Building Heavy Machinery on the Moon

Calliban · 2024-08-20 09:29:00

An interesting youtube video.
https://youtu.be/2TigGaT2C-o?si=fJzoem23eRrliubP

We are going to need a lot of heavy equipment to build things on the moon. This should be made from local resources so far as practicable. We recommends using carbon steel for as much of the equipment as possible. That makes sense to me as it is the easiest metal to produce and resistant to cyclic stresses as well as cold effects.

What about power? There are no fuels and very few volatiles in general on the moon. So electric batteries will be the power source. He misses the obvious choice of sodium sulphur batteries for some reason. Electric motors would use aluminium coils and aluminium will be the general conductor material. Although he doesn't say it, calcium could be used in this way as well. Use puller cables instead of hydraulics.

tahanson43206 · 2024-08-20 12:37:21

This post is reserved for an index to posts that may be contributed by NewMars members over time.

Best wishes for success with this interesting topic. It seems to me that what is proposed for the Moon would work on Mars, with adjustments based upon material availability.

Update 2024/08/23 post by kbd512 re making heat shields on the Moon for Earth return service:
https://newmars.com/forums/viewtopic.ph … 71#p225971 Silicon Carbide wins selection process

(th)

Last edited by tahanson43206 (2024-08-23 06:08:06)

kbd512 · 2024-08-20 13:42:28

I think we've already proven that we can devise much simpler thermal power systems that match or exceed the energy density of batteries, and high temperature radiators are much easier to maintain than photovoltaic arrays. They tend to be very durable and long-lasting, because they're made from steel. This point seems totally lost on people who think we're going to make everything electric. We've done no such thing here on Earth. We power all mining machinery with electric motors AFTER a thermal engine burns fuel to provide on-demand electrical power. As everyone has already pointed out, there are no known underground reservoirs of hydrocarbon fuels on the moon, nor atmospheric O2 to burn them with. That doesn't mean a thermal engine isn't viable, it only means a thermal engine burning fuel isn't viable.

He briefly touched on the numerous manufacturing difficulties involved with producing high-tech items such as electric motors and electro-chemical batteries, but then his solution for mining and infrastructure build-out mandates using those devices. He said he couldn't evaluate how complex any of that would be to set up on the moon. Essentially, he's "hand-waving" all the real complexity the way almost everyone does. That means all such high-tech devices need to be imported from Earth, long after mining starts. Creating a storage tank for molten salt or molten Silicon thermal energy store is drastically simpler than creating an assembly line that produces or refurbishes electro-chemical batteries, electric motor-generators, photovoltaic cells, wiring, etc.

According to his ideation about how this mining and industrial plant build-out will occur, we're going to create all the mining and manufacturing infrastructure required to produce steel and concrete on the moon, but then we're going to additionally mandate the use of all these high-tech items which also don't presently exist on the moon, because we cannot make them on the moon using the exact same technologies we're already developing to produce steel products and more / larger / more efficient mining machines.

There is an actual electric mining truck. It's batteries can supply just enough power to make it up the mining pit one time, and then they partially recharge going back down into the pit, but the machine can effectively make a single trip over multiple hours because a battery recharging "time out" is then required to complete subsequent trips. Perhaps the reduced weight on the moon would enable more trips per shift, but the same would be true of a simpler yet more power-dense purely thermal / mechanical power delivery subsystem.

Someone please make this make sense. It's as if actual mass manufacturing knowledge has become a "lost art", and nobody is aware of the "snowball effect" of mandating additional complexity and specialization. We're going to build-out the infrastructure to produce vast quantities of steel and steel products, which are also suitable for making mining vehicles and thermal power systems, but then the most obvious choice for both producing and powering more of these machines on the moon, using the very same materials we just spent so much money to dig out of the lunar regolith, are then NOT used to power these retro-futuristic mining machines.

Umm... What?

What is the reasoning behind building out multiple entirely separate manufacturing facilities to fabricate electro-chemical batteries, photovoltaics, and electric motor-generators?

Option A
Metals mine
Metals smelting facility
Metals fabricating facility (can produce the desired end product, more mining machines, and power)

Option B
Metals mine
Metals smelting facility
Metals fabricating facility
Battery fabricating facility (requires its own mining and smelting, plus specialty machines)
Photovoltaics and power electronics fabricating facility (requires its own mining, plus specialty machines)
Electric motor-generator fabricating facility (requires its own mining, plus specialty machines)

If you're already contemplating building these "steam punk" machines, as Terraformer calls them, how does adding unrelated "critical path" infrastructure assets assist with the prospect of ultimately creating a self-sustaining economic endeavor that doesn't require endless materials support from Earth. Modern civilization was built using heat, steel, and concrete, not photovoltaics and electro-chemical batteries. All electrical and electronic devices are artifacts of heat engine simplicity, productivity, and durability.

