On January 28, 1986, at 5:39 p.m., 73 seconds after takeoff within NASA’s STS-51-L mission and at a height of 14.6 kilometers, the space shuttle Challenger disintegrated in mid- air and its seven crewmembers, among the cream of the crop scientists in the country, died, giving rise to one of the saddest representative images of the last century.

The ultimate cause of the space shuttle disintegration was the partial separation of the right solid propellant, produced by an ignition gas leak that burned its lower support, weakening it until it broke, leaving the propellant somewhat loose. This caused the Challenger to start to fly sideways, exposing it to forces of approximately 20g (or 20 times the universal earth gravity), far greater than the 5g it was designed for, causing its destruction.

As early as 1977 (nine years before the fatal accident), it was known that the O-rings that seal the union between the different sections of the solid propellant chambers that make up the thrusters were very sensitive to temperature. They become rigid and brittle with cold surroundings, and Challenger’s launch on February 28 was about 12 degrees cooler than any previous launch. It was known too that if one of these joints failed, there was no backup mechanism that could contain the gas leak.

Still, those responsible for NASA’s Marshall Center, the shuttle’s propulsion systems developer, decided that this was an acceptable risk without discussing it with anyone other than the propellant manufacturer. Indeed, it was against the agency’s rules to discuss these types of decisions with anyone outside a closed circle of professionals intimate with the process.

In fact, none of the shuttle program managers who might have stopped the launch of space shuttle Challenger until fixing these problems related to what-if scenarios, was aware of the sealing design. Moreover, none of the engineers showed concern on launch day about the issue of low temperature and its possible effects on the joints in question to warn the right people.

Today, in addition to ordering the immediate redesign of the solid-fuel boosters, the report of the Rogers Commission in charge of studying the Challenger disaster harshly criticized the shortcomings in terms of safety management and estimation of risks. Dr. Richard Feynman, one of its members, was quoted saying: “to have a successful technology, reality must prevail over public relations, since nature cannot be fooled.”

Significant changes in the roles of simulation and physical testing have been occurring in many industries as they become further integrated into the product development cycle. Involving mechanical simulation (CAE or computer-aided engineering) with CAD (computer- aided design) has helped create FEA (Finite Element Analysis) simulators now expanding to nonlinear materials like flexible polymers. Still, a major challenge remains in getting departments not involved in simulation to accept predictions as the basis for engineering decisions. This is where correlating FEA to physical testing can help build simulation credibility.

Even at firms performing FEA, physical testing has traditionally been used downstream in the product development process as a pass-or-fail filter before a product is released to manufacturing. With upstream migration into product development to assist in validating designs and processing, the role of testing has evolved to one of helping develop materials, engineer products, and establish manufacturing processes. While tests have not changed in type (i.e., strain, temperature, pressure, etc.), how results are collected and used, and by whom, are becoming different.