No one really describes how to “do” it. Like if I was just going to build something “small” the size of the Earth, the planet has a volume of 197 million square miles. How does one assememble 197 million x 1 square mile blocks and move them from point A to point B?
How did the Egyptians move millions of multi-ton blocks to make the pyramids? On the surface of it the question seems absurd, but the answer is…ropes and wet sand and a lot of human sweat. But I doubt anyone would move 197 million 1 mile square blocks…we’d do it other ways. Start small (relatively speaking) such as how they are proposing to build that space port.
“Starting small” just means exponentially more trips. And that space port is still on the same scale as terrestrial buildings, not mega-earths or ring worlds.
Unless we are talking about exotic technology like Star Trek replicators, tractor beams or nano-builders or whatever, building these megastructures is still a variation of taking scoops of matter from one place, transforming them into building materials, then placing them where they are supposed to go. So other than millions of giant mega-lifters scooping up buckets of asteroids and grinding them into unobtainium blocks for millenia, I’m having trouble grasping how these things are even theoretically constructed.
And unless we develop some miracle way of turning hydrogen, carbon and other basic elements into scrith or metals or whatever, you’re not turning Jupiter, for one example, into a bunch of Ringworld segments.
You don’t build the Great Pyramid on your first try. You start with a small rectangular building made of mud brick. The Egyptians went from that sort of monumental tomb structure to building the Great Pyramid in a few hundred years using wet sand, fire, stone tools and copper chisels and a lot of sweat (well, and beer…don’t forget the beer). Scale up that spaceport as the mud brick rectangular building and consider where we could be in a few hundred years after that.
The thing is, it’s been (and continues to be) the launch costs that makes something like the space port such a challenge. Once you get out into the solar system, once you can support mining the resources are all there. In near earth orbit there is sufficient material to build one of your megastructures with a lot more to spare. The issues are launch cost and logistics support and engineering. We are at the ‘hm, wonder how we could build that large mud brick building’ stage right now. We haven’t actually built more than the equivalent of a small mud building in space so far, partly because of the costs to do even that. But those costs are dropping, and once they reach a certain level it’s going to open up space for exploitation. Then we have to figure out the equivalent of how do we feed the workers and keep them in stone tools and copper chisels, how do we move the blocks of stone from the quarries to the build site and how do we put the thing together? If you have trouble conceptualizing how we’d do it, well, think of some guy living in a small village being told about plans to build a large stone pyramid someday while others discussed that great mud brick rectangle to put the current king in. Today we’ve build a lot of things here on Earth, but nothing on that scale…though we’ve built some pretty massive things (3 Gorges Dam, for instance) so it’s really a matter of getting access at a cost that lets us do what we do, just in space.
Carbon could actually be a very good building material, in the form of diamond, graphene, carbon nanotube and so on.
A greater problem would be trying to find roles for hydrogen and helium, which are the most common elements in the planets (and in the Sun, of course). You can use these light elements to fill balloons, which could potentially add structural strength to a megastructure- I’ve seen proposals to fill large balloons full of these elements to create large atmosphere walls around inhabitable surfaces. Note that you really need to keep hydrogen and oxygen separate- even if they don’t cause a violent conflagration in your habitat, the inevitable oxidation of hydrogen would gradually increase the water content in you environment to uncomfortable levels.
If you don’t have transmutation of elements, then hydrogen and helium might end up surplus to requirements- maybe you could inflate innumerable balloons with the material, creating a swarm of low-density objects covered with photovoltaic surfaces. Useful if you want to collect as much energy as possible, which would be (after all) one of the major goals of swarm construction.
If you do have transmutation, presumably this would be some kind of fusion technology - if so, the fusion itself would produce a surplus of energy, making the whole process incredibly attractive to anyone who really, really wants to capture as much energy as possible. I doubt very much that this is a practical solution - if any alien civilisations in our galaxy were transmuting their local gas giants at any respectable speed, then we’d see this process as an excess of luminosity from certain solar systems. We haven’t seen this yet, as far as I’m aware, so there are probably a number of problems with the process that makes it unlikely.
Stranger, you never do address antimatter-pion, which is a relatively straightforward concept. Containment is difficult but there are methods that will probably work.
Or fusion. Umm, project daedalus style fusors, where did you address that?
What do you define as “conventional”? Also what do you define as a “human lifetime?”
