uld superconducting coils be mounted beneath a car to repel it against the force of gravity?Theoretically if it worked, the coils would act as permanent magnets so that relatively little energy would be needed to lift the car against the force of gravity.
The thing is, the only real benefit of maglev-tech is that it allows for a way to get rid of the friction which in turn allows to dramatically ramp up speed. And if you get rid of the surface friction (which normally doesn't hinder the car but moves it forward), but not the air friction (which is what really limits a car's speed), then you have achieved nothing. The whole point of maglev technology is that it works well in tunnels where the air is drained away, making it ideal for use in trains. But the concept doesn't really work in cars due to their unrestricted nature. What are you going to do, drain the whole athmosphere? There's also the additional problem of superconductivity not working when the temperature is over -270C. It doesn't work in room temperature. Still, it's entirely possible to build car-lifting magnets without superconductivity, just more expensive.
no. The earths magnetic field is not concentrated enough to overcome gravity, otherwise we could do it with regular electromagnets now. (maglev trains have to have two sets of magnets- they don't rely on the earths magnetic field) The magnetic field of earth is also variable so even if gravity was weak enough for it to work you would be in danger of either crashing into the ground or flying up into the air depending on where you were driving.
Using a matter anti-matter reaction engine might give you enough energy to accomplish this. Then again with the right type of roads it would merely require the energy used by maglev trains that are being built all over the world. The road could be rolled out like a carpet and then the vehicle could float easily over it if the road itself was metal or magnetic in some way. A fusion or nuclear engine would not be required. Probably an efficiently made turbine engine like what a typical helicopter uses, would be sufficient.
