- Status Report
- May 31, 2023
Testimony of Dr. Paul D. Spudis: Senate Hearing on “Lunar Exploration”
Testimony of Dr. Paul D. Spudis, Planetary Scientist, Lunar and Planetary Institute
Mr. Chairman and members of the committee, thank you for inviting me here today to testify on the subject of lunar exploration and the US space program.
I want to discuss a new destination for America in space – the Moon. Although we conducted our initial visits to that body over 30 years ago, we have recently made several important discoveries that indicate a return to the Moon offers many advantages and benefits to the nation. In addition to being a scientifically rich object for study, the Moon offers abundant material and energy resources, the feedstock of an industrial space infrastructure. Once established, such an infrastructure will revolutionize space travel, assuring us of continuous, routine access to cislunar space (i.e., the space between and around Earth and Moon) and beyond. The value of the Moon as a space destination has not escaped the notice of other countries – at least four new robotic missions are currently being flown or prepared by Europe, India, Japan, and China and advanced planning for human missions in many of these countries is already underway.
With me here today is Dr. Bill Stone, a prominent explorer and expedition leader. The points which I will present represent our joint thinking as to WHY the nation needs to return to the Moon and why that return should take place NOW rather than later.
(1) NASA needs a politically viable mission and both Shuttle and ISS are losing appeal as “space exploration.” America needs a compelling space program!
Forty years ago, America made a decision to go to the Moon, starting from a state of primitive technology and vast ignorance. We accomplished this great feat within 8 years, giving us for the first time the ability to travel to another world. We now have a commercial launch industry that each year lifts a mass equivalent to an Apollo mission to geosynchronous orbit. Its mission accomplished, NASA looked to other programs to keep the dream of space flight alive. Shuttle was presented as an affordable means to low Earth orbit. Space Station was planned as both a laboratory in orbit and a way station to the rest of the Solar System. Meanwhile, the Moon largely was ignored as an object worthy of study in its own right, as a natural space station to provision and enable space flight farther a field, and as a center of commerce and national security.
NASA’s current problems are partly technical, but mostly related to the fact that it no longer has a mission, as in its early “Days of Glory.” Forty years ago, its mission was to beat the Soviets to the Moon, a clear goal articulated by the national leadership and presented with a deadline (by the end of the decade). Now, the agency looks for a mission, but has yet to find one, at least, one perceived by government and the American people as worthy of long-term commitment. In the absence of such a goal, we drift between projects and have some success, but nothing is cumulative, where each step builds upon and extends the capability of the step preceding it.
A new national focus in space must have a direct and clear benefit to the American public. Pure science and the search for life are not defensible justifications. As Dr. Stone has put it recently, what the nation needs is a Lewis and Clark-class mission – one that opens the frontier to the expansion of the external commerce of the United States (through the general participation of its people and industry) and to the enhancement of the security of the nation. The recent loss of Shuttle Columbia has only heightened the perception that we are adrift in space, with no long-term goals or direction. Death and risk are part of life and not to be feared, especially in the field of exploration, but for death to have meaning, the objectives of such exploration must be significant. Great nations do great (and ambitious) things. The Apollo project was one such example; a return to the Moon to learn how to live off-planet can be another.
(2) Human missions to Mars currently are too technically challenging and too expensive to be feasible national space goals within the next decade.
Although much attention is given to the idea of human missions to Mars as the next big goal in space, such a journey is at present beyond our technical and economic capabilities. The large amount of discretionary money needed for such a journey is simply not available in the federal budget nor would it be wisely spent on going to Mars in an Apollo-style “flags-and-footprints” program. The principal justification of a manned Mars mission is scientific and such a rationale cannot sustain a large investment in the eyes of the taxpaying public. Mars awaits exploration by people some time in the future, after we have learned how to live and work routinely in space and how to make use of the resources available on other worlds to break the costly ties to Earth-based rocket transport of materiel.
American government has a history of supporting long-term, big engineering projects, provided that such efforts contribute to goals related to national and economic security (e.g., the Panama Canal, the Apollo program). The nation needs a mission whose purpose relates to these important, enduring objectives. A return to the Moon is such a goal. Indeed, it is a necessary goal and the only economically-justifiable goal at this time.
(3) Other possible destinations for people in space are perceived to be either too uninteresting (asteroids) or too arcane (telescopes in deep space) to enjoy “widespread” national support.
