More than twenty-five years ago, the first primitive spacecraft tentatively probed the outer space environment surrounding Earth. Above the filtering shroud of the atmosphere, the universe and the Earth itself assumed new clarity. The Earth functions not merely as a planet circling an average star, but also as a dynamic life support system traveling through and interacting with the universe. The Earth represents a spaceship with billions of astronauts on board‹a system unique to the solar system and perhaps to the universe as well.

Each new spacecraft launch produced both new discoveries and subtle (then major) changes in the day-to-day lives of people. Spaceflights generated better communications, improved weather monitoring, innovative products, and new jobs.

As each new space mission posited more questions than answers, increased launch capabilities were required. The first rockets were essentially modified missile systems with restricted payload capacities and limited orbital elevations. For a time, new microelectronics industries helped pack more instruments into smaller spaces, but the space program required still larger payload capacities and more powerful boosts to interplanetary space. NASA built and flew larger rockets, each more complicated and expensive than the last.

By the early 1970s, budgetary pressures forced an evaluation of launch vehicle design. Although the existing family of launch vehicles had grown and diversified to meet a variety of challenges, each vehicle still was expendable. The need for greatly increased launch services, combined with budgetary constraints, seemed to mandate a reusable vehicle capable of repeated trips to orbit. In 1972, the National Aeronautics and Space Administration began a program to develop the world's first space-ship, a reusable vehicle‹the Space Shuttle.

I. The Space Shuttle

The launch of the first Space Shuttle on April 12, 1981 initiated a new era in space travel. Fifty-four and one-half hours later, the Columbia and its crew, John Young and Robert Crippen, glided to a safe landing on the high desert at Edwards Air Force Base, California.

The Space Shuttle represents a new breed of launch vehicles. The Shuttle takes off as a rocket, operates in orbit as a spacecraft, and returns to Earth as a glider. Following refurbishment and attachment of a new propellant tank and solid rocket boosters, the Space Shuttle is ready for a new space mission.

The orbiter constitutes the central feature of the Space Shuttle; Columbia is the first of four orbiters currently scheduled for manufacture. Together the orbiters will form a fleet of reusable spaceships that will carry payloads into orbit for many years. A delta-winged aerospace vehicle comparable in size to a DC-9 jet, the Shuttle orbiter houses a flight deck and crew quarters in the nose. The flight deck incorporates all control functions, and a lower deck provides living accommodations. As many as seven astronauts (three flight crew members and four specialists) can fly into space on board the orbiter, although the normal crew ranges from two to four astronauts. The midsection of the orbiter is a cargo bay large enough to transport one and one-half buses. The cargo bay accommodates a total of 29,500 kilograms (65,000 pounds) of satellites and other payloads, and 14,500 kilograms (32,000 pounds) can be returned to Earth if necessary.

At liftoff, the three main engines in the orbiter's tail and the two solid rocket boosters produce nearly 30 million newtons (6 and 1/2 million pounds) of thrust. Approximately two minutes into flight, the boosters separate and parachute into the ocean for recovery and reuse. Over the next six and one-half minutes, the giant external tank mounted on the orbiter's underside is emptied of liquid hydrogen and oxygen used by the orbiter's three main engines. The external tank is jettisoned and destroyed by atmospheric friction on reentry. Any surviving pieces fall into preplanned remote ocean areas.

Two small orbital maneuvering system engines accomplish the final thrust into orbit. Pods on either side of the orbiter's vertical tail store the propellants for these engines. While in space, all maneuvering depends on these two engines, and forty-four thrusters mounted in the nose and tail provide attitude control.

In orbit, large clam-shell doors in the mid-section of the orbiter open to uncover a cargo bay 18.3 meters in length by 4.6 meters in diameter (60 by 15 feet). As many as four satellites can be carried to orbit in the bay at one time. Satellites requiring repair or maintenance can be maneuvered into the cargo bay by a 15-meter-long mechanical arm, the Remote Manipulator System (financed and developed by the National Research Council of Canada ). The arm also deploys satellites and other spacecraft in orbit. Additionally, the cargo bay serves as a platform for scientific research: staffed laboratories can be housed in the bay, and automatic experiments can be exposed directly to the outer space environment. Furthermore, the orbiter cargo bay functions as a staging point for spacecraft destined for higher orbits than the nominal 160- to 970-kilometer (100- to 600-mile) range of the Shuttle. Small upper stage rockets will accelerate payloads to geosynchronous orbits and interplanetary courses.

To return to Earth, the orbiter rotates in a tail-first direction. A two and one-half minute burn of the orbital maneuvering system engines slows the vehicle as it swings around nose first and begins the reentry process. Thirty minutes prior to landing, the orbiter encounters the upper atmosphere at an altitude of approximately 122,000 meters (400,000 feet). Using combinations of thrusts produced by the small reaction control rockets, the orbiter realigns into a nose-high attitude.

Intense friction between the orbiter and the thin atmosphere heats portions of the exterior to temperatures exceeding 1,260°C (2,300°F). A dense surface insulation called reinforced carbon/carbon is attached to the nose and leading edges of the wings. This substance is a carbon cloth impregnated with additional carbon, treated with heat, and then coated with silicon carbide. A silica fiber tile covers most other areas of the orbiter skin. The tile receives a glassy ceramic black coating for the underside of the orbiter and a white coating for the top. Still other areas of the orbiter skin are covered with a silicon-coated Nomex felt blanket material.

As air density increases, vehicle speed converts the orbiter from a spacecraft to an aircraft. Attitude control shifts from the reaction control rockets to the aerodynamic surfaces on the wings and tail. By the time the rear landing gear touches down, the orbiter velocity has slowed from an orbital speed of 28,160 kilometers per hour (approximately 4.9 miles per second) to 350 kilometers (220 miles) per hour.

Back on the ground, the Shuttle orbiter undergoes a refurbishment and repair process: expendable supplies are replaced; returned payloads are removed and new ones inserted; a new external tank is mated to two refueled, reusable solid rocket boosters; and the orbiter is joined to the tank and boosters in a vertical position. Within several weeks, the Space Shuttle can return to space for another mission. The orbiter is designed for one hundred missions and the solid rocket boosters for ten to twenty missions .

II. Space Transportation Prospects and Limitations

The Space Shuttle constitutes the main component of NASA's Space Transportation System (STS). Along with some existing low-cost expendable launch vehicles, the Shuttle offers users an unprecedented degree of reliability and versatility at a considerably lower price than previously available. Because the orbiter includes a cavernous cargo bay, spacecraft and satellite designers have more freedom in choosing components; former constraints required custom-built components to fit into comparatively tight payload compartments. This Shuttle advantage alone promises to produce major savings for payload developers.

To reduce design complexity, oversized payloads can be launched in a disassembled form for assembly in space by the Remote Manipulator System (RMS) or by space-suited astronauts. The RMS represents an analog to the human arm and can be operated automatically or by astronauts working on the orbiter flight deck. For more intricate assembly tasks, astronauts will don space suits and clamber over spacecraft, possibly attaching solar cell panels and experiment booms. For additional mobility, a compressed-gas manned maneuvering unit (MMU) can be worn to propel astronauts to desired locations. Human support for satellites, spacecraft, and on-board experiments constitutes one of the more valuable features of STS

Small booster rockets that can be carried in the orbiter cargo bay will raise satellites to higher orbits than those of the Shuttle. Boosters such as the Spinning Solid Upper Stage (SSUS) and the Inertial Upper Stage (IUS) will lift satellites to geosynchronous orbit. Spacecraft targeted for interplanetary travel may be boosted by a modified version of the Centaur upper stage presently used by Atlas and Titan launch vehicles.

