Dyson Sphere (shell) - Dysonica Anyone?

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

I wonder what protections you'd need from meteors....

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Yeah, that's fine if you're doing artificial gravity. Personally, rotation is a cheap way to produce it. Instead of a sphere, how about a partial sphere with the pole areas shaved off? That would allow for spacecraft access from two directions. Gravity would get weird near the edges, but rugged mountains would keep all but the most adventurous inhabitants out of areas of reduced gravity.

 

Matt "Too-practical" Frisbee

 

It would be weird. A ring would be better than a donut though - such as Niven's Ringworld. The Spill Mountains acted as both the silt redistributer for the various waterways, and the border to keep the atmosphere in.

[Narratio]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Good math Megaplayboy' date=' but that's with a perfectly smooth inside. A dyson sphere would have mountains, lakes, rivers, deserts, oceahs, and so on. So how much of that 28 quad is actually liveable?[/quote']

 

As a Dyson sphere is built, not randomly generated, the answer would be 'All of it'. Mountains take up bugger all space in reality and cannot be that tall due to point load limitations, atmosphere blanket etc. Oceans are not deep (mass of water compared to sphere wall thickness) and are there purely for fish farming and sport activities. Rivers are directed for heat exchange and sport activities. Deserts are hard to keep desertified unless you deliberately do not include subsurface irrigation, heat exchange nutrient processing etc.

 

You've built a complete biosphere after all. So why make a world with areas where your species cannot live? It's not a safe practice.

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

They would have to take pains not to have any megascale terrain features - but great diversity. Otherwise you would get niche races evolving (ie mermaids, or races that live their entire lives on a mountain slope and what have you) . Much like the hominids did in Ringworld because there were no other animals to fill those niches.

[Nyrath]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

let's see, surface area of a sphere = 4 pi * radius^2, right?

 

so, (1.5x 10^8 km)^2 *12.5(roughly)=2.8 x 10^16 sq km, or 28 quadrillion square km. divide by 10 billion people, that's 2.8 million sq km per person, or about a million square miles each.

 

That's a lot of lawn to mow.

 

No kidding.

 

The Earth has approximately 150,000,000 square kilometers of land area. This means that Dyson sphere has the same approximate land area as an interstellar empire composed of 190,000,000 earthlike planets.

[Publius]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

I have the same problem with these as I do with Ringworld. Too darned big. Way way too darned big in this case, since it makes the Ring look small by comparison.

[John Desmarais]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

I have the same problem with these as I do with Ringworld. Too darned big. Way way too darned big in this case' date=' since it makes the Ring look small by comparison.[/quote']

 

No problem. Want to use one in a game but don't like the HUGE surface area? No problem - break it. Declare, for whatever reason works for you, that most of the surface area has been rendered unfit to live in (ie. the sphere is extremely old an has suffered many "Fist of God" type asteroid/meteorioid strikes leaving most of the surface area incapable of hold sufficient atmosphere to support life.)

[Nyrath]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

No problem. Want to use one in a game but don't like the HUGE surface area? No problem - break it. Declare' date=' for whatever reason works for you, that most of the surface area has been rendered unfit to live in[/quote']

Alternatively, perhaps the Dyson sphere never completed construction. Perhaps only an area of a couple of Earth surfaces was coated with fertile topsoil, and the rest is billions and billions of square kilometers of barren un-farm able unlivable bare metal.

[austenandrews]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Alternatively' date=' perhaps the Dyson sphere never completed construction. Perhaps only an area of a couple of Earth surfaces was coated with fertile topsoil, and the rest is billions and billions of square kilometers of barren un-farm able unlivable bare metal.[/quote']

Or the inhabitable sections are hundreds of thousands of miles apart. Or Earth-like environments are not the only environments reproduced on the surface.

[megaplayboy]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Well, since the original idea behind the DS was to have a structure that would capture all of the radiant energy of a star, one could logically expect huge sections of it to consist of solar collectors and energy conversion stations, for powering whatever geewhiz level tech exists on the DS.

[austenandrews]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Well' date=' since the original idea behind the DS was to have a structure that would capture all of the radiant energy of a star, one could logically expect huge sections of it to consist of solar collectors and energy conversion stations, for powering whatever geewhiz level tech exists on the DS.[/quote']

I kinda like the idea that it requires DS-level power to enable FTL.

 

Of course if you have orbiting "shadow plates" to simulate night cycles, the plates themselves become perfect solar collectors (or half-perfect, as it were).

[Cancer]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Of course if you have orbiting "shadow plates" to simulate night cycles' date=' the plates themselves become perfect solar collectors (or half-perfect, as it were).[/quote']

 

To mimic real night, though, those shadow plates have to occupy half the solid angle around the star. And they have to be in active powered flight, not orbit, unless you are OK with a Mercury-like light/dark cycle time (that is, 50 or so RL Earth days between "sunrises" rather than 24 hours). An orbit with a period of 24 hours around a solar mass object has a radius of 1/51 AU, about 4.2 solar radii. The plates will heat up to about 2900 K at that distance ... so they'll be glowing a nice red rather than the Sun's yellow-white.

