My space launcher - tube - thingy

I was reading about launching nuclear waste into space, and the consequences of failure (i.e. rocket explodes at high altitude and poisons the entire biosphere). Someone suggested launching the payload into space via a railgun or some sort of mass driver. I've actually thought about how this would work. I considered a very unlikely science fiction-y idea. It goes something like this. 

You have a tube that wraps all of the way around the earth. There are magnets to accelerate a payload. The interior is kept at the same air pressure as low earth orbit.

At some point in the loop, you have a massive switching station that changes from the loop circuit to the launch tube. This tube would reach 400 miles or so into the upper reaches of the atmosphere. This way, you could accelerate the payload as fast as the supporting structure could handle the inertia generated without worrying about air resistance at ground level.

When you reach the desired velocity, you switch to the launch tube and zip the thing into space. There could be more than one launch tube as well. This would allow you to aim the payload to any spot the equator points. You could also throw another tube on the system running north-south to allow launching outside the plane of the solar system.

There would have to be very complicated air control systems to make sure that the pressure was constant throughout the ring and at different altitudes inside the launch tube(s). 

To power the magnets, you cover the entire tube with solar panels and run geothermal as a backup in case of bad weather and darkness.

As a bonus, when you're not chucking things into space, you could use it to transport cargo from one part of the planet to another very quickly.

There, problem solved! Engineers can now do the easy part and design it for me. Maybe I'll start a Kickstarter campaign to cover the construction cost.