On Thu, Jul 23, 2020 at 4:27 PM <xxxxxx@gmail.com> wrote:
I was thinking of a massive electromag track launcher to fire you into orbit (maybe with some auxilliary propulsion to stabilize your orbit with minor tweaks). At least that might greatly reduce the amount of ship mass devoted to getting to orbit for the interface systems. That and a beanstalk to ship traffic up to the geosync stations. 
I was thinking of scaled up Ion drives for going planet to planet, but they may not scale well enough for that to be practical for any significant masses.

That works incredibly well on vacuum worlds. You can make the accelerator as long as you need to limit the g load on passengers, or use a short high-g accelerator for (non-fragile) cargo. You just let the pod leave the far end of the accelerator very nearly parallel to the ground on an elliptical or hyperbolic (escape) orbit. In the former case, you just need enough rocket power on the pod to circularize the orbit at apapsis, which doesn't take very much delta-v at all.

Building such launchers on Luna would be a great way to get bulk construction materials mined on Luna into lunar or terrestrial orbit. Using them to provide grain to Terra, as portrayed in Heinlein's _The Moon is a Harsh Mistress_, seems completely pointless, but it sure made for a great novel. :)

The whole idea falls apart if there's any significant atmosphere, unfortunately. Consider that to be in orbit, you are by definition travelling at a large fraction of escape velocity, and escape velocity is also the minimum speed of meteors entering the atmosphere. On Terra, these burn up at extremely high altitude, where the air is something like 0.1% surface pressure. Picture your pod emerging at a high fraction of minimum meteor velocity into sea-level air. Then stop picturing that, because it gets ugly fast.
 
I'm sort of assuming a) cold berths and b) some sort of fairly well developed anti-radiation shielding (foils, water barrier, maybe some kind of EM field all in conjunction or ?). That might make Ion okay, but it would still mean you'd have long times out and back ("Hey bob, how was your vacation on Mars?" "Well, Jim, the 4 weeks there was a really educational experience, but the 6 months each way in cold sleep meant I missed my anniversary...."). 

Oh, sure, if you can remove the biological constraints from space travel, e.g. through suspended animation and rad shielding as you propose, then you can use all kinds of super-efficient technologies like ion drives and solar sails. That's why our uncrewed probes require on the order of years to reach destinations in the inner solar system, and decades for the outer solar system; once we figured out how to build reliable robot explorers, we could send them on cheap-but-slow trajectories. Initially, this meant using a huge impulse from a chemical rocket over the first ~10 minutes of flight to send them on their way, followed by years of coasting and tiny trajectory tweaks, and sometimes a larger (but still tiny compared to the initial boost) burn at the destination to enter orbit or land. More recently, we've made practical use of ion drives for continuous low acceleration over months of flight, and we've just begun to experiment with solar sail technology.
 
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"What is now proved was once only imagined." - William Blake