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Project Orion: The True Story of the Atomic Spaceship
The chief advantage of an Orion-style spaceship can be explained in terms of specific impulse, which is the time during which a mass of fuel will produce enough mass x g thrust. Conventional chemical rockets, constrained by exhaust temperature, can produce specific impulses of about 430 seconds. Orion-style engines promised a specific impulse that was an order of magnitude higher than that--"2000 to 3000 seconds for first-generation designs, 4000 to 6000 for larger vehicles using existing bombs." The combination of long specific impulse and high thrust was unique to Orion, and would have allowed for the sustained high-acceleration maneuvers necessary for long-range manned space flight. And, like nuclear bombs in general, Orion scaled up more easily than it scaled down. The original Orion reference design massed 4,000 tons, and unlike the Apollo missions, which sent 600 lbs into space for every pound that came home, more than half of Orion's launch weight would have returned to Earth from a voyage to Saturn. Had it fulfilled its promises, Orion would have enabled manned space travel on a grand scale, with thousands of tons of payload and year-plus mission durations. It would have let us go into deep space in spaceships instead of mere disposable, unmanned spacecraft.
From 1958 to 1965, a team of physicists and engineers at General Atomic in California pursued the Orion dream. Project Orion tells their story ably. Dyson explores high-minded science and baroque bureaucracies in short, manageable, anecdote-loaded chapters. It's a terrifically easy read; with just freshman physics and a passing knowledge of 1950's America, I was able to follow along with no problems. The book begins by explaining the basics of Orion, the 1950's atomic establishment, the dot-com-like culture at General Atomic, the experiments that gave rise to the Orion idea, and the seed funding from ARPA. Dyson moves on to introduce us to some of Orion's chief characters, notably Stanislaw Ulam, who originally patented the atomic-pulse-drive idea, Ted Taylor, the Orion project leader and namer (he "just picked a name out of the sky," says the book) and Freeman Dyson, the celebrated scientist who was on board for the first two years -- and, who, not coincidentally, is George Dyson's father.
From there, it's on to the fun parts, beginning with the chapters detailing the engineering problems that Orion's designers faced. Most obviously, how do you design a pusher plate that won't shake itself apart or ablate under repeated impacts of nuclear plasma? (answer: with a thin coat of oil, reapplied between each atomic pulse.) How do you cushion the crew from the hundred-g shock of the pulse-unit explosions? (answer: with two-stage shock absorbers.) How do you shape the expansion of the propellant plasma so that you hit the pusher plate right? (answer: you take advantage of directed-energy weapons research to shape your atomic charges.) How do you eject your atomic charges from around the rim and orient them so that they explode correctly? (answer: you talk to Coca-Cola about bottling plant design.) And how do you cope with a pulse-unit misfire that sprays your pusher plate with jagged shrapnel instead of friendly plasma? (no answer given.)
Since GA's Orion program was a small shop that wasn't straightjacketed by job descriptions, the physicists were free to envision operational details and space missions for their baby. After concluding its engineering coverage, Project Orion looks at some of these missions. Freeman Dyson proposed a mission that would have landed on the moon, orbited Venus, Earth, and Mars, and then gone out to to Enceladus, Saturn's second-innermost satellite. The mission would have made clever use of tricks like planetary gravity boosts, in-atmosphere decelerations, and propellant harvesting to stretch its range. The senior Dyson was vexed by the problem of atomic contamination, though; even if it used the cleanest bombs available in the late fifties, an Orion launch would still introduce considerable amounts of toxic fission products into the Earth's magnetosphere. Dyson estimated that about ten people would die from atomic contamination for every Orion launch. This was about one percent of the estimated fatalities attributed to the atomic tests of the day. Instead of waiting for cleaner bombs to solve this problem, GA collaborated with friendly factions inside NASA--including rocket pioneer Wernher von Braun, who was an enthusiastic supporter of Orion--to discuss rocket-boosted Orion models. Proposals were made to either loft Orion into orbit wholesale or to boost it in pieces and conduct final assembly in orbit. Rocket-powered auxiliaries were also discussed; these would serve as landing craft and inter-Orion taxis.
