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An artist's conception of the Orion "basic" spacecraft, powered by nuclear pulse propulsion.

Nuclear pulse propulsion (or External Pulsed Plasma Propulsion, as it is termed in one recent NASA document) is a proposed method of spacecraft propulsion that uses nuclear explosions for thrust. It was first developed as Project Orion by ARPA, after a suggestion by Stanislaw Ulam in 1957. Newer designs using inertial confinement fusion have been the baseline for most post-Orion designs, including the famous Project Daedalus and the less well-known Project Longshot. Image File history File links Question_book-3. ... Image File history File links NASA-project-orion-artist. ... Image File history File links NASA-project-orion-artist. ... For other uses, see NASA (disambiguation). ... A remote camera captures a close-up view of a Space Shuttle Main Engine during a test firing at the John C. Stennis Space Center in Hancock County, Mississippi Spacecraft propulsion is any method used to change the velocity of spacecraft and artificial satellites. ... It has been suggested that Nuclear explosive be merged into this article or section. ... Thrust is a reaction force described quantitatively by Newtons Second and Third Laws. ... An artists conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion. ... The Defense Advanced Research Projects Agency (DARPA) is an agency of the United States Department of Defense responsible for the development of new technology for use by the military. ... Stanisław Ulam in the 1950s. ... Year 1957 (MCMLVII) was a common year starting on Tuesday (link displays the 1957 Gregorian calendar). ... Inertial confinement fusion using lasers rapidly progressed in the late 1970s and early 1980s from being able to deliver only a few joules of laser energy (per pulse) to a fusion target to being able to deliver tens of kilojoules to a target. ... An artists conception of the British Interplanetary Society design for Project Daedalus Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible interstellar unmanned spacecraft. ... Project Longshot is a design for an interstellar spaceship, an unmanned probe intended to fly to Alpha Centauri powered by nuclear pulse propulsion. ...

Project Orion

Main article: Project Orion (nuclear propulsion)

Project Orion was the first serious attempt to design a nuclear pulse rocket. The design effort was carried out at General Atomics in the late 1950s and early 1960s. The idea of Orion was to react small directional nuclear explosives against a large steel pusher plate attached to the spacecraft with shock absorbers. Efficient directional explosives maximized the momentum transfer, leading to specific impulses in the range of 6,000 seconds (about twelve times that of the Space Shuttle main engine). With refinements a theoretical maximum of 100,000 seconds (1 MN·s/kg) might be possible. Thrusts were in the millions of short tonnes, allowing spacecraft larger than 8×10⁶ short tonnes to be built with 1958 materials.^[1] An artists conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion. ... General Atomics is a nuclear physics and defense contractor headquartered in San Diego, California. ... Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... Space Shuttle Main Engine cluster The Space Shuttle Main Engines (SSMEs) are the three main engines on the Space Shuttle orbiter. ...

The reference design was to be constructed of steel using submarine-style construction with a crew of more than 200 and a vehicle takeoff weight of several thousand tonnes. This low-tech single-stage reference design would reach Mars and back in four weeks from the Earth's surface (compare to 12 months for NASA's current chemically-powered reference mission). The same craft could visit Saturn's moons in a seven-month mission (compare to chemically-powered missions of about nine years). It has been suggested that this article or section be merged with prototype. ...

A number of engineering problems were found and solved over the course of the project, notably related to crew shielding and pusher-plate lifetime. The system appeared to be entirely workable when the project was shut down in 1965, the main reason being given that the Partial Test Ban Treaty made it illegal (however, before the treaty, the U.S. and Soviet Union had already exploded at least nine nuclear bombs, including thermonuclear bombs, in "space," i.e., at altitudes over 100 km: see high altitude nuclear explosions). There were also ethical issues with launching such a vehicle within the Earth's magnetosphere. Calculations showed that the fallout from each takeoff would kill between 1 and 10 people (a claim that has been disputed: see radiation hormesis). The Treaty Banning poop, in Outer Space, and Under Water, often abbreviated as the Partial Test Ban Treaty (PTBT), Limited Test Ban Treaty (LTBT), or Nuclear Test Ban Treaty (NTBT), although the former also refers to the Comprehensive Test Ban Treaty (CTBT), is a treaty intended to obtain an agreement... Bluegill Triple Prime shot, 1962, altitude 31 miles High altitude nuclear explosions have historically been nuclear explosions which take place outside the Earths atmosphere. ... A magnetosphere is the region around an astronomical object in which phenomena are dominated or organized by its magnetic field. ... Radiation hormesis is the theory that low doses of ionizing radiation are beneficial. ...

