To energize a discussion of long-range goals and strategies for the civilian space program, four bold initiatives were selected for definition, study, and evaluation:
1.   Mission to Planet Earth: a program that would use the perspective afforded from space to study and characterize our home planet on a global scale.
2. Â Â Â Exploration of the Solar System: a program to retain U.S. leadership in exploration of the outer solar system, and regain U.S. leadership in exploration of comets, asteroids, and Mars.
3.  Outpost on the Moon: a program that would build on and extend the legacy of the Apollo Program, returning Americans to the Moon to continue exploration, to establish a permanent scientific outpost, and to begin prospecting the Moon's resources.
4.  Humans to Mars: a program to send astronauts on a series of round trips to land on the surface of Mars, leading to the eventual establishment of a permanent base.
The intent is not to choose one initiative and discard the other three, but rather to use the four candidate initiatives as a basis for discussion. For this reason, it was important to choose a set of initiatives which spanned a broad spectrum of content and complexity.
The ground rules for this study are important to understand, since they influenced the detailed definition of the initiatives. The ground rules, set forward at the outset of this study, were:
The candidate initiatives were developed and presented to NASA management to: (1) evaluate the initiatives and their implications, and (2) promote a discussion of the attributes of each initiative to determine the elements which are most important to NASA and to the United States.
Each initiative was developed by a separate task group, which discussed the goals, milestones, and elements of the initiative, and then determined the requisite transportation, space facilities, and technologies. For each initiative, an “advocate” was identified to work with appropriate NASA personnel to develop programmatic details. These four advocates presented the strategies, scenarios, requirements, and rationale to senior NASA management.
Two initiatives, Mission to Planet Earth and Exploration of the Solar System, had a body of recent work from which to draw. The 1986 report of the Earth System Sciences Committee of the NASA Advisory Council, Earth System Science: A Program for Global Change, clearly states goals for the future observation of Earth. Two reports by the Solar System Exploration Committee of the NASA Advisory Council similarly articulate goals and recommendations for solar system exploration. Titled Planetary Exploration through Year 2000: Part One: A Core Program, and Part Two: An Augmented Program, these reports outline both a conservative, steady program for solar system exploration and a set of more challenging, exciting missions to be undertaken if resources to do so become available. The other two initiatives, Outpost on the Moon and Humans to Mars, did not have clearly delineated strategies available and no specific organization within NASA was dedicated to their advocacy.
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An Earth-orbiting polar platform.
Mission to Planet Earth is an initiative to understand our home planet, how forces shape and affect its environment, how that environment is changing, and how those changes will affect us. The goal of this initiative is to obtain a comprehensive scientific understanding of the entire Earth System, by describing how its various components function, how they interact, and how they may be expected to evolve on all time scales.
The challenge is to develop a fundamental understanding of the Earth System, and of the consequences of changes to that system, in order to eventually develop the capability to predict changes that might occur—either naturally, or as a result of human activity.
Background
With the launch of the first experimental satellites in the 1960s, NASA pioneered the remote sensing of Earth from space. Over the past two decades, the scientific community has concluded that Earth is in a process of global change, and scientists now believe that it is necessary to study Earth as a synergistic system. As stated in the Earth System Sciences Committee report cited earlier, “Global observations, new space technology, and quantitative models have now given us the capability to probe the complex, interactive processes of Earth evolution and global change.” Interactive physical, chemical, and biological processes connect the oceans., continents, atmosphere, and biosphere of Earth in a complex way. Oceans, ice-covered regions, and the atmosphere are closely linked and shape Earth’s climate; volcanism links inner Earth with the atmosphere; and biological activity significantly contributes to the cycling of chemicals (e. g., carbon, oxygen, and carbon dioxide) important to life. And now it is clear that human activity also has a major impact on the evolution of the Earth System.
