The Value of the Moon: How to Explore, Live, and Prosper in Space Using the Moon's Resources (2016)
After Apollo: A Return to the Moon?
The two decades following the end of the Apollo program are the wilderness years of lunar exploration. Despite repeated attempts and endless discussion, except for flybys by spacecraft on their way to somewhere else, between 1972 and 1994, there were no American missions to the Moon. Still, we continued to study the samples and data returned by the Apollo missions. There was occasional excitement when an international mission returned new lunar data or information, or when the odd American spacecraft acquired some new data as it flew past the Moon. During these years, we made significant advances in our understanding of the nature of the Moon and with it, gained a better understanding of the requirements for living there, all which added to the frustration of advocates desiring a return to the Moon.
The entire American space program suffered an identity crisis in the early 1970s. Following the success and hoopla of winning the race to the Moon, America seemed to lose interest in space. At least, that’s what we were told had happened.1 Social commentators decried the efforts of the American space program, describing them as irrelevant and a waste of money. Defenders of the space program spoke about technical spinoffs and societal inspiration. But the most inspirational aspect of Apollo turned out to be the most effective one used against it: the striking image of a nearly full Earth rising above the lunar horizon, first seen during the Apollo 8 mission of December 1968. Similar images were subsequently captured by each succeeding mission. The view of a blue and white Earth suspended in black space above the barren, lifeless Moon initiated the modern environmental movement, which, in turn, quickly blossomed into a Luddite, anti-technological crusade. People were encouraged to eschew technology, forswear a modern civilized lifestyle, and go back to the land.
During this time, human spaceflight was focused exclusively on low Earth orbit. The development of the space shuttle was billed as a program that would “make spaceflight routine.” Many equated “routine” with “cheap.” While the program achieved the former, it did not attain the latter. With the space program effectively capped at less than 1 percent of the federal budget per year, there was no money to develop human missions beyond low Earth orbit (LEO). While the shuttle has been labeled a policy failure,2 in truth, it offered several unique and valuable capabilities, including some that are not available now, or even contemplated to be present on any future manned spacecraft. The shuttle’s development was marked by technical difficulties and fiscal challenges, but in hindsight, it is hard to see how it could have been done any better or more inexpensively.
In addition to developing the shuttle, NASA used surplus hardware from the Apollo Moon program to make Skylab, America’s first orbiting space station.3 Skylab was a Saturn third stage (S-IVB) with its interior configured into a living and laboratory space for three crewmembers to inhabit for periods of up to ninety days. The laboratory, launched on a Saturn V on May 14, 1973, quickly encountered problems when during ascent its thermal shield was torn away. Skylab also experienced significant problems when one solar array was torn off during launch, and the other did not deploy on arrival in orbit, pinned to the side of the lab and unable to generate electrical power. As a result, when the crew arrived a few days later, the workshop was severely underpowered and overheated. So severe were these problems that they threatened to cause an early termination of the first Skylab manned mission and the Skylab program as a whole.
Skylab 2’s crew, consisting of Pete Conrad, Paul Weitz, and Joe Kerwin, went straight to work troubleshooting these problems. They erected a sunshade parasol that allowed the vehicle to remain cool under the glare of solar illumination. They conducted spacewalks to free the pinned solar array. Once it was fully deployed, it started producing electrical power. The crew spent a record-setting twenty-eight days in orbit, and thanks to their sustained and heroic efforts, Skylab was saved. During their long-duration mission, they activated on-board experiments, conducted a variety of medical experiments, mapped the Earth, and made solar observations with the use of a special telescope.
Two additional Skylab crews followed, spending periods of two and three months respectively in the orbiting space station. The last crew left the station in a configuration that would allow it to be visited and used by a future crew of the yet-to-fly space shuttle. In order to attach new solar arrays and a docking mechanism, and to outfit the laboratory for use by up to six or seven crew members, plans were developed to fly a couple of shuttle missions to Skylab in 1979–80. However, these missions never flew. The shuttle had run into development problems, which delayed its first launch until well after 1980. By the late 1970s, enhanced solar activity had heated and expanded the atmosphere outward, increasing the drag on Skylab. This increased drag made the orbit of Skylab decay at a much higher than anticipated rate, eventually leading to an uncontrolled reentry of the lab on July 11, 1979. Although NASA attempted to steer the vehicle to uninhabited ocean, large chunks of debris fell on the outback in southwestern Australia. Fortunately, no one was injured and there was little property damage.
Once believed to be the beginning of a long-term effort, one that would see Apollo space hardware conducting a wide variety of missions throughout cislunar space, Skylab now represented the shriveled remnant of our ambitious post-Apollo plans. By using the basic building blocks of Saturn and the Apollo command and lunar modules, this program, dubbed Apollo Applications, had envisioned space stations with orbital servicing vehicles, lunar orbital observatories, and even surface outposts. The problem for Apollo Applications was that it needed the Apollo and Saturn production lines to remain open and that required more money than Congress and the President were willing to make available. The shuttle had been sold politically on the promise of making space affordable. Since there was no affordable way that both could be in production at the same time, something had to go. With the demise of the Apollo-Saturn production lines, plans for missions throughout cislunar space ended.
