4
$\begingroup$

I am struggling to picture what placement of artificial lighting I should use for my O'Neill cylinder design for the daylight hours, a strip light along the centre of the cylinder would obstruct the view of above scenery and take up space and any other designs I can think of wouldn't provide even light over the whole area?

So other than a long strip light down the centre, how can I provide enough daylight for a warm sunny climate capable of growing plants and crops in an enclosed cylinder?

$\endgroup$
  • 3
    $\begingroup$ If you can build an O'Niell cylinder, you can probably figure out how to build a light whose I(θ) (that is, intensity as a function of angle relative to the spot "axis") gets you "close enough" to even illumination in e.g. a Rama lights setup. (Worst case, you put a cover on it with variable translucency.) Atmospheric diffusion, given that the lights are as far away as they can be within a cross-section will also help with evenness. $\endgroup$ – Matthew Dec 30 '19 at 19:41
  • $\begingroup$ @Matthew the Rama set up is interesting, do they have any problems with things on ground level not being able to be close to the lights because of the heat? $\endgroup$ – user69935 Dec 30 '19 at 20:09
  • 1
    $\begingroup$ IIRC, no, but also I think the lights weren't "directly" exposed, but were "under" panels. OTOH, it's possible Clarke didn't think about that. That said, if you have superconductors to use as heat sinks, or maybe even just really good cooling, my guess is you'd be okay. You probably want to keep people away from direct contact with the lights anyway, if nothing else to stop them from scratching or smudging them unnecessarily. (Standing directly on them while they're lit is almost certainly contraindicated.) $\endgroup$ – Matthew Dec 30 '19 at 20:19
  • 1
    $\begingroup$ As an addendum to the previous comment, maybe the waste heat from the lights is how you heat the air in your cylinder... $\endgroup$ – Matthew Dec 30 '19 at 20:20
  • 1
    $\begingroup$ @Matthew the original idea was even light of growing quality everywhere, in a way that landscape, garden and if someone wished to have a plant pot on the window sill could have the same quality light as farming but it is something I may wave for certain areas for visibility. $\endgroup$ – user69935 Dec 30 '19 at 22:05
6
$\begingroup$

First off... I don't think I buy the "but the power!" argument. Aside from atmospheric absorption (which isn't that significant), photons are going to keep until they hit something. Thus, as long as you are emitting most of your light in a useful direction, it doesn't matter how far away the light is from the "ground" if your goal is for more-or-less even illumination. Moreover, if your cylinder is mostly growing things (which seems likely), the percentage of "cropland" to areas that don't need to be lit is probably high. So, while you could save some by not lighting things like roofs, this may not be significant or worth the headaches of having thousands of lighting elements versus only a few.

As far as view obstruction... I'm not sure this can be solved. The light has to come from somewhere, and that "somewhere" is going to produce light that is more intense than what you get from diffusion. Looking in the direction of the light source will thus probably be contraindicated, no matter where it is. A central light will be a bit like a sun, and yes, you won't be able to look directly past it. However, many low-level lights might make the entire sky too bright to look at, unless you are above the lights.

So... all that said, I think you have four choices that come down to a number of trade-offs:

Central light

Pros: Reduced maintenance due to use of a single element. Nearly 100% of light does useful work (i.e. you don't need reflectors to minimize inefficiency). Similar to having a sun that is always at equatorial noon.

Cons: Single point of failure. Blocks view of exact opposite of cylinder.

A better design might be to have a shaft through the center of the cylinder that is surrounded by lights. I can think of all sorts of interesting uses for such a shaft. This would add the need for reflectors, but you'd still have 180° or more of useful light.

Rama-style lights

Pros: Reduced maintenance due to use of a few (three or six, depending if you have a central ring sea) elements. Center of ring is unobstructed.

Cons: Optimal light arcs are 60° or 120°, and not sure what will happen in regions of overlap; may require "interesting" design to achieve balanced illumination. Looking directly at lights is probably contraindicated, but probably no worse than central light scenario.

For day/night, you can dim and turn off the whole system, however, it might be interesting to dim the lights in a cycle, though you probably won't get a terribly dark "night" this way.

"Parking lot" lights

Pros: Many individual elements can fail with minimal effect on the overall system. Can localize light where needed.

Cons: Massive number of individual elements to be maintained. Landing flying craft is going to be a problem. Looking up may not be possible except in areas that are above¹ the lights. If you want tall trees, your lights have to be equally high.

(¹ Yes, you can have a ground-level area isolated from the lights, but by the time you build those walls, which will limit visibility, you might as well just put a deck on top of them and be above the lights.)

