Evolutionary lunar systems for human exploration

v Mission and system concepts for minimum-development return to the Moon are reviewed. Performance and trades are presented for direct-mode missions, including matchups between Outpost surface payload and crew transport systems, storable and cryogenic crew return stages, space engine performance, and kerosene versus hydrogen boosters. Launch vehicle performance for lunar transfer is enhanced by suborbital staging. Equivalent launch to LEO payload capability needed ranges from 150 to 215 metric tons depending on technology level of the lunar transfer systems. It is shown that improvements in technology and performance, including lunar oxygen, reuse of lunar transfer elements. and electric propulsion, can be introduced in an evolutionary manner and offer major reductions in lunar transportation cost for extended lunar exploration and early steps to industrialization. Introduction and Background System concepts for return to the Moon have been studied periodically since Apollo. A complete concept was developed during the NASA “90-Day Study”,[Priest & Woodcock], representing integration of the besrdefinition of launch vehicle and inspace transportation capabilities available at that time, to serve the 90-Day Study lunar mission reU quirements. These requirements were relatively ambitious, leading to early delivery and installation of a sizable uermanent base with a substantial suite minimum modification; ( 5 ) Redundancy and safety for human-tended operations are provided by the crew transportation system which offers any time return to Earth, analogous to the Assured Crew Return Vehicle planned for Space Station Freedom; and (6) The lunar delivery mass of this initial Outpost is roughly commensurate with the lunar delivery mass of a direct return-to-Earth crew transportation system, suggesting a sim le implementation of initial of the Outpost and a single Earth launch for the crew. lunar missions by a sing Y e Earth launch for delivery of science,cbnstruction and operations equipment. Since the 90-Day Study, studies by NASA, Boeing, Manin-Marietta and others have identified a large number of innovative mission and vehicle modes for lunar transportation operations. Also, mission requirements have tended to become less demanding, especially for the initial return-to-the-Moon period. Current ideas suggest a 42-day man-tended surface mission as a reasonable initial capability. Four people, 42 days, on the first return to the Moon offers roughly an order of magnitude more lunar surface crew time than all of the Apollo missions combined. In particular, a concept for an “initial outpost”, a single-launch, turn-key, human-tended lunar surface habitat has evolved, deriving from several step. before a permanently occupied lunar base; (2) TIUS step should be emplaced on the Moon without benefit of construction operations and-a necessity for construction equipment; (3) Adequate radiation shielding for a 45 to 60-day stay can be built into a habitat module, obviating the need for regolith shielding emplacement;(4)ASpace Station Freedom habitat module seems suitable for the purpose with Also since the 90-Day Study, the National Launch System (NLS) program has taken shape, offering clear cost advantages to using an NLS-derived launch vehicle for return to theMoonrather than developing a special-purpose System. NLS as presently conceived is not large enough to serve the single-launch Outpost mission. A heavy-lift derivative is needed, or multiple launches and Earth orbit operations to assemble the lunar transportation system must be accepted. Earth orbit operations for initial lunar return are undesirable since “requirements” on the operations will tend to proliferate and these operations will become ends in theaselves, diverting resources and emphasis From the real objective of renUning to the Moon. Since the NLS is presently in a preliminary design hase, clear definition of a timely and useful guidance to NLS system evolution requiremmts. A recent proposal by Nu Davis for a multiplelaunch return to the Moon uses only existing Earth to orbit transportation and extensive Earth orbit operations to assemble the lunar vehicle. If only one or two missions were contemplated, it could be emerging considerations: (1) We need an initial heavy-lift derivative an B of its mission can provide L. Wopp*ght 1992 The Boeing Company. All Rights Reserved. Printed by AIAA with permission.