Global-scale changes of uncertain impact, ranging from an increase in the atmospheric warming gases, carbon dioxide and methane, to a hole in the ozone layer over the Antarctic, to important variations in vegetation covers and in coastlines, have already been observed with existing measurement capabilities. The potentially major consequences, either detrimental or beneficial, suggest an urgent need to understand these variations.
We currently lack the ability to foresee changes in the Earth System, and their subsequent effects on the planet's physical, economic, and social climate. But that could change; this initiative would revolutionize our ability to characterize our home planet, and would be the first step toward developing predictive models of the global environment.
Strategy and Scenario
The guiding principle behind this initiative is to adopt an integrated approach to observing Earth. The observations from various sensors on platforms and satellites will be coordinated to perform global surveys and also to perform detailed observations of specific phenomena.
Mission to Planet Earth proposes:
1.  To establish and maintain a global observational system in space, which would include experiments and free-flying platforms, in polar, low-inclination, and geostationary orbits, and which would perform integrated, long‑term measurements.
2.  To use the data from these satellites along with in-situ information and numerical modeling to document, understand, and eventually predict global change.
As illustrated in Figure 5, the global observational system would include a suite of nine orbiting platforms:
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Figure 5. Mission to Planet Earth
Low-inclination, low-altitude payloads would also be included in the system. The Earth Radiation Budget Experiment satellite, launched from the Space Shuttle in 1984, and the synthetic aperture radar sensors, SIR-A and SIR-B, flown on the Shuttle in 1981 and 1984, are the types of experiments that would fall into this category. Another example would be a proposed Space Station-attached payload designed to obtain coverage of tropical rainfall with sampling at all local times.
The integrated system would measure, the full complement of the planetÂ’s characteristics, including: global cloud cover, vegetation cover, and ice cover; global rainfall and moisture; ocean chlorophyll content and ocean topography; motions and deformations of Earth's tectonic plates; and atmospheric concentration of gases such as carbon dioxide, methane, and ozone.
Space-based observations would also be coordinated with ground-based experiments and the data from all observations would be integrated by an essential component of this initiative: a versatile, state-of-the-art information management system. This tool is critical to data analysis and numerical modeling, and would enable the integration of all observational data and the development of diagnostic and predictive Earth System models.
This global observational system would be designed to operate for decades, serviced either by astronauts or robotic systems to ensure long life and to provide the continuing data collection, integration, and analysis required by this initiative.
Because of its international and interdisciplinary nature, the Mission to Planet Earth requires the strong support and involvement of other U.S. government agencies (particularly the National Science Foundation and the National Oceanic and Atmospheric Administration) and of our international partners. The roles of the various Federal agencies have been examined in detail by the Earth System Sciences Committee. NASAÂ’s responsibilities would include the information management system and platforms and experiments described previously. Most important, NASA would also provide the supporting technology, space transportation, space support services, and much of the scientific leadership.
Technology, Transportation, and Orbital Facilities
This initiative requires advances in technology to enhance observations, to handle and deliver the enormous quantities of data, and to ensure a long operating life. Sophisticated sensors and information systems must be designed and developed, and advances must be made in automation and robotics (whether platform servicing is performed by astronauts or robotic systems).
To achieve its full scope, this initiative requires the operational support of Earth-to-orbit and space transportation systems to accommodate the launching of polar and geostationary platforms. This does not represent a large number of additional launches, but it does require the capability to launch large payloads to polar orbit; Titan IVs would be used to accomplish this. Since the envisioned geostationary platforms would be lifted to low-Earth orbit, assembled at the Space Station, and then lifted to geosynchronous orbit with a space transfer vehicle well-developed orbital facilities are essential. By the late 1990s, the Space Station must be able to support on-orbit assembly, and a space transfer vehicle must exist.
SUMMARY
NASA, with its technical and scientific expertise, is uniquely suited to lead Mission to Planet Earth. Only from Earth orbit can we gain the perspective necessary to observe the Earth System and the interaction of its components on a global scale. We now understand what to observe, and how to observe it. While we do not yet know how the data will piece together, the resulting Earth System models, developed and refined over years of study, are the important products of this initiative, and would establish NASA as a responsive agency ready to meet the challenge of a genuine time-critical need. Championing this initiative would establish the United States at the forefront of a world recognized need to understand our changing planet.
