Generation Ships--- Can we build one now?

tomBitonti · Feb 15, 2019

Umbran said:
That issue can arise on our generation ship if there's a problem that causes population loss, or on the new colony it may be viewed as necessary to increase reproduction rates. On the Earth in general, it requires a pretty major disaster do drop the population so much that we'd need to force reproduction.

I dunno ... see, for example Italy and Japan, which are losing population because of very low birth rates.

Thx!
TomB

tomBitonti · Feb 15, 2019

dragoner said:
It's not just fusion power is hard, because it isn't (and the state where I live is 3/4's coal powered for electrical generation)*. No, what is hard is doing the math and seeing that you would need all the combined power output of the entire Earth for the next ~14 years or so to launch it from out of our solar system. I have no doubt we'll come up with better propulsion systems, such as eventually fusion rockets, anti-matter catalyzed fusion rockets, or even a super VASIMR/MPD type combined with a field that reduces the interaction between mass and inertia on the quantum level, something wild. Nevertheless, that day isn't today.

*Fusion works, we just aren't getting enough energy back out for what goes in. However, fusion reactors to be efficient have to be much larger (football field sized), is what I have read.

Using fusion for propulsion is a bit different than using it to generate electrical power. I don’t know that our failure to generate power means we can’t make a fusion drive. (There is a lot of solid research on this ... do a search on interstellar rocket motor.)

Thx!
TomB

Umbran · Feb 15, 2019

tomBitonti said:
I dunno ... see, for example Italy and Japan, which are losing population because of very low birth rates.

Yes, they are losing population, but not drastically. In the past decade, Japan has dropped from 127.8 million, to 126.8 million. That's less than one percent (it is 0.7% or so of the population, over an entire decade). In the long run, yes, you'd want to correct for it, but it isn't a situation to call for *forcing* people to have babies.

Umbran · Feb 15, 2019

tomBitonti said:
Using fusion for propulsion is a bit different than using it to generate electrical power. I don’t know that our failure to generate power means we can’t make a fusion drive. (There is a lot of solid research on this ... do a search on interstellar rocket motor.)

At the low-tech end of the scale - you can make a drive with bombs. Build your ship on a big metal plate, with shock absorbers. Throw bombs behind the plate, and let the blast push you along. https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

dragoner · Feb 15, 2019

Shasarak said:
Is there any way we can increase the amount of energy that we can use on Earth? I mean we are burning trees and dinosaur juice now and on the other hand the Sun releases a million times more energy in 1 second then the earth uses in 1 year.

Eventually, except in the confines of the question, not today, that is the simplest answer. Sure, we will increase power generation, and if we build a smart grid we won't lose 40% of generated power due to Ohm's Law, from pumping power into a hundred year old grid with hundred year old power plants.

It's really baby steps to get into space though, the knowing comes from doing, right now, if we built an interplanetary vehicle, it would be very primitive in design, like one of those Duryea cars in comparison to modern ones. That's before any consideration of an interstellar vehicle. Plus the fundamental truth is that if we could create a vehicle where people could live on some thousands of year journey, we could build an O'Neill Cylinder at a Lagrange Point and live there, not needing to make the long journey.

tomBitonti said:
Using fusion for propulsion is a bit different than using it to generate electrical power. I don’t know that our failure to generate power means we can’t make a fusion drive. (There is a lot of solid research on this ... do a search on interstellar rocket motor.)

Thx!
TomB

Rockets are engines: https://en.wikipedia.org/wiki/Rocket_engine I'm lucky enough to have a pint or two with propulsion engineers from Armstrong Hall of Aerospace Engineering https://engineering.purdue.edu/Engr/AboutUs/Facilities/ArmstrongHall Fusion rockets are often a favorite topic, for right now, they are less possible than Fusion Reactors, due to the nominal erosion of the combustion chamber, at least in theory, as one has never been tested. Someday maybe, sure, but not today.

Umbran · Feb 15, 2019

dragoner said:
Plus the fundamental truth is that if we could create a vehicle where people could live on some thousands of year journey, we could build an O'Neill Cylinder at a Lagrange Point and live there, not needing to make the long journey.

*sigh*

Any one of you drive out of your way to get a better cup of coffee or taco or anything at all? Or are you people all hyper-efficient, and never do anything that you don't *need* to do?

