Building and Using Models

“Building and Using Models” Please respond to the following:

Last week we introduced the idea of data, data collection, stratification of data and then data analysis tools. This week we introduce the concept of building models with our data in an effort to predict some future outcome. I have attached a BBC documentary on the space shuttle challenger disaster to inject  the story of a struggle between engineers and their data with operators and administrators that are forced to make hard decisions in a world where there is more unknown than known. After watching this video review the attached Power Point presentation. I would like you to expound on a replacement discussion question this week.

The BBC documentary makes a compelling case that NASA management should have listened to the engineers, thus avoiding the Challenger mishap. However, the video does not present the evidence in the same fashion that the historical record shows. Slides 2-5 depict the data Morton Thiokol showed NASA leadership. Data was presented as raw numbers in tables, not as figures on a chart. Slides 6 and 7 show a different perspective of that data first by using a relational table then drawing a scatter plot. Had this information been presented, could you now come up with a better forecast relating O ring damage and temperature?

Roger Boisjoly, engineer at Morton Thiokol Inc. couldn’t have said this better. He said that he never considered this an accident and never will, since it was predetermined what will happen and the management would not listen.

After listening to the BBC documentary on the Challenger mishap and reviewing the slides, I think NASA management didn’t give importance to the engineers from Morton Thiokol and went ahead with the launch. Larry Mulloy, in his
deposition during the special session of Presidential Inquiry for solid rocket motor, said that given the data from Morton Thiokol, he had he okayed the launch. Allan MacDonald, Director of solid rocket booster project at Morton Thiokol, in the same committee hearing mentioned that the recommendations from the engineers were to scrub the launch because the the ambient temperature during the fatal launch day was 29 degrees, which was 25 degress lower that the last recorded flight from the previous STA 51C mission.

Roger Boisjoly & Arnie Thompson who were leading experts on the design of the booster case seal had found that that the walls of the SRB would flex outward, opening a gap between the O-ring and outerwall. To maintain the seal the primary and the secondary O-ring have to expand in just 50 milliseconds to seal the gap to prevent hot gases from escaping, which if happens will erode the O-rings and lead to catastrophic failure. They found that when the temperatures were very low, the rings would harden, thereby taking longer to seal and hence reduce blowby. They mentioned that it is a race between the O-ring eroding because of blow by and its ability to seal enough and that 24 times before they have won against time. Roger had personally examined the seal on the rocket engine which had been previously launched at an ambient temperature of 53 degrees, and had seen disastrous results. Trying to launch a shuttle at 29 degrees ambient temperature was completely unacceptable. NASA apparently knew about this problem and acknowledged this as acceptable risk, which they should never have because if the primary O-ring failed, the whole assembly would fail as a result.

Apparently the shuttle program was required to fly 24 missions a year and the shuttle launch prior to this launch STA 51C was scrubbed 7 times and Challenger mission was scrubbed 4 times already. All the data pertaining to O-ring  failure was available to the management to make an informed decision. I feel, the input from the engineers were completely ignored, as Jerald Mason took over the meeting with NASA and forced the upper management at Morton Thiocol to give NASA unanimous decision to go ahead with the launch, since the contract for building SRM had come up for renewal a week before launch. Larry Mulloy from NASA also was not in favor of scrubbing the launch, because he felt that the data provided by Roger & Arnie didnt show that the component will fail at temperatures below 53 degrees.

I feel that if the data was provided to the NASA management in a proper chart format, it would have been easy for NASA to see the correlation between O-ring failure and temperature in previous missions, instead of just dismissing them as acceptable risk.