One useful mission for this near-term technology would be to deflect an asteroid that could collide with the 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 and in the event of an imminent asteroid impact a few deaths from fallout would probably not be considered a major drawback. Also, an automated mission would eliminate the most problematic issues of the design: the shock absorbers.

Orion's technology is also one of very few known interstellar space drives that could be constructed with known technology.

Some authorities^{[attribution needed]} say that President Kennedy initiated the Apollo program to buy off the technical enthusiasts backing the Orion program^{[citation needed]}. The recent book by George Dyson says that one design proposal presented to Kennedy was a space-going nuclear battleship, which so offended him that he decided to end the program.

Soviet version

"In the early '60s, Sakharov, I remember, once invited us into his office and told us about this idea for an interstellar space ship that would be propelled through space by micro nuclear explosions. "

Former USSR Minister and current Russian Deputy Minister of Atomic Energy (MinAtom) Victor Mikhailov recalling discussing nuclear powered rockets with Andrei Sakharov ca. 1961.^[2][3][4] Andrei Sakharov, 1943 For the historian, see Andrey Nikolayevich Sakharov. ...

Project Daedalus

Main article: Project Daedalus

Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society (BIS) to design a plausible interstellar unmanned spacecraft that could reach a nearby star within one human scientist's working lifetime (set to be 50 years). A dozen scientists and engineers led by Alan Bond worked on the project. At the time fusion research appeared to be making great strides, and in particular, inertial confinement fusion (ICF) appeared to be adaptable as a rocket engine. An artists conception of the British Interplanetary Society design for Project Daedalus Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible interstellar unmanned spacecraft. ... The British Interplanetary Society (BIS) founded in 1933 by Mr. ... Alan Bond (born 1944) is Managing Director of Reaction Engines Ltd [1] and associated with Project Daedalus, Blue Streak missile, HOTOL and Skylon. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing sustainable fusion power. ... Inertial confinement fusion using lasers rapidly progressed in the late 1970s and early 1980s from being able to deliver only a few joules of laser energy (per pulse) to a fusion target to being able to deliver tens of kilojoules to a target. ...

ICF uses small pellets of fusion fuel, typically Li6D with a small deuterium/tritium "trigger" at the center. The pellets are thrown into a reaction chamber where they are hit on all sides by lasers or another form of beamed energy. The heat generated by the beams explosively compresses the pellet, to the point where fusion takes place. The result is a hot plasma, and a very small "explosion" compared to the minimum size bomb that can be created using fission. This article is about the chemical element. ... Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... Tritium (symbol T or ³H) is a radioactive isotope of hydrogen. ... For other uses, see Laser (disambiguation). ... For other uses, see Plasma. ...

For Daedalus, this process was run within a large electromagnet which formed the rocket engine. After the reaction, ignited by electron beams in this case, the magnet funnelled the hot gas to the rear for thrust. Some of the energy was diverted to run the ship's systems and engine. In order to make the system safe and energy efficient, Daedalus was to be powered by a Helium-3 fuel that would have had to be collected from Jupiter. An electromagnet is a type of magnet in which the magnetic field is produced by the flow of an electric current. ... Helium-3 is a non-radioactive and light isotope of helium. ... Atmospheric characteristics Atmospheric pressure 70 kPa Hydrogen ~86% Helium ~14% Methane 0. ...

As of 2006, designing an ICF system efficient enough for a Daedalus design is still considerably beyond current technical capabilities.

Medusa

Conceptual diagram of a Medusa propulsion spacecraft, showing: (A) the payload capsule, (B) the winch mechanism, (C) the main tether cable, (D) riser tethers, and (E) the parachute mechanism

Operating sequence of the Medusa propulsion system. This diagram shows the operating sequence of a Medusa propulsion spacecraft (1) Starting at moment of bomb / pulse unit firing, (2) As the bomb's explosion pulse reaches the parachute canopy, (3) Pushes the canopy, accelerating it away from the bomb explosion as the spacecraft plays out the main tether with the winch, braking as it extends, starting to accelerate the spacecraft, (4) And finally winches the tether back in.

