Article Posted on : - Apr 15, 2010

A portion of the aft section of the docked space shuttle Discovery. A NASA photo

NEW DELHI (BNS): International Space Station mission managers have said there is no need for a fourth spacewalk to replace the nitrogen tank assembly that has a jammed valve.

Flight controllers on Wednesday tried to open the nitrogen valve twice by remote control, but were unsuccessful. It failed to open on Wednesday after the astronauts finished installing a new ammonia tank. Nitrogen is needed to pressurise the ammonia coolant.

Ground teams were concerned that a high beta angle would cause the ammonia in the new tank assembly to expand and exceed the capacity of the radiators without the nitrogen to keep the system circulating, a NASA statement said.

The beta angle – the angle between the sun and the plane of the orbit – was increasing, creating higher temperatures, it said.

Station ground teams have determined the station can operate for an extended period of time in the current configuration. The team is, however, continuing to troubleshoot the stuck valve and is looking at options for future replacement of the nitrogen tank assembly.