Buy the light of the Moon
by Sam Dinkin
|The Moon does not deserve to be an old-fashioned billboard, but should be a full high-definition television!|
Heinlein’s idea was that fireworks filled with carbon black could be delivered to a central location on the Moon. Then these fireworks would be shot off in various directions and spread carbon black upon impact. The powder would spread quite easily in the vacuum. The result would be “6+” (7up) or a hammer and sickle. While cheap and effective, Heinlein’s idea does not square with the short attention span and high technology available today. It also is not as interesting as a spur to colonization. Heinlein also anticipates “line-of-sight transmission” of television neglecting to note that it would only work half of each day. But if TV from the Moon is novel enough, it might work even if it only is broadcast once a month. Here’s how:
Billboards now are not satisfied to show a single image, but continually shift from image to image. The Moon does not deserve to be an old-fashioned billboard, but should be a full high-definition television! Lasers could be placed on the Moon and powered by solar panels. Cheap solar panels that weigh a few grams per watt could be used to feed 1.3 million lasers (1280 x 1024). If each laser had five kilograms of batteries and five kilograms of solar cells, they could build up 1000 watts for two weeks during lunar day or about 350 kWh from the solar cells. Since that is way too much power than is needed to run only one night per lunar month, we could spend more mass on the batteries and the laser. With 10 kg of batteries we could get 1.5 kWh storage. We could run a 10% efficient array of lasers per pixel giving 75 watts of laser light for only two hours. To run 24 hours we only need about 12 hours of juice because each pixel is only lit part of the time. To get to 12 hours, we need a high efficiency laser, a more efficient battery, lunar manufacturing, or a lunar power grid. A mile of copper from pixel to pixel would weigh too much. Carbon nanotubes could be a great lightweight power line. However, if I had 1.3 million miles of carbon nanotubes, I would build a space elevator, not lunar Christmas lights.
The trick may be to use vacuum to our advantage. Flywheels take months to spin down in vacuum. If we could have a fused silica flywheel, we could get 9 kWh storage with 10 kg. But now we need an efficient engine to get the energy back—back to 3 kWh for a practical system with a 33% efficiency engine and we have spent another 5 kg on an engine and low-g bearings. Stick to batteries. The lasers would need to have communications to Earth or to each other (no ionosphere on the Moon means that coordinating with Earth might be better), low spreading, and high luminosity to mass and power ratios.
If, after some breakthrough, the whole package weighed 20 kg per pixel, this project would entail lifting 26 million kg to the Moon. Suppose heavy lift to the Moon could be developed to take 50,000 kg at a time for $100 million (which is twice the payload of the Space Shuttle at a fraction of the price). We would need 520 such flights or $52 billion worth of launch service. If each station cost $5,000 to produce, that would be another $7 billion. Light lift might work better and the guidance and communication of the last stage launcher might become the guidance and communication of the laser.
Figuring out how bright to make the TV may be the $64 billion question. To approximate, let’s assume an even million lasers. To create an artificial bright star (apparent magnitude 0, like eight of the ten brightest stars) that appears on the Moon would take approximately 3 x 10-5 w/m2. That corresponds to a 76-watt laser array for each pixel to illuminate a 2.5 square kilometer circle (1 square mile) on Earth. Each laser array could sweep the populated areas of the Earth and depending on the population covered, there could be a million squares covered. The overall brightness of the image would be that of a bright star, but each of the million pixels would only shine for one millionth of the time. That might be too dim to make out even in the darkest areas. Any particular pixel would only be magnitude 15 with a flux of 3 x 10-11 w/m2 which is a lot dimmer than magnitude 7, the dimmest naked-eye viewing in a dark sky. With each pixel at the limit of urban viewing, 2.5 magnitude or 3 x 10-6 w/m2, we could illuminate only 25 square kilometers. The resulting complete image with a million pixels would be as bright as the full Moon at apparent magnitude -12.5. This might take some experimentation to get right. There are lasers that produce thousands of watts, but unfortunately, these CO2 lasers work in infrared and not visible. The laser array for each pixel should not be too bright or it will be prohibitively costly. It should not be too dim or no one can see it. Fortunately, these experiments can be done on Earth pretty easily. Call me an economist, but let’s compromise at 50,000 square kilometers with the pixels at 1.5x10-9 w/m2 (apparent magnitude 11) and the whole image at 1.5x10-3 w/m2 (apparent magnitude -4). That would be enough to hit the high-density areas of the top 33 US cities and cover 40 million people at once.
|Figuring out how bright to make the TV may be the $64 billion question.|
The resulting TV station would be unlikely to be worth $60 billion, but it might be close. The audience might be 10 million people for 24 hours straight once a month as prime time sweeps around the planet. If 25% of the time is sold to advertisers at $300k per 30 seconds (less than the Super Bowl, but only 50% more than what England calculated commercials for a three-hour show would be worth), that would be worth $216 million per lunar month or $3 billion a year. Maybe rebroadcasting on a satellite/cable channel would help the Moon raise viewership of the traditional station. That might be worth another $6 billion a year. A 5% or even an 18% return on capital are both pretty poor for such a risky proposition, and we have not paid for content, R&D, or operations and maintenance yet. Maybe starting with 480 or 320 scan lines would be the key to meeting investment hurdles, but that would reduce overall image luminosity so that would not necessarily get us much. Maybe there are some other alternative technologies or other services that can help make ends meet. Projecting some excess power as light during lunar day to an Earth-based solar array probably wouldn’t be worth much, but adding video to an existing lunar solar power broadcast buildout might enhance it.
