U.S.A.F Plans Reusable Booster Demonstrators

Aviation Week and Space Technology ^ | 4/10/2010 | By Graham Warwick

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series of demonstrators is being planned by the U.S. Air Force to mature technology for the Reusable Booster System (RBS), its chosen replacement for the Evolved Expendable Launch Vehicle (EELV) family beyond 2025.

The first of the demonstrators, the Air Force Research Laboratory’s (AFRL) RBS Pathfinder, is planned to fly in 2013 to evaluate the “rocket-back” maneuver that would enable the unmanned first-stage booster to return to a runway landing at the launch site.

An RBS architecture combining a reusable first stage and expendable upper-stage stack is defined in the new spacelift development plan now in the final stages of coordination within the Air Force, according to Ken Hampsten, chief of spacelift for the Space and Missile Systems Center’s developmental planning directorate, SMC/XR. The plan should be with Air Force Space Command “within the next month or so,” he says.

The spacelift plan calls for development of two versions of the RBS: one with a single reusable first stage and cryogenic upper stage for medium-lift missions; and one with two reusable boosters, cryogenic core stage and upper stage for heavy-lift and growth missions. Initial operational capability is planned for 2025, with the EELV to be phased out in 2030, Hampsten says.

The RBS is expected to reduce launch costs by at least 50% at a nominal flight rate of eight a year, he says. Engines would be used for 10 flights before replacement and the reusable airframe for 100 fights.

Extensive studies identified rocket-back as the most promising return-to-base maneuver for the reusable first stage, says Jeff Slaber, AFRL’s Pathfinder program manager. Unpowered glide-back and turbine-powered jet-back maneuvers have been studied, but rocket-back allows a higher staging velocity — Mach 5-7 compared to Mach 3.5 for glide-back — and reduces the size of the upper stage, he says.

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One of the original Space Shuttle designs used a “flyback’ booster, although it was manned, not unmanned.