Before the dust settles from the post-shuttle shift in human access to space, the U.S. could find itself with a big new high-performance hydrocarbon rocket engine to boost NASA's planned heavy-lift Space Launch System (SLS) off the pad. There is a chance it might even replace the Russian-built RD-180 that carries the United Launch Alliance Atlas V.

A dual-use rocket burning refined petroleum-1 (RP-1), a form of kerosene, instead of liquid hydrogen or solid fuel, might hit the sweet spot in next-generation U.S. space launch needs. It could give NASA enough thrust to build its congressionally mandated 130-metric-ton heavy lifter, while removing Russia from the critical path to launching sensitive national security payloads.

“We know the [Defense Department] is interested,” says Dale Thomas, associate director-technical, at NASA's Marshall Space Flight Center. “They are a little apprehensive about using a foreign-sourced engine on a strategic capability for our nation.”

Thomas helped set up the National Institute for Rocket Propulsion Systems (Nirps) at Marshall to find ways to strengthen the U.S. industrial base in the field. One of the Nirps projects is finding “intersecting interests” for collaboration in rocket propulsion, and large hydrocarbon engines may fill the bill.

“We have to have higher lift capabilities out of the Space Launch System, and it turns out one of the options we are looking at is RP-based engines, which potentially intersect with the core-stage engine for the Atlas V,” Thomas told the Fifth Von Braun Memorial Symposium in Huntsville, Ala., this month.

NASA is in talks with the Air Force about joining the Hydrocarbon Boost Technology Demonstrator program, a relatively low-level Air Force Research Laboratory (AFRL) effort to develop advanced kerosene rocket technology. Among the AFRL contractors on the program is Aerojet, which is developing a 1-million-lb.-thrust, LOX-rich staged combustion kerosene-fueled engine designated the AJ-1E6 that could fill the civil and military roles, according to Julie Van Kleeck, the company's vice president of space and launch systems.

NASA is negotiating with Aerojet to bring the AJ-1E6 into the mix of potential powerplants for the advanced boosters it must develop to raise the SLS from its 70-metric-ton initial capability to the 130 metric tons Congress ordered (AW&ST Oct. 22, p. 34). The talks are complicated by the need for agreement among the Air Force, NASA and the company on how best to proceed, according to Rex Geveden, president of Teledyne Brown Engineering, a Huntsville-based supplier that has an agreement with Aerojet to manufacture components for the new engine.

“There is more complexity in this one because there are multiple players,” says Geveden, a former associate administrator of NASA, stressing that his company is not involved in the talks directly. “There is some potential Air Force funding and some things like that going on that make this at least a three-party discussion.”

NASA has already awarded Dynetics Inc. of Huntsville a $73.3 million study contract to demonstrate components of an Apollo-era F-1 kerosene main engine, updated with modern manufacturing techniques, as the engine for the advanced boosters, as well as a separate contract with ATK on new versions of the solid-fuel boosters that launched shuttles into space, and with other companies for technology that could help provide the needed extra lift for SLS.

According to a paper presented at the recent 63rd International Astronautical Congress in Naples, Italy, an upgraded F-1 would provide more than enough capability for the SLS application, and could power other vehicles that might even serve as a U.S.-powered replacement for the Atlas V.

Lead author Steve Cook, director of space technologies at Dynetics, wrote: “The high-cost, non-recurring engineering typical of engine development was accomplished during the Apollo-Saturn program, eliminating significant risks (e.g., turbopump design and combustion stability). This permits the current focus to be on affordability rather than technical feasibility.”

In the Dynetics concept, two of the F-1 engines originally developed for the Saturn V first stage would drive twin strap-on 18-ft.-dia. SLS boosters, using shuttle-heritage attach struts and other hardware to save more on development. The engines would use vintage-design F-1 valves and injectors, and simplified F-1A turbomachinery, with modern Hot-Isostatic Press (HIP)-bond construction for the channel wall main combustion chamber, and a channel wall nozzle (see illustration).

The F-1 remains the most powerful U.S. liquid-propellant rocket engine ever built, and with the proposed modifications it would deliver as much as 1.8 million lb. thrust at sea level, throttlable back to 1.3 million lb. thrust, according to Cook's paper. If used on the early version of the SLS, without the planned upper stage powered by the J-2X version of the Saturn J-2 upper-stage engine, it would be able to generate 105-metric-ton capability, Cook and his coauthors wrote.

Dynetics has teamed with Pratt & Whitney Rocketdyne (PWR), which built the original F-1 and J-2, and is developing the J-2X. Although Aerojet is in the process of acquiring Rocketdyne, the two companies remain competitors for now with their different approaches to the SLS booster engines, according to PWR President Jim Maser.

A significant difference between the modernized F-1 and the AJ-1E6—itself a modernized version of the Russian NK-33 engine Aerojet acquired to power the Orbital Sciences Corp. Antares launch vehicle—is the engine cycle. While the F-1 is a gas generator, which vents part of its propellant over the side after using it to turn the turbomachinery, the AJ-1EJ is a closed-cycle staged combustion engine that burns all of the propellant. Aerojet argues that the closed cycle makes its engine more efficient, while Dynetics says the gas generator's lower operating pressures allow the use of less expensive materials and components.

Before joining Dynetics, Cook was program manager for the Ares I crew launch vehicle that was canceled along with the rest of the Constellation program of shuttle-replacement human-rated vehicles. While the F-1 upgrade is not intended to power the Atlas V, a “single-stick” configuration using one F-1-powered booster and an upper stage, just as the Ares I used a shuttle-derived solid-fuel first stage, could more than match the Atlas V lift capability.

“The F-1 is not a plug and play for an RD-180 on an Atlas V,” Cook says. “However, our dual-engine booster, combined with an upper stage, can deliver over 30 metric tons to orbit—a single-stick version of an EELV–heavy.”

The former NASA engineer argues that the F-1 modification is aimed at affordability, since the capability is already inherent in the design. Under its 30-month advanced-booster study contract, Dynetics and Rocketdyne plan to hot-fire-test the modern F-1 powerpack at Stennis Space Center to demonstrate its performance and reduce risk.

“Think booster versus engine application,” Cook says in an e-mail. “We are engaging the larger space launch community (e.g., commercial, Defense Department) about applications beyond SLS and we have had interest from several parties. When you plan to hot-fire the key components of the largest engine ever built in the U.S., people get pretty interested.”