Type 1 Dyson Sphere

[Nicholas_Bostaph]

I was curious to hear everyone's thoughts on how plausible humanity building a Dyson Sphere is. I've spent about 4 hours googling for information but came up with mostly basic definitions of "Dyson Spheres" or guesses by the uninformed. So I thought I'd try here considering all the intelligent people that I know hang around.

In case you're not familiar with the theory, a Dyson Sphere is a construct to harness all of the sun's energy. There are basically 2 types. A type 2 is a solid sphere built at around Earth distance from the star. It is generally viewed as having a slight rotation to generate gravity near the equator for living areas. The stress and engineering problems show this approach to be near impossible. A type 1 sphere, however, is slightly different in that it is made up of a large number of smaller satellites orbiting at that distance from the sun. Some good basic information can be found here: http://users.javanet.com/~jasp/dyson

Considering our current technology level, I was wandering if a type 1 sphere might be within our ability to build within the near future. I imagine that to construct the satellites we'd first want some kind of mining colony, perhaps on the moon, and a construction facility probably in orbit at L5. That would avoid the problem of having to launch something so massive. The benefits of both energy and living space would be enormous though.

Thoughts? Might this (the first few satellites, not the whole sphere) be a possibility in our lifetimes (I'm young ) or am I way off here? I'm still a beginner when it comes to astronomy and physics but I'm very interested in learning. Thanks.

[russ_watters]

There are some quick and easy calculations you can do on the size of such projects based on the size of Earth's orbit. You will find that constructing even a tiny percentage of such a structure would be a vast undertaking - probably requiring more building materials than there is mass on earth.

Also note, it costs roughly $10,000 per pound to send something into low earth and probably more than double that to send it into deep space. Assuming within your lifetime they got that number down to $1,000 per pound, again, you can easily see how covering a small percentage of such a structure would require many times the world GDP.

[Nicholas_Bostaph]

what about the possibility of mining the moon or Mars. That would cut the actual costs of launching the building materials into orbit down substantially. Even if a tiny portion of the sphere is completed, those satellites would still provide enough energy and living space to be economically attractive, wouldn't they?

[Chuck]

Each satellite could be given the job of building duplicates of itself in the asteroid belt. They could increase their numbers exponentially. When they run out of asteroids they could start mining the planets and moons.

[TriangleMan]

Cost-benefit analysis is needed here. Does the energy benefits of a Dyson sphere outweigh the costs (space missions, mining Moon/Mars, setup and upkeep of sphere)? I think that there are more cost efficient ways to get energy then building Dyson spheres such as setting up solar panels on the Moon or continuing research into more efficient nuclear energy.

Just my 2 cents.

[Grey]

Thoughts? Might this (the first few satellites, not the whole sphere) be a possibility in our lifetimes (I'm young ) or am I way off here? I'm still a beginner when it comes to astronomy and physics but I'm very interested in learning. Thanks.

It's a cool idea, but probably not for quite a few lifetimes to come. Heck, we haven't even established a base on the moon or Mars, and those would require far less engineering effort. Oh, and on that specific website, it mentions the type I as being composed of rings. Although individual orbiting bodies would work, rings are dynamically unstable, so that would be a bad way to go!

[logicboy]

It would have to be a sphere around the whole sun in order to get all of the energy. this reminds me of a Star Trek Next Gen Episode. You know the one where they meet Scotty.

If we had Star Trek tech it would be possible, just build one satellite w/replicator and have it duplicate itself.

[pmcolt]

In our lifetimes? Maybe if you plan to live to be 1000. I'd be happy just to see footprints on Mars by the time I'm 35 (which'll be in 2017 or so).

I think Dyson's original concept involved a Jupiter mass of material. I guess the first satellites would be built from materials mined from the moon, near-Earth asteroids, and Earth. Putting a lot of fabricated satellites into orbit around the sun outside Earth's orbital radius seems like something we could do easily, given that we already had such mining facilities and the associated space infrastructure to move the raw materials around. But we still seem to be a long way off from that.

The ultimate benefit is being able to harness the entire energy output of the sun. I remember someone (can't remember whom, can't site, somebody slap me) proposing the alternative of building an array of solar collectors around the sun inside the orbit of Mercury. They would be supported by radiation pressure, with a gap left around the ecliptic so that the planets would still get sunlight. Then we would build a 'cloud' of independent habitats at Earth's orbital radius (sort of like the type 1 sphere) to capture some of the energy leaking out through the gap and provide additional habitable space for humans.