The utility and versatility of the STS is perhaps best demonstrated by user demand‹the Shuttle has booked over seventy operational flights (as of June 1981). Additional requests for flight accommodations are in negotiation. Moreover, potential STS users have substantially increased the number and scope of studies analyzing potential Shuttle-based space operations. As the system matures, the demand for STS flights and services will likely expand significantly.

Indeed, NASA studies of STS utilization indicate that near-term user needs call for longer missions and greater on-board electrical power than the baseline Shuttle can provide, particularly for missions in fields such as life sciences, materials processing, new science and applications payloads, and high-capability communications systems. To satisfy these needs, NASA plans to develop a deployable solar cell array, the power extension package (PEP). PEP would be mounted on the Shuttle RMS, which will position and hold PEP outside the orbiter cargo bay. Increased power would allow the vehicle to extend orbital stay time from seven to thirty days.

Long-term studies of the potential for Shuttle-derived technologies demonstrates that continued enhancement of the basic STS may generate increasingly large payoffs for individual users (governmental, commercial, and scientific), as well as for the nation and its international partners.

To achieve these payoffs, at least two conditions must be satisfied. First, STS enhancement must follow a clearly defined evolutionary path, designed to: expand and maintain space policy options; respond to changing national goals; and accommodate varying economic, social, security, and political environments. Second, proposals for new Shuttle-derived space technologies should be accompanied by ongoing, objective assessments of the socio-economic implications of these technologies.

III. Three Stages of Shuttle-Based Space Technology Development

Projections of future space development can be too conservative, too optimistic, or simply incorrect. A NASA-sponsored seminar of long-range space planners informed NASA in 1980 that:

When the committee began its discussion of these arcane conjectures it was aware of an earlier failure. We recall that in 1937 when Franklin Delano Roosevelt convened a group of our most distinguished scientists to advise him on impending technological advances which might influence American policy, these outstanding minds did not anticipate nuclear power, rocketry, antibiotics, radar or the electric computer, all of which were about to surface.

Clearly, the pace, direction, and scope of Shuttle-based space activities depend on several factors, including, for example: technological feasibility; the level of demand for space services, determined by a variety of user communities (civil and military government groups, commercial enterprises, and other nations); the economics of space-based versus terrestrial goods and services; competing national scientific, security, political, and economic priorities; and the national and international legal and regulatory structures governing space activities.

In contrast to the preceding discussion of the basic Space Transportation System, this section focuses on future Shuttle-derived space technologies and activities. Of necessity, such a review must be speculative. Much of the value of social analyses of space technologies lies in anticipating the societal implications of the widespread adoption of new space systems. Using such analyses, space technologies most likely to benefit society may be isolated early in the research, design, and development stage; concomitantly, some space systems resulting in little or no benefits or producing counterproductive impacts may be discerned before large-scale commitment and implementation .

To achieve this goal, social studies must examine proposed new space technologies as promptly as possible. Of course, such examinations do not constitute a definitive schedule for the development of Shuttle-derived space utilization technologies. Rather, these analyses attempt to describe possible evolutionary paths for future space program development, based on the conclusions of contemporary NASA studies. Each of the proposed space technologies and systems is feasible within the delineated time frame. However, the degree of certainty of implementation of any given system declines in inverse proportion to the number of years and level of funding required to achieve operational status. Three possible stages of Shuttle-derived space technology development are described below.

A. The 1980s: Learning to Use the Space Transportation System

Following the successful completion of Space Shuttle test flights in mid-1982, the remainder of the decade will focus on learning to use the Shuttle's capabilities most effectively. By 1985 the Shuttle fleet will include four orbiters. In 1983 the STS will begin routine operations by transporting satellites, space probes, booster rockets, experiment facilities, and crews to and from near-Earth orbit. Specific Space Shuttle projects fall into the following areas (each discussed below): space science and astronomy, space applications and utilization, and military applications.

(1) Space science and astronomy. The planet's murky atmosphere inherently limits Earthbound astronomy. Spaceflight provides the capability to place into orbit sensitive new instruments that greatly augment existing knowledge of the solar system, galaxies, and high-energy objects such as quasars and pulsars. Perhaps the most dramatic advances in space-based astronomy stem from the Space Telescope, scheduled for Shuttle launch in 1986. The 13-meter-long (43-foot-long) telescope features a 244-centimeter (96-inch) primary mirror, accompanied by five auxiliary instruments. Flying above the atmosphere, the telescope will significantly increase both the number of astronomical objects visible for study and the distances that can be covered. Astronomers thus will be able to resolve objects five to ten times smaller in angular diameter than those subject to ground-based optical observations. Because of the interrelationships among cosmic distance, light and wave transmissions from objects in space, and time, the Space Telescope will allow astronomers to peer billions of years back in time‹into the early evolution of the universe. Astronauts from the Shuttle will service the Space Telescope in orbit; however, the instrument will be returned to Earth approximately every five years for refurbishment.

Other Shuttle-based astronomical instruments that might be launched in the late 1980s include the Gamma Ray Observatory (GRO) and the Shuttle Infrared Telescope Facility (SIRTF). Gamma ray astronomy explores the highest-temperature and most explosive astrophysical objects, specifically neutron stars and possibly black holes. Gamma ray studies not only enhance knowledge of these highly energetic transmission sources, but also provide direct data on the nuclear processes of such objects‹thus creating a new field of astronomy, nuclear astrophysics. SIRTF would supplement and extend current ground-based infrared studies of astronomical objects and processes such as luminous infrared galaxies, quasars, star and solar system formation, and mass exchange between stars and the interstellar medium. Through infrared observations of phenomena such as the galactic "red shift," SIRTF would contribute data important to understanding the early history of the universe and the expansion of the galaxies.

Planetary exploration during the next decade will utilize the Shuttle as a launch platform. The Jupiter orbiter/probe Galileo represents the first planned Shuttle-based planetary exploration mission. Now scheduled to arrive at Jupiter in 1989, Galileo will perform two tasks: the Galileo orbiter vehicle will conduct scientific studies of Jupiter and its satellite system from an orbital vantage point; and the probe, the first vehicle ever to enter Jupiter's atmosphere, will descend through the atmosphere, measuring and transmitting data back to the Galileo orbiter, which will relay the information to Earth. The probe should survive as long as one hour in the intense Jovian atmospheric pressure.

(2) Space applications/utilization. A significant segment of Shuttle missions in the 1980s will provide routine transportation for applications satellites sponsored by the U.S. government, scientific institutions, firms or industries, and other nations. For example, in its first four years of operations, the Shuttle will carry communications satellites into orbit for Canada, Indonesia, Intelsat, RCA, Saudi Arabia, Bell Telephone, and the People's Republic of China.

