The most recent mission of the space shuttle Endeavour has drawn attention once again to the fundamental deficiencies of the shuttle program. Although the damage to Endeavor’s tiles was not a threat to the safety of the crew, it served as a reminder of the problematic basic design of having the orbiter mounted alongside its solid rocket boosters and external fuel tank. Whether the debris striking Endeavour shortly after launch was foam or ice, it clearly came from the mounting bracket, and would not have struck the shuttle had it been possible to mount it atop the boosters and tank, as was the case in the Mercury and Apollo programs. The last shuttle missions will fly in 2010, and hopefully the successor vehicle will correct this basic design flaw, returning to the more successful earlier model, rather than banking on the supposed reusability of the orbiter.
In truth, the space shuttle as it exists is not properly reusable, as many of its parts need to be replaced or rebuilt after each mission, and there are extensive safety inspections needed to find fractures or other failures. NASA’s model of tolerating stress failures of individual parts, so long as they do not fracture sufficiently to cause the loss of a vehicle, and replacing them after each mission, was exposed by Richard Feynman in the wake of the Challenger disaster. At the time, there was an alarming propensity among NASA administrators to overstate the safety factor and grossly underestimate the probability of failure, which we now know from experience to be at least 1 in 100, consistent with the prediction of engineers in the 1980s. A culture of secrecy and concern for public relations prevented realistic assessments of risk, and prevented certain facts about the Challenger disaster from reaching the public. NASA prevented state authorities from performing autopsies on the astronauts, and downplayed evidence that the astronauts likely were alive and conscious during their free fall before impacting the ocean’s surface.
Among Feynman’s findings regarding NASA’s attitude toward safety was the irrational practice of regarding a situation (such as certain structural damage) as safe if missions have been successfully flown in that condition, regardless of any probabilistic assessment of failure. This posture resulted in the Columbia disaster, as NASA engineers mistook the success of previous missions as an indication that there was no intrinsic danger to the model of having the shuttle alongside its rocket boosters. Worse still, although the impact of foam against the shuttle tiles was recognized during the mission, the shuttle was authorized for re-entry, denying the possibility that there was a threat to the vehicle.
Now that the dangers of the space shuttle are more fully and publicly understood, it is increasingly cumbersome and expensive to assure mission safety. The space shuttle is also burdened with antiquated electronics and computer technology, so that its reusability has become a liability. A new manned space vehicle needs to be developed, more along the lines of the earlier successful American programs, and the currently successful Russian model.
The development of a new space vehicle, as part of NASA’s new objective of returning to the moon and landing astronauts on Mars, will undoubtedly limit its ability to fund other endeavors. Already, basic scientific research unrelated to manned spaceflight has seen reduced funding by NASA, even though important questions in astrophysics and particle physics can be explored with unmanned vehicles that are much more cost effective. Manned space flight increases the cost of research well over a hundredfold, and it provides no data that unmanned probes cannot provide, save for the effects of space flight on humans. Such a circular justification should not be the basis for an enormous investment. Even if scientific research on humans in space is necessary, this can be achieved on the International Space Station, which is also in danger of losing NASA funding. Considering that NASA advocated destroying Mir in favor of a new station that would not be in exclusively foreign control, it is understandable that European partners strenuously object to its plans to scuttle the ISS as soon as 2016, only six years after completion. The enormous cost and complexity of the ISS make comparisons to the space shuttle program inevitable, and given NASA’s recent track record, it is unclear whether they are institutionally capable of leaner, more efficient design for the moon and Mars programs.