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Author Topic:   World Building Techs

warg posted 11-26-98 02:23 AM ET
I'm reviving a thread from the old Sci&Tech foroum. This is to discuse everything from Space Colonies to Terraforming to Ring Worlds and Dyson Spheres. I just read about and idea in Blue Mars. It involved hollowing out asteroids in the Asteroid Belt and spining them to creat artifical gavity. These are some of my thoughts about it:
At about 2AU or 186 million miles(300 kilometers) from the Sun, enough light could still be provided for farming if mirrors we used.
A relitivly small Asterois, say the size of Phobos(about 25x10x10) could even be fitted with some sort of engine and brought in closer to the Sun.
What does everyone think of this?
Gord McLeod posted 11-26-98 02:27 AM ET
I just recently finished reading that book myself, and I found the idea rather claustrophobic, but it has a sort of wild appeal to it... I'm not sure I'd care for the low gravity conditions though.
Firehawk posted 11-26-98 04:15 PM ET
Yeah! Dyson Spheres are back! My topic! Ok. Dyson Spheres were first proposed by Freeman Dyson, in (not sure) the 19th century. He calculated that if you used all the mass in the Sol system, besides Sol itself, you could build a one-mile-thick hollow sphere around Sol with a radius equal to the Terra-Sol distance. People could live on the inner surface of the Sphere, and the available surface area would be so incomprehensibly immense that we would never have population overcrowding problems again (well, never is a very long time, but.)
And for my modifications. Using the masses of Eurytion, Chiron, Nessus, Pholus, and 53% of the mass of Hercules (the rest could be ejected out of the system), you could make a one-mile-thick hollow sphere around Alpha Prime at Earth radius, and another at Mercury radius. The time frame I'm thinking of here is maybe around 2500. If you've read Kim Stanley Robinson's Blue Mars and seen what our engineering capabilities will be by 2200 (and the Mars series is very accurate, IMO), 2500 sounds like a reasonable accurate date; by then we should be able to move star sized masses around and be able to convert one form of matter to another by rearranging the quanta in matter. Anyway, one half of the inner sphere will absorb all forms of EM radiation, converting it to electricity via radiphotoelectric cells (i.e. photoelectric cells that work on other wavelengths than visible; they exists today already). The other half will be transparent to visible and infrared light and absorb and convert all other forms of EM radiation (to electricity). The inner sphere will slowly rotate, and the outer sphere will rotate faster. Now, we have a diurnal cycle, protection against solar radiation, virtually unlimited electricity (excess can be ejected out of the sphere through evenly distributed release valves on the outer surface of the outer sphere), virtually unlimited living space, and artificial gravity. And an atmosphere will be able to be contained between the two spheres. The spheres will stay in place; because of inertia, they will not move unless an outside force acts on them, and what force would do that? In case they got knocked out of alignment, however, the EMR release valves on the outer surface of the outer sphere could be adjusted to release more EMR on one side of the sphere, therefore pushing it back into alignment. Photons do have mass when they are moving.
Whew! ::pins on "Ask me about Dyson Spheres" button:: Gotta go now. Please, someone try to find a hole in my plan.
Tripod posted 11-26-98 08:13 PM ET
There's a old Star Trek The Next Generation with that spere, and the special apperance was the old irish engineer scotty.
Kurn posted 11-26-98 08:20 PM ET
I remember that episode. I'm still not sure if this Freeman Dyson is real or just a figment of some writers imagination
Firehawk posted 11-26-98 09:19 PM ET
Yeah I remember that episode too. As for Freeman Dyson, I don't know, I heard that from...I think Spoe.
OmniDude posted 11-27-98 07:33 AM ET
Kurn & FireHawk: The result of 2 minutes on Yahoo
http://spot.colorado.edu/~gamow/george/1991bio1.html
Goddamn, you people are lazy.
Anyway, Dyson spheres are a mindnoumbing concept. And as someone said in the old forums, by the time mankind can manipulate matter with the ease that is required to construct dyson spheres, I don't think room for living will be a problem since FTL travel must be mastered by then and the whole universe will subsequently be our playground. It just won't be economically feasible.