Among other possible space destinations for people are the Lagranian (L-) points (imaginary spots in space that move in sync with Earth, Moon, Sun or other objects) and the minor planets, better known as asteroids. The Lagranian points have many advantages for the staging of missions that go elsewhere, but the only thing they contain is what we put there. In that sense, they are similar to low Earth orbit and significant activity at the L-points, without travel beyond them to more interesting destinations, would resemble another International Space Station put in a different location. Asteroids have great potential for exploration and exploitation of resources and may eventually become an important destination as a class of objects. However, the times required to reach asteroids can equal the months-long transit times for Mars missions, without the variety of activities that could be undertaken at the end of such a trip. Thus, although specialized missions to these destinations can be imagined, they do not present a compelling return on investment nor the scientific or operational variety that other missions possess.
(4) The Moon is close, accessible with existing systems, and has resources that we can use to create a true, economical space-faring infrastructure
The Moon is a scientific and economic treasure trove, easily reachable with existing systems and infrastructure that can revolutionize our national strategic and economic posture in space. The dark areas near the poles of the Moon contain significant amounts (at least 10 billion tons) of hydrogen, most probably in the form of water ice. This ice can be mined to support human life on the Moon and in space and to make rocket propellant (liquid hydrogen and oxygen). Moreover, we can return to the Moon using the existing infrastructure of Shuttle and Shuttle-derived launch systems and the ISS for only a modest increase in the space budget within the next five years.
The “mission” of this program is to go to the Moon to learn how to use off-planet resources to make space flight easier and cheaper in the future. Rocket propellant made on the Moon will permit routine access to cislunar space by both people and machines, which is vital to the servicing and protection of national strategic assets and for the repair and refurbishing of commercial satellites. The availability of cheap propellant in low Earth orbit would completely change the way engineers design spacecraft and the way companies and the government think of investing in space assets. It would serve to dramatically reduce the cost of space infrastructure to both the government and to the private sector, thus spurring economic investment (and profit).
(5) The Moon is a scientific treasure house and a unique resource, on which important research, ranging from planetary science to astronomy and high-energy physics, can be conducted.
Generally considered a simple, primitive body, the Moon is actually a small planet of surprising complexity. Moreover, the period of its most active geological evolution, between 4 and 3 billion years ago, corresponds to a “missing chapter” of Earth history. The processes that work on the Moon – impact, volcanism, and tectonism (deformation of the crust) – are the same ones that affect all of the rocky bodies of the inner solar system, including the Earth. Because the Moon has no atmosphere or running water, its ancient surface is preserved in nearly pristine form and its geological story can be read with clarity and understanding. Because the Moon is Earth’s companion in space, it retains a record of the history of this corner of the Solar System, vital knowledge unavailable on any other planetary object.
Of all the scientific benefits of Apollo, appreciation of the importance of impact, or the collision of solid bodies, in planetary evolution must rank highest. Before we went to the Moon, we had to understand the physical and chemical effects of these collisions, events completely beyond the scale of human experience. Of limited application at first, this new knowledge turned out to have profound consequences. We now believe that large-body collisions periodically wipe out species and families on Earth, most notably, the extinction of dinosaurs 65 million years ago. The telltale residue of such large body impacts in Earth’s past is recognized because of knowledge we acquired about impact from the Moon. Additional knowledge still resides there; while the Earth’s surface record has been largely erased by the dynamic processes of erosion and crustal recycling, the ancient lunar surface retains this impact history. When we return to the Moon, we will examine this record in detail and learn about its evolution as well as our own.
Because the Moon has no atmosphere and is a quiet, stable body, it is the premier place in space to observe the universe. Telescopes erected on the lunar surface will possess many advantages. The Moon’s level of seismic activity is orders of magnitude lower than that of Earth. The lack of an atmosphere permits clear viewing, with no spectrally opaque windows to contend with; the entire electromagnetic spectrum is visible from the Moon’s surface. Its slow rotation (one lunar day is 708 hours long, about 28 terrestrial days) means that there are long times of darkness for observation. Even during the lunar day, brighter sky objects are visible through the reflected surface glare. The far side of the Moon is permanently shielded from the din of electromagnetic noise produced by our industrial civilization. There are areas of perpetual darkness and sunlight near the poles of the Moon. The dark regions are very cold, only a few tens of degrees above absolute zero and these natural “cold traps” can be used to passively cool infrared detectors. Thus, telescopes installed near the lunar poles can both see entire celestial hemispheres all at once and with infrared detectors, cooled for “free,” courtesy of the cold traps.
