Each of the initiatives described in the previous section is a worthwhile program. Although each has something different to offer, each falls within the framework of NASAs vision, each builds on and extends existing capabilities, and each elicits the reaction, America ought to be doing this. In the absence of fiscal and resource constraints, the United States would undoubtedly adopt all four. In the presence of those very real constraints, and the additional constraints imposed by the current state of our civilian space program, this course of action is not possible.
In its desire to revitalize the civilian space program, NASA must avoid the trap identified by the Rogers Commission during its investigation of the Challenger accident: The attitude that enabled the agency to put men on the moon and to build the Space Shuttle will not allow it to pass up an exciting challengeeven though accepting the challenge may drain resources from the more mundane (but necessary) aspects of the program. The Commission further observed (in reference to the Shuttle flight rates): NASA must establish a realistic level of expectation, then approach it carefully.
To establish a realistic level of expectation, NASA must consider the current condition of the space program, its strengths and limitations, and its capabilities for growth. Any bold initiative has to begin with and then build on todays space program, which unfortunately lacks some fundamental capabilities. For example, our most critical commodity, Earth-to-orbit transportation, is essential to each of the initiatives. But the Space Shuttle is grounded until at least June of 1988, and when it does return to flight status, the flight rate will be considerably lower than that projected before the Challenger accident (a four-Shuttle fleet is estimated to be capable of 12 to 14 flights per year).
In hindsight, it is easy to recognize that it was a crippling mistake to decree that the Space Shuttle would be this countrys only launch vehicle. Several studies since the Challenger accident have recommended that the civilian space program include expendables in its fleet of launch vehicles. This strategy relieves some of the burden from the Shuttle, gives the country a broader, more flexible launch capability, and makes the space program less vulnerable in the event of an accident.
The problem of limited launch capability or availability will be magnified during the assembly and operation of the Space Station. Currently, NASA plans to use only the Space Shuttle to transport cargo and people to and from the Space Station. This places a heavy demand on the Shuttle (six to eight flights per year), but more important, it makes the Space Station absolutely dependent on the Shuttle. If Shuttle launches should be interrupted again in the mid-1990s, this nation must still have access to space and the means to transport cargo and people to and from the Space Station. The importance of this capability was emphasized by the National Commission on Space in its report, Pioneering the Space Frontier: Above all, it is imperative that the US maintain a continuous ability to put both humans and cargo into orbit.
TRANSPORTATION REQUIREMENTS
NASA transportation needs for the 1990s, and beyond received considerable attention from the task group and committees examining agency goals and future program thrusts. The consensus of their findings is that if the Nation is to open a "Highway to Space," we must regain regular and assured access to space and expand launch capacity based on expendable and reusable vehicles.
NASA should, on a most urgent basis, initiate a program to incorporate a diversified family of expendable launchers into its space flight program, to include a heavy-lift ELV. Payloads should be off-loaded from shuttle onto ELVs wherever possible. Report of the Task Force on Issues of a Mixed Fleet, 1987
The U.S. should continue to expand its launch capacity based on a mixed fleet of expendable and reusable launch vehicles to preclude total reliance on any one launch system, so that the present manned and unmanned launchers will remain operationally healthy until the next generation of vehicles is fully developed. U.S. Civil Space Program: An AIAA Assessment, 1987
The use of a mixed launch fleet will humans to fly when they are needed on a mission and allow unmanned vehicles to be the carrier of choice for other missions... Diversity will also allow a better matching of the scientific requirements of a mission with the launch capability needed to meet those requirements, rather than forcing the mission to meet the constraints of a single inflexible launch system. The Crisis in Space and Earth Science, 1986
The shuttle fleet will become obsolescent by the turn of the century. Reliable, economical launch vehicles will be needed to provide flexible, routine access to orbit for cargo and passengers at reduced costs ... to reduce space operation costs as soon as possible, the Commission recommends that three major space transport needs be met in the next 15 years: cargo transport to low Earth orbit; passenger transport to and from low Earth orbit; and round-trip transfer beyond low Earth orbit. Pioneering the Space Frontier, 1986
From now until the mid-1990s, Earth-to-orbit transportation is NASAs most pressing problem. A space program that cant get to orbit has all the effectiveness of a navy that cant get to the sea. America must develop a cadre of launch vehicles that can first meet the near-term commitments of the civilian space program and then grow to support projected programs or initiatives.
