Conceptual designs for antiproton space propulsion systems

Abstract

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.