On a more theoretical notice, aren't we seriously underestimating the energy produced by a star? I imagine the space inside a DS being heated up to intolerable temperatures, causing the sphere to blow up like a balloon (or at least crack). Yes, you could make vents, but they would have to be HUUUGE!!!( say a thousand with a diameter like that of Jupiter. The DS would look like a hockeyball)
Oh, and another old objection: how do you prevent the DS from wobbling like a freshly made soapbubble due to the inherent irregularity of solar flare activity? Hmm, maybe you wouldn't have to. At these dimensions, noone on the DS would probably notice)
Firehawk posted 11-27-98 04:02 PM ET
Read the Mars series and you will understand. Extragalaxial, even extrasolar travel will lag behind our engineering capacity (at least if Robinson is right, and he is my sci-fi god so I'm assuming he is.) In 2200 we are only starting to launch an extrasolar colonization ship, and our engineering capacity has advanced to where we are wrapping a giant coil like an armature around the whole planet of Mercury (?) to slow its rotation. And population overflow is still an immense problem; the main problem.
And remember heat is EM radiation, infrared. Even today we have thermophotoelectric cells (photoelectric cells that work on infrared wavelengths.) By 2500 of course we will have TPE cells that will be able to withstand the star's heat from a Mercury distance, and they will convert most of the star's heat into electricity which will be dissipated into the ether (what I call the cosmic medium.)
Solar flare activity is irregular, but it averages out so the spheres will stay in position (and adjusting the aforementioned EMR dissipation will keep it still, if needed.) Anyway, the spheres have a combined mass on star level (over half that of Hercules) so solar radiation would not be strong enough to budge them. Solar radiation doesn't even budge the earth, which has a mass a fiftieth of the spheres (er...volume. I'm assuming all matter has the same density, which it doesn't, but it doesn't matter.)
Firehawk posted 11-27-98 04:05 PM ET
Alas, now that I'm a Member again and my favorite topic has resurfaced, I have to leave the boards. I'm getting a long-overdue new computer (P90 to PII450) and there will be a lot of downtime. I don't know when I'll be back, if even before the demo comes out. So goodbye everyone! Email me at [email protected]!
warg posted 11-27-98 04:54 PM ET
Ok, 2 things:
First, aren't we SERIOUSLY underestemating the size of a Dyson's Sphere??? THIS THING IS SO BIG THAT(with gavity of some kindTHE ATOMSPHERE WOLUD ONLY EXTEND OUT ABOUT A FEW HUNDRED MILES! As for the heat, it wuld be spread out over 1.08686394x10 to the power of 17 square miles! Any extra heat could be vented into space or used to make electricity, ect.
Second, I read some more about these asteroids in Blue Mars last night. A very bright, large light would be hung in the middle(dont know how) and the light and gavity could be adjusted to be light Earth or Mars(terraformed). They would kinda be like little Dyson's Spheres.
GreatNate posted 12-17-98 03:16 AM ET
Never read Blue Mars due to the ergerious science errors in Red Mars. Anyway, in Re: the asteroid, there is one problem. A hollow asteroid being spun fast enough to get a full 9.8m/s^2 pseudogravity is subject to tremedous tension in it's outer hull.
It would need extensive reenforcement to keep from flying apart into several chunks. And after you wrap the whole thing up like a christmas turkey with carbon fiber, one has to wonder what the point of hollowing out a rock is? Why not simply make a from-scratch habitat, and save a lot of time and trouble.
Kirel posted 12-17-98 03:43 PM ET
Dyson spheres?
Why???
(Aside from the fact that humanity has always done silly things.)(Thank you Tolls.)
Energy production,agriculture,living space?
No,I don't buy that.
Consider the effort of building the thing.(And don't give me that nanite **** again,because I don't believe in the idea anyway.)
Terraforming ought to be so much easier.
And as for energy,some solar panels in orbit around the sun should do the job nicely.
Thank you.
Kirel
warg posted 12-17-98 05:41 PM ET
Ok, does ANYONE know the formula for the rate of spin of an object to produce a given gravity???
Octopus posted 12-18-98 12:24 AM ET
I believe what I'm about to post is correct, but I don't have a physics book handy to check these, so I may be wrong. If anybody knows better, please correct me.
