Review of Roland Lehoucq, “Toward Asteroid Exploration”, in Visions, Ventures, Escape Velocities: A Collection of Space Futures, edited by Ed Finn and Joey Eschrich, (Center for Science and Imagination, Arizona State University, 2017): 165-172 — Download here. Reviewed by Sara L. Uckelman. (Read the review of the anthology).
Mars is usually the destination that captures our collective imagination in the context of human-possible space exploration. Asteroids are, if anything, objects of destruction of humanity, not objects of their preservation. And yet, as Ramez Naam explored in his story “The Use of Things” (read the review), asteroids may in fact provide us with the crucial stepping stones humanity needs. In the nonfiction companion piece to Naam’s story, Lehoucq explores the conditions under which asteroid exploration can be undertaken.
First, there is the paradox that any asteroid to be close enough to be of use may also be, potentially, close enough to be of danger. To determine which are threats and which are not, we “must be able to…accurately predict their flight path” (p. 165). Only the “near-earth asteroids” (NEA) are suitable for the type of exploration that Naam writes about; but there are plenty of options within that subset: “As of 2016, around 15,000 NEAs are known” (p. 166), and it is quite likely that there are many, many more, especially ones of smaller size which are harder to detect.
In addition to knowing where they are and how big they are (and how fast they are rotating!) we also need to know their geological make-up — what kinds of minerals are present, how dense is the asteroid, how porous, how much water does it (possibly) contain? The difficulty here is that “this kind of information is very difficult to accurately determine using Earth-based surveys; it will require physical sampling” (p. 166). Because of their near-earth status, however, it is possible to send surveying equipment to the asteroids and back, and a handful of such missions have already been successful.
Once the likely candidates have been identified, they must in fact be mined — for water, for gold, for nickel-iron alloys. Lehoucq is optimistic about the technological possibilities here:
Such ambitious plans may seem like the mirage of a far-distant future, but the groundwork for a realistic implementation of asteroid mining is already being laid. In 2012, NASA’s Institute for Advanced Concepts announced the Robotic Asteroid Prospector project, which will examine and evaluate the feasibility of asteroid mining in terms of means, methods, and systems (p. 168).
The mining activity will have to be run by robots, programmed not only to run the mining equipment but also to separate the output, and to box it up for use elsewhere. All of this activity requires energy, which raises the next issue: How to provide that energy. Lehoucq offers two feasible options: solar power, for below 100 kilowatts (p. 170), and small fission nuclear reactors, for more efficient energy production (p. 170).
The remaining question, then, is what to do with the materials once mined: Do they get sent back to earth (probably the more likely, at least in initial stages), or are they processed on the asteroid to provide the materials for further space exploration (as in Naam’s story)? That question is one only the future can answer.
This may seem a tall task: But the point of Lehoucq’s article is that each individual step is not only feasible, but we already have been taking steps towards achieving it. When it comes to asteroids, mankind needn’t make one giant leap all in one go, but can many small steps, one by one.