It may be too late for your or me, but it would be silly to think that humans a few centuries from now will turn decrepit and die merely because they are 7-10 decades old. That’s just stupid and while the problems in the way are vast, I think that humans will eventually redirect most of the world’s resources to solving it once immediate needs are met. (frankly I don’t quite understand why that hasn’t already happened…)
I would very much like to hear more of your valuable perspective. I agree, and I think XT agrees, we’re not going to be cramming spaceships full of mini-skirted air hostesses and military officers and sending them to a nearby star using our nuclear arsenal. It won’t work for many reasons, and it is highly unlikely that whatever planetary masses orbit Alpha Centauri are any more marginally habitable than our own Moon or the Jovian Moons or Mars. (as in, not at all habitable but maybe you could use the raw materials)
I really would recommend a look at Atomic Rockets (Project Rho) where the characteristics of most speculative fusion and antimatter drives are reviewed. The Project Orion system is adequate as an interplanetary drive, but really wouldn’t make it to the stars in any reasonable timescale. Project Daedalus was a fly-through, and did not have enough delta-vee to slow down.
http://www.projectrho.com/public_html/rocket/enginelist.php
Antimatter drive is obviously more powerful, but produces dangerous amounts of gamma-rays (and lots of useless neutrinos). Robert Frisbee managed to design a reasonably safe antimatter ship, where the crew were a respectable distance from the reaction- it was 500 kilometers long.
http://www.projectrho.com/public_html/rocket/slowerlight.php#frisbee
I read all that, none of it seemed like showstoppers, and Robert Frisbee’s concept is half as efficient as it could be and it doesn’t use the obvious method of containment. (the obvious method is you fuse your tiny quantities of anti-hydrogen gas to something heavier that is stable. Energy cost to do that is small compared to making the anti-protons in the first place)
As for Project Daedalus, well, obviously it could slow down, you just need a bit more patience. (go at 6% C each side of the trip instead of 12% one way)
Still gets you there. And yeah you can’t be sending biological crew, that ain’t gonna cut it. We’re way too fragile and want too much space. Either we just send our brains or we convert our brains to a digital substrate and just send those.
I guess my perspective isn’t “am I going to see humans go to the stars” but “will life from earth ever expand to the stars”. The answer to the first question is no, unless I am very lucky, but the second question seems to be “yes unless modern physics is basically wrong”.
That would (very approximately) allow the ship to reach its destination, by reducing the fuel required to accelerate and decelerate. The bad news is, it would take 70 years to get to Proxima Centauri.
I do think we will eventually extend life to such an extent that 70 years will be an acceptable journey time- but this will take a couple of hundred years at least. Short answer- we arn’t going to Proxima any time soon.
Well, I don’t think you’d cram the spaceship with ‘skirted air hostesses’ for sure…though I’m guessing there would be at least one ‘military officer’ in the lot. My own position is that if you could build the megastructures in the OP you wouldn’t need to go to the next star over except out of curiosity or adventure, but I think we could do it if we really wanted too…and I think that, today, Orion is the closest technology we have to doing it if we had to. No, you couldn’t do it in a human lifetime, but I don’t think that’s a show stopper…you could do it in 2-3 generations, which I think is difficult but not impossible. Of course, once you can do megastructures it becomes easier, since you could build them out in the Kuiper Belt or Oort Cloud and launch from there with the assist of things like large light sails and laser systems.
I agree that there is unlikely to be more habitable planets at the closest star, but the thing is, once you can build megastructures it’s kind of a moot point. What IS there is Alpha Centauri C, which is a stable red dwarf…and that could be worth the trip alone, at least somewhere down the road. Our own star has a shelf life of a few billion years, while Alpha Centauri C is measured in trillions, making it attractive for that alone (though once you get to a certain level it’s again moot…a sufficiently advanced civilization could modify our own star by lifting material directly from it, giving it a higher shelf life).
At any rate, whether we can or will go to the next star over is kind of beyond this discussion. The OP isn’t really asking about them, though peripherally having megastructures enables you to more easily contemplate things like going to another star. After all, if you can keep a population going on a megastructure in space you can probably keep a star ship going for a couple of generations going to another star.
I was trying to poke fun at a 1960s concept, where it might have seemed like interstellar missions were right around the corner. Also, thisTV mini-series. If the stars were a thousand times closer, I could imagine some alternate reality where this really happened.
As for 2-3 generations, that is a showstopper. Most humans are not going to invest the vast resources you are talking about into an effort they will not personally live to see the payoff from. Some humans would but not enough of them to fund something this expensive. We won’t be going to the stars until we’ve found some way for the original crew to arrive at the destination, hale and hearty and mission capable. And for the mission backers back on earth to feasible be around when transmissions from that mission reach Earth.
Hence the sci fi concept of freezing them, though as you know and I both probably know, we will likely develop some type of appropriate artificial intelligence instead. That’s because even frozen humans would still be accumulating radiation damage, while electronic circuitry could be perpetually inspecting it’s memory, finding corrupted bits from cosmic rays and failed circuitry, and perpetually restoring the corrupted bits from redundancy data and re-allocating away from the failed circuitry. There are straightforward solutions in the math that would lead to outcomes like “1 unrecoverable failure per billion years” or some other absurdly reliable level of data integrity.