Having to import microchips to regulate life support vs having to produce both the materials and photovoltaic cells to power the entire endeavor are two wildly different materials and mass requirement propositions, which is why we can import the life support equipment but have no hope of importing enough energy generating devices to establish much more than an outpost that doesn't really contribute much, economically-speaking. Using functionally unlimited hydrocarbon energy supplies here on Earth, we've been making photovoltaic cells and electro-chemical batteries since the Industrial Revolution started. None of them provide 24/7/365 power to anything whatsoever, beyond tinker toy scale systems. There's always a thermal engine back-stopping the fact that these systems don't scale-up to the degree required, typically an internal combustion engine.

The spouting-off about Aluminum conductor electric motors being 25% bulkier but somehow lighter than Copper is pure ignorance on display, someone who clearly knows nothing about EV electric motor design. Also, he seems to not understand ampacity ratings for Aluminim vs Copper wiring, else he would know that the conductor is 50% lighter for equivalent electrical conductivity, not 66%.

He would also know that, at least according to a real EV motor engineer who designs electric motors for EVs for a living, an equivalent electric motor using Aluminum conductor wiring ends up about 50% larger AND 50% heavier (because most of the motor's weight is in all those other materials not comprising the conductor wiring), and that it has significantly impacted cooling performance (is more difficult to adequately cool to maintain the ampacity rating of the Aluminum wiring). The cherry on top was Aluminum wiring fracturing more easily than Copper from motor or vehicle vibrations, thus requiring multiple annealing steps during and after winding. Those are the real reasons EVs don't use Aluminum conductor wiring. It's not because no electrical engineers who design motors have ever thought they could possibly use Aluminum wiring if and when Copper became too difficult or expensive to source. The motor ends up being larger, more expensive, requires a larger and more expensive cooling system, and that confluence of confounding design factors adds up to a highly undesirable end product whenever Copper is available.

To adequately cool Aluminum wiring electric motors in +250F conditions using radiation alone, I presume a fairly substantial low temperature radiator array will be required. Radiator array size substantially decreases by using higher temperatures, as a thermal engine would do. The materials used by the array to cool electric motors can be a lighter Aluminum and glycol coolant vs heavier steel for a thermal power system using liquid metal (NaK) or supercritical CO2 for thermal power transfer, but said vehicle power subsystem component will still be present in any actual vehicle design of similar size and weight to an excavator or haul truck suitable for large-scale mining operations.

At 200F / 93C, 1m^2 of radiator panel can dissipate 1,882W of heat.

At 1,382F / 750C, 1m^2 of radiator panel can dissipate 114,337W of heat.

At 1,832F / 1,000C, 1m^2 of radiator panel can dissipate 274,125W of heat.

You'll need special refractory alloys to operate at high temperatures, and a ceramic sCO2 gas turbine, but the components become truly tiny for the amount of power output they generate. Something like this can be imported from Earth, because it represents such a tiny fraction of the total vehicle weight. The bulk metal for the vehicle itself and the high temperature ceramics used to insulate the very hot salt tank (Calcium Oxide melts at 4,662F) can come from the moon, not Earth! CO2 begins to break down at 5,840F, so CO2 can transfer heat energy into the Calcium Oxide salt. Even if we imported the first batches of salt and CO2 or NaK from Earth, CaO and CO2 don't break down at the temperatures involved, so unlike an electro-chemical battery that is constantly losing energy storage capacity over time, the salt and CO2 never do. NaK boils at 785C, so CO2 might be a better thermal power transfer fluid at very high temperatures.

Moreover, since lunar regolith is so good at insulating, we could cast blocks of pure Iron to store thermal power from sunlight using the very material (Iron) we're trying to mass produce for other uses. For bulk energy storage, until and unless we quit fixating on "the great disabler" which so greatly hampers all of these grandiose schemes for industrialization and colonization, namely the production / generation / storage of electrical energy, then we're never going to create a self-sustaining colony. Electricity is a brain dead solution to our energy problems, endlessly proposed by well-intentioned people lacking a rudimentary understanding of what they're proposing when it comes to bulk energy production and storage. It's not their fault, though. They teach more ideology than engineering in colleges now. Electrical power's primary applications should be computing and lighting, but not much of anything else, because the very moment you select this option, it's tantamount to developing a Rube Goldberg machine.

Electricity is efficient at transmitting power over great distances (relatively speaking) and converting stored electrical energy into mechanical work output. Due to entropy, it's wildly inefficient in terms of materials inputs and complexity. All electrical / electronic machines are "entropy machines", as I call them. You start with the most highly disordered forms of matter (scarce specialty metals) and energy inputs (photons) and must then convert them to the most highly ordered output (electricity with a very specific voltage / amperage / frequency if AC) humanity can produce. We never directly store electrical energy at anything approaching the scale required for industrial mining. None of that means its overall usage is efficient as a substitute for thermal and mechanical systems, because it requires such a diverse and energy-hungry smorgasbord of materials and machinery inputs to function at all.

