Small cargo ship

[Halleck]

What's the old saying on Dyson Spheres? "if you can build a Dyson Sphere you don't need it"...

I imagine the same is true with ringworlds. You must assume that the builders have the technology to build a ringworld and not some colony ships instead- heck, even a breeding program would suffice to solve the problem of overpopulation.

[chuck_starchaser]

Dyson spheres, in addition to inherent instability, have the problem that only the equatorial region benefits from any kind of centrifugal force. The north and south poles are just waiting there for the media to show up, ready to fall into the star. Amazing someone like this Dyson guy would be immortalized by having so bad an idea that falls to pieces after a minute of serious thought. Some people got all the luck...

This time I smartened up and started with electrical stuff...



Sorry, not much to show, but those wires took time.

Uhmm... don't worry about them; at 0.3 G's they won't bounce around too much. They are cross connected because a paranoid previous owner thought they might touch the exhaust bell. They aren't critical, anyhow; just for the ionizers.

[Ryder P. Moses]

I believe the idea was that the sphere was a solar sail, rather than a rigid centrifugal structure.

It's a really silly idea anyway, but from a design perspective there was nothing overwhelmingly wrong with it. Which is more than can be said for most 'classic' science fiction 'innovations' like the ansible or positronic brain.

[chuck_starchaser]

Damn!, I realize now, I never read Dyson's original stuff; I just got into arguments with people at the SETI@Home forums, years ago, who described dyson spheres to me as kilometer-thick, made of steel. Yeah, if it was made of a thin material it might be held up by solar wind pressure, I suppose; though it might keep maintenance crews pretty busy patching holes left by comets... Thanks for the info, tho.

[Ryder P. Moses]

I don't know much about them either; I was going on secondhand knowledge there.

[Halleck]

What if you made a ringworld out of flexible material as well? Could it hold together?

If it was flexible enough, it could have an ellipitical orbit, although creatures living on it might be disturbed as it flexes.

[chuck_starchaser]

It would have to be not just flexible but elastic as well... Planets on elyptical orbits move faster when they are closer to the sun, slow down as they get far from it. And the soil, the roads, the buildings, everything would have to be flexible. You could not have seas or oceans, as water would tend to destabilize it and "inflate" one spot.

Next question will be... ...
Can we have the ring divided into individual squares you just jump between, each square following its own orbit?

Answer: Wouldn't work. The most objects you can have stabilized on a same orbit is 3 --one large and 2 small ones at its lagrange points at +/- 30 degrees (L4 and L5, IIRC).
(NOTE: Rings around gas giants might seem like an exception to this rule, but they aren't really; what happens there is each individual ring has little moons on either side helping it stay in shape, and the material within each ring is very lose and pretty slowly but chaotically moving around within the ring's thickness.)

This, by the way, would make it particularly difficult to build the ring in the first place. Even if you had powerful enough jets to stabilize it once built; there's problems during building. You cannot build it by parts; it has to be built pretty much all at once; so after you've loaded several billion kilometer-sized cargo ships with scrith base, and your army of a quadrillion workers are lining up with their shovels on EVA... ... they find that each tiny sub-section of the ring is gravitationally attracted to the the ones on either side, and just a little more material on one side than the other causes the distance to change by a millimeter per day, and accelerating ... closer by 2 mm the next day, added to the 1 mm on the previous day. Not impossible, but it would be quite a stunt to pull; and if it goes wrong, you'll need to order scrith anew.

[Zeog]

A possibly much more important drawback: creatures that live on the inside of such a ring or sphere experience no gravity at all from the ring, no matter how massive it is! It cancels out if the ring is radially symmetric (which it is by construction). They do experience however the stars gravitation and would just fall towards it if they are not themselves on a kepler orbit. In order to stay on the ring it would have to rotate faster then a stable circular kepler orbit would require in order to create artificial gravity.

[Ryder P. Moses]

Zeog: This is not a problem; in fact, it is the whole idea.

[Zeog]

I see, I thought the idea was that solar sail approach. I only remember that StarTrek episode where they discover that Dyson's sphere and there it was static, IIRC. (They have probably that artificial gravity.)
But then, if that ring has to rotate around the star much faster then a body on a kepler orbit with the same radius, what's then the point of discussing whether or not it is stable when moving on a kepler orbit...
Never mind, it doesn't seem to work anyways.

