Feasibility of magnetic field

In our last post we found that we need to generate fields of the order of 1.5 x 10^-6 Tesla to move particles around the way we want to. Is this feasible? Let's consider a simple wire loop with a 1 mm² cross-section and in a 200 km radius circle. The volume of material in such a loop would be 1^-6m² x π x 400x10³ m = 1 m³. For unit density the mass is just a ton. For the best current superconductors that critical current density is 10³ to 10⁴ A/mm². Superconducitivity should be easy to achieve since we can run at just a few Kelvin. So let's say we can run 3000 A in the loop. This page let's us plug in the radius and current values and indicates that the resultant magnetic field at the center of the loop will be about 10^-8Tesla. So we're not quite there. If we use 150 coils we get our desired magnetic field at the cost of 150 tons of mass. This is a significant fraction of our mass budget, but not out of line with what we might expect for a major element of the propulsion system. It seems feasible to generate the magnetic fields we want without pushing current technologies too hard.

So we can generate the scale magnetic fields we need to collect the interstellar medium for fuel or reaction mass. Actually designing such a system is a very different thing. Of course we can only affect the ionized component of the medium. The neutral fraction will be unaffected by magnetic or electric fields. Our location in the Local Bubble is fortunate since it means that we can control most of the matter we will pass through.

One implication might be that travel through different regions on the Galaxy may require very different mechanisms with journey's through regions dominated by neutral matter using an entirely different approach than where the ISM is mostly ionized.