One blogger I like suggested a long time ago that, until such time as we have a thriving metropolis in Antarctica, it’s silly to imagine we’ll ever colonize another planet.
After all, as inhospitable as it may seem to human life, Anatarctica actually has an atmosphere, with real, breathable oxygen. That alone makes it FAR more suitable for human colonization than ANY planet or asteroid we’re ever likely to encounter.
Exactly. Look no further than Mount Everest: 4.3 fatalities for every 100 summits and it’s so crowded these days that climbers are getting into fistfights.
You want to go to another star system. You don’t have FTL so you need a generation ship most likely. That being the case;
Find an inbound comet, preferably one that’s been on a huge loop so hasn’t used up a lot of its volatiles/water during inner-system passes. Put engines on it sufficient to nudge it into a shorter term inner-system orbit (maybe 50-75 year period) using the planets for braking. Once confirmed on its path, start hollowing it out (the rocky core) and making your generation ship inside the comet. The combination of the rocky core and thick water-ice shroud will protect from interstellar radiation, and will provide reaction mass for engines. Hollowing out an existing rock is cheaper-easier than a purpose-built ship, and even though it’s not in Earth orbit, it’s still within the solar system and reasonably accessible (if you can wrangle a comet, likely you can move within the system easily).
Figure the construction will take one orbit of 50+ years. During that time, you gain experience and knowledge in building/maintaining your comet-ship, and that knowledge is passed along to the next generation who will actually take up residence. Then they ride out one more orbit of 50+ years to gain the knowledge of actually living in the ship, shaking out the kinks, etc. while still close enough to Earth that if anything goes wrong or needs adjustment, rescue is possible. Maybe giving 50 more years of development on Earth, new technologies could be incorporated during the final inbound leg of the journey.
Then, assuming all is well, you light the fires and add enough thrust (using slingshot effects as well) to boost the comet-ship out of the solar system and on its way. You have a massive ship with lots of reaction mass, living space, and shielding, 50-75 years of actual living experience on board before launch, and you don’t have to expend the energy to move it from a stand-still, so you take advantage of its inherent velocity at the start. Admittedly it takes 100+ years from initial capture to launch, but the time would be well spent and the savings on construction may well be worth it. You likely won’t achieve an appreciable fraction of .c (not even 1% probably, but who knows, depends on how much of your mass you want to use up in thrust there and on arrival), but you’ll have everything you need to improve the chances of success.
Whadda ya think, sirs?
In 1850, Scientific American said the exact same thing about human flight.
I think you are doing a lot of handwaving. If you can move around the solar system that easy and hollow out a comet in space that easy, you can probably just build a giant spaceship in Earth orbit just as easy.
Personally I think the idea of a generation ship is stupid. Space is a harsh, unforgiving environment and basic engineering tells us that at some point over the hundreds or thousands of years the ship is in flight, something will fail that can’t be fixed.
If you can build a generation ship capable of getting to another solar system, you have incidentally negated your need for planets - you can live in space indefinitely - and that being the case, why bother going to another solar system?
I am feeling sad that my awesome ideais getting no love. 
Well I’m just trying to think outside the box a bit. The main reason I chose a comet is that it solves the shielding and fueling problem in one shot, and also the act of hollowing it out may produce materials that help fund the project. Also, it is still easier to dig tunnels and chambers than build a ship from the keel (or spine I guess) up using manufactured materials. And a several-mile-wide comet is likely to be a lot sturdier than a spindly construct.
Yes, generation ships are not the best way, but they may end up being the only way, IF we want to do it at all. Yes, if you can build a comet-ship, you can just live in it here in our solar system just as easily. I, however, think that humanity still has enough curiosity and drive that we’ll try to go to another star someday, no matter how impractical.
or we could swallow our pride and just send the stronger and more intelligent robots instead
Where do you get that idea from? There’s a reason we don’t make ocean-going ships out of hollowed out boulders. Balls of ice and rock tend to be fairly porous. At the very least they are structurally irregular and unstable. Especially if you hollow the damn thing out. Much easier and more consistent to build a structure in orbit IMHO.
Not to mention you will be pushing around orders of magnitude more mass compared to say, a large geodesic structure covered in panels. Even if they are armored against micrometeorites.
Also think about this. It’s going to take possibly thousands of years for a generational ship to reach it’s destination. That means all their machines and systems and a society of maybe 5000-10000 people need to stay intact longer than modern civilization has existed. If science fiction has taught us anything, there is about a 50/50 chance that by the time your Space Arc reaches it’s destination, the inhabitants will have long forgotten they are inside a vehicle.
Another issue with the generational ships:
There is a concept called the Incessant Obsolescence Postulate. Basically the idea is that if an interstellar trip will take more than 50 or so years, we would be better off postponing it. What would likely happen is that propulsion technology will advance such that the next mission will catch up and pass the first ship.
I guess I missed that day in my “basic engineering” classes. I was under the delusion that things lasted as long as you built them to last.
Most stuff today doesn’t last long because people don’t want it to last long. We could have 1000-year cars, but they would be hugely expensive and low performing.
People now are building a clock that will last 10,000 years. Yes, a starship is more complicated than a clock, but the point is that it tells us nothing that the average wall clock breaks after 5. The 10,000 year clock required a great deal of thought, but it didn’t require any massive breakthroughs–just basic engineering.