The space shuttle was originally designed to become the first piece of an entirely new line of reusable, extensible space hardware. The shuttle, as developed, could only go to and from low Earth orbit but its designers certainly had no intention of stopping there. The official name of the shuttle was the Space Transportation System (STS), a name chosen to convey that the Earth to LEO orbiter was only a single piece of a larger, more comprehensive system—a system that included a permanent space station and an orbital transfer vehicle, a space-based “tug” that could haul satellites and other payloads to high orbits above LEO. But that concept was gradually forgotten as we busied ourselves with specialized missions to LEO and with the monumental task of building a new space station—NASA’s principal destination in space for the 1980s—assembled on orbit over time from pieces brought up by the shuttle.4
The end of the Apollo program was followed by the doleful coda of the Apollo-Soyuz Test Project (ASTP), a joint flight of American and Soviet human spacecraft designed to inaugurate a new age of cooperation in space and ensure peace on Earth.5 The Apollo crew consisted of veteran Apollo astronaut Tom Stafford commanding, flying with Vance Brand and Deke Slayton, who was finally getting his chance in space after being grounded for thirteen years because of a heart murmur detected in 1962. They rendezvoused in space with a Soviet Soyuz spacecraft commanded by the first man to walk in space, Alexei Leonov, and his copilot, Valeri Kubasov. The two spacecraft docked using a common berthing mechanism provided by the United States. After exchanging handshakes and smiles, the crew drifted over the Earth in an extended demonstration of good will, good spirits, and fervent hopes for future cooperation in space. Cooperation would eventually come twenty years later after the Iron Curtain was dismantled, and with it the Soviet Union.
With the splashdown of the ASTP on July 24, 1975, America was without any means to send people into space until the new space shuttle system became operational. The shuttle was a complicated and delicate vehicle. It had to withstand a violent launch and ascent as well as a harrowing reentry speed of Mach 25, all while retaining a low enough mass to make the entire system work. Low-weight silica tiles that were glued onto the outside of the orbiter airframe provided the necessary thermal insulation to block the searing heat of reentry. These thermal protection tiles caused ongoing and endless headaches over the entire thirty years of shuttle operations. The thermal tiles were both fragile (likely to break if dropped) and tended to fall off the airframe (finding the right bonding agent to glue them in place took some time).
Several drop tests were conducted in which a shuttle was released from its carrier 747 aircraft and allowed to glide to the surface before the first space shuttle orbital mission launched in April 1981. Astronauts John Young and Bob Crippen flew the first shuttle orbiter Columbia into space and safely returned it to Earth.6 That flight verified the system’s basic design and started the next chapter in the history of the US space program. Shuttle flights continued apace throughout the 1980s, as flight after flight delivered satellites to their orbits and flew a variety of Earth observation and medical experiments. The shuttle design allowed it to be fitted with Spacelab, a cylinder-like module roughly the size of a school bus that was carried inside the shuttle cargo bay. Since Spacelab flew only during a shuttle mission, its operation in orbit was limited to about two weeks, the limit of the amount of reactants that could be carried for the shuttle’s fuel cells and fuel for attitude control.
In addition to these high profile civil space missions, several early shuttle flights were dedicated to the launch of national security payloads. This was a consequence of promoting the shuttle to the Congress as the universal replacement for all expendable launch vehicles. The argument was made that shuttle could handle and deliver on orbit any and all payloads—scientific, commercial, and national security. Estimates made during vehicle development suggested that as many as fifty flights per year were possible. But after the shuttle became operational, the vehicle required much more refurbishment between flights (and consequently, more time to prepare for launch) than had been anticipated. At peak rates of activity, the shuttle flew about eight to nine times per year. While this flight rate was quite respectable for such a complex system, it was not the level of activity envisioned and desired in the early days of the program.
Despite the operational successes of the space shuttle program, a gradual sense of ennui developed within the space community. The program’s seemingly endless series of missions to LEO had become its own justification, and it was perceived, perhaps unfairly, as a dead end. Initially, this was because there was no space station to support. When the additional pieces of the STS “system” did not materialize, it meant we had no station, no orbital maneuvering vehicle and no lunar tug. Thus, the STS had become a system with just one piece, and it was getting harder to justify a human space program that only orbited in endless circles.
The stasis, however, was more illusionary than real. Despite the shuttle program’s focus on low Earth orbit, advanced program planners in Houston had indeed been thinking about follow-on steps once the orbiter became operational. In accordance with the classic von Braun architecture, the obvious next step was some type of space station.7 Because Skylab had been lost and we no longer had the Saturn V launch vehicle, the shuttle would have to be used to assemble a space station. Using the shuttle as a delivery system meant that construction needed to be done in small pieces, with full station assembly requiring dozens of launches, spread out over many years.
Looking back from our vantage point of having an operational ISS, it is easy to forget what a monumental engineering and programmatic challenge that was. We had never assembled a giant, distributed-system satellite in space. The assembly of complex equipment and facilities in space would require techniques that had not yet been developed and were only vaguely understood. The assembly robots had not yet been conceived, let alone built, and a managerial structure had to be formulated that could adapt to changing budgets, module delivery schedules, weather delays, and pad availability. From their mid-1980s vantage point, those tasked with the challenge of assembling the station knew that many more unknowns than certainties lay ahead.
Having a large space station in low Earth orbit would offer more than just a laboratory for experiments: If properly constructed and configured, it could become the transit node for missions beyond low Earth orbit to the Moon and on to the planets. This idea still held sway in the minds of shuttle architects who took the moniker Space Transportation System literally. The von Braun architecture, laid out in the famous Collier’s articles of the early 1950s,8envisioned first a space station, then an orbital transfer vehicle, a Moon tug and lander, and finally an interplanetary spacecraft. This incremental, building block approach had been abandoned when the political imperative of beating the Soviets to the Moon had taken center stage, but it was an approach to which the space agency wanted to return.
