Solar power satellites -- How Bright Would They Look & What Orbit Would They Follow?

Question

There is an Op-ed piece in the NY Times today advocating solar power satellites. I fired off a letter to the editor disagreeing based on the expense, but mainly because of the deleterious effect on astronomy world-wide - since these would have to be big arrays, much bigger than the ISS, they would subtend a large angle in the sky and be correspondingly bright. But now I am curious - how bright? I'm guessing perhaps magnitudes brighter than Venus, but how bad would it get? And, would they be in geosynchronous orbits, LEO, or what? If geo-synch, they'd sort of be messing up the night sky from dusk 'till dawn, right?

Answer 1

I agree with you and innocent victim that it's a bad idea.  There's actually a lot of stuff we could try here on Earth if we were properly motivated (like reflecting unused sunlight back into space).

Answer 2

I googled the piece to see what you up in arms about, http://www.nytimes.com/2008/07/23/opinio...

IMHO you are confused about what is being described. First in this article they are proposing using solar arrays in space  to collect solar radiation and convert it into an electromagnetic form that can be beamed to receiving stations on the earth. They are not proposing using giant mirrors to beam sunlight to the earth to collect, so there would be no appreciable difference in the brightness of the night. There would be occasional flashes of the the sunlight off of the collection panels in the same manner as the ISS and Iridium flares work now. This would be brief sparkles as the sun glances off the bottom of the panels or from the top when they are at an oblique angle.

While this technology is possible to day, it is not very probable in the near future due to initial costs of construction and launching the system, especially in light of the current economic state of the US.

If you are not sure what satellite flashes look like check out Heavens-Above.com for when large satellites (or the ISS) pass over your area. They are quite beautiful, often very bright (when I watched the ISS pass over head in June it was -4 or -5 magnitude for just a few minutes), but short lived, and small in size.

Answer 3

That's far from the only problem they'd cause, and also far from the worst. Collecting solar energy in space and beaming it to Earth would only add to an already severe global warming problem. Whatever form the energy would come to Earth as (probably microwaves), it would eventually become thermal energy. This could only increase the rate of warming. The ONLY solution to the energy problem, ultimately, is solar energy, collected at the Earth's surface, where it would have ended up anyway. Fossil fuels add heat and greenhouse gases to the atmosphere. Fission, and if we ever develop it, fusion, add some heat directly, and the energy they produce also degrades into more heat.

Wind energy comes from the sun, so is not a problem in itself, but the windmills adversely affect bird populations, add noise, and are unsightly. Hydro energy also comes from the sun via the water cycle we all learned about in school, but damming rivers to produce hydro causes other problems as well.

It is confidently predicted that, within only twenty years, photovoltaics will be cheap, durable, and efficient enough to easily take care of all of our energy needs for the foreseeable future. I vote that we wait for them, and in the meantime, reduce consumption by requiring that auto, truck, and bus makers build more efficient vehicles, and requiring homebuilders to start installing geothermal home heating and cooling systems wherever possible. We've already taken a major step in conservation by getting rid of incandescent lighting. Taking these other steps would get us through this period of crisis, to the time when energy is plentiful and virtually free of cost.

Now, I'd like to ask you to write another letter to the Times, incorporating these thoughts. I'm not a subscriber, so I didn't see the article you mentioned, or I'd do it myself.