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Welcome to lets build a dyson sphere! In this episode we'll be using solar sails and counterweights.

As usual we build at 1AU away from the sun.

The counterweight masses 1000 metric tons. Newton's law of gravitation tells me that it will fall toward the star at 0.006m/s/s (6000N of force toward the star). Wikipedia tells me that a sail would require 700kg/N so to get those 6000N requires 4.2million kg sail. Also from wikipedia I find that the material weighs 7g/m^2 and thus the sail has an area of 600million square meters.

A sphere with a radius of 1AU has an area of 2.8e23 square meters . There is room for 460 trillion segments. In practice not all of these can be put in place because of the danger that they might interfere with each other or crash. Let's assume 300 trillion can be put in place.

Each segment has a mass of 5200 metric tons. The whole dyson masses 1.56e18 metric tons.

1-http://www.wolframalpha.com/input/? i=gravitation+constant+%28%282e30kg*1e6kg%29%2F%28
1.5e11m%29^2%29
2-http://en.wikipedia.org/wiki/Magnetic_sail
3-http://www.wolframalpha.com/input/?i=sphere+with+150000000000m+radius


Now here's my problem: I've always had the impression that to burealistic dyson swarms says that you would need to disassemble multiple planets to make it work. However this let's me block about 65% of the star's light and requires less than the mass of the moon to build.

Are my assumptions or math wrong somewhere?

Originally posted by Symmetric Chaos
Welcome to lets build a dyson sphere! In this episode we'll be using solar sails and counterweights.

As usual we build at 1AU away from the sun.

The counterweight masses 1000 metric tons. Newton's law of gravitation tells me that it will fall toward the star at 0.006m/s/s (6000N of force toward the star). Wikipedia tells me that a sail would require 700kg/N so to get those 6000N requires 4.2million kg sail. Also from wikipedia I find that the material weighs 7g/m^2 and thus the sail has an area of 600million square meters.

A sphere with a radius of 1AU has an area of 2.8e23 square meters . There is room for 460 trillion segments. In practice not all of these can be put in place because of the danger that they might interfere with each other or crash. Let's assume 300 trillion can be put in place.

Each segment has a mass of 5200 metric tons. The whole dyson masses 1.56e18 metric tons.

1-http://www.wolframalpha.com/input/? i=gravitation+constant+%28%282e30kg*1e6kg%29%2F%28
1.5e11m%29^2%29
2-http://en.wikipedia.org/wiki/Magnetic_sail
3-http://www.wolframalpha.com/input/?i=sphere+with+150000000000m+radius


Now here's my problem: I've always had the impression that to burealistic dyson swarms says that you would need to disassemble multiple planets to make it work. However this let's me block about 65% of the star's light and requires less than the mass of the moon to build.

Are my assumptions or math wrong somewhere?


I have not done any math on this, yet, but I was under the impression that a "feasible" statite "matrix" would require far less mass than the moon.

Also the statite proposal is supposed to account for that interference you spoke of because each would have its own propulsion system and counterweight, holding it at a static distance from the sun. That solves for the whole "moving" sun problem that the shell had.

And what were you referring to when you said "segments"? I am lost, there. Wouldn't it be closer to really really flat cylinders? Also, the statites would not interfere with one another as they could be "perfectly" suspended. There would still need to be maintenance, which is beyond our means, right now, and some way to avoid "intersteller" debris/objects.

Originally posted by dadudemon
And what were you referring to when you said "segments"? I am lost, there.

I'm assuming that each piece of the shell is shaped like this:

. . . . . . . . . . . . . . . . . .|
888. . . . . . . . . . . . . . . |
888---------------------|
888. . . . . . . . . . . . . . . |
. . . . . . . . . . . . . . . . . .|

The weight falls toward the star while the sail is pushed away. You can alter the balance point by making the connecting wire longer or shorter.

Originally posted by dadudemon
Also, the statites would not interfere with one another as they could be "perfectly" suspended.

But they still need to be far enough apart to avoid crashing. So maybe we can bump the number up to 400 trillion.

Originally posted by dadudemon
There would still need to be maintenance, which is beyond our means, right now, and some way to avoid "intersteller" debris/objects.