But I'd hate to be the guy who had to try to get Congress to approve funding.

[tjm220]

What would happen to the sphere as the sun ages and gets more luminous?

[darkhunter]

Each satellite could be given the job of building duplicates of itself in the asteroid belt. They could increase their numbers exponentially. When they run out of asteroids they could start mining the planets and moons.

As long as they are uninhabited... :wink:

[P. BOOM!]

Maybe with a width of only a mile. That would add up to alot of space!

[russ_watters]

Maybe with a width of only a mile. That would add up to alot of space!

The earth's orbit is roughly 90 million miles in radius. Thats 565 million square miles. Thats slightly smaller than the surface area of the Earth.

[nebularain]

OK, so if we strip the Earth of its surface, we'd have enough silicate material to form a line around the sun! :-? :wink:

[Dickenmeyer]

What would happen to the sphere as the sun ages and gets more luminous?

If it is made up of zillions of independantly orbiting units then we would just nudge them out into more distant orbits. That's a good reason not to build a solid sphere.

[SAMU]

I suspect that the natures of building "Living Space" on a large scale in space will be fundamentally different from simply capturing energy from the sun. To capture the energy most efficiently we should put the capturing satelites where the sun's light is most intense i.e. as near to the sun as we can build them to survive. Transmit the energy via microwave or x-ray lazer. Then build them on a build as needed basis. As our spacefairing civilisation grows we build more of the satelites. Eventually we have a Dyson Sphere but then we will be using all the energy the sun has and will have to reach to other stars for further growth. Be that as it may. Mercury as the source for raw materials for the majority of the construction elements seems reasonable as being closest to where we want the satelites and having the more intense power source of the sun close at hand. Of course we would have to start with the moon for much of the initial raw materials as it has a lower power requirement to lift the raw materials to the Mercurian orbit.


Regarding the transmission of power by x-ray lazer. Question: If large amount of power transmitted over interplanetary or interstellar space by x-ray lazer intersects with dust and gas in space. What sort of radio signature could it produce that might be detectable from a great distance?

One aspect of the signature may be (depending on the type of radiation it produces) that it could be coming from a straight line source. This could be something to look for in the Search for ExtraTerrestrial Inteligence.

[darkhunter]

What would happen to the sphere as the sun ages and gets more luminous?

If it is made up of zillions of independantly orbiting units then we would just nudge them out into more distant orbits. That's a good reason not to build a solid sphere.

Or We've learned enough about solar physics to control it...

[wedgebert]

All you gotta do is apply some device that replaces the helium and higher elements with hydrogen again. Fission won't work bacause it would take more energy to split the atoms then you would get fusing them back together, and if you have that much energy why do you need the sun?

[pmcolt]

Expansion joints. Big ones. As the sun becomes more luminous, we make the sphere bigger and bigger. Or we adapt ourselves to the increasing luminosity.

Or you could just do what they did in Star Trek TNG and abandon the Dyson Sphere. Let's see, how long would it take to evacuate a sphere? :-?

Come to think of it, there was also a TNG episode where they try to reignite a star. Wasn't there a discussion about that somewhere on these forums awhile back?

[Emspak]

Friends, Romans, Countrymen---

Here are some simple calculations as to the amount of mass required for a Dyson Sphere--

1. Radius of the Earth's orbit is about 150 million km or 1.5 * 10e11 meters

2. Total surface area of the sphere is then 4πr^2

3. So we get about 1.9 * 10e23m^2 of space

If we assume that the sphere has thickness of only 1m and is made of little cubes all strung together (the sphere would look like a giant globe with gaps between the cubes) we get 1.9*10e23m^3 of material.

If it is only as dense as water that is 1.9*10e23 metric tons, or 1.9*10e27 kilograms.

The Earth weighs 5.972e24 kg.

So we need something at least 1,000 times as massive as the Earth -- the only body that qualifies is Jupiter.

Probably need to eat Saturn as well. If we do a Type 1 sphere that uses only 1/100 the mass (giving 1% covereage of the sun) we still need a 10-Earth-mass body -- need to use Uranus or a lot of asteroids. (Remember the total mass of the belt is relatively small - about 2*10e21 kg for the 3,000 or so known bodies -- even if you triple it for stuff we haven't seen yet you get less mass than is on Earth).

Technologically possible? Almost anything is. Worth it? Dunno. What do you need all that energy for, anyway?

[Alex W.]

There isn't that much mass in the asteroid belt, really. And you run the risk of us all being turned into grey goo...

