Reusable Booster System

The Reusable Booster System (RBS) was a United States Air Force research program, circa 2010 to 2012, to develop a new prototype vertical-takeoff, horizontal-landing (VTHL) reusable booster and a new prototype expendable second stage to replace the existing Evolved Expendable Launch Vehicles (EELV) after 2025. The program was discontinued in 2012.

History
Program funding was initially set at US$250000000. "Officials anticipate awarding up to three contracts for the project, where winners would compete for individual tasks of experiments and demonstrations that address technology, processes and other attributes of a reusable booster system, or RBS." The proposal deadline was 19 March 2011. The Air Force had developed a notional plan to build a fleet of eight of the RBS systems, to be flown from both Vandenberg Air Force Base in California and Cape Canaveral Air Force Station in Florida.

In December of 2011, Lockheed Martin was awarded a contract to build a flight demonstration vehicle, the RBS Pathfinder, which was to have been completed in 2015. It was being developed under the Air Force Research Laboratory's (AFRL) RBS Flight and Ground Experiments (RBS-FGE) program.

In 2012, Lockheed began initial rocket tests.

The program was discontinued in October 2012, citing DoD funding reductions and an October 2012 negative report by the National Research Council (NRC), after having expended only a small fraction of the original $250 million budget planned to be spent through 2019.

Among other factors, the October 2012 NRC report suggested that the Air Force "should develop and fly more than one Pathfinder test vehicle design [and that] competition amongst RBS concepts should be maintained as long as possible to obtain the best system for the next generation of space launch."

Propulsion
A large-liquid-engine group comprising the Air Force Space Command, propulsion researchers from AFRL and SMC's launch systems program office is also meeting to discuss engine options. The group will consider whether to focus on developing oxygen-rich, staged combustion (ORSC) engines like the Air Force's long-running Hydrocarbon Boost program, use an existing design like the TR-107 or evolve a newer engine such as Pratt & Whitney Rocketdyne's J-2X or RL60. Whatever path is chosen would result in building an engine capable of roughly 250,000 lb. thrust by 2020.