The political battle continues over the next-generation evolved expendable launch vehicle.

WASHINGTON — As the House and Senate move to wrap up negotiations on the 2018 defense policy bill, the Air Force’s “launch systems enterprise” anxiously is waiting to see the final language in the National Defense Authorization Act. One of the concerns: Will Congress limit the options available to the Air Force to phase out Russian engines from U.S. military space launch vehicles?

The political battle over the next-generation evolved expendable launch vehicle started about three years ago when Congress set a deadline for the Air Force to stop funding the Russian RD-180 heavy rocket engine. The Air Force last month issued a request for vendor proposals and expects to have at least three options to choose from. With the completion of the NDAA just days away, Air Force officials worry that the House language, if adopted, would restrict the path forward to end U.S. dependence on Russian engines.

The acquisition strategy was laid out in an Oct. 5 request for proposals for the next-generation EELV. If this plan is carried out, the Air Force said, it would be able to phase out the RD-180 by 2022. If the House NDAA language ends up becoming law, it would set things back at least two years, said Claire Leon, director of the Launch Enterprise Directorate at the Space and Missile Systems Center, in Los Angeles, California.

The larger goal is to find an alternative to the Atlas 5 rocket that uses the RD-180. One of the disagreements between the Air Force and House Armed Services’ strategic forces subcommittee Chairman Mike Rogers (R-Alabama) is over how to go about doing that. The Air Force would prefer a wholesale approach, including a new vehicle design, whereas Rogers has pushed for a straight-up replacement of the main stage propulsion system. Both sides have gone back and forth. The Air Force has essentially prevailed in each of the past couple of legislative cycles, but it still fears it will not have enough flexibility to invest in new launch capabilities.

The RFP said the Air Force wants to “leverage commercial launch solutions in order to have at least two domestic, commercial launch service providers.” Leon said the plan is to select three vendors for prototype development.

“It’s key to have flexibility,” Leon told SpaceNews Thursday at the Pentagon. The way the House NDAA was written, “we could not execute our acquisition strategy. We’d have to change it, and redo the RFP that’s already released.”

Leon said her office is “hopeful that they’ll tweak the language.” There is “tremendous momentum” in the industry right now, she said. “We’ve invested a lot to get as far as we have. … If we can just keep going and leverage the momentum that we have, then 2022 is really viable.” But if the NDAA keeps that restrictive language, “we would have to completely regroup.”

The Air Force would like to have more than one path to replace the RD-180 engine, such as investing in a new booster that the United Launch Alliance is developing that could replace Atlas V and the other heavy-lift Delta IV rocket.

“We’d like to be given requirements, not told how to do them,” said Leon.

Her statements echo the Trump administration’s objections to Section 1615. The White House said the language “would restrict development of new space launch systems, including those whose development is significantly funded by industry, in exclusive favor of rocket engines and modifications to existing launch vehicles.”

It’s been three years since Congress stepped into to mandate the phase-out of the RD-180 Russia’s annexation of Crimea.

Air Force Lt. Gen. John F. Thompson, commander of the Space and Missile Systems Center, played down the disagreements with the House. “I’m not convinced that we will have those political restrictions,” he said Thursday. “I think the Air Force approach we have taken in EELV strikes the right balance in terms of launch capability, competition and driving out cost.”

Agreements have been signed with ULA, SpaceX, Orbital ATK and Aerojet Rocketdyne to “help us get us get off the Russian RD-180 and ensure us access to space,” Thompson said.

Industry consultant Loren Thompson, who works with companies in the EELV program, said Air Force assertions that the language “precludes the service from investing in a new launch vehicle, as opposed to engine” is not how the committee sees it. “Chairman Rogers and others are concerned that any distraction from removing Russian engines will prolong the period of U.S. dependence,” Thompson said. “I don’t think Rogers is trying to dictate a solution, he’s just determined to stop using Russian engines. If the solution to that national-security issue also helps the commercial industry, he’s fine with that. But it isn’t his core concern.”

Mike Tierney, a space industry adviser at Jacques & Associates, said differences will be ironed out in the final NDAA. “The national security imperative to keep our military space investments on schedule typically overcomes the political environment,” he said. “That is what has generally occurred ever since the RD-180 became an annual legislative focus, whether it is how many more RD-180s or how the Air Force can invest to replace that engine.”