I joke, but anyone who likes a fish supper is a good heir to the throne in my book...

[kckempf]

The real problem with the Dyson's sphere idea is that, to construct it, we would have to dismantle a planet, perhaps two, to obtain the materials necessary for even the one mile strip suggested by people previously on this board. Not only do we have to get material of that mass, but we have to obtain the elements necessary for humans to survive on the surface of a narrow sheet of rock. Then, we have to find materials necessary to create an atmosphere necessary for human survival. Then, we have to find water. Then, we have to find fuel to counteract the slowing of the rotation of the strip due to the Sun's gravity. It would be far simpler to create colonies on other planets and satellites and to create our own independent space colonies than it would be to create a Dyson's sphere.

[wedgebert]

The real problem with the Dyson's sphere idea is that, to construct it, we would have to dismantle a planet, perhaps two, to obtain the materials necessary for even the one mile strip suggested by people previously on this board. Not only do we have to get material of that mass, but we have to obtain the elements necessary for humans to survive on the surface of a narrow sheet of rock. Then, we have to find materials necessary to create an atmosphere necessary for human survival. Then, we have to find water. Then, we have to find fuel to counteract the slowing of the rotation of the strip due to the Sun's gravity. It would be far simpler to create colonies on other planets and satellites and to create our own independent space colonies than it would be to create a Dyson's sphere.

Not necessarily. Noone says you have to make the inside of the sphere or ring Earthlike. You could easily just build structures on the inside to live in.

You should read The Time Ships by Stephen Baxter sometime. It's a sequel to the Time Machine, and while visiting a different timeline, the guy discovers that the Morlocks have built a sphere around Sol. At first the sphere is pretty thin, but since they're capturing 100% of the sun's output, the use that to slowly (very slowly) make the shell thicker.

[JohnD]

All,
No one has mentioned Larry Niven's RingWorld, as described in several novels. The RingWorld is a Type 1 sphere. As an SF writer, Niven is dedicated as far as possible to science fact, but he had to assume a material with an unfeasibly high tensile strength, "scrith", for the RingWorld structure. To generate one G at the surface, RingWorld must rotate at over 700 miles/sec.
His fans pointed out so many defects in his original description that they became major points of the sequels!
Eg.1/ stabilisation jets - the Ring's orbit is not stable, like a planet's. Its centre ocillates widely, as if the Sun was bobbing up and down. This severely changes light and temperature on the Ring, and it could just fly off alone. Niven postulated 'Bussard ram-jets' on the rim to control the orbit!
Eg.2/ Meteor defense - a planet will survive an apocalyptic meteor strike, but a Ringworld could be destroyed (Niven's only just survived one), so there is a mechanism to make solar flares lase (!) and destroy dangerous planetoids.

The theoretical/technology/systems/materials problems are so great that even a Type 1 sphere seems unlikely, and where is the evidence for Type 2 spheres out there?

To see what Ringworld would look like, go to:
http://www.rahul.net/rootbear/graphi...world/rw0.html

John

[Shadowhawk]

A more realistic (ha!) Dyson sphere would be somewhat more than a meter thick and made of water. You're looking at stellar-level masses there.
And we'd probably need some sort of gravity generators, because spinning it would make only a miniscule portion of the surface habitable. Still, it'd be nice to have a surface area of billions of Earths to expand on.

A Ringworld, by contrast, could probably be made from Jupiter, and you could spin it for useful gravity. And 3 million Earths worth of surface area sure isn't anything to sneeze at.

A third, and even better option, are Orbitals (from the Culture series). Think of a Ringworld, except being only about a million kilometers in diameter rather than 300 million, and in orbit around the sun, rather than circling it.
You can get something with a similar surface are to Earth, spin it for gravity and night (so you don't have to deal with shadow squares), you don't need any super-exotic materials to make it, and you don't have to deconstruct your solar system for materials. Plus, you could put a few of 'em in orbit. As an added bonus, it doesn't quite blow the Reality Circuits of your brain when you look at one.

[Chuck]

If a smaller surface area would do we could build the sphere closer to the sun and live on the outside. Build it at the proper distance so the sun's pull would produce the desired gravity. For one earth gravity the sphere would have about 330,000 times the surface area of the earth, plenty of room. There's probably no need for us to labor under a full earth gravity so we could actually make it bigger. It might tend to get hot underfoot, but we could let out some of the light to power our machines, launch solar sails, and signal other stars. As future generations got used to the lesser gravity the sphere could be expanded which would create more living room.