A SpaceX Dragon supply ship packed with nearly three tons of experiments, crew provisions and supplies will remain on the ground until at least Friday morning to allow more time for NASA flight controllers to troubleshoot a problem with an electrical distribution unit on the International Space Station.
Multiple sources said the commercial resupply launch, previously scheduled for Wednesday, will be pushed back at least two days to no earlier than Friday at 3:11 a.m. EDT (0711 GMT).
The delay will allow time for NASA flight controllers at the Johnson Space Center in Houston to continue troubleshooting an issue with a distribution box in the space station’s electrical power system. Engineers detected an issue with the Main Bus Switching Unit on Monday morning, and ground teams may elect to replace the component later this week, ahead of the SpaceX cargo launch.
The unit is one of several that routes power from the space station’s U.S. solar arrays to the research outpost’s electrical channels. The suspect unit distributes power to two of the eight electrical channels on the station, including a power supply for the space station’s robotic arm, which the station astronauts will use to capture the Dragon cargo craft as it approaches the complex.
While the robotic arm remains powered through a separate channel, NASA flight rules require redundant power supplies for the arm during critical operations, such as the grapple of a free-flying spacecraft.
Ground teams have replaced a failed Main Bus Switching Unit using the station’s robotic arm before. The capability to robotically replace the power distribution box means astronauts may not have to conduct a spacewalk for the task.
The electrical system glitch does not pose any immediate concern to the station or its six-person crew, NASA said.
“Monday morning, teams identified an issue with the International Space Station’s electrical power system and are working to identify the root cause and restore full power to the system,” the space agency said in an updated posted on its website.
In the update posted Monday afternoon, officials said engineers were examining an unspecified issue with a Main Bus Switching Unit.
“Flight controllers have been working to route power through the remaining six power channels,” NASA said. “Electrical power generated by the station’s solar arrays is fed to all station systems through these power channels.”
NASA said Monday afternoon that managers were discussing how the power system problem might impact plans for the SpaceX resupply launch.
If the Dragon spacecraft had launched Wednesday, it was due to arrive at the station early Saturday. Assuming a launch from Cape Canaveral on Friday morning, the Dragon cargo freighter is scheduled to reach the complex early Sunday.
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