I know, I've read Ringworld

this...

http://img710.imageshack.us/img710/7964/dyson.jpg

I will wait until the crew of the enterprise finds it once more

Originally posted by BruceSkywalker
this...

http://img710.imageshack.us/img710/7964/dyson.jpg

I will will wait until the crew of the enterprise finds it once more

No, not that. Building a solid shell requires serious superscience and I'm trying to avoid that.

Originally posted by Symmetric Chaos
I'm assuming that each piece of the shell is shaped like this:

. . . . . . . . . . . . . . . . . .|
888. . . . . . . . . . . . . . . |
888---------------------|
888. . . . . . . . . . . . . . . |
. . . . . . . . . . . . . . . . . .|


The weight falls toward the star while the sail is pushed away. You can alter the balance point by making the connecting wire longer or shorter.


Peens? awesome



Anyway...oh. I thought it was something else. Word disconnect because I call that 'ropey' thingie that "weight" is attached to, the "tether".





Originally posted by Symmetric Chaos
But they still need to be far enough apart to avoid crashing. So maybe we can bump the number up to 400 trillion.

Well, the entire area would need quite a bit of space, but they could be packed in quite tightly and get much more than 65% "solar coverage".



Originally posted by Symmetric Chaos
I know, I've read Ringworld

I have not. *googles* Looks interesting.

Can we build a Dyson vacuum cleaner instead?

Originally posted by Symmetric Chaos
Welcome to lets build a dyson sphere! In this episode we'll be using solar sails and counterweights.

As usual we build at 1AU away from the sun...

...Are my assumptions or math wrong somewhere?

So...been doodling much lately? What's the impetus? Drunken wager? Shot at full scholarship?

Question: if the mass of the moon gives you 65% coverage, why not cannibalize more mass (get some of the big asteroids, like Ceres) for more coverage? And to prevent collisions, why not anchor/stabilize all the collectors with nanotubes girders, (think giant Tinker Toy construct)?

Let me know if/when you get into starship design.

Originally posted by Symmetric Chaos
Welcome to lets build a dyson sphere! In this episode we'll be using solar sails and counterweights.

As usual we build at 1AU away from the sun.

The counterweight masses 1000 metric tons. Newton's law of gravitation tells me that it will fall toward the star at 0.006m/s/s (6000N of force toward the star). Wikipedia tells me that a sail would require 700kg/N so to get those 6000N requires 4.2million kg sail. Also from wikipedia I find that the material weighs 7g/m^2 and thus the sail has an area of 600million square meters.

A sphere with a radius of 1AU has an area of 2.8e23 square meters . There is room for 460 trillion segments. In practice not all of these can be put in place because of the danger that they might interfere with each other or crash. Let's assume 300 trillion can be put in place.

Each segment has a mass of 5200 metric tons. The whole dyson masses 1.56e18 metric tons.

1-http://www.wolframalpha.com/input/? i=gravitation+constant+%28%282e30kg*1e6kg%29%2F%28
1.5e11m%29^2%29
2-http://en.wikipedia.org/wiki/Magnetic_sail
3-http://www.wolframalpha.com/input/?i=sphere+with+150000000000m+radius


Now here's my problem: I've always had the impression that to burealistic dyson swarms says that you would need to disassemble multiple planets to make it work. However this let's me block about 65% of the star's light and requires less than the mass of the moon to build.

Are my assumptions or math wrong somewhere?

How will the sun's angular momentum effect the dyson sphere, or will it?

Originally posted by Mindship
So...been doodling much lately? What's the impetus? Drunken wager? Shot at full scholarship?

I was curious about how feasible the design was. The FTL drive I'm working with makes gigascale construction feasible for groups that build their own.

Originally posted by Mindship
Question: if the mass of the moon gives you 65% coverage, why not cannibalize more mass (get some of the big asteroids, like Ceres) for more coverage? And to prevent collisions, why not anchor/stabilize all the collectors with nanotubes girders, (think giant Tinker Toy construct)?

I wasn't calculating based on mass. The reason I posted was because it took so little material that I was surprised.

Originally posted by Mindship
Let me know if/when you get into starship design.

I typically use GURPS: Spaceships to get order of magnitude work for those designs, except that I you the rocket equation to get delta-V.

