# Mirror Rotate Around O'Neil Colony?

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#### CAllenDoudna

##### Guest
When I read "The High Frontier" by Gerard K. O'Neil back in the 1980s, well, maybe I missed something--no degree and didn't study engineering, you understand--but it seemed to me those mirrors he had hanging out like banana peals hinged at one end and let out by cables at the other, would be bent in a curve by the stress of centrifugal force. (That's based on my trying to walk from the center to the outside and back of playground merry-go-rounds.) If so bent they would not be able to reflect sunlight through the windows to the valleys below.

Well the knowledgable engineers on this Forum were able to effectively destroy my solution of having one valley and one window in a cylinder big enough so that one rotation every 24 hours would yield Earth-normal gravity by at last answering a question I have asked for quite a few years now: To get Earth-normal gravity by having one rotation every 24 hours you would need a cylinder about four times the size of the Moon's orbit around Earth. Clearly that size is impractical.

But that still leaves the original problem of the mirrors warping from the stress of centrifugal force.

So the other day I came up with a new idea: What about if instead of three separate mirrors attatched to each of the three windows we had one big parabollic mirror that would not be attached at all to the cylinder but would instead float along in the same orbit and the cylinder would rotate at the center? Perhaps "parabollic mirror" is the wrong term. Perhaps what we want is a large ring mirror, cut the big end off a cone if you will.

That alone would probably take care of the problem, but perhaps if the mirror slowly rotated around the cylinder every 24 hours it would give us a day-night cycle also.

Is any or all of this doable or anyway what's the right track?

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#### neutrino78x

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hmm I'm having some trouble visualizing that. I don't have a degree either...but isn't it true that there is no, or very little, rotation at the hub of the ring?

I always think of a space station with artificial gravity looking more like the Stanford Torus than an o'neil cylinder. That is what is shown in 2001 A Space Odyssey.

--Brian

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#### neutrino78x

##### Guest
Actually in that wikipedia article it seems to show the mirror floating separately from the ring. I dunno, I always pictured it being attached.

--Brian

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#### AsimovFan

##### Guest
I think this is the best approach to that problem.

We will have several stations whose jobs are to beam solar energy
to any station that requires it, this solar energy will supply power
to the habitat and charge its batteries, this same power will be used
to power lighting that will be used for farming and general lighting.

Trying to create an artificial sun might not be the most efficient way
to use the sun. IMO.

Also we will be able to produce energy without solar energy.
We will collect hydrogen and ice harvested from space with collectors.
These will be the main source for power and materials.
The collector ships will be in synchronous orbits with the stations, there
will be many ships and many types of ships in synchronous orbits.
The main habitat will be made from asteroids and moons, possibly
dwarf planets. They will be either hollowed out and converted or
broken down into particle dust. Combined with laser energy and ice
particles, we can fabricate the entire ship this way. We can make it
so its entirely protected from the dangers of space. along the center
ring will be made clear, or possibly magnified, this way we can see out.

I have been posting about this subject for almost a week under
"Who needs Goldilocks"

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#### neutrino78x

##### Guest
AsimovFan":jy84wxch said:
I think this is the best approach to that problem.

We will have several stations whose jobs are to beam solar energy
to any station that requires it, this solar energy will supply power
to the habitat and charge its batteries, this same power will be used
to power lighting that will be used for farming and general lighting.
Farming needs huge amounts of light, though. I think you would use the mirror to direct the Sun's natural light into your farming area.

--Brian

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#### AsimovFan

##### Guest
One thing I notice absent from discussion is the use of gravity forces
to generate power.

Heres a page that has a few uses of them
http://www.daviddarling.info/encycloped ... ether.html
Plus there are tons of articles about them.

Using the gravitational forces of the moon and the earth, and even
other bodies to harness large amounts of inertia will be a major way
to procure power for all sorts of uses.

Stations set in close orbit around the sun will be charged and beam either
laser energy or microwave energy to any station, if there isn't enough,
then more stations will be built until our space industry is supplied.

Building a large farming ring in space orbiting the sun will probably be
the best first starting place, this ring can be cylindrical and sunlight can
be filtered and beamed into it from the ends. Reflective mirrors can be
built to orbit the habitats. Large magnifying structures can also be built.