The new launch and repair capacities inherent in the STS probably will spur a revolution in satellite services. Existing satellite systems require large and expensive Earth receiving stations because of launch vehicle limitations on payload sizes and the inability of current launch vehicles to retrieve and/or repair satellites in orbit. The Shuttle will transform these constraints‹satellites can be larger and far more complex, and ground stations can be small, portable, and inexpensive. This phenomenon, called "complexity inversion" by space engineers, could fundamentally alter the economics of space-based information services; user costs could decline dramatically, producing sizable increases in user demand. Public service satellite systems could be economically implemented (for example, a system linking paramedics and physicians assistants in remote areas with trained urban hospital staffs). Indeed, advanced satellite communication systems made economical by the Shuttle could influence humanity's lifestyles and interactions as profoundly as the advent of the telephone or television. Advanced Shuttle-delivered and Shuttle-serviced satellites could be applied to emergency rescue systems, improved aircraft traffic control, electronic mail, border surveillance, forest fire detection, earthquake prediction, nuclear materials location, and many more projects.

One advanced satellite technology certain to emerge during this period‹the direct broadcast satellite (DBS)‹ differs fundamentally from traditional broadcast media, including extant satellite television systems. DBS eliminates the need for large and costly local reception and retransmission facilities; rather, the original signal is beamed to a DBS in geosynchronous orbit, then relayed from the satellite directly to relatively small and inexpensive dish-shaped antennas mounted on the roofs of individual homes. Each DBS services homes within a wide geographic area. The Communications Satellite Corporation (Comsat) intends to offer a three-channel DBS system to millions of home subscribers in the mid-1980s. A study by RCA Americom predicts that as many as fifty-two DBS orbital satellites will be launched in the 1980s. DBS advocates envision a direct broadcasting system that will extend television service to remote areas not now served, as well as significantly expand viewing options by fostering alternative programming.

Beyond the transmission and provision of data, satellites have proved quite useful in detecting and mapping renewable and nonrenewable Earth resources. NASA's Landsat satellite series provides multispectral images of global resources for a variety of national and international users. The Landsat series originally relied on three satellites launched in 1972, 1975, and 1978 (all now virtually inoperable). A fourth satellite, Landsat 4, was launched by a Delta rocket in 1982, and Landsat D' is scheduled for Shuttle launch in 1986.

These new Landsat satellites will mark an important shift in the focus of the program. To date, NASA has classified the system as experimental. In contrast to the communications satellite industry, a mature market with estimated gross expenditures of $11 billion annually, Earth sensing is not yet a fully operational service. Demand for Landsat imagery has outstripped the existing system's designed capability in terms of quantity, quality, and timeliness of data. State and local governments use Landsat imagery for a variety of purposes, such as mapping land use patterns, managing state lands, and monitoring environmental pollution. National governments rely on the images for numerous functions, including crop forecasts, water resource use analyses, and overall resource assessments. Individual companies also employ Landsat data, for example, in oil and mineral exploration and new factory siting decisions. Landsats 4 and D' will constitute the basis for the operational system, carrying the latest in Earth-sensing technology. Data will be recovered via NASA's Tracking and Data Relay Satellites (TDRS), a system of Shuttle-launched orbiting data relay satellites scheduled to be operational by 1984. Landsats 4 and D' have been turned over to the Department of Commerce for operational management‹and perhaps ultimately transferred to private sector control.

Additional remote sensing satellites may be deployed by the Shuttle in the 1980s. Candidate systems include a stereoscopic satellite which is particularly useful in oil and mineral exploration and a synthetic aperture radar device which can observe the oceans and obtain a variety of data on sea surface conditions.

The development of space industrial applications represents one of the more important long-range benefits of the Space Shuttle. Studies conducted on small sounding rockets, in the Skylab orbital workshop, in ground-based materials laboratories, and by Soviet cosmonauts on the Salyut Space Station suggest that the microgravity and vacuum characteristics of space may offer several advantages over ground-based methodologies in the processing of metals, fluids, crystals, and living cells. For example, the microgravity conditions would dramatically reduce convection during melting and solidification; convection currently prevents Earthbound scientists from producing a truly homogeneous material.

Spacelab, a joint project between NASA and the European Space Agency (ESA), may play a vital role in demonstrating the viability of space industrialization. Spacelab is a modular "shirtsleeve" laboratory that will go into space in the Shuttle cargo bay and return to Earth at the end of the flight. This self-contained facility affords scientists the opportunity to conduct science and applications experiments in the near zero-gravity conditions of Earth orbit. Ten European nations financed the development of Spacelab, which more than forty European companies produced under ESA contracts. ESA provided the first Spacelab (including test and ground equipment), which may be flown on the Shuttle as many as fifty times during its ten-year lifespan. Both NASA and ESA will develop experiments and train mission specialists for the orbiting laboratory. The U.S. will purchase from ESA any additional Spacelab modules required by the STS user community. In February 1980, the United States agreed to purchase a second module for 1984 delivery.

Depending on mission requirements, Spacelab can incorporate one or two pressurized cylinders (each four meters wide by two and three-quarters meters long, or thirteen feet wide by nine feet long); each cylinder can both accommodate one to four mission specialists (who can conduct a variety of tasks and scientific experiments) and include as many as five external pallets. The pallets serve as platforms for mounted experiments that require exposure to the space environment (Spacelab functions with the orbiter's cargo bay doors open). Moreover, Spacelab pallets cool equipment and generate electricity for the experiments. Typical pallet-mounted experiments include telescopes and antennas. In some mission configurations, the pallets are used without the pressurized cylinders and are controlled from the orbiter main cabin.

In many ways, Spacelab serves as a model for a free-flying space station such as the proposed Space Operations Center (described in a subsequent section). The pressurized module contains lights, electrical outlets, work spaces, storage facilities, an airlock, and an optical window. Available experimental facilities also include telescopes for several wavelengths, furnaces, high-energy lasers, microscopes, centrifuges, and incubators. Many of the candidate missions build directly on experience acquired from Skylab, an earlier space station derived from Apollo-era technology.

Candidate Spacelab missions reflect the scope of potential uses of the Shuttle-provided space environment. Scheduled for the fall of 1983, the first mission will carry thirty-five experiments (twenty-one from ESA, fourteen from NASA) for seventy-two separate investigations in the fields of medicine, plasma physics, atmospheric physics, Earth observations, astronomy, solar physics, life sciences, and materials science. Subsequent missions may emphasize certain themes, for example, the "Earth viewing application laboratory," which will conduct a world crop survey, assess global mineral deposits, inventory water resources, study weather and climate, supply data for urban planning, and investigate the oceans. Other theme missions might focus on astronomical research, advanced technology experiments (which examine the behavior of materials in the microgravity and vacuum conditions of orbit). Spacelab also will be available for rental to users who want to conduct experiments of their own design for possible commercial applications.

One of the earliest attempts to commercially exploit the Shuttle will be an apparatus that will perform a continuous-flow electrophoresis process which will separate biological materials. McDonnell Douglas Corporation is building the apparatus under a joint endeavor agreement with NASA. If the initial 204-kilogram (450-pound) device successfully produces ultrapure pharmaceutical products (such as vaccines and serums) during a six-flight test sequence, McDonnell Douglas and the Johnson & Johnson Company subsequently will launch a 4,535-kilogram ( 10,000-pound) long-term system to be deployed in orbit for continual production.

