NASA and Orbital Sciences Corp. Saturday moved the targeted launch date of the Orbital-1 resupply mission to the International Space Station to no earlier than Thursday, Dec. 19 to enable engineers to continue their analysis of data involving a suspect Flow Control Valve in a pump module on the starboard truss of the station that malfunctioned on Wednesday. Orbital’s Antares rocket and the Cygnus commercial cargo vehicle are now scheduled to launch from Pad 0A at the Wallops Flight Facility, Va. no earlier than Dec. 19 at 9:19 p.m. EST. NASA TV coverage of launch will begin at 9 p.m.
The delay will allow Orbital’s engineering team to load late scientific cargo into the Cygnus craft on Sunday to protect several days of launch opportunities through the end of next week. Under current planning, the Antares rocket with Cygnus would rollout to the launch pad at Wallops in the early morning hours on Tuesday, Dec. 17. A launch on Dec. 19 would result in Cygnus arriving at the space station for a grapple and berthing to the Earth-facing port of the Harmony module on Sunday, Dec. 22.
The launch is still dependent on NASA engineers resolving a problem with the station’s pump module flow control valve that experienced a problem Wednesday in properly positioning itself so that ammonia coolant can flow properly through the cooling lines of the station’s truss while keeping heat-rejecting equipment at the correct temperature.
Overnight, engineers conducted testing with a component in the Pump Module called a Radiator Return Valve, which is a ball valve that operates in concert with the suspect Flow Control Valve in the pump to control heating in the cooling lines to the Interface Heat Exchangers. The Radiator Return Valve was commanded to various positions to see how the Flow Control Valve might be placed in a fixed position to help actively control cooling loop A, and in turn, allow the system to warm up sufficiently so that the heat exchangers in the loop can operate at a proper temperature. Engineers continue to pore over the data and other techniques to manage the flow control valve. The cooling of station systems is currently being managed through cooling loop B that employs a pump module on the port truss.
In the meantime, Expedition 38 crewmembers Rick Mastracchio and Michael Hopkins worked Saturday in the Quest airlock to begin preparing their spacesuits in the event they are called upon to conduct spacewalks to change out the faulty pump module. If managers direct the crewmembers to perform those spacewalks beginning late next week, the launch of the Orbital-1 mission would be delayed until January.