[chuck_starchaser]

Ryder was talking about Dyson spheres when he mentioned solar sails.
Niven's ringworld spinned faster than orbital speed to create artificial gravity; --which is yet another problem for stability, btw... Even if it was flexible AND elastic it would still be unstable (amplify any excentricity and accelerate itself off-center, and soon break to pieces as the side passing closer to the sun gets close enough that the gravitational differential overcomes the structural strength (and it wouldn't take long, no matter how strong "scrith" is...).

[Ryder P. Moses]

That seems like an awkward way to do it. Anything that big with that much structural strength is gonna be pretty damn dense anyway- not neutronium, maybe, but, say, monomolecular carbon. It'll have its own gravity. Build it away from any stars- if you're sufficiently powerful and technically advanced to be building absurdist pointless super-constructs like that you can simulate a sun too.

And will, over the course of eons, implode on itself anyway. That's inevitable. That's what you get for designing a non-spherical planetoid. But you don't need to be stressing the structure any more to get the job done.

[klauss]

Much cheaper would be to have tons and tons of stations (each rotating to provide gravity) connected to an even greater number of solar sail stations, trhough laser energy transfer conduits (a powerful laser wastes energy in the solar sails/collectors, an efficient solar panel receives that energy and converts it back to electricity on the stations).

Plus: you can gradually build such a network.

[Ryder P. Moses]

Ah, here we go.

http://www.nada.kth.se/~asa/dysonFAQ.html

[chuck_starchaser]

Good find!

[chuck_starchaser]

Good find!

Funny where it says...
"Dyson pointed out that so far the energy usage of mankind has increased exponentially for at least a couple of thousand years, and if this continues we will soon consume more energy than the Earth receives from the sun, so the natural step is to build artificial habitats around the sun so that all energy can be used."
We already consume more energy than receive from the sun. About 1000 times more energy per day than plants are able to absorb in a day, anyways, if my source was correct. It's only by tapping the energy stored underground as crude oil, which took millions of years to collect, that we mange to keep the joke going...

[chuck_starchaser]

Moved below...

[Average Earthman]

[quote="chuck_starchaser"]Good find!
We already consume more energy than receive from the sun. About 1000 times more energy per day than plants are able to absorb in a day, anyways, if my source was correct. It's only by tapping the energy stored underground as crude oil, which took millions of years to collect, that we mange to keep the joke going...[/quote]

Uh... your source must be very different to mine. Mine suggests that the total amount of fossil fuel used by humans since the start of civilization is equivalent to less than 30 days of sunshine...

[chuck_starchaser]

I don't believe your figures; but the fact we're using more energy per day than *plants can absorb* is obvious, since we're going quickly through stores of carbon that took about 200 million years to accumulate. By the way, when contradicting someone, it's a matter of basic courtesy to give a source. Total sun radiation is about 1000 watts per square meter at noon, so say 500 watts on average. Area of the earth's disk is 7 million meters, squared is 49 E+12, times pi is about 150 E+12 square meters. Times 500 watts, that's 75 E+15 watts. 75,000 tera-watts. Yeah, that's pretty high.
However, the fact remains plants are on average 0.2% efficient at de-oxidizing carbon, and average land coverage by vegetation is pretty low (count the rain-forests), and landmass is less than 25% of the earth's surface (though there's photosynthesys by plankton in the seas, but less per square meter than on land). I don't know what the figure is for global energy consumption.
Okay, here from the the World Energy Council..
http://www.worldenergy.org/wec-geis/edc/scenario.asp
9 Gtoe in 1990, about 20 Gtoe projected by 2050, so let's say we're at 10 for simplicity. 1 Gtoe (Giga Tonnes Oil Equivalent, per year) so...
1 barrel of oil is 159 litres and packs 5,800,000 btu's.
http://www.uwsp.edu/cnr/wcee/keep/Mod1/ ... tables.htm
1 btu = 2.93 E-4 kw-hr, so 5.8 E+6 x 2.93 E-4 = 17 E+2 = 1700 Kilowatt hours per barrel = 10.7 kilowatt hours per litre. Specific weight for crude oil is about 0.8 so 10.7/0.8 = 13.36 kwhr per kilogram, or 13.36 megawatt-hour per tonne. 10 billion tonnes then packs
10 E9 x 13.36 E6 watt-hours = 133.6 E+15 watt-hours.
There are 8766 hours in a year, so our present global consumption of energy is 133.6 E+15 / 8766 = 15.24 E+12 watts.
75 E+15 watts received / 15 E+12 watts consumed = 5000 times more energy received than consumed.
Okay, 30 days of sunshine times 5000 = 150,000 days of consumption.
That's 410 years at present consumption... Hmm... Maybe my source was about the rate at which earth traps carbon...