One of the earliest electrophoresis products may be urokinase‹an enzyme that can be separated from human kidney cells and will dissolve blood clots. Current urokinase production costs in Earth laboratories are prohibitive‹a single dose can cost $1,500. An experiment conducted in 1975 on the joint U.S.A./U.S.S.R. Apollo-Soyuz space mission successfully separated the enzyme from the kidney cell cultures at six times the efficiency achieved to date on Earth. One analysis suggests that full-scale production of urokinase on the Shuttle or Spacelab could lower the cost to $100 per dose. Such a reduction could stimulate the use of urokinase in both research and treatment, possibly preventing as many as 50,000 blood clot deaths annually in the United States alone.

Other candidate products for space processing experiments on the Shuttle and Spacelab include electronic components (such as pure crystals for semiconductors and silicon ribbon for integrated circuits), improved turbine engine blades, and advanced optical products for laser systems. Experiments in these fields in the 1980s should do much to establish whether or not space processing will ever achieve commercial viability.

In 1980, the General Accounting Office issued a report which recommended that the United States increase funding by two to three times in order to maintain parity with other nations' efforts (particularly those of the Soviet Union, Japan, and West Germany) in space processing given its potentially enormous economic and social implications .

(3 ) Military applications. Although the Space Shuttle operates primarily as a civilian project, the Department of Defense (DoD) plans to make extensive use of the Shuttle. Military interest in and use of the space environment constituted a crucial factor in Shuttle design (at Air Force request, the cargo bay was enlarged to its current size to accommodate military payloads).

The importance of space to national security stems from many of the same attributes that make space useful for scientific and industrial purposes. Considered the "high ground" by military strategists, space already serves a critical function in information collection and distribution (for example, monitoring arms control agreements and tracking troop and weapon deployments). Moreover, the various armed services operate their own navigation, communications, weather, and surveillance satellites.

The Space Shuttle will augment greatly such military space capabilities. Although many DoD Shuttle payloads are classified, some missions probably will deploy a new generation of reconnaissance, communications, and navigation satellites. Shuttle capabilities also allow in-orbit satellite repairs and other activities such as film retrieval. Because of the Shuttle's large payload capacity, satellite design parameters can be altered substantially. Military satellites can be larger and less expensive, incorporate additional systems for redundancy, and claim a longer life span.

DoD also is considering the military utilization of Spacelab. Potential military Spacelab missions include: (a) basic scientific research‹for example, the impact of solar physics on communications and navigation; (b) long-term exposure to the space environment‹military space systems require a high degree of survivability; and (c) materials processing in space‹for example, high-purity crystals for semiconductor elements.

To date, military space systems have exclusively supported defense and military activities on Earth. As both the civil and military communities increasingly rely on space technologies in the future, some observers project a new role for military space systems‹i.e., defense of space assets. Of course, international treaties prohibit weapons of mass destruction in space; nonetheless, military researchers study space weaponry such as antisatellite devices and space-based laser antiballistic missile systems. Although DoD has not clarified the Shuttle's role in the development of these systems, the vehicle does constitute an invaluable system for military uses. Furthermore, experimentation on board the Shuttle in the 1980s likely will identify a large number of new applications for subsequent military space systems.

B. The 1990s: Moving Toward Permanent Space Facilities

By the late 1980s, STS should be a mature technological system, an integral component of an expanding national and international economy, and an important tool for new scientific experimentation and discovery. To ensure the continued orderly development of U.S. space capabilities, a new technological goal for NASA probably will be established, focusing on an evolutionary follow-on to the STS (in addition to ongoing space science and application projects). The next logical new goal for the NASA budget in the mid-1980s may well be a program to achieve permanent occupancy of space by the early 1990s (1).

A national commitment to the permanent occupancy of near-Earth space will address a number of needs, including: (1) user requirements for: additional orbital stay time; increased electrical power; and facilities for servicing payloads, deploying spacecraft to geosynchronous orbit, and conducting long-term, human-tended experiments; (2) the national objective of establishing a secure base for military and civilian activities; and (3) federal requirements to provide for the continual and orderly development of future space technologies by defining an ongoing goal, thus helping to maintain the nation's overall technological base. Several technological bases of permanent occupancy of space are discussed briefly below.

(1) Space platforms. The Shuttle's large capacity and relatively low cost should encourage the aggregation of satellite experiments and applications into larger, multipurpose orbiting facilities. In contrast to separate spacecraft for each experiment or application, space platforms will accommodate many projects simultaneously and produce major economic savings in spacecraft design and construction. Space platforms will provide electrical power, attitude control, and communication services for all aspects of experiments and applications.

These unstaffed platforms will be placed in a variety of orbital inclinations and altitudes, including geosynchronous orbit. However, space platforms in geosynchronous orbit would require a low-orbit staffed space station and orbital transfer vehicles to both build and service the platform. The Shuttle will directly service space platforms in low orbit.

(2) Space stations. The cornerstone of a program for permanent space occupancy is a constantly staffed space station (or a number of space stations) which can support a variety of scientific, applications, construction, and orbital support missions.

NASA planners believe that orbital space stations may be based on one or both of two approaches. In one scenario, NASA would employ an evolutionary approach to augment unstaffed space platforms by adding one or more habitation modules, thus providing the necessary infrastructure for permanent low-Earth science and applications platforms (SAMSP). These facilities would serve principally as scientific research and surveillance stations for both military and civil purposes. Low-Earth polar orbits for crew-occupied platforms would be ideal for Earth resources surveys and/or military surveillance missions. Higher altitude equatorial orbits would seem more convenient for long-term scientific studies. However, polar orbit stations would not service spacecraft and facilities bound for geosynchronous orbit.

NASA also is studying the advantages of a Space Operations Center (SOC)‹incrementally built and staffed by a permanent crew‹that would serve as an orbital way station between Earth and geosynchronous orbit or deep space. In addition to SAMSP's advantages for research and surveillance, NASA engineers contend that the SOC would facilitate: (a) construction, checkout, and transfer to operational orbit of large, complex space systems; (b) on-orbit assembly, launch, recovery, and servicing of staffed and automated spacecraft; (c) management of co-orbiting free-flying satellites; and (d) development of the capability for permanent human operations in space with reduced dependence on Earth for control and resupply.

The SOC would play a primary role by permitting routine access to geosynchronous orbit by Shuttle payloads and large structures such as advanced communications satellites. Cargo would be off-loaded at the SOC and shifted to orbital transfer vehicles for transport to geosynchronous orbit.

NASA envisions building the SOC from modules and aggregates transported to orbit by the Shuttle for assembly. The SOC would include two service modules, each providing: electrical power, generated by two large solar arrays; guidance, control, and stabilization; reaction control; communications; and airlocks for extravehicular activity. Two habitation modules would be attached to the service module; each habitation unit would operate: a command center capable of controlling the entire station; private quarters for four; food, hygiene, and waste management facilities; and exercise and recreation equipment. One habitation module would contain a health maintenance facility, the other a small laboratory.

(3) Orbital support and advanced transportation. To fully realize the potential of automated low-orbit platforms, geosynchronous platforms, and space stations, NASA requires further advances in orbital support and transportation systems. Typical support system components include an advanced maneuvering unit to enable astronauts to perform extravehicular activities. Worn over space suit life support systems, the maneuvering units generate propulsion thrust by venting compressed gas through a system of nozzles. "Cherry picker" mobile maneuvering units (both open and closed cab types) and teleoperator maneuvering devices represent other possible support systems. These types of support system devices would assemble space structures and service spacecraft.

Transport of materials and supplies to geosynchronous orbit requires the development of new Shuttle-derived vehicle technologies, such as a reusable orbital transfer vehicle (OTV). The OTV would travel from the SOC to high-energy orbits and then return to the SOC (initially transporting payloads, subsequently flight crews).

