Project Orion (nuclear propulsion)
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[[Image:NASA-project-orion-artist.jpg|thumb|right|An artist's conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion.]]
'''Project Orion''' was the first engineering design study of a [[spacecraft]] powered by [[nuclear pulse propulsion]], an idea first proposed by [[Stanisław Ulam]] in 1947. The project, initiated in 1958, was led by [[Ted Taylor]] at [[General Atomics]] and physicist [[Freeman Dyson]], who at Taylor's request took a year away from Princeton's Institute for Advanced Study to work on the project. The first such think-tank of its kind since the [[Manhattan Project]], Project Orion is recalled by many of its team as representing the best years of their lives.{{Fact|date=October 2007}}
By using energetic nuclear power, Orion offered both high thrust and high [[specific impulse]] — the holy grail of spacecraft propulsion. It offered performance greater than the most advanced conventional or nuclear rocket engines now under study. Cheap interplanetary travel was the goal of the Orion Project. Its supporters felt that it had great potential for space travel, but it lost political approval because of concerns with fallout from its propulsion. The [[Partial Test Ban Treaty]] of 1963 is generally acknowledged to have ended the project.
==Nuclear power==
[[Stanisław Ulam]] realized that nuclear explosions could ''not yet'' be realistically contained in a combustion chamber. Such a project did briefly exist, named [[Helios (propulsion system)|Helios]], but its theoretical performance was so poor that it never got beyond the drawing board.
Instead, the Orion design would have worked by dropping [[Nuclear fission|fission]] or [[thermonuclear]] explosives out the rear of a vehicle, detonating them 200 feet (60 m) out, and catching the blast with a thick steel or aluminum pusher plate.
[[Image:ProjectOrionConfiguration.png|thumb|right|600px|The Orion Spacecraft - Key Components, from [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770085619_1977085619.pdf Nuclear Pulse Space Vehicle Study Vol III - Conceptual Vehicle Designs and Operational Systems, Fig 2.1, pp 4.]]]
Large multi-story high [[shock absorbers]] ([[pneumatic]] [[Spring (device)|spring]]s) were to have absorbed the impulse from the [[plasma wave]] as it hit the pusher plate, spreading the millisecond shock wave over several seconds and thus giving an acceptable ride. The long arm [[piston]]s proved one of the most difficult design features but many members of the team said that this seemed solvable. Low pressure gas bags were also proposed as a primary shock absorber. The two sets of shock absorption systems were tuned to different [[frequencies]] to avoid [[resonance]].
One aspect of the proposed vessel seems counter-intuitive today: because of the force involved in the thermonuclear detonations and the need to absorb the [[energy]] without harm, massive vessel designs were actually more efficient. Early designs had crew compartments and storage areas that were several stories tall, as opposed to contemporary [[chemical rocket]]s whose height was almost all multi-stage [[fuel]] tanks with relatively little payload.
[[Reaction mass]] for Orion would have been built into the bombs or dropped between 'pulses' to provide [[thrust]]. [[Polyethylene]] masses, garbage and sewage were all considered for use as reaction mass.
The smallest 4000 ton model planned for ground launch from [[Jackass Flats, Nevada]] had each blast add 30 mph (50 km/h) to the craft's [[velocity]]. A [[graphite]] based oil was to be sprayed on the pusher plate before each explosion to prevent [[ablation]] of the pusher plate. This sequence would be repeated thousands of times, like an atomic [[pogo stick]].
Orion's potential performance was stunning, at least compared to today's chemical or even other nuclear designs. [[Jerry Pournelle]], who is acquainted with the project and its ex-team leader [[Freeman Dyson]], has been quoted as saying that a single mission could have provided us with a large permanent moon base. {{Fact|date=October 2007}} <!-- "Quoted" = Where's the cite? --> Alternatively an Orion could reach Pluto and return to Earth inside of a year. Single stage to Mars and back also seemed to be possible. {{Fact|date=October 2007}}
==Background==
In the 1954 [[Operation Castle]] nuclear test series at [[Bikini Atoll]], a crucial experiment by [[Lew Allen]] proved that [[nuclear weapon design|nuclear explosives]] could be used for propulsion. Two [[graphite]]-covered [[steel]] spheres were suspended near the test article for the [[Castle Bravo]] shot. After the explosion, they were found intact some distance away, proving that engineered structures could survive a nuclear fireball.
