Stratolaunch Aircraft hits another milestone with completion of first phase of engine testing

The world’s largest aircraft is moved a step closer to its first flight this week.

Stratolaunch Systems Corporation completed the first phase of engine testing for its Stratolaunch aircraft at its facility at the Mojave Air and Space Port in California.

“For the first time we started the aircraft’s six Pratt & Whitney turbofan engines,” said Jean Floyd, chief executive officer of Stratolaunch Systems Corporation.

Engine testing was conducted with a build-up approach and consisted of three phases.

First as a “dry motor,” where an auxiliary power unit was sued to charge the engine. Next, as a “wet motor,” where fuel was introduced. Finally, each engine was started one at a time and allowed to idle. In these initial tests, each of the six engines operated as expected.

“It has been a busy, exciting, and productive several months since the aircraft left the hangar for the first time and began ground and flight line testing,” said Floyd.


The team completed fuel testing, testing all six fuel tanks to ensure proper operations. Each of the six fuel tanks were filled independently to ensure proper operations of fuel mechanisms and to validate the tanks were properly sealed.

In addition to fuel testing, the company began testing the flight control system.

“So far we have exercised the full limits of motion and rate of deflection of control surfaces on the wing and stabilizers,” said Floyd.

Building up to this week’s engine tests, prerequisite testing of the electrical, pneumatic, and fire detection systems were completed successfully.

“Over the next few months, we will continue to test the aircraft’s engines at higher power levels and varying configurations, culminating to the start of taxi tests,” said Floyd. “As we work toward that milestone, we look forward to sharing additional details on the aircraft’s journey.”


The Stratolaunch aircraft is designed to provide convenient, reliable and routine access to low Earth orbit.

The Stratolaunch weighs approximately 500,000 pounds without any cargo, and is designed to carry a maximum takeoff weight of 1.3 million pounds. The plane rolls around with the aid of 28 wheels. Once airborne, it is powered by six 747 aircraft engines.

In 2016, Stratolaunch signed a deal with Orbtial ATK. Under the deal, Orbital ATK will initially provide multiple Pegasus XL air-launch vehicles for use with the Stratolaunch aircraft to provide customers with unparalleled flexibility to launch small satellites weighing up to 1,000 pounds into low Earth orbit. Pegasus has carried out 42 space launch missions, successfully placing more than 80 satellites into orbit for scientific, commercial, defense and international customers.

The aircraft was unveiled during a rolling out ceremony earlier this year in Mojave. Stratolaunch Systems Corporation was officially announced in December 2011 by Microsoft co-founder Paul G. Allen and Scaled Composites founder Burt Rutan. The Stratoluanch aircraft was built by Mojave-based Scaled Composites, now owned by Northrop Grumman. On Sept. 18, 2017, Northrop Grumman announced plans to purchase Orbital ATK.


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