The Shuttle-derived cargo vehicle (SDCV) constitutes another important space transportation system. Many missions planned for the late 1990s likely will require both much greater lifting capacity than the Space Shuttle presently generates and significantly lower launch costs than those currently available. For example, in one SDCV concept, the orbiter would be replaced by a large, automated payload package attached to the orbiter's main propulsion system, i.e., the standard external tank and solid rocket boosters (SRBs). This configuration would place a 68,000-kilogram (149,900-pound) payload into low-Earth orbit. Replacing the SRBs with liquid-fueled boosters and other modifications would uprate the vehicle's payload capacity to as much as 160,000 kilograms (352,700-pounds) to low-Earth orbit. In another concept, only the Shuttle SRBs would be used in one of several possible configurations to increase payload launch capability.

The solar electric propulsion system (SEPS) might serve as another transport vehicle for the 1990s. SEPS would produce thrust by electrically charging a vapor of an element such as mercury and then accelerating that vapor through an electric field. Although SEPS would generate very low thrust, the power would be continuous over a period of several months and gradually would accelerate a payload to extremely high velocities. NASA conducted orbital tests of SEPS engines on experimental satellites for many years with great success. (However, further development of SEPS currently is suspended.)

Thus, with these program elements‹automated space platforms, staffed space stations, and orbital support and advanced space transportation technologies‹the U.S. can establish a permanent presence in near-Earth space early in the 1990s. Such a presence should enable an entirely new generation of space technologies to service expanding economic, scientific, and social needs on Earth and in space. Some of these technologies and their applications are described below.

(4) Space technologies and applications. The Shuttle can enhance capabilities to construct large space structures for low-Earth and geosynchronous orbit applications in space sciences and astronomy. But the Shuttle also can facilitate the construction of devices and large structures targeted at fundamental advances in space-based astronomy and astrophysics. A recent NASA-sponsored study described one such potential system, a pair of wideband Michaelson interferometers. Such an optical system could: . . . detect an Earth-sized planet in orbit about a star thirty-two light-years away, calibrate the distance scale of the universe by measuring directly the distances and luminosities of the Cepheid variables, measure the proper motion of stars in our own and neighboring galaxies, and observe the second-order relativistic deflection of starlight by the Sun (2).

The same study detailed laser instruments that would detect gravity waves generated by the collapse of stars and by the formation of black holes.

Other candidate astronomy and astrophysics technologies for the 1990s include: (a) a large X-ray telescope to measure spectra from celestial sources; (b) a 10,000-kilogram solar observatory to make high-resolution spatial, spectral, and time measurements across all light wavelengths for advanced studies of the Sun; and (c) a large-scale microwave telescope to conduct very advanced radio astronomy experiments and perhaps search for radio waves emitted by extraterrestrial civilizations.

In planetary research, the initial reconnaissance of this solar system should be nearly completed for all planets but Pluto by the 1990s. New Shuttle-based solar system exploration projects should advance this research into the 1990s. Proposed missions to the outer planets (Uranus, Neptune, and Pluto) would take advantage of Jupiter's orbital position between 1989 and 1997 to launch gravity-assisted spacecraft. Another high priority outer planet mission would employ an orbiter and probe configuration similar to Galileo to probe both Saturn's atmosphere and that of the moon Titan.

During this period, a mission to rendezvous with an asteroid could use either ballistic trajectories (chemical propulsion) or low-thrust trajectories (SEPS). Such a mission could include a landing to analyze asteroid surface composition. This asteroid reconnaissance mission could produce progress in both pure science and the exploration of the feasibility of acquiring and using asteroid materials for near-Earth space manufacturing and construction (discussed below).

Exploration of the inner planets offers similarly intriguing possibilities. Mission options include a Mercury orbiter and lander and a variety of lunar missions (e.g., a lunar polar orbiter that would map and analyze the high latitudes of the Moon). Another mission would land a spacecraft on Venus to conduct a chemical analysis of apparently one of the most complex and radioactive soil compositions in the solar system. Such a mission would be a strong candidate for a joint U.S./U.S.S.R. effort because of the Soviet Union's long-term interest in the exploration of Venus.

Perhaps the most exciting prospects for automated, Shuttle-based solar system exploration in the 1990s focus on advanced investigations of Mars. Despite a relatively substantial Mars exploration program‹including the first attempt to discover extraterrestrial life‹numerous unanswered questions and unresolved puzzles remain. Scientists and engineers have devised several STS-based missions, including a Mars polar orbiter, a network of scientific stations, a robot roving vehicle, an airplane explorer, and a soil sample collector.

Opportunities during the 1990s for meaningful, Shuttle-based solar system exploration likely will exceed U.S. financial and information management and analysis capabilities. However, space exploration programs of this type naturally lend themselves to international cooperative ventures. Such international cooperation would accelerate the pace of planetary exploration, but even a vigorous international effort during the 1990s probably would overlook numerous important missions that could be scheduled for the post-2000 period.

The economic development and utilization of space systems and resources (termed space industrialization by space planners) present significant challenges and opportunities for STS and Shuttle-derived technologies during the 1990s (3).

Several space environment characteristics suggest a host of possible applications for Shuttle-based industries, based on factors such as: (a) easy control over gravity; (b) absence of atmosphere; (c) comprehensive overviews of the Earth's surface and atmosphere; (d) isolation from Earth's biosphere (particularly relevant to hazardous processes); (e) freely available light, heat, and power; (f) infinite natural reservoirs for disposal of waste products and safe storage of radioactive products; (g) super-cold temperatures; (h) large, three-dimensional volumes (storage structures); (i) a variety of non-diffuse (directed) radiation; (j)magnetic field; and (k) availability of extraterrestrial raw materials (4).

Beginning in the mid-1970s, NASA began to assess the potential of space industrialization in the Shuttle age. In 1977 NASA released a Rockwell International study which concluded that: ... space industrialization is relevant to many urgent problems afflicting the nation and mankind. It offers important practical opportunities for strengthening our economy and provides access to new energy and material resources. It reduces the burdens on the terrestrial environment and offers new options for human growth in an open world (5).

Together, these NASA-sponsored studies (6) constitute a technological and economic framework for projecting the pace and focus of space industrialization. Such studies thus serve as an invaluable research tool for students and teachers interested in analyzing the implications of Shuttle-derived technologies; reports have identified literally hundreds of potential space industrial opportunities. Of course, actual implementation of specific industrial systems and technologies will depend on several factors, including economic viability, competing national priorities, and social and institutional implications.

The individual systems and technologies relevant to Shuttle-based space industrialization in the 1990s seem to cluster in four broad areas: (a) information systems; (b) products manufactured in space; (c) energy generation applications; and (d) humanization. A Science Applications, Inc. study detailed the following subdivisions within the four industrial activity categories (7).

Information Services
Earth observations
Location determination
Sensor polling

Solar power satellites
Redirected isolation
Nuclear waste disposal
Nuclear power or breeder satellites
Power relay satellites

Electronic components
Electrical components
Structural items
Process improvements

Medical care
Entertainment and art
Education Support facilities

Some of the specific technologies within these categories are considered below. These discussions should introduce the reader to the range of products and services potentially available within a program of Shuttle-based space industrialization. The actual studies provide a relatively comprehensive listing of the various relevant technologies.

