New Mars Forums

quasar777,

How about a true "iron horse"?:

quasar777,

I think this is the basic concept, but this type of vehicle could be ridden while wearing a space suit:

Island Victory is one of the most powerful tugboats in the world, with 42,880hp worth of installed engine power.  The props on tugs like this are nothing too spectacular when it comes to propulsive efficiency, perhaps 65% efficient at converting shaft power into thrust.  That's a necessary concession to high-thrust at low-rpm, frequently accomplished using ducted propellers that don't perform very well at higher speeds.  The prop design can't and won't be optimally efficient at all speeds.  Even variable-pitch props don't produce as much thrust at low speeds as ducted props, which is why tugs frequently use ducted props.  You have to design to a given criteria set, same as an aircraft propeller.  Efficiency will be very important for a tug using batteries, liquid air, or other forms of natural energy, all of which have far lower gravimetric and volumetric energy density than hydrocarbon fuels.  Larger diameter props do help with that, but there will be draft limits, especially within inland waterways.  The Sharrow prop design could help reduce diameter while maintaining thrust, without the use of a thrust-robbing duct at higher speeds.  Large diameter props also cost a lot more, but so do Sharrow props.  The hull forms used by modern tugs are already pretty close to ideal for their intended applications, although rudders are optimized to minimize thrust sapped from the prop(s).  Perhaps the new weldable Mangalloy steel plate developed by the Japanese and South Koreans would allow liquid air to be carried within a "double hull", similar to LNG, at more reasonable material and fabrication cost, as compared to stainless, and with fewer corrosion / pitting issues, which is why no ocean-going ships use stainless hulls.

To a point, top speed is far less impressive for a tugboat than pure "pulling power" at speeds below 10 knots.  However, the ability to tow ships in for repairs will likely be affected.  For starters, you cannot sail at any speed you please, into or out-of a port facility, nor within the confines of restricted inland water ways.  Power required also increases dramatically as speed increases, so travel at lower speeds is advantageous to total cost, provided that personnel and equipment costs don't exceed fuel costs, whatever said "fuel" happens to be.  4,000hp might be plenty for low speed travel, but it will affect the bollard pull of a tug.  This implies more tugs, more powerful motors / engines, and/or shorter operating times at full power.  That said, 10 knots was well above the speed at which we would approach congested ports aboard an aircraft carrier, which somewhat counter-intuitively, is now a much smaller ship than many of these new super-massive cargo and tanker ships requiring tugboat assistance to navigate from / to a pier.

If we're serious about using liquid air as a viable marine fuel, then we need to create ocean-going barges capable of station-keeping, operated along common shipping lanes, able to perform liquid air transfer to ships underway, to refuel cargo and tanker ships.  The US Navy calls this "UNREP" (UNderway REPlenishment).  Each ship in a battlegroup typically has an UNREP event scheduled once or twice per week.  This adds cost, but allows for continuous semi-autonomous operation at sea, without the need to visit a port.  The barges will likely use some form of wind and/or solar power to suck in, filter, compress, and liquefy the air.  As ships pass through, they will come alongside the barge, take on a fresh load of liquid air to continue their intercontinental transits.

Large scale liquid air energy density is around 125Wh/kg of usable energy, which could be doubled or perhaps tripled with an onboard load of molten salt.  Diesel fuel burned in a very large low-speed marine engines, which are about 50% thermally efficient, provides 6,250Wh/kg, so 50X greater usable energy density.  I've seen Aluminum-air batteries with energy density figures quoted at up to 2,500Wh/kg.  Lithium-ion batteries are around 300Wh/kg at the cell level, but not at the pack level, and some packaging is still required to inhibit the worst effects of a thermal runaway and to move large strings of cells as a singular unit.  Iron-air and modern Lead-acid batteries have very similar energy density.  You can't make a ship's energy supply 2.5X (Aluminum-air batteries) to 50X (liquid air) heavier and still expect the ship to be roughly the same size or to perform similarly.  The "super-sized" tugs referenced in the article would quite literally be the same size as WWII era battleships, meaning 25,000t to 40,000t, not tugboats.  Succinctly, no amount of efficiency improvement can overcome energy deficits of that magnitude.  Diesel engines and diesel fuels remain the workhorses of the entire modern world for a reason.  Thus far, no other energy generation and storage technology can match the combination of characteristics they provide.  The end result will be more costly ships with less range and cruising speed capability, which implies a requirement for many more ships and the support infrastructure to complete the same transportation and maneuvering tasks.

