[RedDevil]

Originally Posted by redpoint5

Is a tube even necessary? Couldn't a maglev railgun accelerate at practically any rate, or is the tube the cheaper option?

I can't see a vacuum tube being feasible or practical.

Having the rocket use onboard propellant while being accelerated defeats the purpose of the accelerator; to reduce the required mass of onboard fuel. Rockets are already about 85% fuel, by weight. Of that fuel, something like 85% of it is used to accelerate the remaining fuel.

Providing ground based acceleration logarithmically reduces the amount of fuel required to take a vehicle to orbit or escape velocity.

Can the body really withstand sustained 10+ G acceleration rates if surrounded by water? The brain is encased in fluid, and yet people get concussions fairly easily.

Track it back to what stirred the discussion.
If you are to launch something with a rail gun it will produce a massive bang if you go supersonic; you cannot do it in vacuum.
Super heated steam however is much less dense than air because it has lower molecular weight and the molecules will be further apart.
A steam jet from a launch tube can reduce the friction and the initial bang in the atmosphere and even double as propellant.

The rocket comes in because it does 3 things at once: it produces thrust (though not enough to launch the capsule by itself), pressure pushing the capsule up and a jet of supersonic steam punching a channel through the air above the launch tube.

Would it be safe, or even possible, to fire a rocket inside a tube? I'm not sure... but it will produce more thrust than a rocket in open air.
Nuclear subs launch their ICMBs with compressed air, afaik, which only fire their rockets when well clear of the sub. But a tube bored in a volcano should be able to withstand a rocket blast. My concern would be whether the capsule itself can withstand it all.
But then the tube improves the performance of the rocket at the start - where its conventional efficiency is worst. It might even do away with the need of staged rockets.

As thread jacks go, this one is over the moon