Information systems. Communications and Earth-sensing satellites constituted a maturing industry in the 1980s and should develop into an advanced industry in the 1990s. For example, personal communications satellites could be operational in the early 1990s; in one scenario, a single 67-meter-diameter satellite in geosynchronous orbit could service twenty-five million people with two-way voice and data communications using wristwatch-size ground-based radio sets (8). technologies.

Public service applications for large, multi-beam satellites are many and varied. For example, such satellites could: establish immediate communication links with rescue authorities during disasters; provide continuous, all-weather monitoring of global air and ocean traffic; improve educational services in remote areas through direct broadcast of public service programming; and facilitate remote health care services via three-dimensional teleconferencing (9). technologies.

One public service satellite proposal would group several functions on a single, large satellite in geosynchronous orbit. This satellite would weigh 29,500 kilograms (65,035 pounds), measure 240 meters (9,449 feet) in length, generate 500 kilowatts of solar cell power, and deploy 23 antennas. The system would supply the continental United States with a broad range of services, including: (1) educational programs broadcast over five simultaneous video channels for sixteen hours each day; (2) personal voice communications; (3) national information services affording instant access to government, university, and industry data banks; (4) teleconferencing on as many as 150 simultaneous two-way video channels; and (5) electronic mail transmission at a rate of forty million pages per day (10).

During the 1990s, Shuttle-borne Earth resource sensing satellites located in polar orbits should offer increasingly sophisticated views of the planet that will be useful for renewable resource management. For example, advanced satellites should produce a continual, comprehensive assessment of worldwide crop production levels. Such an agricultural watch should accrue significant benefits if conducted and institutionalized to inspire international cooperation (11). Other advanced Earth resource systems that might be functional in the 1990s include: (1) water availability forecasting; (2) living marine resources assessments; (3) timber inventories; (4) large-scale weather forecasting and climate prediction; and (5) insect monitoring and control systems (12).

During the 1990s, hazard warning systems (particularly satellite-based earthquake prediction systems) should generate substantial interest in the field of advanced Earth sensing systems. Recently acquired scientific knowledge in geology and seismology‹on topics such as plate tectonics‹may provide the basis for constructing accurate earthquake forecasts. Very long baseline interferometry and laser measurements of the Earth's crustal movements should contribute significantly to the knowledge base and, subsequently, to an operational system for earthquake predictions. In this system, Shuttle-deployed satellites would reflect radio signals and laser beams to ground-based instruments on an auxiliary basis (13). Analysts would combine the data from these subsystems with ground-based measurements from the operational system. Such an operational system would reduce risks to life, increase the ability to prepare for and respond to disasters, and lower the costs of international rescue and assistance efforts (14).

Products manufactured in space. An inhabited space station or operations center equipped with solar power augmentation modules should facilitate greatly the development of commercial space processing, perhaps leading to the first true "space factories" in the 1990s. If successful, initial experiments aboard Shuttle and Spacelab in the 1980s should identify the viable systems and processes that hold the greatest potential for early commercial and industrial applications. One study predicts that semiconductors produced in orbit could account for ten percent of the total market ($1.27 billion) by the end of the decade (15). Moreover, space processing and manufacturing probably will focus on numerous other products and applications, described earlier, that could prompt national and international governments and corporations to invest significant resources in the space-based economy. Such investment may spur the development of additional multipurpose or dedicated space operations centers, with attendant demands for expanded orbital transportation and support systems.

Energy generation applications. A permanent space occupancy program fundamentally would attempt to fulfill important terrestrial needs in a cost-effective manner by applying selected space technologies. The provision of adequate and economical energy supplies in an environmentally acceptable mode should continue to dominate Earth's resource and industrial requirements throughout the remainder of the century.

Space industrialization would supplement the terrestrial energy base in several ways, specifically by:
(1) Providing technology that can be used to generate and transmit energy on Earth and to dispose of waste products associated with fission power. One industry estimate suggests that producing silicon crystals in space might reduce the cost of switching from AC to DC power transmission on Earth by as much as $76.5 billion over the next twenty years (16). NASA also is studying the prospects for STS disposal of nuclear waste material in space (17);
(2) Stationing power reflectors in space that can passively relay electrical power from Earth-based power plants to Earth-based end users (18); and
(3) Generating solar energy in space and transmitting it to Earth (19). This option appears technologically and economically feasible some time in the 21st century (discussed in depth below). During this stage of STS development, initial proof-of-concept studies might be conducted in orbit.

Space humanization. Prospects for human-oriented industries in space‹such as medical, clinical, and biogenetic research; space sciences; educational centers; hospitals; and the arts‹may become technically viable during the latter part of the second stage of STS development (20). These human industries would depend on the timely and step-by-step developments of the systems and subsystems (described earlier) that are necessary to implement the permanent space occupancy program.

C. 2000 and Beyond: Conducting Large-Scale Space Operations

At the outset of the 21st century, human civilization should be completing a fundamental transition period. If current projections are accurate, humanity should have a permanent presence in near-Earth orbital space. The subsequent development of new space technologies during the post-2000 period should focus on extensions and offshoots of STS; however, in many ways such developments would be as different from the Shuttle orbiter as that vehicle is from the Mercury space capsules of the 1960s. Of course, such 21st-century developments can only be described in basic terms at this time. In many instances, descriptions of future technologies are not the product of systematic NASA advanced planning, but rather of visionary space planners in industry, academia, government, and, in some cases, science fiction writing. Moreover, no attempt is made to fully assess the prospects for post-2000 space development. Instead, a range of technologies and missions are discussed in order to reflect the breadth of options available to space planners and to society as a whole.

An entire new generation of Shuttle-derived orbital transportation vehicles probably will be operational after the year 2000. Researchers have studied and advocated many candidate systems since 1960. Many of the transportation systems differ in terms of number of stages, launch attitude (vertical or horizontal), landing attitude (ballistic or lifting), and landing location (land or water) (21).

Continuing development of new Shuttle generations is spurred by the intrinsic technological advances associated with years of orbital transport experience and by the ever present need to achieve the lowest possible per kilogram cost of transporting people and goods into space. More than one Shuttle-derived orbital transport system may be developed in this period. In one scenario, a single-stage-to-orbit, Shuttle-type craft would ferry people to orbit, while new versions of a heavy lift vehicle would provide low-cost transportation of goods and equipment.

The development of a Moon base may well constitute a significant addition to overall space operations during the 21st century. A lunar base would serve both scientific and industrial purposes. The early return missions to the Moon likely would continue the exploration process begun by the Apollo program, which sampled only six lunar locations. Other potential scientific activities for a lunar base (or bases) focus on optical and radio astronomy. The far side of the Moon represents a desirable location for radio astronomers, because the facilities would be shielded permanently from the radio noise produced by Earth activities. The lunar surface is comparable to free space as an advantageous position for telescope location, in large measure because of the absence of an atmosphere. Scientists at the Jet Propulsion Laboratory are particularly interested in the south pole of the Moon as an optical astronomy site, because the cosmic southern hemisphere is particularly rich in objects of interest to modern astronomy (22). A lunar base also might be useful for X-ray, cosmic ray, and possibly gravity wave observations (23).