Mechanisms don’t break; materials do (or they wear, or they corrode, or whatever). But materials are pretty well understood, and often we can vastly increase the lifetime of a component by only modestly decreasing the stresses. For instance, cutting the stress on an aluminum item by half may increase the lifetime by a factor of 5,000. We don’t necessarily do that today because a factor of 5,000 may be meaningless on a device designed to last 10 years. If it needs to last much longer, and with greater safety margins, then a factor of two is a pretty reasonable cost.
The ship would have small but definite losses of various things. For instance, every time an airlock is opened, some air will be lost into space. You just can’t keep doing that indefinitely. We also don’t know just what effects long term low gee will have on the human body, and whether or not humans can successfully reproduce and raise kids in low gee.
Don’t get me wrong, I’m all for space habitats, and I think that it would be a good idea to have people living on them for several generations before we try interstellar traveling. But even large habitats are going to need some way of replenishing their basic components.
Low Gee?
Gahhhhh…SPIN THE SHiP…problem solved…as much gee as you want.
I’ve even seen this technology at county fairs.
Zero gee is a feature of space if you want it. Its not a REQUIREMENT.
Sorry, but this whole low/zero gee thing makes me stabby. Don’t get me started.
No, we won’t be ready to consider a generation ship until we have experience in long-term sealed biomes, like those marvelous, shiny O’Neill bubbles of the '80s. First in Earth orbit, then the asteroid belt, then the Oort Cloud, then disperse like dandelion seeds. Long-term goals here, and I am certain ther will be any number of dare-devils saying “I’m out of here” and dying along the way.
Assuming we reach the level of technology necessary to build a Starship, why not take all of that tech and renovate Mars? Its close, not too cold, and house lots are cheap. Later on, we might even tackle Venus. No need to go light years for something close at hand.
Ok, I’ll admit it, I’m just trying to re-create the Comet Empire.
Once travel time within the Solar system drops to weeks rather than months or years, there will be people wanting to move far enough away to no longer be within anyone’s potential sphere of empire.
Maybe you haven’t taken that class yet where they show you all those spectacular engineering failures like the Tacoma Narrows collapse and whatnot. Things sometimes don’t last as long as you think they will.
I would be curious as to how one would design a car that lasts 1000 years (I assume you mean with no replacement parts and subject to normal use).
Dude, the only man-made thing that has lasted anywhere near that long is the Great Pyramid of Giza. And that has no moving parts. AND it looks like shit!
We haven’t even had industrial machines for more than a couple hundred years, let alone ones that worked for hundreds or thousands of years.
You can’t just make everything thinker so it lasts longer. Maybe it is just an engineering exercise in calculating metal fatigue and failure rates and whatnot. But it’s an extraordinarily complex one when you consider that this ships has to contain everything 10,000 people will need for a thousand years.
I assumed we would have already terraformed Mars, Venus and maybe even some of the Jovian moons by the time we start thinking about the stars.
Yes, of course engineering failures happen. But they aren’t inevitable, and with every failure, lessons are learned.
The Tacoma Narrows bridge was built outside known best engineering practices. It was not nearly stiff enough, and although the aeroelastic flutter that destroyed it was not well-understood at the time, the bridge would have been fine if it had been built to the same standards as contemporary bridges.
In a sense, it was probably a valuable experiment. But a generation ship would not want to make the same optimistic assumptions, and stay well within the envelope of existing engineering standards.
Well, clearly I can only sketch out a design. And there will have to be some wear items; for instance, I don’t know how to get rid of tires. But I think the main components can be made to last a very long time.
The powertrain is the main thing to get right. I think a turbine hybrid system would work rather well. Turbines are simple devices, with few moving parts. At high speed they put high stresses on their materials, but if we sacrifice efficiency and power density, we can vastly extend the lifetime.
An electric hybrid system acts as the transmission. On the turbine side, the generator allows the turbine to run at a constant speed, with corresponding low stresses. Just as importantly, you want to adjust the power delivery smoothly, so as not to cause steep thermal transients. An electronic controller can enforce this.
Electronic units can be very reliable, but only when designed for long life. For instance, you can’t use electrolytic capacitors (except possibly the solid state variety). ICs should be fabricated with large traces and run at a low voltage (to minimize electromigration and other stuff).
We probably want the turbine to be always running, even when parked. Fluid bearings are very simple and reliable, but they experience a small amount of wear on every start/stop. They probably wouldn’t last 10M start/stop cycles, but 10K is probably ok. So just try not to cycle it more than a few times a year.
Anyway, there are a million other problems to solve, and I don’t want to get too tangential.
There are many ceramic/stone items that over ten thousand years old and are as good as the day they were made. Modern ceramics are even better and will be an important part of any high reliability system.
Again, no one has tried.
Thicker parts is just one example among many. However, the principle of staying well within the operational envelope is a general one. Virtually everything built today pushes one limit or another so as to maximize efficiency, or minimize cost, or the like.
There’s a reason that no lightbulb today will last more than a couple thousand hours, whereas there’s an old carbon bulb in a fire station that’s been running for over a century. It’s because modern light bulbs straddle a fine line between light output and lifetime, while the old carbon bulb was overbuilt, and long lasting if not efficient. Take a modern bulb and run at 80 volts or so, and it will last essentially forever (but it won’t be very bright). Just about everything makes the same kind of tradeoff in one way or another.
Anyway, you are correct that it will be extraordinarily complex. I never said it would be easy.
Terraforming is way harder than a generation ship. Self-sufficient colonies are probably a necessary condition, though.