==Performance==
The Orion nuclear pulse drive combines a very high exhaust velocity, from 20,000 to 30,000,000 m/s, with [[newton|meganewton]]s of thrust. Many spacecraft propulsion drives can achieve one of these or the other, but nuclear pulse rockets are the only existing technology that delivers both (see [[spacecraft propulsion]] for more speculative systems). [[Specific impulse]] measures how much thrust can be derived from a given mass of fuel, and is the standard figure of merit for rocketry.
Unmanned Orion-style nuclear pulse rockets can tolerate very large accelerations. A human-crewed Orion, however, must use damped springs behind the pusher plate to smooth the instantaneous acceleration to a level that humans can withstand–typically about 1–3 <math>g</math>.
The high performance depends on the high exhaust velocity, in order to maximize the rocket's force for a given mass of propellant. The velocity of the plasma debris is proportional to the square root of the change in the temperature (<math>T_c</math>) of the nuclear fireball. Since fireballs routinely achieve ten million degrees Celsius{{Fact|date=October 2007}} or more in less than a millisecond, they create very high velocities. However, a practical design must also limit the destructive radius of the fireball. The diameter of the nuclear fireball is proportional to the square root of the bomb's explosive yield.
The shape of the bomb's reaction mass is critical to efficiency. The original project designed bombs with a reaction mass made of [[tungsten]]. The bomb's geometry and materials focused the [[x-ray]]s and plasma from the core of nuclear explosive to hit the reaction mass. In effect each bomb would be a nuclear [[shaped charge]].
A bomb with a cylinder of reaction mass expands into a flat, disk-shaped wave of plasma when it explodes. A bomb with a disk-shaped reaction mass expands into a far more efficient cigar-shaped wave of plasma debris. The cigar shape focuses much of the plasma to impinge onto the pusher-plate.
A 10 [[kiloton]] of TNT equivalent atomic explosion will achieve a plasma debris velocity of about 100,000 m/s, and the destructive plasma fireball is only about 100 meters in diameter. A 1 megaton of TNT explosion will have a plasma debris velocity of about 10,000,000 m/s but the diameter of the plasma fireball will be about 1000 m.
The maximum effective specific impulse, <math>I_{sp}</math>, of an Orion nuclear pulse drive generally is equal to:
:<math>I_{sp} = \frac{C_0 \cdot V_e}{g_n}</math>
where <math>C_0</math> is the collimation factor (what fraction of the explosion plasma debris will actually hit the impulse absorber plate when a pulse unit explodes), <math>V_e</math> is the nuclear pulse unit plasma debris velocity, and <math>g_n</math> is the standard acceleration of gravity (9.81 m/s²; this factor is not necessary if <math>I_{sp}</math> is measured in N·s/kg or m/s). A collimation factor of nearly 0.5 can be achieved by matching the diameter of the pusher plate to the diameter of the nuclear fireball created by the explosion of a nuclear pulse unit.
==Sizes of Orion vehicles==
A 1959 report by General Atomics<ref name="GAMD-784">{{cite book| year=1959| publisher=General Atomics| title=Dimensional Study of Orion Type Spaceships| last=Dunne| coauthors=Dyson and Treshow| id=GAMD-784}}</ref> explored the parameters of three different sizes of [[hypothetical]] Orion spacecraft:
{| class="wikitable"
!