Think of mining in terms of electric trucks that the entire City of Chicago cannot recharge, all at the same time.

1 haul truck equals 10 Tesla semi-trucks, meaning think of each haul truck as a 10,000hp machine, vs a 1,000hp machine.

A company very recently wanted to purchase and run 120 Tesla semi-trucks using Chicago's electric grid. If all of them were plugged in and recharging at the same time, the electrical energy demand exceeded the total electrical energy supply that provides energy to millions of people living in the City of Chicago. It's entirely plausible for an industrial mine to run 4 excavators, 4 loaders, and 4 haul trucks, 24/7/365 (until they break down and require repairs). If each of those machines is a 10,000hp mining implement, then the electricity production required to keep them up and running probably exceeds that of the entire City of Chicago.

Maybe those machines require less power than that because they're on the moon in 1/6th Earth's gravity, but you know what? That still doesn't matter the least little bit, because the smelter still requires power to refine the ore into metal, and the machines that make the steel products really do require electricity, because those machines used for that purpose (metal shaping) actually do represent the most efficient use of electrical energy.

How plausible does it seem to generate and somehow store more electricity than the entire City of Chicago, for a single mining operation?

You know what that looks like to me?

Blind ideologically-fueled silliness. It's not a serious proposal. It's futurism drivel. It's something that ain't gonna happen because it's a ridiculous proposition. We're primarily building on the moon so we can reach further out into the solar system in an economically sustainable manner, and also to move some of our people off of Earth, and to move heavy industry off of Earth using their input labor, primarily so that we don't environmentally destroy the only as-is habitable planet in the solar system in pursuit of ideological silliness masquerading as something it is not now and never will become, because the people fixated on it are mindlessly building Rube Goldberg machines that fewer and fewer people can afford while they wonder why sensible people aren't buying into their futurism fantasies.

Void · 2024-08-20 18:56:44

This topic is interesting, but I will not try to obstruct or duplicate your materials.

I am interested in two primary activities for the Moon Skylights, and special resources.

I say skylights and do not object to lava tubes, but skylights themselves may be of value.

I think that at least 9/10ths of the activity on the Moon should be robotic and more likely 99% should be robotic. The Skylights may offer some fair protection for some types of such robots. I am thinking of the building of extensive factories in and around those skylights.

https://www.nbcnews.com/mach/science/gi … ncna813396

https://www.astronomy.com/space-explora … moon-base/
Quote:

Studies have investigating sealing off and pressurizing a lava tube itself for use as a lunar habitat, but that plan is fraught with unknowns. A more practical venture might be to deploy an autonomous construction robot like an oversized Roomba that would clear and flatten the floor of a lava tube. Inflatable modules then placed in the shelter of a lava tube could quickly establish a permanent base on the Moon. Additional data returned by LRO’s Diviner Lunar Radiometer Experiment show the temperature within the Tranquillitatis skylight remains a benign 63 F (17 C), simplifying the design of an inflatable habitat.

And elsewhere China found the notion that there may be water in salts, in at least one place on the Moon.
https://www.msn.com/en-au/news/techands … ngNewsSerp
Quote:

There's water on the Moon, and scientists have just confirmed where a lot of it may be hiding.
A mineral in Moon dust collected by China's Chang'e-5 lander and ferried to Earth was recently found to contain so much water, it makes up 41 percent of its weight.
The mineral is similar to novograblenovite, which was only identified a few years ago in basaltic rock from Russia's Kamchatka Peninsula. Both the lunar and terrestrial versions have the chemical formula (NH4)MgCl3·6H2O, and have similar crystalline structures.

In addition, there are hints that more Carbon exists on the Moon than expected. I believe Japan found some evidence of that: https://phys.org/news/2020-05-carbon-em … 0from%20it.

But we can see.

A problem we have is that one of the American goals is to put a woman of color on the Moon. Now don't get me wrong, that is a actual desire even for me. But I don't see that there should be any emphasis for leaving large amounts of people on the Moon, until sufficient and low cost resources for it are found. If there were to be people on the Moon, then fine make them all women of color, to please any DEI agenda necessary, as long as they are competent to do the needed work, and I expect that many can be.

Well OK then, I will leave you alone as that may suit you.

