Alan Boyle has an extensive story on the implications of water on the moon for human spaceflight policy. I agree that NASA’s prize focus should be on lunar processing tech demos.
[Update a few minutes later]
Dennis Wingo discusses the importance of lunar water.
I often see these arguments that water would be for drinking, farming and for making oxygen for breathing (there is much easier oxygen on the Moon). Water for all these activities can far more easily come from recycling.
Also consider the consumer products needed from Earth that have hydrogen, oxygen and even carbon in them (food, packaging, etc.), there is enough ongoing water to sustain some losses and increasingly grow stuff (which also requires carbon). This also suggests that packaging should be made of useful recyclable materials, like carbon fiber…
Point being, the primary argument for extra terrestrial water is for use as propellant. If it is not needed for this, then it is not necessarily needed.
And how do you get this recycled water to the Moon to start with/
There are many uses for the water, from an energy storage medium for a closed loop fuel cell system in rovers and other mobile equipment, to things like hydrogen reduction of iron (which is where a lot if not most of that water came from in the first place), to aquaculture (people are not going to eat vegetables all the time on the Moon), to various and sundry industrial processes.
The recycled water gets there in food, packaging, clothes, consumer plastic products, used carbon fiber structures, and so forth – as I mentioned. I suspect it reasonable to assume that people working on the moon will not be completely self sufficient, stuff will be continually shipped up from Earth, and it may as well favor useful elements.
As you well know, these initial requirements for water are largely in the noise (with the possible exception of large scale aquaculture). 1.1 ton of LH2 from Earth could make 10 ton of water on the moon, which would presumably be more than enough for doing rather a lot of things. Not that regolith was ever without trace amounts of hydrogen perhaps sufficient enough for these purposes any way. Burning rubbish and turning it into water is fairly simple.
Sure in the long term a lot of lunar hydrogen for lunar use would be nice, but by then many things would also be possible. As I said, water is really only of great interest for making propellants – it is very interesting in this regard, but that, and that alone is the primary need for large quantities of lunar hydrogen. Well a heated swimming pool would also be nice…
Just a thought, but it seems most of the exhaust of a rocket launched from the Moon would stay in its gravity field. What are the chances it would migrate back into another cold trap?
As you well know, these initial requirements for water are largely in the noise (with the possible exception of large scale aquaculture).
Who’s requirements? This is the whole point, if there is much more water there, then new things can be done within the same cost structure that could not be thought of before.
With the amount of metals that we know are there and readily accessible we can build large structures with copious internal volume. With that you could have a lot of fun with hydroponics for food, plentiful water for hygene (you should have smelled the JSC LER Rover after the crew was in there 14 days during desert rats this year), and even a pool if desired.
Open your mind to the possibilities.
What actually significant things requiring large quantities of water can be done beyond propellants? Swimming and diving would be cool, one could jump clear out of the water like a dolphin, or dive from great heights, but this is hardly a critical requirement. Aquaculture similarly.
A shower does not require a lot of water – and recycled water will be required anyway. Developing such systems would be a good starting point – no need to be unnecessarily uncomfortable. 20-30kg of water could keep a small group of people clean.
People do not generally need to ingest more hydrogen, carbon and oxygen than they put out. Assuming food takes some months to grow, the invested biomass necessary to feed a person is still not a lot.
The amount of hydrogen needed to operate a rather large greenhouse is quite small. Carbon might be far more critical, and would perhaps still have to come from Earth. Nitrogen will also be a big constraint if making large habitats. Materials that use carbon and hydrogen would be more of a constraint.
Lunar hydrogen is a game changer with regard to propellants, but it would only really seem to be a helping hand with regard to most everything else. I would be inclined to focus on the game changing capabilities of lunar water – for now that means propellants.
Just a thought, but it seems most of the exhaust of a rocket launched from the Moon would stay in its gravity field. What are the chances it would migrate back into another cold trap?
I am no expert in this area, but I suspect for launching most exhaust products would end up back on the moon, assuming a very lean low ISP LH2/LOX engine. When deorbiting I would expect far fewer exhaust products to end up on the moon (most would be going faster than lunar escape velocity and in a tangential direction).
