Journal of Aerospace Engineering

Human exploration of the solar system can be said to have begun with the Apollo missions. The Apollo Project was publicly funded with the narrow technical objective of landing human beings on the Moon. The transportation and life support systems were specialized technical designs, developed in a project management environment tailored to that objective. Most scenarios for future human exploration assume a similar long-term commitment of public funds to a narrowly focused project managed by a government organization, which becomes a single customer for a large industrial complex supporting the mission. Advocates of human exploration of space have not yet been successful in generating the political momentum required to initiate such a project to return to the Moon or to explore Mars. Alternative scenarios of exploration may relax some or all of the parameters of organizational complexity, great expense, narrow technical focus, required public funding, and control by a single organization. Development of the Moon using private investment is quite possibly a necessary condition for alternative scenarios to succeed.

An overview is provided of the key issues facing those who view lunar development as a desirable goal. There is general agreement that in order for lunar development to begin, there must be a capitalist component of interest. By this is implied the existence of aspects in the lunar development that would attract investor interest. There are two reasons for this. The first is that governments do not have excess funds. Instead, cutting budgets and downsizing are the primary concerns. The second and more important reason is that there is little public support for space in general. While most people, including even a few elected officials, understand the importance of national efforts in space, national spans of attention tend to be short. Therefore, since the development of space requires a long time frame, it cannot retain the attention of citizens or government, and it has a difficult time attracting investor financing. A new paradigm is needed for the further development of space, in general, and the Moon, in particular. It is proposed to deconstruct such a long-term project into independently financeable units that have dual-use potential. This essay proposes such a framework. This approach does not appear to have been suggested by others.

Currently available launch vehicles cannot support logistically the human exploration of the Moon and Mars in the next century. They are too small and too expensive for this job. Past studies have shown that the costs of programs leading to the acquisition and operation of extraterrestrial bases are driven by the space transportation system, which accounts for about two-thirds of total program costs. Consequently, more emphasis has to be placed on the question of the next-generation launch vehicles to be developed. This paper attempts to define the problem at hand and to give an overview of the options and trends to be expected. The issues of expendable versus reusable, as well as small versus heavy lift launchers are discussed. Specific transportation costs for low Earth orbit as well as high-energy missions are presented for selected space transportation system concepts.

The discovery of water ice at the lunar poles can spur lunar exploration and development and may be a factor in accelerating human exploration beyond the Earth-Moon system. Theoretical models predict the existence of ice in the cold traps, and the Clementine and Lunar Prospector missions have given evidence that ice is indeed present. The Lunar Prospector results suggest that the ice concentrations are low, consistent with a cometary source for ice, which is mixed into the regolith by meteorite impact. Initial concepts for extracting ice from the lunar cold traps, where extreme environmental conditions prevail, have been developed; however, more information on the precise location and physical properties of the ice deposits is required before an approach can be selected. The principal implications of lunar ice development could be: (1) cutting the cost of human exploration missions to the Moon by a factor of two, due to the availability of propellant for returning crews and materials to Earth (this could also accelerate the use of the Moon for scientific outposts and human exploration technology testbeds); and (b) creating an opportunity for export of lunar materials to space at a low cost relative to Earth-to-space transportation. The latter would require the development of a reusable, lunar-based transportation system, fueled on the Moon, and capable of delivering payloads to lunar and Earth orbits. If an export economy is initiated, it is important to consider from the outset the conservation of the lunar ice, which is a nonrenewable resource, and to develop alternatives to its use in transportation systems.

Studies on lunar base construction conducted by the writers' research group are summarized. A desirable lunar base design was first discussed by employing a systems engineering approach and by defining an evolutionary scenario, which emphasized resource utilization. Several lunar-base-related concepts were examined from the viewpoint of construction engineering including construction materials, structural design, and construction methods. The research also addressed resource utilization for the production of oxygen and construction materials. A commericial approach toward future lunar development is proposed.

Robotic missions to Mars are listed and significant results of each past mission related to soil engineering are noted. What is known of the Mars environment and surface features that may be of interest to the engineer is summarized. The presumptive engineering properties of soils on the Martian surface are postulated based on expected soil forming mechanisms, the thermal environment found on Mars, and experience from cold region engineering on Earth. The discussion also extends to likely soil characteristics in craters found in the polar regions of the Moon. Experimental results from triaxial testing inert silt (JSC-1 lunar soil simulant) at and near freezing temperatures, with and without water, are also presented. Areas for future investigation and research are suggested.