On the 20th anniversary of the first Apollo-Lunar landing, 20 July 1989, President Bush outlined a long term national program for the Human Exploration of the Moon and Mars
The intent of this paper is to provide insight into advanced transportation planning and the systems that must evolve to support these long-term mission requirements. The general requirements are: launch and lift capacity to low earth orbit (LEO); space-based transfer systems for orbital operations between LEO and geosynchronous equatorial orbit (GEO), the Moon, and Mars; and transfer vehicle systems for long duration deep-space probes. These mission requirements are addressed in the NASA Civil Needs Data Base to promote multiple applications. To accomplish these mission goals, adequate lift capacity to LEO must be available to support science and application missions, to provide for construction of the Space Station Freedom, and to support resupply of personnel and expendables for its operations. Growth in lift capacity must be time-phased to support an expanding mission model that includes Freedom Station, the “Mission To Planet Earth”, and an expanded robotic planetary program. Near-term launch system improvements will capitalize on the existing hardware and infrastructure of the Shuttle.
The near-term increase in cargo lift capacity that could be available by the development of Shuttle-C, a Shuttle derived cargo vehicle, are addressed. The joint DOD/NASA Advanced Launch System studies are focused on a longer term new cargo capability that will significantly reduce costs of placing payloads in space.
Longer term transportation studies explore the Next Manned Transportation System and Space Transfer Vehicles. The Next Manned Transportation System studies focus on concepts to extend, complement, or replace the Shuttle after the turn of the century; assessment for this system apprises three distinctly different paths: Shuttle Evolution, a new Personnel Launch System, and an Advanced Manned Launch System. The Space Transfer Vehicle studies seek the methods to satisfy the robotic and human exploration missions.
Activation of Space Station Freedom in the mid 1990's connotes continuous human habitation with increasing crew complements and activities over time. If a contingency such as an accident or a major medical emergency should arise, there must be an assured crew return capability. NASA recently has initiated contracted Phase A-Prime/B definition studies to evaluate the vehicle options and the system implications associated with providing this capability. Several Assured Crew Return Vehicle concepts under study are described.
These transportation vehicle activities are interrelated and are time-phased to provide a comprehensive planning base for decisions related to future elements of the national space transportation capability. These programs provide broad options in terms of technology, cost, and development risk, as well as in terms of fleet size, lift capacity, and mission operational flexibility. When combined with companion studies on missions and experiments, a complete set of program options will be available for defining the course of the United States Civil Space Program.