!"Satellite"<br/>Orion
!"Midrange"<br/>Orion
!"Super"<br/>Orion
|---
!Ship diameter
| 17–20 m || 40 m || 400 m
|---
!Ship mass
| 300 t || 1000–2000 t || 8,000,000 t
|---
!Number of bombs
| 540 || 1080 || 1080
|---
!Individual bomb mass
| 0.22 t || 0.37–0.75 t || 3.00 t
|}
The biggest design above is the "super" Orion design; at 8 million tons, it could easily be a city.<ref>{{cite book| title=Project Orion: The True Story of the Atomic Spaceship| first=George| last=Dyson| year=2002| id=ISBN 0-8050-7284-5}}</ref> In interviews, the designers contemplated the large ship as a possible [[interstellar ark]]. This extreme design could be built with materials and techniques that could be obtained in 1958 or were anticipated to be available shortly after. The practical upper limit is likely to be higher with modern materials.
Most of the three tons of each of the "super" Orion's propulsion units would be inert material such as [[polyethylene]], or [[boron]] salts, used to transmit the force of the propulsion unit's detonation to the Orion's pusher plate, and absorb neutrons to minimize fallout. One design proposed by [[Freeman Dyson]] for the "Super Orion" called for the pusher plate to be composed primarily of uranium or a [[Transuranium element|transuranic element]] so that upon reaching a nearby star system the plate could be converted to nuclear fuel. {{Fact|date=October 2007}}
==Applications==
The Orion nuclear pulse rocket design has extremely high performance. Orion nuclear pulse rockets using nuclear fission type pulse units were originally intended for use on interplanetary space flights.
The top cruise velocity that can be achieved by a thermonuclear Orion starship is about 8% to 10% of the [[speed of light]] (0.08–0.1c). An atomic (fission) Orion can achieve perhaps 3%–5% of the speed of light.{{Fact|date=March 2007}} A nuclear pulse drive starship powered by matter-[[antimatter]] pulse units would be theoretically capable of obtaining a velocity between 50% to 80% of the [[speed of light]]. {{Fact|date=December 2007}}
Missions that were designed for an Orion vehicle in the original project included single stage (i.e., directly from Earth's surface) to Mars and back, and a trip to one of the moons of Saturn.
One possible modern mission for this near-term technology would be to deflect an asteroid that could collide with Earth. The extremely high performance would permit even a late launch to succeed, and the vehicle could effectively transfer a large amount of kinetic energy to the asteroid by simple impact. Also, an automated mission would eliminate the most problematic issues of the design: the shock absorbers.
Nuclear fission pulse unit powered Orions could provide a fast, economical interplanetary transportation with useful human crewed payloads of gargantuan mass.
Orion's technology is also one of very few interstellar space drives that could be constructed with known technology. Orion is the ideal method of propelling a multi-generational starship such as an interstellar ark to the stars at velocities of up to 10% of the velocity of light.
Even at 0.1''c'', Orion thermonuclear starships will require a flight time of 44 years to reach [[Proxima Centauri]], the nearest star to the [[Sun]], not counting time needed to reach that speed. At 0.1''c'', an Orion starship would require 100 years to travel 10 light years. The late astronomer [[Carl Sagan]] suggested that this would be an excellent use for current stockpiles of nuclear weapons.
The first improved version of the Orion concept was designed by the [[British Interplanetary Society]] (B.I.S.) in the years 1973-1974. [[Project Daedalus]] was to be a robotic interstellar probe to [[Barnard's Star]] that would travel at 12% of the speed of light (0.12''c''). In 1989, an improved version of the original Daedalus design was created by the U.S. Navy in [[Project Longshot]].
From 1998 to the present, the nuclear engineering department at Pennsylvania State University has been developing two improved versions of the Daedalus design known as [[Project Ican]] and [[AIMStar(spacecraft)|Project Aimstar]].<ref>[http://www.engr.psu.edu/antimatter/documents.html Antimatter Space Propulsion at Penn State University (LEPS)<!-- Bot generated title -->]</ref>
==Economics==
The expense of the fissionable materials required was thought high, until the physicist [[Ted Taylor]] proved that with the right designs for explosives, the amount of fissionables used on launch was close to constant for every size of Orion from 2,000 tons to 8,000,000 tons. The larger bombs used more explosives to super-compress the fissionables, reducing fallout. The extra debris from the explosives also serves as additional propulsion mass.
