The spectacular advances of science and engineering in the twentieth century established the basis for creating permanent human settlements in space in the twenty-first century. Since the Moon is our closest celestial neighbor and is in orbit around Earth, it will logically be the next principal focus of human exploration and settlement. The Moon is an excellent platform for astronomical and other scientific investigations, for technological development, and for human habitation. It also has access to the virtually unlimited energy and material resources of space, which can be applied to the development needs of both the Moon and Earth. These opportunities, combined with the universal desire of humankind to explore and settle new lands, assure that the global transformation of the Moon into an inhabited sister planet of Earth will become a reality in this century.

A major impediment to the exploration of space is the...