A fusion propulsion system for rapid deep space missions

A very promising, near-term propulsion system that could open up the solar system and beyond to human exploration is presented. It is called the Magnetically Insulated Inertial Confinement Fusion (MICF) Concept which combines the favorable aspects of both magnetic fusion and inertial fusion into one. Physical containment of the hot plasma is provided by a spherical metallic shell, such as tungsten, while its thermal energy is insulated from that shell by a strong, self-generated magnetic field. The fusion nuclear reactions in MICE can be triggered by a laser or a particle beam, and for mass considerations, we choose an antiproton beam that enters the target through a hole. Upon striking the inner surface of the pellet, the antiproton beam annihilates on the deuterium-tritium (DT) coated wall giving rise to the hot fusion plasma. In addition to thermally insulating the plasma, the magnetic field helps to contain the charged annihilation products, such as the pions, and allows them to deposit their energy in the plasma to heat it to thermonuclear temperatures. The mechanism for the generation of such a field revolves around the formation of density and temperature gradients in the ablation region. According to the generalized Ohm's law, these gradients, when at an angle with respect to one another, give rise to an electric field, which in turn gives rise to a time-varying magnetic field. The lifetime of the plasma in this device is dictated by the time it takes the shock wave to traverse the metal shell that surrounds the plasma once it is formed when the incident beam strikes the inner wall. Because of the thermal insulation provided by the magnetic field, this confinement time is relative long (similar to 10(-7) seconds) allowing the plasma to burn for a long time and to generate very large energy gains. As a propulsion system it is envisioned that MICF pellets will be dropped in a reaction chamber at a pre-determined rate, and zapped with the antiproton beam to initiate the fusion reactions. At the end of the fusion burn, these pellets (or the disassembled charged constituents) are guided by a magnetic nozzle and ejected from the chamber to produce the thrust. Preliminary analysis has shown that the MICF propulsion system is capable of producing specific impulses on the order of 10(6) seconds, and thrust of tens of hundreds of kilonewtons. Such capability makes not only the most distant planet in the solar system, but also the nearest star reachable in a human's lifetime. In fact it will be shown that a one- way mission to a 10,000 AU destination such as the Oort Cloud can readily be achieved in about 30 years.