The only kinds of emission-free ships capable of covering economically-useful distances are, in point of fact, ye olde wind-powered sailing vessels.  The modern "take" on classical sailing ships involves using a 1,000m^2 technical fabric "kite" tethered to the bow of the ship and flown at an altitude of 300m, using an automated computer control system to model wind and ship behavior.  This provides roughly 100,000kg-f of propulsive power, using average wind speeds.  It does not require tall heavy masts to hold sails.  A pay-in / pay-out device similar to a capstan is used to control said device, using deck space that is typically clear / available on most cargo and tanker ships.  To deliver 100% of the force required to achieve top speed using its diesel engine, the Emma Maersk container ship, a very large vessel, even by today's standards, requires a bit over 7.5MN of force to sail at 24.5kts, so the sailing kite's surface area becomes 7,648m^2.  The giant diesel engine and fuel cold be replaced by a nominal quantity of liquid air for electrical power generation and maneuvering near ports.

SeaWings "Kite" Deployment:

Flying this "kite" at altitude permits access to higher average wind velocity:

Bar Technologies uses both Aluminum 37.5mH (750m^2 / 200t per sail) and composite 20mH to 24mH 3-element sails (<30t per sail), which achieve greater lift than single element rigid sails using a fowler flap design similar to that used by commercial airliners:

I watched an entire YouTube video on this with Randall Carlson.  This is a very interesting object with unusual physical properties.

I'd like to point out that the landing gear on the Falcon 9 / Falcon Heavy boosters are 100% CFRP structures, with a white thermal barrier protective coating, presumably some kind of thermal spray ceramic coating.  Landing gear absolutely counts as a high stress load-bearing structure, one expected to survive a landing so hard that it permanently deforms an Aluminum crush tube contained within each hydraulic strut upon landing.  Moreover, the outer-mold-line for that gear is markedly different from the Falcon's Al-2195 propellant tank, which ensures that they also experience some brief localized shock impingement heating.

To wit, Falcon's CFRP landing gear components have repeatedly survived both the peak heating impulse caused by plunging back through the thicker lower atmosphere following their Mach 6 burnout velocity, plus some minor impingement of the engine plume upon restart for retro-propulsion.  A Merlin engine is nowhere near as powerful as a Raptor, but it's still briefly bathing the underside of the booster in a sheet of white-hot flame.

My assertion, which should not be too controversial, is that the booster cores for both Falcon and Starship rockets could be fabricated from CFRP consisting of IM7 fiber bound within a PBI matrix, with a thin thermal barrier coating applied, which should result in virtually no loss of base material tensile strength associated with peak heating.  Al-2195 Aluminum-Lithium alloy (82ksi with a T8 temper) and 304L stainless (30.5ksi according to MatWeb, possibly up to 42ksi for slightly modified alloys) or similar alloys are very weak materials compared to IM7 (800ksi for the fiber, 395ksi in a typical composite using 8552 resin, given a typical 60/40 fiber-to-resin ratio, by volume).  Said resin is weaker than PBI, so my presumption is that a 60/40 IM7-to-PBI composite would be modestly stronger.

IM7 composite is 9.4X to 13X stronger than 304L and 4.8X stronger than Al-2195-T8.  All known metal alloys, irrespective of type, are W-E-A-K compared to this "garden variety" aerospace structural CFRP, fabricated using the modern method of using automated fiber placement machines, aka "tape winding machines", laying down unidirectional fiber tow / roving / tape.  That said, we will still use metal for the thrust structure, 300M (turbofan engine mounts for airliners) or Aermet VIM/VAR steels (more exotic, but considerably better YS than 300M or Ti-6Al-4V, though more expensive than either by a wide margin) or Ti-6Al-4V (common enough here in America, where there is extensive Titanium forging experience for military aircraft and government spacecraft).  For commercial rocketry, I would bet on 300M, but government rockets frequently call for carefully designed Titanium mounts, such as that used by the Space Shuttle.  Use of the described materials has become a fairly well accepted industry standard practice in aerospace because it's so exhaustively well-proven at this point.

NCAMP / NASA Material Qualification Report for IM7 (uni-tape)/8552 composites:
Hexcel 8552 IM7 Unidirectional Prepreg 190g/m^2 & 35% RC Qualification Material Property Data Report

Unidirectional IM7 tape / tow / roving, laid down by an automated fiber placement machine, followed by hot mold curing using PBI, is what I'm proposing.  This is how high temperature / cryogenic temperature capable composite propellant tanks could be fabricated.

