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To effectively design an operable reusable launch vehicle propulsion system a baseline operations model and supporting historical data are required. There are traditional problems with the definition of baseline systems for aerospace launch vehicle operations analyses. In this paper, these problems are discussed and an overall approach for establishing a detailed baseline ground operations model is presented. The SSME is used as the source of historical reusable engine systems operations experience. The approach demands the identification of the requirements for SSME ground operations and the root source of the requirements. From this, an RLV engine model is developed that is based on the baseline SSME operations model. This is done through incremental modification of the baseline operations model based on the proposed changes from the baseline SSME to the RLV engine. The modifications of the baseline processing activities are based on changes in hardware configuration and technology, processing technology improvements, and operations philosophy. The RLV engine system model is then traceable to past requirements and historical experience. This modeling approach supports credible operations modeling and analysis. In this paper, the baseline SSME model and a demonstration of its utility is presented. Modification of the baseline model will be based on three hypothetical changes that are potential candidates for use on an RLV engine system. Copyright © 1996 by the American Institute of Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S. code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for government purposes. All other rights are reserved by the copyright owner. NOMENCLATURE EMA electro-mechanical actuator HEX heat exchanger HMS health monitoring system HPFTP high pressure fuel turbopump HPOTP high pressure oxidizer turbopump KSC Kennedy Space Center LH2 liquid hydrogen LO2 Equid oxygen LPFTP low pressure fuel turbopump LPOTP low pressure oxidizer turbopump MCC main combustion chamber MPS main propulsion system OMEF orbiter main engine facility OMI operations & maintenance instructions OMRSD operations & maintenance requirements & specifications document OPAD optical plume anomaly detection OPF orbiter processing facility R&R removal and replacement PR problem report PRACA problem reporting & corrective action database QC quality control RLV reusable launch vehicle SSME space shuttle main engine STS space transportation system

Developing a mission planning system for a Space Shuttle mission is a complex procedure. Several months of preparation are required to develop a plan that optimizes science return during the short operations time frame. Further complicating the scenario is the necessity to schedule around crew activities and other payloads which share Orbiter resources. SpaceTec, Inc. developed the mission planning system for the Lidar In Space Technology Experiment, or LITE, which flew on Space Shuttle mission STS-64 in September of 1994. SpaceTec used a combination of off-th-shelf and in-house developed software to analyze various mission scenarios both premission and real-time during the flight. From this analysis, SpaceTec developed a comprehensive mission plan that met the mission objectives.

The paper describes a lunar transportation system (LTS) based on a minimum cost approach to the lunar exploration scenario. A three-part exercise was conducted to minimize the cost and risk of lunar exploration, and the results of these optimization studies are presented. Particular consideration is given to the proposed concepts for the translunar injection stages, the common crew module of the LTS, the lander configuration, the LTS performance, and a concept of a long-range rover ('Rover First ') for discovering and mapping lunar resources for future utilization.

The Space Station Freedom program and the process used to develop an assembly sequence are overviewed, with special attention given to the outcome of the recent restructuring activity and the positive impact it had on the Space Station design and the assembly sequence. The many technically complex and challenging aspects of the assembly sequence planning are examined, including the launch vehicle integration, the spacecraft systems capability development, and the availability of resources. It is shown that the restructuring reduced the size and the complexity of the Space Station, while the increase of ground integration through the use of preintegrated truss and shortened modules offers a reduced program risk and reduced demands on the STS.

The paper discusses the primary objective of the NASA-OAST earth-to-orbit (ETO) propulsion technology program, namely, to completely overhaul the nation's liquid rocket design and analysis capabilities which were found to be severely limited when used for the design and development of the Space Shuttle Main Engine (SSME). Meeting this objective is to provide a much sounder, very comprehensive technology base that will enable the cost-effective low-risk development, acquisition, and operation of high-performance, expendable, or reusable ETO propulsion systems. This in turn will enable the future development of space transportation system launch vehicles with greatly reduced life-cycle costs. Work is carried out in three major areas: combustion devices, turbomachinery, and controls and health management.

