Antares Upgrade Will Use RD-181s In Direct Buy From Energomash
Dec 16, 2014 Frank Morring, Jr. | Aviation Week & Space Technology
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Orbital Sciences Corp. will buy directly from Russia’s NPO Energomash a new rocket engine with a long heritage, to replace the surplus Russian powerplants tentatively implicated in the Oct. 28 failure of an Antares launch vehicle with a load of cargo for the International Space Station (ISS).
Designated the RD-181, the new engine will be used on Antares in shipsets of two to accommodate as closely as possible the two-engine configuration built around the AJ-26 engines supplied by Aerojet Rocketdyne, Orbital Sciences managers said Dec. 16.
A descendant of the RD-171 that powers the Ukrainian-built Zenit launch vehicle, the RD-181 will be manufactured in the same Khimki factory that builds the RD-180 used on the United Launch Alliance Atlas V. It closely resembles the RD-191 on Russia’s new Angara launcher and the RD-151 that powers South Korea’s Naro-1 launch vehicle.
In testing at Energomash, “the RD-181s have seen more than two times the Antares flight duration to date, and if you take a look at some of the heritage of this engine, the RD-151 and the RD-191 combined have over 10 hr. of test time for their configuration testing,” said Mark Pieczynski, Orbital’s vice president for space launch strategic development.
Like the AJ-26, the single-thrust-chamber, single-nozzle RD-181 uses liquid oxygen and refined petroleum (RP) as propellants, generating a sea-level performance in the two-engine configuration of 864,000 lb. thrust with a specific impulse of 311.9 sec. That is equivalent to the twin-nozzle RD-180, but the two engines are a better fit with the Antares main stage, built for Orbital by Ukraine’s Yuzhmash.
Orbital has picked a new Russian engine to power the Antares medium-lift launcher, after the Oct. 28 failure of this vehicle tentatively attributed to its AJ-26 engines. Credit: NASA Wallops Flight Facility.
“While there is no such thing as a plug-and-play in this business, the RD-181 in its dual-engine configuration is about as close as you could possibly get to replacing the current twin AJ-26 engines in Antares, so it minimizes the redesign of the core,” Pieczynski told Aviation Week. “It allows us to keep the core nearly identical.”
Ron Grabe, executive vice president and general manager of Orbital’s Launch Systems Group, said his company has been looking for an engine to replace the AJ-26 for three years. Two of the surplus Russian powerplants suffered major failures in acceptance tests at the Stennis Space Center before the October failure shortly after liftoff from the Antares pad at NASA’s Wallops Flight Facility in Virginia.
“We evaluated several alternatives, really all available alternatives both foreign and domestic,” Grabe said Tuesday. “Ultimately, we decided upon the RD-181 engine because it offered the best combination of schedule availability, technical performance and cost compared to the other possible options. The RD-181 came out on top of the evaluation in terms of the performance improvement that it offered and its cost-effectiveness, but where it really stood out for us as the clear winner was with regard to its near-term availability.”
Pieczynski said Energomash will deliver the first shipset next summer and a second in the fall of 2015. Planning is still underway for integrating the new Russian engines into the series of existing and on-order Antares vehicles, the managers said, but the company intends to mount the first shipset in an Antares for a hot-fire test on the repaired Wallops pad next year.
“The first shipset that we receive in mid-summer of next year will be integrated into the booster,” Pieczynski said. “And then in the fall,, our plan is to conduct an on-pad static fire to prove out that system in the core, just as we did in the existing Antares system, where we strapped the first stage down to the pad, conducted about a 29-sec. hot fire and then we shut it down.
“In the meantime, we will be receiving our second set of engines in the fall of 2015. Our plan is to then use that test article as our first launch, but with another set of engines arriving, should we need to do some additional work that we don’t anticipate today on that test article, we will have another set of engines that will be ready to be incorporated into a core vehicle.”
Orbital has selected the Atlas V 401 as a substitute for Antares until it has finished the upgrades, as it works to complete its $1.9 billion contract to deliver 20,000 kg (44,000 lb.) of cargo to the ISS by the end of 2016. Ultimately, the RD-181 will be able to lift 20% more cargo to the space station than the AJ-26 shipsets, in conjunction with an upgraded solid-fuel upper stage that flew on the failed October mission and an extended Cygnus cargo carrier already in the works. But the new engines will be held back to the AJ-26 level until the thrust structure and tankage on the Antares core stage can be modified to accommodate the increased performance, which will be 100,000 lb. thrust more than provided by the AJ-26-powered variant.
Congressional concern about Russian aggression in the Crimean peninsula led to a ban in the new National Defense Authorization Act (NDAA) on using RD-180s purchased after Russia occupied the Ukrainian territory on Feb. 1. Grabe said that legislation will not affect the deal to buy RD-181s from Energomash.
“We’ve coordinated with all relevant congressional committee staffs to keep them informed of our decision,” Grabe said.
“Certainly the NDAA places future restrictions on the use of the Russian engines for national security space applications. Our application is in civil space. There’s a long history of U.S.-Russian cooperation in civil space, dating back to Apollo-Soyuz in the 1970s at the height of the Cold War. Since our immediate objective is in civil space supporting the International Space Station, it’s got a slightly different twist or perspective than supporting national security space. NASA already relies on cooperation with its Russian partner in other ways to execute the ISS program [including] crew transport. Certainly it would not make sense to restrict the use of engines manufactured in Russia on a program that’s already inherently dependent on cooperation between the United States and Russia.”
Orbital hopes eventually to use the Antares with its new Russian engines for commercial satellite launches, as well as in follow-on ISS cargo-delivery work already out for bid. Orbital Chairman/CEO David Thompson has vowed that the company will finish its current contract without increasing the cost to NASA—and with four more flights instead of the five originally planned because of the performance enhancements in the launch vehicle and Cygnus (AW&ST Nov. 17, p. 35).
Pieczynski said the company’s contract with Energomash calls for the delivery of as many as five Antares shipsets of the RD-181 per year, although there will not be a need for that many engines initially.
“Our contract with Energomash covers our obligations under the current [station cargo-delivery] contract, and hopefully anticipating an award for the next phase,” Grabe said. “Beyond that, we have options that, if exercised, would satisfy our requirements out beyond 2020.”
