Quantitative Risk Assessment: NASA

Quantitative Risk Assessment: NASA


Quantitative assessment of risk factors in complex space technology is very important in ensuring the safety of the astronauts to, at, and from space. NASA has faced several criticisms over its lack of quantitative risk assessment techniques in incidences such as the Challenger accident.

Committee’s Criticism

NASA has always used the Probabilistic Risk Assessment (PRA) tool to manage risks, cost, and efficiency of its complex equipment. The strategy helped it ensuring safety and efficiency particularly after the occurrence of challenger accident in 1986. Along with this tool, NASA has sought the help of quantitative risk assessment procedure that relies on the qualitative representation of risk (Mahler 2009). However, the Committee on Science and Technology criticized the application of these techniques was highly criticized when it reviewed the Challenger Accident.

Rodgers Committee

Rodgers commission charged NASA with a duty of reviewing its process and mechanism of ensuring the safety of NSTS (National Space Transportation System). The committee conducted an in-depth analysis of NASA’s procedures involved in conducting a qualitative risk assessment on space-craft elements and subsystems like the engine and auxiliary power unit. The probe was extensive. Software issues, integrated space transportation system, and orbiter structural margins were found to be weightily demanding a further investigation (Stamatelatos et al., 2011).

The committee appreciated the work done by NASA in designing, developing, verifying, and satisfying its operations using procedures that were successful so far. Nonetheless, they recommended a risk assessment criteria that NASA had to adopt as a way of enhancing the safety of its systems (Mahler 2009). The sanctions were quantitative and were to be integrated into the qualitative techniques applied by NASA hitherto as necessity demands. Further, the committee established the presence of documents outlining safety assessment strategies. It also noted that NASA emphasized procedures to “eliminate potential failure modes” using retention rationale, which was inconclusive (Stamatelatos et al., 2011).

The committee noted that the retention rationale adopted by NASA was biased and that it ignored some critical information which would determine whether the design was safe to adopt. Concerning critical items list, the committee established that it was slanted in its application by generalizing items under critically 1 and R1 to be of the same magnitude noting that they differed on the risk posed. It also emphasized that this practice was highly dangerous to a successful mission (Mahler 2009).

On hazard analysis and MSA (Mission Safety Assessment), the committee noted several flaws regarding its scope to deal with particular hazards. It also questioned NASA application of quantitative risk assessment in reaching most of its decisions which were found not to be the case (Johnson et al., 2011). NASA had failed to use quantitative risk analysis directly. Notably, NASA was not sufficiently staffed with statistical analysts who would handle complex information and converting them to simpler forms that could be applied in the decision-making process (Stamatelatos et al., 2011). The need for quantitative techniques in risk assessment was emphasized in subsequent programs such as the Apollo.


Considering Rodgers committee’s report on Challenger Accident, NASA did not meet the threshold of quantitative risk assessment criteria. Instead, it relied on series of board meetings that created a perception of group responsibility in decision making and risk assessment criteria. The failure to apply integrated quantitative risk analysis criteria would predispose another mission to the same dangers that befell the Challenger mission.


Johnson, S. B. et al., (2011). System Health Management: with Aerospace Applications. New York, NY: John Wiley & Sons.

Mahler, J.G. (2009). Organizational Learning at NASA: The Challenger and Columbia Accidents. New York, NY: Georgetown University Press.

Stamatelatos, M., et al., (2011). Probabilistic risk assessment procedures guide for NASA managers and practitioners. https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120001369.pdf