For a ship of exploration of our solar system, I chose the following.
It would be powered by a series of fusion reactors, sustained by an impulse drive system (no, its not just Star Trek). It uses a massive magnetic field with the poles lined up to the nose and rear of the ship, which would be of a linear configuration. It would magnetically attract polaraized space gases, which is mostly hydrogen, and pull them in the front of the magnetic field. Some of these gases become fusion materials to sustain the reactor. The rest is accellerated down a long tube, by magnetic forces. They are also bombarded by high-energy radiation, which is given off by the fusion reactors, and that can't be used for conventional power. This bombardment excites the gases, which are then joined by nucleonic helium (containing no electrons at all), which is the fused exhaust from the reactor, already excited. They are all then spit out the back at high speed, resulting in significant thrust. Furthermore, the magnegic field serves to protect the ship and crew from solar flares and other particle showers, that could be dangerous. It also gains energy from these solar storms, surfing on the shockwave somewhat.
Gravity would be maintained by a series of cyllinders near the front of the ship. The rotational systems would be maintained by magnetic repulsion to reduce drag. These cyllinders would be in decreasing diameter so they could all occupy the same space, each rotating at a different speeds, faster for those cyllinders closer to the center. Some of those closer to the center would contain hydroponics labs to both grow food, and to clean and re-oxigenate the air. The center of this, would be stationary and thus a 0-g section of the ship. It would also be heavily shielded to act as a refuge for the crew, should the magnetic field fail.
The main engine exhaust would be some distance back, but the reactors that power them are partway down the length of the ship, both far from the crew, and from the exhaust. There would also be a series of backup chemical engines both to suppement thrust, and to take over when the impulse engine is not suitable to use.
There would also be a series of docking ports at the rear of the crew compartment, where craft could be mounted, both for exploration of planets with or without atmospheres. All craft would be refuleable and fully reuseable. A ship of this type could travel to virtually any planet in the inner solar system in a matter of months.
