Last month, US-based Northrop Grumman conducted its first ground test of an extended-length 63in-diameter Graphite Epoxy Motor (GEM 63XL) at Promontory in Utah.

This variation of the company’s GEM 63 ‘strap-on’ booster was developed in partnership with United Launch Alliance (ULA) to provide additional lift capability to the Vulcan Centaur, a two-stage-to-orbit heavy-lift space launch vehicle scheduled for lift-off next year.

Charlie Precourt, vice president of propulsion systems at Northrop Grumman, said: “Our new GEM 63XL motors leverage its flight-proven heritage while using ‘state of the art’ manufacturing technology to enhance launch vehicle heavy-lift capabilities. The GEM 63XL increases thrust and performance by 15-20% compared to a standard GEM 63.”

During the static test, the motor fired for about 90sec, producing nearly 449,000lb of thrust to qualify the motor’s internal insulation, propellant grain, ballistics and nozzle in a ‘cold-conditioned environment’.

Northrop Grumman has supplied rocket propulsion to ULA and its heritage companies for a variety of launch vehicles since 1964. The development of the GEM family of strap-on motors began in the early 1980s with the GEM 40 to support the Delta II launch vehicle.

The company then followed with the GEM 46 for the Delta II Heavy, and the GEM 60, which “flew 86 motors over 26 Delta IV launches” before being retired in 2019 with 100% success.

The first flight of the GEM 63 motors will be on a ULA Atlas V launch vehicle planned for the fourth quarter of 2020; GEM 63XL motors will support the Vulcan rocket in 2021.