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The Comet Rendezvous Asteroid Flyby spacecraft
flies in formation with Comet Tempel 2.
EXPLORATION OF THE SOLAR SYSTEM
This initiative would build on NASA's longstanding tradition of solar system exploration and would continue the quest to understand our planetary system, its origin, and its evolution. Solar system bodies are divided into three distinct classes: the primitive bodies (comets and asteroids), the outer (gas giant) planets, and the inner (terrestrial) planets. Each class occupies a unique position in the history of the solar system, and each is the target of a major mission, in this initiative, which includes a comet rendezvous (the Comet Rendezvous Asteroid Flyby mission), a mission to Saturn (Cassini), and three sample return missions to Mars. The centerpiece of the initiative is the robotic exploration of Mars; the first of these three automated missions would bring a handful of Mars back to Earth before the year 2000.
Background
In the 1960s and 1970s, exploration of the solar system was an important and visible component of the U.S. space program. Highly successful missions such as Pioneer, Viking, and Voyager made the United States the unchallenged leader in the exploration of the planets. Our spacecraft were consistently both the first and the best. While the Soviet Union concentrated most of its efforts on the exploration of Venus, the rest of the solar system was left to the United States.
But now almost a decade has elapsed between U.S. planetary missions—the last was Pioneer Venus, launched in 1978. Galileo (to Jupiter), Magellan (to Venus), and the Mars Observer are in line for launch between 1989 and 1992, but no other planetary missions have been approved. Although the successful Voyager missions to the outer planets clearly established U.S. leadership in exploration of the outer solar system, plans for the future beyond the Galileo mission are uncertain.
Other nations have recently begun to undertake innovative and challenging programs (the recent international flotilla to Halley's Comet is an excellent example). The Soviets have announced an ambitious program for the exploration of Mars which will culminate in a sample return mission, and the Europeans have set a long-term goal of returning a sample from a comet. Although currently scheduled U.S. missions will ensure that the United States will remain a leader in certain areas of solar system exploration through 1995, the position of the United States beyond 1995 is in question. This initiative would maintain U.S. leadership in exploration of the outer planets, and would regain and sustain U.S. leadership in the exploration of both the planet Mars and the primitive bodies of the solar system.
Strategy and Scenario
This initiative is based on the balanced strategy developed by the Solar System Exploration Committee of the NASA Advisory Council and elucidated in its two reports (cited previously) describing a Core Program and an Augmented Program for planetary exploration. The missions include:
1. The Comet Rendezvous Asteroid Flyby (CRAF) mission would investigate the beginnings of our solar system, studying a Main Belt asteroid and a comet, which represent the best preserved samples of the early solar system. Because of their primordial nature, comets can provide critical clues about the processes that led to the origin and evolution of our solar system.
The CRAF mission scenario is shown in Figure 6. After a 1993 launch and a six-month cruise, the spacecraft would fly past the asteroid Hestia at an altitude of about 10,000 kilometers. CRAFÂ’s visual and infrared asteroid imaging systems would conduct investigations of HestiaÂ’s surface composition and structure. CRAF would then continue its journey for a rendezvous with a periodic comet, Tempel 2. The spacecraft would maneuver to within 25 kilometers of the comet's nucleus and begin a series of observations, which includes shooting two penetrators into the nucleus itself for detailed in-situ measurements. The spacecraft would fly in close formation with the comet until it nears the Sun and becomes active; then the spacecraft would maneuver farther away to observe the comet's coma and tail.
2. The Cassini mission would explore Saturn and its largest moon, Titan. The giant outer planets offer us an opportunity to address key questions about their internal structures and compositions through detailed studies of their atmospheres. Titan is an especially interesting target for exploration because the organic chemistry now taking place there provides the only planetary-scale laboratory for studying processes that may have been important in the prebiotic terrestrial atmosphere.
