Nuclear pulse propulsion
Encyclopedia
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
document)
is a proposed method of spacecraft propulsion
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. There are many different methods. Each method has drawbacks and advantages, and spacecraft propulsion is an active area of research. However, most spacecraft today are propelled by forcing a gas from the...
that uses nuclear explosion
Nuclear explosion
A nuclear explosion occurs as a result of the rapid release of energy from an intentionally high-speed nuclear reaction. The driving reaction may be nuclear fission, nuclear fusion or a multistage cascading combination of the two, though to date all fusion based weapons have used a fission device...
s for thrust
Thrust
Thrust is a reaction force described quantitatively by Newton's second and third laws. When a system expels or accelerates mass in one direction the accelerated mass will cause a force of equal magnitude but opposite direction on that system....
. It was first developed as Project Orion
Project Orion (nuclear propulsion)
Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft...
by DARPA, after a suggestion by Stanislaw Ulam in 1947. Newer designs using inertial confinement fusion
Inertial confinement fusion
Inertial confinement fusion is a process where nuclear fusion reactions are initiated by heating and compressing a fuel target, typically in the form of a pellet that most often contains a mixture of deuterium and tritium....
have been the baseline for most post-Orion designs, including Project Daedalus
Project Daedalus
Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary Society to design a plausible unmanned interstellar spacecraft. Intended mainly as a scientific probe, the design criteria specified that the spacecraft had to use current or near-future technology and had to...
and Project Longshot
Project Longshot
Project Longshot was a conceptual design for an interstellar spacecraft, an unmanned probe intended to fly to Alpha Centauri powered by nuclear pulse propulsion. Developed by the US Naval Academy and NASA from 1987 to 1988, Longshot was designed to be built at Space Station Freedom, the precursor...
.
Project Orion
Project Orion was the first serious attempt to design a nuclear pulse rocket. The design effort was carried out at General AtomicsGeneral Atomics
General Atomics is a nuclear physics and defense contractor headquartered in San Diego, California. General Atomics’ research into fission and fusion matured into competencies in related technologies, allowing the company to expand into other fields of research...
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 impulse
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
s in the range of 6,000 seconds (about twelve times that of the Space Shuttle Main Engine
Space Shuttle main engine
The RS-25, otherwise known as the Space Shuttle Main Engine , is a reusable liquid-fuel rocket engine built by Pratt & Whitney Rocketdyne for the Space Shuttle, running on liquid hydrogen and oxygen. Each Space Shuttle was propelled by three SSMEs mated to one powerhead...
). With refinements a theoretical maximum of 100,000 seconds (1 MN·s/kg) might be possible. Thrusts were in the millions of tons
Tons
Tons can refer to:* Tons River, a major river in India* the plural of ton, a unit of mass, force, volume, energy or power* short ton, 2,000 pounds, used in the United States...
, allowing spacecraft larger than 8 × 106 tons
Tons
Tons can refer to:* Tons River, a major river in India* the plural of ton, a unit of mass, force, volume, energy or power* short ton, 2,000 pounds, used in the United States...
to be built with 1958 materials.
The reference design
Reference design
Reference design refers to a technical blueprint of a system that is intended for others to copy. It contains the essential elements of the system; however, third parties may enhance or modify the design as required....
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 tons
Tons
Tons can refer to:* Tons River, a major river in India* the plural of ton, a unit of mass, force, volume, energy or power* short ton, 2,000 pounds, used in the United States...
.
This low-tech single-stage reference design would reach Mars and back in four weeks from the Earth's surface (compared to 12 months for NASA's current chemically-powered reference mission). The same craft could visit Saturn's moons in a seven-month mission (compared to chemically-powered missions of about nine years).
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
Partial Test Ban Treaty
The treaty banning nuclear weapon tests in the atmosphere, in outer space and under water, often abbreviated as the Partial Test Ban Treaty , Limited Test Ban Treaty , or Nuclear Test Ban Treaty is a treaty prohibiting all test detonations of nuclear weapons...
made it illegal (however, before the treaty, the US 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 explosion
High altitude nuclear explosion
High-altitude nuclear explosions have historically been nuclear explosions which take place above altitudes of 30 km, still inside the Earth's atmosphere. Such explosions have been tests of nuclear weapons, used to determine the effects of the blast and radiation in the exoatmospheric...
s). There were also ethical issues with launching such a vehicle within the Earth's magnetosphere
Magnetosphere
A magnetosphere is formed when a stream of charged particles, such as the solar wind, interacts with and is deflected by the intrinsic magnetic field of a planet or similar body. Earth is surrounded by a magnetosphere, as are the other planets with intrinsic magnetic fields: Mercury, Jupiter,...
. Calculations showed that the fallout from each takeoff would kill between 1 and 10 people (a claim that has been disputed: see radiation hormesis
Radiation hormesis
Radiation hormesis is the hypothesis that low doses of ionizing radiation are beneficial, stimulating the activation of repair mechanisms that protect against disease, that are not activated in absence of ionizing radiation...
).