Geoff Landis analyzed the degradation of the lunar surface vacuum by industrial activities. While he doesn’t mention cold traps, his calculations of how fast gas entirely escapes the moon seem relevant to the question of whether rocket exhaust ends up back on the moon.
Link: http://www.islandone.org/Settlements/DegradeLunarVacuum.html
Lunar hydrogen is a game changer with regard to propellants, but it would only really seem to be a helping hand with regard to most everything else.
At a $100,000 per kg, that is quite a helping hand.
At a $100,000 per kg, that is quite a helping hand.
Not really, a couple of a percent saving on total mission cost is not going to dramatically change anything. Not that there would be such a saving.
And it would be more like $10,000/kg, oxygen is ~88% of water and roasting a little regolith will yield something like 1-2% of it. But presumably launch costs would have to come down significantly before any of this could happen anyway.
Hydrogen needs for uses other than propellant are unlikely to be more than a few percent of the required landed mass for other things. Recovered hydrogen from delivered food and packaging is likely to be sufficient to cover these needs.
Hydrogen needs for uses other than propellant are unlikely to be more than a few percent of the required landed mass for other things. Recovered hydrogen from delivered food and packaging is likely to be sufficient to cover these needs.
Maybe for a few ESAS sortie type missions but for an outpost or anything serious this level of water is simply insufficient.
Also, if there is water there, you have no need to develop an expensive hydrogen tanker, with strict operational constraints on delivery.
The same system that does any ISRU at all for oxygen will get you the water for much less energy input and could easily be all solar thermal. If you drive the temp up you get metallic Fe as well through hydrogen reduction of the Fe-O so the local hydrogen is very beneficial to your oxygen ISRU system as well and could replace in some instances the much more complicated flourine based wet chemical processes.
To drive a rover any serious distance will require tens of kilowatt hours of electricity, something a closed loop fuel cell system would be great at, and to get the water locally would be far better than hauling it from the Earth.
Quit thinking in a minimalist ESAS mode, that is not how we want things to develop.
Ignoring propulsion requirements, what proportion of the ISS is hydrogen within water? Is it really ~10% or more as you seem to imply? Lets say the ISS was on the Moon and the structural elements were made from insitu resources, would the hydrogen content of the water used still be 10% or more of the delivered mass? I very much doubt it.
I am yet to see a good argument beyond propellants why a lunar base would need proportionately large quantities of water.
Not that one would need a hydrogen tanker, but most everything delivered from the Earth will come on one.
It is much easier to get the oxygen from regolith, solar ovens are easier, the through put can be very high, the yields are very high and a huge expensive and inefficient solar power and electrolysis unit is not needed to extract the oxygen. You do realize how hard it is is to electrolyze and liquefy hydrogen?
I am all for using hydrogen to reduce iron, iron and aluminum in large quantities can make a huge difference on the Moon (please focus more on this and less on non propellant water uses), but again this is a closed loop process, it should not need large quantities of hydrogen.
Closed loop fuel cells are really not that appealing to date, assuming they have actually got beyond vapor ware. Fortunately there are many other options. Batteries are much easier and more reliable, much easier to recharge, and their energy densities are not much less. Aluminum oxygen batteries are another possibility – could be made from insitu resources. Though I am not sure that large mobile energy storage would be on the critical path just yet. Also note that due to a lack of air resistance and one sixth the gravity transport should hopefully require much less energy on the Moon.
Quit thinking in a minimalist ESAS mode, that is not how we want things to develop.
Please quit thinking shiny object/NASA mode that gets no where and start thinking critical minimum energy development path – the serious enabling technologies. For example, water for propellants, large underground habitats, low cost solar power, regolith moving systems, iron and aluminum smelting, carbon and nitrogen sourcing and materials export transport systems.
Ignoring propulsion requirements, what proportion of the ISS is hydrogen within water? Is it really ~10% or more as you seem to imply? Lets say the ISS was on the Moon and the structural elements were made from insitu resources, would the hydrogen content of the water used still be 10% or more of the delivered mass? I very much doubt it.