Done

Last edited by Void (2024-08-20 19:15:49)

kbd512 · 2024-08-20 19:13:32

Cat 797 Offroad Mining Truck
Fuel: 1,000 gallons to 1,800 gallons
Engine Power Output: 3,550hp
Steering Tank: 67 gallons
Steering System, incl. Tank: 95 gallons
Brake / Hoist Tank: 203 gallons
Brake / Hoist System, incl. Tank: 489 gallons

1,800 gallons is 71.55MWh worth of diesel fuel energy, of which the truck might receive as much as 40% as mechanical energy output. I presume we need 1/6th of that for lunar operations, because we only need 1/6th the engine horsepower for the same speed, so 11.925MWh. It's feasible to get 60% of that energy back out at the extreme temperatures involved, using a 3-stage sCO2 gas turbine with heat reinjection / recovery between the stages. The means we need 19.875MWh of thermal energy storage.

Calcium oxide or "lime" heated to 1,414C can store 1.2Mh/m^3. That means we need 16.5625m^3 of CaO for thermal power storage. Calcium oxide is 3,340kg/m^3, so 55,318.75kg of mass (9,220kg on the moon) is devoted to thermal energy storage, excluding the mass of the tank. The Caterpillar 797's engine is rated at 3,550hp. Presumably, we require 592hp on the moon. A Caterpillar C-175-20 diesel engine weighs 23,400kg for comparison purposes. Its diesel fuel supply weighs 5,797kg. The fuel tank must also weigh something, but so will a thermal energy storage tank. I'm guessing a refractory alloy tank and insulation will make the scO2 gas turbine engine and thermal energy storage tank weigh every bit as much as the 797's original diesel engine. It's a different form factor and weight allocation. The original diesel engine does occupy a physically greater volume / space claim than the storage tank, so that's a good thing for technical feasibility without a radical vehicle redesign. Extreme width across the outside of the tires is 9.14m and vehicle height is 7.21m. Given a 2m diameter / 7m long thermal energy storage tank in lieu of the diesel engine, the salt storage tank volume is 21.99m^3, so plenty for the CaO and embedded piping to transfer thermal energy into and out of the tank. Inconel 625 has a 982C maximum service temperature limit in air, but we're not placing any real stress on the tank, which will be coated with Silicon, with interior insulation. It has to support its own weight and that of the CaO. The tank itself is not pressurized at all. The sCO2 in-tank piping and radiator, however, will need to be much stronger, which implies the use of a refractory Molybdenum-based alloy to withstand both high temperatures and high pressures.

Lighter drive train components could be used since the 797's axles are extremely heavy to support its crushing weight here on Earth, but then they'd require complete redesign. Who wants to do that when we have something that we already know will hold up well under Earth-like gravity? If it's completely over-built, that's a good thing. It won't require as frequent repair when it's nowhere near as highly stressed / loaded. If we used tracks instead of tires, CG would be reduced, reducing the possibility of rollover accidents. Shock absorbers and spring rates will require appropriate adjustment for lunar gravity. We could devise a lighter bed design, perhaps a welded honeycomb design that uses thinner sheet metal instead of thicker plate.

For our choice of steels, we require something that is both strong and incredibly tough under modestly cryogenic temperatures. Mangalloy fits that description, now that we have techniques to weld and shape Mangalloy plate steel for LNG tanker ships and tank farms, at the lowest possible cost. It's ye olde alloy steel, the original. It was/is used in rock crushers, forging hammers, tank track links, and bank vaults. Manganese is also used to remove impurities from steel, especially Sulfur and Phosphorous. Both initial and off-world fabrication cost and availability of metal for repair on the moon or Mars will be enhanced by not requiring Chromium and Nickel. The stainless will be reserved for chemical processing plants, life support, and kitchen or surgical uses where Mangalloy would be sub-optimal. However, if Silicon-coated Mangalloy is cheaper to produce, then there's no reason to waste perfectly good Chromium and Nickel making weak or brittle stainless steels.

Calliban · 2024-08-21 02:31:32

Calcium oxide would be a byproduct from aluminium production from lunar anorthite. This is an abundant lunar highland material.
https://en.m.wikipedia.org/wiki/Anorthite

But really any solid ceramic material will do for thermal energy storage. Loose basalting rocks in a jacketed steel can will do the job. The insulation can be provided by a layer of fine regolith in the jacket. Under lunar conditions, regolith is a better insulator than rockwool is on Earth. On the airless, waterless moon, sulphur dioxide would make a good working fluid for thermal engines. It is non-corrosive so long as water is kept away from it. The moon is a famously dry environment. Sulphur is one of the few volatiles that exist there in any practical abundance.

Last edited by Calliban (2024-08-21 02:33:36)

Void · 2024-08-21 10:00:13

Thankyou Calliban. I had not thought of Sulfur Dioxide. That is a very good one. I want to borrow it.

Done

tahanson43206 · 2024-08-21 10:45:13

For Calliban re Sulfur Dioxide as compared to liquid Sulfur for machinery applications...

