Virgin Galactic’s plans to supplement its suborbital human spaceflight business by launching small satellites from its WhiteKnightTwo carrier aircraft are advancing with hot-fire ground tests of the two kerosene-fueled rocket engines it has designed for the application.

Developed and built by Virgin Galactic engineers, the 3,500-lb.-thrust NewtonOne and 47,500-lb.-thrust NewtonTwo are the first- and second-stage engines, respectively, for the company’s planned LauncherOne rocket.

NewtonOne, the upper-stage engine, completed a full-mission duty cycle of 5 min. on the company’s test stand on Mojave, Calif. The larger main-stage engine has had multiple firings for short durations, including one that came within a 12-hr. turnaround for engine swap out to demonstrate responsiveness, according to Virgin Galactic. Longer-duration tests of the NewtonTwo engine are planned “in the coming months,” the company said.

“Combined with parallel progress made by the company in advanced tank and avionics technology, we are now well on our way to providing customers with the lowest-cost opportunity for small satellite manufacturers and operators to buy a dedicated ride to space,” said George Whitesides, the Virgin Galactic CEO.

LauncherOne is being designed to deliver a 500-lb. payload (225 kg) to low inclination equatorial low Earth orbit, and 225 lb. (100 kg) to polar sun-synchronous orbit at higher altitudes. Higher-capability configurations are also planned, the company says.

The two-stage rocket will be drop-launched from WhiteKnightTwo in the same fashion as the company’s SpaceShipTwo suborbital human vehicle now undergoing flight testing. Falling from an altitude of 50,000 ft., its main-stage engine will ignite 4 sec. after release. Because the rocket will be air-launched, the company is marketing its relatively simple ground operations from runways around the world.

Initial plans call for launches using the runway at the Spaceport America facility in New Mexico, Virgin’s commercial base of operations, and other U.S. facilities. Later flights could come from the planned spaceport in Abu Dhabi, home of Virgin partner Aabar Investments PIS, and elsewhere.