The International Space Station (ISS) and its astronaut crews routinely face a series of potentially disastrous risks in Earth orbit, an independent safety panel reported Tuesday. But available backup systems and procedures minimize the likelihood of the most catastrophic scenarios.
Impacts from space debris and micrometeorites topped a list of potentially serious risks that, if realized, could harm ISS astronauts, force an orbital evacuation, or destroy the half-built space station [image], according to a report released by the International Space Station Independent Safety Task Force.
A deliberate attack on the station's systems from Earth or accidental critical command by Mission Control is low on the list, the 119-page report stated.
"Although the Task Force made a number of recommendations, the ISS Program was aware of the problems that result in vulnerabilities and was developing improvements or had concepts to deal with most of the concerns," the safety panel concluded in its report, but added that some critical risks - such as that posed by space debris - required additional attention.
Congress ordered the independent review of potential hazards to the ISS and its expedition crews in 2005. It was released simultaneously to Congress, NASA and the public Tuesday.
The $100-billion orbital observatory is the result of an international agreement that includes NASA and 15 other countries. Currently crewed by three-astronaut teams, the ISS is expected to grow into a six-astronaut installation with as much habitable space five-bedroom home by 2010. Its exterior will rival a U.S. football field in length when complete [image].
"Most, if not all, of the things that are mentioned in the report have been on our radar for some time," Allard Beutel, a NASA spokesperson at the agency's Washington, D.C. headquarters, told SPACE.com. "The plan is to take some time and read this thing cover to cover and come up with a comprehensive plan addressing the recommendations of the report."
Space rock shielding a high priority
Micrometeorite and orbital debris (MMOD) impacts, fires, toxic spills and other time-sensitive emergencies are the biggest threat to the ISS astronauts and hardware.
The new report found that, when complete, the station has a 55 percent chance of being struck by tiny space rocks or trash over a 10-year period, with a 9 percent chance of a catastrophic strike.
Those chances could be reduced to 29 percent and 5 percent, respectively, by changing some Russian solar array orientations and installing new impact-protecting panels to the exterior of the station's Russian-built Zvezda service module - which launched to the outpost in June 2002 and December 2006 aboard NASA shuttles and are slated for installation during spacewalks set for April, the task force reported. Delivering an adequate number of pressure covers for the Zvevzda module's windows, in case they are struck by debris and must be sealed, would helped reduce MMOD risk to the ISS, it added.
Ensuring cargo and crew access to the ISS beyond the planned 2010 retirement of NASA shuttle fleet is also critical concern according to the task force's report. The safety panel recommended the U.S. space agency consider maintaining two non-ISS construction-dedicated orbiter missions - ostensibly to ferry spare parts and supplies to the orbital laboratory - in the agency's flight plan.
A close watch on station astronaut health is also required, since studies of submarine and Antarctica research crews found spontaneous illnesses severe enough to require medical attention could crop up every four to six years.
"In a worst-case scenario, a spontaneous health event may necessitate returning the crew to Earth for specialized medical attention, which would result in temporary abandonment of the ISS," the task force reported.
Despite its recommendation, the task force conceded that flying humans in space will always include safety concerns for flight crews.
"It must be recognized that regardless of the efforts put forth, operating in space is, and will be for the foreseeable future, inherently risky and requires continuing discipline and diligence to maintain safe operations," it reported.
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