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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 read this book a few months ago and I agree with the reviewer that this is an excellent book. However, it tends to concentrate a great deal more on the politics surrounding Project Orion than the science much to my chagrin. Much of the information surrounding Project Orion is still classified so I don't necessarily blame the author for this, but those intending on reading the book should qualify their expectations.
I did get a great appreciation for the sheer size and magnitude of truly difficult engineering problems and the organizations and minds assigned to solving them.
All in all, it's a quick and easy interesting read that engineers and NASA junkies will likely enjoy.
Another good book that bears on this subject is Robert Zubrin's Entering Space: Creating a Spacefaring Civilization. He discusses the atomic bomb drive as well as other postulated ideas for interstellar craft, such as solar wings and some trick with laser and mirrors (IIRC).
Even better, for slashdot folks, is that Zubrin takes this stuff seriously in a scientific sense. He discusses the energy needs and expected capabilities of the various craft, and in general covers a lot of "practical" ground. This is the same guy who is behind The Mars Society, which actively works to enable and encourage mannned missions to Mars.
Slashdot has covered Zubrin and Mars Society before; see this and that. He also has a mars-specific book titled The Case for Mars: The Plan to Settle the Red Planet and Why We Must. I recommend both his books to anyone who thinks we need to get off this rock.
They wern't meant to be exploded directly against the ship, but a 'safe' distance away. The blast/shock wave is what actually propels the ship. The pusher-plate absorbs the shock and transmits it to the rest of the ship like a giant shock-absorber.
You can find more info about advanced propulsion techniques (like the Orion-project) and other interesting space-science stuff at Warp Drive When?.
Government cannot make man richer, but it can make him poorer. - Ludwig von Mises
sPh
It's been done. Short story, in the 1950's they were still testing nuclear weapons. They put one at the bottom of a long mine shaft and put a heavy metal plate on top to partially contain the explosion. The plate was last seen moving at about six times escape velocity.
On the other hand, it probably vaporized before leaving the atmosphere, see Operation Plumbob for more information.
For more on Ted Taylor -- his work on fission bombs, his participation in Project Orion, his speculations on how small a nuclear bomb could topple the World Trade Center towers (decades ago), and his concerns about nuclear proliferation -- I strongly recommend John McPhee's The Curve of Binding Energy (BN). McPhee (BN) is an excellent writer, and this is one of his books I enjoyed the most.
Stupid job ads, weird spam, occasional insight at
http://search.npr.org/cf/cmn/segment_display.cfm?s egID=145345
The interview is great for conveying the commitment and enthusiasm Freeman felt for the Orion Project. They really believed that the ship would be build and flown to Mars last century. With NASA's new administrator Sean O'Keefe talking about alternative propulsion systems (including nuclear), who knows maybe Dyson's ideas will actually see the light of day.
yea i stole your sig- whats the big deal, it sucked anyway.
That's because it IS ludicrous, at least the "ascend into orbit" part. It has been a while since I read anything about Project Orion, but I'm pretty confident that this propulsion technique was intended for use only in space. The spacecraft would most likely have been assembled in orbit, or possibly launched from Earth by one mother of a big chemical rocket.
Remember the 'Dyson Sphere' episode of ST:TNG where Scotty had been trapped in a regenerative transporter cycle for 75 years in his ship, stuck on the sphere?
Well, Freeman Dyson is that Dyson.
See the Dyson Sphere FAQ for details.
Lucifer's Hammer is an offshoot/expansion/whatever of the asteroid impact scene in Footfall. According to N&P in a making-of article (source escapes me, but I think was an old Analog,) they were pitching the story outline for Footfall, and the editor wrote back, "Forget about alien invasion. Write about asteroid impact."
The rest, as they say, is history.
Life is like surrealism: if you have to have it explained to you, you can't afford it.
While a nuclear explosion is rather devastating, it doesn't totally vaporize everything. H bomb tests at Bikini atoll included Navy ships so we could see how they weathered the explosion. I think there's a picture with one cruiser lifted hundreds of feet up in the air with one of these tests.
For an Orion, you build a really thick plate (it will slowly wear away) with some ablative surface (carbon, oil?) and set off the nuke some distance from it. You don't capture all the force of the explosion but what you do bumps you along.
I drank what? -- Socrates
I feel compelled to plug Freeman Dyson's semi-autobiographical Disturbing the Universe:
http://www.amazon.com/exec/obidos/ASIN/0465016774/
I like the very earliest review. Mine's the one after.
Dyson's books are as interesting as science fiction, but without the cranky politics and cluelessness about the human condition that pervades much of the genre. Imagined Worlds is a sort of lite version of Disturbing the Universe; Weapons and Hope is a still-relevant book about arms control from the mid eighties.
The reason that a rocket engine has a conical 'bell' is to control the behavior of the exhaust gases. Specifically, the shape of the exhaust bell controls the efficiency of the gas flow, and prevents losses which could reduce thrust. All of the exploding happens inside the rocket, and it is the escaping gasses which the exhaust bell is designed to affect.
FYI, one of the main uses of explosion control is shaped charges, the kind that police special units use to get through walls/roofs/ceilings. A simple shaped charge can be made by placing two explosives in a 'V' shape, the resulting explosion will be pointed toward the opening in the 'V'. It's not magic, the explosion is very radial, but more heads toward the open end of the 'V' than any other direction. To get a charge which points most (nearly all?) of the explosion in one direction, put something strong and heavy around the explosive where you don't want damage. Example - a piece of angle iron (an 'L' shape of steel) with strips of C4 along the inside of the 'V' will shape the explosion and direct it toward the open end. Unfortunately, Newton's Third Law still applies (for every action there is an equal and opposite reaction), so the force of the explosion will want to move the angle iron. So you weight it down with sandbags. This is pretty much how LAPD started using shaped charges to enter buildings through the roof. A few pieces of angle iron with explosive in them, some sandbags, arrange on the roof, get behind something and BOOM. This was later refined - the shaped charges (iron pieces, wiring, & everything) were attached to a piece of particle board, placed on the roof, a few sandbags were dropped on top, and you could create yourself a nice entry hole for your SWAT team in a few seconds.
Caveat: I haven't experimented with shaped charges, I've just read about them.
sPh
A book by John A. McPhee, written in 1979, called The Curve Of Binding Energy gives an excellent account of this project, including an inverview with one of it's cheif designers. It's a fabulous book, and it's short, so you could read it in a night (a long night, but hey :>) Check it out at borders.
Wouldn't using the resulting hot gasses/radiation from a nuclear reactor provide a smoother, more efficient burn?
Smoother? Yes. More efficient? definitely not.
Specific impulse depends on exhaust velocity. Exhaust velocity depends on temperature. The maximum achievable temperature for a nuclear thermal rocket is limited by the reactor construction materials to a few thousand degrees. With an Orion rocket, even if it loses a significant percentage of of thrust sideways the temperature is still orders of magnitude higher.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
"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.)"
So the ship itself isn't really undergoing any ablation. I'm not sure if the term could be properly applied to a continuously resupplied coat of oil.
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