Void has pointed out that Sulfur Dioxide may have value.

Sulfur Dioxide is reported (by many sources) to be a gas.

Sulfur is a solid at room temperature, but it becomes liquid at 115.21 Celsius.

The source I found for this information is the Royal Society of Chemistry.

My question is about the advantages and disadvantages of Sulfur Dioxide (as suggested by Void) as compared to metalic Sulfur.

I found a paper from a National Space Society conference that includes discussion of uses of Sulfur on the moon.

Lunar-Bases-Conference-2-509-Uses-of-Lunar-Sulfur.pdf

One interesting application, which you may have already reported in earlier posts, is concrete. Apparently Sulfur concrete has advantages over Calcium concrete, except that it is sensitive to temperature so should not be used under the surface.

(th)

Last edited by tahanson43206 (2024-08-21 10:46:43)

Void · 2024-08-21 11:14:13

Sulfur Dioxide as a working fluid is entirely Callibans idea as seen from my view.

Sulfur is another issue. It would have it's uses. The two are not in a contest against each other in this regard.

And fyi, I do not like the method of contest as per binary comparisons. It too easily summons the lower mind functions and so then interferes with the higher mind functions. Sulfur joined with two Oxygen atoms makes a useful fluid that is much less corrosive/burning than LOX would be. Working fluids on the Moon seem to be in short supply so, I am very happy that Calliban introduced this idea.

Done

Last edited by Void (2024-08-21 11:17:47)

kbd512 · 2024-08-21 22:59:07

A Caterpillar 797F mining haul truck costs about $5M USD. That's a lot of money for a truck, but the cost is not outlandish for a mining operation. Starship is projected to reduce launch costs to between $10/kg and $20/kg. Every indication is that SpaceX is drastically reducing the marginal costs of producing and launching each new Starship. Cat's 797F truck weighs about 260.7t and was designed to be broken down into multiple large pieces, of roughly 40t to 50t each, for shipment / delivery to a mining site using standard semi-trucks with modified trailers to support the extra weight.

At $20/kg, or $5,240,000 USD, that means launching said truck into space costs about as much as the truck itself. There are certain optimizations we could make to the body and bed to reduce weight and cost, which we should do, but even after doing that, the weight savings would be nominal, absent a complete redesign to take full advantage of the moon's lower gravity. I think that's a mistake, because drastically reduced wear and tear from reduced weight means the truck's useful service life should be significantly increased. Careful selection of steels used must be made to ensure extreme cold and heat, relative to Earth, don't cause problems. That said, this mining truck variant also operates without burning any diesel fuel. All the steel produced on the moon isn't having any significant effect on Earth's environment.

There's an associated one-time transport fuel burn, specifically Starship's LNG propellant, but the total quantity of fuel consumed is only equal to about 109 days of operation of the truck here on Earth, assuming said truck is operated for 2 shifts per day. If the truck is operated 24/7/365, then Starship Super Heavy V3's fuel burn represents 2 months of truck operation here on Earth. Mining trucks are typically operated for at least 20 years.

3,099,853lbs of LNG fuel is the anticipated LNG burn for Starship V3, or about the same as 436,599 gallons of diesel fuel. The truck's engine delivers a maximum of 3,550hp / 2,647,235W of power, which implies 6,618,087.5Wh of fuel burn at 40% efficiency, or 166.49 gallons per hour. However, daily fuel burn per truck here on Earth averages out to about 1,680 gallons, so the Starship delivery flight is equal to 260 days of continuous operations here on Earth. I presume that's why 797A had a 1,000 gallon tank, 797B had a 1,800 gallon tank, and 797F (current model since 2009) has a 2,000 gallon diesel tank. That would mean regardless of how heavy the use was, the truck only has to be refueled once per day. Mining trucks have to be operated for 20 to 25 years here on Earth, so 12,264,000 gallons of diesel fuel burn over 20 years of mining operations, so that fuel burn rate is equal to 28 Starship flights. We're already way, way ahead on fuel burn rate, which is a good sign.

Our mining truck costs $10M, for the truck and transport flight purchases, but on the moon our "fuel cost" is non-existent. Our lunar metals mine and smelter doesn't pay any fuel bills or taxes or land / environmental permitting fees after its equipment has been delivered. There are no mining reclamation fees when the mine shuts down, either. Up-front delivery costs are clearly quite expensive, but operating cost is limited to spare parts and a handful of machine operators who cost $120,000 per operator per year. Transporting them to and from the moon every 6 months isn't much money. We'll assert that they'll receive $250,000 worth of training as well, to ensure their survival and productivity on the moon. They're graduate-level truck operators. That means salaries and training amount to $1.11M per machine operator per year.

