Lunar Lasers

Two different articles about building lasers (well, lasers and a maser perhaps) on the moon. Reuters has a story about a potential lunar power plant, creating electricity with solar panels and beaming it to Earth with microwaves. Space.com has a piece about building a sort of super-sized Star Wars program on the Moon, giant lasers set up to blast incoming space debris and not, of course, anyone here on Earth.

Comments

Re:Why bother?

[Anonymous Coward]

And why is this news for nerds?

Yeah, only jocks discuss lasers on the moon. Us nerds should stick to talking about football and women and beer.

If they don't bite, lower the price...

[ObligatoryUserName]

The solar power plant on the moon idea has been around for quite a while, but the last time I heard of it, the estimated cost was more than a trillion dollars (I seem to recall it being closer to 2 trillion dollars). Even though it cost so much, the scientist (I can't remember who it was, so it might be the same guy) said it could make back all its costs in under a year by selling power to everyone on Earth at a rate that was lower than what we would pay otherwise.

What I'm curious to know is has the cost of space missions gone down so much since then that it can now be done for the $59 billion listed in the article, rather than the >$1 trillion number cited a number of years ago, or is there some new trick (sure sounds the same), or is this guy just making up a lower number so that people will actually listen to him? Anyone out there heard of this Prof. Criswell before? I'd really like to believe that this is a viable option.

Re:Microwave

[mbessey]

Microwaves are easy to recieve - you simply stretch out a wire between two insulated poles, and the power just flows. That's the big advantage of microwaves over other power transmission possibilities.

Granted, given the spill-over from the "concentrated" beam of microwaves, you'll probably have to use some frequency that's not very popular for communication, but it's probably do-able.

The people who are worried about power-line emissions would probably go insane over this, though - the exposure levels would be MUCH higher.

-Mark

I've got an even better idea

[SIGFPE]

Why not spend $50,000,000,000 on solar panels for use on Earth. This proposal has a number of cool features:

1. You don't have to send lots of equipment up to the moon
   
2. You don't have the hassle of building microwave transmitters and receivers to transmit the energy to the Earth
   
3. They couldn't easily be hijacked to make a nasty weapon
   
4. The equipment would be easy to service. You wouldn't need regular flights carrying crews to the moon.
   

Two dumb ideas

[markmoss]

If you are going to do this beamed microwave thing, build it in Earth orbit, closer to the target. (distance)*(wavelength)= k*(diameter of transmitter aperture)*(diameter of beam at target), where k is a constant somewhere between 1/3 and 3. I think the moon is about 250,000 miles or 400,000 km away. So to focus a 30GHz (1 centimeter wavelength) microwave beam down to a 10 km spot on Earth takes an antenna about 400m across. Or in units the average American understands, a football-field sized antenna would put most, but not all, of the transmitted energy into a 10 mile wide spot. This whole area would have to be blanketed with receiving antennas (expensive!). And people living 20 miles away would be measuring the leaking energy and suing every time they got a cough. (Birds would be safely building nests on the antennas, but American trial lawyers never let science get in the way of a deep-pockets lawsuit.)

The best place for a solar power satellite is probably geosynchronous orbit (40,000 km). This needs a football-field sized transmitter and a mile-wide receiver; still pretty big, but maybe manageable. And the transmitter and receiver don't move relatively. A lunar array would have to keep switching between different receivers as the Earth turns. An SPS in a lower orbit would also have to keep switching receivers, but at least it would have smaller antennas.

A solar plant in orbit is in sunlight almost all the time (depending on distance from earth and orbital particulars, it might spend a few hours a year in earth-shadow). On the moon, two weeks out of every four is night.

The laser installation would also work better in a medium-height earth orbit, where it's solar panels were powered all the time and it was much closer to the targets. At least, I assume that it isn't meteroids headed for the moon that this is supposed to shoot down?

Re:This is a weapon of massless destruction

[Fenris2001]

Answers to safety questions -

1. Focus - the beam will most likely be a maser, or microwave laser. Given a reasonable size emitter in geosynch or elliptic earth orbit, the footprint on the surface of the planet is only a few kilometers wide, and has an energy density of perhaps ten to a hundred watts per square meter.

2. Guidance - the same way they keep aircraft away from anything else - tell them not to go there. Note that this isn't really a problem, as the metal skin of an aircraft would deflect the beam.

3. Of course they will coordinate with other satellite operators. Although, if some satellite DID accidentally cross the beam path, it wouldn't necessarily be harmed, for the same reasons as 2.

The proposals I've seen for this (including a gov't study in the Sixties), all addressed the safety question. The REAL question is whether or not this can be done ECONOMICALLY - it's no use if the power so produced is ten times more expensive than fossil fuels (though note that such a scheme becomes more attractive as fossil fuels become more expensive...). The most attractive source of building materials for the solar cells and support hardware is not the Earth, but asteriods that cross or come near the orbit of the Earth - they contain all the necessary elements (silicon, iron, hydrogen, carbon, etc.) to make a solar power satellite in orbit, instead of having to haul every component up from the planet.

Problems

[saider]

Has anyone built a 100% automated large scale power plant? Even here on Earth, such a task is daunting. Saying that it can be easily done on the moon, and done cost effectively is like saying that I could build cheaper cars on the moon because my machinery will only have to cope with 1/6th of the gravity.

"But satellites and the space shuttle use solar power all the time." They also have either a 5-10 year lifespan or are serviced regularly. The article said that it could be profitable in 5 years. So when it finally becomes profitable, many of its components will be nearing the end of their lifespan. Then you have to chunk down some more money to build a replacement.

Nevermind that there will still need to be multiple ground stations in remote areas to catch the radiation. The moon is not geosynchronous. Build a station at the poles you say? There goes your costs again. Also, say what you want about safety, nobody will want to live near these things. And they will have to be in different countries which brings politics into the mix.

This is pie-in-the-sky dreaming. If you ask me, I think the money is better spent designing and running a good nuclear power plant or for some fusion research.