Book Review: To the End of the Solar System

James Dewar set out to the write the story of the nuclear rocket, and that’s exactly what he succeeded in doing. To the End of the Solar System is a nearly complete history of nuclear-thermal propulsion research from the discovery of radioactivity in the 1890s through the cancellation of the American research & development program in 1973. He discusses the work done in subsequent years, though through the book’s publication in 2004 that research was largely theoretical.1 Dewar consequently directs his attention to the period when nuclear propulsion was a near-term possibility.

It is not, primarily, a technical tale. The majority of the book focuses on the political, managerial, and bureaucratic aspects of the program. There is a good deal of technical detail, but ultimately the engineering challenges are not the biggest hurdle for those supporting nuclear propulsion. Securing long-term support and funding from industry and Congress will be much more difficult.

The book also necessarily focused on the American nuclear program, though addresses briefly Soviet work. Unfortunately, our knowledge of their program comes from only a handful of sources, sometimes contradicting one another. How much useful information we can glean from them is uncertain.

The Cold War played a major role in the development of the nuclear rocket, but the story begins well before the Russian Revolution. A number of early rocketry theorists, including Robert Goddard, Konstantin Tsiolkovsky, and Hermann Oberth speculated on using the energy released from radioactive decay to propel spacecraft, but both the quantity available and isotopic energy output was minute. Discussion remained entirely abstract and largely an aside in the development of rocket propulsion until after the Second World War.

The ultimate motivation was military. As atomic bombs grew larger and larger, existing aircraft and missile designs struggled to keep up. A handful of scientists floated nuclear options to deliver these weapons, either in aircraft, missile, or pulse-propulsion form. The Pentagon developed a nuclear airplane program as a joint venture between the Air Force and Atomic Energy Commission with the express goal of developing an aircraft capable of delivering a hydrogen bomb inside the Iron Curtain.

Oak Ridge National Laboratory hired a young physicist named Robert Bussard2 to work on the nuclear airplane project. Brussard did excellent work but insisted on studying nuclear rockets alongside his official duties. Through months of feverish lucubration, he developed some of the first viable nuclear rocket concepts. His classified publications attracted the interest of several prominent physicists. Teams formed at Los Alamos and Livermore National Laboratories to develop Bussard’s concepts. Los Alamos eventually came to favor nuclear turbojets, while Livermore concluded that nuclear rockets were more viable.

When Congress got involved a few years later, the need for nuclear aircraft or missiles was waning as bomb mass fell and chemical launcher capability grew. However, Washington was beginning to think about spaceflight, and decided to continue funding both programs. Ironically, the AEC assigned Los Alamos to study rockets and Livermore to study nuclear jet engines. These became Projects Rover and Pluto, respectively.

Los Alamos began constructing facilities at the Nevada Test Site to put their series of reactor designs through the paces. Each reactor was a hard-won concession from Congress, which was worried about just how many tests and iterations would be necessary to develop a viable system. Throughout the program, many in Washington opposed Project Rover or believed that it should be transferred to the civilian space program. NASA was very skeptical of the program, however, and so a small clique of Senators fought to keep it under AEC aegis. Ultimately NASA and the AEC found a reasonable compromise, forming a joint Space Nuclear Propulsion Office.

The early Space Race initially helped Rover’s prospects, as the Soviet Union sped ahead in missions and technological firsts. Nuclear propulsion would enable much more impressive projects, such as manned planetary landings, massive probes to the outer Solar System, space stations, and Lunar bases.

In Nevada, reactors were steadily improving. Their thrust and successful burn-time grew, though several failures occurred, including one which required an expensive clean-up effort. Through a series of redesigns, however, the test articles began to closely match the existing aerothermodynamic models. Better designs were coming, but a large question mark hovered over the program: when would Rover get a reactor in-flight test?

RIFT was well-named, as it became a political hot-button issue. Early concepts involved dumping the used reactor into the ocean or using it to perform orbital insertion as a Saturn upper stage. Both of these concepts were eventually abandoned on safety grounds, but did nothing to advance the issue in Congress.