$10M truck purchase / transport (one-time)
$2M (one-time operator training cost for 8 machine operators)
$0.48M for 4 machine operators per machine (per year salary, but they only get paid while they're working, so 6 months on and 6 months off)
$0.52M for spare parts and consumables per year

That's $32M per machine, over 20 years. At current diesel prices, the fuel bill for operating said truck here on Earth is about $24.5M. Our all-in cost is $1.6M per machine per year.

There are around 50,000 giant mining trucks in operation globally. The largest examples are around 16m long, 10m wide, 8m high, can carry around 350-450 tons and reach top speeds of 40mph.
This data-file captures the economics of a mine haul truck. A 10% IRR requires a charge of $10/ton of material, if it is transported 100-miles from the mine to processing facility. Assumptions can be stress-tested overleaf.
Fuel consumption is large, around 40bpd, or 0.3mpg, comprising around 30% of total mine truck costs at c$1.5-2/gal diesel prices. Some lower carbon fuels are c5x more expensive, and would thus inflate mined commodity costs.
High utilization rates are also crucial to economics, to defray fixed costs, which are c50% of total costs, as our numbers assume each truck will cover an average of 500 miles per day for c20-25 years.

Calliban · 2024-08-22 02:01:33

The complete lunar sourcebook is available online here.
https://www.lpi.usra.edu/publications/b … ourcebook/

Also, why a railgun makes more sense than a mass driver when launching from the moon.
https://youtu.be/QdVMfmf5AbM?si=1q3IHWp4noxq1NAd

Ablation due to arcing is a problem for rail guns. But on the moon, we can vacuum plate rails with aluminium after every x number of shots. We can build a dedicated vehicle to do that.

Last edited by Calliban (2024-08-22 02:53:34)

Calliban · 2024-08-22 05:29:05

Re Kbd512, your analysis suggests that initially at least, we are better off importing heavy equipment rather than making it on the moon. The first generation of equipment must inevitably be imported.

Two additional problems for equipment operating on the moon.

1. Keeping dust out of moving parts. All moving parts need to be well shrouded to keep out lunar fines. Apollo experience taught us how destructive lunar dust is to space suits. If it gers into wheel bearinfs they won't live ling.
2. Lubrication of moving parts in vacuum. There are low vapour pressure lubricants, whose rate of loss can be reduced further by labyrinth seals. There are also certain soft metals that can provide lubrication to steel parts, lead for example.

Last edited by Calliban (2024-08-22 05:31:43)

tahanson43206 · 2024-08-22 06:24:29

For Calliban re #12....

Your note about lunar fines reminded me of a study that was reported recently, but at the moment I can't remember where I saw it. It might well have been reported here in the forum, but otherwise it would have been something on the Internet feed. The study was on use of magnetic fields to permit transport over long distances on the Moon, without using moving devices such as wheels.

I'm fairly sure the study was done for NASA, and it may have been published with the NASA logo somewhere in the presentation.

Vehicles that move over magnetic tracks will still need wheels to maneuver at the destinations, but magnetic tracks would reduce wear on bearings.

Magnetic fields are used on Earth for high speed trains, so I assume the proposed lunar application is similar, but it would not have the advantage of high speed motion to build up magnetic force.

(th)

tahanson43206 · 2024-08-22 06:27:57

For Calliban re the difference between sulfur dioxide and sulfur for application on the Moon.

I would like to renew my request for guidance on how to think about using the two materials. You have written in the past about using sulfur as a coolant for nuclear reactors, but I assume that is not what you are talking about in this topic.

Please expand a bit on how you would use the gas sulfur dioxide in a machine. Would it be a substitute for air using on Earth, for a pneumatic tube?

(th)

Calliban · 2024-08-22 07:59:43

Properties of sulphur dioxide.
https://en.m.wikipedia.org/wiki/Sulfur_dioxide

Liquid at 30°C with a vapour pressure of 4.3 bar. It can therefore be pumped into a heat exchanger as a liquid, from a radiator / condenser operating at 30°C. That greatly reduces the required compression power, making the cycle efficient. Critical temperature is 157°C, so no drying equipment is needed prior to putting the gas through a turbine, provided the hot source has a temperature greater than Tc. It is a dense gas with a density of 2.6km/m3 under standard conditions. This allows for high power density power generation equipment.

In the absence of moisture, it will not corrode steel. But it is highly corrosive when mixed with water. That would be a problem in most places on Earth, but is easily achievable on the moon.

Sulphur could have uses as a heat transfer fluid. One problem however is that it reacts with iron to form iron sulphide. So materials compatability might be a problem. But sulphur has the advantage of a low vapour pressure even at temperatures up to 400°C.

Last edited by Calliban (2024-08-22 08:06:50)

tahanson43206 · 2024-08-22 08:09:26

Please keep going !!! for Calliban re #15

Your famous hand drawn sketches would fit in nicely here...

