By Douglas Messier
Following the loss of a Cygnus freighter when its Antares booster exploded after launch on Oct. 28, NASA officials emphasized the International Space Station (ISS) crew was in good shape on supplies, which could last into March without any other ships visiting the facility. As if on queue, a Russian Progress freighter blasted off for the station the following morning, which officials said demonstrated the wisdom of redundant supply systems.
All that was true enough. Behind the scenes, however, officials were concerned over one critical item aboard station: water. The suspension of Cygnus flights for at least a year threw a monkey wrench into NASA’s plan to use the cargo ship to resupply the station with H2O. It also left station astronauts dependent upon the success of a Japanese HTV freight set for launch only weeks before they would ran out of water on Sept. 2.
The details of how NASA and its international partners have been dealing with this serious situation are included in the 2014 Annual Report of the Aerospace Safety Advisory Panel (ASAP), an independent watchdog group that reviews the space agency’s safety practices.
NASA had planned to certify Cygnus to carry water to the space station in early 2015; there were no plans for certifying SpaceX’s Dragon cargo ship to do the same. Orbital plans to launch its next Cygnus aboard a United Launch Alliance Atlas V rocket, but that flight is not scheduled until Nov. 19.
Meanwhile, ESA has ended flights of its ATV cargo ship, which was certified to carry water. With the ATV program over and Cygnus off-line, the space station was left with two vehicles capable of carrying water, the Russian Progress and Japanese HTV.
HTV flights are now limited to once per year; the next one is planned for August 17, just over two weeks before ISS would run out of water on Sept. 2 unless it was resupplied by other vehicles. The schedule provided very little margin for error, ASAP said.
“The ISS program responded quickly by initiating discussions with SpaceX to have them certify their vehicle for water (targeting SpaceX CRS-6 in April/May 2015), initiating negotiations with the Russians to potentially fly water on one of their Progress vehicles, and making all efforts to return the Sabatier system on the ISS to operational status for water production,” the report stated.
“This response is viewed by the Panel as appropriate, and there is confidence that adequate water supplies will be maintained on the ISS,” ASAP added.