Now, it may be a tad ignorant to say, because there's always a new innovation to be had...
But you're not getting anything off this rock without some form of propulsive force. And because your space elevator is generally inviable, the fact is that you need flight systems that can boost themselves into space at some level. The question then becomes, "how can one do this more efficiently?" Non-rocket spacelaunch as a thread title be damned. How do you make a better system?
Now, the tube launch isn't a bad concept, giving the flight vehicle that extra initial velocity, thus reducing a good fraction of the fuel wasted in the zero-speed phases of launch. BUT, the infrastructure would be difficult to maintain, and your lauch vehicles would be limited by the configuration of the launch system. In short, it's a short-term, novelty system with fairly limited application.
Actually, if you want to reduce the fuel consumption on the ground from a secondary catapult system, a steam catapult is interesting to at least consider. The technology is also very well vindicated. However, it should also be noted that the USN has been involved with the development of new electromagnetic launch systems, as seen
here.
"Lightcraft," very UFO-ey looking ship concepts, using intense heat from a ground source to generate propulsive thrust, are most interesting. They combine my new love of aerospike nozzle shapes with... well, nerdy engineering stuff that I just cant put to words. And the list goes on.
The fact is simple, efficient space flight cannot be achieved until you have a space flight system which can easily tranist from the ground to orbit. That said, I'm quite certain that spaceplanes will be the future for SSTO flight, while true space ships have yet to evolve for deep space flight. I suppose Apollo was the closest we've seen of the latter thus far, if the space stations are not considered.
