Development of the U.S. Air Force's proposed next-generation upper-stage engine is vital to inject new life into the industry, even though the operational requirement remains obscure, say supporters.

The Air Force Space and Missile Systems Center issued a request for information in 2010 for a next-generation engine (NGE) to replace the Pratt & Whitney Rocketdyne (PWR) RL10 by 2017. The effort was launched amid concerns that the venerable engine is reaching its design limits and costing more as PWR's customer base shrinks with the retirement of the space shuttle. Two variants of the RL10 power the upper stages of the Air Force's Atlas V and Delta IV Evolved Expendable Launch Vehicles (EELV).

The Air Force plans to continue using the EELV family through 2030 and, according to the request for information, wants a new “upper-stage engine utilizing modern design and manufacturing methods . . . that will demonstrate state-of-the-art operating margin and reliability and minimize life-cycle costs.”

EELV operator United Launch Alliance has since embarked on a joint effort with XCOR Aerospace to develop a low-cost, flight-ready, liquid oxygen-liquid hydrogen, upper-stage engine, while PWR has outlined a road map for an all-new RLXX engine based on an evolution of the RL10. In the interim, PWR is also reworking the many excess RL10B-2 engines in the inventory into a new common RL10C variant that incorporates the best of the B-2 and RL10A-4 for use on the Atlas V.

Aerojet, the other main U.S. producer of liquid-fueled rocket engines, has meanwhile won a $7.5 million Air Force contract to add the NGE and “upper-stage technology options” to work it is doing to develop modeling and simulation tools for more efficient hydrogen-fueled engines. Tests of the company's advanced turbopump are also under way at Edwards AFB, Calif., as part of the Air Force's Upper Stage Engine Technology program.

Julie Van Kleeck, Aerojet vice president for space and launch systems, says the NGE initiative is vital not just for future EELV capability, but for the health of the entire U.S. rocket industry. “I'm sad that the U.S. has lost its position as a leader in commercial launch. We have a presence, but we're becoming unaffordable. We used to develop engines all the time, but we haven't done much for a while,” she says.

The NGE plan could inject new life into an industry suffering from years of cancelled projects, such as NASA's Constellation program, says Van Kleeck. “To sustain the industrial base, you have to have a full life cycle. We have to take these things all the way from development, and we're not doing that. Now's the perfect time to say, 'Let's do something different,' because if we continue in this mode we aren't going to do anything,” she adds.

Linda Cova, Aerojet executive director of pump-fed engine development, says that with the completion of the RL10C, “they need to restart production. So what we've been saying is, 'Do you want to restart an old line, or take that money and do a modern engine using modern manufacturing techniques?''' Cova adds, “We'd like an opportunity to compete.”

An all-new program would also help stimulate new interest in aerospace among today's engineering students, says Vigor Yang, a professor at the Georgia Institute of Technology's School of Aerospace Engineering. “U.S. rocket propulsion faces extinction because the numbers are so small, and there's no long-term commitment—that's pretty much the situation. The RL10 is a wonderful engine, but it doesn't inspire the next generation. That's why I'm a big fan of NGE. My job is to inspire the next generation and getting them inspired to work on the same engine their grandfathers developed 50 years ago is not easy!”

Yang and Van Kleeck also say the NGE should be executed in as short a time frame as possible. “Should we spend seven to eight years on the next engine? I don't believe the country needs to take that long—that's a business-as-usual approach,” says Yang, who warns that interest in the sector has waned so much among young people that only 2% of U.S. engineering students enter aerospace.

Van Kleeck adds that “if it takes eight to 10 years, it will cost billions. In the 1950s and 1960s, we could develop these in two to four years, and I'd argue that with advances in technology and tooling, and the type of workforce we have, I don't know why it should take seven years—I don't know why it should take three years, or even two. We're struggling financially, but I'd say we can't not afford to do this as a country.”

John (Chris) Andrews, ULA director for strategic planning and government relations, also believes the importance of the development is strategically greater than the sum of its parts. “We, as a spacefaring nation, really ought to have the capability to invest in these technologies, and yet in the past 15 years we've been measured and have been found wanting. Is there a compelling need for an NGE? Not really. But there is a compelling need that I have for something.”

The Air Force, meanwhile, echoes the view that the NGE forms more than just a pathway for its national security payload launch capability. EELV Chief Engineer Lt. Col. Tobin Cavallari says, “SpaceX has taken a good step in that direction with a young workforce, and we hope NGE is a potential path to do that and revitalize the workforce.” Additionally, Cavallari says the study will assist in assessing “where we are going as a country in liquid propulsion. What's beyond EELV? Certainly there are things beyond today, in five to 10 years, that we should be concerned about, and one is affordability. What things can you do to make launch vehicles as affordable as we can?”

Randolph Kendall, general manager of The Aerospace Corp's Launch Systems division, also believes the NGE offers a rare opportunity to help inject new energy into the sector. “There is not a lot of development activity sustaining the liquid-rocket industrial base, which has been reduced to a fairly small number of primes,” he says.

“But there is a bright spot,” adds Kendall. “There is a growing number of small companies serving the commercial space market.” To this view, SpaceX Propulsion Vice President Tom Mueller wholeheartedly agrees: “We're going to be making more than 400 engines per year. That's more than any other country in the world, including Russia. I don't see where it's dying. There's new energy that's started in commercial space.”