Masters Theses

Date of Award

8-2002

Degree Type

Thesis

Degree Name

Master of Science

Major

Aerospace Engineering

Major Professor

Gary Flandro

Abstract

Throughout the architecture definition and risk reduction phase of the Second Generation Reusable Launch Vehicle (2GRL V) Program, the National Aeronautics and Space Administration (NASA) is faced with refining their requirements for human space transportation. Design Reference Missions defined during the Space Transportation Architecture Studies (ST AS) asked for Space Shuttle-like capabilities with improved safety and lower costs. If a crewed Space Transport (ST) is designed to meet NASA's crewed space flight needs, it has the potential to drive the rated lift of a Second Generation Reusable Launch System. In order to reach a 2GRL V Full Scale Development decision by mid-decade, NASA must fully understand how their unique requirements affect the entire space transportation system. The capability to perform ST trade studies quickly can show the cost (in weight) of NASA-unique requirements and technologies, allowing NASA to make a more informed decision earlier. The Lockheed Martin Space Transport Weights & Sizing Tool provides this capability. The Tool is a parametric model that predicts ST size and weight for specified requirements (crew number, mission duration, OMS delta-v, payload weight, etc.) and configuration choices (fuselage diameter, propellants, system redundancy and more). It enables trade studies on total vehicle functionality as well as subsystem details. Improvements have been made to this Tool over that past ten months, increasing its utility even further. Configuration choices have been added that allow the user look beyond the way in which missions are performed today. These improvements also improve the fidelity of the Tool, making the predictions more viable. A number of trend lines have been plotted to show the effects of variations in the inputs described above. Though these trends are largely based on a Shuttle-heritage system, some basic rules of thumb for ST growth can be concluded. ST Gross Lift-Off Weight (GLOW) for this type of system increases ~ 2.5 lb per pound of Unpressurized Cargo. Increases in GLOW due to additional OMS delta-v can be predicted based on propellant choice. Vehicle growth attributed to increases in steady state power requirements, mission duration and system redundancy have also been explored. The ability to quickly assess the size and weights for Space Transports of various configuration choices and requirements allows the user to generate a pool of possible vehicles on which to perform functional trade studies. These trades can help NASA better understand the cost of specific requirements.

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