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To the End of the Solar System: The Story of the Nuclear Rocket

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Six million horsepower from a reactor the size of a 55 gallon drum. This was the promise of the ultimate in all-American 60's muscle - the nuclear thermal rocket engine. With it, you could send jumbo jet sized payloads to the Moon, or send a crew to Mars in 3 months.

James A. Dewar's exhaustively researched work (there are 91 pages of footnotes) shows both the technical and political sides of the 18 year effort to develop the nuclear rocket. Like the space program itself, the nuclear rocket program was a creature of the Washington political process.

While lacking the polish of a David McCullough, Dewar does a good job of introducing the cast of characters and their competing visions for America's technologic and social future.

Dewar's thesis is that the nuclear engine was feasible and would have revolutionized space travel, boosting mankind into a 2001 Space Odyssey. I found his viewpoint to be refreshing, especially in contrast to the dour visions of historians such as Richard Rhodes. He devotes Appendix D of the book to "safety and environmental aspects of testing."

Perhaps the most poignant vision one gets from reading the book is that of the turning of a page in American history. With the end of Apollo and the nuclear engine project in 1973 we go from an era of limitless promise, to an era of sharply limited outcomes.

To The End of the Solar System is an excellent primer on the nuclear rocket -- the history that might have been, and still waiting to be. It is a story even avid spaceflight fans may not have heard. Dewar presents a very readable account of the visionary engineers, project managers, and politicians who developed the first nuclear thermal rockets. The narrative covers the politics and engineering (with supplementary appendices) without being overwhelming. It explains why the nuclear rocket is superior to chemical engines, yet why the world failed to embrace it. The technology has lain dormant for decades, but is quietly making a revival in NASA's project Prometheus and elsewhere. Learn where it all started and where it's going; read To The End of the Solar System. It is well worth the price of admission.

Excellent book... a must read for anyone interested in space propulsion technology which needs a 'second look' to enable humans to bridge our Solar System in the future.

I have been a big fan of the Nuclear Thermal Rocket for many years. In 1966 my family drove by the Jackass Flats test site and I still have vivid memories of the AEC carpools passing us at 100mph on their private freeway from Las Vegas, hard hats stacked next to the back windows of their government-issue Chevys.

As I learned more about this program in recent years, the advantages of nuclear rockets seemed less clear to me. Is the 2x reduction in propellant weight really worth the big increase in cost and danger of a white-hot nuclear reactor? This book confirms my growing suspicions that NTR was and is a bad idea. The bare facts make it clear that this technology wasn't worth the costs even in the nuclear-friendly 1950s.

One often sees the claim that NERVA had a flight-ready design at the time of cancellation in 1971. The detailed descriptions of the many reactor tests in this book make it clear that this really wasn't so. Despite a huge amount of research, the high-temperature graphite/uranium fuel elements in these reactors were still subject to considerable cracking, corrosion and erosion. It was considered a great milestone when a test reactor lost less than 100lbs of bomb-grade uranium blown out the nozzle, mostly in the form of gas or microscopic inhalable particles.

This shouldn't have been a surprise to anyone. The great nuclear physicist Luis Alvarez had pointed out the fundamental physical limitations of the H2/U-235 rocket engine in an obscure but unclassified journal as early as 1947. And the Rover/NERVA project was consistently opposed by every Presidential Science Adviser and every NASA Administrator right up to its final cancellation in 1971. Why then was so much public money wasted on a project that almost all competent observers thought was unwise?

This is the strongest aspect of Dewar's book. He has reconstructed in great detail the political deals that kept Rover and NERVA alive. It's a fascinating window into a past age of Congressional politics -- an age when a few powerful committee chairmen ruled the Hill with an iron fist, deciding billion-dollar research programs at all-night poker parties lubricated with large amounts of hard liquor. None of these men had any kind of technical education at all, and their decisions seem to have largely been based on pork barrel politics. It's no accident that the strongest supporter of NERVA was Sen. Clinton Anderson of New Mexico, home of Los Alamos where most of the NERVA funding ended up.