Irrelevant comparison.
I am yet to see a good argument beyond propellants why a lunar base would need proportionately large quantities of water.
What you see and what others see are different things.
It is much easier to get the oxygen from regolith, solar ovens are easier, the through put can be very high, the yields are very high and a huge expensive and inefficient solar power and electrolysis unit is not needed to extract the oxygen. You do realize how hard it is is to electrolyze and liquefy hydrogen?
Actually it isn’t. To drive off all volatiles in a batch of regolith takes temperatures of no more than 800 degrees C. To obtain oxygen from regolith requires heating to no less than 1500 C. To get more than a small fraction of the oxygen, it takes temperatures of more than 1800 C. (reduces the Fe oxides, Mg oxides, and some Si oxidies. Or, it requires chemical reduction methods, which are complex, though very interesting.
Closed loop fuel cells are really not that appealing to date, assuming they have actually got beyond vapor ware.
I would be more than happy to point you to the many websites where you can buy complete fuel cell systems and a closed loop system that has no outside sulfur contaminants has a lifetime well above 10,000 hours, much better than the best lithium batteries, energy density is better too.
Please quit thinking shiny object/NASA mode that gets no where and start thinking critical minimum energy development path – the serious enabling technologies. For example, water for propellants, large underground habitats, low cost solar power, regolith moving systems, iron and aluminum smelting, carbon and nitrogen sourcing and materials export transport systems.
Way ahead of you there buddy. You might want to read my book on the subject, or the reports that I have prepared under NASA contracts.
What you see and what others see are different things.
I would hope so. Beyond propellants, what do you need all this water for? How is it a game changer? What major thing has all this new hydrogen made possible that was not previously possible? Where’s the beef?
I was just rechecking on using hydrogen for iron production (it has been a few years) – it does not even seem to need to be primed with hydrogen, trace quantities (known of since Apollo) are enough.
To drive off all volatiles in a batch of regolith takes temperatures of no more than 800 degrees C.
Distant memory says this yields something like 1-2% free oxygen, some of which would be yielded at somewhat lower temperatures, is my memory correct? This seems significantly cheaper than ~35kW/kg to split water for oxygen. Electricity is unfortunately not yet cheap in space let along on the moon (making it so seems on the critical path to me), solar concentrating mirrors do seem fairly inexpensive in comparison.
I recall closed cycle fuel cells with energy densities of 600Whrs/kg from ~ten years ago, a quick search now suggests little improvement (I stopped bothering to follow the field long ago). Lithium is more typically within the 150-200Whrs/kg range, though I expect some breakthroughs on that front in the next few years. Some batteries, like aluminum air batteries (perhaps manufacturable insitu), can do much better than this. Considering the additional complexity of fuel cells, why use them? Batteries that last many more than 10,000 hours are not that hard to come by. And there are many other energy storage technologies that are more efficient, less expensive and more reliable than fuel cells (solar thermal with heated regolith energy storage always seemed about the best to me). Closed cycle fuel cells would never be close to viable for grid energy storage on Earth. Is energy density really that critical and where it is, is there really not already enough spare hydrogen around to use? It is being recycled, it is not like it is being exhausted to vacuum.
Water is critical for hydrogen for propellants – and an economic transport system to and from LLO. Though I fear extracting and refining it will not be as easy as one might hope, but this is a game changer. An easy way of getting materials off the Moon has always been highly problematic.
Sorry I have not read your book.
Fuel cell advances into cell phones now.
http://www.breitbart.com/article.php?id=CNG.d91ba987344e9043651104d25f35d1d9.581&show_article=1
There is not going to be a lot of advances in fuel cells after they mature, just as it took almost 100 years to improve the Otto cycle (gasoline engine) with the Atkins cycle (hybrid).
I have read of some interesting experiments where a cocktail of Platinum Group Metals (Platinum, Iridium, Ruthenium, and Osmium) were used to increase the efficiency of a fuel cell by more than double, which is significant. The problem is that there is not enough of these materials and the cost is high. Guess what, lunar PGM’s would solve that problem.
🙂