President Ronald Reagan announced plans for the new space station program in his 1984 State of the Union speech.9 It would be called Freedom and would serve a variety of purposes, including laboratory research and observing the Earth and the universe, as well as serving as a transportation node. In its latter role, Freedom would be equipped with a servicing bay for satellite repair and serve as a departure point for missions from low Earth orbit to high orbits typically occupied by commercial communications and other satellites. Such transport required a reusable, refuelable vehicle, one that could move from low orbits to geosynchronous orbit (GEO), a circular, equatorial orbit about 22,000 miles (36,000 km) high. At this altitude, satellites orbit once every twenty-four hours and thus appear stationary or trace elongated, figure-eight loops in the sky. Any ground station on the hemisphere below the satellite in GEO is always in radio view. GEO is extremely important real estate for global communications, weather monitoring, and remote sensing.
A rocket launched from the surface of the Earth expends virtually all of its fuel to achieve low Earth orbit. But in terms of orbital energy, this is only about halfway to geosynchronous orbit. To get satellites to GEO, the rocket would have to carry an upper stage for the final orbital transfer, thus limiting the size, and therefore capacity, of a satellite in GEO. Additionally, a satellite in high GEO would not be accessible by the shuttle, or any other human spacecraft to date. When a high orbit satellite malfunctions, typically it is abandoned and deorbited, whereupon an entirely new satellite must be built and launched.
Having a spacecraft stationed at the low orbit space station would solve this dilemma. It would permit crews to travel routinely to and from the high orbits that these satellites occupy to service or replace them. But more significantly, crews could build satellite systems that would be much larger and more capable than any that could be launched on a single existing or planned launch vehicle. If the building of Freedom were successful, it would teach us how to build large, distributed systems in space. These techniques could then be applied to complex satellites in high orbits, presuming that there would be a way to get crews and repair facilities to that high orbit.
A key piece of the evolving STS, the projected orbital transfer vehicle (OTV), was designed to be berthed at Freedom and available to transport people and equipment to higher orbits when needed. The OTV was to be fueled by liquid hydrogen and oxygen brought up from Earth, at least initially. The vehicle also carried a heat shield, allowing it to use the friction of Earth’s atmosphere to slow down the vehicle during close approach on return to LEO, thus requiring only a minimal amount of maneuvering capability. This strategy made the vehicle smaller and more efficient. Development of an OTV would be the next link in creating a genuinely space-based transportation system—and a vehicle that could routinely reach GEO could also go to the Moon.10 Despite its many potential benefits, an OTV was never built.
The Lunar Base Movement (1983–93)
In 1983, two scientists from the Johnson Space Center, Michael Duke and Wendell Mendell, realized that if NASA developed the OTV as part of the shuttle-station architecture, we would possess the means to return to the Moon. Along with physicist Paul Keaton from Los Alamos National Laboratories, they organized a small workshop, which was followed by a major conference at the National Academy of Sciences in Washington.11 That conference drew a large and enthusiastic attendance of engineers, scientists, and space visionaries. Over the course of three days, they discussed and pondered the implications of a lunar return. The scope of the meeting varied widely, with such topics discussed as extended exploration of the Moon, habitation and life support, mining and use of local materials for oxygen and construction, and orbit-to-surface transportation and fueling depots.
This meeting initiated a large community movement dedicated to lunar return. Enthusiasts and advocates studied and improved their knowledge of the lunar surface and materials in preparation of a return, not in the temporary, sortie mode of Apollo, but for longer, more permanent stays. A series of meetings, workshops, and conferences over the next few years fleshed out possible scenarios for lunar return. Much attention was paid to the possible use of lunar resources to support extended human presence on the Moon and elsewhere in space.12 These schemes tended to focus primarily on the production of oxygen; lunar soil is about 45 percent by weight oxygen, although extracting it and converting it into its free, gaseous form was found to be a very energy intensive activity. Moreover, the environment of the low latitude regions of the Moon requires a long-lived source of electrical power in order to survive the fourteen-Earth-day-long lunar night. Thus, studies of power generation mechanisms needed at lunar outposts to keep equipment and people warm during the bone-chilling lunar night, revolved around the development of nuclear reactors, which would provide steady, constant electrical power and heat.
All these studies concluded that while lunar habitation was possible, it would require several expensive technical developments. Once again, space dreams ran up against the cold realities of fiscal constraints. The response to this realization tended to focus on justifying lunar return in terms of some high-value benefit, such that billions of dollars of investment would be worthwhile. Such benefits typically involved the production of clean electrical energy for the Earth. One idea was to make solar cells in situ on the lunar surface and create kilometer-sized photovoltaic arrays whose power output could be transmitted to Earth via microwave or laser. An alternative concept was to harvest the lunar regolith for a rare isotope of helium, 3He, which could fuel a “clean” fusion reaction, i.e., one that produces no harmful radioactive by-products.13 Although 3He is present on Earth as a trace component of natural gas, it is found in extremely minute quantities, inadequate to fuel a commercial electrical generating industry. However, the Sun streams energetic particles continuously. This is the solar wind, which bypasses the Earth due to our global magnetic field but is implanted on lunar dust grains. Although still present in relatively minute amounts in the lunar soil (about twenty parts per billion), studies indicate that such concentrations are large enough such that 3He could be harvested from the Moon. This idea caught the imagination of both the public and the lunar return community when it was first proposed. However, several significant technical prerequisites remain before we have power generation systems that use 3He, most significantly, the need for a reactor design in which to burn the helium fuel.
A major activity of the lunar science community in the 1980s was an effort to send a robotic mission to orbit the Moon. This mission concept first emerged in the mid-1970s under the name Lunar Polar Orbiter (LPO), a perfect descriptor. Because the plane of an orbit is fixed in inertial space, a satellite in polar orbit will view the entire surface as the planet or moon slowly rotates on its axis. Such a spacecraft could be configured with nadir-pointing instruments to measure a variety of chemical, mineralogical, and physical properties of the Moon. All of the Apollo missions flew in near-equatorial orbits, so only about 20 percent of the lunar surface was overflown and mapped with compositional remote sensors from the orbiting Command-Service Modules. Both of the Lunar Orbiter IV and V spacecraft were placed in polar orbits and completed a global survey of the Moon, documenting their value.
