The recent successful interception of a ballistic missile in flight recalls earlier fevered debates of the 1980s and 90s over the “feasibility” of missile defense. Back then, “settled science” declared that missile defense was either impossible, or of such technical difficulty as to make the eventual deployment of a working system extremely unlikely. Although such “expert” judgment aligned more with political inclination than with sound technical assessment, it served its intended and useful media purpose of providing “proof” that SDI (Strategic Defense Initiative), initiated in 1983, would never work. A similar set of circumstances exists today, as development and use of space resources to create new spaceflight capabilities faces familiar objections and roadblocks.
Leveraging access and capability in space through the use of the material and energy resources found in space gained traction during the initial study phases of SDI. Such a connection is logical – SDI was a program designed to establish a significant space presence by using a number of satellite assets with widely varying requirements (depending on their function: observation, monitoring, interdiction, or protection). Research initially focused on the deployment of unmanned systems from Earth, but it soon became apparent that the significant mass requirements needed by space-based missile defense put a strain on then-existing launch costs and capabilities. Most mass (weight) required in space is “dumb” mass (i.e., low information density) such as bulk material for shielding and protection, and propellant for the movement of assets throughout near-Earth space. Extended human missions beyond LEO faced similar difficulties. Thus, finding and using materials and energy from space-based sources became a topic of interest in both areas of research.
In 1983, a group of planetary scientists and defense space experts considered the acquisition and uses of space resources to support our national strategic needs. The report from this meeting recommended a research program designed to assess whether, and how, space resources from near-Earth asteroids and the Moon might be accessed and deployed. Their work considered a variety of needs for such a system, including orbital transfer vehicles (to move payloads between low Earth orbit and higher regions of cislunar space), propellant depots, and the use of bulk material to shield and protect satellite assets. Participants in the workshop included people from the NASA Johnson Space Center who were studying lunar base concepts, so the marriage of these two streams of inquiry occurred very early. This cross-fertilization continued with additional meetings and conferences during the 1980s, where the problems and benefits of using space resources were further examined.
Meanwhile, research in SDI techniques continued apace. Although a variety of approaches were studied, space-based missile defense architectures eventually moved from laser and particle beam weapons to kinetic energy interceptors, largely because there was less technical risk associated with such a system (we already knew that a high-velocity impact could destroy a target). A group at Lawrence Livermore National Laboratory led by Dr. Edward Teller developed one such system called Brilliant Pebbles (BP). The Brilliant Pebble concept used swarms of small satellites, each with its own independent sensing, computing, and propulsion capabilities. The spacecraft were small (“pebbles” – each a few 10s of kg) yet possessed significant autonomy and computing capacity (“brilliant”); when deployed by the thousands, they would create robust redundancy and thus, reliability. The Brilliant Pebbles concept took advantage of a variety of new advanced technologies already developed to support defense applications and applied them to the deep space mission of strategic missile defense.
In 1989, President George H. W. Bush announced the Space Exploration Initiative (SEI) that included a permanent return to the Moon and a future human mission to Mars. The Synthesis Group, chaired by Astronaut Thomas Stafford, was convened in 1990 by the White House to study architectures for this program. The assembled group considered a variety of architectures made up from “waypoints” that described a capability or a theme; several waypoint themes featured the use of space resources, including the Fuels, Energy and Asteroids Waypoints. It was proposed to use materials and energy from both asteroids and the Moon to augment capabilities for people on the Moon and in deep space. I was part of this study team and participated in defining these waypoints. Another member of the team was Dr. Stewart Nozette, who had edited the 1983 workshop report and was then employed by Lawrence Livermore on Brilliant Pebbles.
Nozette’s idea – testing the BP sensor suite and providing operational experience with a small, semi-autonomous spacecraft by flying a “Brilliant Pebble” – was the concept that became Clementine, the 1994 mission that flew to the Moon. In the course of 74 days, Clementine globally mapped the Moon in 11 colors in the visible and near-infrared, allowing us to map the location of resources (notably, iron and titanium) on the Moon. But the real payoff came from an improvised experiment that beamed radio waves into the dark regions near the lunar poles. By measuring the properties of reflected radio echoes from the poles, we found that water ice, long suspected by some planetary scientists, exists in the dark areas.
Some scientists were not convinced that ice was what we’d detected, largely on the grounds that the enhancement in same sense echoes seen in the Clementine radar data could also be cause by surface roughness. Thus began a decade-long debate over the meaning of the Clementine results. The debate was eventually resolved with additional data from subsequent missions, such as Lunar Prospector (which found enhanced hydrogen at the poles), India’s Chandrayaan-1 mission (that found polar ice using imaging radar), the LRO mission (a variety of spectral and remote evidence for water) and finally, the LCROSS spacecraft (which kicked up water ice particles and vapor by the impact of an empty Centaur stage near the south pole of the Moon). It is now widely agreed that significant amounts of water ice exist near the lunar poles, although its form and distributions remain unknown.
Although the presence of water on the Moon generated a variety of plans to develop and use it, skepticism about using space resources remains. The essence of these complaints sound very familiar to anyone conversant with the debates over SDI in the 1980s – “it’s too expensive and it won’t work.” But more significantly, both developments – SDI and exploiting space resources – upset the existing paradigm. For SDI, the idea that we should actively defend ourselves rather than passively await our annihilation actually offended those devoted to the doctrine of Mutual Assured Destruction – the strategic paradigm under which we have lived for over half a century. As for space resource utilization, much of the current skepticism stems from the notion that we can somehow lower launch costs to a point, where everything we need in space, can be cheaply launched from Earth. One can see how this concept would be supported by much of the aerospace industry, as the development and operation of launch vehicles is a path of operation with known risks and rewards, while developing lunar propellant or making a lunar base through 3-D printing of lunar regolith, sounds like risky science-fiction.
The path to new and revolutionary capabilities is often littered with stumbling blocks and naysayers. The success of the recent missile defense test reminds us that something worthwhile, though extremely difficult, can usually be achieved (and hopefully, achieved in time). Space resource utilization is connected to both space-based defense and to human spaceflight. And in both cases, significant mass is needed in deep space, in much larger quantities than is practicable to launch solely from Earth’s surface. So, by dedicating our efforts to increase our capabilities in both of these areas, they will become both synergistic and mutually supporting.