The design of lunar and Mars transportation systems utilizing extra-terrestrial resources

Abstract

This paper investigates means for optimizing the design of a space transportation architecture which incorporates the use of extra-terrestrial materials for propellant production. In has been shown by many authors that the use of in situ propellant production (ISPP) at a destination planetary body may offer large benefits for missions, when compared with the same missions carried out using propellants or terrestrial origin. However, it has generally been the case that such mission trade studies do not seek to optimize the transportation architecture to the use of ISPP. Instead, such studies have employed transportation architectures whose designs were based upon the assumption of all-terrestrial propellants, and ISPP is thrown in as an afterthought. This method of analysis is defective because the introduction of ISPP completely changes the optimum form of the space transportation system itself. For example, it has been accepted since the Apollo missions that lunar orbit rendezvous (LOR), while having operational disadvantages compared to a direct return (DR) from the surface stategy, is far more efficient on a mass basis and therefore is the proper way to carry out a manned lunar mission. However, once lunar LOX is available, this is no longer true, and DR becomes more mass efficient than LOR. Furthermore, the required size and capability of the booster and all the stages required to perform a lunar mission under condition of availability of lunar LOX is radically different than if only terrestrial propellants are used. Thus Lunar LOX changes both the form and the required scale of a lunar transportation architecture. The alterations of the form, scale and even the technological basis of manned Mars missions under conditions of optimized utilization of ISPP are even more dramatic. As the non-availability of ISPP can be made a transitory condition applying only to a small (or non-existent) set of initial missions, designing a space transportation architecture optimized for terrestrial propellants, but far off optimum for the recurring mission utilizing ISPP, may be a very big mistake. This paper discusses space transportation systems that have been optimized for use in conjunction with in situ produced propellants. It is shown that by using such systems right from the start of the lunar/Mars program, flight system development costs can be reduced by about an order of magnitude compared with those required for creating a transportation system that only utilizes terrestrial propellants. In addition, the use of in situ produced propellants can cut ongoing operations costs by a factor of 2 to 3, and makes possible simpler and safer mission modes.