Figure 3.1. Lighting maps of the north (left) and south (right) poles of the Moon. On these composite images, bright areas are in sunlight for extended periods while black areas are in permanent darkness. This relation (caused by the 1.6° obliquity of the Moon) makes cold traps that have accumulated significant amounts of water ice over geological time. The sunlit areas permit electrical power to be generated nearly continuously. (Credit 3.1)
One critical piece of information about the Moon was much debated in the years following Apollo. No evidence for water—past or present, on the surface or inside the Moon—was found in the lunar samples, a finding that led to the dogma that the Moon was bone-dry and that it had always been so. As such, this made the task of living on the Moon much more formidable and challenging. However, before the advent of the Space Age, we knew that the poles of the Moon had some unique properties. Because the spin axis of the Moon is nearly perpendicular (88.4°) to the plane of the ecliptic (the plane in which the Earth-Moon system orbits the Sun), the Sun always appears on or close to the horizon at the lunar poles. If you were on a peak, you could be bathed in constant sunlight. Conversely, if you were in a hole (crater) at the poles, you might never see the Sun (see figure 3.1). These dark areas would be extremely cold, since the only heat they receive comes from the extremely low quantities of heat flowing from the interior of the Moon itself.
Several studies suggested that these properties could have some dramatic consequences. We had evidence that the Moon has been bombarded by water-bearing objects—namely, comets and meteorites—over its history. Most of this water would be lost to space or dissociated in the high temperature vacuum of the lunar surface. However, if water somehow found its way into a dark “cold trap” near the poles, it would remain there forever, and no known natural process could extract it. Much speculation was expended on how much ice might be in the polar regions of the Moon, but we could not know if it was there until we went looking for it.14 A polar orbiting, remote sensing satellite (e.g., LPO) was needed to detect what might be in those dark areas.
Despite its appeal on scientific grounds, and its obvious importance as a precursor for eventual human return to the Moon, the LPO mission was repeatedly passed over for other missions throughout the twenty years following Apollo. In January 1986, the space shuttle Challenger exploded shortly after liftoff, killing all seven of its crew, including Christa McAuliffe, who was not an astronaut but instead the first teacher in space. The shock of this tragedy was a public relations disaster for the agency, followed by a wrenching period of introspection and soul-searching about its vision and purpose, along with the accompanying technical reviews called up to fix the problem and restart the shuttle program. In addition to agency chaos after the Challenger accident, the Freedom project was also in turmoil, having undergone two complete redesigns before the shuttle accident, followed by another redesign a year later. Because of the major disruption of the loss of a shuttle, serious concerns were raised about the viability of the space station program.
Two reports were issued during the manned spaceflight hiatus of the late 1980s. The Rogers Commission, named after its chairman, former Secretary of State William Rogers, was chartered to identify the cause or causes of the Challenger accident and to recommend policies and procedures to fix the problem.15 The other commission had a broader task: The National Commission on Space (NCOS), also called the Paine commission after its chairman, former NASA Administrator Thomas Paine, was asked to devise a set of long-range goals for space and to identify some of the strategies needed to attain them.16 The NCOS work was near completion when the Challenger accident occurred, and because of this unfortunate timing, its report was largely ignored when released. However, the Paine Commission report was very thorough and complete. It identified a systematic, incremental, and affordable expansion of humanity into space, for all the reasons we have identified over the years—the NCOS vision prominently featured space resource utilization in addition to exploration and science. It anticipated almost all of the current arguments for space goals and destinations, and suggested that because all are desirable in the objective sense and have their own constituencies, each can and should be pursued via a program that incrementally develops a wide range of capabilities.
The agency responded to the Paine report with a series of studies and workshops throughout the hiatus period in human spaceflight, culminating with a report issued in August 1987 by an internal study group led by astronaut Sally Ride. The Ride Report identified four mission concentration areas: Earth system science from space, unmanned space science exploration, a lunar outpost, and a human Mars mission.17 The report did not advocate or choose any of the four but instead focused on what benefits and spacefaring legacies each one would give us. It suggested that a heavy lift launch vehicle would enable many of these activities and that a new HLV, using shuttle-derived hardware, could be developed quickly and inexpensively.
Rise and Fall of the Space Exploration Initiative (1989–93)
Problems with the shuttle solid rocket booster joints (identified by the Rogers Commission) were corrected and the vehicle returned to flight in September 1988. Armed with a renewed capability to get humans to and from orbit and with reports from three blue-ribbon study groups, President George H. W. Bush made the decision to announce a new major direction for America’s space program. Much speculation has been expended on the origins of the subsequent Space Exploration Initiative (SEI).18 My interpretation is simple: at the end of the 1980s and the beginning of the 1990s, as the Cold War was winding down in our favor, concern had developed about the erosion of our national technical capabilities—the enormous defense industrial infrastructure that won the struggle against the Soviet Union. President Bush and his advisors were well aware of this issue and the need to maintain a level of advanced technical infrastructure in the absence of the Cold War political imperative. The space program had served that purpose before and thus, an expanded space program—made affordable by the easing of defense requirements—could maintain a keen technological edge at a fraction of the level of Cold War defense expenditures. Curiously, the members of the Bush administration responsible for space policy never made this point publicly, but I know from discussions with some of them that many in the White House were well aware of its dimensions and implications.