The formula you are looking for is:
acceleration = (angular velocity)^2 * radius
Angular velocity should be measured in radians per time unit (and is usually represented by a lower case omega, which looks like a curvier w). There are 2*pi radians in a complete circle. If your rotational speed is 1 rpm (rev. per minute) then your angular velocity is 2*pi/60 radians per second.
warg posted 12-18-98 01:29 AM ET
Where does the gavity come in though???
Octopus posted 12-18-98 01:57 AM ET
The acceleration in the equation is the simulated gravity effect. If the acceleration were 9.8 m/s^2, it would feel just like gravity feels to you on Earth. If you want 1/2 g, set acceleration to 4.9 m/s^2, etc.
Example:
Suppose the UNS Unity is a cylinder with a radius of 100 meters, and we want to simulate earth-normal gravity at the outer hull.
9.8m/s^2 = w^2 * 100m
w^2 = (9.8m/s^2) / (100 m)
w^2 = 0.098
w = sqrt(0.098) = 0.313 radians/second
w = 3 revolutions per minute.
(assuming my formula's correct, and I plugged the numbers in properly)
Fluke posted 12-18-98 02:06 AM ET
Gravity is acceleration. You spin the sphere and it accelerates towards the center. You press the other way.
Dyson sphere doesn't really work since your entire atmosphere would be sucked into the sun at both ends of the axis where there's no artificial gravity.
Octopus posted 12-18-98 02:22 AM ET
Okay, I just did a little experiment in my kitchen. Using the same formula, with a 1 meter radius (approx. length of an arm), you need to get one revolution every two seconds to maintain a 9.8 m/s^2 acceleration. By approximating that rotation, you can swing a glass of water over your head and the water stays in the glass (you are moving the glass as fast as gravity would pull the water down, so the water doesn't fall out at the top of the circle). It's hard to keep a smooth circular motion with your arm, but it looks like my formula is at least close. I'm really bored .
Octopus posted 12-18-98 02:34 AM ET
Fluke, I don't think that's right. I thing that the atmosphere would be denser at the equator and thin out to nothingness at the poles. There's no reason the air would flow "uphill" to the poles and "leak out". There's nowhere for it to leak out to, it's a closed system.
Why is everybody trying to live on the inside of the sphere? Why not just live on the outside, and use real gravity?
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Author	Topic: World Building Techs
warg	posted 11-26-98 02:23 AM ET I'm reviving a thread from the old Sci&Tech foroum. This is to discuse everything from Space Colonies to Terraforming to Ring Worlds and Dyson Spheres. I just read about and idea in Blue Mars. It involved hollowing out asteroids in the Asteroid Belt and spining them to creat artifical gavity. These are some of my thoughts about it: At about 2AU or 186 million miles(300 kilometers) from the Sun, enough light could still be provided for farming if mirrors we used. A relitivly small Asterois, say the size of Phobos(about 25x10x10) could even be fitted with some sort of engine and brought in closer to the Sun. What does everyone think of this?
Gord McLeod	posted 11-26-98 02:27 AM ET I just recently finished reading that book myself, and I found the idea rather claustrophobic, but it has a sort of wild appeal to it... I'm not sure I'd care for the low gravity conditions though.
Firehawk	posted 11-26-98 04:15 PM ET Yeah! Dyson Spheres are back! My topic! Ok. Dyson Spheres were first proposed by Freeman Dyson, in (not sure) the 19th century. He calculated that if you used all the mass in the Sol system, besides Sol itself, you could build a one-mile-thick hollow sphere around Sol with a radius equal to the Terra-Sol distance. People could live on the inner surface of the Sphere, and the available surface area would be so incomprehensibly immense that we would never have population overcrowding problems again (well, never is a very long time, but.) And for my modifications. Using the masses of Eurytion, Chiron, Nessus, Pholus, and 53% of the mass of Hercules (the rest could be ejected out of the system), you could make a one-mile-thick hollow sphere around Alpha Prime at Earth radius, and another at Mercury radius. The time frame I'm thinking of here is maybe around 2500. If you've read Kim Stanley Robinson's Blue Mars and seen what our engineering capabilities will be by 2200 (and the Mars series is very accurate, IMO), 2500 sounds like a reasonable accurate date; by then we should be able to move star sized masses around and be able to convert one form of matter to another by rearranging the quanta in matter. Anyway, one half of the inner sphere will absorb all forms of EM radiation, converting it to electricity via radiphotoelectric cells (i.e. photoelectric cells that work on other wavelengths than visible; they exists today already). The other half will be transparent to visible and infrared light and absorb and convert all other forms of EM radiation (to electricity). The inner sphere will slowly rotate, and the outer sphere will rotate faster. Now, we have a diurnal cycle, protection against solar radiation, virtually unlimited electricity (excess can be ejected out of the sphere through evenly distributed release valves on the outer surface of the outer sphere), virtually unlimited living space, and artificial gravity. And an atmosphere will be able to be contained between the two spheres. The spheres will stay in place; because of inertia, they will not move unless an outside force acts on them, and what force would do that? In case they got knocked out of alignment, however, the EMR release valves on the outer surface of the outer sphere could be adjusted to release more EMR on one side of the sphere, therefore pushing it back into alignment. Photons do have mass when they are moving. Whew! ::pins on "Ask me about Dyson Spheres" button:: Gotta go now. Please, someone try to find a hole in my plan.
