Book Review: The Case for Space
Michael Goff medium.com
Robert Zubrin’s new book, The Case for Space: How the Revolution in Spaceflight Opens up a Future of Limitless Possibility, is an excellent read that indeed makes the case the title advertises. The…
https://miro.medium.com/v2/1*m-R_BkNf1Qjr1YbyOIJY2w.png
Medium
Robert Zubrin’s new book, The Case for Space: How the Revolution in Spaceflight Opens up a Future of Limitless Possibility, is an excellent read that indeed makes the case the title advertises.

The book makes its case in two parts. In the first, Zubrin outlines a path from today’s commercial spaceflight revolution through the industrialization and settlement of Earth’s orbital space, the Moon, Mars, asteroids, the outer planets, interstellar space, and finally the potential for planetary terraforming. The second part of the book argues why a positive future for humanity necessarily entails space settlement.

The Case for Space is all throughout a clear and thorough read. Zubrin covers quite a bit of ground in 335 pages, and he does so efficiently. Each major topic is covered well, and there is no sense of lingering on a topic longer than necessary. Part I of the book is a fairly thorough introduction to the major topics in space settlement. For the reader who is not familiar with space settlement, the book is as good an introduction as any I have seen. It covers almost everything on the subject that I would regard as important, and not much that I don’t think is important. The first four chapters or so stay mostly grounded in ventures that we could be seriously pursuing today, while the subsequent four chapters move on to possibilities for the farther future that might not be feasible for generations or centuries.

Part II is Zubrin’s argument for the necessity of space settlement. There are some arguments I would make that he doesn’t, and not every point he makes I find compelling, but in general it is a strong case. It is not the case one generally hears from NASA or the popular press, and he makes plenty of controversial statements that might rub some readers the wrong way. I will make some specific comments about both the underlying ideology of the book and some technical aspects of space settlement below.

The target audience for The Case for Space is probably a well-educated reader who is receptive to big ideas and interested in space. I did not need to be persuaded, having long been a believer in space colonization, and I don’t have a very good sense of how convincing the book would be to a skeptic or someone who is uninterested in space. For me, one of the major benefits is that the book helps articulate things that I already believed but had not articulated well before.

There are some mathematics and technical details throughout the book: enough that the less technically inclined reader may gloss over them, but not so much that they present a serious barrier to understanding the overall narrative for said reader. For the more technically inclined reader, the rigor is welcome in a genre that is often lacking in rigor.

The reader should also be aware that much of the book represents Zubrin’s ideas, which at times can be rather idiosyncratic. His writing and speaking is a volcanic eruption of thoughts, always interesting but often needed to be taken with a grain of salt. I didn’t see anything in the book that appears to be clearly wrong, though there are a few things I would disagree with, some of which I will note below.

Overall, it’s a great book. The greatest virtue is the obvious creativity and passion that Zubrin brings to the subject. I highly recommend it to anyone with even a passing interest in the subject. And I recommend that everyone have an interest in the humanity’s future in space.

The book is The Case for Space: How the Revolution in Spaceflight Opens up a Future of Limitless Possibility by Robert Zubrin. Copyright 2019, published by Prometheus Books. 405 pages.

Following are some additional comments, first on some of the ideological issues that Zubrin raises, and then on some technical issues. I would suggest stopping here if you have not read the book and intend to.

Ideology

Zubrin’s makes several arguments for why expansion into space is desirable and necessary, though there are a few that stand out as particularly interesting to me, as they touch on issues that I think a lot about, often in the context of energy policy and urban design. I will focus on the two arguments that I find most interesting.

The first is the frontier argument, rooted in the Frontier Thesis of Frederick Jackson Turner. Without a terrestrial frontier, Zubrin argues that the United States, and the Western World in general, has fallen into a state of complacency and stagnation. He cites several trends, including chronic low economic growth, falling fertility, and an evident slowdown in technological advancement as warning signs that the wealthy and free countries of the world are falling off course. Zubrin believes that the opening of a new and ultimately endless frontier in space will be the revitalizing force that turns the trends toward stagnation around.

The topic of secular stagnation is a complex one with a wide range of poorly understood causes. There is nothing close to a consensus as to what the right response is, and there doesn’t even seem to be a consensus that stagnation is a problem (personally I have great difficulty understanding the logic of people who argue that slow economic growth and subreplacement fertility are good things). It is not at all clear that the opening of space settlement would have the catalyzing effect on terrestrial institutions that Zubrin hopes for, and indeed one could uncharitably characterize the idea as having a cargo cult quality to it.

Still, I feel that I am living in a society that is sleep-walking toward decline and am running short on ideas to turn things around. If nothing else, if terrestrial civilization enters into a state of protracted decline, a vanguard of dynamism on Mars or elsewhere in the Solar System might be humanity’s best chance for long term thriving.

The second argument, closely related to the first, is that expansion into space will push back against the wrong notion that prosperity on Earth is fixed and is something that we need to fight over.

