International Space Station engineers are closing in on a repair for their torn solar array blanket, but they may have to wait until Saturday to try it.

The idea is to send astronaut Scott Parazynski up to the rip, about 90 feet from the foot of the array, on the boom normally used to inspect the tiles on the belly of  the space shuttle. There he will string  as many as  seven jury-rigged "cufflinks" between reinforced  holes in the array blankets that originally guided pins that held the blanket rigid during launch in November 2000. The wire straps will bypass the tear and take the load that will result when the array is extended to its full extent.

If it works, station assembly will be able  to continue as planned, although probably with some delay. If it doesn't, the whole schedule will have to be reworked, and the half-array affected by the damage may have to be jettisoned, according to Mike Suffredini, NASA's ISS program manager.
 
Managers have already pushed back the next extravehicular activity (EVA) from Thursday to Friday (see previous post), and if that isn't enough time  to get ready for the complicated EVA the plan is to wait until Saturday. A Saturday EVA would require the addition of another day to the 15-day mission, which already has been increased by one day.

Shuttle engineers are still studying  what  it would  take to do that. But not matter what happens, the planned fifth EVA of the STS-120/10A mission - to begin the work necessary to put the Harmony node in its final position - won't occur until after the shuttle  Discovery undocks next Monday.

Since the tear appeared as the P6 array-half was being redeployed after its move from its temporary position on top of  the station, engineers have worked around the clock to find a way to fix it, Suffredini said. If  it can't be fixed, structural limitations  from its partially deployed  state make it questionable whether the station can produce the power and handle the dockings  and  undockings needed to continue assembly.

Many questions remain about  the get-well plan too, including whether the sophisticated sensors at the end of the Orbiter Boom Sensor  System (OBSS) will be able to survive through one and perhaps two spacewalks. Engineers believe  they can.

But if they are  damaged by thermal extremes, they won't be available for  the normal post-undocking inspection to ensure  Discovery's thermal protection system is safe for reentry. A set of accelerometers installed after the Columbia to monitor impacts to the wing  leading edges from orbital debris or micrometeoroids has registered seven "indications" that something may have hit.

Those alarms have proved  false  in the past, but  shuttle engineers are  unwilling to take the risk and are looking at alternative inspection techniques in case  the OBSS is damaged during  the array repair, according to  Derek Hassmann, lead  ISS flight director for the current mission.