A fusion rocket is a rocket that is driven by fusion power. The process of nuclear fusion is well understood and recent developments indicate this technology will be able to provide terrestial based power within 30 years (as of 2006). However, the proposed reactor vessels are prohibitively large and heavy making them unsuitable to use on spacecraft until at least next century. A smaller and lighter fusion reactor might be possible in the future when better methods have been devised to control magnetic confinement and prevent plasma instabilities. A Soyuz rocket, at Baikanur launch pad. ... Internal view of the JET tokamak superimposed with an image of a plasma taken with a visible spectrum video camera. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... A plasma lamp, illustrating some of the more complex phenomena of a plasma, including filamentation. ...

For space flight, the main advantage of fusion would be the very high specific impulse, the main disadvantage the (probable) large mass of the reactor. In addition, a fusion rocket may produce less radiation than a fission rocket, reducing the mass needed for shielding. The surest way of building a fusion rocket with current technology is to use hydrogen bombs as proposed in Project Orion. Specific impulse (usually abbreviated Isp) is a way to describe the efficiency of rocket and jet engines. ... For the generation of electrical power by fission, see Nuclear power plant An induced nuclear fission event. ... The mushroom cloud of the atomic bombing of Nagasaki, Japan, in 1945 lifted nuclear fallout some 18 km (60,000 feet) above the epicenter. ... An artists conception of the NASA reference design for the Project Orion spacecraft powered by nuclear propulsion. ...

Electricity generation vs. direct thrust

Many spacecraft propulsion methods such as ion thrusters require an input of electric power to run but are highly efficient. In some cases their maximum thrust is limited by the amount of power that can be generated (for example, a mass driver). An electric generator that ran on fusion power could be installed purely to drive such a ship. One disadvantage is that conventional electricity production requires a low-temperature energy sink, which is difficult (i.e. heavy) in a spacecraft. Direct conversion of the kinetic energy of the fusion products into electricity is in principle possible and would mitigate this problem. This article or section does not cite its references or sources. ... A mass driver for lunar launch (artists conception) A mass driver or electromagnetic catapult is a method of spacecraft propulsion that would use a linear motor to accelerate payloads up to high speeds. ...

An attractive possibility is to simply direct the exhaust of fusion product out the back of the rocket to provide thrust without the intermediate production of electricity. This would be easier with some confinement schemes (e.g. magnetic mirrors) than with others (e.g. tokamaks). It is also more attractive for "advanced fuels" (see aneutronic fusion). Only 20% of the power produced by the D-T reaction could be used this way; the other 80% is released in the form of neutrons which, because they cannot be directed by magnetic fields or solid walls, would be very difficult to use for thrust. A magnetic mirror is a magnetic field configuration where the field strength changes when moving along a field line. ... A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ... Base for aneutronic nuclear fusion. ...

Even if a self-sustaining fusion reaction cannot be produced, it might be possible to use fusion to boost the efficiency of another propulsion system, such as a VASIMR engine. VASIMR test bed The Variable specific impulse magnetoplasma rocket (VASIMR) is a hypothetical form of spacecraft propulsion that uses radio waves and magnetic fields to accelerate a propellant. ...

Confinement concept

To sustain a fusion reaction, the plasma must be confined. The most widely studied configuration for terrestrial fusion is the tokamak, a form of magnetic confinement fusion. Currently tokamaks weigh about the same as an oil tanker, so the thrust to weight ratio would seem unacceptable. A split image of the largest tokamak in the world, the JET, showing hot plasma in the right image during a shot. ... Magnetic confinement fusion is an approach to fusion energy that uses magnetic fields to confine the fusion fuel in the form of a plasma. ...

The main alternative to magnetic confinement is inertial confinement fusion, such as an Orion drive. A small pellet of fusion fuel (with a diameter of a couple of millimeters) would be ignited by an electron beam or a laser. To produce direct thrust, a magnetic field would form the pusher plate. In principle, the Helium-3-Deuterium reaction or an aneutronic fusion reaction could be used to maximize the energy in charged particles and to minimize radiation, but it is highly questionable whether it is technically feasible to use these reactions. Both the detailed design studies in the 1970s, the Orion drive and Project Daedalus, used inertial confinement. 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 Orion basic spacecraft, powered by nuclear pulse propulsion. ... A charged particle beam is a group of electrically charged particles that have approximately the same kinetic energy and move in approximately the same direction. ... Experiment with a laser (likely an argon type) (US Military) In physics, a laser is a device that emits light through a specific mechanism for which the term laser is an acronym: light amplification by stimulated emission of radiation. ... In physics, a magnetic field is an axial vector field that traces out solenoidal lines of force in and around closed electric circuits and bar magnets. ... Helium-3 is a non-radioactive and light isotope of helium. ... 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). ... Base for aneutronic nuclear fusion. ... An artists conception of a 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. ... 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. ...

A popular confinement concept for fusion rockets is inertial electrostatic confinement, such as in the Farnsworth-Hirsch Fusor. In an article[1] in the Analog Science Fiction and Fact publication, Tom Ligon (who also wrote several science fiction stories) suggested that the fusor might make the basis for a highly effective fusion rocket. It was also featured in this role in the science fiction novel The Wreck of the River of Stars, by Michael Flynn. However, there are difficulties with the concept, related to energy losses through bremsstrahlung radiation or maintaining a highly non-Maxwellian ion energy distribution or both, that appear to be fundamentally unsurmountable. Inertial electrostatic confinement (often abbreviated as IEC) is a concept for retaining a plasma using an electrostatic field. ... US3386883 - fusor -- June 4, 1968 The Farnsworth-Hirsch Fusor, or simply fusor, is an apparatus designed by Philo T. Farnsworth to create nuclear fusion. ... April 1997 issue of Analog. ... The Baháí Faith has appeared in fiction in multiple forms. ... Michael Flynn, (born 1947), sometimes published as Michael F. Flynn, worked full time as a statistician and wrote science fiction as a sideline for several years. ... (help· info), (from the German bremsen, to brake and Strahlung, radiation, thus, braking radiation), is electromagnetic radiation produced by the acceleration of a charged particle, such as an electron, when deflected by another charged particle, such as an atomic nucleus. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

A still more speculative concept is antimatter catalyzed nuclear pulse propulsion, which would use tiny quantities of antimatter to catalyze a fission and fusion reaction, allowing much smaller fusion explosions to be created. 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. ...

See also

• Spacecraft propulsion