A Discussion of a Mars Cycler Transit System
Here's the wikipedia stub and the Popular Mechanics article for the Buz Aldrin version.
The basic idea, if you're not familiar with it, is to have a large craft continuously moving at high velocity between the orbits of Earth and Mars without stopping. The orbit would be designed to make a pass by the planets at regular intervals. The premise is that it reduces the amount of material needed to be accelerated for each transit by limiting it to a small passenger craft that travels to or from the planet to the cycler and vice-versa.
I like the idea from that article, but I would want to alter and expand it. The current idea is near future with dainty craft, and wants to use aerobraking to slow a second class of cycler (Mars-Earth transit cycler) into orbit, board, and then boost for a slower, unrotating trip back to Earth. I wonder if it would be better to forgoe that second stage variation and just "waste" the fuel to accelerate up to a full-size/first-class cycler. This would be plausible once there is a fuel infrastructure on or near Mars.
The Aldrin idea would want to leave the cycler uninhabited and shut down as it waits for an Earth-Mars transit. However, I suspect it could be a useful platform for various astronomy activities, such as solar observing and as relays during conjunction (when one planet is eclipsed by the sun). The cycler-as-a-colony concept would mean it's is rather self-sufficient with recycling technologies, using solar energy, and only needing occasional inputs of stock materials (food, etc) after startup.
The basic reasoning is that an interpanetary craft has the same needs as a space colony (protection, arti-grav, recycling), except for thrust, and that once thrust is generated, the only difference is slowing it down into orbit around a planet or letting it sail past. If we want to send people, but not the entire vessel, to the planet, then you only need to decelerate a shuttlecraft or lander (to the surface or an orbiting station, perhaps another rotating colony). I think this would be a plausible step between dainty missions like Mars-For-Less and the desired but speculative big and fast interplanetary ships with lots of delta-v at their disposal. Since we don't know if or when we'll have those types of big and fast craft, or when they will become competitive once we have them, I think it's fair to examine this idea as valid starting in a couple decades and operative for several decades to a century or more using current technology.
There are limitations to the idea of a Mars cycler. It would only really be useful for perishable items like passengers and some small cargo. It would probably still be preferable (cheaper) to ship large amounts of bulk or large items via a slow boat. Each cycler has limited windows of use, making it desirable to have multiple cyclers running routes in order to have a semi-regular schedule. (I admit I don't have a complete understanding of the orbital mechanics to schedule one myself, but I've read there should be several, due to opposition occuring at different point in the orbit each time. Opposition would be the shortest transit, other trajectories going closer to the sun might also be plausible.)
Feel free to criticize or expand the concept.
Et tu BAUT? Quantum mutatus ab illo.