Ultimately, nuclear rockets became a chicken-and-egg problem. Congress and NASA leadership did not want to approve a program that required nuclear propulsion until the technology was ready, but also hesitated to develop nuclear technology until a mission required it.

Much of the opposition stemmed from budgetary concerns. NASA was a rapidly-growing slice of the federal budget, competing with the Vietnam War and Great Society for a shrinking set of tax dollars. Recall that fiscal conservatism was once common in both political parties, rather than a fringe movement within one of them. Few wanted to commit to the large, expensive missions which nuclear propulsion would enable (such missions being prohibitively expensive—in the extreme—with chemical propulsion).

The concept of preeminence rapidly fell out of favor. Washington decided that Apollo would be the extent of trying to upshow the Soviet with big flashy projects. After Skylab, the Space Race would be abandoned in favor of developing the “economical” space transportation system. Los Alamos was still developing reactors, including the most powerful reactor ever run, but the tide was shifting towards smaller reactors to complete technology validation. Stacking small reactors, it was thought, would provide adequate thrust and cut down burn durations.

Even the space transportation system came under attack as tax revenue continued to shrink in the Nixon years. The original plan included nuclear orbital tugs, the chemical shuttle, and a space station. Ultimately, only the shuttle was funded, with the design of its cargo bay becoming a proxy battle over the future of nuclear propulsion. Small nuclear engines could be carried to orbit in the shuttle cargo bay, after which they would be attached to larger spacecraft and activated once astronauts had left the vicinity.


The Space Transportation System concept in 1970.

Source: Marshall Space Flight Center

Quite suddenly, though, all funding was terminated in 1973. Congressional funding was falling but still there, and researchers thought they were approaching flight test readiness. The change was ultimately a decision made by bureaucrats in the executive branch, which reprogrammed the funds without the consent of Congress or the President.

Believe it or not, this was technically a legal move. Several Senators were enraged by it, including Barry Goldwater—not exactly a friend of large, expensive federal programs. Within a few years, laws were introduced which required the Executive Branch to spend funds on the programs which Congress had allocated them for.

The defunding took the Soviets by surprise, to the point that they suspected it was a false-flag move to classify the work. Unfortunately, this does not appear to be the case. In fact, some of the officials involved in cancelling Rover were involved in the later Air Force Project Timberwind, which again attempted to develop nuclear propulsion. This too was cancelled after the end of the Cold War, without producing any real results.

All of this was really fascinating history, which I think should be discussed more widely in the spaceflight community. Nuclear propulsion, despite some extreme challenges, came very close to practicality. In the end, it was cancelled by politicians who failed to see the opportunities it provided rather than for the technological difficulties it faced.

It is quite arguable that Project Rover was well-worth the cost, and could have been justified on technology-development grounds alone. The program created entirely new industries, such as commercially-affordable cryogenics, and demonstrated all kinds of new material sciences. One would expect spaceflight advocates to mention this more often.

To the End of the Solar System does discuss the technical details, but is ultimately a political history. The style is somewhat confusing in this regard, routinely switching between Washington and Nevada—and not necessarily in chronological order. I would like to reread it to see if contextualization improves the narrative, but sadly it goes back to the school library tomorrow. Maybe one day I’ll buy a personal copy.

However, the appendices are worth reading. They provide a decent introduction to the major aspects of nuclear propulsion, without drowning the reader in technical minutiae. The discussion of radiation safety, for instance, was extremely informative and should allay many fears about the dangers of nuclear rocket testing. Dewar also dedicates a section to the Russian nuclear propulsion program. These are a good introduction to the subject, though hardly an expert make. I’ll be diving into dedicated nucleonics and advanced propulsion resources Soon™.

On the whole, To the End of the Solar System: The Story of the Nuclear Rocket is a rich resource for those studying the history of nuclear propulsion, whether for technical or non-technical reasons. Understanding the story of advanced propulsion is essential for those of us who wish to see humanity spread out into the Solar System, and James Dewar has written an excellent introduction. The book does not appear to be particularly common in print3, but if you get the chance to read it, you definitely should.