In a special speech delivered on the steps of the National Air and Space Museum in Washington DC, President Bush announced the new initiative on the twentieth anniversary of the Apollo 11 Moon landing.19 The SEI was what space enthusiasts had been wanting since the Apollo program: a presidential declaration on ambitious space goals. It called for the completion of space station Freedom, a return to the Moon (“this time to stay”), and a human mission to Mars. The president did not set forth deadlines for each milestone, except that space station Freedom should be completed within the next decade and that missions to the other destinations were tasks for the new millennium. The president asked his own White House National Space Council to examine and define the technologies and architectures needed to implement his new space initiative. Naturally, the Space Council turned to NASA for assistance in this new task.
Teams from NASA Headquarters and the field centers were quickly assembled and charged with defining the steps, and the missions and pieces of the new program. They were tasked to report to the White House within ninety days. The “90-Day Study” soon became infamous as the death certificate of the SEI, although in hindsight, it is not nearly as nefarious as widely reported and believed, and in fact, contains much good engineering sense and many clever ideas.20 In short, the main problem was that NASA was barely being funded at an adequate level to run the space shuttle program and to build Freedom. Naturally, it would require additional funding if additional major tasks were added to its agenda. Such logic was forgotten or ignored in an orgy of self-righteous indignation over the “pedestrian and bloated approach” of the 90-Day Study. Five alternative “reference approaches” were outlined, with each building outward from the shuttle/station in incremental steps while varying the rate of development and the amount of activity according to selectable levels of effort.
The biggest problem with the 90-Day Study was not the report itself, but what happened behind the scenes. The report deliberately did not include budget information. Estimated costs were prepared so that policymakers could evaluate differences among the approaches. As one might expect, once these cost numbers were leaked to the press, the chattering classes inside the Beltway were aghast: the new SEI was expected to cost upward of $500 billion! What was always left out of these stories was that this cost number was the aggregate budget of the agency spread over the course of thirty years, a metric against which few federal agencies would stand up well under scrutiny. And given the national security dimension of the new SEI, such sums were a mere fraction of the national defense budget over the same period. Nonetheless, this number was widely circulated. It quickly became “canonical” and was used to discredit and disparage the whole idea of the SEI.
The White House and Space Council knew that political forces outside their control were torpedoing their new, major initiative.21 To fight this effect, the Space Council convened a special committee to examine the 90-Day Study, as well as to review detailed alternatives prepared by industry and other federal entities. The most famous of the latter was the proposal from Lawrence Livermore National Laboratory to use inflatable vehicles launched on existing expendable rockets.22 This proposal claimed that both a lunar return and a manned Mars mission could be conducted for less than one-tenth the leaked cost of the 90-Day Study. Regardless of the doubtful veracity of that cost estimate, or the technical feasibility of the concept, it drew major attention from the White House. That attention propelled the canvassing of a wider segment of the community with hopes it would generate new and innovative ideas with which to implement the SEI for a fraction of the funding that NASA claimed was needed. The National Research Council, whose special report on the study concluded that a variety of other technical options should be investigated, ones that NASA had not considered, provided additional support for a major reevaluation of the 90-Day Study.
In this vein, the Space Council decided to create an outreach effort that would gather up the best technical ideas on how to implement the SEI from all sectors. These educated and innovative suggestions and plans were to be collected, evaluated, and high-graded by a special panel called the Synthesis Group and distilled into a plan for a magical—meaning cheap—beanstalk into space. This panel included members from academia, government, and industry and was chaired by astronaut Tom Stafford. I was a member of this group from August 1990 to June 1991. Tom Stafford said this activity was “like drinking from a fire hose,” and I found that to be an apt description. The ten months spent serving on Synthesis was a crash course in astronautics, a course that included the benefits and pitfalls of technology development and its role in architectural design. As one might expect, the massive input from the space community did not contain any “magic beans” or “silver bullets” that would take us to the Moon and the planets faster, better, or cheaper.23 And in that sense, the Synthesis Group did not succeed. But in another sense, the Synthesis Group advanced our understanding about the Moon and its crucial role for human expansion into the solar system.
Two events occurred in the spring and summer of 1990 that severely damaged the cause of SEI. The first event involved the Hubble Space Telescope. Although the telescope had been successfully launched, it was soon discovered that its main optical element had been ground to the wrong specification. This mistake caused Hubble’s highly anticipated new images of the universe to be out of focus.24 The other event was the temporary grounding of the shuttle fleet because of an unresolved hydrogen leak. These problems, along with the release of the 90-Day Study, combined to present the image of a space agency that was both technically incompetent and politically out of touch. Thus, despite giving the space agency an additional $2 billion overall in the FY 1991 budget, Congress zeroed out the SEI, a clear signal that NASA was in serious political trouble. The deep antipathy between the space agency and the White House was finally resolved with the sacking of Richard Truly as administrator and the subsequent hiring of Daniel Goldin as his replacement. Despite attempts to initiate SEI again in the following two years, Congress would not approve or fund it, and the initiative was terminated following the reelection defeat of President Bush and the advent of the Clinton administration.25
The Clementine Mission and Its Legacy (1994)
The lunar science community continued to lobby NASA to send a robotic orbiter to the Moon, but to no avail. Their goal was to map the Moon’s shape, composition, and other physical properties. Such a mission would not only document the processes and history of the Moon but would also serve as an operational template for the exploration of other airless planetary objects. A collection of global remote sensing data could provide scientists with invaluable ground truth when used in conjunction with the previously returned Apollo surface samples. The Lunar Polar Orbiter mission, proposed several times, never received a new start. Its last incarnation was the Jet Propulsion Laboratory’s Lunar Observer, patterned after the ill-fated Mars Observer mission. The cost review of Lunar Observer came in at around $1 billion in 1990 dollars. Of course, it was passed over yet again.
