HL-20 Personnel Launch System - PLS Concept

PLS Concept

With increasing national interest in obtaining routine access to space, a number of Earth-to-orbit transportation systems were being studied in the mid-1980s. One, referred to as a Personnel Launch System (PLS), could utilize the HL-20 and an expendable launch system to provide manned access complementing the Space Shuttle. A full-size engineering research model of the HL-20 was constructed in 1990 by the students and faculty of North Carolina State University and North Carolina A & T University for studying crew seating arrangements, habitability, equipment layout and crew ingress and egress. This 29 feet (9 m) long engineering research model was used at Langley to define the full-scale external and internal definition of the HL-20 for utilization studies.

The PLS mission was to transport people and small amounts of cargo to and from low-Earth orbit, i.e., a small space taxi system. Although never approved for development, the PLS concept spaceplane was designed as a complement to the Space Shuttle and was being considered an addition to the manned launch capability of the United States for three main reasons:

• Assured manned access to space. In the era of Space Station Freedom and subsequent missions of the Space Exploration Initiative, it is imperative that the United States have an alternate means of getting people and valuable small cargo to low-Earth orbit and back should the Space Shuttle be unavailable.
• Enhanced crew safety. Unlike the Space Shuttle, the PLS would not have main propulsion engines or large payload bay. By removing large payload-carrying requirements from personnel delivery missions, the PLS would be a small, compact vehicle. It is then more feasible to design an abort capability to safely recover the crew during critical phases of the launch and return from orbit.
• Affordable costs. As a small vehicle designed with available technologies, the PLS is forecast to have a low development cost. Subsystem simplification and an aircraft approach to PLS ground and flight operations can also greatly lower the costs of operating PLS.

Two designs that were considered for PLS differed in their aerodynamic characteristics and mission capabilities:

• the Johnson Space Center's approach used a blunt cone shape (similar to the various Moon-mission return vehicles), incorporating a parachute system for coming to rest;
• the Langley Research Center proposed a lifting body that could make a conventional runway landing on return from orbit.