Zubrin singles out the scarcity mindset as a primary root of evil in the world, implicating it (the perception of scarcity, not actual scarcity) in the world wars of the 20th century. We see it today in many forms: the alt-right’s agitation for racial conflict; trade protectionism, which imagines that jobs are some sort of scarce resource that we need to fight other countries for; immigration restrictionism, which imagines that national culture, which isn’t even a tangible thing, is somehow depleted by immigrants; and the NIMBY (not in my back yard) mindset that plagues municipal politics, just to name a few. Most of all, we see it in the environmental movement, which imagines the well-being of humans and non-human nature to be in conflict and that the only response is to curtail human numbers or prosperity.

There is a real need to push back against the scarcity mindset. Whether initiating space settlement will actually do so is not entirely clear, but as a dramatic illustration of abundance, it would have as good a chance as anything else I can think of.

One of the major debates within the space settlement community is whether near-term colonization efforts will best be served by building settlements on Mars or artificial habitats in orbit around Earth. These are the views espoused by Elon Musk and Jeff Bezos, respectively, in their endeavors, and of course there is nothing to prevent pursuing both routes simultaneously. Zubrin, who heads the Mars Society, wrote The Case for Mars, and developed the Mars Direct mission plan, falls squarely into the former camp, whereas I lean toward the latter. While Zubrin did not address the debate specifically in The Case for Space, I came away with some insights as to why he prefers Mars over other near-term destinations.

The following is my interpretation of what Zubrin argues, not what he says directly, so I apologize if I mischaracterize his views. In my comments last month on Jeff Bezos’ Blue Origin presentation, where he outlined a vision of space development rooted in Gerard K. O’Neill’s vision of orbital megastructures, I noted that a major hurdle in his or any space development scheme is that they tend to lack an understanding of the economic forces that might move people off-planet. All prosperous cities throughout history have existed in places that are strategic for commerce. For the foreseeable future, nowhere away from the surface of the Earth can be strategic for commerce. Under no scenario will launch costs be reduced to the point where sending goods by rocket is cost-comparable to sending goods by rail, truck, or cargo ship. Personal travel to and from space will, at best, have a cost comparable to supersonic business travel, which precludes the operation of a globally integrated business hub.

However, I suspect that Zubrin would say that this line of reasoning misses the point. We’re not trying to build the next Shenzhen or Dubai in space. Rather, we are trying to build the next Plymouth or Salt Lake City. The first generation of space colonies are designed to initiate new branches of civilization, not merely extend the increasingly homogeneous global civilization of today. To that end, the apparent drawbacks of settling on Mars — long supply chains, lack of integration into the global economy, and communication lag time — would in fact be advantages. I think this is an interesting line of reasoning, and it makes sense from a perspective of maximizing humanity’s long term potential, but it does continue to leave open the question of what economic forces will drive human expansion. Zubrin answers this by making it clear that far-sighted governments will play an essential role.

Technical Points

Considering how The Case for Space covers such a wide range of topics, it would be very hard to criticize it for omissions. There are a few areas where I would disagree or suggest some alternate pathways. Unlike Robert Zubrin, I am not a professional aerospace engineer, so with that caveat here we go.

The first two chapter discuss the spaceflight revolution and the near term possibilities it opens up, particularly on Earth. One of which is the possibility, as SpaceX has announced, of orbital flights connecting major cities on opposites sides of Earth within an hour. It is an exciting prospect that brings us closer to the vision of ecumenopolis, or the planetary city, as described by Constantinos Doxiadis, but rockets will remain expensive, geographically constrained due to noise and other logistical issues, and probably too energy intensive to be suitable for usage by the general public. There remains a missing link toward a fully integrated world economy that is also integrated with its orbiting space habitats, and I think the most likely candidate for the missing link is electromagnetic launch.

An electromagnetic launch system, such as the Lofstrom Loop, could potentially offer launch costs in the range of single dollars per kg, well below what any rocket system on the horizon could achieve. However, such a system would require major R&D and capital investments, not to mention political coordination for such a large structure. Thus, it makes sense only if there is already enough development in space to insure ongoing market demand. The Lofstrom Loop would, in turn, spur the development of large cities in orbit. The travel demands of such cities would then spur the development of orbital rings, as described by Paul Birch. With Earth encircled by several orbital rings and the transportation costs to space sufficiently low, we would see a tipping point where the economic advantages of being in space outweigh the disadvantages, moving the figurative center of gravity of human civilization into space.

Electromagnetics are not the only option for advanced space travel. Zubrin discusses skyhooks in the context of cheap launch from the Moon, though they may be an option around Earth too if coupled with a hypersonic plane. I’m surprised, though, that he didn’t mention the possibility of a lunar mass driver, which due to the Moon’s low escape velocity (2.4 km/s) and lack of atmosphere, would be much more feasible than a Lofstrom Loop on Earth. He is also generally skeptical of widespread usage of space-based solar power, due to high launch costs from Earth, but a highly automated system that manufactures and launches panels from the Moon would have the potential to have near-zero marginal cost. Still, for the short term on energy on Earth, I would put my money on the next generation of traditional solar, advanced nuclear fission, or fusion.

