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Could the same technology be used to help the lift off of Falcon9-sized space rockets from a deep vertical tunnel ?

• krastanov 7y ago
  On bodies without atmosphere, yes. It is a common thread in many futuristic exploration plans and scifi stories.
• ars 7y ago
  See here: https://en.wikipedia.org/wiki/Mass_driver https://en.wikipedia.org/wiki/Mass_driver You actually want horizontal velocity, not vertical. Getting "up" is easy (it's only a few miles), it's the horizontal speed that keeps you there. The only reason rockets launch straight up is to avoid the thick air as quickly as possible, then they turn and accelerate sideways the rest of the way.
  • logfromblammo 7y ago
    Or they do a gravity turn to round off the corner, largely in the same manner as that one math problem you probably did in school that involved finding the fastest path that includes running on the beach for some distance, then swimming at slower speed to a point in the water. Also, different rocket designs have different efficiencies at different outside pressures due to overexpansion or underexpansion of the exhaust plume. Kicking a rocket out of the atmosphere--or at least up to a lower pressure altitude--with a big gun first stage changes the requirements a bit for the second stage rocket engine. It's slightly more efficient. But the biggest advantage is that you aren't ever accelerating the fuel for the first stage along with the rest of the vehicle. The disadvantage is that you need a very long track if you don't want to reduce vehicle occupants to thin red paste with excessive acceleration. Also, you can evacuate the gun barrel and put one or more plasma windows at the end, so your initial acceleration doesn't have so much atmospheric drag.