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- NASA is to waive its safety requirements for the International Space
Station (ISS) in a bid to get it in orbit earlier.
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- The Russian-built service module, which
serves as the first crew's living compartment, has failed Nasa's tests
for surviving collisions with orbiting space junk. In a bid to keep the
station on schedule Nasa has waived the requirements and is now planning
to send collision shields to the module once it is in orbit.
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- However, according to Allen Li, an associate
director with the US General Accounting Office who last week reviewed Nasa's
budget with the Senate, the shields will not be ready for three years,
meaning the first crew members will have to sleep in an unprotected module.
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- "The current plan is for Nasa to
issue a waiver at the time of launch, and then correct the problem when
the module is in orbit," Li told a Senate panel that oversees Nasa's
activities.
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- Li also revealed that although Russia
is working with Nasa to get the shielding in place, Nasa could end up footing
the bill. "This is another area where we may have to pick up the slack
for Russia, not just in terms of paying for the hardware, but also the
EVAs [space walks] we would have to schedule to install them."
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- When Russia began its involvement in
the station, all the ISS partners decided there was only a 19% chance of
the station being hit by debris, and planned protection accordingly. However,
as more modules were added, this rose to a 24% chance. Once the Russian
Service Module is added to the ISS, there will not be enough shielding
on the station to protect it.
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- According to Nasa's tests, if the service
module were struck and depressurised, it would fail to work. It would have
to be evacuated immediately
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- The shielding planned for the modules
would help slow down debris, which could hit the station at about 75,000mph.
Rather than stopping the debris dead, it will be vapourised as it passes
through the shield, causing little or no damage when it finally hits the
station. The shields will be mounted on arms attached to the outside of
the module during a series of space walks. Shields are also likely to be
added to the Zarya module already orbiting earth, as it also fails to meet
Nasa's space-debris requirements.
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- As well as building extra shields for
the module, Nasa and Russia are also beginning to plan for possible repairs
should the module ever be damaged.
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- According to Li, Nasa is to go ahead
with the launch of the module despite the safety lapses. "Nasa believes
the module adds capabilities to the station that would otherwise be unavailable,
and thinks it is a worthwhile risk to go ahead as planned," says Li.
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- According to Jim Oberg, a consultant
who has advised the Senate on space-station issues, the move is simply
Russia's way of cutting corners to get the service module in orbit.
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- He says: "Russia has been running
its Mir space station for a long time with no space-debris problems. However,
Mir orbits the earth at a lower altitude than the ISS. Where the ISS is,
the space debris is much thicker and poses more of a risk. The ISS will
also be in orbit for longer than Mir, and Nasa is most worried about the
long-term effects."
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- Oberg believes Russia is cutting corners
to save money. "This is really just another way for Russia to save
time and money. They have also failed to upgrade the oxygen system that
caught fire on Mir and will form part of the ISS - something Nasa is not
happy about," says Oberg.
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- According to Dan Goldin, head of Nasa,
the space agency is doing all it can to get added protection for the service
module in place sooner, but he says American laws are conservative in the
area of space debris, so the risks for ISS crew will not be great.
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- Joe Rothenberg, Nasa's associate administrator
for space flight, says that without the additional shielding, the service
module has the same level of protection as Mir, which has been in orbit
since 1986 without any space-debris accidents.
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- "Russia has far greater experience
than us, and they have assured us there is no problem," says Rothenberg.
However, Nasa claims Russia is keen to install the shielding to adhere
to Nasa's rules.
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- It has also been revealed that it is
not just Russia that is facing financial problems - Boeing, the prime American
contractor for the station is $986m over budget. The company claims the
cost is due mainly to expensive software development for the ISS's controlling
computers.
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