The Challenger Accident - Essay Example

The Challenger Accident The Space Shuttle Challenger exploded seventy three seconds from liftoff killing all seven crew members during that fateful day of January 28, 1986. The Presidential Commission on the Space Shuttle Challenger Accident, otherwise known as the Rogers Commission, headed by former secretary of state and attorney general William P. Rogers, submitted their findings and results of exhaustive investigation on the cause of the accident, dated June 6, 1986, to then president Ronald Reagan.

The commission in consensus with other agencies involved summarized that the Challenger mishap was caused by the failure “was the destruction of the seals that are intended to prevent hot gases from leaking through the joint during the propellant burn of the rocket motor.” (Presidential Commission on the Space Shuttle Challenger Accident, 1986). The damaged O-ring seals in the tang and clevis joint were found to cause the failure of the seals. The commission’s investigations pointed out several contributing mechanical and structural breaches that lead to the failure.

Among the major structural flaws was a defect in the fittings of the aft joint’s tang and clevis. Original design of the aft segments or other segments of the Solid Rocket Booster has a tang that almost perfectly fits into the clevis of the other segment. This structural design is oftentimes contaminated during handling and transport such that the roundness of the segments is altered due to pressures and transport vibrations. Minor alterations in the roundness of the segments would result to differences in the diameters of the tang and the clevis.

These problems may result to some fitting imperfections that could make the O-rings attached within the joint more vulnerable to damage.Another contributory factor to the failure of the seals was the conditions of the O-rings during launch. It was noted that during launch time, the temperature was very cold and the launch facility even experienced problems due to lower temperature. Furthermore the SRB used in the Challenger launch have been used in several other missions. This practice had been used in the space program without any problems.

For better seal performance, tests confirmed that actuating pressure must get behind the entire face of the O-ring on the upstream side of the groove within which the O-ring sits (Presidential Commission on the Space Shuttle Challenger Accident, 1986, p. 61). Under imperfect sealing conditions discussed above a potential greater pressure is exerted on the O-ring and would make it fit the entire groove. During vibration, under normal conditions, when pressure is relieved, the O-ring contracts and return to uncompressed state providing an effective seal.

However, at lower temperature, the O-rings performance is greatly affected as its contraction to its original shape becomes slower. Its tendency to remain in the groove is possible and could cause possible pressure leakage. The Commission further explained that “low launch temperatures had two effects that could potentially affect the seal performance: (1) O-ring resiliency degradation, the effects of which are explained above; and (2) the potential for ice in the joints. O-ring hardness is also a function of temperature and may have been another factor in joint performance.” (p. 62)Aside from the aforementioned factors, examinations of all other mechanical and structural components and parts of the Challenger mission including the external fuel tank carrying the liquid oxygen and hydrogen, the Orbiter, and the three engines show that everything were running in optimum conditions and that there were no other contributory factors to the accident.

ReferencePresidential Commission On The Space Shuttle Challenger Accident. (1986, June 6). Chapter VI: The Cause of the Accident. June 6, 2008, from http://history.nasa.gov/rogersrep/v1ch4.htm#4.15