The "Medusa" design is a type of nuclear pulse propulsion which has more in common with solar sails than with conventional rockets. It was proposed in the 1990s in another BIS project when it became clear that ICF did not appear to be able to run both the engine and the ship, as previously believed. Image File history File links Size of this preview: 800 × 279 pixel Image in higher resolution (1723 × 601 pixel, file size: 52 KB, MIME type: image/png) Conceptual drawing of a Medusa nuclear pulse propulsion type spacecraft, showing spacecraft capsule (A), tether winch (B), main tether (C), parachute canopy (E... Image File history File links Size of this preview: 800 × 279 pixel Image in higher resolution (1723 × 601 pixel, file size: 52 KB, MIME type: image/png) Conceptual drawing of a Medusa nuclear pulse propulsion type spacecraft, showing spacecraft capsule (A), tether winch (B), main tether (C), parachute canopy (E... Image File history File links Size of this preview: 518 × 599 pixel Image in higher resolution (714 × 826 pixel, file size: 41 KB, MIME type: image/png) Firing / operating sequence of a Medusa nuclear pulse propulsion spacecraft (see also Image:MedusaNuclearPropulsionConceptDrawing. ... Image File history File links Size of this preview: 518 × 599 pixel Image in higher resolution (714 × 826 pixel, file size: 41 KB, MIME type: image/png) Firing / operating sequence of a Medusa nuclear pulse propulsion spacecraft (see also Image:MedusaNuclearPropulsionConceptDrawing. ... Solar sails (also called light sails or photon sails, especially when they use light sources other than the Sun) are a proposed form of spacecraft propulsion using large membrane mirrors. ...

A Medusa spacecraft would deploy a large sail ahead of it, attached by cables, and then launch nuclear explosives forward to detonate between itself and its sail. The sail would be accelerated by the impulse, and the spacecraft would follow.

Medusa performs better than the classical Orion design because its "pusher plate" intercepts more of the bomb's blast, its shock-absorber stroke is much longer, and all its major structures are in tension and hence can be quite lightweight. It also scales down better. Medusa-type ships would be capable of a specific impulse between 50,000 and 100,000 seconds (500 to 1000 kN·s/kg). Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ...

The Jan 1993 and June 1994 issues of JBIS have articles on Medusa. (There is also a related paper in the Nov/Dec 2000 issue.)

Project Longshot

Main article: Project Longshot

Project Longshot was a NASA-sponsored research project carried out in conjunction with the US Naval Academy in the early 1990s. Longshot was in some ways a development of the basic Daedalus concept, in that it used magnetically-funneled ICF as a rocket. The key difference was that they felt that the reaction could not power both the rocket and the systems, and instead included a 300 kW conventional nuclear reactor for running the ship. The added weight of the reactor reduced performance somewhat, but even using LiD fuel it would be able to reach Alpha Centauri in 100 years. Project Longshot is a design for an interstellar spaceship, an unmanned probe intended to fly to Alpha Centauri powered by nuclear pulse propulsion. ... For other uses, see NASA (disambiguation). ... Teamwork: Fourth Class Midshipmen lock arms and use ropes made from uniform items as they brace themselves climbing the Herndon Monument The United States Naval Academy, or USNA, is an institution for the undergraduate education of officers of the United States Navy and the United States Marine Corps. ... Core of a small nuclear reactor used for research. ... Alpha Centauri (α Cen / α Centauri, also known as Rigil Kentaurus), is the brightest star system in the southern constellation of Centaurus. ...

Antimatter catalyzed nuclear pulse propulsion

Main article: antimatter catalyzed nuclear pulse propulsion

In the mid-1990s research at the Pennsylvania State University led to the concept of using antimatter to catalyze nuclear reactions. In short, antiprotons would react inside the nucleus of uranium, causing a release of energy that breaks the nucleus apart as in conventional nuclear reactions. Even a small number of such reactions can start the chain reaction that would otherwise require a much larger volume of fuel to sustain. Whereas the "normal" critical mass for plutonium is about 11.8 kilograms, with antimatter catalyzed reactions this could be well under one gram. Antimatter catalysed nuclear pulse propulsion is a variation of nuclear pulse propulsion based upon the injection of antimatter into a mass of nuclear fuel which normally would not be useful in propulsion. ... This article is about the state-related university. ... For other senses of this term, see antimatter (disambiguation). ... The antiproton (aka pbar) is the antiparticle of the proton. ... This article is about the chemical element. ... A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions. ... A sphere of plutonium surrounded by neutron-reflecting blocks of tungsten carbide. ... This article is about the radioactive element. ...

Several rocket designs using this reaction were proposed, ones using all-fission for interplanetary missions, and others using fission-fusion (effectively a very small version of Orion's bombs) for interstellar ones.

References

1. ^ General Dynamics Corp. (Jan 1964). Nuclear Pulse Vehicle Study Condensed Summary Report (General Dynamics Corp.). U.S. Department of Commerce National Technical Information Service.
2. ^ From an interview for Nuclear Dynamite, 1998.
3. ^ [1] Russian language details.
4. ^ Rough translation and more details at:[2]