Orbital Contracts Russian RD-181 Engines to Launch Future Antares Flights

Orbital will employ Russian RD-181 engines to replace the failed AJ-26 engines which led to the total loss of the company's Orb-3 ISS resupply mission for NASA in Oct. 2014. Photo Credit: Orbital Sciences Corporation
Orbital will employ Russian RD-181 engines to replace the failed AJ-26 engines which led to the total loss of the company’s Orb-3 ISS resupply mission for NASA in Oct. 2014. Photo Credit: Orbital Sciences Corporation

When an Orbital Sciences Corporation Antares rocket exploded seconds after liftoff on the company’s third contracted NASA resupply flight to the International Space Station (ISS) on Oct. 28, 2014, the first thing that came to everyone’s mind was the 40-year-old Soviet-era Russian NK-33 engines (refurbished by Aerojet Rocketdyne and redesignated as the AJ-26) used to fly the rocket. Antares had flown flawlessly on all four of its missions since 2013, but the liquid kerosene and liquid oxygen-powered AJ-26’s had failed in testing, twice, since 2011, with the most recent failure having caused an engine slated to fly in 2015 to disintegrate on the test stand at Stennis Space Center last spring.

The search for a different engine has been ongoing for several years, but the final straw came with the total loss of the Orb-3 mission, which was witnessed by millions of people—both in person and on live broadcast. In the imagery of the liftoff it was clear immediately that a problem occurred with an engine, and it didn’t take long for Orbital to announce their intention to discontinue use of the AJ-26 in the days following the accident, citing preliminary evidence and analysis which strongly suggested a probable turbopump-related failure in one of the two AJ-26 engines.

Antares ORB-2 on the pad prior to launch. Photo Credit: John Studwell / AmericaSpace
Antares ORB-2 on the pad prior to launch. Photo Credit: John Studwell / AmericaSpace

This week, the Dulles, Va.-based company confirmed a new deal to employ Russian-made RD-181 engines to replace the AJ-26 for all future Antares flights, the first of which is expected to fly again from the Mid-Atlantic Regional Spaceport (MARS) at NASA’s Wallops Flight Facility in Virginia as soon as early 2016.

The news, which was released publicly this week in a story published by Frank Morring, Jr. at Aviation Week & Space Technology, was confirmed by Orbital on the company’s Twitter page on Dec. 16:

RD-181 engine meets schedule and technical requirements. No other options do,” said the company in their statement confirming the Aviation Week article detailing the news. “First deliveries of the newly-built RD-181 engines in mid-2015 to be ready for next Antares flight in early 2016. Newly-built RD-181 is only propulsion option that enables us to complete cargo commitments to NASA under CRS contract by end of 2016.”

That commitment calls on Orbital to fulfill a $1.9 billion Commercial Resupply Services (CRS) contract with NASA, signed in December 2008, which requires Orbital to fly eight dedicated Cygnus flights to the ISS by 2016 to deliver a total of 44,000 pounds of payloads and other items for the space agency.

However, the need for eight flights no longer holds true. Recently, Orbital struck a deal with United Launch Alliance (ULA) to fly their next Cygnus NASA CRS flight (Orb-4) on a ULA Atlas-V 401 rocket while the new Antares/RD-181 system becomes a reality. The combination of using the more powerful Atlas-V 401 (35 percent more cargo) and upgraded Antares in 2016 (20 percent more cargo for three flights: Orb 5, Orb-6, and Orb-7) eliminates the need for an eighth ISS CRS flight under Orbital’s CRS contract with NASA, which keeps the company on schedule and prevents any material adverse financial impacts in 2015 (or future years) as Orbital carries out their $1.9 billion CRS commitment and Antares propulsion upgrade programs.

The Russian-made RD-180 engine ULA currently uses on their proven Atlas-V rockets were an obvious alternative, but ULA holds exclusive rights in the U.S. to buy the RD-180 and has a reputation for anti-competitive practices. Orbital’s previous requests for support from the Air Force, Office of the Secretary of Defense and Congress, were all met with roadblocks and silence as well, and other possible AJ-26 alternatives (such as the RD-191 and RD-193) were either still in development or not yet approved for export (the RD-191 is being developed for Russia’s Angara rocket).

