  Excluding speculations about future breakthrough discoveries in physics, it
is shown that with what is at present known, and also what is technically
feasible, manned space flight to the limits of the solar system and beyond deep
into the Oort cloud is quite well possible. Using deuterium as the rocket fuel
of choice, abundantly available on the comets of the Oort cloud, rockets driven
by deuterium fusion, can there be refueled. To obtain a high thrust with a high
specific impulse, favors the propulsion by deuterium micro-bombs, and it is
shown that the ignition of deuterium micro-bombs is possible by intense GeV
proton beams, generated in space by using the entire spacecraft as a
magnetically insulated billion volt capacitor. The cost to develop this kind of
propulsion system in space would be very high, but it can also be developed on
earth by a magnetically insulated Super Marx Generator. Since the ignition of
deuterium is theoretically possible with the Super Marx Generator, rather than
deuterium-tritium with a laser where 80% of the energy goes into neutrons,
would also mean a breakthrough in fusion research, and therefore would justify
the large development costs.
