Northrop Grumman Tests New Motor for U.S. Space Force’s Vulcan Centaur Rocket Our Bureau 1751 Northrop Grumman Corporation conducted a validation ground test of an extended length 63-inch-diameter Graphite Epoxy Motor (GEM 63XL) today in Promontory. 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 rocket. Vulcan Centaur is a two-stage-to-orbit heavy-lift launch vehicle under development 2014–2021 by United Launch Alliance (ULA), principally funded through the U.S. government's National Security Space Launch (NSSL) competition and launch program, to meet the demands of the United States Space Force and U.S. national security satellite launches.