Feasibility of coilgun system for sub-luminar interplanetary transport

My story is set within one solar system, which can be assumed to have a similar composition to that of our own: one Class G star, a handful of rocky inner planets and a handful of gas giants on the periphery. The backstory is that this was a colony from Earth that arrived on a generation ship many hundreds of years ago and has since lost contact with Earth; though this isn't pertinent to the question.

The setting calls for relatively hard-science, so normal Sci Fi tech like inertial dampeners, FTL, and artificial gravity are off the table. In a book series with a similar setting, interplanetary travel was achieved with "fusion drives" which allows for subluminar travel between planets in a few weeks or months. However, while fusion reactors are feasible within my story, a fusion drive still seems like a hand-wavey solution to the problem.

What I would like to use instead is a series of mega-structures in orbit around the various planetoids that act as large gauss cannons to "throw" vessels from planet to planet. Essentially, large interplanetary vessels would be designed to be loaded into the cannons and then fired as a projectile. The cannons themselves would of course need to be massive, on the order of 25km+ in length with massive power requirements to run the magnetic coils. When the ship is arriving on the other end, a similar mechanism captures it and uses the same rail gun assembly to slow it down.

Some issues I've identified with the tech and how they could be addressed:

• Failure condition: in the event that the receiving end of a transit could not capture the craft (for whatever reason) each vessel has enough fuel on board to perform one orbital injection burn as an emergency measure to prevent catastrophic failure.
• Human survival: the accelerations associated with launch and capture would be immense. I haven't done any math, but I'd guestimate on the order of 30+ Gs for a minute or so. Passengers would spend launch and capture unconscious in specialized "crash-couches" that would prevent death during acceleration.

What I'm looking for is an assessment of this method of transit for interplanetary travel compared to other semi-realistic methods; like fusion drives, ion propulsion, or giant chemical rockets.

To be clear, my narrative requires that this is the method of interplanetary travel I use, so I'm not looking for alternatives. What I want to know is how realistic this method is and/or if there are any tweaks I can make to improve it.

Some things to consider:

• Economic viability of maintaining the mega cannons vs. other methods of transport
• Safety of both vessels and launch/capture destinations using this method
• Practicality when considering method requires infrastructure at both ends of the transit path
• Whether orbital paths can be calculated with sufficient accuracy

posted over 6 years ago

enpaul‭

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