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Figure 6. The Comet Rendezvous Asteroid Flyby Mission
Figure 7. The Cassini Mission
The Cassini mission proposed in this initiative would be a considerably expanded version of the Cassini mission considered by the Solar System Exploration Committee. (Figure 7 shows the scenario for the baseline version of Cassini.) This expanded mission would be launched in 1998 for the long interplanetary voyage to arrive at Saturn in 2005 with a full array of investigative instruments. An orbital spacecraft and three probes would conduct a comprehensive three-year study of the planet and its rings, satellites, and magnetosphere. One atmospheric probe would be launched toward Titan. The expanded Cassini mission would also carry one probe to investigate the Saturnian atmosphere, and one semi-soft lander which would reach the surface of Titan.
3.  The Mars Rover/Sample Return missions would, in journeys covering hundreds of millions of miles, gather samples of Mars and bring them back to Earth. Because of its relevance to understanding Earth and other terrestrial planets, and because it is the only other potentially habitable planet in our solar system, Mars is an intriguing target for exploration. The Mars Rover/Sample Return mission scenario is shown in Figure 8. It would involve a soft landing on the Martian surface, deployment of a "smart" surface rover to select and collect samples delivery of the samples to an ascent vehicle, and transfer of the samples from Mars orbit to a return vehicle. The samples would then most likely be returned to a sample handling module on the Space Station for analysis. The initiative would include three such missions: two launched in 1996, probably sending redundant rovers and ascent vehicles to ensure return of a sample in 1999, and one launched in 1998/99 with return in 2001.
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Figure 8. The Mars Rover/Sample Return Mission
Technology, Transportation, and Orbital Facilities
As it is defined, this initiative places a premium on advanced technology and enhanced launch capabilities to maximize the scientific return. It requires aerobraking technology for aerocapture and aeromaneuvering at Mars, and a high level of sophistication in automation, robotics, and sampling techniques. Advanced sampling methods are necessary to ensure that geologically and chemically varied and interesting samples are collected for analysis.
The Solar System Exploration initiative significantly benefits from improved launch capability in terms of the science returned from both the Mars and the Cassini missions. In fact, it is a heavy-lift launch vehicle that enables the full complement of three different probes to be carried in the expanded Cassini mission.
The Space Shuttle is not required for any of the missions in the initiative. The Space Station would not be needed until 1999, when an isolation module may be used to receive the Martian samples.
Summary
This initiative adopts the broad strategy devised by the Solar System Exploration Committee for a balanced, systematic program of solar system exploration. Spacecraft would be sent to a comet (Tempel 2), an outer planet (Saturn), and an inner planet (Mars), to study representatives of each of-the three distinct classes of solar system bodies in exquisite detail. The U.S. would take a bold step forward in the exploration of Mars and we would continue our leadership in exploration of the outer solar system. The scientific return over the next two decades would complement the outstanding solar system exploration program of the 1960s and 1970s and would offer additional insights into the evolution of our Earth and the solar system.
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This initiative builds on the legacy of Apollo and envisions a new phase of lunar exploration and development—a phase leading to a human outpost on another world. That outpost would support scientific research and exploration of the Moon's resource potential, and would represent a significant extraterrestrial step toward learning to live and work in the hostile environments of other worlds.
Beginning with robotic exploration in the 1990s, this initiative would land astronauts on the lunar surface in the year 2000, to construct an outpost that would evolve in size and capability and would be a vital, visible extension of our capabilities and our vision.
Background
The Apollo Program was a great national adventure. We sent explorers to scout the cratered highlands and smooth maria of the Moon, and to bring samples collected on their trips back to laboratories on Earth. The world was fascinated by the Apollo missions and the information they obtained, and the samples provided scientists many exciting clues about the Moon's origin and chemical composition.
