Stratolaunch taxi test
Stratolaunch's aircraft prepares for taxi tests at the Mojave Air and Space Port in California on Feb. 24 and 25. Credit: Stratolaunch Systems Corp.

WASHINGTON — The giant aircraft being developed by Stratolaunch as part of an air-launch system is one step closer to its first flight after a new series of taxi tests.

The company said Feb. 26 that it performed a series of medium-speed taxi tests of its aircraft Feb. 24 and 25 at the Mojave Air and Space Port in California. The aircraft reach a top speed of 74 kilometers per hour in the tests.

“The primary purpose of the activity was to evaluate updates made to the steering and primary braking systems. We are excited to report all objectives of this test were achieved,” company spokesperson Alex Moji said in a Feb. 26 email. “The data collected will be used to evaluate and update our flight simulator for crew training.”

The latest tests build upon an earlier series of taxi tests of the plane, performed at lower speeds, in December. Those earlier tests were the first time the plane taxied under its own power.

Stratolaunch has not disclosed a schedule for future tests, including the plane’s first flight. Based on development efforts of other aircraft, more taxi tests are likely at speeds approaching those required for takeoff.

Stratolaunch, funded by billionaire Paul Allen, developed the plane as an air-launch platform. When originally announced in late 2011, the plane was to carry a modified version of a Falcon 9 rocket from SpaceX. The company later switched to a medium-class rocket developed by Orbital ATK, only to set those plans aside a few years later.

The company now plans to initially use the aircraft to carry Orbital ATK’s Pegasus XL rocket, with the ability to host three such rockets on a single flight. That approach, the company argues, could offer benefits particular to national security applications by being able to launch a constellation of small satellites into different orbits on the same flight.

Stratolaunch, though, is also considering developing its own launch system. The company has hired propulsion engineers and has a Space Act Agreement with NASA’s Stennis Space Center in Mississippi to use a test stand there for “testing of its propulsion system test article element 1.”

Company spokesperson Steve Lombardi confirmed in November that the Stratolaunch was in the “early stage” of a propulsion development project that required use of the NASA test stand. “As we’ve said in the past, we’re exploring a number of launch system possibilities to provide reliable access to space.”

The giant aircraft — the largest in the world by wingspan, at more than 117 meters — has remained the center of attention, though, attracting visits by dignitaries such as Vice President Mike Pence, who stopped at Stratolaunch during a tour of Mojave Air and Space Port in California in October. That visit including a photo op standing on top of the aircraft’s wing.

Pence made a passing reference to that visit in remarks Feb. 21 at a meeting of the National Space Council at the Kennedy Space Center. “I walked atop the massive vessel that will soon launch satellites while soaring through the skies,” he said.

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...