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28 April 1998: I wrote this after the Clementine mission, and before the Lunar Prospecter mission. Lunar Prospecter returned additional data about the possibility of ice at the moon's polar regions. However, the analysis and conclusions remain the same.
We have heard a lot of debate concerning the alledged ice at the Lunar South Pole. Based on what we know now, if that ice is really there, it just isn't enough to be economically significant.
We need to figure out how much the ice is really worth. Depending on your source, there is about 15,000 cubic feet (425 m3). It's about the amount of water in the fish pond on my grandfather's farm in Martinsville, Indiana, or roughly the volume of water contained at this very moment in the new Neutral Buoyancy Laboratory at NASA.
That's about 128,000 lbs (58,000 kg) of hydrogen, or about how much is imbedded in the top 10 cm of a square kilometer of regolith at 1 part in 10,000. To extract that hydrogen, however, one would have to process 580 kilotons of regolith. In that regolith, one would also find very roughly 60 tons of nitrogen, 120 tons of carbon, 10 tons of helium, 2.5 kilograms of helium-3, and 500 kg each of neon, argon, krypton, and xenon.
Assuming chemical rockets are used to deliver this much hydrogen to the moon from LEO with an Isp of 460, we'd need 3.76 times as much mass in LEO as we deliver to the moon's surface. Add in 4% for the weight of the tanks, do some arithmetic, and we need 500,000 lbs (225,000 kg) in LEO to get that much hydrogen to the moon.
That's about 8 Titan IV launches, which we could get for $125 million each if we could talk the US Air Force into putting our payloads into LEO. So, assuming that the cost of obtaining and processing lunar ice into tanks of liquid hydrogen is negligible (a very unreasonable assumption), the street value in downtown Luna City of that much hydrogen in that theoretical lunar ice is about US$1 billion.
That's $1 billion using 1996 technology. When the moon fleet gets running, the cost of delivering that much hydrogen to the moon will drop by about two orders of magnitude, so let's guess $10 million.
I'm not exactly overwhelmed by that much hydrogen.
Can't say I'm underwhelmed, either. It's just about the amount of water we need to support our little city in the moon; not enough to really do things in a big way, but nothing to be scoffed at, either.
Some folks have suggested that we should consider doing whatever it takes to get the lunar community started; even if that means using in-situ hydrogen for propellant. However, it doesn't seem like this theoretical puddle of ice at Artemis Antarctica will be worth the bother to go get it. It just doesn't make a big impact on the overall balance sheet.
Further, the scientific value of the stuff is far greater than its intrinsic commercial value, assuming there's a lunar community who would want to buy water ice for the sake of using the water. Also, whatever today's selenologists could learn from studying this stuff, one couldn't guess what the lunar scientists two generations hence might be able to learn. However, this ice is an anomalous condition on the surface of the moon; so I'd guess that it is scientifically important. I can't champion the cause of doing anything that would forever destroy the data.
So, it doesn't make sense for us to plan on using this resource for either life support or rocket fuel. Let's let the geologists have first crack at it, and leave its commercial value for our grandchildren to exploit after they have learned all there is to learn.
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