What do you base that on, exactly? Humans have invested thousands of years in some cases on some shared project. Europeans invested hundreds of years in building cathedrals to their God in fairly recent history. Polynesian’s invested hundreds of years in exploration and colonization of the Pacific. The Native Americans dedicated generations to the same thing in the new world…as did Europeans later down the road. So, not seeing it as a showstopper. The big challenges are technical, not social such as you seem to think here.
Getting some sort of hibernation technology would just make it easier but isn’t necessary. What IS necessary is not propulsion either…it’s the ability to keep the crew alive and functioning and the equipment running.
You know, smaller than a Dyson sphere, you could (in fiction) build a shell around a gas giant at the level that the gravity would be equal to Earth’s (or any other alien planet with a surface gravity lower than that of the gas giant’s cloud-tops), cover that with soil and water and air, and have a big-ass living surface that behaves like a normal planet. Anybody know books that use those off the top of your heads? (Googling shell around Jupiter tries to give me the locations of gas stations in Jupiter, Florida.)
I think one of the videos XT linked to describes that as a “mega-Earth”. Really they describe it as a giant shell you then fill with hydrogen, but I don’t see a reason why you can’t just start with an existing gas giant.
Flip this the other way. What’s the lowest effort way to go?
The lowest effort way that would still provide basically all the benefits of a planet is you inflate a balloon. In a long, skinny cylinder. The balloon does not spin and the fabric is kevlar/carbon fiber mesh.
Around this balloon is basically just bags of space sand. Basically it’s mining tailings, which are going to be roughly the size of sand particles.
Inside this balloon, you build a structure made of metal plates that is a few hundred meters in radius, ideally. It’s got apartments and parks and offices and all that, the plates are just metal pieces bolted or welded to each other. There’s bearings at the ends and there’s outer rings with seats you can get into. So you board from the low gravity section, it’s all pressurized, get into the outer ring, sit down, and the ring spins up to match velocity with the habitation structure. You then just open a door on the other side and walk in.
You would hear the “wind” whistling over the structure all day and night.
There is a second structure of about the same mass as the primary one that you can get into by boarding an intermediate ring in between them that spins up and down all day to match.
The second structure probably has farms and processing equipment that benefits from the spin.
Finally there is a third, counterweight ring all the way at the end. It speeds up and down to compensate for people and cargo and liquid changing the weight distribution between the two main rings. (you move things like sewage and clean water between rings by pumping them into a tank in the intermediate ring, having that ring decouple and match speeds with the other ring, and then it offloads)
The net angular velocity of this whole thing is zero. Any time you have a problem, you engage some brakes, and spin the whole thing back to idle. The metal pieces are obviously made by laser 3d metal printer or something, from a powder processed from asteroid ore. Large sections of the habitat are all in low gravity, including the factories and spaceports and all that.
This is even lower effort than “O’Neil cylinders” and other such proposals since you are not spinning a whole station. I actually have never heard of this proposal, though I am sure I am not the first to think of it.
You could turn the mass available in our solar system into probably millions of separate habitats like these. They have a serious advantage in that each one is easy to fix, losing one is no big deal, each one is relatively low tech, and so on. 30-100 feet or so of asteroid sand (which isn’t spinning, it’s just passively sitting in bags around the outside) provides about the same protection from rads as a planet. You could get a full G from the ring if it turns out humans need it. (probably not, we can probably get by with maybe 0.5 to 0.8 and live normal lives I suspect, but that hasn’t been proven)
I think this shows up in the later chapters of Accelerando (by Stross).
Checking - not quite - they use a floating platform above Saturn’s clouds (high enough so that the gravity is Earth standard)
I’ve seen science fiction about cities floating in Jupiter’s atmosphere, even high up in Venus’ atmosphere.
Cloud City in Star Wars is a gas mining facility, 59,000km above a gas giant’s core in a breathable portion of the atmosphere. Which is really really strange that a gas giant would have a breathable atmosphere of mostly Oxygen at that altitude, although the altitude itself is not an issue with the right size of gas giant. It would need to be only slightly larger than Saturn and smaller than Jupiter. You’d also need some hellacious shielding just to survive the radiation, I’d think.
The top of Jupiter’s clouds are at around 2.5g. To get the shell at 1g, you would need to build it thousands of miles above the cloudtops. (Or thousands of miles below, but that takes a whole different type of fiction magic.)
These are called suprashells; the concept was largely developed by Paul Birch of the British Interplanetary Society. Here’s a shell around Uranus (no pun intended) with an image by me:
heres a Jupiter-like planet with a strip suspended above the clouds, also one of mine;
http://www.orionsarm.com/eg-article/564de72a02e9a
(these constructs use orbital rings, a technology that presupposes the fine control of powerful magnets and superconducting levitation, which might be tricky to achieve on this scale).