The application of large scale hybrids to NLS and future personnel launch vehicles

Abstract

Two new space transportation concepts are being investigated in the United States. One, the National Launch System (NLS), is designed t o launch unmanned payloads. Another, the Personnel Launch System (PLS), is a small spacecraft designed exclusively for personnel transport. Consideration is being given t o launching the PLS using an element of the NLS booster. Because o f the demanding requirements for crew safety and safe return after abort, the PLS may be better served by a launcher optimized for crew safety, leaving the NLS t o be optimized for its unmanned cargo carrying role. The unique safety characteristics of hybrid propulsion could be ~ invaluable in this manned launch role. This paper reviews the characteristics of hybrid propulsion as they apply t o the PLS mission, and describes the features of an example hybrid PLS launcher. The paper suggests that booster elements of this hybrid PLS launcher could be used t o augment NLS core performance for missions that require heavier payloads. lntroductim The United States is currently planning a new generation of launch vehicles t o support the needs of future national space programs. These launchers will operate more economically and reliably than current systems, and serve both manned and unmanned space transportation missions. In addition, they should be less damaging to the environment than current systems, and more resilient t o failure-driven stand-downs in order to assure routine access to space. The principal candidate for unmanned cargo transport missions is the National Launch System (NLS). The NLS is a family of boosters that can be assembled from common components. Depending on which configuration is assembled, it can lift from 20,000 LB t o over 100,000 LB into low earth orbit. Recently the National Research Council (NRC) has recommended that development be focused on the 20,000 LB payload class NLS-3 vehicle because ... it is the least complex and least expensive of the NLS family and the one most likely t o have possible commercial, as well as national security applications.' Projected traffic models indicate this size booster will have the highest planned flight rate and will carry the majority of foreseen traffic growth. When programs requiring more performance mature, the NLS-3 can serve as a core vehicle that can be augmented by strapon boosters t o carry heavier payloads. A leading option for a new manned transport is the Personnel Launch System (PLS). It is designed to launch a small crewed spacecraft and will be used primarily for transport of personnel t o and from earth orbit. The PLS spacecraft is currently planned t o weight approximately 25,000 LB on orbit. Its small size and independence from cargo handling requirements will lead t o reduced operating costs for manned missions. The launch vehicle used for lifting the PLS must offer a safe abort capability during all stages of operation. Because the desired throw weight of the PLS launcher and NLS-3 are similar, consideration is being given t o configuring the NLS-3 core for both manned and unmanned rolls. Although these systems have similar payload l i f t requirements, they have exclusive design requirements. The NLS-3 is designed t o serve