While you're at it, please think about that magnetic road that I mentioned seeing (somewhere). That idea might be adapted to a piece of machinery for individual movement. There would be an outer layer that is in contact with the terrain, and the inside component would contain magnets that would (somehow) expert force on the outer component. In this scenario (assuming it is possible) there would be no joints into which lunar dust could squeeze.

You mentioned a turbine, so I assume you have a heat engine somewhere in the mix, to provide thermal energy to get the process started.

(th)

Calliban · 2024-08-22 08:49:05

Regarding nuclear properties. From what I can see, 32S has a relatively high scattering cross section in the low MeV range.
https://www-nds.iaea.org/exfor/servlet/E4sMakeE4

However, atomic number is high so the average collision will remove relatively little energy from a neutron. Also, a gaseous reactor coolant would have a low number density at temperatures above critical temperature. Thermal absorption cross section is intermediate at 0.5 barns.

So I think SO2 could be used as a direct cycle reactor coolant, maybe for a fast reactor. But great care must be taken to keep moisture out of the core. Any moisture coming into contact with SO2 forms sulphurous acid, which is highly corrosive.

Alternatively, SO2 could be used as a secondary side coolant for a sodium cooled fast reactor. Nuclear properties are irrelevant in that case.

Last edited by Calliban (2024-08-22 08:56:14)

tahanson43206 · 2024-08-22 09:41:16

For Calliban re #17

If I understand post #17 correctly, you seem to have achieved a happy marriage of sulfur and sulfur dioxide in the same machine.

Surely this will make our member Void happy. Void seemed to be worried about low brain thinking occurring in the forum, as compared to the high brain thinking that he shows us every day.

Per Void:

And fyi, I do not like the method of contest as per binary comparisons. It too easily summons the lower mind functions and so then interferes with the higher mind functions.

Hopefully your marriage of the two substances in one machine will ease Void's concerns.

(th)

Last edited by tahanson43206 (2024-08-22 09:43:20)

Calliban · 2024-08-22 11:20:49

I don't think elemental sulphur is a particularly useful heat transfer fluid. Liquid sodium is likely to be a better choice. It has low viscosity, high heat capacity and has good materials compatability with steel. But it boils at 800°C, so is not much good as a power cycle fluid. The primary reason I suggested SO2 was that it can undergo phase change at temperatures and pressures that are compatible with steel power cycle machinery.

tahanson43206 · 2024-08-22 12:52:21

For Calliban re #19

Thank you for catching my unintentional substitution of Sulfur for Sodium in my attempt to remember your posts about reactors.

I found a reference to sodium abundance as 1.33% wt% at iopscience.iop.org.

Wikipedia has the abundance of Sodium at .6%. That value may be reflective of the Apollo missions.

Sulfur does not show up at all in the Wikipedia table, so recent reports of discovery of Sulfur may reflect more recent missions and exploration of other areas.

So my question would be ... is there enough Sodium on the Moon to support a few reactors that use Sodium as a coolant?

For that matter, is there enough Sulfur-Dioxide to support the machinery you've envisioned?

In looking at the table of abundances in Wikipedia "Lunar_resources" it crosses my mind that Oxygen seems ubiquitous, so perhaps oxygen might be considered as a working fluid for pneumatic machinery?

(th)

Void · 2024-08-22 12:57:01

(th) you and I have a problem communicating. So, I wish you well with your efforts, but I think we need to be careful not to trigger each other. I want the best things for this place, but there is a lot of "Lost in translation" going on between us. I will try hard to not lead you astray,

Anyway, your dialog with Calliban is very good, so don't sweat it. Just understand that it is very likely that you do not understand my intentions.

Done

Calliban · 2024-08-22 13:50:49

From Chapter 7 of the lunar source book, Na2O accounts for an average of about 0.6% of lunar regolith by weight. So each cubic metre of regolith contains an average of about 8kg of sodium. Elemental sulphur is 800ppm on average, or about 1.4kg per cubic metre.

Assuming the sulphur is in elemental form, it will be easier to extract than sodium. This can be done just by heating regolith in a vacuum to maybe a few hundred centigrade. The sulphur will sublime. Solar wind gases and argon will be released along with it.

To extract Na2O from regolith, the easiest option would be to dissolve it in water, whereupon it would react to form sodium hydroxide.

Na2O + H2O = 2NaOH.

This can be dehydrated back into Na2O by heating NaOH to high temperature. The pure Na2O can then be used to produce metalic sodium using electrolysis. This is a relatively energy intensive process, comparable to producing aluminium.

