Well, the g-force on the rotor in the deflection coils goes as the square root of the velocity (centripetal force). As the speeds rise, for any give acceleration in the deflection coils, the size of the ring needs to increase.

So the limit on the acceleration is the deflection coils, which in turn is limited by how intense the magnetic field can be made, which is limited to about 1-10 Tesla (ish) (~1 T is permanent magnets, ~10 T is superconducting magnets which may be expensive to run, or very heavily cooled electromagnets, but they're of little use here).

Net upshot is that a storage ring needs to be pretty big to get decent velocities/energy storage; km scale.

But you can demonstrate the basic technology at meter scale; but just not the high velocities.

Oops that should be square of the velocity, but the general argument is still correct.

It's a bit of a shame that the energy density isn't higher,  it doesn't even seem to compete with batteries, never mind gasoline at laptop sizes for example.

Still, for stationary use it might work; and as you scale the radius up it becomes much better I think.

This has probably all ready been discussed, but the next step after Launch Loops are orbital rings. This becomes a real possibility considering NASA plan's to establish a lunar base. 

See: http://en.wikipedia.org/wiki/Orbital_ring

bert

Yes, I think that is right, and it must be what I was originally thinking, before you convinced me otherwise :-) As you increase the size of the device leaving the rotor thickness unchanged, rotor mass goes up linearly. So does energy density, because a larger radius permits higher velocity using the same magnets. Thus, overall energy storage density increases indefinitely with size, something which cannot be matched by any other technology. Thus, there must be a critical size at which a storage ring becomes economical for storing power. If that size is manageable, research funds should be forthcoming. The  resurgence of interest in renewable energy makes a unique means of large-scale energy storage very attractive.

Andreas

Mmm. The problem is, that when something gets hit by something in orbit, essentially both the hitter and the hittee both explode, and generate a large shower of fragments that are both more or less in the original orbits, plus or minus some delta-v due to the explosion.

So the fragments of the projectile will tend to continue forward and, while many will reenter, many will not, and are likely to impact the spokes, or after the orbital planes have been perturbed by standard orbital mechanics, will impact the orbital ring from a different direction at very high speed causing a fresh shower.

Basically, you've got a runaway space debris situation from the orbital ring itself back onto itself, Kessler syndrome.

I think 100% of spacecraft in a decaying orbit are going to perform a near miss or worse with an orbital ring- as the apogee decays, it's certain to go through an altitude where the ring is, and because an orbital ring encircles the Earth, it's always going to be there. It seems to be worse than the Space Elevator in that regard.

And its worse the heavier the reentering object is- heavy objects have a higher ballistic coefficient, and hence lose less altitude per orbit, and hence are more likely to strike the ring.