Stewart “Stu” Nozette of Lawrence Livermore National Laboratory, another Synthesis Group member, was involved in the Brilliant Pebbles (BP) program of the Defense Department’s Strategic Defense Initiative.26 The idea behind BP was to defend the nation against ballistic missiles by launching swarms of small, inexpensive satellites, each capable of observing, calculating and plotting an intercept course to incoming missiles (the “brilliant”) and then rendering them inoperative by collision (the “pebble”). These small, three-axis stabilized vehicles carried imaging sensors (both active and passive) as well as in-flight computers and propulsion systems. In short, they were small but fully capable, self-contained spacecraft.
Nozette’s idea was to fly a BP to a distant target in space. Because of his interest in space resources, he devised a mission that would fly by an asteroid and possibly orbit the Moon. Stu and I discussed these possibilities, and it seemed that a fairly significant mission might be built around these small spacecraft. My colleague Eugene Shoemaker of the US Geological Survey was brought in early on the planning of this mission. Gene was a legend in planetary science circles. A member of the National Academy of Sciences, he had done the original geological mapping of the Moon before the Apollo program and was actively researching asteroids. His interest and involvement with the mission brought both prestige and credibility to the idea.
An agreement between NASA and the Strategic Defense Initiative Organization (SDIO) specified that NASA would provide the science team and the communications tracking support for the flight, and that SDIO would provide the sensors, spacecraft, and launch. The sensors had been developed at Livermore as part of the BP program, while the Naval Research Laboratory (NRL) would design and build the spacecraft, later named Clementine. Launch was on a surplus Air Force Titan II rocket, the same vehicle NASA used to launch the two-man Gemini missions in the 1960s. Because the Titan II pad at the Cape had been dismantled, the mission would be launched from Vandenberg Air Force Base near Lompoc, California.
The mission would put Clementine in a polar orbit around the Moon for two months, providing global coverage. The spacecraft would map the color of the lunar surface in eleven wavelengths in the ultraviolet, visible, and near-infrared portions of the spectrum and measure the Moon’s shape from laser ranging. Other remote measurements would be acquired as opportunity presented. After this phase, Clementine was to leave lunar orbit and fly by the near-Earth asteroid Geographos. Program Manager Pedro Rustan, an Air Force colonel, was a skilled, tough engineer who kept us to deadlines. Stu became his deputy, coordinating many different activities, ranging from science objectives to spacecraft fabrication and testing. The Science Team, twelve lunar scientists with varied expertise, was selected from individual proposals submitted to NASA. Gene Shoemaker was named the team leader, and I was his deputy. Together, we planned mission operations with the NRL and Livermore teams. The Science Team carefully selected the filter bandpasses for the imaging systems that would allow the identification of lunar rock types from the color images.
The Clementine mission was remarkable for its short development cycle and cost. Twenty-two months elapsed from project start to launch, while a typical NASA planetary mission took from three to four years. In FY 1992 dollars, NRL spent about $60 million for the spacecraft and the mission control center. Livermore spent about $40 million on support services and on the production of the mission sensors. The Titan II launch vehicle and services, supplied by the Air Force, were valued at about $20 million, with an additional $10 million or so for avionics upgrades. The NASA Science Team cost a couple of million dollars, and the Deep Space Network support was a few million more. By totaling those numbers, I estimate that the mission cost about $140 million, or $540 million in today’s dollars; for comparison, the then-recently lost NASA JPL Mars Observer mission cost a bit over $800 million, or more than $2 billion in 2014 dollars.
Those cost numbers caused considerable controversy, with some in the scientific community whining that the massive “Star Wars” (SDI) program absorbed and hid much of Clementine’s cost. In fact, the whole point of the Brilliant Pebbles program was to adapt cheap, rugged tactical sensors to deep space use and thus take advantage of the cost savings provided by mass production (as opposed to the custom builds of most space systems). Moreover, there was nothing to stop NASA from using this same technology, other than a not-invented-here mindset and the still-prevalent tendency in the space science community to gold-plate scientific payloads.
The Clementine mission demonstrated the value of the so-called Faster–Better–Cheaper (FBC) paradigm.27 The concept is not that cheap missions are inherently “better” but that by carefully restricting mission objectives to only the most essential information, it is possible to fly smaller capable missions that can return 80 to 90 percent of the most critical data; resources are often squandered in an attempt to achieve that last 10 percent of performance. Maybe FBC should be renamed Faster–Cheaper–Good Enough. The broad success of NASA’s Discovery program over the last twenty years, in which mission objectives are carefully defined and limited to control overall cost, is testament enough to the general validity of the FBC concept. In addition to its scientific return, the Clementine mission flight-tested and qualified twenty-two new spacecraft technologies, including solid-state data recorders, nickel-hydrogen batteries, lightweight components, and low-mass, low-shock, nonexplosive release devices. All of these technologies have been employed on dozens of subsequent space missions, making many of these spacecraft lighter, more reliable, and longer-lived.
On the morning of January 25, 1994, less than two years after project start, the members of Clementine’s science team stood together on a cold, windy California beach just a couple of miles from SLC-4W. We watched as the Clementine Titan II rose above the launch pad on a cloud of orange smoke and flame, arching into the clear, blue Pacific sky. We followed the vehicle’s progress all the way through staging before losing sight of it. I left Vandenberg excited about the mission ahead, but my mood quickly changed when Science Operations Manager Trevor Sorensen sent news that we were in danger of losing the spacecraft (erroneous commands had been sent to Clementine, and the spacecraft was out of control). Fortunately, we recovered.
Once our spacecraft had safely inserted itself into orbit around the Moon and began mapping its surface, we were eager to get our first images. Our perch for receiving this mission data was a converted National Guard armory in Alexandria, Virginia. Dubbed the Batcave, the armory served as mission control center for the duration of the mission. Designed to save fuel, Clementine had taken a month-long, leisurely looping trip to the Moon, arriving there on February 19. When the first image finally flashed on the screen, I immediately recognized the crater but due to all the excitement, initially drew a blank on its name. Quickly consulting the wall map, I saw that we were looking at Nansen, a crater located near the north pole. A very strong sense of physically being present at the Moon came over me—I was flying across a landscape as familiar to me as any one that I knew on the Earth.