Fusion rockets are often a favorite topic, for right now, they are less possible than Fusion Reactors, due to the nominal erosion of the combustion chamber, at least in theory, as one has never been tested. Someday maybe, sure, but not today.

That's an issue we may not ever get past, given that what you're basically doing is making a tiny star, and throwing it out the back of the ship. For long-term use, an engine with low temperatures, and few moving parts are good - and that suggests an ion engine as a good choice. Then, you make electricity through whaatever means you want, and pump it into the ion engine. Fusion not required.

Mustrum_Ridcully · Feb 15, 2019

[MENTION=6943731]dragoner[/MENTION] Well, there is still a "long-term" need for your O'Nell Cylinder to fly somewhere else - the Sun won't be there forever. That is really long term, of course, but it's almost the only reason to actually bother with the Cylinder in the first place, I think. If you expect you can stay on the solar system, no planet is really a safer bet than Earth, because the base environmental conditions are just so much better here, even if we assume severe changes due to asteroids, super vulcanos, nuclear war or even zombie apocalypses.

An O'Neill Cylinder that stays in the solar system has a few conveniences that it would not have in deep space flight hasn't. There are planetary bodies and asteroids that could be mined. And there is a sun that radiates energy.

One of the really hard parts is the time in isolation when you're too far from any star system to mine resources or collect solar energy.

Shasarak · Feb 15, 2019

dragoner said:
It's really baby steps to get into space though, the knowing comes from doing, right now, if we built an interplanetary vehicle, it would be very primitive in design, like one of those Duryea cars in comparison to modern ones. That's before any consideration of an interstellar vehicle. Plus the fundamental truth is that if we could create a vehicle where people could live on some thousands of year journey, we could build an O'Neill Cylinder at a Lagrange Point and live there, not needing to make the long journey.

There is always going to be that fundamental human curiosity that drives us to explore. If not that then the bloody mindedness when someone tells us that we can not do something.

And there is always the Mormons.

dragoner · Feb 15, 2019

Mustrum_Ridcully said:
Well, there is still a "long-term" need for your O'Nell Cylinder to fly somewhere else - the Sun won't be there forever.

Though the question is for right now, in the future, I suppose much more will be possible. Even with more powerful engines, we will not need generation ships, as the time, subjective, will be less. Tau Zero by Poul Anderson is a good novelette on the subject.

An O'Neill in orbit can also provide a base for building spacecraft for exploration of the Solar System and beyond. In a sci-fi setting I made, there are those, plus space elevators, where the orbital stations provide Earth with it's manufacturing and food production, and the Earth is like a park.

An O'Neill Cylinder that stays in the solar system has a few conveniences that it would not have in deep space flight hasn't.

I mentioned up-thread of using them in the Mars cycler orbit, they can be stepping stones. There is an old Soviet sci-fi film, A Dream Come True, where they sing "Apple Trees will bloom on Mars ..." A favorite of mine as a child.

One of the really hard parts is the time in isolation when you're too far from any star system to mine resources or collect solar energy.

True, however we could find a rogue planet, current research says they might be more common than we previously thought.

Shasarak said:
There is always going to be that fundamental human curiosity that drives us to explore.

I am 100% for space exploration.

And there is always the Mormons.

Until the Belters steal their ship.

(I was voted one of Avasarala's biggest fans on Shohreh's FB page, unrepentant Earther that I am.)

Mustrum_Ridcully · Feb 16, 2019

dragoner said:
True, however we could find a rogue planet, current research says they might be more common than we previously thought.

Not a direct source of power probably, but a source of resources (and if includes stuff like whatever we use in the reactors, an indirect source of power). Getting things up from a planet is costly, of course, but if it has the resources for it, it might work out in the end.

Do you mean that we would follow that rogue planet around? Because even if they are common, I don't think one could count on the ability of plotting a route that leads us near rogue planets often enough.

But an interesting side-topic - the science behind rogue planets: What would be the basis on assuming the frequency of rogue planets? I don't really know enough about planet formation and star formation to see why planets wouldn't form outside of star systems. It seems the fundamental is always the same - you have a collection of gas and materials, and their gravitational attraction brings them closer together until they collide and can't escape each other. I can somewhat see that a star forming means there is so much mass in the area that additional "mass clumping" are more likely.