stratolaunch test
Stratolaunch said Sept. 19 it successfully tested the six jet engines that power the giant aircraft that will serve as a launch platform. Credit: Stratolaunch

WASHINGTON — Stratolaunch announced Sept. 19 that the company has achieved another milestone in the development of a unique giant aircraft that will serve as a launch platform.

The company said that it successfully tested at its Mojave, California, facility the six Pratt & Whitney PW4056 turbofan jet engines that will power the aircraft. Each engine is capable of producing 56,750 pounds-force of thrust.

The engines came from two Boeing 747 jetliners that Stratolaunch acquired as part of the development of the one-of-its-kind plane. The engines, the company said in a statement, were put through a series of tests, including one where the engines were started one at a time and allowed to idle. “In these initial tests, each of the six engines operated as expected,” the company said.

Stratolaunch has tested other aircraft systems as well, including control surfaces and electric, pneumatic and fire detection systems, the company said.

“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,” the company stated, not giving a more specific schedule for the flight test program.

The company rolled the aircraft out of its hangar for the first time in May. The twin-fuselage airplane, made of carbon composite materials, has a wingspan of more than 117 meters, making it the largest in the world by that metric. The plane weighs 226,800 kilograms empty, and 50 percent more when fully fueled. It can accommodate payloads weighing nearly 250,000 kilograms, attached to the wing segment between the twin fuselages.

Despite the plane’s giant size, Stratolaunch plans to initially use the aircraft as a platform for Orbital ATK’s Pegasus XL rocket, which is currently launched from a much smaller L-1011 airplane. The Stratolaunch plane will ultimately have the ability to carry three Pegasus rockets that could be launched one at a time on a single flight. An initial launch, the company said in May, could take place as early as 2019.

A recent deal could combine two of Stratolaunch’s partners. Scaled Composites, who developed the aircraft for Stratolaunch, is owned by Northrop Grumman, which announced Sept. 18 a deal to acquire Orbital ATK for $9.2 billion.

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...