Image result for to the end of the solar system dewar

1Dewar mentions Project Prometheus to explain that it was too early in the program life-cycle to discuss. As it turns out, Project Prometheus went nowhere. In 2017, NASA issued new hardware contracts for exploring the manufacturing and testing requirements for making nuclear propulsion viable, but it is too early to say whether these will yield results, either.

2Bussard is better known for his later work on advanced propulsion, proposing a fusion ramjet fueled by the interstellar medium.

3I believe that it has had only two printings: initially from the University of Kentucky Press in 2004, and a second run from Apogee Books later in the decade. New hardbacks are hundreds of dollars on Amazon. There might be a PDF version floating around, but if there is, I haven’t come across it. Libraries are probably the best bet.


Beware Scientific Metaphors

I’m about a quarter finished with Isabel Paterson’s The God of the Machine, which I’m finally reading after several years of intending to. So far, it’s been both pleasurable and interesting. My main reservation, however, has been an extended metaphor which both illustrates the central idea and potentially undermines it.

Paterson develops a notion of energy to describe the synthesis of material resources, cultural virtue, and human capital which results in creativity and production. As metaphors go, this is not a bad one. That said, my engineering background gives me cause for concern. It isn’t clear that Paterson has a clear understanding of energy as a scientific concept, and her analogy may suffer for it. Complicating matters, she sometimes also phrases “energy” as if it were electricity, which is another can of worms in and of itself.

Mechanical energy behaves oddly enough for human purposes, being generally conserved between gravitational potential and kinetic energy, and dissipated through friction and heating. It emphatically does not spring ex-nihilo into cars and trains. Coal and oil have chemical potential energy, which is released as thermal energy, then converted into kinetic energy and thus motion to drive an internal combustion engine.

Electrical energy is even weirder. It’s been enough years since I finished my physics that I won’t attempt to explain the workings in detail. (My electronics class this spring bypassed scientific basis almost entirely.) Suffice to say that the analogy of water moving through a pipe is not adequate beyond the basics.

Atomic energy, the most potent source yet harnessed, does create energy, but at a cost. A nuclear generating station physically destroys a small part of a uranium atom, converting it via Einstein’s famous relation to useful energy. But more on that in later posts.

I won’t say that the “energy” metaphor is strictly-speaking wrong, because I haven’t done the work of dissecting it in detail. Paterson was a journalist and writer, but she was also self-educated, and therefore we cannot easily assess the scope and accuracy of her knowledge of such phenomena. But I don’t think it matters: even if the metaphor is faulty, the concept which it tries to communicate seems, on the face, quite plausible without grounding in the physical sciences.

I bring this up now, well before I’ve finished the book, because I’ve seen much worse analogies from writers with much less excuse to make them. The God of the Machine was published in 1943. Authors today have a cornucopia of factual knowledge at their fingertips and still screw it up. For instance, take this caption from my statics textbook:


Hibbeler, R. C., Engineering Mechanics: Statics & Dynamics, 14th ed., Pearson Prentice Hall, Hoboken, 2016.

There is no excuse for a tenured professor (or, more plausibly, his graduate students) to screw this up. The correct equation is on that very page and they couldn’t even be bothered to run the numbers and see that, no, you’re not significantly lighter in low Earth orbit. From my perspective, such a blatant error is unconscionable in the opening pages of a professional text.

Now that isn’t exactly a metaphor, but it illustrates the risks of discussing fields nominally close to your own which nevertheless you know very little about. Imagine the danger of using metaphors from totally different fields you’ve never formally studied.

So, I would advise writers to be sparing with scientific metaphors. If you can learn the science correctly, that’s great: you’ll construct metaphors that are both interesting and accurate. But as we’ve seen above, even PhDs make stupid mistakes. Err on the side of caution.

Book Review: Guns, Germs, and Steel

For many years, I did not expect to like this book.

Jared Diamond has something of a reputation for primitivism—arguing that hunter-gatherer societies are actually better off than our own. I found this position abhorrent as an Objectivist and wanted to hear nothing of it.