[[Project Daedalus]] later proposed fusion explosives ([[deuterium]] or tritium pellets) detonated by electron beam inertial confinement. This is the same principle behind [[inertial confinement fusion]]. However, theoretically, it might be scaled down to far smaller explosions, and require small shock absorbers.
==Vehicle architecture==
{{Unreferencedsection|date=November 2007}}
From 1957 until 1964 this information was used to design a spacecraft propulsion system called "Orion" in which nuclear explosives would be thrown through a pusher-plate mounted on the bottom of a spacecraft and exploded underneath. The shock wave and radiation from the detonation would make an impact against the underside of the pusher plate, giving it a powerful "kick," and the pusher plate would be mounted on large two-stage [[shock absorber]]s which would transmit the acceleration to the rest of the spacecraft in a smooth manner.
Radiation shielding for the crews was thought to be a problem, but on ships with mass greater than a thousand tons, the structural bulk of the ship, its stores, and the mass of the bombs and propellent provides shielding for the crew from most of the explosives' radiation. Radiation shielding effectiveness increases exponentially with shield thickness (see [[gamma ray]] for a discussion of shielding).
At low altitudes, during take-off, the fallout would be highly radioactive, and there was a grave danger of fluidic shrapnel being reflected from the ground. The solution was to use a flat plate of conventional explosives spread over the pusher plate, and detonate these to lift the ship from the ground before going nuclear. This would lift the ship far enough into the air that a focused nuclear blast would avoid harming the ship.
A preliminary design for the explosives was produced. It used a fusion-boosted fission explosive. The explosive was wrapped in a [[beryllium oxide]] "channel filler", which was surrounded by a [[uranium]] radiation mirror. The mirror and channel filler were open ended, and in this open end a flat plate of [[tungsten]] propellant was placed. The whole thing was wrapped in a can so that it could be handled by machinery scaled-up from a soft-drink vending machine.
At 1 microsecond after ignition, the gamma bomb plasma and neutrons would heat the channel filler, and be somewhat contained by the uranium shell. At 2-3 microseconds, the channel filler would transmit some of the energy to the propellant, which would vaporize. The flat plate of propellant would form a cigar-shaped explosion aimed at the pusher plate.
The plasma would cool to 14,000 °C, as it traversed the 25 m distance to the pusher plate, and then reheat to 67,000 °C, as (at about 300 microseconds) it hit the pusher plate and recompressed. This temperature emits ultraviolet, which is poorly transmitted through most plasmas. This helps keep the pusher plate cool. The cigar shape and low density of the plasma reduces the shock to the pusher plate.
The pusher plate's thickness was to decrease by about a factor of 6 from the center to the edge, so that the net velocity of the inner and outer parts of the plate are the same, even though the momentum transferred by the plasma increases from the center outwards.{{Fact|date=November 2007}}<!-- not decreases? -->
At low altitudes where the surrounding air is dense, [[compton scattering|gamma scattering]] could potentially harm the crew. The plan to solve this was to have takeoff stations in inner rooms shielded by supplies and equipment. Such a radiation refuge is necessary anyway on long missions to survive [[solar flare]]s.
Stability was thought to be a problem due to random placement errors of the bombs, but it was later shown that over time the random errors would tend to cancel out.
A one-meter model using [[RDX]] (chemical explosives), called "putt-putt", flew a controlled flight for 23 seconds to a height of 56 meters at Point Loma.
The shock absorber was at first merely a ring-shaped airbag. However, if an explosion should fail, the 1000 ton pusher plate would tear away the airbag on the rebound. A two-stage, detuned shock absorber design proved more workable. On the reference design, the mechanical absorber was tuned to 1/2 the pulse frequency, and the air-bag absorber was tuned to 4.5 times the pulse frequency.
