On Sickness, Games, and Dyson Spheres

[elfric]

So, after 3 months of being off work and completely unable to concentrate, my liver tests are back to only mildly alarming and I'm going back to work on Monday. I've been bored out of my skull and have played more RPGs/strategy games in the last three months than I think I have my whole life before that

Comments

[hallerlake]

...if you're moving any reasonable fraction of lightspeed, how do you stay in orbit instead of just shooting off into deep space?

[elfric]

Hmmm, well, I think you found the (in hindsight) obvious flaw in Version 1's configuration. I suspected that the high orbital speed would be a problem.

Escape velocity from the Sun at 1 AU is calculated by the formula

v_e = sqrt(2GM/r)

Where
G is the Universal Gravity Constant (6.67428 x 10^-11 (m^3/(kg * s^2))
M is the mass of the Sun (2 x 10^30 kg)
r is the distance from the Sun (1 AU or 1.49598 x 10^11 m)

Or, 29789.06669 m/s. Interestingly, this is only very slightly more than the orbital velocity of the Earth itself.

Ah well, that explains why I haven't seen that configuration anywhere else. Thanks for the insight, as always :)

[elfric]

Actually, I just remembered one of the rules for stable orbits is that the orbital velocity must be right around the actual escape velocity. Less and the orbit will decay and eventually fall into the sun, more and the gravity of the sun won't be enough to hold the object in orbit.

Obvious in hindsight, I suppose. Ah well, it's always the stupid mistakes that get ya.

[hallerlake]

In double retrospect, you could THEORETICALLY solve this by tethering the orbiting objects. Clearly you can't tether them to the Sun, but if you have a ring of them you could perhaps attach them to the ones across the way (at some angle of offset so the connecting tether doesn't go through the Sun). Picture a multi-headed bola.

But even if that's a reasonable solution, I don't think any plausible materials technology is up to it. You're back to tractor beam handwaving. Also, the failure of any of those attaching tethers would be pretty catastrophic.

Long term viability

[anonymous]

Structures without plate tectonics suffer long term degradation due to erosion.
1. Ocean salinity increases over time without ability to recycle oceanic crust. Also bodies of water fill with sediment.
2. Terrain erodes to flatness. No orogeny.
3. Atmospheric chemical imbalances. Water and sediments scavenge gasses. No volcanoes to put them back into the air.

David Shelley

Re: Long term viability

[elfric]

Ah, good to know, actually. I guess I'll have to figure out a way to emulate plate tectonics also :)

Re: Long term viability

[elfric]

Hmm, actually, I think problem #1 might be solved by the wave pool idea. I'm not really sure what other effects constantly sifting the ocean bottoms would have on marine life or marine geological processes.

Problem 2 might be solvable by brute force. If we have propulsion units capable of moving the cylinder, it should be possible to create internal "earth-moving" plates near the bottom of the layer that could simulate tectonic plate movement and cause terrain perturbation. Probably also expensive in terms of energy usage, but I can't think of a better way off the top of my head.

Problem #3 seems the hardest. With only 1 km of material, there isn't nearly enough weight/pressure near the bottom to convert the sediment into magma. It would have to be solved by applying massive heat to sections of the "crust" to convert it into magma, but I'm not sure that would cause an actual volcano. I don't know enough about geology to have good ideas on this one.

Re: Long term viability

[anonymous]

Wave activity in the ocean is confined to a very thin surface region, perhaps 30 meters at most. Deep oceans have currents, but they are gravity driven (water descends near Greenland and Antarctica and then flows to the deepest points in the Pacific to slowly rise again.) Any wave machine would have no effect on sediments beyond a shallow rim