Is this thread refering to the daft idea of using some of Jupiters mass to build an energy collector around the sun?

Originally posted by Bicnarok
Is this thread refering to the daft idea of using some of Jupiters mass to build an energy collector around the sun?


No, this is a thread about creating a semi-Dyson Sphere through staties built from a future material that is super duper ultra light and super duper ultra strong. Strong enough to support the solar collectors and a "pod" of lots of people. It will have a propulsion system in place and a counterweight, so that it will remain static around the sun to avoid the solar drift problem. It will require far less mass than the moon to accomplish. It's very plausible, actually. We just need to amp up or solar collection efficiency to something closer to 80%, imo.

Edit - Oh yeah, there's also that material that doesn't really exist yet...cept for carbon nano-tubes.

Originally posted by Symmetric Chaos
The FTL drive I'm working with makes gigascale construction feasible for groups that build their own. What sort of FTL?

Originally posted by Mindship
What sort of FTL?

It moves a given volume of mass into the objective frame of reference. This lets me neatly handwave paradox and sound totally smart. Borrowing from the Known Space rules the drive doesn't work deep in a gravity well (though it fails harmlessly rather than destructively), however you can make the drive big enough to envelop a planet if you want at which point the planet's gravity is entirely in the drive field and you can move it FTL. There's a limited number of planets that are far enough from their star for this to work, but it does mean that extreme scale projects are just about practical.

Originally posted by Symmetric Chaos
No, not that. Building a solid shell requires serious superscience and I'm trying to avoid that.

There's also the problem that a solid Dyson sphere is gravitationally neutral and so anything living on the inner surface would just fall towards the star contained in it.

Although this is avoidable through a series of rotating outer and inner spheres.

Originally posted by jaden101
There's also the problem that a solid Dyson sphere is gravitationally neutral and so anything living on the inner surface would just fall towards the star contained in it.

Although this is avoidable through a series of rotating outer and inner spheres.


That's cool.

How do those rotating spheres work, though? The inner one rotates and the outer doesn't? Or, do all the people live on the interior of the outer sphere and the internal is stationary and the people live on the inside of the outer sphere's surface?


And, how does that work? I've never understood how rotating would work on a small scale...but a large scale should work.

Originally posted by jaden101
There's also the problem that a solid Dyson sphere is gravitationally neutral and so anything living on the inner surface would just fall towards the star contained in it.

Although this is avoidable through a series of rotating outer and inner spheres.

That only gets you gravity near the equator and requires materials with ridiculously high binding energy. The amount of energy needed to spin it up is available to the largest powers in the setting but it's really easier to just alter people a bit.

If we cut off the top and bottom of the shell and call it a Niven Ring then we have a mass of 2e27kg (maybe less if we have better materials than Niven). It has to spin at 1.2million m/s to get 1G. A conversion engine would need 10000000000000000000000000 kg (~1.5 Earths) of matter to spin it up to that speed (unless the equations for spinning an object are different than for moving it). A solid shell will take a lot more energy. It's easier to just adapt people to love gravity.

Originally posted by Symmetric Chaos
That only gets you gravity near the equator and requires materials with ridiculously high binding energy. The amount of energy needed to spin it up is available to the largest powers in the setting but it's really easier to just alter people a bit.

If we cut off the top and bottom of the shell and call it a Niven Ring then we have a mass of 2e27kg (maybe less if we have better materials than Niven). It has to spin at 1.2million m/s to get 1G. A conversion engine would need 10000000000000000000000000 kg (~1.5 Earths) of matter to spin it up to that speed (unless the equations for spinning an object are different than for moving it). A solid shell will take a lot more energy. It's easier to just adapt people to love gravity.

For a hollow cylinder, it's m*R^2. I believe.


There's a lot more to that, actually. I don't remember anything else other than a solid being (1/2)m*R^2.

There's actually lots of more stuff that goes along with that...but the simple formulas are easiest to remember.


edit - *google searches*


I found something that might apply:

http://www.vectorsite.net/tpecp_04.html

There's bound to be your answer in there, somewhere. Also, what I found was MOI, so I don't think that that is the answer you were looking for.

I'm looking at what I wrote and I have no idea why I said "alter people to love gravity" it should read "alter people to not need gravity".

