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STS-97 (ISS 4A - P6 Truss)
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ISS NewsWith the ISS modules on orbit (Zarya, Unity, Zvezda) forming a construction shack with basic albeit limited life support systems, and the first crew onboard setting up systems for long term habitation and work, the STS-97 mission continues the work began with STS-96 in assembling the US segment of the ISS, adding the P6 Truss to its temporary working position on top of the Z1 truss mounted to Unity.
With many of the major systems of the Zvezda (Service) module and Zarya (FGB) module activated, the complex has been on a tight electrical power budget. The ISS-1 crew has not been allowed to enter of use the Unity (Node-1) module at all during the first month of their flight due to the inability to properly heat the module to prevent condensate from harming its internal systems. That all changes with the successful addition of the P6 truss (see description) and solar arrays of unpresidented size during the STS-97 mission crewed by Brent Jett, Michael Bloomfield, Joseph Tanner, Marc Garneau, Carlos Noriega.
Major Mission Goals:
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After docking the the station at the new docking port added by the STS-96 mission, the shuttle crew opened the hatch transfered some items into the docking adapter PMA-3. They then closed the hatch again, and the station crew would make their first entry into Unity for a breif hour to retreive the items including a new laptop. The reason for this exchange is the shuttle is pressurized to a lower level than usual to allow for shorted oxygen pre-breathing time before their EVA's to attach the P6 truss. Once the EVA's are over, the shuttle will be pressurized to normal levels allowing for opening the hatches to the station for more transfers and crew interactions.
Shortly after docking, the shuttle RMS arm was used to lift the P6 Truss out of the payload bay, rotating it at an angle at first to avoid hitting the forward end on the PMA-2 docking adapter which stuck out over the payload bay. The Truss was left hanging high over the payload bay to allow for it to be evenly heated and cooled as it flew around the Earth, like it was designed for when attached to the station. Without doing this the Truss could have gotten too cold or hot in places and exceeded its design limits risking damaging some sensitive equipment.
The next day as astronauts watched at the docking point, the P6 truss was placed next to the Z1 truss with the shuttle RMS. A docking hook then was screwed down by the astronauts soft docking the P6 in place. Then pre-installed several bolts were driven into the trusses by the astrouants. A few minor problems slowed work on deploying the arrays but the first solar array was then delpoyed. During this, one of the pair of arrays developed a small problem when its tensioning wires came off tensioning pullies as the array elements popped open in a jurky fashion sending gentle shock waves rippling down the array and unraveling the wires off the pullies.
The second array was delpoyed and the solar array thermal radiators. Another EVA was done to install wiring to route power from the P6 to the rest of the station and place the tensioning wires back on their pullies in the first array deployed. Several other minor tasks were performed during the EVA's successfully completing this stage of the ISS assembly.
Next in the construction is the all important US Laboratory module Destiny with its computers and control systems which will make full use of the P6 and Z1's capabilities.
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The view from the end of the P6 truss looking back at the Shuttle and Zarya (FGB) module. Two astronauts placed a electrical measuring device (Floating Potential Probe) on the end of the truss to help characterize the charging around the newly installed solar arrays. |
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EVA crewman work on the Unity module( Node-1) while taking a moment to enjoy the view of the Earth and Moon over South America. |
Images from NASA
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