In the end, of course, all of this work amounted to nothing. For various reasons -- nuclear test bans, lack of funding, and indifferent brass -- the Orion project was never permitted to conduct any of the nuclear test shots necessary to advance its work. The Orion staff made only a single successful test flight during the entire duration of the project, and this was conducted with 1m-diameter model powered by C4 charges. By 1959, Freeman Dyson had left the effort; he had seen that NASA wasn't going to budge away from Von Braun's giant rockets, and he knew that NASA was the only agency that would be able to support Orion. The project staggered on for four more years under Air Force funding, but the Air Force wasn't the right fit for Orion; no one could figure out a clear and present military use for all that lifting power. The USAF repeatedly approached NASA for money, but NASA was interested only in the conservatively incrementing known technologies, not in wholesale revolution. Orion was orphaned by 1965, its knowledge scattered through hundreds of classified documents and dozens of scientist's brains.
The book ends on a fascinating note, with modern-day retrospectives from various Orion staff. Some of them--including Ted Taylor--have renounced the idea of atomic weapons entirely. Some of them are convinced that Orion could never be made to work safely and reliably. Others believe that Orion is an idea whose time will come. NASA agrees with them, in some small measure; they're looking at Orion again as a space-exploration and asteroid-intercept technology. They're having a tough time finding details and data from the General Atomic project, though -- much of Orion's data is still classified. Dyson has had more success in hunting down those documents than NASA. When he contacted them in the course of his research, they begged him for copies!
I greatly enjoyed reading Project Orion. The only disappointment it held for me was its heavy reliance on Freeman Dyson's recollections, and the consequent weighting of the book towards Dyson's year of involvement. I suspect there's a lot of interesting detail missing from the latter six years of the project. That aside, Project Orion is an excellent high-level introduction to the characters, engineering, culture, and future of the Orion project, and an ideal jumpoff point to other readings about the atomic age.
You can purchase Project Orion: The True Story of the Atomic Spaceship from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.
I'm not a physicist, but I would think that the majority of the energy from the explosion would not propel the spaceship but would be emitted in perpendicular directions, escecially as the blast grew in size (let's not forget the sudden G forces involved here). Wouldn't using the resulting hot gasses/radiation from a nuclear reactor provide a smoother, more efficient burn?
If you are ever in Idaho, you should visit EBR-1, the world's first breeder reactor. It is decommissioned, cold, and open for tourists during the summer season. Outside, they have some prototype nuclear jet engines - devices that took in air, heated it with a fission reactor, and expelled it for thrust. Neat stuff - would have been nasty as hell had it ever gone into service, but neat none the less.
EBR-1 is about 4 hours drive from the west entrance of Yellowstone National Park, and about 45 minute from Craters of the Moon National Park, so there's plenty of other stuff to do in the area.
www.eFax.com are spammers
The shielding burns up, but at a predicted rate, and it lasts long enough to get the craft on the ground. Shuttle shielding is the opposite, it's a ceramic that simply "holds" the heat (vast simplification there, but well).
And it's ablation again with Orion. Sure, the explosions ablate part of the shielding, but it lasts long enough to get the craft where you want it to be.
And to answer your other question, the idea is like the engine of a car. If you can hear the individual pistons firing, then you've probably got a problem! But they do fire individually. Same thing with Orion (or similar) - the bombs are chucked out the back at a pretty rapid rate. At least in the designs I remember - I haven't read the book but I will based on the review. It sounds fascinating!
This is a design by Robert Zubrin for a rocket that produces a continous atomic blast using water with a high concentration of Uranium or Plutonium salts.
Nuke Your Way to the Stars
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
Dissolved uranium salts in water ejected by a magnetohydrodynamic drive (think linear accelerator for saltwater) with a neutron emitter to initiate fission at the egress point: that's the way to go. Any comments?
Cool hack if ever I have seen one! Build-your-own Mars Base in one of the most Mars-Like places on Earth, and do real research on how to operate said base when (not if) we get to Mars.
If you keep up with the web traffic on this project, NASA's position seems to be basically "Great work guys!" and "Can we send our best people?" to which request the Mars Society seems to graciously and intelligently accede.
Keep in mind that all controlled, sustained nuclear reactions we have engineered to date are fission reactions. An inefficiently converted but uncontrolled fusion reaction (aka Hydrogen bomb) will still give more "bang for the buck," literally and figuratively.
taken! (by Davidleeroth) Thanks Bingo Foo!
The air bursts (when the blast doesn't actually touch the ground) wouldn't have been that bad except for the initial EMP and radiation burst. Air bursts don't create fallout and are thus much cleaner then surface bursts (but I still wouldn't want to be around one).
Oh, really? Hiroshima was an air burst (around 2000 feet; no crater was created). Are you really saying there was no fallout at Hiroshima? I know there is less fallout than there is with ground bursts, but none?
