There’s LOTS of Water on the Moon | Moon To Stay #5

Water will be the the first and most important resource we look for on the moon when we get back there. The water on the moon has the potential to catapult human spaceflight into a new paradigm.

Previous to 2008 many believed the moon was devoid of significant amounts of water. It was supposed very likely solar radiation and low gravity would have resulted in all the water sublimating away over billions years of lunar history and bombardment by cosmic radiation. As such the moon would be very dry. It was only as recently as 2008 ISRO, the india space agency launched the Chandrayaan-1 mission to explore the moon and discovered there was water at the poles hidden in the perpetually dark regions of craters.

NASA fast-tracked the LCROSS mission to double check the discovery of water. LCROSS was a low-cost mission to look for more around the water at the polar regions. This mission used an impactor that slammed into the moon to create a plume of lunar dust which could be examined to confirm the discovery of water. This mission confirmed water, but unfortunately only small amounts. It was later believed the impact location was a particularly dry spot.

NASA also launched the LRO, a orbital satellite at the same time as LCROSS.  LRO is still in orbit around the moon. It is tasked with taking high resolution images and other measurements of the moon. Data from LRO has given us a better sense of how much water is on, or close to the lunar surface.

There is estimated to be at least 600 million metric tons of water ice at the surface in the permanently dark craters at the northern polar region. Evidence shows at least some of this water ice could be several meters thick. That is a lot of water! The water detected at the surface of the moon is enough to supply the ISS for 2 million years!

To date we have really only been able to assess the surface presence of water using radar and optical analysis. There is no easy way to do sub-surface analysis without drilling – like we do when looking for ground water on earth. It is entirely possible we will find more water locked up underground where it wouldn’t be subject to solar radiation and have evaporated. We need to get back there to do some hands on prospecting to find out exactly what the conditions are like, how accessible the water resources are, and what we might be able to get at with a robot.

Current indications are there is enough water, at least in the polar regions, to be mined and used productively.

Since we now have some confidence there is plenty of water available, the next question is what will we use water for?  Water, H20, is critical for all life on earth, humans need large quantities of water to survive – we drink it, the food we eat needs water, and even the air we breathe has some humidity to it. Without water we would die.

We need quite a bit of water to live, and the cost to top up our supplies puts an economic limit to the amount of people we can reasonably afford to have in space at a time. With more water we could support more astronauts.

On the ISS water is rationed and recycled because it is a scarce resource not to be wasted. It costs between $5000 and $10,000 per kilogram to launch supplies to the ISS, and though the actual amount of water needed to replenish the station changes depending on lots of factors, I did some digging and found out last year they launched 420kg of the water.  That’s $4.2M to resupply water every year for the 3-6 people usually on the station in spite of the severe rationing and advanced recycling.

In addition to the water used by astronauts, we use water to grow plants and sustain animals. The rationing of water on the ISS forces limits on how much science can be done. We can’t study growing any significant amount of plants, and we can’t support too many animal studies at any one time. Again, water is a potential limiting factor on expanding our knowledge. With more plentiful water we could accelerate our pace of biological studies in space.

Besides the biological uses, Water can be electrolyzed into Hydrogen and Oxygen, two important elements. Oxygen – very important for us to be able to breath – it powers our metabolic system – without oxygen humans will die in 10 minutes. We will suffer brain damage in just 5 minutes of oxygen deprivation. Hydrogen makes a pretty good rocket fuel and Rockets are pretty good for providing mobility in space – moving people around, re-positioning satellites, and launching payloads back and forth to the moon.

A hydrogen powered rocket, fuelled from lunar water would enable an operational cost savings that makes access to the moon an order of magnitude cheaper than direct from earth approaches with SLS scale heavy lift rockets. The current boom we are seeing due to commercial development of reusable rockets is evidence that when we make things less expensive, we get to do it more often. I expect that will continue to be true with lunar exploration.

One other use we have for this is as stored energy. Re-combining hydrogen and oxygen with a fuel cell produces electricity and water. The international space station uses fuel cells, and if you’re going to have hydrogen and oxygen around anyway, it just makes sense to have a fuel cell for electricity if you need it. Fuel cells can be used as a backup to solar panels, or to store power for the lunar night cycle. Backups add redundancy, and reduce risks. For a moon base that is several days away in the case of emergency, having that alternative to direct solar power will help with astronaut safety.

So, Water is critical for life, it can be turned into rocket fuel for mobility and stored to later be converted into electricity. It is particularly valuable to us as we go further into space. Which is why water on the moon will be among the most valuable things we will get there.

The other thing with water is the ease with which we may be able to collect it. Microwaves like the one in your kitchen are tuned specifically to heat water molecules. One of the most promising ways to mine water on the moon is to cover an area with a collector – a sealed dome or tent like device, and then beam some microwaves in to evaporate the water, collect the steam and condense it to a liquid for storage, purifying it at the same time. There are no reactants, no smelting refineries required, no shovels, jackhammers, or rock crushers. This approach may not even require digging.

The potential for using water from the moon could change the dynamics of space travel. This is how – We build a mostly remote and semi-autonomous water mining operation using robots and solar power. It would produce and store water at a low cost per kg of water. Much lower than the cost to launch that water to the moon from earth.

Locally sourced water from the moon would eliminate the need to deliver it from earth – like is needed to the ISS – which will lower the cost to resupply.  Abundant lunar water would enable large lunar greenhouses to produce astronaut food. If we don’t need to launch as much food and water from earth to support a lunar base that would result in huge savings, or a larger human presence on the moon.

Rocket fuel derived from the lunar water and electrolyzed with solar power would enable transportation on the moon, around the moon, and between the moon and earth. Avoiding the cost of launching fuels will save 10s of millions of dollars per mission, and will make new kinds of missions economically feasible – like servicing satellites. By delivering rocket fuel to lunar orbit or back to low earth orbit we can turn the moon into a fuel stop for deep space – which would open up the solar system to missions launched on even the smallest rockets.

Lunar water, oxygen and hydrogen could be delivered to the ISS at a lower cost compared to launching it from earth – helping to reduce the operational costs to maintain the station – or to relieve astronauts from the water rationing they have to do currently.  

It’s hard to imagine any other resource – iron, aluminum, titanium for example would impact our future in space more than water on the moon.

So we know the water is there, and we have lots of things we could do with it. What we don’t know yet is the reality of the environment on the ground. We need to get more robots and people on the moon to find out – will it be like a flat frozen lake, or sharp shards and deep crevasses. Will that water in dark craters also contain other volatiles? Those are some big unknowns. Until we know more it is difficult to design and engineer the robots to collect the water ice. We’re going to be back on the moon many times in the coming decade to find out the answers and work towards a permanent stay on the moon.

Links:

https://www.nasa.gov/mission_pages/Mini-RF/multimedia/feature_ice_like_deposits.html

https://www.quora.com/Rockets-What-is-cost-of-sending-1-kg-weight-into-space

How much water is re-supplied to ISS: https://www.quora.com/How-is-water-carried-to-the-ISS-Is-there-some-technique-of-compressing-and-carrying-it-and-how-much-of-it-is-carried-into-space-at-a-time