Expendable launch vehicles should be provided for payloads which are not unique to the Space Shuttlethis is required just to implement current plans and to satisfy fundamental requirements.
A Shuttle-derived cargo vehicle should be developed immediately. A Shuttle-derived vehicle is attractive because of its lift capacity, its synergism with the Space Transportation System, and its potential to be available for service in the early 1990s. This cargo vehicle would reduce the payload requirements on the Shuttle for Space Station support and would accelerate the Space Station assembly sequence.
The United States should also seriously consider the advisability of a crew-rated expendable to lift a crew capsule or a logistics capsule to the Space Station. The logistics vehicle, for Space Station resupply and/or instrument return, would be developed with autodocking and precision reentry capabilities. The crew capsule would carry only crew members and supplies, would launch (with or without a crew) on the expendable vehicle, would have autodocking capability, and might also be used for crew rescue.
TECHNOLOGY
Rebuilding the Nations technology essential for the successful achievement of any long-tem space goal. It is widely that we are living off the interest of the era technology investment, and that it is to replenish our technology reservoir in to enhance our range of technical option.
The Nation has allowed its technology to erode, leaving it with little cap move out in new directions should the arise. Letter from Daniel J. Fink (Chairman, NASA Advisory Council) to James Fletcher, dated August 14, 1986
Space technology advancement unlies any comprehensive future space activity. The present course is a status-quo caretaker path with no potential growth. New commitments are called for in key technologies such as propulsion, automation and robotics, flight computers, information systems, sensors, power generation, materials, structures, life support systems, and space processing. We support the recommendation by the National Commission on Space for a three-fold increase in this relatively low-budget but extremely important area of space technology. advancement, especially in view of strong foreign commitments to such technology development. U.S. Civil Space Program: An AIAA Assessment, 1987
Research must be pursued on a broad front, to identify and quantify technical possibilities before their usefulness can be judged. Such a research and technology program is therefore properly conceived as opportunity generating, not directed toward applications. Pioneering the Space Frontier, 1986
These transportation capabilities are required just to launch, assemble, operate, and safely inhabit the Space Station, and to have some prospect of being able to support future initiatives.
Without sound, reliable Earth-to-orbit transportation available to lift sensors, spacecraft, scientists, and explorers to orbit, we will not be in a position to aggressively pursue either science or exploration. We have stated that transportation is not our goalbut it is essential to the successful pursuit of whatever goals we choose. If we do not make a commitment now to rebuild and broaden our launch capability, we will not have the option of pursuing any of the four initiatives described in the previous section.
The same can be said for advanced technology. The National Commission on Space observed that NASA is still living on the investment made [during the Apollo era], but cannot continue to do so if we are to maintain United States leadership in space. Several recent studies concur, concluding that our technology base has eroded and technological research and development are underfunded. The technology required for bold ventures beyond Earth's orbit has not yet been developed, and until it is, human exploration of the inner solar system will have to wait.
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Technologies explored by Project Pathfinder.
Project Pathfinder has been developed by NASAs Office of Aeronautics and Space Technology in conjunction with experts on the Lunar and Mars initiatives. Pathfinder would provide the technologies to enable bold missions beyond Earths orbit: technology for autonomous systems and robotics, for lunar and planetary advanced propulsion systems, and for extraction of useful materials from lunar or planetary sources. It also deals in a significant way with the human ability to live and work in space, by developing technologies for life-support systems and the human/machine interface. Until advanced technology programs like Project Pathfinder are initiated, the exciting goals of human exploration will always remain 10 to 20 years in the future.
Life sciences research is also critical to any programs involving relatively long periods of human habitation in space. Because the focus of our life sciences research for the last several years has been on Space Shuttle flights, which only last for five to ten days, there has been no immediate need for a program to study the physiological problems associated with longer flights. Without an understanding of the long-term effects of weightlessness on the human body, our goal of human exploration of the solar system is severely constrained.
Before astronauts are sent into space for long periods, research must be done to understand the physiological effects of the microgravity and radiation environments, to develop measures to counteract any adverse effects, and to develop medical techniques to perform routine and emergency health care aboard spacecraft.
Project Pacer, developed by NASAs Office of Space Science and Applications, is a focused program designed to develop that understanding and provide the physiological and medical foundation for extended spaceflight. This research would be conducted in laboratories and on Space Shuttle missions in preparation for the critical long-term experiments to be conducted on the Space Station.
