will consist of He3 and deuteruim. The He3 will probably be manufactured on earth using particle accelerators, and then both components of the fuel will be launched in liquid form to orbit for processing into pelletized reactor fuel. The payload, like the fusion drive, will be launched fully-assembled, and have a simple plug-in interface to the rest of the system.
By the time that this mission will be flown, the experience gained through the assembly of Space Station, and the ongoing orbital operations which it is expected to support, will provide an adequate base of technology for personnel to assemble the probe. During assembly, systems checks will be run as each component is integrated into the spacecraft, to prevent failures which would necessitate disassembly of components assembled in orbit. Following assembly, a comprehensive system check-out will be made prior to ignition of the upper stages.
The fission reactor will be used to provide the initial power required to start the fusion reactor. Once the drive is ignited it will become self-sustaining and provide enough excess power to operate the systems in use during the transit. During this phase, fuel will be drawn from symmetrically located pairs of fuel tanks to avoid instability caused by non-homogeneous mass distribution. As each pair of tanks is emptied, they will be discarded. Tank volume has been calculated so that four of the ship's six tanks will have been jettisoned by the time it reaches the turn-