My understanding of your link isn't so great but it says:

v_a = v_l / r

v_a = (1.2e6 m/s)/(1.5e11 m)

v_a = 8e-6 seconds

Uh . . . which doesn't make any sense.

Originally posted by Symmetric Chaos
It moves a given volume of mass into the objective frame of reference. This lets me neatly handwave paradox and sound totally smart. Borrowing from the Known Space rules the drive doesn't work deep in a gravity well (though it fails harmlessly rather than destructively), however you can make the drive big enough to envelop a planet if you want at which point the planet's gravity is entirely in the drive field and you can move it FTL. There's a limited number of planets that are far enough from their star for this to work, but it does mean that extreme scale projects are just about practical. Hokey Smokes: you possess a drive powerful enough to move whole planets faster than light!? (The Orion's Arm posse would have conniptions at the very thought). I would think having an FTL drive at all means you could build pretty much whatever kind of Dyson Sphere you want (less handwaving required, IMO). Is this Statite Dyson some sort of futuristic housing project?

(Actually, I do understand your engineering curiosity: I'm just bustin' your chops over what I feel is some inconsistency in tech capability).

Originally posted by Symmetric Chaos
I'm looking at what I wrote and I have no idea why I said "alter people to love gravity" it should read "alter people to not need gravity".

My understanding of your link isn't so great but it says:

v_a = v_l / r

v_a = (1.2e6 m/s)/(1.5e11 m)

v_a = 8e-6 seconds

Uh . . . which doesn't make any sense.

I knew what you meant. I didn't feel it necessary to be a jerk and, apparantly, no one else did, either.


Anywho, I could look in one of my old physics books. I think my first semester physics book covered that in the torque and power chapter. I remember something like what you're trying to calculate, being in there.


I'll check tonight. But, if it starts to take too long, I'm giving up.

Originally posted by Mindship
Hokey Smokes: you possess a drive powerful enough to move whole planets faster than light!?

What, me personally? No.

Of the three groups in the setting capable of making their own drive only two trust the device enough to make regular use of it. The expense of even building a small one is very high, for the most part they have better things to do with their time and energy.

This isn't Star Trek where a drunk with a nuclear missile can go FTL.

Originally posted by Mindship
Is this Statite Dyson some sort of futuristic housing project

No, I set the population as 50 trillion Earth descended, real space, life forms (ie not counting aliens at all or AIs that spend most of their time in VR). The math at the beginning shows that they could all live in the counterweights and never meet one another. And before you ask the setting is X years into the future, where X is a number that gives me the population I want.

It's probably more like the housing for some manner of intelligence or an energy collector for ridiculously high energy research.

Originally posted by Symmetric Chaos
Of the three groups in the setting capable of making their own drive only two trust the device enough to make regular use of it. The expense of even building a small one is very high, for the most part they have better things to do with their time and energy.Y'know, that's a factor I never considered in my own future tech machinations: the cost. Very realistic of you.

This isn't Star Trek where a drunk with a nuclear missile can go FTL.IMO, Glenn Corbitt and his sex cloud > James Cromwell and his bottle, regardless.

Originally posted by dadudemon
No, this is a thread about creating a semi-Dyson Sphere through staties built from a future material that is super duper ultra light and super duper ultra strong. Strong enough to support the solar collectors and a "pod" of lots of people. It will have a propulsion system in place and a counterweight, so that it will remain static around the sun to avoid the solar drift problem. It will require far less mass than the moon to accomplish. It's very plausible, actually. We just need to amp up or solar collection efficiency to something closer to 80%, imo.

Edit - Oh yeah, there's also that material that doesn't really exist yet...cept for carbon nano-tubes.

That sounds pretty amazing, what size & mass does the counter weight have to have

Originally posted by Bicnarok
That sounds pretty amazing, what size & mass does the counter weight have to have

That depends on how big the sail is, how far away the sail is and how bright the star is.

Originally posted by Symmetric Chaos
That depends on how big the sail is, how far away the sail is and how bright the star is.


Sail has a 1500Km radius. It is 1 AU away and the star is about a 5 billion year old G V Class (G2V...see what I did there? teehee).

Ready.....GO!

Isn't there an app for that?