WASHINGTON – The U.S. Air Force has chosen to invest up to $241 million in rocket propulsion systems Orbital ATK and SpaceX pitched as a way to end Air Force dependence on the Russian-built rocket engine it uses to launch most U.S. national security payloads.

In announcing the Orbital ATK and SpaceX awards Jan. 13, the Air Force said it may award additional contracts over the next few months.

“The Air Force is still in negotiations with the remaining offerors and subsequent awards, if any, will occur over the next few months,” the Air Force’s Los Angeles-based Space and Missile Systems Center said in a statement.

Orbital ATK won the biggest share of the money awarded Jan. 13. The Dulles, Virginia-based company stands to receive at least $46.9 million, and perhaps as much as $180 million, to develop three rocket propulsion system technologies the contract announcement said are “intended for use on an Orbital ATK next generation launch vehicle.”

In a Jan. 14 press release, the company said it would develop a “solid rocket propulsion system.”

“All the best features of solid motors, including operational reliability, high lift-off thrust, shorter development schedules and, importantly, affordability have improved over time with the advancement of new technologies,” Charlie Precourt, vice president and general manager of Orbital ATK’s propulsion systems division, said in the release. “This means we can offer the Air Force a low technical risk and very cost-competitive American-made propulsion alternative.”

Specifically, Orbital ATK will combine the Air Force money with at least $31 million, and as much as $124 million, of its own to develop the GEM 63XL strap-on solid rocket motor, the Common Booster Segment solid rocket motor, and an extendable nozzle for Blue Origin’s BE-3U upper stage engine.

Blue Origin uses the BE-3 for its New Shepard suborbital rocket. The BE-3 also is one of three upper-stage engines United Launch Alliance is considering for Vulcan, the Denver company’s next-generation rocket.

“We are proud to provide the BE-3U high energy upper stage solution for Orbital ATK’s next generation launch vehicle,” Rob Meyerson, Blue Origin’s president, said in an email to SpaceNews. “The BE-3U is a variant of our BE-3 engine that powers our New Shepard space vehicle for both launch and landing.”

The GEM 63XL solid rocket motor also is being developed for ULA’s Vulcan rocket.

SpaceX, meanwhile, will get at least $33.6 million, and perhaps as much as $61 million, to continue development of its reusable methane-fueled Raptor engine. SpaceX is expected to match the Air Force’s investment in Raptor with at least $67 million, and as much as $123 million, according to the Air Force contract announcement.

In testimony before a House subcommittee last year, Jeff Thornburg, then SpaceX’s senior director of propulsion, said the Raptor would have “significant applications” for national security and would be the first large liquid engine in the world built largely with printed parts.

The Air Force is under pressure to end its dependence on the RD-180, the Russian-built engine that powers the main stage of United Launch Alliance’s Atlas 5 rocket.

Congress has directed the Defense Department to develop a domestic propulsion systems that would enable the Air Force by 2019 to end its reliance on RD-180.

When the Air Force solicited proposals in June, it said it intended to award a total of $160 million to fund work on both main- and upper-stage rocket engines. Industry would be required to cover at least one-third of the costs of their proposed development efforts, but the actual size of the government investment would vary from proposal to proposal.