Masers

[MrUniverse]

I've read a lot about space based solar power, and I've been wondering why none of the proposals suggest using masers (microwave lasers) to beam the power to the surface. It seems to me that the collecting area on Earth wouldn't have to be nearly as large. Sure, the beam would be more concentrated and might hurt some birds, but seems like a reasonable trade-off. Birds get chopped up in wind turbines and fish get killed on underwater turbines all the time.

My idea of a space power station would be to send up and inflate gigantic, metallic-coated Mylar balloons to geosynchronous orbit that are transparent on their sun-facing side so that the suns rays focus on solar cell type collector in the center and send the energy down via maser to a rectenna on the planet.

NASA has already sent enormous inflatable balloons into obit like Echo I (30.5 meters) and Echo II (41.1 meters).

Is this a workable idea?

http://en.wikipedia.org/wiki/Echo_1

 

[Boris_Badenov]

It looks like a good idea to me. I'd really like to see someone put a pathfinder mission together, It's just launch costs are too high for any of the big boys to take the risk. In time, as launch costs come down, we could very well see some demonstrators flying.

 

[scottb50]

It looks like a good idea to me. I'd really like to see someone put a pathfinder mission together, It's just launch costs are too high for any of the big boys to take the risk. In time, as launch costs come down, we could very well see some demonstrators flying.

The biggest problem I see is even in Geocentic orbit sunlight is blocked for a time every day. Another is the loss sending the energy to the surface, it seems it would be a lot simpler to improve ground based Solar collection capabilities.

Basically you are moving the collectors to orbit and transmitting their production to the surface. What advantage is there?

 

[MrUniverse]

IIRC, because of the the tilt of Earth's axis, a body in geosynchronous orbit is only in Earth's shadow for a few hours a year. You get practically uninterrupted sunshine for the life of the satellite.
Also, a big advantage to space based solar power is that you can collect solar energy which is normally blocked by the Earth's atmosphere (a few hundred percent more). Sure there will be transmission losses from beaming it to the surface, but losses are minimized by transmitting the energy in microwave form (I believe 2.45 gigahertz is optimal) which readily passes through Earth's atmosphere.

Once more, my main reason for the post was to inquire why masers are not the mode of choice for transmission in space based power schemes. Is it because it would be so concentrated as to kill birds that fly through; I say who cares about a few unfortunate sparrows. We need a real solution to the energy crisis. Besides, we could save more wildlife by utilizing carbon-free sustainable energy than by the alternative.

 

[Mee_n_Mac]

Once more, my main reason for the post was to inquire why masers are not the mode of choice for transmission in space based power schemes. Is it because it would be so concentrated as to kill birds that fly through; I say who cares about a few unfortunate sparrows. We need a real solution to the energy crisis. Besides, we could save more wildlife by utilizing carbon-free sustainable energy than by the alternative.

I don't know what schemes have been proposed for getting the power back to Earth other than they're usually microwave based. I'd first investigate the conversion efficiencies of the competing technologies. If a TWT is 65% then a MASER needs to beat that or come close and have some other advantage (ie - weight or output power).

 

[neilsox]

Mee-n-Mac is likely correct. In 60 years of electronics, I know of zero applications for high or medium power masers. Apparently masers are less efficient, more costly, less reliable and/or not suitable for high power. Over 100 million one kilowatt magnetrons have given good service in microwave ovens which operate on 2.45 megahertz. Higher frequencies are better for small and medium scale SSP = space solar power as the transmitting antenna and receiving rectenna are smaller, and thus less costly.
The atmosphere is moderately transparent at 860 nanometers = near infrared light, and half watt lasers are available. 2 million of them would be required for a million watts and each may require separate optics. Phase lock of two million laser diodes, is difficult, but may soon be practical and cost effective. If the current economic recession ends soon, a demonstration SSP will likely fly before 2012, but megawatt plus SSP await a sharp reduction in the cost of getting to geostationary orbit. A solar synchronous orbit has some advantages including supplying occasional power to all the countries of Earth, but hundreds of receiving sites would be needed. Not so bad for the laser diodes as ordinary solar sites can receive the beam from the satellite. There are lots of details at the forum at www.spacesolarpower.wordpress.com Neil