Stratolaunch milestone

At 385ft the Stratolaunch has the widest wingspan of any aircraft ever built
A twin fuselage is one of the most distinctive features of the Stratolaunch, pictured here on the Mojave Air and Space Sport runway during its first taxi test.

THE STRATOLAUNCH is like no other aircraft, truly standing out with its six engines, huge wingspan and twin fuselages. In December, this giant aircraft (N351SL), manufactured by Stratolaunch Systems Corp, undertook a low-speed taxi test on the Mojave Air and Space Port runway, the first time it moved under its own power.

The aircraft taxied down the runway at 25kts (46km/h).

Stratolaunch said all test objectives to assess the aircraft’s ability to steer and stop were met. A ground team monitored steering, braking, antiskid and telemetry systems during the test from the Stratolaunch Mission Control Centre at Mojave. This recently opened facility will be the hub for testing the aircraft and will eventually control commercial operations.

George Bugg, the aircraft programme manager at Stratolaunch Systems Corp, commented: “Our crew was able to demonstrate ground directional control with nose gear steering, and our brake systems were exercised successfully on the runway.”

Jean Floyd, Chief Executive Officer, Stratolaunch Systems Corp, added: “Once we have safely completed low-speed taxi tests, we will begin the next phase of taxi testing, which will include increased speeds.”

The Stratolaunch was rolled out of the company’s hangar at Mojave in May 2017. In the following weeks, initial tests started on the aircraft’s six 56,000lb (250kN) Pratt & Whitney PW4056 engines.

This testing consisted of three phases. First, an auxiliary power unit was used to charge the engines, then a ‘wet motor’ test saw fuel introduced to the engines, and finally the engines were started one at a time and allowed to idle.

In these initial tests, each of the six engines operated as expected. A further series of assessments on the PW4056s were then carried out at higher power levels and in varying configurations before the initial low-speed taxi took place.

Each of the aircraft’s six fuel tanks was filled independently to check the operations of fuel mechanisms and to validate the tanks were properly sealed. The full limits of motion and rate of deflection of control surfaces on the wing and stabilisers were also assessed, and checks undertaken on electrical, pneumatic and fire detection systems and the flight control system.

The Stratolaunch has the widest wingspan of any aircraft yet built at 385ft (117m). To put this into perspective, its wingspan is 95ft (29m) wider than the 290ft (88.4m) span on the sole Antonov An-225 Myria – for decades the largest aircraft flying – and 65ft (19m) wider than the 320ft 11in (97.5m) span on the single Hughes H-4 ‘Spruce Goose’, briefly flown in 1947.

The Stratolaunch is 238ft (73m) long, around the same length as an A380, but shorter than the 275ft 7 inch (84m) An-225. It stands 50ft (15m) high at the tail, is fitted with 28 wheels, has an empty weight of 500,000lb (226,796kg) and is designed for a maximum take-off weight of 1,300,000lb (589,760kg). This gigantic aircraft has been created specifically for the commercial launch of satellites into space from high altitude.

Stratolaunch Systems Corp was founded in 2011, backed by billionaire Microsoft co-founder Paul Allen, to develop a reuseable platform to make access to low Earth orbit more convenient, reliable and routine, and to create more opportunities for commercial, philanthropic and government organisations to access space. Stratolaunch is designed to carry a single Orbital ATK Pegasus XL vehicle between its two fuselage sections into orbit and carry payloads up to approximately 550,000lb (249,475kg). The aircraft is the result of a partnership between Stratolaunch Systems Corp and Mojave-based Scaled Composites. The aircraft’s first flight is due in 2019. Mark Broadbent

The Stratolaunch is designed to carry an Orbital ATK Pegasus XL vehicle into orbit, which will be carried between the two fuselage sections.
All photos Stratolaunch Systems Corp