Engine Makers Pushing AM, Other Technologies For (Russian) RD-180 Replacement

[DocM]

(AM = additive manufacturing = 3D printing)

http://m.aviationweek.com/space/engine-makers-pushing-am-other-technologies-rd-180-replacement

Engine Makers Pushing AM, Other Technologies For RD-180 Replacement

Rocket-engine developments that evolved from preparations for an advanced strap-on booster to lift the largest version of the planned Space Launch System (SLS) could push a prototype 500,000-lb.-thrust U.S. replacement for Russia?s RD-180 to the test stand in 2.5 years, contractors say.

Dynetics and Aerojet Rocketdyne (AJR) have joined forces on risk-reduction work growing out of NASA?s SLS advanced booster program and the Air Force Research Laboratory (AFRL) Hydrocarbon Boost effort. The goal is to hasten the AR-1 hydrocarbon-fueled rocket engine being proposed by AJR in hopes that Congress and the Pentagon will decide to go all-out on a U.S. powerplant for national security space launch in place of the RD-180.

Congressional defense committees have indicated a willingness to begin funding development of a large hydrocarbon rocket, given uncertainty over long-term availability of the RD-180 in the sanctions war over Russian ambitions in Ukraine. The Air Force is polling industry on options for a replacement engine, and the Dynetics/AJR work?so far only with NASA funding?is providing some of the answers.

?We think a risk-reduction program preceding full-scale development is the way to go to get you the fastest route to a real engine for the lowest cost,? says Steve Cook, a former top-level NASA rocket propulsion engineering manager at Marshall Space Flight Center who has been director of corporate development at Dynetics for the past five years.

To that end, Dynetics and AJR have merged their work for NASA and the Air Force in hydrocarbon rocket technology. The new technologies could remove some of the uncertainty that would go into replacing the 860,000-lb.-thrust RD-180 manufactured in Russia by NPO Energomash with the proposed AR-1 (see artist?s concept), a 500,000-lb.-thrust oxidizer-rich, staged-combustion engine that could be twinned for vehicles requiring more thrust.

That would include the United Launch Alliance Atlas V, currently the launch vehicle of choice for high-value U.S. national security payloads and potentially the next U.S. human launch vehicle as well. As the U.S. and its allies spar with Russia over the ongoing conflict in Ukraine, support for a long-discussed but never-funded U.S. alternative to the RD-180 has been growing (AW&ST May 26, p. 22).

Cook says advance risk-reduction work enabled a tenfold reduction in the time it took for the J-2X engine to reach 100% power in hot-fire testing compared to the RS-68. The J-2X reached full power 29 days after testing started, he says. In the late 1990s, it took the RS-68 320 days to reach the milestone.

?Risk reduction has real, tangible benefits and will save us years in schedule,? says Cook, who was project manager on the Ares launch-vehicle development that was paced by the J-2X upper-stage engine development. ?Our estimate is 2-3 years off schedule and several hundred million dollars in cost, because if you get those key risk areas knocked down to a reasonable level, and you understand the affordability equation, when you make your full-scale development decision, you?ve got a lot more data, so you?re a lot smarter. And when you get going on full-scale acquisition, you?re not trying to understand the technology challenges.?

Scott Seymour, president and CEO of AJR parent GenCorp, says the rocket-engine company is targeting a full-production cost of $20-25 million for each two-engine shipset of AR-1s, with a development cost of $800 million to $1 billion over four years after a contract award (AW&ST June 12, p. 33). Technologies developed in the risk-reduction work by Dynetics and AJR include additive manufacturing (AM) of injectors and other engine elements, new alloys and new nozzle technology.

Materials engineers at AJR have developed a set of alloys they have trademarked as ?Mondaloy? that combines high strength with resistance to burning, making them particularly useful in the oxygen-rich, high-pressure environments that would be found inside the AR-1 and other oxidizer-rich, staged-combustion rockets. The alloys offer cost and reliability advantages over the coatings used to protect components inside the RD-180, also an oxidizer-rich, staged-combustion engine, according to Paul Meyer, senior vice president for advanced programs and business development at AJR.

?We?ve been characterizing the application of Mondaloy inside that thrust chamber itself,? Meyer says. ?We don?t have the normal erosion associated with that oxygen-rich environment. It gives us some reliability. It gives us endurance capability, and it also allows us to reduce some weight. It also helps us from a manufacturing perspective.?

AM is also playing into the risk-reduction work by the two companies. Dynetics and AJR predecessor Pratt & Whitney Rocketdyne used NASA funding under the $37 million Advanced Booster Engineering Demonstration and Risk Reduction (Abedrr) project to study what it would take to resurrect the F-1 Saturn V main engine for the strap-on boosters intended to bring the SLS to the 130-metric-ton capacity mandated by Congress (AW&ST Jan. 21, 2013, p. 20).

While NASA shelved that effort?at least temporarily?in favor of developing a new upper stage for a 105-ton version of the heavy-lift rocket, Dynetics conducted gas-generator hot-fire tests (see photo) and worked with AJR to build engine components, including an F-1 injector, using AM.

?We built and we?re getting ready to test an additive-manufactured rocket engine injector at the 30,000-lb. class,? says Cook. ?The injector itself is the 30,000-lb.-thrust class. Typically, that would have taken 15 months to build. We did it in 15 days.?

The work is continuing at AJR under a separate Air Force cost-sharing contract that the company is using to build and test engine parts made from various materials with large-scale laser-melting AM (AW&ST Aug. 25, p. 12).

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AR-1 (single chamber)