Tripod	posted 11-26-98 08:13 PM ET There's a old Star Trek The Next Generation with that spere, and the special apperance was the old irish engineer scotty.
Kurn	posted 11-26-98 08:20 PM ET I remember that episode. I'm still not sure if this Freeman Dyson is real or just a figment of some writers imagination
Firehawk	posted 11-26-98 09:19 PM ET Yeah I remember that episode too. As for Freeman Dyson, I don't know, I heard that from...I think Spoe.
OmniDude	posted 11-27-98 07:33 AM ET Kurn & FireHawk: The result of 2 minutes on Yahoo http://spot.colorado.edu/~gamow/george/1991bio1.html Goddamn, you people are lazy. Anyway, Dyson spheres are a mindnoumbing concept. And as someone said in the old forums, by the time mankind can manipulate matter with the ease that is required to construct dyson spheres, I don't think room for living will be a problem since FTL travel must be mastered by then and the whole universe will subsequently be our playground. It just won't be economically feasible. On a more theoretical notice, aren't we seriously underestimating the energy produced by a star? I imagine the space inside a DS being heated up to intolerable temperatures, causing the sphere to blow up like a balloon (or at least crack). Yes, you could make vents, but they would have to be HUUUGE!!!( say a thousand with a diameter like that of Jupiter. The DS would look like a hockeyball) Oh, and another old objection: how do you prevent the DS from wobbling like a freshly made soapbubble due to the inherent irregularity of solar flare activity? Hmm, maybe you wouldn't have to. At these dimensions, noone on the DS would probably notice)
Firehawk	posted 11-27-98 04:02 PM ET Read the Mars series and you will understand. Extragalaxial, even extrasolar travel will lag behind our engineering capacity (at least if Robinson is right, and he is my sci-fi god so I'm assuming he is.) In 2200 we are only starting to launch an extrasolar colonization ship, and our engineering capacity has advanced to where we are wrapping a giant coil like an armature around the whole planet of Mercury (?) to slow its rotation. And population overflow is still an immense problem; the main problem. And remember heat is EM radiation, infrared. Even today we have thermophotoelectric cells (photoelectric cells that work on infrared wavelengths.) By 2500 of course we will have TPE cells that will be able to withstand the star's heat from a Mercury distance, and they will convert most of the star's heat into electricity which will be dissipated into the ether (what I call the cosmic medium.) Solar flare activity is irregular, but it averages out so the spheres will stay in position (and adjusting the aforementioned EMR dissipation will keep it still, if needed.) Anyway, the spheres have a combined mass on star level (over half that of Hercules) so solar radiation would not be strong enough to budge them. Solar radiation doesn't even budge the earth, which has a mass a fiftieth of the spheres (er...volume. I'm assuming all matter has the same density, which it doesn't, but it doesn't matter.)
