Two U.S. astronauts will venture outside the International Space Station on Jan. 30 on what will be a first step toward restoring full power-generation capability at the orbiting outpost.
NASA set the date after flight controllers and the astronauts -- station commander Peggy Whitson and Dan Tani -- worked out the steps the spacewalkers will take to remove and replace a faulty solar array drive motor.
Whitson and Tani are tentatively set to exit the U.S. Quest airlock at 4:30 a.m. EST that day. They'll crawl hand-over-hand to a solar wing at the starboard end of the station's central truss. Once there, the astronauts will use pistol-grip power tools to unbolt the broken motor drive and the replace it with a spare.
The station now is powered by three massive American solar wings -- two on the portside end of the outpost's central truss, and one on the starboard end. A fourth and final solar wing is to be added to the starboard end of the truss during an assembly mission scheduled for launch later this year.
Ten-foot-diameter rotary joints on either end of the truss are designed to turn like a Ferris wheel, enabling the wings to constantly track the sun, maximizing solar energy collection and electrical power production. Engineers noted high voltage readings and vibration on the starboard joint and shut it down late last year, limiting the amount of electricity it can generate.
Separate motor drives on either end of the truss are used to tilt the wings so they remain face-on to the sun as the station circles 220 miles above Earth.
Whitson and Tani will replace one of the motor drives on the starboard end of the central truss. A separate series of spacewalks will have to be performed to fix the malfunctioning starboard rotary joint. That repair work is critical to station assembly plans this year. Engineering analyses show the station likely won't be able to generate enough power to support a Japanese science laboratory now scheduled for launch in late April.
NASA astronauts Thomas Marshburn (above) and Sunita "Suni" Williams (below) are suited up and working in 6.2 million-gallon swimming pool near Johnson Space Center today, refining the procedures Whitson and Tani will follow during the repair work.
The Jan. 30 outing will be the sixth for Whitson, who already holds the world record for most spacewalking accumulated by a woman: 32 hours and 36 minutes during five previous excursions. The first female commander of the station, Whitson said she is excited about the upcoming repair job.
"I feel very honored to have the privileged again to be able to walk in space," Whitson said in a space-to-ground interview. "We're really looking forward to it."
The spacewalking work will afford Whitson and Tani unmatched panoramic views of the Earth as well as the 250-ton station, which is about 60 percent complete. Whitson said she has trouble putting the experience into words.
"The analogy I typically use is that it's like living your whole life in a room that is somewhat dark, and then suddenly turning the lights on. That's what it's like to look out the window here at the space station. The colors are so much richer and clearer," Whitson said.
"The clarity is unbelievable, and when you go outside the it's like the difference between being in a darkened room and going outside in a sunlit street. So for us up here, it's quite exhilarating to get to see not only our Earth but the huge structure that we've built, which is just amazing as well."
Whitson and Russian cosmonaut Yuri Malenchenko flew up to the station in mid-October, and Tani joined them when shuttle Discovery arrived for an assembly mission later that month.
Tani is scheduled to return to Earth aboard shuttle Atlantis in February, and Whitson will fly back aboard a Russian Soyuz spacecraft in mid-April.
No comments:
Post a Comment