Until the Space Station is occupied, and actual long-duration testing is begun, we will lack the knowledge necessary to design and conduct piloted interplanetary flights or to inhabit lower-gravity surface bases. Although the research conducted prior to the occupation of Space Station cannot provide definitive answers to several key questions, it is an essential precursor to the research and technology development on the Space Station.
LIFE SCEINCES RESEARCH
The prospect of an extended human presence in space on the Space Station and tended missions to the Moon or Mars requires a commitment to better understand and respond to, biomedical, psychological, and human engineering challenges. Although there is great confidence that we win eventually establish a presence on other bodies in the solar system, there remains uncertainty in the medical community about the implications of such journeys for human health, safety, and productivity. A number of recent studies highlight concerns and identify areas requiring additional research.
Space medicine is unique in the context of the other space sciences primarily because, in addition to questions of fundamental interest, there is a need to address those issues that are more of a clinical or human health and safety nature ... if this country is committed to a future of humans in space, particularly for long periods of time, it is essential that the vast number of uncertainties about the effects of microgravity on humans and other living organisms be recognized and vigorously addressed. Not to do so would be imprudent at best quite possibly, irresponsible. A Strategy for Space Biology and Medical Science, 1987
Many crucial issues in the three major areas of health, life support, and operational capabilities remain to be resolved before the safety of humans working in space over months and years can be assured. Certain aspects of physiological adaption to microgravity may be life-threatening, especially over the long-term Areas such as medical care, radiation protection, environmental maintenance, and human productivity are equally serious, but the research and development activities associated with these areas have at least begun on a modest scale. To neglect any of these areas could risky, and parallel research activities commended. Advanced Missions Humans in Space, 1987
Of paramount practical importance are human safety and performance. Long-duration flights on the Space Station will increase our understanding of the effects of the space environment on people and other living systems. Problems of bone demineralization and loss of muscle mass persist, and effective empirical solutions are unlikely to be found soon It is imperative that basic research on this problem continue, both on the ground and in space. Pioneering the Space Frontier, 1986
Both technology development and life sciences research are pacing elements in human exploration.
The four initiatives represent widely varying levels of complexity and commitment. As part of the development and evaluation of the initiatives, an assessment was performed to estimate their relative complexities and therefore their relative impacts on the agency and its resources. The initiatives, and results from related studies, were reviewed to identify the required technology, transportation, on-orbit facilities, and precursor science. This assessment yielded the elements comprising each initiative the building blocks of that initiative.
The assessment sought to define the initiatives to a reasonable level of detail through 2010. At this time, the initiatives would be in different stages of development. All Earth observing platforms would be in space with their observing systems operating; they would be serviced periodically, and would continue to transmit data to Earth for years. The final mission of the Planetary initiative would be complete; this initiative is not defined past 2010. The Lunar outpost would be well established, with most surface elements developed and delivered; it would receive continuing logistics support, but would be somewhat self sustaining, and have considerable potential for growth and for support of further exploration activities. In 2010, the nation's Mars program would have just finished its human reconnaissance phase, and would be prepared to embark on the establishment of an outpost.
To provide a common starting point for each initiative, this analysis assumed the currently planned NASA space program as a foundation. That is, each initiative must be built from the foundation of a fleet of four Space Shuttles and a Phase I Space Station; everything else that would have to be added to accomplish the initiative, including additional Space Station modules, new transportation elements, unscheduled precursor science missions, etc., was assumed to be part of that initiative.
Some of the elements of each initiative would be developed solely for that initiative; many others could be common to other initiatives as well. An example of the former is the lunar oxygen plant designed to extract oxygen from the lunar soil. Although similar technologies might eventually be needed at a Mars outpost, the element itself exists only in the Lunar initiative. An example of an element which could be common to several programs is the space transfer vehicle of the Earth initiative. Although it would lift geostationary platforms from the Space Station to their final orbit, this vehicle could also be used to deliver other cargo (unrelated to the Earth initiative) to geosynchronous orbit, or it could be the basis of a lunar transfer vehicle. Each initiative has elements which could be common to other programs, as well as initiative specific elements.
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Table 1. Transportation Requirements for the Initiatives
An overview of the transportation elements required for the initiatives is shown in Table 1. The Earth and Planetary initiatives make the most modest demands on transportation, in terms of both essential new capabilities and frequency of use. But each of the initiatives requires an Earth-to-orbit transportation system comprised of more than just a Space Shuttle fleet.
