AP Aerospace Writer
CAPE CANAVERAL, Fla. (AP) -- A space station cargo ship will remain Earthbound for a while longer because of a rocket leak.
With just over an hour remaining, the SpaceX company called off Monday's planned launch. Officials said they believe the problem can be fixed by Friday, the next opportunity for flying and the last chance before astronauts do urgent spacewalking repairs.
A helium leak in the first-stage of the unmanned Falcon rocket forced a halt to the countdown, the latest delay spanning the past month.
Over the weekend, NASA almost postponed the launch attempt because of a computer outage at the International Space Station. But mission managers decided Sunday that everything would be safe for the arrival of the Dragon capsule and its 2½ tons of supplies.
The computer, a critical backup, failed outside the space station Friday as flight controllers were trying to activate it for a routine software load. The primary computer has been working fine.
It's the first breakdown ever of one of these so-called space station MDMs, or multiplexer-demultiplexers, used to route computer commands for a wide variety of systems. Forty-five MDMs are scattered around the orbiting lab. The failed one is located outside and therefore will require spacewalking repairs.
The Dragon capsule holds a gasket-like material for next week's computer replacement. This new material was rushed to the launch site over the weekend and loaded into the Dragon. NASA said astronauts can make the repair without it if necessary.
NASA astronauts Rick Mastracchio and Steven Swanson will perform the spacewalk next Tuesday -- regardless of whether the Dragon flies by then. It will take several days to get the replacement computer ready, thus the one-week wait before the job, NASA's Kenny Todd, a station operations manager, said Monday.
SpaceX -- Space Exploration Technologies Corp. of California -- is one of two American companies hired by NASA to fill the cargo gap left when the space shuttles retired in 2011. Orbital Sciences Corp. of Virginia is the other.
If the SpaceX Dragon isn't flying by Friday, the company may have to get in line behind Orbital, on track for a May delivery run from its Virginia launching site.
The Dragon should have soared in mid-March, but SpaceX needed two extra weeks of launch prepping. Then an Air Force radar-tracking device was damaged in a fluke accident; an electrical short caused the instrument to overheat.
Monday's helium leak apparently came from a system that separates the first-stage during the first few minutes of flight.
Earlier in the afternoon, SpaceX signed a 20-year lease with NASA to take over the launch pad used during the Apollo and shuttle programs. Kennedy Space Center's Launch Complex 39-A would be used for SpaceX launches with astronauts bound for the space station in three or four more years, if NASA approves the venture. Russia currently provides the only way to get astronauts to and from the space station.
Unmanned missions also are slated for this pad, possibly next year.
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