The Apollo era ended 15 years ago, before we could fully explore the promise of lunar science and lunar resources. But we learned that human beings can work on the surface of the Moon, and we laid the technical foundation to develop the scientific and engineering tasks for the next stages of exploration. This initiative would send the next generation of pioneers—to pitch their tents, establish supply lines, and gradually build a scientifically and technically productive outpost suitable for long-term habitation.
This initiative represents a sustained commitment to learn to live and work in space. As our experience and capabilities on the lunar surface grow, this extraterrestrial outpost will gradually become less and less dependent on the supply line to Earth. The first steps toward “living off the lunar land” will be learning to extract oxygen from the lunar soil, where it is plentiful, and learning to make construction materials. The lunar soil would eventually be a source of oxygen for propellant and life-support systems, and a source of material for shelters and facilities.
The MoonÂ’s unique environment provides the opportunity for significant scientific advances; the prospect for gains in lunar and planetary science is abundantly clear. Additionally, since the Moon is seismically stable and has no atmosphere, and since its far side is shielded from the radio noise from Earth, it is a very attractive spot for experiments and observations in astrophysics, gravity wave physics, and neutrino physics, to name a few. It is also an excellent location for materials science and life science research because of its low gravitational field (one-sixth of EarthÂ’s).
Strategy and Scenario
This initiative proposes the gradual, three-phase evolution of our ability to live and work on the lunar surface.
Phase I: Search for a Site (1990s)
The initial phase would focus on robotic exploration of the Moon. It would begin with the launching of the Lunar Geoscience Observer, which will map the surface, perform geochemical studies, and search for water at the poles. Depending on the discoveries of the Observer, robotic landers and rovers may be sent to the surface to obtain more information. Mapping and remote sensing would characterize the lunar surface and identify appropriate sites for the outpost. The discovery of water or other volatiles would be extremely significant, and would have important implications for the location of a habitable outpost.
Phase II: Return to the Moon (2000-2005)
Phase II begins with the return of astronauts to the lunar surface. (The scenario is sketched in Figure 9.) The initiative proposes that a crew be transported from the Space Station to lunar orbit in a module propelled by a lunar transfer vehicle. The crew and equipment would land in vehicles derived from the transfer vehicle. Crew members would stay on the surface for one to two weeks, setting up scientific instruments, a lunar oxygen pilot plant, and the modules and equipment necessary to begin building a habitable outpost. The crew would return to the orbiting transfer vehicle for transportation back to the Space Station.
Over the first few flights, the early outpost would grow to include a habitation area, a research facility, a rover, some small machinery to move lunar soil, and a pilot plant to demonstrate the extraction of lunar oxygen. By 2001, a crew could stay the entire lunar night (14 Earth days), and by 2005.the outpost would support five people for several weeks at a time.
Phase III: At Home on the Moon (2005-2010)
Phase III evolves directly from Phase II, as scientific and technological capabilities allow the outpost to expand to a permanently occupied base. The base would have closed-loop life-support systems and an operational lunar oxygen plant, and would be involved in frontline scientific research and technology development. The program also requires the mobilization of disciplines not previously required in the space program: surface construction and transportation, mining, and materials processing.
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Figure 9. Return to the Lunar Surface:
Piloted Sortie, Expendable Lander
By 2010, up to 30 people would be productively living and working on the lunar surface for months at a time. Lunar oxygen will be available for use at the outpost and possibly for propellant for further exploration.
Technology, Transportation, and Orbital Facilities
This initiative envisions frequent trips to the Moon after the year 2000—trips that would require a significant investment in technology and in transportation and orbital facilities in the early 1990s.
The critical technologies for this initiative are those which would make human presence on the Moon meaningful and productive. They include life-support system technologies to create a habitable outpost; automation and expert systems and surface power technologies to make the outpost functional and its inhabitants productive; and lunar mining and processing technologies to enable the prospecting for lunar resources.
