COLORADO SPRINGS – Aerojet Rocketdyne has studied what it would take to replace the Russian-built RD-180 and AJ-26 rocket engines used in the Atlas V and Antares launch vehicles.

The answer is at least four years, with enough money, said Julie Van Kleeck, Aerojet Rocketdyne vice president for Advanced Space & Launch Systems, when asked what it would take to develop new engines domestically if Russia shuts off the supply over the Crimean crisis.

"We believe that it can be done in four years," she said. "Any number you have has all kinds of assumptions on money, requirements, acquisition strategy, but we’ve developed a number of rockets. You can develop a booster engine in four years."

Although Russian Deputy Prime Minister Dmitry Rogozin has threatened to cut off the supply of RD-180s – a two-bell version of the RD-170 that was developed for the Atlas V – for military launches, United Launch Alliance officials say they have received no official notice from NPO Energomash, which builds the engines, or the RD Amross joint venture set up to market the engines in the U.S.

That joint venture includes Aerojet Rocketdyne, and Van Kleek declined to comment on the specific status of RD-180 sales to the U.S. in light of Rogozin’s remarks.

"I can say that the U.S. is capable of developing and fielding products similar to the capability of those that we purchase today," she said. "The country hasn’t committed to developing those products over the past several decades. We’re prepared to do that."

The RD-180 is under consideration as an eventual replacement for the AJ-26 engine that powers the Antares medium-lift launcher, which was developed by Orbital Sciences Corp. to fly cargo to the International Space Station. Those are not military launches, but the AJ-26 is an Aerojet Rocketdyne modification of surplus Soviet-era NK-33 engines and thus the supply is finite.

Orbital has said it has enough AJ-26 engines on hand to fly out its current cargo-delivery contract with NASA.

Van Kleek said her company has studied potential AJ-26 replacements for Orbital, based on its work with the Russian engines to date.

Despite the uncertainty over the RD-180, Van Kleek said Aerojet Rocketdyne is getting ready to build an expendable version of the RS-25D Space Shuttle Main Engine for the heavy-lift Space Launch System (SLS) that NASA is developing for deep-space human exploration. It also has signed a new contract to supply engines for the planned Stratolaunch Thunderbolt vehicle under development by Orbital Sciences for a startup funded by Microsoft co-founder Paul Allen, and is studying the use of those same engines – the venerable RL-10 – as the engine for the "dual-use" upper stage NASA appears to be favoring as the next development effort in the SLS project.

Aerojet Rocketdyne also has signed a new contract with Dynetics for additional work in materials, additive manufacturing and other technologies growing out of work the two companies did on reviving the main engine from the Saturn V. That project was aimed at the advanced booster that will be needed to get the SLS to its congressionally mandated 130-metric-ton capability, but is now considered more likely to follow the dual-use upper stage rather than precede it.

The company also is using additive manufacturing to develop a family of low-cost rocket engines for ascent and in-space propulsion to meet the needs of the U.S. Defense Advanced Research Projects Agency and others. Van Kleek said the company has test fired "printed" rocket engines, and expects to continue the work as new applications pull the technology.