SpaceX announced it will try to launch the first commercial flight to the International Space Station at 3:22 a.m. Tuesday morning following the replacement of a valve that led to an abort just a half second before the Falcon 9 rocket was to lift off a Cape Canaveral launch pad Saturday.

The rocket’s computers shut down its nine engines after sensors on the rocket’s fifth engine indicated pressure readings that fell outside safe operating levels. SpaceX technicians identified the problem as a faulty check valve and replaced it by Saturday evening.

SpaceX President Gwyne Shotwell said at a Saturday press conference that the abort was not a setback for the company.

“This not a failure. We aborted with purpose, it would be a failure if we were to have lifted off with an engine trending in this direction.” Shotwell said.

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NASA’s own Space Shuttle experienced a number of similar aborts after engine ignition throughout the history of the program. Standard procedure for liquid fueled rockets typically involve running the engines at full power while the rocket is bolted down to the launch pad. Flight computers release the bolts after testing determines there are no anomalies.

Watch the abort from CTTechJunkie’s Launchpad Camera:

The historic mission will be the first time a private spacecraft will dock with the International Space Station. Aboard the unmanned cargo capsule are non mission-critical supplies and equipment, including an experiment from Hartford high school students.

NASA and SpaceX officials were quick to keep expectations in check at a Friday press conference.

“This is a test flight. NASA views test flights primarily as learning opportunities, they don’t fit very neatly in characterizations of success and failure,” said Phil McAlister, NASA’s Director of Commercial Space Flight Development.

Shotwell said the company has spent over $680 million on the commercial cargo test program since 2006. That figure is a mix of private investment and public contributions from NASA. Shotwell declined to provide a specific breakdown of public and private funds that made up that figure.

The NASA commercial cargo and crew programs are performance driven. Private firms hoping to get a NASA contract have to reach certain development milestones and raise certain levels of private capital in order to remain in the program. This is in sharp contrast to previous “cost plus” contracting that guaranteed profit margins regardless of performance. NASA considers its relationship to the program participants as an investor.

If the test flight is successful Shotwell hopes that the next mission will begin the process of providing regular cargo resupply missions to the International Space Station. The company has a 12 flight contract with NASA for resupply flights valued at $1.2 billion. If problems arise more test flights might be necessary.

Once on orbit the SpaceX Dragon spacecraft must perform a number of tasks that the company has yet to test in space, including unfurling solar panels and generating power. If all systems work well it will be in range of the ISS by the second day of the mission for maneuvering tests. If those tests pass Dragon will be berthed with the station the following day. It will later return to Earth and will be recovered in the Pacific Ocean.

Provided the problem is not severe, SpaceX will make another attempt on May 22. Shotwell says the rendezvous is challenging because the station’s orbit path needs to align properly to ensure their spacecraft can catch up with the orbiting complex. The ISS travels at over 17,000 miles per hour.


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