Another problem was finding a way to push the explosives past the pusher plate fast enough that they would explode 20 to 30 m beyond it, and do so every 1.1 seconds. The final reference design used a gas gun to shoot the devices through a hole in the pusher plate.
==Potential problems==
{{Unreferencedsection|date=October 2007}}
Exposure to repeated nuclear blasts raises the problem of ''ablation'' (erosion) of the pusher plate. However, calculations and experiments indicate that a steel pusher plate would ablate less than 1 mm if unprotected. If sprayed with an oil, it need not ablate at all (this was discovered by accident; a test plate had oily fingerprints on it, and the fingerprints suffered no ablation). The absorption spectra of [[carbon]] and [[hydrogen]] minimize heating. The design temperature of the shockwave, 67,000 °C, emits [[ultraviolet]]. Most materials and elements are opaque to ultraviolet, especially at the 340 MPa pressures the plate experiences. This prevents the plate from melting or ablating.
One issue that remained unresolved at the conclusion of the project was whether the turbulence created by the combination of the propellant and ablated pusher plate would dramatically increase the total ablation of the pusher plate. According to [[Freeman Dyson]], during the 1960s they would have had to actually perform a test with a real nuclear explosive to determine this; with modern simulation technology, this could be determined fairly accurately without such empirical investigation.
Another potential problem with the pusher plate is that of [[spall]]ing–shards of metal potentially flying off the top of the plate.
True engineering tests of the vehicle systems were said to be impossible because several thousand nuclear explosions could not be performed in any one place. However, experiments were designed to test pusher plates in nuclear fireballs. Long-term tests of pusher plates could occur in space. Several of these tests almost flew. The shock-absorber designs could be tested at full-scale on Earth using chemical explosives.
But the main unsolved problem for a launch from the surface of the Earth is [[nuclear fallout]]. Any explosions within the magnetosphere would carry fissionables back to earth unless the spaceship were launched from a polar region such as [[Antarctica]]. This would require enormous legal changes as the continent is presently an international wildlife preserve. Freeman Dyson, group leader on the project, estimated back in the '60s that with conventional [[nuclear weapons]], that each launch would cause on average between 0.1 and 1 fatal cancers from the fallout.<ref name="disturbing">Disturbing the Universe- Freeman Dyson</ref> The United States Government concurred and decided that because of the danger to human life and the danger to electronic systems on the ground (from [[electromagnetic pulse]]) to shelve the project.
Orion-style nuclear pulse rockets can be launched from above the [[magnetosphere]] so that charged ions of fallout in its exhaust plasma are not trapped by the Earth's magnetic field and are not returned to Earth.
The fallout for the entire launch of a 6000 [[short ton]] (5500 [[metric ton]]) Orion is only equal to a ten-[[megaton]] (40 [[petajoule]]) blast, assuming the use of pure fission weapon-type nuclear explosives.
With special designs of the nuclear explosive, [[Ted Taylor]] estimated that it could be reduced tenfold, or even to zero if a pure fusion explosive could be constructed. However, no pure fusion explosives have ever been successfully invented.<ref name="disturbing"/>
The vehicle and its test program would violate the [[Partial Test Ban Treaty]] of 1963 as currently written, which prohibited all nuclear detonations except those which were conducted underground, both as an attempt to slow the arms race and to limit the amount of radiation in the atmosphere caused by nuclear detonations. There was an effort by the US government to put an exception into the 1963 treaty to allow for the use of nuclear propulsion for spaceflight, but Soviet fears about military applications kept the exception out of the treaty.
One way around the restrictions of the treaty would be to use a form of the Daedalus fusion microexplosion rocket. Daedalus class systems use pellets of one gram or less ignited by particle or laser beams to produce very small fusion explosions with a maximum explosive yield of only 10–20 tons of TNT equivalent.