Diffuse light

Pros: Sky is probably quite hazy, but otherwise can look anywhere. Possibly self-maintaining.

Cons: Almost certainly requires heavy hand-waving. No clear shadows, ever (like an overcast day). Unclear if opposite side of cylinder is even visible.

The idea here is that the entire inside of your cylinder is full of tiny light emitters... enough that the source of light is sufficiently diffuse to avoid any source that is too bright to look towards. You could achieve this effect with a central light surrounded by enough diffusive material, but this becomes an exercise in maximizing drawbacks. Alternatively, you could have floating swarms of micro-lights.


And now, here's an idea out of left field... have multiple layers to your cylinder. Have all the plants and animals on a lower/outer level with all the lights on the "ceiling" (made of glass or something that lets light through), and all the human stuff "above" (with only local lighting, or just use what reflects from the lower level). In the lower/outer level, you can't look up, but the plants and animals won't care. In the upper/inner level you can definitely look anywhere.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Great, thanks for all the good suggestions. $\endgroup$ – user69935 Dec 30 '19 at 19:12
  • 1
    $\begingroup$ @JRams For another example of the "central light along axis", take a look at The Book of the Long Sun tetralogy. There was a "sunshade" running more or less the length of the axis, covering several degrees' worth of the light. As the shade rotated around the "long sun", the lands underneath experienced their local nighttime. $\endgroup$ – Ti Strga Dec 30 '19 at 21:47
  • 2
    $\begingroup$ Shellworlds aren't a new concept, so you've got some conceptual ground to work on there. $\endgroup$ – Draco18s no longer trusts SE Dec 30 '19 at 23:14
  • $\begingroup$ @Draco18snolongertrustsSE it was the cylinder design I was really looking forward to designing and drawing first but shellworlds are likely something I will think about later also. $\endgroup$ – user69935 Dec 31 '19 at 0:15
3
$\begingroup$

Besides blocking the view of the other side of the cylinder, the other issue with a central light source is the sheer power it would require. Do the math -- inverse law (not inverse square, because a linear lamp as long as the area to be lit effectively doesn't spread in the length dimension), with the amount of area you want to light, and the intensity you want (for plant growth, at least, about twenty times brighter than common office illumination), times the efficiency of your light source in terms of actual light per kilowatt.

You'll likely find you'd need a fusion power plant just to run the center light strip.

Far more efficient would be to put small light strips (or pole lights, like modern parking lot or street lights) just above building height -- lighting the same surface at the same intensity won't require much if any less total power, but the ability to leave areas "less lit" (like building roofs) would save significantly. And there would be less blockage of the view of the inside of the cylinder -- in fact, "dark parks" where one could look up unobstructed might be part of the design.

Of course, these lights would dim or a fraction completely shut off for night.

| improve this answer | |
$\endgroup$
  • $\begingroup$ From a ground level view point, how much of the above and rest of the cylinder could be viewed in daylight times do you think? $\endgroup$ – user69935 Dec 30 '19 at 14:23
  • $\begingroup$ It would be much like looking up between streetlights, at a street lit night cityscape. $\endgroup$ – Zeiss Ikon Dec 30 '19 at 14:25
  • $\begingroup$ would it not be stronger or hazier? ive seen grow lamps and their pretty strong and blinding compared to regular lighting. $\endgroup$ – user69935 Dec 30 '19 at 14:27
  • 2
    $\begingroup$ Yes, the lighting would (have to) be brighter than common street lighting, to grow plants -- but for humans, it need be no brighter than common office lighting, which is about 1% of direct sunlight at Earth's distance. Therefore, cities might well be kept dimmer than farmland, and dimmer still at night. $\endgroup$ – Zeiss Ikon Dec 30 '19 at 14:45
  • 1
    $\begingroup$ It's still dimmer than Earth summer daylight, by about a factor of 5, so looking up between the lights would give little impression of what's beyond -- the lights would be brighter than the background, so unless there's a lot of space between, you couldn't see much. $\endgroup$ – Zeiss Ikon Dec 30 '19 at 14:53
3
$\begingroup$

Sun Chariot

This is a variation of the central light source. Since the central axis will be a zero G zone with very low atmospheric pressure, we don't actually need much structural support for our light engine. Think a long power-line along which our sun/light bulb can pull itself along like a cable car. We could even add coolant pipes should we need them. The cable won't be visible for most in most cases, especially if we use carbon nanotubes power lines and paint the thing appropriately.

The big advantage would of cause be the redundancy such a system can have. You can either have several cables or simply install a new one in case maintenance or replacement is required. You can obviously have several sun chariots. One small issue, or rather novelty, would be that you would either have to transport the chariot back to the "sunrise side" at night or have sunrise and sunset alternate sides on a daily basis.