A heavy-lift launch vehicle is either enabling, or significantly enhancing, to all the initiatives. A Shuttle-derived vehicle would have sufficient capacity for the Earth and Planetary initiatives. It would also satisfy the requirements of the Mars and Lunar initiatives through the 1990s, although shortly after the turn of the century both would need a vehicle with a lift capacity of 150,000 to 200,000 pounds. This higher lift capacity is needed primarily to supply the large amounts of propellant required for each initiative (about 2.2 million pounds to low-Earth orbit for each Mars sprint mission; 200,000 pounds to low-Earth orbit for each lunar trek).
SPACE STATION EVOLUTION
The Phase 1 Space Station will be a permanently staffed laboratory in space by 1996. Other capabilities, such as an assembly station or a fueling depot, will not be included in the initial phase, but could be accommodated later if a need for those functions is clearly identified.
A key question for the not-too-distant future is How should the Space Station evolve? Since the Space Station is a means to pursue our goals, the answer depends on what those goals are. It is important to understand what each initiative demands of the Space Station. For example, the Planetary initiative makes few demands on the Space Station; the Mars initiative makes substantial demands.
NASAs Office of Space Station has set up a Strategic Plans and Programs Division whose charter is to understand how the Space Station would be required to evolve under a variety of scenarios for the future, and what provisions must be made in the design of the Phase 1 Space Station to ensure that the evolution is possible.
Space Station evolution workshops, held in September 1985 and July 1986, laid the foundation for understanding how to accommodate a variety of users whose requirements may not be compatible. These workshops recognized, for example, that a laboratory in space, featuring long-term access to the microgravity environment, might not be compatible with an operational assembly and checkout facility, as construction operations could disturb the scientific environment.
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Artists conception of the Phase 1 Space Station.
Space Station evolution planning will include an assessment of the implications of each of the four initiatives. It is important to have specific scenarios, with a level of technical definition behind them, to serve as a basis for these assessments. It is also important that results from these assessments feed back into the initiative scenarios. This iterative approach is required to establish reasonable evolution scenarios and initiatives that are compatible with the proposed evolution.
The Lunar and Mars initiatives also have a critical need for the capability to transport personnel to and from the Space Station. This need could be filled by a personnel module added to the Shuttle, or by some other personnel carrier. The additional crew members would perform on-orbit assembly of the cargo and crew vehicles. Although there is currently no good estimate of the size of the crew required to assemble and test a vehicle in orbit, it is likely that the Lunar initiative, if it develops as projected in Phase III, would require more than 30 people in low-Earth orbit by the year 2010. It builds to this peak gradually, though, and the early assembly requirements (2000 to 2005) can be phased in slowly.
All the initiatives have other needs as well. The Planetary initiative's needs are limited to expendable stages, and possibly an Orbital Maneuvering Vehicle for the recovery of a returned Mars sample. The Earth initiative makes more substantial use of Earth-orbital transportation, including a transfer vehicle to lift fully assembled observing platforms from the Space Station to geosynchronous orbit, and sophisticated Orbital Maneuvering Vehicles to aid in platform servicing. The Lunar and Mars initiatives are more demanding. Both are likely to require Orbital Maneuvering Vehicles to transport personnel from the Space Station to orbital assembly sites. Most significant, both require substantial space transfer vehicles to transport crews from low-Earth orbit to either the Moon or Mars. Although the lunar transfer vehicle could be a derivative of a transfer vehicle to geosynchronous orbit (or vice versa), at this time it appears that the Mars transfer vehicle will demand a different design.
The orbital facilities required for each initiative are shown in Table 2. The Planetary initiative has limited requirements in this area; the other three have extensive needs that begin with the Phase 1 Space Station. The Phase 1 Space Station includes polar platforms and attached payloads for the Earth initiative; it serves as a technology and systems test bed for the Lunar initiative; and it will be a crucial laboratory for life sciences research and technology development for the Mars initiative.
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Table 2. Orbital Facilities Required for the Initiatives
All the initiatives require that the Space Station evolve additional capabilities, but the needs of the Planetary initiative (a sample return module) and the Earth initiative (servicing capability, operation of a space transfer vehicle) are relatively modest. The Lunar initiative requires gradual evolution to support the assembly, servicing, and checkout of lunar transfer vehicles. This requires more people in orbit (and therefore more Space Station modules and logistics traffic), spaceport facilities, and a propellant depot. The Mars initiative also relies on those spaceport facilities and additional crew accommodations, and although it will not occur quite as soon as in the Lunar initiative, the assembly of the large Mars cargo and piloted vehicles will be a significant task.
