Last week, the team at Stratolaunch announced it is one step closer to providing convenient, reliable, and routine access to low Earth orbit. For the first time, the company started the aircraft’s six Pratt & Whitney turbofan engines, completing the first phase of engine testing. In addition to fuel testing, we began testing the flight control system. According to Stratolaunch, the company has “exercised the full limits of motion and rate of deflection” of the aircraft control surfaces on the wing and stabilizers.

“Engine testing was conducted with a build-up approach and consisted of three phases,” Stratolaunch explained. “First as a ‘dry motor,’ where we used an auxiliary power unit to charge the engine. Next, as a ‘wet motor,’ where we introduced fuel. 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.”

With a wingspan of 385 feet, the Stratolaunch the largest composite aircraft ever built. The aircraft is 238 ft. from nose to tail and stands 50 ft. tall from the ground to the top of the vertical tail.

Back in May, the Stratolaunch was towed outside for the first time to begin its ground test phase. The jet’s airframe is made mostly of CFRP. Stratolaunch constructed a separate building dedicated to making the carbon composite components, one sized to the airplane’s largest parts: four wing spars each more than 62 meters long. Curing the spars required Scaled Composites to create a mobile oven that moved along the spar given the lack of an oven big enough to hold the entire component. A team of 300 engineers and fabricators designed, built, and hand assembled the twin fuselage vehicle as an air launch platform with a payload capacity of about 550,000 lbs.

Over the next few months, the company plans to continue testing the aircraft’s engines at higher power levels and varying configurations, culminating with the start of taxi tests.