(6) Hydrogen, probably in the form of water ice, exists at the poles of the Moon that can be extracted and processed into rocket propellant and life-support consumables
The joint DoD-NASA Clementine mission was flown in 1994. Designed to test sensors developed for the Strategic Defense Initiative (SDI), Clementine was an amazing success story. This small spacecraft was designed, built, and flown within the short time span of 24 months for a total cost of about $150 M (FY 2003 dollars), including the launch vehicle. Clementine made global maps of the mineral and elemental content of the Moon, mapped the shape and topography of its surface with laser altimetry, and gave us our first good look at the intriguing and unique polar regions of the Moon. Clementine did not carry instruments specifically designed to look for water at the poles, but an ingenious improvisation used the spacecraft communications antenna to beam radio waves into the polar regions; radio echoes were observed using the Deep Space Network dishes. Results indicated that material with reflection characteristics similar to ice are found in the permanently dark areas near the south pole. This major discovery was subsequently confirmed by a different experiment flown on NASA’s Lunar Prospector spacecraft four years later in 1998.
The Moon contains no internal water; all water is added to it over geological time by the impact of comets and water-bearing asteroids. The dark areas near the poles are very cold, only a few degrees above absolute zero. Thus, any water that gets into these polar “cold traps” cannot get out so over time, significant quantities accumulate. Our current best estimate is that over 10 billion cubic meters of water exist at the lunar poles, an amount equal to the volume of Utah’s Great Salt Lake – without the salt! Although hydrogen and oxygen can be extracted directly from the lunar soil (solar wind hydrogen is implanted on the dust grains of the surface, allowing the production of propellant and water directly from the bone-dry dust), such processing is difficult and energy-expensive. Polar water has the advantage of already being in a concentrated useful form, greatly simplifying scenarios for lunar return and habitation. Broken down into hydrogen and oxygen, water is a vital substance both for human life support and rocket propellant. Water from the lunar cold traps advances our space-faring infrastructure by creating our first space “filling station.”
The poles of the Moon are useful from yet another resource perspective – the areas of permanent darkness are in proximity to areas of near-permanent sunlight. Because the Moon’s axis of rotation is nearly perpendicular to the plane of the ecliptic, the sun always appears on or near the horizon at the poles. If you’re in a hole, you never see the Sun; if you’re on a peak, you always see it. We have identified several areas near both the north and south poles of the Moon that offer near-constant sun illumination. Moreover, such areas are in darkness for short periods, interrupting longer periods of illumination. Thus, an outpost or establishment in these areas will have the advantage of being in sunlight for the generation of electrical power (via solar cells) and in a benign thermal environment (because the sun is always at grazing incidence); such a location never experiences the temperature extremes found on the lunar equator (from 100? to -150? C). The poles of the Moon are inviting “oases” in near-Earth space.
(7) Current launch systems, infrastructure, and space hardware can be adapted to this mission and we can be back on the Moon within five to seven years for only a modest increase in existing space budgets.
America built the mighty Saturn V forty years ago to launch men and machines to the Moon in one fell swoop. Indeed, this technical approach was so successful, it has dominated the thinking on lunar return for decades. One feature of nearly all lunar return architectures of the past twenty years is the initial requirement to build or re-build the heavy lift launch capability of the Saturn V or its equivalent. Parts of the Saturn V were literally hand-made, making it a very expensive spacecraft. Development of any new launch vehicle is an enormously expensive proposition. What is needed is an architecture that accomplishes the goal of lunar return with the least amount of new vehicle development possible. Such a plan will allow us to concentrate our efforts and energies on the most important aspects of the mission – learning how to use the Moon’s resources to support space flight.
One possible architecture for lunar return devised by the Office of Exploration at the Johnson Space Center has several advantages. First, and most importantly, it uses the Space Shuttle (or an unmanned derivative of it), augmented by existing expendable boosters, to deliver the pieces of the lunar spacecraft to orbit. Thus, from the start, we eliminate one of the biggest sources of cost from the equation, the requirement to develop a new heavy-lift launch vehicle. This plan uses existing expendable launch vehicle (ELV) technology to deliver the cargo elements of the lunar return to low Earth orbit – lander, habitat, and transfer stage. Assembled into a package in Earth orbit, these items are then transferred to a point about 4/5 of the way to the Moon, the Moon-Earth Lagranian point 1 (L1). The L1 point orbits the Earth with the Moon such that it appears “motionless” to both bodies. Its non-motion relative to Earth and Moon has the advantage of allowing us to wait for favorable alignments of these bodies and the Space Station in various phases of the mission. Because there is no requirement for quick transit, cargo elements can take advantage of innovative technologies such as solar electric propulsion and weak stability boundaries between Earth, Sun, and Moon to make long, spiraling trips out to L1, thus requiring less propellant mass. These unmanned cargo spacecraft can take several months to get to their destinations. The habitat module can be landed on the Moon by remote control, activated, and await the arrival of its occupants from Earth.