HexCel HexTow IM7 Carbon Fiber Product Data Sheet

HexCel 8552 Resin Matrix Product Data Sheet

As the data sheet shows, 8552's tensile strength is 17.5ksi.

PBI exhibits a tensile strength of about 32ksi when used as the matrix in CFRP composites, or 23ksi for the neat resin.  IIRC, PAI is one of the strongest "neat" polymers, around 28ksi without any fiber reinforcement, but only rated to 500F service temps.

Any composite capable of 800F service temps without meaningful weakening is more than good enough for a booster stage.  A good thermal barrier coating means the composite can survive transient 1,000F+ aerodynamic heating associated with Mach 5 to Mach 7 burnout velocity without permanent weakening of the composite structure.

Thermal barrier coating for carbon fiber-reinforced composite materials

Porous Thermal Barrier Coating Formation Technology for Carbon Fiber Reinforced Composites through Flame Spraying

All those yellow areas shown are high temperature composite parts.  On the side facing the engine, they have thermal barrier coatings applied, in addition to high temperature capable resins.  Hot bleed air from the turbine flows around the nozzle, to help mask the thermal signature from the far hotter exhaust flow from that giant F-135 engine.

Here's a good shot of the nozzle:

That saw-tooth pattern you see on both the nozzle itself and the composite skin does more than merely reduce the radar return.  It also aids in mixing and acoustic signature reduction.  On the composite skins you see on the jet engine nacelles of the most modern commercial airliners, it's deliberately used to reduce engine noise.

NASA Helps Create a More Silent Night

Anyway...

Material Data Sheet for the Cycom 5250-4 Resin System used in the high-temp BMI composites near the F-135's hot section:
CYCOM® 5250-4 PREPREG SYSTEM

Max service temp is only 450F, but take careful note of how those aforementioned thermal barrier coatings can drastically reduce temperature and damage to the resin matrix.

Proof Research is a maker of CFRP over-wrap firearms barrels and they also fabricate the hot section composites for the F-35.
PROOF Research - May 18, 2016 FaceBook Posting

Gun barrels get really freaking hot, much like the engine casing of that gigantic F-135 engine.

All that said, I promised GW to provide a link to a 1,000F capable (intermittent service use) "resin", used in high-temp CFRP applications:

Wikipedia:
Polybenzimidazole

It was first synthesized in 1949, by the Material Laboratory of Wright Patterson Air Force Base, which is why I'm a little surprised that this keeps getting questioned.  That said, full synthesis of the material we use today was accomplished in 1961.  NASA contracted with Celanese to use PBI in the space suits used in the Apollo spacecraft, following the Apollo I fire.  Today, the company originally created to make PBI-based polymers, named "Celanese", operates as PBI Performance Products, Inc.  The Space Launch System 5-segment solid rocket motors use PBI plastic

In 2016, NASA qualifies the use of PBI in the insulating compound for the reusable and largest solid fuel rocket motor ever built for flight - the Space Launch System Five-Segment Booster.

This NTRS Report dates back to 1971, in which PBI composites were studied for Space Shuttle Program TPS:
STUDY AND PRODUCTION OF POLYBENZIMIDAZOLE BILLETS, LAMINATES, AND CYLINDERS - Prepared by LOCKHEED MISSILES & SPACE COMPANY

Said study describes tests performed on PBI-infused carbon cloth "laminates" (CFRP by another name) materials.

In 2025, for a thermally-protected spacecraft propellant tank structure, we'd probably use IM7 fiber as government-furnished material (no choice, because it's what NASA and our aerospace primes have on-hand, meaning no ultra-high tensile strength T1200 fiber), get a specialty PBI resin from a company that makes it, use an aerospace prime to fabricate the part (Boeing or Lockheed-Martin or Northrop-Grumman), and then we'd hire a specialty company to apply a highly uniform ceramic thermal barrier coating (expensive but necessary).

tahanson43206,

This weekend I should have some time to address the banned users issue.

There's a major difference between the difficulty of confining a plasma long enough to use it to generate baseload electricity vs the far lower relative difficulty of intentionally allowing said plasma to escape from its magnetic confinement chamber to generate thrust.  The technological bar to clear for generating electricity using fusion, in a manner similar to a fission reactor, is monumentally high.  The bar to clear for achieving thrust has already been cleared.  There's no question that using fusion to achieve thrust actually works.

When MSNW LLC did the initial development work on the concept, they proved that all major components worked to the degree required, but then NASA immediately pivoted to something that looked better in theory, namely continuous thrust generation from continuous fusion power, but continuous fusion requires long term plasma confinement, similar to a conventional Tokamak.  That's the part we cannot yet do in a practical manner- fusion that generates net positive electrical output to use as input for a self-sustaining reaction.