Then, around a year ago, educational YouTuber C.G.P. Grey made a pair of videos* summarizing certain aspects of Diamond’s book. The theory, as presented there, made a lot of sense and piqued my interest. A few months later I purchased a copy of Guns, Germs, and Steel from my local Half Price Books and eventually got around to reading it.

It turned out to be really good.

First of all, Diamond’s position on agricultural civilization is much more considered than many give him credit for. In the course of his anthropological research he’s spent many months living with modern hunter-gatherer societies, experiencing that sort of existence first-hand. Diamond says that his “own impression, from having divided my life between United States cities and New Guinea villages, is that the so-called blessing of civilization are mixed.” He goes on to discuss the various benefits that extremely low-tech societies realize: better family ties, richer social life, and considerably more free time.

His argument, then, is less that industrial civilization is necessarily bad, so much as that it comes with trade-offs. These trade-offs were far more salient for pre-Renaissance agricultural societies, for whom producing enough food to survive took nearly all available resources, and which were subsequently ravaged by war, disease, and famine on a level which pre-agricultural peoples almost never experienced.

But if the hunter-gatherer lifestyle is so great, why didn’t it stick around? The answer is simple enough: agricultural societies out-competed them. Farming allows a much larger population to subsist on the same land, and additionally allows for the development of professions—specialists not directly involved with food production. With a few exceptions, agricultural societies assimilated, displaced, outbred, or simply exterminated their less advanced neighbors.

So why did certain agricultural societies get an upper hand on the others? This is the real question of Diamond’s book.

His answer comes down to one word: geography. The orientation of the continents, the climate at various locations, and similar factors dictated what early humans had available to work with. The Americas and Africa, on their North-South axes, were at a significant disadvantage compared to Eurasia’s East-West axis. Plants and animals spread over a much wider area, increasing the odds that a human population would have the opportunity to domesticate them.

Thus the Americas and Africa ended up with a much slower diffusion of agriculture. (Australia had it even worse.) While industrial civilization might have developed there, it would have been much later. Eurasian colonization cut such trajectories short.

Diamond rejects the notion that certain peoples’ inherent superiority was the fundamental driver of historical progress. Over the course of millennia, cultural and genetic mutation would have been sufficient to make such factors irrelevant. Societies which disregard the advantages of any particular technology don’t tend to stick around very long. Thus human cultures tend to be near the full potential set by their geographic conditions.

We can observe this through natural experiments, the colonization of Polynesia in the last 2,000 years being a prime example. Austronesians, expanding out of Formosa, landed on nearly every Pacific island, and settled pretty much any scrap of land that can support human populations. These ranged from proto-empires in Hawaii and Fiji, to hunter-gatherers on the cold southern Chathams, which were conquered by New Zealand Maoris wielding European firearms in 1835. It also includes tiny Anuta, which despite a population of less than 200 realized an extremely high population density through advanced agriculture.

In a similar manner, Diamond explores the development of African, American Australian, Chinese, and European cultures in the context of geographic determinism. Of particular note is the impact of states on technology. China, a single political unit, abandoned oceanic exploration due to internal factionalism, and never expended the capital costs necessary to resume. Europe, alternatively, was never truly unified, and so never stopped exploration altogether.

Several chapters are devoted specifically to literacy, technology, and political theory. I think a few of my libertarian friends would find them quite interesting, particularly those concerned with what a stateless society might look like. Also noteworthy are the discussions of cultures which had and lost technology—writing being one example, Roman concrete being another. This obviously does not read as a conservative book, but the more intellectual breed of rightists will find something worth considering in Part Three.

Altogether, I found Diamond’s theory intelligent and well-argued. He does not pretend that it’s perfect. His epilogue is an exhortation for more serious study—history as a science, as he call it. Nearly thirty pages are devoted to suggested further readings. Find a coy, apply a light dose of skepticism, and enjoy.


*The first of these is Americapox: The Missing Plague, which discusses why European diseases were so devastating to Native Americans, but not vice versa. The second is Zebras vs Horses: Animal Domestication, which digs deeper into the causes at play. Disease is only one of the proximate factors Diamond discusses, and I’ve mostly chosen to omit it from my review because Grey explains far better than I could.