Due to “unexpected funding reductions,” the U.S. Air Force is discontinuing work on a prototype reusable rocket design effort that the U.S. National Research Council recently cited as a key steppingstone to an operational system.
The Air Force had budgeted $250 million through 2019 for the reusable booster system (RBS) Pathfinder program, intended to demonstrate a kerosene-fueled first stage that would fly back to its launch site after completing its mission. The Air Force Research Laboratory in December awarded RSB Pathfinder study contracts worth about $2 million apiece to Andrews Space of Seattle, Boeing Phantom Works of Huntington Beach, Calif., and Lockheed Martin Space Systems of Denver.
“Lockheed Martin, Andrews Space, and Boeing recently completed the technical period of the Phase I portion of the Pathfinder program and the contractual period of performance will end in December, 2012,” Ted Theopolous, a spokesman for the laboratory at Wright-Patterson Air Force Base, Ohio, said in an emailed response to Space News questions. “Due to unexpected reductions in program funding, [the Air Force Research Laboratory] does not plan to make any future contract awards related to the Pathfinder program.”
In a report released to media Oct. 15 that challenged the economic arguments for an operational RBS system as notionally planned by the Air Force, the National Research Council said the service should develop enabling technologies and concepts independently of whether it proceeds with a full-scale program. These include oxygen-rich staged-combustion hydrocarbon engines; operations of vehicles that return to the launch site; vehicle-health monitoring systems; and adaptive guidance and control, the report said.
The Pathfinder program was intended to demonstrate the return-to-launch-site operations scheme for the vehicle’s first stage.
“To increase the chances for Pathfinder’s success, [the Air Force Research Laboratory] should develop and fly more than one Pathfinder test vehicle design,” the report said. “In addition, competition amongst RBS concepts should be maintained as long as possible to obtain the best system for the next generation of space launch,” the report said.
As envisioned, the RBS features a reusable first stage powered by a liquid-kerosene-fueled engine and an expendable second stage fueled by liquid hydrogen. The vehicle would take off vertically and the first stage would, after releasing the second stage, return to the launch site and land horizontally.
The Air Force has notional plans for a fleet of eight such vehicles at Vandenberg Air Force Base, Calif., and Cape Canaveral Air Force Station, Fla., according to the report, “Reusable Booster System: Review and Assessment.” These plans were devised in response to a June 2011 Air Force Space Command vision document outlining strategies for maintaining U.S. dominance of space and cyberspace, the report said.
According to the Aerospace Corp., the Los Angeles-based not-for-profit company that performs engineering and other analyses in support of U.S. military space programs, developing and operating an eight-vehicle RBS fleet would provide significant long-term cost savings over the Evolved Expendable Launch Vehicle (EELV) program, which today launches the vast majority of U.S. military and intelligence satellites. But the National Research Council, tasked with conducting an independent analysis of the concept, said the business case for pursuing a large-scale RBS program is unclear.
The council’s expert panel questioned the RBS cost estimates, citing numerous uncertainties associated with reusable launch systems. While the estimates were based on industry-standard methodologies, they rely on historical data that do not draw on experience operating reusable launch systems, the report said.
The cost projections also assume the RBS’s first stage would utilize a U.S. variant of Russian hydrocarbon — or kerosene-fueled — engine technology, “but the cost risks associated with development of an operable engine are difficult to capture,” the report said. The first stage of the Atlas 5 rocket, one of two workhorses of the U.S. EELV fleet, is powered by the Russian-built RD-180 main engine, for which a U.S.-based production line was planned but never implemented.
Moreover, the report said, it is not clear what infrastructure would be needed to operate and maintain a fleet of RBSs, and therefore the costs associated with that requirement are uncertain.
The report also noted that the savings attributed to the RBS are based on current EELV program costs and do not account for the possibility of lower-priced competitors entering the market.
Denver-based United Launch Alliance, a Boeing-Lockheed Martin joint venture, has a virtual monopoly in the U.S. military market as prime contractor on the EELV program, whose costs have soared well beyond expectations for a variety of reasons. But Space Exploration Technologies Corp. of Hawthorne, Calif., is angling for that business with what it says will be lower-cost vehicles, and has several successful launches under its belt. Another company, Stratolaunch Systems of Huntsville, Ala., is developing a system that would launch rockets from an aircraft that incorporates components from a Boeing 747 jetliner.
“Given the significant number of commercial entities pursuing novel approaches to achieve launch capabilities, the future of space lift may look very different from those employed today,” the report said.