In response to Russia's rather unorthodox suggestion to NASA — that perhaps it could use giant trampolines in absence of Russia's shuttle to get our astronauts up to the ISS — a more serious question arose: Could a ship really get into space without rocket fuel?
Physicist Jonathan McDowell, who was responsible for conducting the calculation that figured out just how a hypothetical space trampoline might work out (Spoiler: Not very well), joined the discussion to explore just what options were out there for a non-rocket spacecraft:
I've read before that giant slingshots might be one way to get people and objects into space without burning rocket fuel. Is there really anything to that idea?
You may be discussing the concept of the "Slingotron", which would use centrifugal force to work up enough energy to shoot something into orbit. The long story short version is that, yes, on paper that could work for materials delivery, but building up the required amounts of G-force (like, upwards of 60,000 Gs) would pulp any humans in the device. That said, it could theoretically be built using materials available today, and would possibly be a more cost-efficient way to get materials into orbit for a big build of some sort (spacecraft, station, whatever).
Here's a pretty good article from Space outlining it. And the wiki entry for "Non-rocket spacelaunch" is also worth a look. It gives an overview of other ideas, like mag-launches, skyhooks, mass drivers, even the classic Jules Verne big space gun.
Yes, this is a good list. I had forgotten about laser propulsion, which is another non rocket way of delivering the energy slowly enough not to puree you. In combination with a small deorbit rocket and heatshield reentry braking this could be a reasonable alternative ( you can't use the laser method to get back down, I think). As I said in the interview, the failure modes for skyhook approaches are nasty, and all the other methods are either variations on the rocket or involve giving you all the energy in the first second or so (which is hard to survive).