Air Force Eyes New Upper Stage Engine for Atlas V, Delta IV

United Launch Alliance's Delta IV Heavy.

U.S. Air Force Ponders New Upper-stage Rocket Engine
Space News

The U.S. Air Force is beginning to weigh options for developing a more capable and affordable upper-stage engine for the Atlas 5 and Delta 4 rockets the service uses to launch most national security payloads.

The Air Force Space and Missile Systems Center in Los Angeles is giving industry until Nov. 9 to submit ideas for building a next-generation upper-stage engine to replace by 2017 the two versions of the RL-10 engine Pratt & Whitney Rocketdyne builds for the Atlas 5 and Delta 4. A formal request for information the Air Force posted Sept. 27 on the Federal Business Opportunities website has garnered the attention of Pratt & Whitney Rocketdyne and its rival Aerojet, the other main U.S. producer of liquid-fueled rocket engines.

Originally developed under the Air Force’s Evolved Expendable Launch Vehicle (EELV) program as competing rockets, the Atlas 5 and Delta 4 are operated today by United Launch Alliance of Denver, a Boeing-Lockheed Martin joint venture. The rockets use slightly different versions of the liquid hydrogen-fueled RL-10 engine to power their upper stage. While the engine has evolved over the years, Pratt & Whitney Rocketdyne officials say engineers are reaching the limit of additional improvements that can be squeezed out of the 50-year-old engine design.

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