This is one of the books you should read if you are interested in research, both with weapons and peaceful purposes, that was done with nuclear weapons. Theodore B. Taylor was one of the most interesting and ingeninous nuclear researchers ever, and had many ideas for using directed charge nuclear devices for everything from rockets to digging subways that would span the entire continent. He also discusses how easily nuclear devices can be made, and a lot of the current state-of-the-art in devices. A definite good read. More info about the book can be found on amazon here.
Way I see it there are three approaches to nuclear propulsion: 1) Orion -- putty-putty bang-bang, 2) NERVA -- high power density reactor which heats up hydrogen that squirts out a conventional rocket nozzle, and 3) VASIMIR (Variable specific impulse magnetic rocket) -- use the nuclear reactor for an electric power station and accelerate hydrogen or other gas with a magnetic rocket nozzle (there is also ion drive, but VASIMIR is popular these days because it offers the greatest thrust of all the electric schemes). The book, in talking the politics, indicated that NASA Huntsville though that Orion was pie-in-the-sky before doing something like NERVA first. VASIMIR is a more recent proposal and was not under consideration in that era. My understanding is that NERVA would be a replacement 3rd stage to a Saturn V -- that way the reactor would not be turned on until you got into space. One thing about NERVA is that its propellant is stores as liquid hydrogen, which is one of the bulkiest, least dense liquids around. The NERVA stage would have been huge, essentially the same diameter as the S-IC and S-II rocket stages below it, making the nuclear Saturn V one continuous cylinder until you got to the payload fairing. Given the weight of the reactor and given the bulk of the hydrogen tank, I am wondering if the 800-second specific impulse compared to the 430-second specific impulse of the regular Saturn S-IVB upper stage would have been a wash. Orion had a bulk problem too. If it was ground launched, if could have had a much bigger diameter pusher plate to capture more of the nuclear explosion and be more efficient (or perhaps less inefficient). Its efficiency came from the ultra-high temps of a nuclear blast compared to a sustained nuclear reactor and its inefficiency came from most of that efficiency being wasted apart from the little bit captured by the pusher plate, and the bigger the pusher plate the better. I thought they said a ground launch Orion could be in the 10000-second specific impulse range while the Orion launched as a third stage of a Saturn V was reduced to about 2000-second specific impulse because of the smaller pusher plate -- you start getting into the is it worth the bother range. I actually think that the Orion approach would be by far the easiest from the engineering standpoint, given how much work and testing went into bomb making. The only holdup is the idea of polluting even space let alone the Earth with that much fission fragments.
If we were to develop a ship that accelerated at 9.8 m*m for the first half of a trip, and then slowed at the same rate for the second half of a trip, would that be sufficient for artificial gravity?
Andy
Trusting software vendors is no smarter than trus
The idea is that you would have a tank of water with uranium salt in solution along with enough boron so the thing would go off at once. You piped this salt water into a reactor chamber where you somehow extracted the boron so that you would get a nuclear chain reaction inside the chamber and then the super heated salt water would squirt out the back.
As somewhat less crazy idea is that you would entrain uranium hexafluoride gas in a vortex in a reactor and pump hydrogen through it -- kind of a look-Ma-no-walls version of NERVA.
Just briefly I had the opportunity to meet George Dyson (a really nice down to earth guy). If the name sounds at all familiar, his sister is Ester Dyson (used to be chairperson of ICANN) and father is Freeman Dyson (a well known theoretical physicist). From what I've heard, George was always the odd one out in the family taking his own path. He used to live in a great looking tree house on the north end of Vancouver Island and then went on to research and build baidarkas (an Aleut Kayak).He has a great book on the kayaks called "Baidarka" which in the first half covers the history of the their development and Aleuts interaction with Russian traders and then moves on to cover the vessels themselves and his work.
He then went on to research and write a book on A.I. titled "Darwin Among the Machines: The Evolution of Global Intelligence". In addition to the original theories about using nuclear explosions to propel space ships, his father had the concept of building a huge structure around a star that people would live on the inside of and the star would provide the energy. You may remember this from a Star Trek Next Generation where they brought back Scotty, it was the Dyson Sphere. A final interesting tidbit is that George Dyson's grandfather Sir George Dyson was an English composer and founder of the National Federation of Music Societies.
Overall, it's an interesting family with some incredible minds in it. The BBC has a short piece on his AI book and on the left hand column is a real audio interview with George. There are also plenty of other links on google if you plug in his name.
is "The Starship and the Canoe" by Kenneth Brower. It's actually about Freeman Dyson (the "starship" refers to the Orion project) and George Dyson (who at the time was living in the Alaska wilderness). It's not really a techie book about specific impulses or engineering history, but a good read about these two very interesting people.