[The Red Zone]

Why don't I have to duck those pesky things while on the Albuquerque Tramway?

[SampleMan]

I had no idea Albuquerque was at 52,800,000 ft., or are you just tall? You did say miles.

Many low earth orbit sats are in fact at only a few hundred miles up.

My original point is that the exit velocity for a rail gun will be so high that atmospheric loading requirements will increase strength requirements. Starting the ascent at or above 10,000 ft, reduces that by half. There is also the engineering problem of burying that much structure. Much easier to build it above ground. Of course the vehicle would need to be in a contained tube, which is itself kept at less than normal atmospheric pressure. The less the better.

[JustDoItAlways]

We're still stuck using Chemistry.

Hyrdogen and Oxygen burn fast. Controlled-explosion gets you off the ground. Gliding, friction and parachutes get you back.

A little improvement in technology gets you a little better rocket ship. But you're still stuck using the Chemistry of Hydrogen and Oxygen (and the various solid fuel-based ways of storing the two elements to get a controlled explosion later.)

Nuclear doesn't sound like the next wave except for deep space exploration satellites. Plasma engines give you a good boost in deep space over a long period of time but it doesn't get you off the ground or the moon or Mars.

Until we get a new form of Energy (not based on Chemistry or dangerous Nuclear), we're stuck doing what we're doing now. Slightly better crafts as slight technology improvements come on stream.

New physics, anti-gravity, something else is needed to make the next step.