The transportation system must be capable of regularly transporting the elements of the lunar outpost, the fuel for the voyage, and the lunar crew to low-Earth orbit. This requires a heavy-lift launch vehicle and a healthy Space Shuttle fleet. The transfer of both cargo and crew from the Space Station to lunar orbit requires the development of a reusable space transfer vehicle. This and a heavy-lift launch vehicle will be the workhorses of the Lunar initiative.
The Space Station is an essential part of this initiative. As the lunar outpost evolves, the Space Station would become its operational hub in low-Earth orbit. Supplies, equipment, and propellants would be marshalled at the Station for transit to the Moon. It is therefore required that the Space Station evolve to include spaceport facilities.
In the 1990s, the Phase I Space Station would be used as a technology and systems test bed for developing closed-loop life-support systems, automation and robotics, and the expert systems required for the lunar outpost. The outpost would, in fact, rely on the Space Station for many of its systems and subsystems, including lunar habitation modules which would be derivatives of the Space Station habitation/ laboratory modules.
Summary
This initiative represents a conceptual leap outward from Earth. The challenge is to tame and harness the space frontier—to go beyond Apollo, and explore the Moon for what it can tell us, and what it can offer us, as a research and development; center and as a resource in itself. Exploring, prospecting, and settling are parts of our heritage and will most assuredly be parts of our future.
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This bold initiative is committed to the human exploration, and eventual habitation, of Mars. Robotic exploration of the planet would be the first phase and would include the return of samples of Martian rocks and soil. Early in the 21st Century, Americans would land on the surface of Mars; within a decade of these first piloted landings, this initiative would advance human presence to an outpost on Mars.
Background
The Red Planet has piqued our curiosity and stimulated our imaginations for decades. Our previous exploration of Mars has revealed a fascinating world of enormous mountains and deep canyons, and a surface etched by erosion during ancient floods. Mars may once have supported life; in any case, it is the only potentially habitable planet in our solar system besides Earth.
America has led the way in humanity's exploration of the worlds beyond our own planet. We have sent spacecraft to the outer reaches of the solar system, and our emissaries have walked on the surface of the Moon. The Humans to Mars initiative would greatly increase our understanding of the solar system, and would push the frontier of human presence ever further beyond the confines of Earth.
The United States has also led the way in the robotic exploration of Mars. The last visitor to that planet was the extremely successful Viking spacecraft, which landed on the Martian surface in 1976, and transmitted data to Earth until late in 1982. During the coming decade, humanity will learn more about Mars, but it will largely be the result of ambitious Soviet, not American, programs. Our single mission to Mars, the Mars Observer, to be launched in 1992, is a small spacecraft which will perform an important geochemical characterization of Mars while in orbit around the planet. Meanwhile, the Soviets have announced three separate missions to Mars before 1995, and the possibility of a sample return mission in the late 1990s.
This leadership initiative declares America’s intention to continue exploring Mars, and to do so not only with spacecraft and rovers, but also with humans. It would clearly rekindle the national pride and prestige enjoyed by the U.S. during the Apollo era. Humans to Mars would be a great national adventure; as such, it would require a concentrated massive national commitment—a commitment to a goal and its supporting science, technology, and infrastructure for many decades.
Strategy and Scenario
This initiative would:
1.  Carry out comprehensive robotic exploration of Mars in the 1990s. The robotic missions would begin with the Mars Observer, include an additional Observer mission, and culminate in a pair of Mars Rover/Sample Return missions. These missions would perform geochemical characterization of the planet, and complete global mapping and support landing site selection and certification.
2.  Establish an aggressive Space Station life sciences research program to validate the feasibility of long-duration spaceflight. This program would develop an understanding of the physiological effects of long-duration flights, of measures to counteract those effects, and of medical techniques and equipment for use on such flights. An important result would be the determination of whether eventual Mars transport vehicles must provide artificial gravity.
3.  Design, prepare for, and perform three fast piloted round-trip missions to Mars. These flights would enable the commitment, by 2010, to an outpost on Mars.