But I also wanted to learn all the technical details of the program, and in this area Dewar has come up short. He obtained a vast number of formerly-classifed internal project documents, but the information from them is not conveyed to the reader in a digestible form. Dewar has tried to water down the subject to make it understandable for a non-technical audience. This is really difficult to do in a complex field like fission reactor design, and some of his analogies and interpretations are oversimplified and downright misleading. A few tables summarizing the different reactor designs and their test histories would have been nice.

Dewar also adopts the annoying practice of summarizing lenghty policy documents in his own words, without including the original text in a appendix. On p.248-249, he even includes what seems to be a totally imaginary conversation between some of the major players in NERVA -- hardly an acceptable practice for serious historians.

Even worse, there are a few telling technical errors that make me doubt that Dewar understands nuclear physics very well. In an attack on anti-nuclear activists on p.209-210, he confuses Pu-239 with Pu-238. These isotopes have very different properties and safety problems.

But the biggest problem with this book is that the author is a true believer. He repeats as gospel truth all the claims made by pro-NERVA politicians, while expressing nothing but scorn for the opinions of highly qualified experts like Alvarez, Herbert York, and Jim Webb. When he states facts, he usually can be trusted. But his analysis and opinions are highly biased and untrustworthy. I hope somebody writes a better book on this topic someday -- but I'm keeping this one until that happens.

This book is mesmerizing for anyone who is interested in either the U.S. political process or space exploration. The author spent his working life at DOE immersed in both politics and nuclear materials management, and much of Dewar's description of the way things worked in Congress back in the 1950's and 1960's is still the case today. While the author sometimes promotes his topic, he delineates his opinions carefully and gives equal space to opposing arguments. The book is copious with footnotes that are in and of themselves an excellent resource.

By the end of World War II, both rocket scientists and preeminent physicists like Leo Szilard and Stan Ulam had realized that although it looked impossibly difficult to develop, only nuclear energy could make manned space exploration beyond Earth orbit feasible. Nuclear reactors at that time were still huge and heavy, and nuclear weapons were only just barely feasible to carry on a large aircraft. Nonetheless, the physics of space travel was undeniable, then and now. Dewar mentions (and footnotes) a non-technical 1947 article by Luis Alvarez entitled, "There Is No Obvious or Simple Way in Which to Use Nuclear Energy For Spaceships" that made a long and objective assessment of the difficulties nuclear rockets entailed. At the time and up until Sputnik, rockets were a low priority for the United States. It was a young Dr. Robert Bussard who managed to convince a few people in the right places in 1953 that the difficulties could be overcome. Ultimately John von Neumann said that it should be examined as a precaution against the Russians developing one first. Mark Mills, assistant director of Livermore, came up with a way to achieve a workable design, and Herbert York, then-Livermore director (he later became director of DARPA), announced that he would form a division around it and staunchly supported nuclear thermal rockets for the remainder of his life. Norris Bradbury, director of Los Alamos, said that he would do the same, and a few years later the launch of Sputnik infused more cash into the project. The Cold War and the unrelenting support of several space supporters in Congress kept the project funded (along with Apollo) throughout the sixties, long enough to conquer Alvarez's list, right up until the Nixon administration defunded it along with much of the space program.

The technical reasons for developing nuclear rockets lie in gravity. Although we are able to send unmanned missions to other planets using chemical rockets, they must be highly expensive, multi-year affairs. Even though Apollo stretched the U.S. budget (approximately $150B in 2008 dollars), the Apollo missions were only feasible by using a multi-day gravitational slingshot process to help get our spacecraft to the Moon. A small 1960's-era nuclear thermal rocket can easily ascend to the Moon or Mars while keeping radiation exposure for astronauts to a minimum.

Today's rockets burn chemicals. Anybody who has ever built rockets, even just Estes rockets, has learned that almost all of a rocket's weight at launch is fuel. A large amount of effort is spent trying to leave just a few percent of the total weight of the rocket for payload, i.e. cargo.

Get more energy out of the fuel, and you're able to decrease the amount of fuel you carry. Now you can decrease the size of tanks and structure, and so the total weight of your rocket decreases, leading to a further decrease in fuel requirements. A small amount of weight saved means an extraordinary amount of fuel saved, and so the amount of energy in your fuel limits how far you can travel.

