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Prologue

Ever wonder what went wrong with the Space Shuttle Challenger? Do you remember seeing it on TV but being confused by the various reports of the incident? Would you like a simple, easy-to-read, and engaging synopsis of the disaster? If you answered yes to any of these questions, I have posted this research paper for you. I hope it is of some insight.

Little Leaks Sink Great Ships: Lessons from the Space Shuttle Challenger Disaster

Benjamin Franklin, a renowned inventor and Founding Father of the United States, may not have foreseen the tragic manner in which his famous quote, “a small leak can sink a great ship,” would manifest hundreds of years later in one of the most terrible engineering disasters of the twentieth century. On the morning of January 28, 1986, the American space shuttle Challenger disintegrated less than two minutes after its launch, killing its seven crew members and shocking the nation. Later investigation revealed that the primary cause of the disaster was a leak of hot gas which resulted from the failure of the O-ring material used to seal the rocket boosters. As a scientist, Franklin would have desired to investigate this material failure, and engineers today can also glean insight from the mistakes of the Challenger incident.

NASA had experienced problems with shuttle O-rings for years before the Challenger launch. According to the Department of Mechanical Engineering at Texas A&M University, almost half of all previous shuttle flights had experienced severe erosion of the O-ring sealants.1) In the days preceding the shuttle’s launch, engineers from Morton-Thiokol, the contractor which designed the shuttle’s solid rocket boosters, approached NASA with serious concerns about the safety of launching the shuttle on the planned date. Temperatures on the day of the launch were predicted to be around twenty degrees Fahrenheit, lower than the launch temperature for any previous launches. Since the O-rings had never been tested at such a low temperature, the engineers pleaded for NASA to postpone the launch until temperatures rose. However, NASA’s management teams ignored the concerns of Thiokol’s engineers, arguing that since it could not be proven that the launch was unsafe, it was therefore safe. Events would soon prove the flaws in this logic.

On the night before the launch, temperatures dropped to even lower than initially expected. At launch, the shuttle initially appeared stable, despite large amounts of ice on the launchpad and the continued concerns of the engineers. However, fifty-nine seconds into the flight, the shuttle experienced wind shear more violent than that experienced by any other flights. The wind shear continued unabated for another twenty-seven seconds, at which point the solid rocket boosters broke away from the shuttle and the vehicle itself broke apart. Several minutes later, the crew compartment of the shuttle collided with the ocean at over 200 miles per hour, ensuring the death of the seven astronauts on board.

Though many factors were involved in the Challenger disaster, the primary cause of the shuttle’s explosion was the failure of the O-ring material used to seal the joints on the solid rocket boosters.2) For years, NASA and other contractors had used fluorocarbon rubber O-rings to seal these joints and prevent the leakage of solid rocket fuel. However, rubber is a polymer, containing all non-metal elements. As such, it is quite ductile and will respond actively to changes in temperature. Rubber will become more ductile and resilient at higher temperatures and more brittle and stiff at lower temperatures, characteristics it shares with many other materials. The joints of Challenger’s solid rocket boosters depended upon the ductility and resilience of the rubber O-ring material in order to seal properly.3) Sadly, because NASA did not heed the warnings of the Morton-Thiokol engineers, the rubber O-rings were too cold to seal properly on the morning of the launch. Consequently, extremely hot exhaust gases burned their way past the O-rings into the solid rocket boosters’ fuel tanks and ignited the solid rocket fuel, which led to the explosion of the shuttle and the deaths of seven Americans.

The effects of the Challenger disaster continue to linger even today, almost thirty years later. At the time of the disaster, NASA had never experienced such a terrible accident, and the country was beginning to place great faith in the ability of the agency to conquer the “Final Frontier” of space. However, as eloquently summarized by President Ronald Reagan in the speech he delivered on the eve of the accident, “all the people of our country” were shocked.4) Ever since the accident, the US space program has drawn fiery debate and concern from different quarters of society, especially because several other notable space tragedies have occurred since that time. For certain, the accident caused NASA to seriously re-evaluate its commitment to safety and to listen more closely to its engineers.5) Regarding the design of the shuttle, NASA replaced the fluorocarbon rubber O-rings used for all previous flights with fluorosilicone rubber rings which had a much higher resiliency and resistance to temperature change. Furthermore, the O-rings were surrounded with heating strips to maintain them at a temperature of at least seventy-five degrees Fahrenheit regardless of the outside temperature.6) Never again would NASA make a similar mistake.

For budding generations of engineers, the Challenger disaster offers grave warnings and lessons about the importance of material selection and application. For NASA, the engineers at Morton Thiokol, and the United States at large, the Challenger disaster was a heartbreaking setback which nearly crippled the US space exploration program. The scientific work of decades and the hopes of humanity for centuries seemed engulfed in the fireball which destroyed the most technologically advanced human machine in the world at that time. But for the families of the Challenger astronauts, the disaster held much more emotional and lasting significance. Their lives were forever changed by this engineering disaster, and no amount of successful engineering in the future can ever reclaim their loved ones. The most significant lesson to be learned from the Challenger disaster is the grave responsibility of all engineers to the society for which they build. Future generations of engineers would do well to heed the pithy wisdom of Franklin as they help to move human civilization even further towards the stars.

Engineering Science Disasters

1) “The Space Shuttle Challenger Disaster.” Engineering.com. http://www.engineering.com/Library/ArticlesPage/tabid/85/ArticleID/170/The-Space-Shuttle-Challenger-Disaster.aspx (accessed March 17, 2013).
2) Richard S. Lewis, Challenger: The Final Voyage (New York: Columbia University Press, 1988), 216.
3) Allan J. McDonald, Truth, Lies, and O-Rings: Inside the Space Shuttle Challenger Disaster (Florida: University Press of Florida, 2009), 100.
4) Ronald Reagan, “Speech on the Challenger Disaster,” January 28, 1986. http://teachingamericanhistory.org/library/index.asp?document=147 (accessed March 21, 2013).
5) Lewis, 216.
6) Ibid, 223.

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