Case Study NASA Challenger Disaster 关于挑战者号事故原因的分析和风险控制模型分析

CASE STUDY 5. NASA CHALLENGER DISASTER

The Challenger Disaster was an aerospace accident with 7 deaths happened on 28 January 1989, when the NASA space shuttle Challenger disintegrated and exploded 73 seconds after its launch. A special commission was formed to investigate the reason behind this disaster and result shown that the failure of the O-ring which seals the right solid rocket booster (RSB) was the direct cause of this accident. At the launching day, the ambient temperature was far below usual. At the low temperature, the O-ring lost its ability of expansion which created a breach for pressurized burning gas to burn through and jet out. The space shuttle disintegrated and exploded at 40’000 feet above the ground. Other than the technical failure, the investigation also revealed more problems about the communication and project management. The night before the disaster, there were dispute between the opinions of engineering team and project managers. The engineering team suggested to postpone the launch under 53°F while NASA tended to stick with the plan. Ineffective communication made the engineers failed to provide strong evidence of possible failure hence not able to persuade NASA to pay attention to the risk of low temperature. The manager team of Thiokol overridden the engineers and made the recommendation of launch. Then NASA made the decision to proceed to launch based on inadequate and misleading information. Also, it was the managerial structure of NASA allowed the negligence towards the potential safety risk in this space shuttle project.

There were multiple factors which contributed to the O-ring failure so there are several parties to shoulder the responsibility. Firstly, technical failure can often be attributed to engineers who have the obligation to produce the safe design and make improvement when necessary. The problems associated with O-ring seal was not new to Thiokol before the Challenger disaster. By the time of Mission 51C in 1985, a number missions had yielded disturbing O-ring erosion. NASA had designated the O-ring as “Critical ity 1” item which means the failure in this item could cause the loss of shuttle and lives. However, even with the frequently warning signs from such a critical part, the engineers in Thiokol did not provide an effective remedy nor call pause to future mission. Secondly, it was a faulty movement for the management team in Morton Thiokol overridden the engineering team and made the recommendation to proceed to launch. During a teleconference in the eve of event, technical crews shown their concerns about the performance of O-ring in low temperature and given clear suggestion that should not launch at below 53°F. However, under the pressure of NASA, the general manger in Thiokol decided not to listen to the engineers who against launch. Not long after, the manager team provided the recommendation “No temperature requirement of launch” to NASA. Thirdly, NASA was also responsible for its cavalier attitude towards the risk of lives, even after being shown the concerns of possible failure.

As mentioned above, the design engineers did not carry the professional responsibility to solve the safety problem after the several erosion happened. In 1985, the Mission STS 51C was a launch performed in a freezing condition of 51.8°F and can be considered as a serious warning. The technical team found evidence of burn through on the primary O-ring by recovery of booster nozzle. Thiokol then started to notice the correlation between low temperature and possibility of seal “blow-by”. The examination of following mission 51B also indicated erosion problem on secondary O-ring seal. A structural engineer of Thiokol expressed him concern over the O-ring and recommended to build a team to resolve the problem. The task force was formed later but did not solve the problem since their efforts often frustrated by senior management. By the time of the teleconference before the launch of Challenger, the engineers did not even had not done enough test to provide a solid evidence about the relationship between temperature and O-ring’s functionality. More over, during the teleconference, the engineers did a poor job on communication with NASA administrators about the potential risk and consequences. It was important to deliver the concern to the right ear but they failed to do so.

The management scheme of NASA was questionable during and after the disaster. The issues with the O-rings were acknowledged by NASA through the previous missions. However, NASA did not request a detailed investigation. Instead, it increased its tolerance level to ignore the potential problem. One potential reason could be that NASA was facing schedule pressure. Onward from the glory days of Apollo project, NASA was facing an increasingly significant financial problem so NASA has to perform more commercial launches to raise public fund. Moreover, in 1982, President Reagan announced a space policy in which it stated that the space shuttle should provide routinely access to space while be both fully operational and cost effective. In this situation, NASA even managed to launch every fortnight. Tight Schedule Plus tight funding made NASA tend to overlook the risk and hence made the decision to prioritise the schedule over the wellbeing of astronauts.

There were also ethical issues involved in the disaster. In the eve of Challenger launch, Thiokol requested a five-minute recess from the teleconference to evaluate the situation, during that time, the general managers of Thiokol downplayed the concern of launch objectors and collectively voted to give launch recommendation to NASA. Engineers were ruled out of signing the recommendation and then given up on whistle blowing. NASA management level were also involved in unethical conduct. During the aftermath investigation, instead of telling take the responsibility and prevent future disaster, NASA’s managers t ried to hide the up facts and ran away from guilty.

The lack of a unified goal among the stakeholders also contributed to the happening of disaster. Through the disaster, every party focused on own benefit only. NASA paid most attention on the funding and schedule problems instead of potential risk. The managers in Thiokol concerned more about follow the contract and cut cost instead of quality of project. The engineers concerned about their working opportunities and yield under the pressure of management level. When facing the known issue, no party insisted to play the villain and stop the launch.