Firehawk	posted 11-27-98 04:05 PM ET Alas, now that I'm a Member again and my favorite topic has resurfaced, I have to leave the boards. I'm getting a long-overdue new computer (P90 to PII450) and there will be a lot of downtime. I don't know when I'll be back, if even before the demo comes out. So goodbye everyone! Email me at [email protected]!
warg	posted 11-27-98 04:54 PM ET Ok, 2 things: First, aren't we SERIOUSLY underestemating the size of a Dyson's Sphere??? THIS THING IS SO BIG THAT(with gavity of some kindTHE ATOMSPHERE WOLUD ONLY EXTEND OUT ABOUT A FEW HUNDRED MILES! As for the heat, it wuld be spread out over 1.08686394x10 to the power of 17 square miles! Any extra heat could be vented into space or used to make electricity, ect. Second, I read some more about these asteroids in Blue Mars last night. A very bright, large light would be hung in the middle(dont know how) and the light and gavity could be adjusted to be light Earth or Mars(terraformed). They would kinda be like little Dyson's Spheres.
GreatNate	posted 12-17-98 03:16 AM ET Never read Blue Mars due to the ergerious science errors in Red Mars. Anyway, in Re: the asteroid, there is one problem. A hollow asteroid being spun fast enough to get a full 9.8m/s^2 pseudogravity is subject to tremedous tension in it's outer hull. It would need extensive reenforcement to keep from flying apart into several chunks. And after you wrap the whole thing up like a christmas turkey with carbon fiber, one has to wonder what the point of hollowing out a rock is? Why not simply make a from-scratch habitat, and save a lot of time and trouble.
Kirel	posted 12-17-98 03:43 PM ET Dyson spheres? Why??? (Aside from the fact that humanity has always done silly things.)(Thank you Tolls.) Energy production,agriculture,living space? No,I don't buy that. Consider the effort of building the thing.(And don't give me that nanite **** again,because I don't believe in the idea anyway.) Terraforming ought to be so much easier. And as for energy,some solar panels in orbit around the sun should do the job nicely. Thank you. Kirel
warg	posted 12-17-98 05:41 PM ET Ok, does ANYONE know the formula for the rate of spin of an object to produce a given gravity???
Octopus	posted 12-18-98 12:24 AM ET I believe what I'm about to post is correct, but I don't have a physics book handy to check these, so I may be wrong. If anybody knows better, please correct me. The formula you are looking for is: acceleration = (angular velocity)^2 * radius Angular velocity should be measured in radians per time unit (and is usually represented by a lower case omega, which looks like a curvier w). There are 2pi radians in a complete circle. If your rotational speed is 1 rpm (rev. per minute) then your angular velocity is 2pi/60 radians per second.
warg	posted 12-18-98 01:29 AM ET Where does the gavity come in though???
Octopus	posted 12-18-98 01:57 AM ET The acceleration in the equation is the simulated gravity effect. If the acceleration were 9.8 m/s^2, it would feel just like gravity feels to you on Earth. If you want 1/2 g, set acceleration to 4.9 m/s^2, etc. Example: Suppose the UNS Unity is a cylinder with a radius of 100 meters, and we want to simulate earth-normal gravity at the outer hull. 9.8m/s^2 = w^2 * 100m w^2 = (9.8m/s^2) / (100 m) w^2 = 0.098 w = sqrt(0.098) = 0.313 radians/second w = 3 revolutions per minute. (assuming my formula's correct, and I plugged the numbers in properly)
Fluke	posted 12-18-98 02:06 AM ET Gravity is acceleration. You spin the sphere and it accelerates towards the center. You press the other way. Dyson sphere doesn't really work since your entire atmosphere would be sucked into the sun at both ends of the axis where there's no artificial gravity.
Octopus	posted 12-18-98 02:22 AM ET Okay, I just did a little experiment in my kitchen. Using the same formula, with a 1 meter radius (approx. length of an arm), you need to get one revolution every two seconds to maintain a 9.8 m/s^2 acceleration. By approximating that rotation, you can swing a glass of water over your head and the water stays in the glass (you are moving the glass as fast as gravity would pull the water down, so the water doesn't fall out at the top of the circle). It's hard to keep a smooth circular motion with your arm, but it looks like my formula is at least close. I'm really bored .
Octopus	posted 12-18-98 02:34 AM ET Fluke, I don't think that's right. I thing that the atmosphere would be denser at the equator and thin out to nothingness at the poles. There's no reason the air would flow "uphill" to the poles and "leak out". There's nowhere for it to leak out to, it's a closed system. Why is everybody trying to live on the inside of the sphere? Why not just live on the outside, and use real gravity?