One useful mission for this near-term technology would be to deflect an asteroid that could collide with the earth, depicted dramatically in the 1998 film Deep Impact
Deep Impact (film)
Deep Impact is a 1998 science-fiction disaster-drama film released by Paramount Pictures and DreamWorks in the United States on May 8, 1998. The film was directed by Mimi Leder and stars Robert Duvall, Elijah Wood, Téa Leoni, and Morgan Freeman...
. 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 predicted deaths from fallout
Fallout
Fallout or nuclear fallout is the residual radiation hazard from a nuclear explosion.Fallout may also refer to:*Fallout , a 1997 post-apocalyptic computer role-playing game released by Interplay Entertainment...
would probably not be considered prohibitive. Also, an automated mission would eliminate the most problematic issues of the design: the shock absorbers.
Orion is one of very few interstellar space drives that could theoretically be constructed with available technology, as discussed in a 1968 paper, Interstellar Transport by Freeman Dyson
Freeman Dyson
Freeman John Dyson FRS is a British-born American theoretical physicist and mathematician, famous for his work in quantum field theory, solid-state physics, astronomy and nuclear engineering. Dyson is a member of the Board of Sponsors of the Bulletin of the Atomic Scientists...
.
Soviet version
Project Daedalus
Project Daedalus was a study conducted between 1973 and 1978 by the British Interplanetary SocietyBritish Interplanetary Society
The British Interplanetary Society founded in 1933 by Philip E. Cleator, is the oldest space advocacy organisation in the world whose aim is exclusively to support and promote astronautics and space exploration.-Structure:...
(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
Alan Bond (rocket developer)
Alan Bond is Managing Director of Reaction Engines Ltd and associated with Project Daedalus, Blue Streak missile, HOTOL, Reaction Engines Skylon and the Reaction Engines A2 hypersonic passenger aircraft.- Career :...
worked on the project. At the time fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
research appeared to be making great strides, and in particular, inertial confinement fusion
Inertial confinement fusion
Inertial confinement fusion is a process where nuclear fusion reactions are initiated by heating and compressing a fuel target, typically in the form of a pellet that most often contains a mixture of deuterium and tritium....
(ICF) appeared to be adaptable as a rocket engine.
ICF uses small pellets of fusion fuel, typically Li6
Lithium
Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...
D with a small deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
/tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...
"trigger" at the center. The pellets are thrown into a reaction chamber where they are hit on all sides by laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
s 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
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
, and a very small "explosion" compared to the minimum size bomb that would be required to instead create the necessary amount of fission.
For Daedalus, this process was run within a large electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
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
Helium-3
Helium-3 is a light, non-radioactive isotope of helium with two protons and one neutron. It is rare on Earth, and is sought for use in nuclear fusion research...
fuel that would have had to be collected from Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
.
As of 2009, designing an ICF system efficient enough for a Daedalus design is still considerably beyond current technical capabilities. However some designs are on the drawing board awaiting confirmation.
Medusa
Solar sail
Solar sails are a form of spacecraft propulsion using the radiation pressure of light from a star or laser to push enormous ultra-thin mirrors to high speeds....
s 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.
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
Specific impulse
Specific impulse is a way to describe the efficiency of rocket and jet engines. It represents the derivative of the impulse with respect to amount of propellant used, i.e., the thrust divided by the amount of propellant used per unit time. If the "amount" of propellant is given in terms of mass ,...
between 50,000 and 100,000 seconds (500 to 1000 kN·s/kg).
The January 1993 and June 1994 issues of the Journal of the British Interplanetary Society
Journal of the British Interplanetary Society
The Journal of the British Interplanetary Society is a technical scientific journal, first published in 1934. JBIS is concerned with space science and space technology...
(JBIS) have articles on Medusa. (There is also a related paper in the Nov/Dec 2000 issue.)
Project Longshot
Project Longshot was a NASANASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
-sponsored research project carried out in conjunction with the US Naval Academy in the late 1980s . 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
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
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
Alpha Centauri
Alpha Centauri is the brightest star in the southern constellation of Centaurus...
in 100 years, (approx. velocity of 13,411 km/s, or 30,000,000 mph)
Antimatter catalyzed nuclear pulse propulsion
In the mid-1990s research at the Pennsylvania State UniversityPennsylvania State University
The Pennsylvania State University, commonly referred to as Penn State or PSU, is a public research university with campuses and facilities throughout the state of Pennsylvania, United States. Founded in 1855, the university has a threefold mission of teaching, research, and public service...
led to the concept of using antimatter
Antimatter
In particle physics, antimatter is the extension of the concept of the antiparticle to matter, where antimatter is composed of antiparticles in the same way that normal matter is composed of particles...
to catalyze nuclear reactions. In short, antiproton
Antiproton
The antiproton is the antiparticle of the proton. Antiprotons are stable, but they are typically short-lived since any collision with a proton will cause both particles to be annihilated in a burst of energy....
s would react inside the nucleus of uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
, 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
Chain reaction
A chain reaction is a sequence of reactions where a reactive product or by-product causes additional reactions to take place. In a chain reaction, positive feedback leads to a self-amplifying chain of events....
that would otherwise require a much larger volume of fuel to sustain. Whereas the "normal" critical mass for plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...
is about 11.8 kilograms, with antimatter catalyzed reactions this could be well under one gram.
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.