[stcredzero]

That could be a non-launch version of the Lofstrom Loop.

http://en.wikipedia.org/wiki/Launch_loop

Because it's not subject to the rocket equation, it would basically have the same effect on space access costs as a space elevator.

It is possible in principle for such a device to bring a vehicle up to hypersonic speeds, then regeneratively brake the same vehicle to a stop and recover a fraction of the energy.

[rwhitman]

I think this is much more likely to be what he's talking about than pneumatic tubes, as others have mentioned. Seems much more up his alley

[ableal]

Good reading there, but the part about the difficulties notes that it holds nuke-scale energies and states "Therefore for safety and astrodynamic reasons, launch loops are intended to be installed over an ocean near the equator, well away from habitation."

That would exclude the downtown-to-downtown feature.

[stcredzero]

the part about the difficulties notes that it holds nuke-scale energies

Nuke scale energies get dissipated in the atmosphere on a regular basis by thunderstorms. I suspect it may be possible to ensure that most of the mass burns up in the atmosphere and is dispersed.

That would exclude the downtown-to-downtown feature.

A rocketplane could "rendevous" with the electromagnetic loop at high altitude and then be accelerated and decelerated for the bulk of the cross-ocean trip, then land at an airport.

[maxerickson]

If one vehicle is leaving when one is arriving, you have a nice place to put all that energy.

I guess if the transit is efficient enough, you store energy by getting a bunch of mass moving around the loop.