Antares and its former AJ-26 engines. File Photo, Credit: Orbital Sciences Corporation
Antares and its former AJ-26 engines. File Photo, Credit: Orbital Sciences Corporation

The RD-181’s have seen more than two times the Antares flight duration to date,” said Mark Pieczynski, Orbital’s vice president for space launch strategic development. “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. It allows us to keep the core nearly identical.”

We evaluated several alternatives, really all available alternatives both foreign and domestic,” added Ron Grabe, executive vice president and general manager of Orbital’s Launch Systems Group, in comments to Aviation Week. “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.”

Antares seconds after exploding on the Orb-3 launch. Photo: Elliot Severn / Zero-G News
Antares seconds after exploding on the Orb-3 launch. Photo: Elliot Severn / Zero-G News

The new Antares RD-181 engines will be manufactured and supplied by NPO Energomash, a corporation owned and controlled by the Russian Government who is also behind ULA’s Atlas-V RD-180 engine. According to Pieczynski, Orbital will receive two sets (pairs) of RD-181 engines in 2015. The first set, which is expected to arrive on Orbital’s doorstep next summer, will be integrated with an Antares booster core and strapped down on MARS launch pad 0A for a static test fire next fall to validate the new Antares/RD-181 system. When flown, at least for the first few launches, the engines will not out-perform the AJ-26, not until Orbital can make the necessary modifications to Antares to survive the increased performance capability of the RD-181 (100,000 pounds more thrust than the previous AJ-26 powered Antares).

A second set of RD-181 engines will be delivered next fall, and Orbital’s RD-181 contract with Energomash calls for up to five RD-181 engine sets per year (10 engines). The total number of engines ordered, and the costs for such a deal, have not been disclosed by Orbital, but reports from other sources have stated a firm order of 20 engines (two years of engines at five sets per year), with two contract options available for 20 more engines each if needed (potential to order 60 total engines over the next six years).

Our contract with Energomash covers our obligations under the current CRS contract, and hopefully anticipating an award for the next phase,” added Grabe in comments to Aviation Week. “Beyond that, we have options that, if exercised, would satisfy our requirements out beyond 2020.”

Elon Musk and his SpaceX publicly slammed ULA earlier this year for their use of Russian RD-180 engines because SpaceX could not compete against ULA’s controversial block-buy deal, citing Russia’s de facto annexation of the Ukraine’s Crimea region and the formal severing of military ties as potentially causing problems to America’s ability to launch national security payloads should U.S./Russian relations deteriorate. The powers that be in the federal government and U.S. Congress took notice, asking why our nation’s most secretive and important national security satellites were so dependent on Russian engines to reach orbit (ULA’s Atlas-V is the workhorse launch vehicle for the Dept. of Defense). The concern led to restrictions in the FY2015 National Defense Authorization Act (NDAA) for using Russian-made engines for U.S. national security payloads, such as completely banning ULA’s use of any RD-180 engines purchased after Feb. 1, 2014, but Orbital’s requirement for a Russian engine are civil space related, not national security related, and so the new NDAA restrictions—which apply to the Evolved Expendable Launch Vehicle (EELV) program—do not apply to Orbital’s contract for the RD-181 (Antares is not classified as EELV).


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  1. SIGH!!! I guess the people in charge at OSC haven’t learned a thing from ULA’s recent experience with the threats to the supply of RD-180 engines for the Atlas V. How long until the next international crises involving Russia threatens OSC’s supply of RD-181 engines for the Antares?

    • Considering OSC doesn’t launch military/NRO satellites, I’m not sure Putin gets much of anything out of playing the same game that he did with ULA.

      • It is NOT Putin stopping the supply of RD-181s for Antares that is the concern. It is the US government banning their import as part of sanctions in response to some future incident with the Russians that is the problem.

        • That’s probably not really that big of an issue. The sanctions now (and likely future) don’t prohibit procurement for military use, or support of US personnel on the ISS. State Department clarified that and that’s why the injunction against purchase that came as part of the SpaceX EELV suit was dropped.

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