[austenandrews]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

To mimic real night' date=' though, those shadow plates have to occupy half the solid angle around the star. And they have to be in active powered flight, not orbit, unless you are OK with a Mercury-like light/dark cycle time (that is, 50 or so RL Earth days between "sunrises" rather than 24 hours). An orbit with a period of 24 hours around a solar mass object has a radius of 1/51 AU, about 4.2 solar radii. The plates will heat up to about 2900 K at that distance ... so they'll be glowing a nice red rather than the Sun's yellow-white.[/quote']

But it shouldn't matter how fast the plates are orbiting, right? What matters is that they produce 12 hours of darkness and 12 hours of light in sequence (or whatever day cycle you want). You just have to make sure that the orbital period is a multiple of 24 hours.

 

Unless I'm missing something..?

[Cancer]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Yeah, you're right. And if you let the inhabited sphere and the shadow plates rotate/revolve in opposite directions, it gets easier.

 

The one goofy thing is that you need multiple subarrays of plates, with different orbital distances, with different orbital inclinations. Without the varying inclinations, the areas at the poles of the plate array don't get shadow. Without the varying orbital distances, items at different inclinations will collide sooner or later. Even then I think it'll be real hard to have a regular light/dark cycle...

[austenandrews]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

I imagine some enormous shifting moire pattern calculated to deliver various periods to various areas. Or something.

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

With the level of technology required to build the Dyson Sphere in the first place, I would imagine the builders would have no difficulty modifying the life forms inhabiting it to require no cycle of night.

[Mentor]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

It gets us back to the actual campaign itself, then. Are the PCs part of the still functioning society that built the sphere or the unsophisticated descendents surviving on the structure now running automatically? Is FTL impossible making the world and local space the only real gaming melieu?

 

I like the idea of having an "all of the above" for possible habitats. In fact the scale involved leaves plenty of room for absolute diversity as well as huge areas of relative homogeneity and regions nearly impassible between them.

 

Anything conceivable can be done on a 1AU Dyson Sphere.

[Cancer]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

I've toyed with the idea of an inverted Dyson sphere, with the people, atmosphere, etc. on the outside, and three stars orbiting the sphere at intervals to enable periods of day and night. If you made the thickness of the sphere about 1/3 the radius of the Earth, and the density comparable, it could have a comparable gravitational field at the surface.

 

Of course, depending on how large it's scaled, you could have a population larger than most galaxies...

 

Minor quibble: that does work out to about 1.5 solar masses of stuff. There's certainly less than about 100 Earth masses or so of Earth-composition stuff outside of the Sun in the Solar System. 1 solar mass is about 333,000 Earth masses. So building that sphere requires harvesting many thousands of star systems, or dismantling and processing a couple of hundred stars (because Earth-composition matter is only a couple of percent of solar-composition matter).

 

Galactus is a miserable little worm compared to that. "Cosmic-powered" supers are beneath the notice of anything which can marshal those resources. Cthulhu, Azathoth, and the entire ensemble of Old Entities are bush league compared to that.

 

I'm uncomfortable with a Dyson sphere in a game-world simply because I cannot imagine what entities capable of building such a thing would be like. I can't imagine why'd they be gone, or what they'd think of us if they weren't gone. I'd need to answer those before I'd go forward. Call me imagination-impaired, but there it is.

[Capt JT Kohonez]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Minor quibble: that does work out to about 1.5 solar masses of stuff. There's certainly less than about 100 Earth masses or so of Earth-composition stuff outside of the Sun in the Solar System. 1 solar mass is about 333,000 Earth masses. So building that sphere requires harvesting many thousands of star systems, or dismantling and processing a couple of hundred stars (because Earth-composition matter is only a couple of percent of solar-composition matter).

 

Galactus is a miserable little worm compared to that. "Cosmic-powered" supers are beneath the notice of anything which can marshal those resources. Cthulhu, Azathoth, and the entire ensemble of Old Entities are bush league compared to that.

 

I'm uncomfortable with a Dyson sphere in a game-world simply because I cannot imagine what entities capable of building such a thing would be like. I can't imagine why'd they be gone, or what they'd think of us if they weren't gone. I'd need to answer those before I'd go forward. Call me imagination-impaired, but there it is.

 

Ooof! that is a scary thought!!

 

But it'd make a helluva Sci-fi/Fantasy campaign!!

Doncha think???!!

[tgrandjean]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

'Actually had a few thoughts on running in a broken sphere. Set the campaign immediately after whatever happens to shatter the sphere. Now you have over 1 bil earth sized chunks of shell orbiting around a star and whatever population survives the immediate impact looking to get away. 'Would even be great for a relic hunters game.

[Play4Keeps]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

However, with a "hollow" spheroid, if the thickness of the shell is constant no matter the radius from the center, the gravitational pull at the surface will be constant as well.

 

Nope.

