The causes of both of NASA’s shuttle disasters are complex — so complex that the agency took about two years to run flights again after fatal disasters in 1986 and 2003. Investigation boards pointed to a range of technical factors or failures in the shuttle systems. There also were human factors; examples included rushing launch dates, or managers deciding to “normalize deviance” (meaning, if a small failure happens often enough without an issue, mission managers accept that as the norm).
“[NASA] also said at one point that [the shuttle] was going to be as safe as an airline, which it never approached even close to,” Launius added. “Two airplane crashes out of 100 flights would be unacceptable in the aviation world.”
An infinite amount of money to spend on spacecraft development might help ensure human safety, but that’s not possible. So space agencies and their spacecraft manufacturers must make clever calculations: running statistics to see how often components will fail, testing as many individual components as possible, and implementing redundant systems, among many other measures.
NASA is working very closely with SpaceX to ensure that the contractor is doing everything possible to meet safety and reliability for astronauts in order to reliably transport astronauts to and from the International Space Station. Failure isn’t an option.
“It’s one thing to lose a payload that isn’t alive,” Launius remarked, “but it’s another thing to lose humans.”
While NASA and SpaceX have expressed hope that a human crew might fly in 2019, Launius suggested that the safety checks could likely push a crewed launch date back further.
“I could see this thing stretching out for a year or more,” he said.