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.
The threat
of collisions with visiting
spacecraft or an ISS
robotic arm, onboard
fires, and toxic spills
follow closely after.
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.
Changes
underway
"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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