May 24, 2019

SpaceX resupply launch delayed by malfunction on space station


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EDITOR’S NOTE: Updated at 12 p.m. EDT (1600 GMT) with NASA’s confirmation of the delay.

A portion of a solar array wing on the International Space Station is visible in this image. Credit: NASA

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 Monday that the commercial resupply launch from Cape Canaveral, 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).

NASA confirmed the launch delay Tuesday.

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 plan to replace the component later this week, ahead of the SpaceX cargo launch.

“Teams are working on a plan to robotically replace the failed unit and restore full power to the station system,” NASA said in a statement Tuesday. “The earliest possible launch opportunity is no earlier than Friday, May 3.”

The Main Bus Distribution 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 will 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.

NASA’s Orbiting Carbon Observatory-3 (OCO-3) and the U.S. military’s Space Test Program-Houston 6 (STP-H6) payloads are in view installed in the trunk of SpaceX’s Dragon spacecraft inside the SpaceX facility at NASA’s Kennedy Space Center in Florida on March 23, 2019. Credit: NASA

“Flight controllers have been working to route power through the remaining six power channels,” NASA said in a previous statement released Monday. “Electrical power generated by the station’s solar arrays is fed to all station systems through these power channels.”

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.

Forecasters with the U.S. Air Force’s 45th Weather Squadron predict a 60 percent chance of favorable conditions for Friday’s predawn launch opportunity, which is timed for when the space station’s orbital plane passes over Cape Canaveral.

An outlook issued Tuesday identified concerns that weather at Cape Canaveral could violate weather rules relating to cumulus clouds, thick clouds and flight through precipitation.

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Follow Stephen Clark on Twitter: @StephenClark1.


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