The crew is launched separately on a Shuttle launch and uses a chemical stage and a quick transfer trajectory to reach the L1 depot in a few days. The crew then transfers to the lunar lander/habitat, descends to the surface and conducts the surface mission. As mentioned above, the preferred landing site is an area near one of the Moon’s poles; the south pole is most attractive from the perspective of science and operations (see the attached “Shackleton Crater Expedition” proposal submitted to the committee by Dr. Stone). The goal of our mission is to learn how to mine the resources of the Moon as we build up surface infrastructure to permit an ever-larger scale of operations. Thus, each mission brings new components to the surface and the size and capability of the lunar outpost grows over time. Most importantly, the use of lunar-derived propellants means that more than 80% of the spacecraft weight on return to Earth orbit need not be brought from Earth. A properly designed mission will return to Earth not only with sufficient fuel to take the craft back to the Moon for another run, but also to provide a surplus for sale in low Earth orbit. It is this act that creates the Earth-Moon economy and demonstrates a positive return on investment.
On return, the L1 depot provides a safe haven for the crew while they wait several days for the orbital plane of ISS to align itself with the return path of the crew vehicle. Rather than directly entering the atmosphere as Apollo did, the crew return vehicle uses aerocapture to brake into Earth orbit, rendezvous with the ISS, and thus, it becomes available for use in the next lunar mission.
In addition to its technical advantages, this architecture offers important programmatic benefits. It does not require the development of a new heavy lift launcher. We conduct our lunar mission from the ISS and return to it afterwards, making the Station an essential component of humanity’s movement into the Solar System. The use of the L1 point as a staging depot allows us to wait for proper alignments of the Earth and Moon; the energy requirements to go nearly anywhere beyond this point are very low. The use of newly developed, low-thrust propulsion (i.e., solar-electric) for cargo elements drives new technology development. We will acquire new technical innovation as a by-product of the program, not as a critical requirement of the architecture.
The importance of using the Shuttle or Shuttle-derived launch vehicles and commercial launch assets in this architecture should not be underestimated. Costs in space launch are almost completely dominated by the costs of people and infrastructure. To create a new launch system requires new infrastructure, new people, new training. Such costs can make up significant fractions of the total program. By using existing systems, we can concentrate our resources on new equipment and technology, focused on the goal of finding, characterizing, processing, and using lunar resources as soon as possible.
(8) A return to the Moon gives the nation a challenging mission and creates capability for the future, by allowing us to routinely travel at will, with people, throughout the Earth-Moon system.
Implementation of this objective for our national space program would have the result of establishing a robust transportation infrastructure, capable of delivering people and machines throughout cislunar space. Make no mistake – learning to use the resources of the Moon or any other planetary object will be a challenging technical task. We must learn to use machines in remote, hostile environments, working under difficult conditions with ore bodies of small concentration. The unique polar environment of the Moon, with its zones of near-permanent illumination and permanent darkness, provides its own challenges. But for humanity to have a future, we must learn to use the materials available off-planet. We are fortunate that the Moon offers us a nearby, “safe” laboratory to take our first steps in using space resources. Initial blunders in mining tactics or feedstock processing are better practiced at a location three days from Earth than from one many months away.
A mission learning to use these lunar resources is scalable in both level of effort and the types of commodities to be produced. We begin by using the resources that are the easiest to extract. Thus, a logical first product is water derived from the lunar polar deposits. Water is producible here regardless of the nature of the polar volatiles – ice of cometary origin is easily collected and purified, but even if the polar materials are composed of molecular hydrogen, this substance can be combined with oxygen extracted from rocks and soil (through a variety of processes) to make water. Water is easily stored and used as a life-sustaining substance for people or broken down into its constituent hydrogen and oxygen for use of rocket propellant.
Although we currently possess enough information to plan a lunar return now, investment in a few robotic precursors would be greatly beneficial. We should map the polar deposits of the Moon from orbit using imaging radar to “see” the ice in the dark regions. Such mapping could establish the details of the ice location and its thickness, purity, and physical state. The next step should be to land small robotic probes to conduct in place chemical analyses of the material. Although we expect water ice to dominate the deposit, cometary cores are made up of many different substances, including methane, ammonia, and organic molecules, all of which are potentially useful resources. We need to inventory these species, determine their chemical and isotopic properties, and their physical nature and environment. Just as the way for Apollo was paved by such missions as Ranger and Surveyor, a set of robotic precursor missions, conducted in parallel with the planning of the manned expeditions, can make subsequent human missions safer and more productive.
After the first robotic missions have documented the nature of the deposits, focused research efforts would be undertaken to develop the machinery needed to be transported to the lunar base as part of the manned expedition. There, human-tended processes and principles will be established and validated, thus paving the way to commercialization of the mining, extraction and production of lunar hydrogen and oxygen.
