The HL-20 Lifting-Body Personnel Launch System 911970
For several years the NASA Langley Research Center has conducted in-depth research in supporting technology advancement for a concept which could complement the Space Shuttle operation and ensure the ability to transport people to and from earth orbit. The concept is called the HL-20 Lifting-Body and it has been defined as an option for future development as a Personnel Launch System (PLS). This paper will describe early lifting-body research, expected PLS mission requirements, the HL-20 concept design status, and those features which enhance aerodynamic and aerothermodynamic performance, operation efficiency, maintainability, reliability, and crew safety.
The HL-20 concept evolved from early lifting-body research in the 60's and 70's and has been designed for the primary mission of changing the Space Station Freedom crew. It is sized to accommodate eight passengers plus a flight crew of two. The duration of the mission is 3 days. About 29 ft in length, the vehicle has a landing weight of 22000 lb. It is launched vertically, mounted on an expendable or partially reusable booster and has a hypersonic lift-to-drag ratio of about 1.4 with an entry cross-range of 1100 nautical miles to provide flexibility in choice of landing sites for each orbit and in opportunities for landing. Landing is horizontal on runways 10000 feet or longer.
Considerable research effort has advanced the HL-20 to a fairly mature design. A broad range of wind tunnel testing has provided a substantial data base for understanding the aerothermodynamic performance and these tests have been complemented by numerous computational flow-field studies. Structural and subsystem design has focused on features which offer operational simplicity with low maintenance costs and rapid vehicle processing. Efficiency in operation is achieved through the use of airline approaches to overall system layout and access coupled with built-in test and health monitoring instrumentation. Computer-based flight simulations have involved experienced pilots and astronauts, and the HL-20 concept proved to be relatively easy to fly and to land. A full-scale model of the concept has been constructed with an interior for conducting crew accommodation studies, ingress and egress, pilot visibility, and other man machine interface investigations. Results of the HL-20 PLS research to date show that the concept has definite advantages for efficiently satisfying future needs for assured manned access to space. The vehicle is designed with operational efficiency, low life-cycle costs, reliability, and safety as the primary criteria. Should there be a decision to develop and operate the vehicle, it has been defined with a substantial technical foundation for reducing the risk of program success.