Eventually we would be able to magnify the starlight and focus it into
a type of solar tube, to be used for lighting, maybe more.

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#### CAllenDoudna

##### Guest
neutrino78x":1qt9pdxl said:
hmm I'm having some trouble visualizing that. I don't have a degree either...but isn't it true that there is no, or very little, rotation at the hub of the ring?

I always think of a space station with artificial gravity looking more like the Stanford Torus than an o'neil cylinder. That is what is shown in 2001 A Space Odyssey.

--Brian
Here you go. Broaden your horrizons:

http://settlement.arc.nasa.gov/70sArt/art.html

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#### CAllenDoudna

##### Guest
Upon further reflection, I think this might work better:

Wecould have two opposite-facing mirrors attached end-to-end like an hour glass and these could slide back-and-forth to reflect into the Colony 12 hours of daylight and 12 hours of nightime stars in a stable, apparantly non-rotating sky. This back-and-forth slide could be done with rockets which will need servicing and re-fueling or with electromagnetic attraction.

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#### neilsox

##### Guest
I can't picture any of these mirror ideas, but that does not mean they are impossible or even impractical. The 2001 craft was in low Jupiter orbit which is likely longer period than LEO = low earth orbit = less than two hours. In solar orbit, the period is likely a year or more. LED lighting is very efficient and can likely provide adequate light levels at less cost than mirrors and giant windows. Neil

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#### neutrino78x

##### Guest
Well, the mirrors are for agriculture. Providing adequate light to grow plants requires a lot of energy. Granted, you have a lot of energy through solar power in orbit, but it would probably still be more efficient to have a mirror to reflect sunlight into your agricultural areas.

I guess the question is, can you build something transparent that will let in light, but not cosmic rays etc., into your agricultural area?

--Brian

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#### CAllenDoudna

##### Guest
neilsox":1l041yh1 said:
I can't picture any of these mirror ideas, but that does not mean they are impossible or even impractical. The 2001 craft was in low Jupiter orbit which is likely longer period than LEO = low earth orbit = less than two hours. In solar orbit, the period is likely a year or more. LED lighting is very efficient and can likely provide adequate light levels at less cost than mirrors and giant windows. Neil
Here are some pictures; they might help:

http://settlement.arc.nasa.gov/70sArt/art.html

The project was simply too big to grasp back in the 1970s and Senator William Proxmire summed up the mood of Congress: "I say not one penny for this nutty fantacy!" NASA then became a program without a mission and the Shuttle became a road to nowhere. But there is enough material in the Asteroid Belt to create such habitats with a living area 3,000 times the land area of Earth and about a hundred times that if we got our building material from Mercury.

Had we proceeded in the 1970s it would have been fantastically expenssive (though with the Arab Oil Embargo fresh in everybody's mind it was calculated they could pay for themselves by building Solar Power Satellites). We could have completed the first Island I habitats by about 1995 (pop. 10,000) and by 2000 switched to the larger Island IIs (pop. 50,000?). By now we would be beginning the Island III cylinders that could hold a couple hundred thousand or more. As is, we'll probably start building these in the 2020s as travel to LEO and the Moon becomes routine and by 2050 there will be a tidal wave of settlers pouring into space with an unchecked (and uncheckable) flow of wagon trains to any place in the Solar System offering building material the settlers could turn into such habitats.

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#### neilsox

##### Guest
Generally I did not agree with Senator Proxmire, but he may have been correct on this one. I suspect materials still don't exist which can hold 14 pounds per square inch of atmosphere in a cylinder 10 kilometers in diameter and 20 kilometers long (inside dimensions) Worse the cylinder likely cannot produce enough food for 50,000 people. Glass a kilometer thick is nearly opaque, unless impurities are held to parts per billion which is still very costly. If we can get enough light inside for effective agriculture, lots of infrared will come in also which will over heat the cylinder to unbearable without a gigaton of air conditioning which requires several thousand gigawatts of electricity. The suggested 12 hours of darkness alternating with light makes the cost much higher, or much reduces the light available for photosynthesis. Perhaps the colonist can live on mushrooms which require no light :lol: Neil

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