The launch of such an Orion nuclear bomb rocket from the ground or from [[low Earth orbit]] would generate an [[electromagnetic pulse]] that could cause significant damage to [[computer]]s and [[satellite]]s, as well as flooding the [[Van Allen radiation belt|van Allen belt]]s with high-energy radiation. This problem might be solved by launching from very remote areas, because the EMP footprint would be only a few hundred miles wide. The Earth is well-shielded from the Van Allen belts. In addition, a few relatively small space-based conductive [[tether propulsion|tether]]s could be deployed to quickly eject the energetic particles from the capture angles of the Van Allen belts.
Assembling a pulse drive spacecraft in orbit by more conventional means and only activating its main drive at a safer distance would be a less destructive approach. The [[space elevator]] hypothetically provides an excellent solution, but is currently impossible because existing materials such as [[carbon nanotubes]] do not have sufficient [[tensile strength]]. Existing chemical rocket designs are extremely inefficient (and expensive) when launching mass into orbit. Furthermore, it is unlikely that lifting the immense Orion into orbit in one piece would even be possible, unless multiple elevators or rockets were used in tandem. Adverse public reaction to any use of nuclear explosives is likely to remain a hindrance even if all practical and legal difficulties are overcome.
==Urban Legends==
{{main|Operation Plumbbob}}
According to an urban legend, a test similar to the test of a pusher plate apparently occurred as an accidental side effect of a nuclear containment test called "Pascal B" conducted on 27 August 1957.<ref>{{cite web| url=http://nuclearweaponarchive.org/Usa/Tests/Plumbob.html#PascalB| title=Operation Plumbbob| year=July 2003| accessdate=2006-07-31}}</ref> The test's experimental designer Dr. Brownlee performed a highly approximate calculation that suggested that the low-yield nuclear explosive would accelerate the massive (900 kg) steel capping plate to six times [[escape velocity]].<ref>{{cite web| url=http://nuclearweaponarchive.org/Usa/Tests/Brownlee.html| title=Learning to Contain Underground Nuclear Explosions| first=Robert R.| last=Brownlee| year=June 2002| accessdate=2006-07-31}}</ref> The plate was never found, and Dr. Brownlee believes that the plate never left the atmosphere (for example it could have been vaporized by compression heating of the atmosphere due to its high speed). The calculated velocity was sufficiently interesting that the crew trained a high-speed camera on the plate, which unfortunately only appeared in one frame, but this nevertheless gave a very high lower bound for the speed.
==Appearances in fiction==
{{main|List of stories featuring nuclear pulse propulsion}}
An early appearance of an Orion-style nuclear pulse propelled rocket in science fiction was in the science fiction novel ''[[Empire of the Atom]]'' written by [[A. E. Van Vogt]] in 1956. In this novel there is a post-atomic-war interplanetary empire called the Empire of Lyn that uses Orion-type nuclear rockets for interplanetary spaceflight. In the story the past atomic war was an interstellar war fought between humans and hostile aliens from another star somewhere between 800 and 8000 years before.
Early versions of ''[[2001: A Space Odyssey (novel)|2001: A Space Odyssey]]'' had a ship (''[[Discovery One]]'') using this drive. The final vehicle did not use this idea since [[Stanley Kubrick]] was fed up with nuclear bombs after making ''[[Dr. Strangelove or: How I Learned to Stop Worrying and Love the Bomb]]''.
In [[Jerry Pournelle]] and [[Larry Niven]]'s [[Hugo Award|Hugo]]-nominated novel ''[[Footfall]]'', an Orion vessel is constructed as a last-resort weapon against an alien invasion.
In the novel ''[[King David's Spaceship]]'', also by Pournelle, inhabitants of a planet that is to be readmitted as a colony world to the [[CoDominium|Empire]] plot to build the spaceship based on an Orion project concept in order to qualify their planet as a higher-developed, spacefaring, Class Two Imperial world.
The ''[[Star Trek: The Original Series|Star Trek:TOS]]'' episode "[[For the World is Hollow and I Have Touched the Sky]]" features a [[generation ship]], constructed out of a hollowed-out iron asteroid, propelled using "Orion class nuclear pulse engines" in which fission bombs were detonated in shafts. It appeared to have been traveling for about 10,000 years, and had traveled about 30 [[light years]] on its own power.
