Antimatter catalyzed nuclear pulse propulsion
Encyclopedia
Antimatter catalyzed 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. The anti-protons used to start the reaction are consumed, so it is a misnomer to refer to them as a catalyst.
Traditional nuclear pulse propulsion has the downside that the minimum size of the engine is defined by the minimum size of the nuclear bombs used to create thrust. With conventional technologies nuclear explosives can scale down to about 1/100 kiloton (10 tons, 42 GJ; W54
), but making them smaller seems difficult. Large nuclear explosive charges require a heavy structure for the spacecraft, and a very large (and heavy) pusher-plate assembly. Small nuclear explosives are believed to stop shrinking in overall size and required fissile nuclear materials at around 25 kilograms weight, so smaller pulse units are much more expensive per delivered unit energy, and much less mass efficient than larger ones.
By injecting a small amount of antimatter
into a subcritical mass of fuel (typically plutonium
or uranium
) fission
of the fuel can be forced. An anti-proton has a negative electric charge
just like an electron
, and can be captured in a similar way by a positively charged atomic nucleus
. The initial configuration, however, is not stable and radiates energy as gamma ray
s. As a consequence, the anti-proton moves closer and closer to the nucleus until they eventually touch, at which point the anti-proton and a proton
are both annihilated. This reaction releases a tremendous amount of energy, of which some is released as gamma rays and some is transferred as kinetic energy to the nucleus, causing it to explode. The resulting shower of neutron
s can cause the surrounding fuel to undergo rapid fission or even nuclear fusion
.
The lower limit of the device size is determined by anti-proton handling issues and fission reaction requirements, but the concept appears to be feasible using today's technology and infrastructure, unlike either the Orion-type system, which requires large numbers of nuclear explosive charges, or the various anti-matter drives, which require impossibly expensive amounts of antimatter.
Tuning of the performance to the mission is also possible. Rocket efficiency is strongly related to the mass of the working mass
used, which in this case is the nuclear fuel. The energy released by a given mass of fusion fuel is several times larger than that released by the same mass of a fission fuel. For missions requiring short periods of high thrust, such as manned interplanetary missions, pure microfission might be preferred because it reduces the number of fuel elements needed. For missions with longer periods of lower thrust, such as outer-planet probes, a combination of microfission and fusion might be preferred because it reduces the total fuel mass.
The concept was invented at Pennsylvania State University
before 1992. Since then, several groups have studied antimatter-catalyzed micro fission/fusion engines in the lab (sometimes antiproton as opposed to antimatter).
Work has been performed at Lawrence Livermore National Laboratory
on antiproton-initiated fusion. In contrast to the large mass, complexity and recirculating power of conventional drivers for inertial confinement fusion
(ICF), antiproton annihilation offers a specific energy of 90 MJ per µg and thus a unique form of energy packaging and delivery. In principle, antiproton drivers could provide a profound reduction in system mass for advanced space propulsion by ICF. Antiproton-driven ICF is a speculative concept, and the handling of antiprotons and their required injection precision—temporally and spatially—will present significant technical challenges. The storage and manipulation of low-energy antiprotons, particularly in the form of antihydrogen
, is a science in its infancy and a large scale-up of antiproton production over present supply methods would be required to embark on a serious R&D programme for such applications.
The current (2011) record for antimatter storage is just over 1000 seconds performed in the CERN
facility, a monumental leap from the millisecond timescales that previously were achievablehttp://www.nature.com/nphys/journal/v7/n7/full/nphys2025.html
Nuclear pulse propulsion
Nuclear pulse propulsion is a proposed method of spacecraft propulsion that uses nuclear explosions for thrust. It was first developed as Project Orion by DARPA, after a suggestion by Stanislaw Ulam in 1947...
based upon the injection of 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...
into a mass of nuclear fuel which normally would not be useful in propulsion. The anti-protons used to start the reaction are consumed, so it is a misnomer to refer to them as a catalyst.
Traditional nuclear pulse propulsion has the downside that the minimum size of the engine is defined by the minimum size of the nuclear bombs used to create thrust. With conventional technologies nuclear explosives can scale down to about 1/100 kiloton (10 tons, 42 GJ; W54
W54
The W54 was the smallest nuclear warhead deployed by the United States. It was a very compact implosion-type nuclear weapon design, designed for tactical use and had a very low yield for a nuclear weapon.- Development :...
), but making them smaller seems difficult. Large nuclear explosive charges require a heavy structure for the spacecraft, and a very large (and heavy) pusher-plate assembly. Small nuclear explosives are believed to stop shrinking in overall size and required fissile nuclear materials at around 25 kilograms weight, so smaller pulse units are much more expensive per delivered unit energy, and much less mass efficient than larger ones.
By injecting a small amount of 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...
into a subcritical mass of fuel (typically 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...
or 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...
) fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
of the fuel can be forced. An anti-proton has a negative electric charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
just like an electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
, and can be captured in a similar way by a positively charged atomic nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
. The initial configuration, however, is not stable and radiates energy as gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s. As a consequence, the anti-proton moves closer and closer to the nucleus until they eventually touch, at which point the anti-proton and a proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
are both annihilated. This reaction releases a tremendous amount of energy, of which some is released as gamma rays and some is transferred as kinetic energy to the nucleus, causing it to explode. The resulting shower of neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s can cause the surrounding fuel to undergo rapid fission or even nuclear 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...
.
The lower limit of the device size is determined by anti-proton handling issues and fission reaction requirements, but the concept appears to be feasible using today's technology and infrastructure, unlike either the Orion-type system, which requires large numbers of nuclear explosive charges, or the various anti-matter drives, which require impossibly expensive amounts of antimatter.
Tuning of the performance to the mission is also possible. Rocket efficiency is strongly related to the mass of the working mass
Working mass
Working mass is a mass against which a system operates in order to produce acceleration.In the case of a rocket, for example, the reaction mass is the fuel shot backwards to provide propulsion. All acceleration requires an exchange of momentum, which can be thought of as the "unit of movement"...
used, which in this case is the nuclear fuel. The energy released by a given mass of fusion fuel is several times larger than that released by the same mass of a fission fuel. For missions requiring short periods of high thrust, such as manned interplanetary missions, pure microfission might be preferred because it reduces the number of fuel elements needed. For missions with longer periods of lower thrust, such as outer-planet probes, a combination of microfission and fusion might be preferred because it reduces the total fuel mass.
The concept was invented at Pennsylvania State University
Pennsylvania 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...
before 1992. Since then, several groups have studied antimatter-catalyzed micro fission/fusion engines in the lab (sometimes antiproton as opposed to antimatter).
Work has been performed at Lawrence Livermore National Laboratory
Lawrence Livermore National Laboratory
The Lawrence Livermore National Laboratory , just outside Livermore, California, is a Federally Funded Research and Development Center founded by the University of California in 1952...
on antiproton-initiated fusion. In contrast to the large mass, complexity and recirculating power of conventional drivers for 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), antiproton annihilation offers a specific energy of 90 MJ per µg and thus a unique form of energy packaging and delivery. In principle, antiproton drivers could provide a profound reduction in system mass for advanced space propulsion by ICF. Antiproton-driven ICF is a speculative concept, and the handling of antiprotons and their required injection precision—temporally and spatially—will present significant technical challenges. The storage and manipulation of low-energy antiprotons, particularly in the form of antihydrogen
Antihydrogen
Antihydrogen is the antimatter counterpart of hydrogen. Whereas the common hydrogen atom is composed of an electron and proton, the antihydrogen atom is made up of a positron and antiproton...
, is a science in its infancy and a large scale-up of antiproton production over present supply methods would be required to embark on a serious R&D programme for such applications.
The current (2011) record for antimatter storage is just over 1000 seconds performed in the CERN
CERN
The European Organization for Nuclear Research , known as CERN , is an international organization whose purpose is to operate the world's largest particle physics laboratory, which is situated in the northwest suburbs of Geneva on the Franco–Swiss border...
facility, a monumental leap from the millisecond timescales that previously were achievablehttp://www.nature.com/nphys/journal/v7/n7/full/nphys2025.html
External links
- Antimatter Catalyzed Micro Fission/Fusion (ACMF)
- Antiproton-Catalyzed Microfission/Fusion Propulsion Systems For Exploration Of The Outer Solar System And Beyond (one of the early Penn-State articles)
- "On the Utility of Antiprotons as Drivers for Inertial Confinement Fusion" (Nuclear Fusion journal article of work performed at LLNL)