SpaceX scrubs Sunday launch attempt with Intelsat relay satellite – Spaceflight Now

 In Science
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A computer-triggered abort halted the countdown of a Falcon 9 rocket Sunday at NASA’s Kennedy Space Center in Florida, pushing back the next mission in SpaceX’s launch surge until at least Monday.

The 229-foot-tall Falcon 9 rocket was counting down to liftoff with an Intelsat communications satellite at 7:36 p.m. EDT (2336 GMT) Monday, and an iffy afternoon weather forecast gave way to clear skies as clocks ticked toward launch.

An automatic sequencer sent commands to load the two-stage rocket with super-chilled RP-1 kerosene and liquid oxygen propellants, and the Falcon 9’s engines were prepared for ignition and its fuel tanks pressurized for launch during the final minutes of Sunday’s countdown.

But clocks stopped at T-minus 9 seconds after a computer overseeing preset criteria in the rocket’s guidance, navigation and control system ordered an automatic abort. SpaceX’s launch director scrubbed Sunday’s launch attempt a few minutes later as engineers investigated the problem.

“We had a vehicle abort criteria violated at T-minus 10 seconds, a GNC (guidance, navigation and control) criteria,” the launch director said. “We’re still looking into what that is at this time.

“We’re not going to be able to get a recycle in today without going past the end of the window, so we’re officially scrubbed,” he said. “Go ahead and put a 24-hour recycle into work.”

SpaceX began draining the Falcon 9’s propellant tanks at launch pad 39A soon after the scrub.

If SpaceX’s launch team can understand the problem, and correct it if necessary, the Falcon 9 rocket could be fueled again Monday for a 58-minute launch window that opens at 7:37 p.m. EDT (2337 GMT).

The launch of the Intelsat 35e communications satellite is the third in a series of Falcon 9 flights over the last two weeks. If the rocket blasted off Sunday, it would have been the third Falcon 9 launch in a little over nine days, and the second from the same launch pad in Florida.

The feverish pace of activity at SpaceX’s Cape Canaveral facilities seeks to break the record for the fastest turnaround between launches at pad 39A. SpaceX and Intelsat are eager to get the rocket off the ground before the U.S. Air Force’s Eastern Range becomes unavailable to support the launch after the July 4 holiday.

The Falcon 9 rocket assigned to Intelsat 35e’s mission conducted a static fire test Thursday evening at pad 39A, less than 72 hours before the opening of Sunday’s launch window. Ground crews rolled back the Falcon 9 to its hangar Friday afternoon and attached the Intelsat 35e satellite to the rocket in time to return to the pad in the predawn hours Sunday.

“We had to add additional resources to try to turn around the campaigns in such a short time,” said Ken Lee, Intelsat’s senior vice president of space systems, in an interview Sunday at Cape Canaveral. “More manpower — a lot of pressure — but as usual our team is mission-oriented, so when they see a target they’re going to do the best they can do meet that date.

“They’ve been working almost around-the-clock, and we brought in additional engineers to make sure that we did the work that we needed to do without any shortcuts.”

Credit: Stephen Clark/Spaceflight Now

The 14,905-pound (6,761-kilogram) Intelsat 35e communications satellite, built by Boeing, is the heaviest spacecraft ever launched by SpaceX toward a perch in geostationary orbit, a circular loop more than 22,000 miles (nearly 36,000 kilometers) above Earth’s equator commonly used by broadcast and data relay stations.

At that altitude, orbital mechanics require a satellite to fly around Earth at the same speed it rotates, allowing a spacecraft to hover over a fixed geographic location, an ideal situation for communications applications.

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