Mission operations became a regular series of work cycles arranged around the routine of collecting and downlinking data, verifying that the data was good, and making some initial scientific observations, although a couple of incidents from my time in the Batcave stand out.
As Clementine’s orbit was about to pass over Tycho, the largest rayed crater on the near side of the Moon, I alerted everyone in the Batcave’s control room that something incredible was about to appear. Audible gasps greeted the spectacular images of the floor and central peak of Tycho that came into view. On another occasion, Dave Smith, a science team member from NASA–Goddard Space Flight Center, asked how much polar flattening might be expected for the Moon. I replied “almost none,” mainly because of the slow rotation rate of the Moon (once every 708 hours) combined with the rigid, nonplastic state of the lunar globe. Then, as the orbital ground tracks slowly marched westward across the far side of the Moon, we saw an astonishing falling off of topography toward the south pole. This large negative relief was the rim and floor of the South Pole–Aitken (SPA) basin, an impact crater more than 2,600 kilometers across and more than 12 kilometers deep. Geologists had long known that this basin was present, but until Clementine mapped its topography, no one had fully appreciated its huge size and state of preservation.
By now, Clementine had already shown us the nature of the polar regions of the Moon, including peaks of near permanent sun-illumination and crater interiors in permanent darkness. From his first look at the poles, Gene Shoemaker had an inkling that something interesting was going on. Gene tried to convince me that water ice might be present there, an idea about which I had always been skeptical. At that time, no trace of hydration had ever been found in lunar minerals, and the prevailing wisdom was that the Moon had always been bone-dry. With Gene arguing for us to keep an open mind and Deputy Program Manager Stu Nozette devising a bistatic radio frequency (RF) experiment to use the spacecraft transmitter to “peek” into the dark areas of the poles, we moved ahead on planning our observations. This turned out to be the setup for a history-making event midway through the orbital mapping campaign.
Although Clementine did not carry sensors for the detection of water, Stu believed we could improvise an experiment using the spacecraft’s radio transmitter to “look into” the dark (and thus very cold) areas near the poles, places where water ice might exist. Radio echoes from the Moon could be detected on the giant radio antenna dish at Goldstone in California’s Mojave Desert. With careful planning and commanding of the spacecraft by Radio Engineer Chris Lichtenberg, we successfully took bistatic radio frequency (RF) data of both poles during those phasing orbits, when Clementine shifted the perilune (low point) of its polar orbit from 30° south to 30° north latitude.
To my astonishment, a single pass over the dark areas of the south pole of the Moon showed evidence for enhanced circular polarization ratio (CPR), a possible indicator of the presence of ice. A control orbit over a nearby sunlit area showed no such evidence. However, CPR is not a unique determinant for ice, as rocky, rough surfaces and ice deposits both show high CPR. It took a couple of years for us to reduce and fully understand the data, but the bistatic experiment was successful—and a huge scientific bonus. In part, our ice interpretation was supported by the then-recent discovery of water ice at the poles of Mercury (a planet very similar to the Moon with a comparable polar environment).28 Our published results in a December 1996 issue of Science magazine set off a media frenzy, followed by a decade of scientific argument and counterargument about the interpretation of radar data for the lunar poles—an argument that continues to a lesser degree to this day, despite subsequent confirmation of lunar polar water from several other detection techniques.29
The Batcave played host to several distinguished visitors during the two months that Clementine orbited the Moon, most notably astronauts John Young, a familiar face to members of the Synthesis Group and always a friend of lunar science, and Wubbo Ockels, a Dutch physicist with the European Space Agency. Ockels, encouraged by Clementine’s success, campaigned to generate enthusiasm for small, cheap lunar missions at ESTEC, the European space center in the Netherlands where he worked. US Representatives Bob Zimmer and Jim Moran were impressed with our operation and pledged their support in Congress for future space efforts like Clementine. Finally, then-new Administrator of NASA Dan Goldin visited, distributing lapel pins and offering encouragement to the worker bees. Not all at NASA were enamored with the mission though, with some resenting the attention it had drawn, particularly with regard to the inevitable comparisons with their own ongoing and budget overrunning robotic missions.
With Clementine, we had successfully returned to the Moon, mapped it globally, and made several significant discoveries. A Science Team press conference was scheduled at NASA Headquarters to report on the new scientific findings, but NASA intervened at the last minute and cancelled our briefing. Several mutually exclusive excuses were given for this cancellation, but it was clear to members of the science team that some in the agency wanted to keep a lid on the scientific success of the mission, which was embarrassing to NASA because Clementine was much cheaper than similar agency efforts, yet just as scientifically productive, if not more so. But in time, news of the discovery of “the most valuable piece of real estate in the solar system” was revealed. With urging from the planetary science community, NASA agreed to fund a research program to take advantage of the abundant new lunar data acquired by Clementine.
Two cameras on Clementine with eleven filters covered the spectral range of 415 to 1900 nm, where absorption bands of the major lunar rock-forming minerals (plagioclase, pyroxene and olivine) are found. Varying proportions of these minerals make up the suite of lunar rocks. Global color maps made from these spectral images show the distribution of rock types on the Moon. The uppermost lunar crust is a mixed zone, whose composition varies widely with location. Below this zone is a layer of nearly pure anorthosite, a rock type made up solely of plagioclase feldspar—the original lunar crust, formed during the global “magma ocean” melting event. Craters and large basins act as natural “drill holes” in the crust, exposing deeper levels of the Moon. The deepest parts of the interior (and possibly the upper mantle) are exposed at the surface within the floor of the enormous (2,600 km diameter) South Pole–Aitken basin on the far side of the Moon.