Although scientific applications abound for a lunar base, most of the projects probably could be conducted with equal facility at an orbiting space station. Consequently, the potential of the Moon and lunar resources to promote space industrialization and development ultimately would drive the construction of a Moon base. Analyses of surface samples from Apollo missions document that lunar soil contains many of the materials required for construction of solar power satellites, orbital facilities, and even the lunar base itself. The basic constituents of lunar rock include silicon, iron, aluminum, calcium, magnesium, titanium, and oxygen (24). Chemical engineers already are evaluating means of extracting metals from lunar rock and processing them into valuable products (25).

The mineral resources of the Moon may be abundant, and analysts are beginning to understand the process to extract such materials. However, the extent to which these resources would be used to construct space systems depends on the economics of lifting large quantities of materials off the lunar surface. In comparison to Earth, the Moon's weak gravity field (approximately one-sixth that of Earth) constitutes a mining advantage in terms of accessibility and environmental constraints. Yet, a NASA-sponsored Rockwell International study concluded that because most large space systems (especially SPS) still would require materials from Earth‹for example, carbon epoxy, carbon fiber, polyamids‹ "the opportunities for taking advantage of lunar gravity to obtain structural materials appear limited" (26). The Rockwell study foresaw the primary contributions of a lunar base to be supplying oxygen for interorbital propulsion and providing maintenance services for large energy structures.

Current attempts to pinpoint economical and justifiable industrial uses of the Moon during the post-2000 period are probably premature. Specific lunar industrial developments depend on a variety of factors, particularly the extent of near-Earth orbital space development in the pre-2000 period. Krafft Ehricke, a space pioneer on von Braun's Peenemunde team, wrote: A primary advantage of lunar industries is that they offer the option of separating production (elsewhere) from consumption (on Earth) in an industrial civilization where it becomes increasingly difficult to do both indefinitely in the same environment (27).

Lunar bases and industries would be an integral component of post-2000 space development, because‹if for no other reason‹such operations open up a new resource arena for continued economic growth.

Permanent lunar facilities are contingent upon the development of efficient economic transportation between Earth and Moon, and STS can act as the basis for this system. An industrial research group at General Dynamics/ Convair designed a system that would rely on the Shuttle to carry reusable "space tugs" (derived from orbital transfer vehicles) (28). The tugs would be equipped with landing legs and radar for soft landings on the Moon. This system also would incorporate two technologies that are potentially capable of reducing lunar transportation costs by facilitating the manufacture of propellants in orbit. An efficient Earth-to-Moon transportation system also requires a variety of communication satellites in both lunar and terrestrial orbits.

Actual construction of the first Moon base may borrow significantly from terrestrial experiences with scientific bases in Antarctica and industrial outposts on the Alaskan North Slope. However, from the outset a Moon base would demand a higher degree of self-sufficiency than either of these predecessors. Initially, the base would be constructed almost entirely from prefabricated materials brought from Earth, perhaps using unprocessed materials as a radiation shield (29). Power requirements probably would be satisfied from some combination of nuclear fission and solar energy. The high costs of Earth resupply operations would tend to place a premium on recycling various liquids, gases, and solids. Eventually, some percentage of required foodstuffs would be grown in processed lunar soils in a pressurized greenhouse.

The long-range prospects for solar system exploration continue to rely for the most part on robot probes. By the year 2000, initial fly-by reconnaissance of most of the objects of interest within the solar system should be completed. Orbital surveys and landers may be in place around and on many of the planets and several of their moons. Robot probes may conduct advanced analysis and resource mapping of some objects, providing new insights into the origin and evolution of the solar system.

The post-2000 period also may fulfill one of mankind's oldest and most enduring spaceflight goals‹a visit to Mars by humans. In 1953, Dr. Wernher von Braun published a manuscript describing a detailed plan for sending astronauts to Mars (30). Dr. von Braun's proposed expedition included a flotilla of ten vessels assembled in Earth orbit, each staffed by seventy astronauts; the expedition would consume almost three years, with fifty people spending a total of 400 days on Mars. In 1970, NASA outlined a proposed mission to Mars which would begin in 1987 and use two nuclear-powered rockets to carry twelve men and two landing craft on a 600-day mission to the red planet (31). Although NASA has not authorized additional formal assessments of manned Mars missions since the 1970 study, some aerospace experts continue to plan for a Martian mission with the STS as an integral component. British aerospace authority Dr. R.C. Parkinson proposes a mission incorporating adaptations of the Shuttle, an advanced orbital transfer vehicle, Spacelab modules, and a lander module based on the Apollo program lunar module (32). Once on the planet, astronauts would have twenty-five days to conduct detailed explorations and scientific experiments before returning to Earth.

The barriers to mounting a full-scale Martian expedition always have included the sophistication of available technology, the project's economic feasibility vis-a-vis competing national priorities, and the political implications of such a decision. According to some experts, by the 21st century the necessary technology should be in place or readily available. Moreover, some analysts believe that the basic hardware required for the actual mission‹ excluding space technologies that would be developed independently (for example, an orbital transfer vehicle)‹ would cost substantially less than the Apollo program of the 1960s (33). The political feasibility of such a Mars mission is very much a function of the highly variable overall national and international political climate. President Kennedy affirmed the U.S. commitment to land a man on the Moon within a decade barely four months after a contrary decision made at the highest levels of government (34). At some point in the 21st century, the political milieu may favor a new Apollo-type commitment to a manned Martian expedition.

One of the most interesting and far-reaching proposals for the large-scale utilization of space resources suggests locating as many as sixty satellites (each approximately one-half the size of Manhattan Island) in geosynchronous orbit for the purpose of relaying large quantities of solar energy to Earth. Plans for such solar power satellites (SPS) include numerous variations in design, size, location, method of energy transmission, and even construction materials; however, the basic concept of the proposed SPS attempts to capitalize on several space-related advantages over Earth-based energy systems, for example:
(1) A satellite in geosynchronous orbit is exposed to between four and eleven times the solar energy that strikes Earth sites receiving copious sunshine.
(2) In space, solar energy is available almost continuously; only one percent of solar rays are obscured by Earth shadowing. On Earth, clouds and nightfall prevent continuous exposure of solar energy collectors to the Sun.
(3) The space environment, zero gravity, and the absence of wind and rain allow SPS to be built of relatively light materials and to be large in area without incurring the high cost of such structures on Earth.
(4) The environmental effects of such a system are thought to be within acceptable limits (35).

Dr. Peter E. Glaser first proposed SPS in 1968 (36). Since then numerous studies failed to identify any insurmountable technological hurdles which would prevent SPS construction at some future time (37). As with all advanced space systems and technologies, proceeding from paper studies to actual hardware production requires more than a demonstration of technological feasibility. Attendant questions of economic, social, and political viability must be addressed and resolved. A recent study by the National Research Council concluded that although there currently are no known technological barriers to SPS, economic and logistic issues may relegate the concept to the post-2000 time frame (38).

If the preceding stage of space development‹i.e., permanent space stations, large solar power modules for in-orbit use, geosynchronous space platforms, advanced Shuttle-derived heavy lift vehicles, and new orbital transfer vehicles‹is completed by the turn of the century, the next major space goal may well be the provision of nearly unlimited quantities of SPS energy for use on Earth. Once the infrastructure required for orbital construction and manufacturing is well established, the cost of such a program might be reduced substantially.

