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XCALIBUR: A Vertical Takeoff TSTO RLV concept with a HEDM Upperstage and a Scram-Rocket Boosterarge
John E. Bradford, A.C. Charania, John R. Olds, and Matthew Graham
October 19, 2002
Abstract
A new 3rd generation, two-stage-to-orbit (TSTO) reusable launch vehicle (RLV) has been designed. The Xcalibur concept represents a novel approach due to its integration method for the upperstage element of the system. The vertical-takeoff booster, which is powered by rocket-based combined-cycle (RBCC) engines, carries the upperstage internally in the aft section of the airframe to a Mach 15.5 staging condition. The upperstage is released from the booster and carries the 20 Klbs of payload to low earth orbit (LEO) using its high energy density matter (HEDM) propulsion system. The booster element is capable of returning to the original launch site in a ramjet-cruise propulsion mode. Both the booster and the upperstage utilize advanced technologies including: graphite-epoxy tanks, metal-matrix composites, UHTC TPS materials, electro-mechanical actuators (EMAs), and lightweight subsystems (avionics, power distribution, etc.).
Details of the concept design including external and internal configuration, mass properties, engine performance, trajectory analysis, aeroheating results, and economics assessment are given. Highlights of the distributed, collaborative design approach, analysis tools, and a summary of the payload trade study results are also provided.
Introduction
NASA Marshall Space Flight Center’s Advanced Space Transportation Program (ASTP) is currently conducting a number of system analysis studies focused on a variety of combined-cycle propulsion system options for use on future (2020+) reusable launch vehicles1,2. One specific option currently under consideration is the rocket-based combined cycle (RBCC) engine. These multi-mode engines combine the best aspects of rocket propulsion (high thrust-toweight)and airbreathing propulsion (high specific impulse). Previous research has shown that vehicles utilizing RBCC propulsion are attractive candidates for future space access due to the variety of missions and markets they can support (ETO payload delivery, military global reach, space tourism, etc.).
While a number of conceptual design organizations have focused their research on single-stage and twostage, horizontal takeoff machines, there appear to be very few studies examining a two-stage vertical takeoff with horizontal landing system utilizing RBCC engines. This is most likely attributable to the difficulties of arranging the two vehicles vertically into the airframe/propulsion integrated configuration required for hypersonic air-breathing propulsion operation.
With this clearly identifiable unexplored region of the design space, SpaceWorks Engineering, Inc. (SEI) was tasked by the Advanced Concepts Division (TD30) at NASA MSFC to undertake the conceptual-level vehicle study of a two-stage vertical 3rd Gen RLV using RBCC propulsion on the booster stage. The Xcalibur concept was thus created and designed by SEI and represents a potentially feasible 3rd Gen RLV concept in this undeveloped region of the design space.
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