WASHINGTON — Space Exploration Technologies Corp.’s third contracted cargo run to the international space station is still set to launch at 4:58 eastern daylight time April 14, despite the failure of an external space station computer that will require replacement by spacewalking astronauts, a NASA official said April 13.

The so-called External-2 Multiplexer/Demultiplexer, a computer that controls station’s solar arrays, among other things, failed April 11. However, a backup unit has been activated, and even a failure of the secondary system does not pose an unacceptable threat to the SpaceX mission, Michael Suffredini, space station program manager at the Johnson Space Center in Houston, said during a press conference.

“We’re good to go” with the planned April 14 launch from Cape Canaveral Air Force Station, Fla., Suffredini said. Should the mission be delayed for some other reason, a backup launch date April 18 has been set.

NASA has a spare for the failed computer onboard the station. It will be installed during a spacewalk tentatively scheduled for April 22, six days after SpaceX’s Dragon cargo capsule is scheduled to berth with the station. NASA has not yet decided which astronauts will perform the spacewalk.

One of the two astronauts tapped for repair duties will don the same spacesuit that nearly drowned Italian astronaut Luca Parmitano back in July, when his helmet filled with fluid. NASA has since determined that a clogged filter was the cause, and the so-called Extravehicular Mobility Unit has undergone repairs to make it safe, Suffredini said.

SpaceX’s third contracted station cargo launch was delayed by problems with a tracking radar used for launches from the Cape, and the slippage may have implications for Orbital Sciences Corp., NASA’s other commercial cargo hauler.

Dulles, Va.-based Orbital is working toward a May 6 launch of its Antares rocket from Wallops Island, Va., but may not be able to launch until June 9 because of an brewing on-orbit traffic jam. SpaceX’s Dragon is required to remain at station for about a month following its scheduled April 16 arrival, and the Russian Federal Space Agency, Roscosmos, is scheduled to launch new crew members to the station May 28, Orbital said in an April 7 note on its own website.

SpaceX’s commercial manifest might also be affected by the delay. The Hawthorne, Calif.-based company is scheduled to launch half a dozen data-messaging satellites for Fort Lee, N.J.-based Orbcomm in late April.

Hans Koenigsmann, SpaceX’s vice president of mission assurance, said during the April 13 press briefing that the Orbcomm launch was still on for the end of April, but Orbcomm said in an April 11 note on its website that  “due to the recent delays with [SpaceX’s station cargo] mission, our new target launch window is May 10-15.”

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.