Weight and energy are issues for rocket engineers. Space radiation is a big issue for astronauts. For long missions very large amounts of shielding are necessary, not to mention more food and water. Radiation shielding tends to be made of materials like lead and concrete, so for example on a mission to Mars they very quickly begin to take up a significant portion of a rocket's cargo capacity. The mass drives up the fuel which drives up the mass again, etc. Because there are practical limits to the size of a space vehicle, the shielding requirement raises the mass and forces the mission duration to go up, which in turn requires more supplies and more shielding, which slows it down some more, and so on and so on.

Chemical rocket missions to the Moon the size of a Saturn V can take very little cargo and bring back almost none. Chemical rocket missions to anywhere else farther out stretch to years and multiple rockets. Huge manned multi-year space missions have thus far proven to be far beyond what any government has been willing to pay, because they require huge traveling space stations. They are also currently far beyond the reach of even the richest corporations. Even unmanned missions beyond low Earth orbit based on chemical rockets are either very expensive or incredibly slow. In contrast, manned nuclear-powered missions can be short and cheap.

No new chemicals are coming; the periodic table has been thoroughly explored since the early 1900's. If we want to send humans elsewhere in the solar system, chemical energy is insufficient, and only rockets powered by nuclear energy will do.

Nuclear rockets do much better than cutting rocket fuel requirements in half, as one of the other reviewers asserted. The ones invented in the 1960's made fast manned missions to anywhere in the solar system possible. This is not fanatic advocacy; it's simple physics. The research programs that succeeded in inventing them are one of the subjects of this book, and the incredible politics surrounding that research are another.

James Dewar wrote this book because by virtue of the fact that the programs were classified, very little has to date been published about them. "To The End Of The Solar System" is the ONLY existing detailed history of the U.S. nuclear rocket program. It reveals that by 1968 the difficult problems of building a nuclear thermal rocket had been solved. The programs were cancelled not because of technical difficulties or radiation problems, but because at that time manned space exploration was a huge budget issue, and the Republican Party saw correctly that nuclear rockets were necessary to exploration. The Democratic Party had made manned space exploration an integral part of their party platform, and by stopping manned exploration the Republican party was able stymie the Democrats. Politics doesn't always make sense, but that's what happened. What people didn't foresee was that the nuclear rocket and manned space exploration were so thoroughly hamstrung that they would be crippled for (at least) 40 years.

The research and footnotes in this book are exhaustive. One of the surprising things you'll learn is that the nuclear rocket program was not all pork-barrel politics, as Jeff Bell, an avowed opponent of manned space exploration, has asserted. Many of the program's staunchest Congressional supporters stood to gain nothing by supporting it; they simply argued that manned space exploration was a noble goal.

All rocket designers deal with white-hot temperatures, but the biggest problem for nuclear rocket designers was fuel rods that needed to be exposed to these temperatures. Surprisingly, after just over a decade of research in high-temperature materials and nuclear physics, the test program had advanced to the point where the engines were ready to launch. By 1968 the engines were running for hours at a time, a feat unmatched in engine tests before or since. The release of small amounts of radioactive materials in space (where they would be used) was not an issue, but by 1970 enough progress had been made by the Y-12 researchers that they felt that the engines might safely be used in the upper atmosphere with no releases whatsoever. Before the new fuel rods could be tested and before they could be flown, the program was ended.

It must be stressed again that the nuclear rocket program was ended not for technical reasons, but because many people were alarmed at the cost of the Apollo program. Ending nuclear rockets was the best way to make sure that the multi-decade expense of supporting Lunar and Mars colonies did not arrive.

James Dewar believes fervently in manned space exploration, but even if you don't there is no better or more exhaustively-referenced book on this fascinating slice of U.S. history than this one.

I'd love to read this book but can't justify shelling out so much money for either the hardback or Kindle versions. Who sets the prices for these books, I wonder?

This is an important book about a topic that is often unjustly overlooked. Nuclear rockets are significant because they represent the only proved approach to gaining significant improvements in the performance of rockets to be used for space propulsion. I hope to write about this and if I do, I will use this book as my principal reference.

Thomas A. Heppenheimer