 

Get your favorite spreadsheet program out and do the following.

 

In cell A1 put "1000" (without the quotes)

In cell A2 put "=A1+100" (without the quotes)

In cell B1 and B2 put "100" (without the quotes)

in cell C1 put "=((4/3)*PI()*A1^3)-((4/3)*PI()*(A1-B1)^3)" (without the quotes)

Do a "copy down" from C1 to C2

In cell D1 put "=C1/(A1^2)" (without the quotes)

Do a "copy down" from D1 to D2

Do a "copy down" from (A2 thru D2), to oh say row 200.

 

Look at the results in column D. See how they keep going up? That's the relative surface gravity.

 

I didn't do this in any particular units, but the math is right. If you want to put it in kilometers, metric tons, Earth gravities, and all that, you can figure out the "fudge factor". I can't be hedgehogged. Important thing is that the surface gravity does keep going up.

[megaplayboy]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Nope.

 

Get your favorite spreadsheet program out and do the following.

 

In cell A1 put "1000" (without the quotes)

In cell A2 put "=A1+100" (without the quotes)

In cell B1 and B2 put "100" (without the quotes)

in cell C1 put "=((4/3)*PI()*A1^3)-((4/3)*PI()*(A1-B1)^3)" (without the quotes)

Do a "copy down" from C1 to C2

In cell D1 put "=C1/(A1^2)" (without the quotes)

Do a "copy down" from D1 to D2

Do a "copy down" from (A2 thru D2), to oh say row 200.

 

Look at the results in column D. See how they keep going up? That's the relative surface gravity.

 

I didn't do this in any particular units, but the math is right. If you want to put it in kilometers, metric tons, Earth gravities, and all that, you can figure out the "fudge factor". I can't be hedgehogged. Important thing is that the surface gravity does keep going up.

 

1)gravitational pull is an inverse square function of radius from center of mass.

2) mass of a hollow sphere of non-variable thickness t is also a square function, increasing with the radius of the sphere.

 

Let's plug in a radius of 150 million km for the outer shell, and 149.9987 million km for the inner shell. Volume is the volume of the larger shell minus the volume of the inner shell.

 

Raw estimated volume for this(mine) is 150 million^2, times 4 pi, times 1300 km.

14137166941154069573081895.224758

-14136799377999165315240965.523582

 

367563154904257840929.70117(1st method volume result)

367566340470005808900.1292758437(2nd method volume result)

 

16336.140217967015152431163111111(volume divided by radius squared)

 

So, mine comes out slightly higher for volume. Volume times density yields mass. Since the volume of the shell will remain fairly close to a mirror of the square function, and the gravity will decrease as an inverse square function, the range of the gravitation attraction will stay pretty steady, once the thickness/radius ratio is small enough(say, 1/1000, or higher). I should have qualified my statement. I'll plug in 10 million, 10 billion and 10 trillion km later to check my numbers.

 

okay, for 1 trillion km:

your method:

1633628179654320820627000000000

 

my method:

1633628179866692484000574559305.3

 

 

16336.28179654320820627(volume divided by radius squared)

 

It looks like the increase in surface gravity will be negligible.

[Nyrath]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

I'm uncomfortable with a Dyson sphere in a game-world simply because I cannot imagine what entities capable of building such a thing would be like. I can't imagine why'd they be gone' date=' or what they'd think of us if they weren't gone.[/quote']

What makes you think that they are gone?

 

Imagine that the human race are all one-celled creatures living in a drop of stagnant pond water, and the Dyson sphere builders are human beings.

 

The amoebas wonder where the Dyson sphere builders have gone, and what they'd think of amoebas if they were not gone. The answer is that the humans are not gone, they are just so huge and comic that they are basically invisible to amoeba-kind. As far as communication goes, an amoeba has a tiny chance of communicating with one of the Human's white blood corpuscles, but no chance at all of talking to the human.

 

Paul Hughes proposes a corollary to Clarke's Third Law: Any sufficiently advanced intelligence is indistinguishable from nature.

http://www.futurehi.net/archives/000106.html

 

http://www.projectrho.com/rocket/rocket3aa.html

(scroll down to "As far as technological advancement goes, there is a crude measure in the Kardashev scale.")

[Curufea]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Is a Dyson Sphere less believable that Faster Than Light travel? Does it break the level of fantasy that is acceptable in your game?

(ie usual acceptable fantasy include FTL, hyperspace, artificial gravity, psionics, force fields etc)

 

If you have a Sphere, you need not have FTL.

[megaplayboy]

Re: Dyson Sphere (shell) - Dysonica Anyone?

 

Is a Dyson Sphere less believable that Faster Than Light travel? Does it break the level of fantasy that is acceptable in your game?

(ie usual acceptable fantasy include FTL, hyperspace, artificial gravity, psionics, force fields etc)

 

If you have a Sphere, you need not have FTL.

 

Well, in the real world currently, the energy required for FTL travel is infinite, while the energy required for a DS, while vast, is not.