The 1998 film ''[[Deep Impact (film)|Deep Impact]]'' featured a spacecraft named ''Messiah'', which utilized the "Orion drive" and appears to be a variant of nuclear detonation propulsion. In the film, the drive is accredited to the Russians.
In the books ''[[Ilium (novel)|Ilium]]'' and ''[[Olympos (novel)|Olympos]]'' by [[Dan Simmons]] a space ship with Orion thrust is used to travel through the Solar System over the course of a week.
The book ''[[Orion Shall Rise]]'' by [[Poul Anderson]], part of his [[Maurai]] series of stories, featured a covert group within a resource-deprived, [[post-apocalyptic fiction|post-apocalyptic]] civilization resurrecting the Orion program to take humanity to the solar system and beyond.
==See also==
*[[Portal:Nuclear technology]]
==References==
<div class="references-small">
<references/>
*"Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" RTD-TDR-63-3006 (1963–1964); GA-4805 Vol. 1, Reference Vehicle Design Study, Vol. 2, Interaction Effects, Vol. 3, Pulse Systems, Vol. 4, Experimental Structural Response. (From the National Technical Information Service, U.S.A.)
*"Nuclear Pulse Propulsion (Project Orion) Technical Summary Report" [[1 July]] [[1963]]–[[30 June]] [[1964]], WL-TDR-64-93; GA-5386 Vol. 1, Summary Report, Vol. 2, Theoretical and Experimental Physics, Vol. 3, Engine Design, Analysis and Development Techniques, Vol. 4, Engineering Experimental Tests. (From the National Technical Information Service, U.S.A.)
*"Dynamic America; a history of General Dynamics Corporation and its predecessor companies", John Niven, Courtlandt Canby, and Vernon Welsh Designer, Erik Nitsche, 1960 [http://spacebombardment.blogspot.com/2005/10/dynamic-america.html Page Image]
* General Atomics, [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19650058729_1965058729.pdf ''Nuclear Pulse Space Vehicle Study, Volume I -- Summary''], September 19, 1964
* General Atomics, [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19770085619_1977085619.pdf ''Nuclear Pulse Space Vehicle Study, Volume III -- Conceptual Vehicle Designs And Operational Systems''], September 19, 1964
* General Atomics, [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660072847_1966072847.pdf ''Nuclear Pulse Space Vehicle Study, Volume IV -- Mission Velocity Requirements And System Comparisons''], February 28, 1966
* General Atomics, [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19660072846_1966072846.pdf ''Nuclear Pulse Space Vehicle Study, Volume IV -- Mission Velocity Requirements And System Comparisons (Supplement)''], February 28, 1966
* NASA, [http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19760065935_1976065935.pdf ''Nuclear Pulse Vehicle Study Condensed Summary Report (General Dynamics Corp)''], January 1964
* [http://www.alternatehistory.com/gateway/essays/OrionProblems.html Problems with the Orion project] a somewhat negative opinion on the project.
</div>
==External links==
{{commons|Project Orion|Project Orion (nuclear propulsion)}}
*[http://www.peoplesarchive.com/browse/movies/1216/ Freeman Dyson talking about Project Orion] on [[Peoples Archive]]
* [http://www.islandone.org/Propulsion/ProjectOrion.html Project Orion: Its Life, Death, and Possible Rebirth]
* [http://www.u.arizona.edu/~tuvas/ Electromagnetic Pulse Shockwaves as a result of Nuclear Pulse Propulsion]
* [http://www.mfbb.net/nuclearrockets-about12.html Nuclear Rocket Board: "Pulse Propulsion Document Library"]: Forum page w/links to original Orion docs
* [http://www.ted.com/talks/view/id/221 George Dyson talking about Project Orion] at [[TED (conference)|TED]]
* [http://www.bbc.co.uk/bbcfour/documentaries/features/mars-a-bomb.shtml To Mars by A-Bomb] at [[BBC Four]] Documentaries
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