Imperatives for the Decades 1995 to 2015

Overview

9

Human Presence in Spac

SPACE AGE SCIENCE

It is difficult to determine which of the scientific projects contemplated in this study, other than those in space medicine, compel the presence of humans in space. In fact, there may be no others. With sufficient resources, we might devise automated systems that could substitute for people, performing all of the necessary functions usually associated with humans. People would, in turn, control the machines from Earth. On the other hand, it appears that under certain circumstances people are able to function productively in space and perform tasks in support of scientific investigations. At present, we lack enough information to judge where the balance between manned and unmanned missions should lie.

Some space science missions at the beginning of the twenty-first century may be intended to pave the way for the expansion of humanity into deep space. For many reasons, not all scientific, human activities may extend into an increasing arena of space. With the advent of space stations, plans are already being made by a number of national space agencies for the continuous presence of men and women in low earth orbit, beginning in the 1990s. Such activities in the next century may extend to geosynchronous orbit, and possibly to the regions of the L4 and L5 points. The National Commission on Space has also expressed interest in establishing inhabited stations on the Moon and Mars. Space science practiced at the frontier requires a wide variety of innovations in observational and control capabilities, instrumentation, and propulsion methods. Thus, the pursuit of space science and its supporting functions should be a powerful driver of advanced technology, extending the capabilities of unmanned spacecraft. Advances in the technology of sensors, robotics, artificial intelligence, and parallel computation may enable the development of a new generation of autonomous decision-making machines that will extend exploration and intensive study into remote parts of the solar system—and eventually beyond—without a human presence. Earth orbit can become a proving ground for the deployment of robots, automated observatories, and advanced data management systems.

THE SCOPE OF HUMAN PRESENCE IN SPACE

The space stations of the United States and the Soviet Union are the first steps toward a sustained human presence in space. It is impossible now to predict either the pace or the ultimate extent of this expansion into space. The human-inhabited sphere may never extend beyond low earth orbit. Whether its boundaries are near Earth, on the surface of Mars, or somewhere else, this human-inhabited sphere will be the base from which many future space science investigations are conducted. Conversely, these investigations will provide the foundation needed for continued expansion of this sphere, if called for. Space science experiments, tended in space by human beings, may provide the most important rationale for the staging, assembly, maintenance, repair, and operation of major space facilities (e.g., space astronomical telescopes, earth science experiment payloads/platforms, launch vehicles for planetary missions).

The steering group expects that the sphere of human presence in space wild have relatively distinct boundaries. Within this sphere human presence will be pervasive and well-supported. Many scientific investigations will be carried out under direct human supervision, much as they are on the ground; others wild be conducted in a largely automatic mode, with general supervision from scientists on Earth or perhaps elsewhere within the inhabited sphere.

This confinement of human activities to regions where they can draw upon a host of well-established facilities is advisable for two reasons. First, the capability of humans to make judgments is optimized when there is an opportunity for adaptation, over a long period of time, to the new environment. Second, human manipulative and observational skills can rarely be used effectively without the support of a large array of sophisticated instruments, machines, and facilities. Neither of these two conditions is generally met by brief forays of human beings into regions far from the facilities that support their sustained presence. This applies to manned excursions to Mars, for example, if the human-inhabited sphere is restricted to space near the Earth.

Further, it is important to recognize that the limitations on human survival in space are not well known. At present, we are not certain that mission times can be extended greatly beyond those already experienced, even with considerable technological progress. Low gravity leads to loss of bone mass and other physical effects. High-energy, heavy ion radiation causes irreversible damage to cells, including brain cells. Human relationships in a small, isolated group can badly deteriorate and lead to the loss of functional capabilities. We have not demonstrated the feasibility of a closed ecological system yet, and resupply at a great distance for a long period could be formidable. We must address these issues before we can reach a final decision about the nature and extent of human involvement in expanding the frontier of space.