-round conditions” in part due to the two SRB segments having been re-used. The very low ambient temperature affected the resiliency – and therefore its sealing capability – of the O-ring, which at (say) 75 degrees F. is 5 times as resilient as one at 30 degrees F.
Also reported in the same case study as above, the resultant flames playing onto the external fuel tank and a strut linking that tank to the shuttle caused structural failure of both the strut and the fuel tank, which caused complete breakup of the space vehicle.
Contributing Factors. Forrest (Aug 2005) cited the first factor contributing to the disaster as one of a flawed human decision to launch; itself a product of NASA’s “Group Decision Support System” (GDSS). From this article, it would appear that in meetings that ultimately resulted in the launch decision, anonymous voting was not possible and that anyone departing from the party line risked removal from the program.
Also, it was reported that the engineers from Thiokol (the company who made the O-rings) tried on the eve of the ill-fated launch to have it postponed, stating the O-rings were not designed for such low temperatures, but were “persuaded” by their own senior management and senior NASA officials to change their recommendation. Also, NASA itself was under severe pressure to proceed with the launch, having already had several launches cancelled in the preceding year.
Another contributing factor referred to in “The Space Shuttle Challenger Disaster: A Study in Organizational Ethics” (Oct 2006) was that President Reagan had urged NASA to make as a many shuttle launches as possible to make the program a commercial success. That resulted in pressures within NASA to almost launch at all costs, pushing engineering and safety considerations to one side.
Investigation Board Findings. According to Gregory, Marcellino & Moyer (Sep 2006), the Reagan-appointed Rogers Commission, presented a total of sixteen findings, all associated with technical aspects of the O-ring problem (p. 10).
Specifically, the Rogers Commission Report concluded that:
the Challenger accident was the failure of the pressure seal in the aft field joint of the right Solid Rocket Booster. The failure was due to a faulty design unacceptably sensitive to a number of factors. These factors were the effects of temperature, physical dimensions, the character of materials, the effects of reusability, processing and the reaction of the joint to dynamic loading. (“Report of the Presidential Commission on the Space Shuttle Challenger Accident”, Feb 1986, p. 40).
Recommendations. The Rogers Commission presented nine recommendations to President Reagan / NASA, only one specifically addressing redesign of that SRB joint. Of the remaining eight, four concerned other technical and/or maintenance aspects, and four recommended changes to the organization of NASA and its management and communications systems. (Gregory, Marcellino & Moyer, Sep 2006).
Two key recommendations were a) to establish within NASA an “STS Safety Advisory Panel” that would report directly to the Shuttle Program Manager and would have a remit that would include matters concerning launch safety issues, and b) to improve communications within NASA “by changes of personnel, organization, indoctrination or all three.” (Gregory, Marcellino & Moyer, Sep 2006).
Outcomes. An immediate effect of the Challenger disaster was a 3-year suspension of the space shuttle program (Chow, 2011).
Also, according to Lethbridge (n.d.), the nine Rogers Commission findings were acted upon by NASA, who also instituted “a more relaxed Space Shuttle Launch Schedule”, reducing the pressure for shuttle launches at the possible expense of safety.
References
Chow, D. (Jan 2011). “Space Shuttle Challenger Disaster FAQ: What Went Wrong.” Space.com. Retrieved from http://www.space.com/10677-challenger-tragedy-overview.html
Forrest, J. (Aug 2005). “The Space Shuttle Challenger Disaster: A failure in decision support system and human factors management.” Metropolitan State College. Retrieved from http://dssresources.com/cases/spaceshuttlechallenger/
Gregory, R., Marcellino, S. & Moyer, S. (Sep 2006). “Analysis of NASA’s Post-Challenger Response and Relationship to The Columbia Accident and Investigation.” Naval Postgraduate School, Monterey, California. Retrieved from http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA456946
Lethbridge, C. (n.d.). “The Challenger Legacy.” Spaceline. Retrieved from http://www.spaceline.org/challenger.html
“Report of the Presidential Commission on the Space Shuttle Challenger Accident.” (Feb 1986). Kennedy Space Center. Retrieved from http://science.ksc.nasa.gov/shuttle/missions/51-l/docs/rogers-commission/table-of-contents.html
“Space Shuttle Challenger.” (n.d.). Frostburg State University. Retrieved from http://antoine.frostburg.edu/phys/invention/case_studies/disasters/challenger.html
“Space Shuttle Challenger Disaster.” (Updated Feb 2013). Aerospace Guide. Retrieved from http://www.aerospaceguide.net/spaceshuttle/challenger_disaster.html
“The Space Shuttle Challenger Disaster: A Study in Organizational Ethics.” (Oct 2006). Seton Hall University. Retrieved from http://pirate.shu.edu/~mckenndo/pdfs/The%20Space%20Shuttle%20Challenger%20Disaster.pdf