Speaking of fusion, Zubrin discuss the possibility of mining Helium-3 from the Moon or the gas giants, as the deuterium-Helium-3 fusion cycle would offer considerable technical advantages over the deuterium-tritium cycle that most fusion projects are pursuing today. I haven’t attempted to look at the numbers in detail, but I certainly need some convincing that the advantages of D-He3 would outweigh the considerable difficulty of mining He3 and transporting it to Earth.

Jumping ahead a bit, in Chapter 7, Zubrin outlines most of the major concepts available for an interstellar mission (a kugelblitz black hole-powered ship is the only option in mainstream physics that I know of that is not discussed). However, one overlooked option is transtellar space. While we don’t know much yet, one recent estimate is that there could be as many as 100,000 objects in transtellar space with at least 10^(-8) solar masses, or 0.3% Earth masses, for every main sequence star. As long as there is decent building material and fusion fuel, this is more than enough to set up a nice outpost. We would therefore have a path to settling the full galaxy by conducting voyages measured in light-weeks, not light-years. Furthermore, such transtellar objects (or artificial habitats built near them for reasons of alignment) would be good places to set up laser relay stations to establish interstellar railroads for solar sail ships, as described by Charles Quarra.

While on the subject of power beaming, obviously unsupported solar power is not useful beyond the outer solar system, but concentrators built near the Sun would be another option for powering cities in the Kuiper Belt or Oort Cloud, which in turn would be useful for constructing a Dyson Swarm.

In Chapter 8, on terraforming, Zubrin discusses iron fertilization as a method of sequestering excess carbon dioxide on Earth. As someone who works on energy and environmental policy as a day job, iron fertilization is one of those ideas like Georgism: maybe it has merit but I overlook it due to a lack of institutional support. I am fully supportive of doing more small scale experiments, but I think that Zubrin is overly dismissive of risks that remain unknown and is premature to call for doing it on a large scale. Having read Zubrin’s comments, I will take a closer look at the topic.

In Chapter 9, Zubrin discusses the Drake Equation, which was developed by the astronomer Frank Drake to estimate how many advanced civilizations might exist in the Milky Way. Using more recent knowledge on the abundance of planets, Zubrin estimates that were might be five million technological civilizations at a given time. Curiously, though, he does not discuss the Fermi Paradox, which asks, if there are so many technological civilizations out there, why do we not see any evidence of them?

While Zubrin discusses more advanced generations of SETI and astronomy which he believes will eventually reveal evidence of life and intelligence throughout the galaxy, he overlooks two key points which, in my opinion, make it unlikely that we will find the latter. The first is what the futurist Isaac Arthur calls the Dyson Dilemma. If a Kardeshev Type II civilization is to achieve its potential around a single star system, it will build something like a Dyson Swarm. Unlike a Dyson Sphere, which is a rigid object that probably can’t be structurally sound, a Dyson Swarm is simply so many artificial habitats around a star that they harvest a substantial fraction of the star’s energy output. The surfaces of naturally occurring solid objects in the solar system could accommodate, maybe, a few trillion people before crowding and waste heat disposal become serious problems, but a Dyson Swarm could hold quintillions. We have enough material in the Kuiper Belt and Oort Cloud to build enough habitats at Earth radius to make a Dyson Swarm, and a growth-oriented civilization is likely to do so. If the civilization engages in interstellar travel, which again is to be expected, and builds Dyson Swarms around many stars, there would be a whole region of the galaxy that is giving off anomalously high levels of infrared radiation. While we would have a hard time picking up ET’s equivalent of I Love Lucy today, we would certainly notice a cluster of Dyson Swarms.

The second overlooked issue is civilization lifetime. While we lack any real evidence on the topic, as with many things in the Drake Equation, I would expect that a civilization that achieves interstellar spaceflight would have nearly indefinite duration. Whatever might bring civilization to an end would have to strike the entire expanse, which might be hundreds of light years, simultaneously. If interstellar civilizations live indefinitely, build Dyson Swarms, and presumably have time to spread over the entirely galaxy or multiple galaxies, then it becomes impossible (or at least requires some highly convoluted explanations) that there is such a thing nearby that we fail to see. A recent search for such K3 civilizations over 100,000 galaxies has failed to turn any up.

The conclusion I come to is that building advanced civilizations must be much harder than indicated by a Drake Equation type analysis. Somewhere along the line, there must have been one or more great filters that we are lucky to have passed, and perhaps there are more between our present level and an interstellar civilization. Humanity may be the only chance for widespread intelligence in the Milky Way or even greater expanses of space, further reinforcing the need that we don’t mess it up.

The book is chock full of interesting ideas. I have much more to say about them, but I think this article has gotten long enough.