Before Clementine, good topographic maps existed only for the near-equatorial areas under ground tracks of the orbital Apollo spacecraft. From Clementine’s laser ranging data, we obtained our first global topographic map of the Moon. It revealed the vast extent and superb preservation state of the SPA basin and confirmed many large-scale features, mapped or inferred, from only a few clues provided by isolated landforms. Correlated with gravity information derived from radio tracking, we produced a map of crustal thickness, thereby showing that the lunar crust thins out under the floors of the largest impact basins.
As a result of this mapping, scientists could place the results of studies of the Apollo samples into a regional, and ultimately, a global context. Clementine collected special data products, including broadband thermal, high resolution and star tracker images for a variety of special studies. In 1996, after our paper was published in Science, a press conference was held at the Pentagon to announce the results of the bistatic experiment: the discovery of ice at the south pole of the Moon. In addition to discovering new knowledge of lunar processes and history, this mission led a strong wave of renewed interest in the processes and history of the Moon, an interest that spurred a commitment to return there with both machines and people. By peeking into the Moon’s dark polar areas, we now stood on the edge of a revolution in lunar science.
This renewed interest in the Moon led to the selection of Lunar Prospector (LP) as the first of NASA’s new, low-cost Discovery series of planetary probes. This mission found enhanced concentrations of hydrogen at both poles, again suggesting that water ice was probably present there. Buttressed by this new information, the Moon once again became an attractive destination for robotic and human missions. With direct evidence for significant amounts of hydrogen (regardless of form) on the surface, there now was a known resource that would support long-term human presence. Lunar Prospector’s hydrogen discovery was complemented by the identification in Clementine images of several areas near the pole that remain sunlit for substantial fractions of the year—not quite the “peaks of eternal light” anticipated by the astronomers Beer and Mädler in 1837, but something very close to it.30 The availability of material and energy resources, the two most pressing necessities for permanent human presence on the Moon, was confirmed in one pass. These two missions certified the possibility of using lunar resources to provision ourselves in space, thus permanently establishing the Moon as an enabling asset for continued human spaceflight. A remaining task was to verify and extend the radar results from Clementine and to map the ice deposits of the poles.
Missions flown over the last twenty years show how significantly Clementine’s programmatic template has influenced spaceflight. The Europeans flew the SMART-1 spacecraft to the Moon in 2002, largely as a technology demonstration mission with goals very similar to those of Clementine. NASA directed the Applied Physics Laboratory (APL) to fly the Near-Earth Asteroid Rendezvous (NEAR) spacecraft to the asteroid Eros in 1995 as a Discovery mission, to attain the asteroid exploration opportunity missed when control of the Clementine spacecraft was lost after leaving the Moon; the mission was renamed NEAR-Shoemaker after Gene’s tragic death in an automobile accident in Australia in 1997. India’s Chandrayaan-1 had a size and payload scope similar to Clementine. The selection of the LCROSS impactor as a low-cost, fast-tracked, limited objectives mission further extended use of the Clementine paradigm.
The Faster-Better-Cheaper mission model, once panned by some in the spaceflight community, is now recognized as a valid mode of operations, absent the emotional baggage of that name.31 A limited-objectives mission that flies is more desirable than a gold-plated one that sits forever on the drawing board. While some missions do require significant levels of fiscal and technical resources to attain their objectives, an important lesson of Clementine is that for most scientific and exploration goals, “better” is the enemy of “good enough.” Space missions require smart, lean management; they should not be charge codes for feeding the beast of organizational overhead. Clementine was lean and fast; perhaps we would have made fewer mistakes had the pace been a bit slower, but despite its shortcomings, the mission gave us a large, high-quality dataset, one still used extensively to this day. In recognition of its substantial accomplishments, the Naval Research Laboratory transferred the Clementine engineering model to the Smithsonian in 2002, where it was put on display in the National Air and Space Museum, suspended above the display of the Apollo Lunar Module.
It is probably not too much of an exaggeration to say that Clementine changed the direction of the American space program. After the failure of SEI in 1990–92, NASA was left with no long-term strategic direction. For the first time in its history (but alas, not the last), the agency had no follow-on program to the shuttle/station, despite attempts by Dan Goldin and others to secure approval for a human mission to Mars, an insurmountable challenge both technically and financially. This programmatic stasis continued until 2003, when the tragic loss of the space shuttle Columbia led to a top-down review of US space goals. Because Clementine had documented the strategic value of the Moon, the lunar surface once again became an attractive destination for future robotic and human missions. The resulting Vision for Space Exploration (VSE) in 2004 made the Moon the centerpiece of a new American effort beyond low Earth orbit. Though Mars was declared as an eventual (not ultimate) space objective, specific activities to be done on the Moon were detailed in the VSE, particularly with regard to the use of its material and energy resources to build a sustainable program. Regrettably, as I will detail, various factors combined to subvert the Vision, thereby ending any strategic direction for America’s civil space program.
Clementine was a watershed, a hinge point that forever changed the nature of space policy debates. We now recognize a fundamentally different way forward in space—one of extensibility, sustainability, and permanence. Once an outlandish idea found in science fiction, we now know that lunar resources can be used to create new capabilities in space, a welcome genie that cannot be put back in the bottle. Americans need to ask why their national space program was diverted from such a sustainable path. We cannot afford to remain behind while others plan and fly missions to understand and exploit the Moon’s resources. Our path forward into the universe is clear. In order to remain a world leader in space, and a participant in and beneficiary of a new cislunar economy, the United States must again direct its sights and energies toward the Moon.