Weighing the risks of human spaceflight
One former astronaut’s perspective
There are few people better qualified to judge the risks of human spaceflight than Rick Hauck. The former astronaut flew on three shuttle missions in the 1980s, including serving as commander of STS-26, the first space shuttle mission after the Challenger accident. Since leaving the astronaut corps he became president and chief executive officer of AXA Space, a leading space insurance company, and also serves on the advisory committee for the X Prize.
Hauck addressed the issue of the risks of spaceflight in a talk at the Woodrow Wilson International Center for Scholars in Washington, DC, in late May. He started by laying out the raw statistics of human spaceflight: 18 of the 430 humans who have flown in space have died, 14 on two shuttle missions and four on two Soyuz flights. That works out to a fatality rate of just over four percent, a rate that holds roughly true if one considers only US or only Russian citizens, Hauck noted. (One can argue that this metric inflates the fatality rate, since it counts includes people who have flown multiple times; over 600 seats have been filled on the 113 shuttle flights to date, reducing the shuttle’s fatality rate to closer to two percent.)
Nevertheless, that number is uncomfortably high for Hauck. “Would I have flown if I had known there was a four percent chance of death?” he asked. “No, I don’t think I would have flown.”
However, he cautions, it’s unwise to assume that all manned space flights will have similar odds of death. “This is not an actuarial business, we don’t have thousands of events,” he said. “I do not believe that we can extrapolate from this experience that you have a four or five percent chance of dying if you go on a space mission.”
What Hauck didn’t point out, though, is that other ventures exist with similar fatality rates. In recent years about four percent of the people climbing Mt. Everest have died. Through the late 1970s that number was actually much higher, at about 30 percent; improvements in equipment and techniques have reduced the fatality rate even as the number of people attempting the climb has dramatically increased. For the mountain climbing community, a fatality rate of four percent had not deterred people from taking the risks.
Hauck, though, thinks the risk of death needs to be decreased for space flight, particularly future public space travel, to be widely accepted. Hauck said that the owner of an adventure travel company told him that his customers need to know that the odds of dying on a particular trip were less than one percent before enough of them would sign up for the business to be viable. “I think that’s about where I sit,” he said. “If I was told that I had a one percent chance of dying on the next space shuttle mission, I think I would take my chances.” Interestingly, that one-percent level of risk is about the same that the typical American has over his life of dying in an ordinary traffic accident.
Having determined an acceptable level of risk, Hauck then turned to another issue: who should make that determination? Even for government-run programs like the space shuttle, he believes, the public should have no say in deciding if space flight is too risky. “We all as taxpayers certainly have a vote on whether to spend the dollars on NASA programs,” he said. “However, I would take issue with the view of some people that they should have a vote on whether I should risk my own life. That is truly not an issue for the public to debate.”
The people who should ultimately decide if the risk of a space flight is acceptable are the crews themselves, he believes. “The crew will have to be convinced that all reasonable measures have been taken to minimize risk.”
The public, though, should have a somewhat larger role when weighing the risks to bystanders posed by human missions. This risk became clearer with the Columbia accident, as debris from the orbiter fell on eastern Texas and western Louisiana. No one was seriously injured or killed by the debris, but some have argued that if the shuttle broke up a little earlier, moving the debris field west towards the Dallas-Fort Worth area, or if the accident had taken place on a weekday morning rather than on a Saturday, more people could have been at risk.
Hauck acknowledged this risk exists and needs to be considered, particularly in the future as commercial manned spacecraft enter service. “A degree of care, study, and tailoring of orbits and reentry paths needs to be part of the flight profile decision process,” he said. “However, I’m not sure you can craft a reentry profile of a spacecraft that does not pose a threat to humans on the Earth.”
As Hauck notes, it’s impossible to completely eliminate the risk of human space travel, either to the crews themselves or people on the ground who could be in the launch or reentry flight paths of manned vehicles. In fact, as commercial manned spaceflight comes into being in the near future, the existence of that element of risk may prove to be a key selling point: without destinations to go to, many of the early passengers on suborbital spacecraft will be thrillseekers who willingly accept that chance of death to fly faster and higher that ever before. It will be these people who will provide the revenue that will allow companies to build new generations of more capable, and safer, spacecraft. For humanity to successfully journey into space, we must not only be able to mitigate and accept risk, but embrace it as well.