Stratolaunch Roc plane
Stratolaunch says it will increase the pace of test flights of its Roc aircraft this year as it prepares for a first flight of a hypersonic vehicle before the end of the year. Credit: Stratolaunch

WASHINGTON — Stratolaunch flew its giant aircraft Jan. 16 for just the third time as company executives promise a higher rate of flight activities this year, including the first flight of a hypersonic test vehicle.

The plane, known as Roc, took off from Mojave Air and Space Port in California at 11:47 a.m. Eastern. The plane returned to the airport four hours and 23 minutes later after a flight that took the plane to a peak altitude of more than 7,160 meters and top speed of 330 kilometers per hour.

The flight met all of the company’s objectives, including testing the retraction and extension of the landing gear on the left fuselage. The successful flight “meant we were one step closer to hypersonic flight,” Zachary Krevor, president and chief operating officer of Stratolaunch, said in a call with reporters after the flight.

The flight took place nearly nine months after the previous Roc test flight. That, in turn, took place two years after the inaugural flight of the plane, originally developed to serve as a platform for an air-launch system. After that first flight, the company changed ownership and shifted direction to focus on hypersonic flight testing.

Under that new direction, Stratolaunch will use Roc as a platform for launching a series of hypersonic vehicles called Talon. A prototype vehicle, called TA-0, will be flown for a drop test over the Pacific Ocean. That will be followed by the first powered vehicle, TA-1, as soon as the end of the year.

That schedule will require Stratolaunch to accelerate the pace of aircraft testing. “You’ll see us flying more frequently,” Daniel Millman, chief technology officer of Stratolaunch, said on the call. “Before the end of the year, we plan to and hope to launch our first hypersonic test vehicle.”

The next flight will test retracting the entire landing gear of the plane. “That’s when we can really begin envelope expansion in earnest,” Millman said. On the following flight, the company will install the pylon on the central wing segment to which Talon vehicles will be attached.

Krevor and Millman declined to give a schedule for the next test flight, stating that it will depend on the review of data from this flight. The number of test flights will also depend on the vehicle’s performance as they gradually increase the altitude and speed of Roc to that “comparable to what you expect on a commercial airliner,” said Krevor. “It will be our goal to finish out the envelope expansion by the end of this year, and the number of flights will be dictated by the performance of the aircraft.”

Both TA-0 and TA-1 are nearing completion, Millman said, including powering up TA-1 for the first time last month. He added the company is working “hand-in-hand” with Ursa Major Technologies, the company that is providing the rocket engine that will propel TA-1, in qualification testing of that engine.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...