Stratolaunch has begun full-scale testing of its rocket engine’s preburner after completing the first hot-fire test earlier this month.
The PGA Engine, which is named after Stratolaunch’s founder Paul G Allen, has been developed by the company to produce 200,000 lbf (890kN) of thrust. The liquid hydrogen-oxygen engine will have the highest specific impulse of any rocket engine using that propellant and will release only water as a byproduct.
According to the latest reports, the tests, which are being conducted at NASA’s Stennis Space Center in Mississippi, have tested the preburner up to 70% power so far.
Stratolaunch said that its hydrogen pre-burner has been designed, fabricated, assembled and tested in less than a year. The first phase of testing for the PGA Engine was completed in September 2017.
In the last 12 months, engineers have successfully completed propellant cold flows, igniter activation, and hot-fire sequence development for the preburner, culminating in the hot-fire tests, it added.
Jeff Thornburg, vice president of propulsion at Stratolaunch said, “This is the first step in proving the performance and efficient design of the PGA engine. The hot-fire test is an incredible milestone for both the propulsion team and Stratolaunch.”
The PGA Engine is the first US hydrogen-staged combustion engine to be built since the Space Shuttle Main Engine. Stratolaunch has used rapid prototyping to develop the engine, resulting in an entirely additively manufactured preburner.
The preburner testing is set to continue over the coming months, with increases in both the duration and power-levels of the hot-tests.
The PGA Engine will support multiple configurations of Stratolaunch’s launch vehicles, which will be drop-launched from a large mothership aircraft currently being developed at the Mojave Air and Space Port in the USA.
The dual-fuselage “launch platform”, claimed to be the largest aircraft in the world with a wingspan of 385ft (117 m), will carry its payloads to an altitude of 35,000ft (10,700m) before launching them via the launch vehicles . The first vehicle to be used on the platform, the Pegasus, is scheduled to be in use by 2020 and will be able to carry payloads, most likely commercial satellites, of up to 370kg (815 lb).