Aft section done! Gosh it's hard work doing cables...
First image is a take of the whole ship. The reason is so fish-eye'd is that there seems to be a hard limit on distance for the rendering camera in Blender. I have to put it pretty close or nothing shows.
The front of the ship is at the top; rear at the bottom. All the new work is at the bottom, near the exhaust.







Actually, I forgot to add a couple of support beams for the end of the ladder and start of the scaffolds, as well as a couple of heatsinks; but that's about an hour's work. Then I'm onto the front part. Yey! Haven't finished the mid section, yet, really; got all the electrical stuff to do, plus doubling the pumps and pipes on the bottom side; but I'm too lazy to work on that presently; so the front will be next.

[rockstar]

i guess this work speaks for itself... or is there anything else to add than

[chuck_starchaser]

LOL No, no need to comment; I understand. If this had been someone else's work I'd be out of something to say too. There's really not that much to it, just accumulation of stuff; I'm rendering at maximum quality (16 raytracing samples per pixel, 512 octree resolution) and shadows look good. What I see when I look at it are the shortcomings, though; I started this without a clear plan. The pumps are mounted with screws onto like pieces of wood attached to a flimsy frame in some invisible way. The wiring is all exposed, far more for looks than for realism. The ladder and scaffolds lack support also. But when you throw so much crap together it inevitably ends up looking good because you can't tell one thing from another anymore
If you look at diagrams of real spacecraft and stations, the amount of stuff on them is breathtaking; hopeless to try and be "realistic".
So, the more detail the better; and if you can find references and pictures for each of the details you're adding, chances are it will look better than just random boxes. Right now, for example, I'm doing the cargo doors at the front, and for that I found a drawing of the "international docking hatch" in the Soyuz spacecraft. It consists of a body mounted ring, called the "structural ring", which has an interface seal and 8 latches. Surrounding that ring, there's a "guide ring" that is movable and it's suspended by hydraulic pistons called "attenuators" but they are actually active hydraulics. This guide ring has 3 guide flaps with "capture latches" in them.
Well, no particular reason to copy the model exactly, but it can't hurt, and it saves me the headache of having to come up with ideas for greebles...

[Average Earthman]

Well, I don't think you can safely discount the effect of plankton, there are claims it soaks up up to half of C02 emissions [url]http://www.gdrc.org/oceans/fsheet-02.html[/url]. But anyway, any number we came up with would be a very wild ballpark figure, since nobody really understands plankton. The same can be pretty much said for other ecosystems, come to that.

[chuck_starchaser]

Cargo/docking hatch door taking shape.



Pretty much an exact replica of the Soyuz docking hatch.



Which is actually an international standard for docking compatibility. Here's a pic of the Apollo, with the same docking hatch idea:



The only difference is size: My hatch has an 8-meter diameter opening, 15 meter outer diameter.
Needless to say, once it's done I'll mirror it onto the other end of the front plate.

[Ryder P. Moses]

Doesn't seem very... flexible. Suppose ultimately it depends on the extent and variety of civilization in your mod, but I'd figure there'd be some larger variety of port shapes and sizes (to accomodate bulk cargo, for one thing) that a transport ship would need to have a sort of highly adaptable universal connector for.

[chuck_starchaser]

Well, there are benefits to standardization. I'll assume for now I'll have 3 or 4 standard sizes of the same docking hatch design. But this is a *docking* hatch. There will also be non-docking hatches that you extend a connecting tube to; probably a rectangular one for passengers. As well as air-locks for EVA rather than for boarding. And there will also be non-pressurized hull modules that attach on the sides, whose hatches would be a lot simpler.
And, oh, yeah, no aliens in my mod, just plain old humans