I noticed from reading Chapter 7 that lunar regolith contains a proportion of pure reduced metallic iron. This appears to originate from ilmenite, which is FeTiO3. Micrometeorites impact dust grains in the regolith. The impact heats these grains to extremely high temperatures. Solar wind deposited hydrogen then reacts with ilmenite reducing it to a mixture of metallic iron and titanium dioxide. The iron exists as microscopic spheroids on the surface of mineral grains. This has been going on since soon after the moon's creation, allowing substantial buildup of reduced iron in the regolith. The significance of this is that pure iron can be harvested from regolith using a magnet. We do not need an energy intensive smelting process to make iron on the moon. Nature has done this for us. Presumably, the same is true on a lot of asteroids as well.

Last edited by Calliban (2024-08-22 14:03:34)

Calliban · 2024-08-22 14:16:51

Re use of oxygen as a working fluid. This could have applications. The obvious weakness of using oxygen as a power cycle fluid is that its liqurfaction point is cryogenic. So a practical O2 power cycle must deal with O2 entirely in the gas phase. This makes an O2 power cycle relatively bulky and inefficient. But it coukd have niche applications. Inside habitats, we need to scrub out CO2 and replace O2 as humans consume it. One possibility is to use compressed O2 to drive tools, with the leakage O2 gas used to replenish the O2 that humans are consuming. The average human consumes 0.8kg of O2 each day.

Assuming we release this from 10bar and expand it adiabatically to 0.33bar, then some 100KJ of mechanical energy can be released per person per day.

I think ultimately storing energy in SO2 will be more efficient, as it can be stored as a dense saturated liquid. But it is toxic, so it cannot be released into a habitable space. We would need to capture the gas in a vessel, and then recompress it when surplus power is available. The use of SO2 would allow solar power facilities to continue generating power over the lunar night. During the day, solar heat could be stored in rock piles on the surface, reaching temperatures of 200 - 300°C. During night, this heat is recovered and used to raise hot pressurised SO2 gas in boilers. This gas drives turbines, generating power. The condensor will be iron radiator panels on the surface. The SO2 will condense back into liquid at a temperature of 30°C and pressure of 4.3bar. The liquid drains into a well, where it is extracted by a pump and reinjected into the boilers.

This is a form of stored thermal energy. SO2 has ideal fluid properties for a relatively low temperature rankine cycle like this. The low critical point of 157°C makes it easy to superheat SO2. The compact turbine is a significant economic advantage. SO2 toxicity and corrosivity in contact with moisture would make this impactical on Earth. But lunar conditions allow it to fill a niche. Assuming a boiler temperature of 200°C and a condensor temperature of 30°C, Carnot efficiency would be 56%. We can expect to get about half carnot efficiency in small machines generating a few MW. This would rise to 75% for GWe scale powerplants.

Base case. Suppose we want a machine that can generate a constant 1MWe of power for large base, over a 14-day lunar night. How big would the rock pile need to be?

Assume basaltic rock has density of 3000kg/m3 and a specific heat of 0.8KJ/kg.K. During the day we heat it up to 300°C. During night, we extract heat until temperature drops to 200°C. Each cubic metre of rock can store:

Q = 3000 x 800 x 100 = 240MJ of heat.

Lets assume that 30% of this is turned into electricity, or 72MJ (20kWh). To provide 1MWe for 14 days, we would need 16,800m3 of rock. That is a cube some 26m (83') aside. Which is quite doable. The best approach is probably to store heat in bore holes some 100' deep. The upper layers of regolith then provide the insulation needed. We would build a set of parabolic trough collectors directly over the storage area.

Last edited by Calliban (2024-08-22 15:10:27)

tahanson43206 · 2024-08-22 15:13:19

For Calliban re #22

Thank you for taking up the possible use of oxygen as a fluid for pneumatic tools... It sounds to me as though the idea is not necessarily as attractive as i had hoped. On Earth, ordinary air is used for pneumatic tools. Earth air contains nitrogen as well as oxygen. Is your hesitation based upon the absence of nitrogen?

I don't know enough about the way the gases function (separately and together) to make even a guess.

(th)

Calliban · 2024-08-22 15:50:29

Oxygen is quite valuable. Assuming we extract oxygen by reducing iron (II) oxide, then we need about 20MJ of electrical energy to produce 1kg of oxygen. That is over 100x more than we get by passing that 1kg of O2 through an air tool. It really isn't affordable to use oxygen to transmit power if we are bleeding it off into space. We could capture the oxygen into some low pressure store, recompress it later and use it over and over again. But that implies a huge pressurised volume just to store exhausted O2. By contrast, bleeding the oxygen into a hab space and drawing power from the expansion wastes nothing. But the useful power that can be generated in this way is limited by the breathing rate of the people in the hab. However, it is still valuable to have this option. Hand tools that are powered by compressed air are much easier to make than their electric equivelant. So for low power applications, compressed O2 could be valuable.

Last edited by Calliban (2024-08-22 16:09:50)

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