[ScientificSorcerer (OP)]

Beam ships an ummite design principle.

There is something known as laser produced plasma, if you get a room sized 100giga watt (or greater) rapid pulsed laser and focus it down to a very thin beam then the thin yet powerful light beam will strip electrons from the air and create a plasma track in a straight line. The type of plasma is positive, because the electrons are stripped away from the air molecules. This track is more conductive then the surrounding air and any electricity will be attracted to it. Such as lightning, or man made high voltage plasma.

In essence you shoot this tiny yet ultra powerful laser beam straight up and blast some ultra high voltage and high amp electric power in that beam in-order to get a strong electro magnetic field around the beam. (Electro laser canon)

then you get a ship which is donut shaped (with a hole in the middle) in which the beam will go through, this ship will have a superconducting electro magnet on board (similar to an MRI) except charged to the max critical magnetic field. (Dependent on critical current) so that the ship gets around 8 teslas of magnetic power which requires no power consumption to maintain that level of magnetism.
Though it will need to remain super cold in-order to remain superconductive.
(Liquid helium fuel). This type of system would act like a "space bridge beam"
SBB for short.

In summery, you get a powerful electro laser canon to act as a rail gun (rail part)
And use a donut shaped superconductive magnet ship to act as the projectile.
It's that simple.

 

[alancalverd]

Define "simple". And then ask how you can make a plasma in space. Lasers have been used to make conductive holes in the atmosphere, but you run out of air after a couple of miles.

[CliffordK]

Depending on the distance from the sun, you should be able to use passive cooling in space.  For example, the JWST telescope is designed to operate at about 50K (-223° C), with passive heat shields (and locating in L2). 

A superconductor would be diamagnetic.  However, if you are making an electromagnet, it would require power, and more power for the more powerful magnet.  Consider MRI's all use power.

I'm not sure about a long distance magnetic field.  You may be able to make an electron beam (CRT monitors use a focused electron beam).  Perhaps a proton beam. 

Is your design essentially an electronic rail with a number of ships along it?  Otherwise, wouldn't it be preferable to capture the beam with something like a solar sail?

Your problem with multiple ships along the same beam would be that nothing is stationary, nor does it move in straight lines in space.  You may be able to focus the beam on a single ship, but not multiple ships.  And, hitting a small target, say 1 meter would be difficult for an object thousands of km away.