The prospects for SPS depend heavily on the pace of development for competing Earth-based energy alternatives, such as nuclear fission and fusion, fossil fuels, and terrestrial solar energy. Moreover, the environmental and social implications of all potential energy systems must be evaluated. In the long term, SPS may represent the optimal mix of renewability, environmental acceptability, and economic feasibility for a permanent source of electrical energy for Earth.

Another proposal to utilize space resources advocates the use of nonterrestrial mineral resources in the construction of many of the advanced space systems and technologies already discussed (39). Some experts even foresee a time when the mineral resources of the solar system (especially the Moon and the asteroids) are transported to the Earth's surface in large quantities to replace depleted supplies of valuable commodities such as copper, nickel, and iron (40).

The space program and astronomical discoveries to date document the vastness of the mineral resources of the solar system. Analyzing asteroidal spectral data, one research team determined that a single asteroid's gross economic value could total as much as $5 trillion, with the nickel content providing a millenia's supply at present terrestrial consumption rates (41). Although these figures are admittedly simplistic, they do indicate the potential inherent in mining the mineral resources of the solar system for use in space and, eventually, on Earth as well.

Preliminary studies concentrated largely on procedures for mining and processing lunar materials and have done much to establish the technological feasibility of such systems in the long run. A limited number of studies suggest that nonterrestrial materials may offer distinct economic advantages in the construction of space manufacturing centers and solar power satellites (42).

Clearly the future uses of space probably will be limited not by technical feasibility, but rather by societal budgetary constraints. A recent NASA study group recognized that: . . . the cost of space operations, even if transportation came free, makes many intriguing large scale enterprises so expensive that they will nor likely gain approval in any foreseeable environment. [The study group sought to] see if such projects would become more practical through machines which use the energy and material resources available in space to reproduce themselves, creating a quickly increasing number of identical self-replicating factories that then would produce the finished machinery or product (43).

Such a concept (labelled telefactors by the study group) offers the possibility that large-scale space projects may at some time become essentially self-financing after the initial investments in a self-replicating system. The study group considered this revolutionary concept to be both theoretically and technically feasible, although the group noted that "such systems for space use would come as the end product of a long process of developing automation, robotics, and machine intelligence" (44).

Of course, such a system raises numerous social and economic implications. Indeed, the mere fact that scientists already can suggest the initial parameters of a self-replicating machine capable of large-scale space manufacturing and production emphasizes the necessity of conducting comprehensive social analyses of proposed space systems well in advance of actual decisions to implement such technologies. The future pace and direction of the space program probably will not be limited solely by technological and economical feasibility. The social science community should provide sound and relevant data to be incorporated into the design and operation of space systems.

Appendix One supplies information on obtaining supplemental teaching materials relevant to space technologies.


1. Jesco von Puttkamer. "The Industrialization of Space: Transcending the Limlts to Growth." The Futurist. Vol. 13, No. 3, June 1979, pp. 192-201.

2. Ivan Bekey and John E. Naugle. "Just Over the Horizon in Space." Astronautics and Aeronoutics. May 1980, p. 65.

4. See footnote 1, p. 197.

5. Rockwell International. "Space Industrialization: Port I Final Briefing." NAS8-32198, July 7, 1977, p. 127.

6. See footnote 5. Also: Science Applications, Inc. "Space Industrialization: An Overview. Final Report, Vol. 1. NAS8-32197, April 15, 1978; The Aerospace Corporation. "Preliminary Definition and Evaluation of Advanced Space Concepts." NASW 3030, Vol. 1, June 30, 1978.

7. See footnote 6, Science Applications, Inc., p. 10.

8. See footnote 1, p. 195.

9. See footnote 8.

10. See footnote 5.

11. Charles K. Paul. "Satellites and World Food Resources." Technology Review. October 1979, pp. 18-29.

12. National Aeronautics and Space Administration. "Outlook for Space." January 1976, pp. 68-80.

13. See footnote 12, pp. 77-78.

14. See footnote 13.

15. See footnote 1, p. 195.

16 See footnote 15.

17. Time. "Nuclear Dump in the Heavens." June 2, 1980, p. 72.

18. Krafft A. Ehricke. "The Extraterrestrial Imperative." Futures. April 1981, pp. 111-12.

19. G.M. Hanley. "Space Shuttle and Solar Power Satellite Systems." In: "Update on Space." Granada Hills, CA: National Behavior Systems, 1981.

20. See footnote 1, pp. 200-201.

21. Robert Salkeld, Donald W. Patterson, and Jerry Grey (eds). "Space Transportation Systems." New York: American Institute of Aeronautics and Astronautics, 1978.

22. Kenneth Gatland (ed). "Space Technology: A Comprehensive History of Space Exploration." New York: Harmony Books, 1981, p. 240.

23. See footnote 12, p. 175.

24. See footnote 18.

26. See footnote 5, p. 113.

27. Krafft A. Ehricke. "The Extraterrestrial Imperative." In: "Update on Space." Granada Hills, CA: National Behavior Systems, 1981, p. 168.

28. See footnote 22, pp. 238-39.

29. See footnote 12, p. 174.

30. Wernher von Braun. "The Mars Project." Urbana, Illinois: University of Illinois Press, 1953.

31. For a detailed account, see: John M. Logsdon. "The Policy Process and Large Scale Efforts." The Space Humanization Series. Vol. 1, 1979, pp. 65-80.

32. R.C. Parkinson. "Mars in 1995?" Analog. June 22, 1982, pp. 38-49.

33. See footnote 32.

34. John M. Logsdon. "The Decision to Go to the Moon: Project Apollo and the National Interest." Chicago: University of Chicago Press, 1972.

35. Peter E. Glaser. "Solar Power From Satellites." Physics Today. February 1977, p. 30.

36. Peter E. Glaser. "Power from the Sun: Its Future." Science. November 22, 1968, pp. 857-61.

37. U.S. Department of Energy. "Program Assessment Report Statement of Findings, Satellite Power Systems Concept Development and Evaluation Program." DOE/ER-0085, November 1980.

38. Robert C. Cowen. "A Sun-Power Satellite? Not Likely in this Century." The Christian Science Monitor. August 5, 1981, p. 16.

39. Brian O'Leary. "Mining the Apollo and Amor Asteroids." Science. July 22, 1977, pp. 363-65.

40. Michael J. Gaffey and Thomas B. McCord. "Mining Outer Space." Technology Review. June 1977, pp. 51-64.

41. See footnote 40, p. 52.

42. David R. Criswell and Robert D. Waldron. "Commercial Prospects for Extraterrestrial Materials." Journal of Contemporary Business. Vol. 7, No. 3, pp. 153-69.

43. See footnote 2, pp. 75-76.

44. See footnote 43.

Appendix One

Space Technologies - Resources

NASA provides a variety of education services for teachers, students, schools, and communities. A free pamphlet describing these services is available from: William D. Nixon, Code LFC-9, NASA Headquarters, Washington, D.C. 20546, (Educational Services).

NASA also offers a variety of films, film strips, and audiotapes that can be borrowed by educational, civil, industrial, professional, youth, and similar groups. A pamphlet describing audio/visual materials is available from the same source as above.

Additionally, the "Education Stack" of "The Space Educators Handbook" provides not only the pamphlet described above, but an encyclopedia of space education resources for Macintosh computer users. For this program, contact: Jerry Woodfill, NASA, JSC, IA12, Houston, TX, 77058, 713-283-5364. Diskettes must be provided. (Seven 3.5", Hi-Density).