Another advantage is that this moving lightsource brings more dynamics into the ecosystem. All the static lights will create permanent light and shadow zones. This is of cause fine and dandy if you are into mould and eternal shadow as well as ever scorching and endless light, but I actually think that moving light and shadow would be more interesting.

Power requirements depend on the area of the habitat. For this rough estimate I'm going to assume we're dealing with Island Three (r = 4 km, l = 32 km, A = 804 km^2) and want to mimic the maximum normal surface irradiance at sea level of 1000 W/m2. I'll ignore the albedo of the interior of the drum, which would reduce the light we need. Furthermore I don't believe that this figure is accurate, because a lot of the light hitting earth is infrared light. Plants actually don't need most of the suns light. Look up grow lights in case you are interested. You could and probably want to cut out most of the infrared light, as heat management will be an issue anyways.

That said, you'll need a 804 Megawatt lamp to light the place. This is a lot of energy. An average nuclear powerplant produces 1 Gigawatt. This means that given a non 100% efficiency we'll probably need one of these or its equivalent in fusion, solar or beamed power. Assuming we use 10000 watt lamps, which aren't that much more powerful than the 39 7000 watt lamps powering the the Luxor Light in Las Vegas. Assuming we need one square meter per lamp a spherical lamp would have a radius of 80 m. We could of cause go for a "pill shape" trading radius for length. Using several lamps at the same time might be an interesting option as well, especially if one has settled a binary star system.

| improve this answer | |
$\endgroup$
  • $\begingroup$ really interesting idea, thanks $\endgroup$ – user69935 Dec 31 '19 at 14:37
  • $\begingroup$ I had just accepted an answer before you posted this, but this idea is really making me think plus it would look really cool. $\endgroup$ – user69935 Dec 31 '19 at 14:39
  • $\begingroup$ I mostly like this, but it has the drawback that the ends of the cylinder are lit differently from the middle. While this is true to some extent with any "big light" system, this would seem to make it more pronounced. Maybe this can be mitigated by having several "suns" that focus their light in a relatively narrow band. (You could also run the lights on "low" when moving them back at night for a simulated "moon".) $\endgroup$ – Matthew Dec 31 '19 at 15:56
2
$\begingroup$

If your cylinder can be transparent, you could have exterior mirror arrays reflecting star light around the interior. There could be transparent sections or "belts" in the cylinder wall, or the caps could be transparent - or both. The mirror arrays would allow to modulate the amount of light over the inside of the cylinder, allowing for a diurnal cycle and even seasons.

| improve this answer | |
$\endgroup$
  • $\begingroup$ I wanted this particular structure to be off in interstellar space at times so I chose the closed cylinder to maximise habitat space also, the type you suggested I will probably use for Dyson swarms. $\endgroup$ – user69935 Dec 30 '19 at 19:11
2
$\begingroup$

Poles everywhere, similar to what you see with road lights, equipped with artificial solar spectrum lamps and powered according to the artificial day time you want to enforce.

| improve this answer | |
$\endgroup$
  • $\begingroup$ wont that be to harsh on peoples eyes? unless u mean pretty tall poles which again may take up space and obstruct above views, but I did want night street lighting similar to what we have now so it is an option. $\endgroup$ – user69935 Dec 30 '19 at 12:49
  • 1
    $\begingroup$ Solar lamps? They are supposed to magically power themselves? $\endgroup$ – Matthew Dec 30 '19 at 19:05
  • 1
    $\begingroup$ @Matthew, solar lamps is how lightbulbs having the same emission spectrum of our sun are commercialized in some countries $\endgroup$ – L.Dutch - Reinstate Monica Dec 30 '19 at 19:39
  • 1
    $\begingroup$ Ah... I was reading that as "solar powered". (It doesn't help that Wikipedia shares my confusion.) I think "full spectrum light" or even "artificial sunlight lamp" would be less confusing. $\endgroup$ – Matthew Dec 30 '19 at 19:50
2
$\begingroup$

You can sacrifice even lighting to get a better view of the ground above, with spotlights on the ground pointing only at the farms opposite them.

If you're standing on farmland, you see one blindingly bright light above you, shining like the sun.

If you stand anywhere else, you can look up without being blinded, and your world is lit by the gently glowing constellation of farms above you. If the habitat is more than 5% farmland, then the "dark" areas will be lit up brighter than your office. More than 10% farmland and they'll be brighter than a cloudy day.

| improve this answer | |
$\endgroup$
  • $\begingroup$ "constellation of farms" quite a beautiful idea. $\endgroup$ – user69935 Dec 30 '19 at 21:57

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy