The physics of antimatter induced fusion and thermonuclear explosions
The possibility of using antihydrogen for igniting inertia l confinement fusion pellets or triggering large-scale thermonuclear ex plosions is investigated. The number of antiproton annihilations required to start a thermonuclear burn wave in either DT or Li2DT is found to be about 10 21 /� 2 , where � is the compression factor of the fuel to be ignited. We conclude that the financial and energy investments needed to produce such amou nts of antiprotons would confine applications of antimatter trigger ed thermonuclear devices to the military domain.
On the utility of antiprotons as drivers for inertial confinement fusion
By contrast to the large mass, complexity and recirculating power of conventional drivers for inertial confinement fusion (ICF), antiproton annihilation offers a specific energy of 90MJ/{micro}g 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. We examine the physics underlying the use of antiprotons ({bar p}) to drive various classes of high-yield ICF targets by the methods of volumetric ignition, hotspot ignition and fast ignition. The useable fraction of annihilation deposition energy is determined for both {bar p}-driven ablative compression and {bar p}-driven fast ignition, in association with 0-D and 1-D target burn models. Thereby, we deduce scaling laws for the number of injected antiprotons required per capsule, together with timing and focal spot requirements. The kinetic energy of the injected antiproton beam required to penetrate to the desired annihilation point is always small relative to the deposited annihilation energy. We show that heavy metal seeding of the fuel and/or ablator is required to optimize local deposition of annihilation energy and determine that a minimum of {approx}3x10{sup 15} injected antiprotons will be required to achieve high yield (several hundred megajoules) inmore » any target configuration. Target gains - i.e., fusion yields divided by the available p - {bar p} annihilation energy from the injected antiprotons (1.88GeV/{bar p}) - range from {approx}3 for volumetric ignition targets to {approx}600 for fast ignition targets. 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 program for this application.« less
Conceptual designs for antiproton space propulsion systems
Conceptual designs for antimatter propulsion systems are reviewed, including 1) solid core liquid propellant rockets, 2) magnetically confined gaseous core rockets using both liquid and solid propellants, 3) plasma rockets, 4) pion rockets, which are driven directly by the mass annihilation products, and 5) ram-augmented rockets. Generally it is found that as the specific impulse of the propulsion system increases, the thrust decreases. Solid core rockets can have a specific impulse as high as 1000 s and thrust-to-engine mass ratios of 100 g. The performance here is limited by the temperature of the solid core. In a gas core rocket, a propellant gas is heated by the charged particles resulting from the annihilation. The charged annihilation products are contained by a magnetic bottle. The primary limitation here is heating of the chamber wall and nozzle. For this system, somewhat higher specific impulses can be achieved. Lining the chamber with a solid propellant or ablative material can increase the specific impulse somewhat, but the range of application is narrow. The chamber walls and nozzle can be removed by heating the propellant to ionization temperatures and then using magnetic, or electric, fields to contain and direct the plasma. With plasma rockets, specific impulses of 100,000 s or more could be achieved. Pion rockets can have a specific impulse of 20 x TO s but thrust-to-engine mass ratios of only 0.01 g. If the propulsion system can collect its propellant as it travels through a planetary atmosphere, or through the residual hydrogen in space, then extremely high specific impulses could be achieved.