- After yet another computer crash on the International
Space Station on Tuesday, a NASA spokesman has told New Scientist that
the station's spinning hard drives may be replaced with units with no
moving
parts.
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- These could work better in orbit, as the lack of gravity
is much less likely to affect solid state components than moving
ones.
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- The station's central command computers have suffered
many glitches since the station opened. All three crashed during the last
shuttle mission in April 2001, causing the station's communication system
with Earth to go down.
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- One of the computers crashed again on Tuesday, crippling
the station's robotic arm and delaying the installation of several air
tanks to the outside of the station.
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- NASA spent several hours debating whether to abandon
the large arm in favour of using a smaller robotic arm on the shuttle.
But a full reboot of the computer seemed to solve the problem and the
operation went ahead as planned.
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- Bad Vibrations
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- Kelly Humphries, at NASA's Johnson Space Center in
Houston
says they are not sure if it was a hardware or software problem that caused
the computer to "hang up". Some computer trouble is to be
expected
he says: "computers will be computers." But NASA is trying to
make the system more stable.
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- Moving parts in the computers' hard drives, which spin
just like those in desk-top computers, are thought to be causing some of
the problems. Vibrations from docking shuttles could cause these kinds
of drives to crash, and the parts are not specifically designed to work
in a zero gravity environment.
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- Humphries says: "We have plans to move to a solid
state hard drive towards the end of this year." These have no moving
parts.
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- But Chris Tofts from Hewlett-Packard labs in Bristol,
UK says that solid state hard drives could have their own problems in
space.
The usual cause of crashes in these drives is radiation, he says, and the
station is bombarded by cosmic rays. Shielding is in place but is unlikely
to block all the rays.
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- "Radiation can flip the quantum states of the stuff
that's storing the data," he says. "Effectively you're passing
charge through stuff that's charge sensitive. They're not liable to like
it very much."
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- While replacing the central command computers might sound
like a sensitive operation, Humphries says it should not be too difficult.
Two of the computers were replaced after the April crash without problems.
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- Hump
hries adds that the station can "run on an even
keel" for weeks at a time even with all three control computers
off-line.
Vital systems like lights, temperature control and air circulation can
be run manually by NASA staff on Earth if necessary.
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- Leaking Ship
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- The space station also suffered from leaking pipes during
the installation of its new airlock this weekend, though this is not
causing
serious problems.
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- As astronauts connected the plumbing that would deliver
cooling water to the new airlock, about two cups of water spilled out.
That was much bigger than the small leak they expected, but the system
is now working.
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- A pipe circulating air between the station and the
airlock
was also discovered to have a small leak after being switched on for the
first time. The leak does not pose a safety hazard, but will make it
difficult
to pressurise and depressurise that part of the station accurately.
Astronauts
were unable to fix the leak, so they have capped it until a replacement
part can be delivered.
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- More annoying is the noise made by an air pump in the
new lock. Astronauts have complained that this is so loud it has driven
them out of the module next door.
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- The various problems have delayed the mission by a day.
The shuttle is now scheduled to return on Saturday night.
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- http://www.newscientist.com/news/news.jsp?id=ns99991042
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