It would be cheaper in every sense to turn something like a giant asteroid into a rotating habitat ship than achieve a constant 1g to even the closest systems. Realistically interstellar travel is not a thing that (biologically modern) humans will ever be suited for, robotic probes don't need thousands of kg of food and water to stay alive, don't need artificial gravity, air, or entertainment. The fact that the trip is inevitably 1-way won't bother probes and robots either.
You are right. One addendum: many humans would be bothered by one-way trips, but humanity is large, and in absolute numbers there are still plenty of volunteers for one-way trips to the planets and stars.
When talking about how efficient a given reaction mass engine, such as a rocket, can be the unit is specific impulse in seconds. That unit represents how long a given engine carrying a given propellant can maintain 1g acceleration.
For context, the most powerful chemical rockets peak around 450s-530s. A nuclear rocket of the sort we can build today would be more than twice that value, and super-efficient ion thrusters can have IspS in the tens of thousands of seconds.
But we're talking about an engine with a specific impulse measured in decades, and as far as anyone knows that means having catastrophic amounts of antimatter. I don't think plucky explorers on a one-way trip are going to have access to a small moon's worth of antimatter, and if they did, imagine how many more interesting things they could do with it than fly to nowhere?
Like power an entire planet for centuries, or use it as the energy budget for a megastructure project like a Dyson swarm.
We're talking about a truly incomprehensible amount of energy, not just to carry the rocket and its own fuel, but the tens of thousands of kg of water and food for even a modest compliment of people.
And how many in that group are actually fit to spend many years living that lifestyle without losing their mind and getting into deadly fights with one another?
And who's covering the great expense of building these generational colony ships and training their only inhabitants, only to have them zip away never to be heard from again? (With no benefit other than believing there's a slight chance we've succeeded in making our species multi-plantary)?
As humanity becomes more numerous and richer, the fraction of humanity you need that have such strange ideas and desire keeps shrinking.
(Btw, I share your intuition that the number of people willing to sign up for a one-way trip to the stars, or even just Mars, is fairly low. However, if you already look at people who are dedicated enough to become astronauts, I suspect the additional filter of asking for one-way-trip volunteers for a mission to the stars isn't all that severe. My purely speculative guess is that at least 10-20% of current astronauts would be willing to sign up.)
Yes. There's currently way more people who want to be astronauts, than people who can be astronauts. So you get some extreme selection effects; and those tend to bring out weird people.
I was really thinking of astronauts who have actually been to space; I wonder whether the experience disposes people to kookiness. I suspect that trainee/aspiring astronauts might suppress their kookiness.
Rotation wont really work unless the structure is gigantic (many miles in diameter) otherwise you will suffer from dizziness. Rotating spaceships like in many movies are probably making everyone on board sick.
This is true, it's why I suggest using a large asteroid for just that reason. Either way though, I promise you that altering a human's vestibular system to accommodate spin is a MUCH easier problem to solve than generating gigatons of antimatter fuel.
