To reduce the radiation hazard for manned missions to Mars and beyond, a high specific impulse-high thrust system is needed, with a nuclear bomb propulsion system the preferred candidate. The propulsion with small fission bombs is excluded because the critical mass requirement leads to extravagant small fission burn up rates. This leaves open the propulsion with non-fission ignited thermonuclear micro-explosions, with a compact fusion micro-explosion igniter (driver), and no large radiator. It should not depend on the rare He3 isotope, and only require a small amount of tritium. This excludes lasers for ignition. With multi-mega-ampere-gigavolt proton beams and a small amount of tritium, cylindrical deuterium targets can be ignited. The proton beams are generated by discharging the entire spacecraft as a magnetically insulated gigavolt capacitor. To avoid a large radiator, needed to remove the heat from the absorption of the fast neutrons in the spacecraft, the micro-explosion is surrounded by a thick layer of liquid hydrogen, stopping the neutrons and heating the hydrogen to a temperature of ~ 105 K, which as a fully ionized plasma can be repelled from the spacecraft by a magnetic mirror.