Reusable Launch Vehicle Tank/intertank Sizing Trade Study

A tank and intertank sizing tool that includes effects of major design drivers, and which allows parametric studies to be performed, has been developed and calibrated against independent repzresentative results. Although additional design features, such as bulkheads and field joints, are not currently included in the process, the improved level of fidelity has allowed parametric studies to be performed which have resulted in understanding of key tank and intertank design drivers, design sensitivities, and definition of preferred design spaces. The sizing results demonstrated that there were many interactions between the configuration parameters of internal/external payload, vehicle fineness ratio (half body angle), fuel arrangement (LOX-forward/LOX-aft), number of tanks, and tank shape/arrangement (number of lobes). INTRODUCTION AND TRADE STUDY OBJECTIVES Future launch vehicles must be lightweight, fully reusable and easily maintained if low-cost access to space is to be achieved. The X-33 Program is a joint venture between NASA and Lockheed Martin to develop the enabling technologies for such a vehicle with a goal of reducing the cost of placing payloads into orbit by an order of magnitude.1 The Lockheed Martin VentureStarTM, a proposed commercial Reusable Launch Vehicle (RLV) based on the X-33 configuration, is a lifting body with aerospike engines mounted aft (Figure 1). The goal of VentureStarTM is to establish a vehicle that meets targets for empty weight, payload to orbit, and stability through all flight regimes, while being economically viable. Currently, parametric weights are being used to assess the viability of configurations as changes are made to the vehicle Outer Mold Line (OML) and major changes are made in the vehicle structural arrangement. For example, the number of cryogenic tanks (as well as their shapes, sizes and packaging) vary widely between possible configurations, as does the location of the payload bay, connection of tanks through intertanks, and integration of tanks into the thrust structure. However, current parametric weights lack the fidelity to allow discrimination between different arrangements, configurations, sizes and geometries of major airframe structural components. They also offer no insight into defining either the major structural parameters driving a design, or sensitivity of a particular structural concept to its design drivers. As a result major perturbations have been made to the vehicle structure, and the erroneous result of no apparent impact on the vehicle total weight was obtained. 1 American Institute of Aeronautics and Astronautics Figure 1. Lifting body reusable launch vehicle