Dyson Sphere

[Sitting Duck]

Hello, I have recently appeared on the Celestia scene and I am highly impressed by the standard of this freeware, good job everybody.
I've been fiddling around with evrything, trying to add a sputnik (which I later discovered did exist already at motherlode) and adding buck rogers to my solar system. I have a rather simple request for an add-on as my anemic attempts at creating anything in 3Dstudio max end miserably. I would like to ask for the creation of a dyson sphere for Sol, appearing sometime in the years from 100000 to 400000, a sphere surrounding the sun at the orbit of venus with an earthlike texture inside, much like in Steven Baxter's novel 'The Time Ships', if anybody could provide this I would be greatly indebted!!!

im not sure if any requests are permitted in this section of the forum, but Im afraid i could find no other appropriate place. Punish me if necessary...

[selden]

You should be able to make a solid Dyson sphere (if that's what you mean) by using the "kit bash" method: combine an existing Addon with a planet.

A 3D sphere that accepts images on its inside is available at
http://www.lepp.cornell.edu/~seb/celest ... d.html#7.2

Make the model's radius to be just slightly smaller than the desired value.
Define a planet that's just slightly larger to be the outside of the Dyson sphere.

A problem with 3D models (the inside) is that the size of the surface texture image is limited by your graphics card, so its resolution won't be the greatest.
Since the outside is a planet, it can be much higher resolution.

Does this help?

[Sitting Duck]

Wow! The efficiency of this forum is astounding! Yes thank you very much this is precisely what i was looking for (solid sphere), do you think people would appreciate something like this as an add-on? Or should I just keep it to myself (if it conforms to a high standard of quality!)

[selden]

I'm sure many people would be glad to use it.

[Sitting Duck]

Im afraid that when my my 3DSmax using friend opened your file, to get a good look, it told him "Improper file format"

[selden]

Please read the Web page.

3DS can't read the files because the surface texture file name field has been edited and its length has been changed. Celestia has no problems reading it, though.

[eburacum45]

Thank you for that sphere which accepts images on its inside;
here is what I have done with it.

Note- you have to use a texture which is 2048x2048; luckily I have been working on one recently.


this is looking past the central star at the far side- you can see the giant continents millions of kilometers across which nevertheless seem small inside such a huge sphere


(edit- weather would be no doubt very strange inside such an object)




and the outside- just a general purpose grid I use;



here is the code;

Code: Select all

"Impossible Dyson" "18 sco"
{
   Mesh "mw-msx.3ds"
   Texture "kiyoshi.*"
   
   Radius 140000998

   EllipticalOrbit {   
      Period            0.0001
      SemiMajorAxis     0.00001
               
   }

   RotationPeriod   200.8
   
   Albedo            0.37
}
"Impossible Dyson" "18 sco"
{
   Texture "grid.*"
BumpMap "gridbump.*"
BumpHeight 0.9
   
   Radius 140002000

   EllipticalOrbit {   
      Period            0.0001
      SemiMajorAxis     0.00001
               
   }

   RotationPeriod   200.8
   
   Albedo            0.37
}


[eburacum45]

Now for the reasons this kind of Dyson won't work in practice.

There is nowhere for reflected light to go, so the star will illuminate the inside of the sphere too brightly, and the whole sky will glow with a luminosity equal to 1/3 the local Sun's brightness if the sphere is 1au in radius; this means the inside of such a sphere will be very warm.
this is not a fatal flaw - to bring the inside surface temperature down you can make the sphere bigger. I think it would have to be several au in radius before the surface becomes temperate- all the better for providing living room. Or you use a smaller star.

Also the sphere would tend to collapse under its own gravity; it either has to be incredibly rigid, or it can be dynamically supported(see below).

But the real clincher is that gravity on such a sphere is towards the star; you would need artificial gravity generators; a technology which does not seem to exist.

There are, however a number of Dyson concepts which might be possible in the real world;
there are examples of each of these in the Orion's Arm Universe add-on if you want them.

1/ Dyson's original idea was a swarm, not a shell; here is one, radiating away the waste heat after the swarm has utilised the star's energy.


a close-up of the swarm elements


A second type of Dyson uses lightweight sails to float on the light pressure from the star; these floating satellites are called statites and can support the weight of photovoltaic cells- these dyson statites are basically an energy collection device



Earlier, I mentioned dynamic support for shells; using rotating particle streams it seems possible to support a ring or a shell at any height above a planet or star.
However the gravity on such a structure is towards the centre, so you live on the outside. Here is one from the OA universe, surrounding a Brown Dwarf; once again it glows slightly as it radiates waste heat from the imprisoned object. You can just see the yellow lines of artificial illumination on the land surface, without which it would be quite dark.


Finally a slice of a dyson sphere is called a Ringworld; here is a small one
around a white dwarf


as the ring rotates, it produces centrifugal 'gravity'.

[Sitting Duck]

In reply to Selden: Sorry!

In reply to eburacum45: Holy Cow! That is precisely what i was looking for, secondly, I do believe in this alternate universe that the sun had undergone some massive changes, as material had been stripped from its surface for the construction of the sphere; the sphere did indeed spin to simulate gravity for organisms near the equator, while the sphere was created out of a highly futuristic 'unknown' combination of materials. Wow!!! Thanks!

[Sitting Duck]

eburacum45, could you please make the Inner and Outer textures for the Impossible Sphere available for download?

[eburacum45]

I'll fix the rather nasty pinch effect on the internal texture before I release it;

I'll have to make up a rationale for this construct as well, as Orion's Arm doesn't use gravity generators...

[Sitting Duck]

ETA final version? Btw, very k00l.

I'm wondering, are you going to keep an approximate 1 AU radius for the sphere?

[eburacum45]

I used the polar coordinates function in Gimp to get rid of the polar pinch; it still has some strange artifacts visible, but it is much better.
Now I suppose I will have to use that function on all the planets I make, and upgrade the ones already made.

It is being uploaded to the Motherlode as I type; the star I have chosen is 18 Scorpii, which is an almost exact clone of our Sun. The radius is just less than one astronomical unit.

[Sitting Duck]

Has it become part of the package of the complete Orion's Arm?

[eburacum45]

No; we have to wait now for it to appear on the Motherlode as a separate item. This can be a slow process, but of course the Motherlode is run by volunteers. I would like to help them out myself but the OA site takes up most of my internet time...

[Sitting Duck]

Interesting...I'd like to thank you once more for taking the time to get this sphere up and running, it will be a pleasure to have in my universe.

Im assuming by "slow" you mean weekly or bi-weekly, monthly at the most?

[Sitting Duck]

Excellent work!! This is exactly what I was looking for, I love the 80000 degrees K touch!

[eburacum45]

Thanks; if anyone else wants it, the Impossible dyson is available here
http://www.celestiamotherlode.net/catal ... onsarm.php

[NoXion]

Oh goodie! I've been waiting so long for a decent Dyson Sphere addon.

My universe does use gravity generators on the other hand

[Blaydewind]

Hi all, this is my first post, and in my own proper tradition, I've got to stir up an anthill

1. If a Dyson Sphere had enough mass to collapse in on itself, wouldn't it also have enough mass to have its own gravity twards the outside of the sphere from the inside?

2. Although I do agree that any such structure would have to be dynamically supported, what form would that support take?

3. If gravity in a system is always twards the star in any given system, (referencing my first point) how come I havn't fallen into the sun?