The Mars missions described in this initiative are one-year, round-trip “sprints,” with astronauts exploring the Martian surface for two weeks before returning to Earth. The chosen scenario significantly reduces the amount of mass which must be launched into low-Earth orbit, and by doing so brings a one-year round trip into the realm of feasibility. This is accomplished by splitting the mission into two separate parts—a cargo vehicle and a personnel transport—and judiciously choosing the launch date for each.
The Mars cargo vehicle minimizes its propellant requirements by taking a slow, low-energy trip to Mars. The vehicle would be assembled in low-Earth orbit and launched for Mars well ahead of the personnel transport, and would carry everything to be delivered to the surface of Mars plus the fuel required for the crew's trip back to Earth (Figure 10).
The personnel transport would be assembled and fueled in low-Earth orbit, and would leave for Mars only after the cargo vehicle had arrived in Mars orbit. It would carry a crew of six astronauts, crew support equipment, and propellant for the outbound portion of the trip (Figure 11). Once in Mars orbit, it would rendezvous with the cargo vehicle, refuel, and prepare for descent to the surface. The landing party would spend 10 to 20 days on the Martian surface, and then rerendezvous with the personnel transport for the trip back to Earth orbit (Figure 12). Recovery in Earth orbit would return the crew to a Space Station rehabilitation facility (Figure 13). The round-trip time for this scenario is approximately one year.
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Figure 10. Piloted Mars Sprint Scenario—Split Mission Option:
Earth-Orbital Cargo Flight Operations
Figure 11. Piloted Mars Sprint Scenario—Split Mission Option:
Earth-Orbital Cargo Flight Operations
The initiative proposes three of these sprint missions, the third around the year 2010. By the second decade of the 21st Century, the U.S. would have the knowledge, the experience, and the technology base to begin developing an outpost on Mars.
Technology, Transportation, and Orbital Facilities
A significant, long-term commitment to developing several critical technologies and to establishing the substantial transportation capabilities and orbital facilities is essential to the success of the Mars initiative. The Mars expeditions require the development of a number of technologies, including aerobraking (which significantly reduces the amount of mass which must be lifted to low-Earth orbit), efficient interplanetary propulsion, automation and robotics, storage and transfer of cryogenics in space, fault-tolerant systems, and advanced medical technology. Technology development must be initiated immediately to support the timetable of this scenario.
Even with separate cargo and personnel vehicles, and technological advances such as aerobraking, each of these sprint missions requires that approximately 2.5 million pounds be lifted to low-Earth orbit. (In comparison, the Phase 1 Space Station is projected to weigh approximately 0.5 million pounds.) It is clear that a robust, efficient transportation system, including a heavy-lift launch vehicle, is required. The complement of launch vehicles must be able to lift the cargo and personnel required by the sprint missions to the Space Station in a reasonable period of time. Like the outpost on the Moon, this initiative requires a substantial investment in launch systems, for transport of both cargo and crew.
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Figure 12. Piloted Mars Sprint Scenario—Split Mission Option:
Mars-Orbital/Surface Operations
The Phase 1 Space Station is a crucial part of this initiative. In the 1990s, it must support the critical life sciences research and medical technique development. It will also be the technology test bed for life-support systems, automation and robotics, and expert systems.
Furthermore, we must develop facilities in low-Earth orbit to store large quantities of propellant, and to assemble large vehicles. The Space Station would have to evolve in a way that would meet these needs.
Summary
This initiative would send representatives of our planet to Mars during the first decade of the 21st Century. These emissaries would begin a phase of human exploration and reconnaissance that would eventually lead to the establishment of a permanent human presence on another world.
A successful Mars initiative would recapture the high ground of world space leadership and would provide an exciting focus for creativity, motivation, and pride of the American people. The challenge is compelling, and it is enormous.
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Figure 13. Piloted Mars Sprint Scenario—Split Mission Option:
Earth Recovery Operations