A Falcon 9 carrying X-37B beneath its protective shroud minutes before its Sept. 7 liftoff from Kennedy Space Center, Florida. Credit: SpaceX video

WASHINGTON — With Hurricane Irma looming off the Florida coast, SpaceX beat unfavorable weather odds Thursday morning to send the U.S. Air Force’s X-37B reusable spaceplane back into orbit for its fifth classified mission.

A Falcon 9 carrying the Boeing-built X-37B hidden inside its protective shroud lifted off a 10:00 a.m. Eastern from NASA Kennedy Space Center’s Launch Complex 39A.

By noon, the Air Force had declared the launch a success.

“Congratulations @45thSpaceWing and @SpaceX on a successful launch (and landing!) of the Falcon 9 rocket carrying OTV-5 into orbit” pic.twitter.com/WmzbhC7M36

— Gen. Jay Raymond (@AFSpaceCC) September 7, 2017

This was the first X-37B be launched on board a Falcon 9 and following stage separation, the rocket’s first stage successfully landed at SpaceX’s Landing Zone 1  at Cape Canaveral Air Force Station, Florida, the company said.

Officials at neighboring Patrick Air Force Base said Tuesday that the 45th Space Wing had begun their hurricane preparations sooner than usual so that they could still support today’s launch attempt. On Wednesday, forecasters were giving only a 50 percent chance of acceptable weather for today’s launch, with the odds of favorable conditions shrinking to 40 percent for a backup opportunity Friday.

While X-37B’s mission has been tentatively scheduled to last 270 days, the Air Force has said that could change depending on the testing progress, how the vehicle performs in orbit and conditions at the landing facility.

The X-37B mission is the second national security launch for SpaceX since the Air Force certified the Falcon 9 in 2015 to compete for Defense Department business. In May, SpaceX launched a classified payload for the National Reconnaissance Office, NROL-76.

That launch followed back-to-back wins of the first two GPS 3 launch contracts the Air Force put out for bid. A third competition, for the mid-2018 launch of the multi-spacecraft Space Test Program-3 mission, went to United Launch Alliance in June. That launch, which will employ ULA’s most-powerful variant of its Atlas 5 rocket, would have required SpaceX to have used its Falcon Heavy, which is still months from its debut.

X-37B has been launched into orbit four times since 2010, accumulating a total of 2,085 days in space. All four missions have been launched atop Atlas 5s.

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Air Force Secretary Heather Wilson disclosed during an early June congressional hearing that SpaceX, not ULA, would be launching X-37B this time around. She suggested that price was a factor in the Air Force’s decision to go with Falcon 9. “The benefit we’re seeing now is competition,” she said. “There are some very exciting things happening in commercial space that bring the opportunity for assured access to space at a very competitive price.”

This mission has a tough act to follow. X-37B’s fourth mission set an endurance record, racking up 718 days in orbit before landing in early May at Kennedy Space Center, Florida.

X-37B began as a NASA program in 1999, but transferred to Defense Advanced Research Projects Agency in 2004.  DARPA transferred it to the Air Force in 2006.  Total program costs and budget line are classified.

Mike Fabey is SpaceNews' senior staff writer covering military and national security space matters. Mike previously covered as Defense News’ air and space warfare reporter in 2005 and 2006. Mike was an Aviation Week...