George Allan England’s idea of shining images from Earth onto the Moon would not be as cost effective. The power required to project images from the Earth onto the Moon would need to be ten million times more powerful than those required to shine back from the Moon. There are three factors that make lunar lasers much better than Earth-based illumination. First, the Moon’s albedo is only 12%, so eight times as much light will need to be shined on it than is reflected back. Second, the Earth only takes up a little bit of the Moon’s sky. At 60 Earth radii, the Earth seen from the Moon spans a little less than two degrees. If light bounces off randomly in a hemisphere, 99.99% of the photons’ reflection will go off into space and not hit the Earth. Third, a laser can focus on populated areas where the light level is just right and most people are still awake. That can reduce the power requirements of a Moon-based laser by another 99%. Shining on a quarter crescent Moon as England postulated would not work with the Moon’s apparent magnitude of -12.6 (when full). If projection from Earth is therefore not cost effective, perhaps value added services can enhance the business plan.
A much more compelling reason exists than cost to have a Moon-based projector. That is, different images could be projected at different spots on Earth. Laser beam divergence of common laboratory lasers is approximately one mile from the Earth to the Moon. That would allow localized content to be televised in different locations and more importantly, localized advertising. Different areas can also receive different resolution and brightness depending on their economic importance, whether high value content can be found for that market at that timeslot and the weather around the planet. Content may be able to be localized down to someone’s garden party given that laser light spreads very little between the Earth and the Moon. Many, many separate garden parties can be served in addition to regular TV content.
|The power required to project images from the Earth onto the Moon would need to be ten million times more powerful than those required to shine back from the Moon.|
Another service that can be offered is disaster warning. Krakatoa erupted in 1883 becoming the world’s first global disaster. The event is described in colorful detail in an excellent book named after the volcano that tells much of the history of Dutch and English colonization. The recently-completed telegraph to England was instrumental in allowing the world to share information about the disaster and dispatch relief. While we probably will not lay a telegraph wire to the Moon as predicted in Harper’s in 1856, the Moon may be the key to a modernized and more effective global alert system. Brightly-colored flashes from the Moon might be able to be seen on a crescent or half Moon possibly during daytime.
Whenever there is an impending volcanic eruption, tsunami, earthquake, hurricane, or asteroid strike, the lunar lasers can shoot a message that would be visible only in areas of danger. By utilizing this emergency broadcast system, any nation of the world can bootstrap instant communication to its entire population at risk. This is much more of an inducement to rural societies than to cell-phone and mass-communication linked rich urban ones. These nations have low TV penetration so are apt to appreciate the literacy promotion potential of lunar TV. There are a lot more such nations in the UN than there are rich ones, so don’t bet too heavily against lunar advertising on Ladbroke’s.
However, the bet against is probably more profitable at this point. There is a lack of regulation so there are no assurances either way regarding whether the Moon is available for such shameless exploitation. Such assurances would certainly be necessary in light of environmentalist backlash likely to be spurred by lunar TV. Vote.Com held a poll in 1999 and two-thirds of those polled were against lunar advertising. We may have a property rights regime where the Moon and other celestial bodies are held in common, which technically means that there is no right to exclude someone from advertising on the Moon. But the minute that an entity tries to do something that is against the international consensus there will spring into being a lunar authority charged with preventing harmful development from occurring. One of the best ways to bootstrap property rights from a commons is to do something that no one else wants you to do on the commons.
Therefore, before raising billions to put lunar television in place, the would-be developer should take a page from D. D. Harriman’s playbook and find broad international local support for lunar TV before attempting development. Unlike Harriman’s theory that only nations that are less than 28 degrees latitude are the owners of the Moon, the Moon Treaty of 1967 makes the Moon the province of all Mankind. Lunar development is deigned to be coordinated amongst all nations. Therefore, local lunar development companies should be established in all nations, in much the way that satellite phones should have localized their marketing and lobbying.
|There is something appealing about using a guy in a truck to maintain the system. That’s what we do for cable TV here on Earth.|
There is, of course, a problem in convincing developing countries to use the Moon as an emergency broadcast system—there would be no broadcast on the other side of the Earth from the Moon and no broadcast during the day. For daytime use, we would have to up the peak power by a factor of 10,000. That might be accomplished with a mirror array since we have a million lasers (thanks George) and only need to send a binary message. A fleet of microsatellites in low orbit might work for the other side of the Earth. It would also be a bit trickier, but perhaps not overly so, to aim a laser from a zippy low flying satellite, but it begs the question about using the Moon at all. Putting another constellation of satellites at the various Lagrange points would not make sense because stationkeeping (not to mention getting there in the first place) would make the cost prohibitive. There is something appealing about using a guy in a truck to maintain the system. That’s what we do for cable TV here on Earth. By putting lasers on luna firma, a person or a robot could maintain the lasers and emplace new ones. Half a loaf will hopefully be seen to be better than none.
So I raise a glass of 7up to the upcoming centennial of George Allan England’s “The Lunar Advertising Co. Ltd.” and the recent semi-centennial of Robert Anson Heinlein’s “The Man Who Sold the Moon.” New technology is allowing England’s business plan to nearly become feasible and Heinlein’s business plan has held up over time. Environmental cleanup of carbon black on the Moon might just be the key to beginning colonization.