Spacelab is a series of multiple configuration payload carriers that fit in the Orbiter cargo bay. The carriers, ranging from pressurized modules to simple support structures that span across the cargo bay, provide a variety of payload support services, such as cooling, power distribution, data management, pointing, and structural attachment. Previously published papers have addressed the joint development of the initial Spacelab system by the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). Herein, the emphasis will be on the NASA utilization and evaluation of the system into the operational era of the Space Transportation System (STS), system enhancement, additional carrier configuration, the effects of time on system hardware, and subsequent replacements and improvement. All configurations added were intended to fulfill payload requirements not originally foreseen. Subsystem replacements thus far have resulted from life limits or unreliable performance while assessments and plans are underway to look also for increased performance and new payload requirements, to the transition from Spacelab to the Space Station Freedom.

The paper discusses the constraints on a production process imposed by the lunar or Martian environment on the space transportation system. A proposed chemical route to produce oxygen from iron oxide bearing minerals (including ilmenite) is presented in three different configurations which vary in complexity. A design for thermal energy storage is presented that could both provide power during the lunar night and act as a blast protection barrier for the outpost. A process to release carbon from the lunar regolith as methane is proposed, capitalizing on the greater abundance and favorable physical properties of methane relative to hydrogen to benefit the entire system.

NASA has studied future missions to the moon and Mars since the 1960's, and most recently during the studies for the Space Exploration Initiative chartered by President Bush. With these most recent studies, the Lunar and Mars Exploration Program Office is looking at a number of possible options for the human exploration of the solar system. Objectives of these options include science and exploration, testing and learning centers, local planetary resource development, and self sufficient bases. To meet the objectives of any particular mission, efforts have focused primarily in three areas: (1) space transportation vehicles, (2) the associated space infrastructure to support these vehicles, and (3) the necessary infrastructure on the planet surface to carry out the mission objectives. This paper looks at work done by the Planet Surface Systems Office at JSC in the third area, and presents an overview of the approach to determining appropriate equipment and elements of the surface infrastructure needed for these mission alternatives. It describes the process of deriving appropriate surface architectures with consideration of mission objectives leading to system concepts, designation of elements and element placement.

A robust earth-to-orbit (ETO) transportation system, designed to facilitate the continuing human exploration of space, is discussed. The concept stresses larger lift capability and minimized on-orbit operations, of which the assembly and refueling operations are given priority. The modularity of the system is based on the required compatibility with the Space Shuttle vehicle, and it offers resiliency and reduced development costs. The support of lunar and Mars missions is interrelated with the mission logistics, the design of a transfer vehicle, the extent of reusability, and the required on-orbit operations. The transfer systems, the magnitude and frequency of propellant deliveries, and some human transportation requirements are considered with respect to vehicle concepts and flight rate strategies.

The development of an evolutionary approach to a space transportation system to meet the needs of the Space Exploration Initiative and other earth orbital and planetary missions is discussed. Common architectures, a building block approach to space transportation elements, the development of alternative technologies are considered as essential steps to arriving at an integrated space transportation system. These aspects are addressed as they apply to both lunar and Mars technology.

The results of an analysis of several reboost scenarios for nominal and contingency SS operations during the Phase I assembly sequence are presented. Space Station program requirements on assembly and operational altitudes are outlined, and essential features of the SS reaction control system are described. A nominal reboost strategy designed to meet the current program requirements is presented. In addition, reboost strategies are developed for several contingency scenarios, including one missed STS mission, and an extended STS outage. It is shown that the time-averaged propellant 'cost' of maintaining altitude is greatest for equivalent continuous-thrusting altitude maintenance; it decreases with increasing reboost/rendezvous time interval to an asymptotic minimum value.