(9) This new mission will create routine access to cislunar space for people and machines, which directly relates to important national economic and strategic goals.
By learning space survival skills close to home, we create new opportunities for exploration, utilization, and wealth creation. Space will no longer be a hostile place that we tentatively visit for short periods; it becomes instead a permanent part of our world. Achieving routine freedom of cislunar space makes America more secure (by enabling larger, cheaper, and routinely maintainable assets on orbit) and more prosperous (by opening an essentially limitless new frontier.)
As a nation, we rely on a variety of government assets in cislunar space, ranging from weather satellites to GPS systems to a wide variety of reconnaissance satellites. In addition, commercial spacecraft continue to make up a multi-billion dollar market, providing telephone, Internet, radio and video services. America has invested billions in this infrastructure. Yet at the moment, we have no way to service, repair, refurbish or protect any of these spacecraft. They are vulnerable to severe damage or permanent loss. If we lose a satellite, it must be replaced. From redesign though fabrication and launch, such replacement takes years and involves extraordinary investment in the design and fabrication so as to make them as reliable as possible.
We cannot now access these spacecraft because it is not feasible to maintain a man-tended servicing capability in Earth orbit – the costs of launching orbital transfer vehicles and propellant would be excessive (it costs around $10,000 to launch one pound to low Earth orbit). Creating the ability to refuel in orbit, using propellant derived from the Moon, would revolutionize the way we view and use our national space infrastructure. Satellites could be repaired, rather than abandoned. Assets can be protected rather than written off. Very large satellite complexes could be built and serviced over long periods, creating new capabilities and expanding bandwidth (the new commodity of the information society) for a wide variety of purposes. And along the way, we will create opportunities and make discoveries.
A return to the Moon, with the purpose of learning to mine and use its resources, thus creates a new paradigm for space operations. Space becomes a part of America’s industrial world, not an exotic environment for arcane studies. Such a mission ties our space program to its original roots in making us more secure and more prosperous. But it also enables a broader series of scientific and exploratory opportunities. If we can create a spacefaring infrastructure that can routinely access cislunar space, we have a system that can take us to the planets.
(10) The infrastructure created by a return to the Moon will allow us to travel to the planets in the future more safely and cost effectively.
This benefit comes in two forms. First, developing and using lunar resources can enable flight throughout the Solar System by permitting the fueling the interplanetary craft with materiel already in orbit, saving the enormous costs of launch from Earth’s surface. Second, the processes and procedures that we learn on the Moon are lessons that will be applied to all future space operations. To successfully mine the Moon, we must learn how to use machines and people in tandem, each taking advantage of the other’s strengths. The issue isn’t “people or robots?” in space; it’s “how can we best use people and robots in space?” People bring the unique abilities of cognition and experience to exploration and discovery; robots possess extraordinary stamina, strength, and sensory abilities. We can learn on the Moon how to best combine these two complementary skill mixes to maximize our exploratory and exploitation abilities.
Return to the Moon will allow us to regain operational experience on another world. The activities on the Moon make future planetary missions less risky because we gain this valuable experience in an environment close to Earth, yet on a distinct and unique alien world. Systems and procedures can be tested, vetted, revised and re-checked. Exploring a planet is a difficult task to tackle green; learning to live and work on the Moon gives us a chance to crawl before we have to walk in planetary exploration and surface operations.
The establishment of the Earth-Moon economy may be best accomplished through an independently organized federal expedition along the lines of the Lewis and Clark expedition. Dr. Stone, who is eminently qualified to lead such an expedition, has prepared the Shackleton Crater Expedition proposal (attached to this testimony) to elaborate upon this alternative organizational strategy. One of the fundamental tenets of this approach is to take a business stance on cost control with the objective of demonstrating a positive return on investment. Such an approach would take advantage of the best that NASA and other federal agencies have to offer, while streamlining the costs through a series of hard-nosed business approaches.
A lunar program has many benefits to society in general. America needs a challenging, vigorous space program. Such a program has served as an inspiration to the young for the last 50 years and it can still serve that function. It must present a mission that inspires and enriches. It must relate to important national needs yet push the boundaries of the possible. It must serve larger national concerns beyond scientific endeavors. A return to the Moon fulfills these goals. It is a technical challenge to the nation. It creates security for America by assuring access and control of our assets in cislunar space. It creates wealth and new markets by producing commodities of great commercial value. It stimulates and inspires the next generation by giving them the chance to travel and experience space flight for themselves. A return to the Moon is the right destination for America.
Thank you for your attention.