The Lunar initiative includes significant surface facilities such as habitation modules, laboratory modules, and an oxygen plant; the Mars initiative looks toward an eventual outpost (after 2015), but while similar surface facilities would be necessary at that time, they have not been included in the assessment to 2010. The Lunar and Mars initiatives both require landers, ascent vehicles, and rovers. These would most likely use some common technologies and subsystems, but they would not be identical.
The initiatives also require investments in technology development, and investments in institutional and human resources. This support early in the life of an initiative is vital to its success. The level of investment required is directly proportional to the magnitude and complexity of the initiative. The Earth and Planetary initiatives would be expected to have relatively modest needs; the Lunar and Mars initiatives would demand substantial technology development programs, and significant increases in highly skilled personnel and institutional facilities. The need for a dedicated, enthusiastic, and technically competent workforce must not be minimized; the Lunar and Mars initiatives would both require a significant increase in human resources.
The current level of definition of the initiatives, particularly the Lunar and Mars initiatives, is not adequate to reasonably estimate their costs. But while it was not appropriate to attempt to determine the absolute level of resources required by each, it was reasonable to estimate the relative levels through 2010. For each initiative, after the elements not included in current NASA plans were identified, the mass and size of each were estimated in order to determine the transportation requirements for that initiative. There was no attempt, at this early stage, to optimize the transportation system.
Figure 14 compares the resources required by the four initiatives during the next five years. It is important to understand the level of effort needed to support a new initiative during this period, since the country will also be relying on the civilian space program to return the Shuttle to flight, to reinvigorate its transportation system, and to continue serious preparations for the Space Station.
The Lunar, Earth, and Planetary initiatives would take about the same level of investment through 1992. The investment in the Lunar initiative would be primarily in technology and in early transportation development; in the Earth initiative, it would be largely in the development of the polar platforms, data handling system, and transportation; in the Planetary initiative, it would be primarily in technology, and in readying the Comet Rendezvous Asteroid Flyby mission for a 1993 launch.
The Mars initiative requires the largest commitment in the early years. This would be primarily an investment in transportation elements and in life science related additions to the Space Station. Transportation and Space Station use have not been optimized, so some reduction might be possible. The message, however, would not change: the country would have to make a major investment in the next five years to land people on Mars in 2005.
The complexity of both the Lunar and Mars initiatives in the year 2000 demands technology developments early in the program. Thus, through 1992 the majority of the Lunar initiative, and a significant portion of the Mars initiative, would be comprised of those technology activities which lay the groundwork for the initiative. Like early work in transportation, there is considerable synergism in the early technology requirements of these two initiatives.
Figure 15 compares the initiatives through 2010. The Lunar and Mars initiatives are nearly an order of magnitude greater in programmatic scope than the Planetary and Earth initiatives. The levels of investment in the Earth and Planetary initiatives peak in the early-to-mid-1990s, and then decrease to levels which remain fairly constant through the first decade of the next century. The Lunar initiative does not require extraordinary resources through 1992, but the commitment builds substantially in the mid1990s. It peaks in about 2000, at the time of this initiative's first human landing, and stays high through 2010 as the outpost is developed into a permanent base. The total level of effort through 2010 is large, and reflects the ambitious approach to the construction of the lunar base. However, the nature of this initiative allows considerable flexibility. For example, the outpost materials could be delivered to the surface rapidly or at a more deliberate pace; certain capabilities of the outpost could be emphasized and developed before others; or the transition from a temporarily occupied outpost to a large permanently staffed base could be delayed. Any of these options would significantly reduce the investment through 2010.
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Figure 14. Resources Required by Initiatives through 1992
Figure 15. Resources Required by Initiatives through 2010
Although the Mars initiative offers the greatest amount of human and technological drama, it also demands the greatest investment. The Mars initiative definition included only those elements required for the three sprint missions, the last in 2010, so the level of investment shown is artificially low between 2005 and 2010. The magnitude of the initiative indicates a large commitment of resources, and the timescale dictates that the investment peak in about 2000.
It is possible to reduce the early investment to a level comparable to that of the other three initiatives by allowing the first human landing to occur in 2010, rather than in 2005. The 2005 landing was selected at the outset to achieve the major milestone within two decades, but this analysis suggests that this ground rule may not be appropriate for the Mars initiative.
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