Why did they do that?

NASA is focused on science, not producing tangible usable things like a pulsed fusion drive as an enabler for their own exploration missions.

That's the best answer I can come up with.

GW,

CFRP's strength can be improved and porosity reduced using a method known as "Carbon Forging", which was pioneered by Lamborghini.  The process combines extreme heat and pressure.  A French Company named Duc Helices makes propeller blades for light aircraft and helicopters using this method.  The "forging" process takes less than a minute, sometimes only seconds, and can be used with chopped fiber, fabrics laid by hand in a mold, or roving/tow which has been laid down using an automated fiber placement machine, which is how CFRP rocket propellant tanks are made by companies like Rocket Labs.  IIRC, at least one company makes high performance CFRP wheels / hubs for sports cars this way.  They use a combination of fabric, chopped fiber, and roving / tow, all in one part.

Reliable Energy Intensity Estimation
Global average steel making energy intensity is 19.76GJ/t (19.76MJ/kg).  Rather than using the absolute best figure achieved, which is what our photovoltaics / electric wind turbines / batteries enthusiasts typically do, I think using a global average energy intensity value is far more appropriate, since steel will inevitably be sourced from wherever it's available.  Steel is a staple construction material, one for which we have detailed energy intensity data publicly available because it's not considered proprietary knowledge.  At 31.4kg/m^2 of solar thermal collector array, using 2mm thick stamped sheet steel mirrors and tubing for structural support (does not include the steel rebar in the foundation), the embodied energy for the steel is 620.424MJ/m^2, or 172,351Wh/m^2.  Steel mirror support structure is identical to "tube-and-fabric" light aircraft structure.

Design with Sophistication, Operate with Simplicity
At least one company holding a contract with NREL ran an AI-enhanced computer aided engineering program for optimizing support structure geometry to minimize mass and cost.  The end result was that support mass was about equal to mirror mass, using a welded tubular steel support structure.  This was done for 5m to 10m width parabolic troughs with single-axis Sun tracking, not the gigantic perfectly flat "billboard" mirrors used by solar power towers.  My assumption is that the bulk of generated power will come from the most simplistic and user-friendly solutions.  Advanced economies can afford to invest additional material and monetary resources into solar power towers, where the overall efficiency of the solution might matter more to them, at the scale they require.  For all solar thermal component designs, multiple examples of full scale hardware are built and tested, then operated within a functional power plant, typically for at least a year, but often for multiple years to evaluate durability.  Thus, very little extrapolation of potential future performance is required.  For photovoltaics, very small sample quantities are subjected to a battery of standardized tests, which is fine and desirable, but this testing tells you very little about broader context of mass production because it's frequently singular wafer special production runs in a lab, with minor variations for test purposes (also good to have), because scale-up frequently entails building a brand new factory to efficiently fabricate at scale.  Real world performance is highly dependent upon process control and testing to minimize rejection rates, equipment in the factory which has a major effect on said rejection rates, the competence of the installation crew, and site selection.  I've had an electrical engineer, a certified electrician with over 20 years of experience who specializes in commercial photovoltaic panel installations, and run-of-the-mill rooftop panel installers all show me the results of amateur hour in plant design.  They all spoke of spending days to months of rework to salvage poor quality installation work.  The consensus is that pure mechanical assembly tends to be less error-prone than a combination of mechanical / electrical / electronic assembly, because less knowledge and experience is required.

Expect Similar Energy Intensity for Solar Thermal and Photovoltaics
You have to add more energy for a steel-reinforced concrete support structure, but this also applies to roughly equally heavy photovoltaic panels with single-axis Sun tracking.  Photovoltaics still use support tubing and reinforced foundations.  Getting back to mirror design, a polished hot-dip Aluminum coating is also required.  That adds even more energy to the final total for the mirror, because there are no free lunches here or anywhere else.  There's a real energy cost to every concession made to design efficiency.  The Aluminum coating is corrosion-resistant, which is why it's applied to factory automotive exhaust tubing and mufflers, and highly reflective after polishing.  Surface finish quality of the steel greatly affects reflectivity, hence the use of a cold-rolled product.  An electronic or mechanical sun tracking mechanism is also required for each mirror assembly.  Troughs are typically rather long, but can be assembled onsite from smaller sub-assemblies for ease of transport.  The net-net is that the total mass of materials for parabolic troughs, in a real world plant, is remarkably similar to real world commercial photovoltaic farms.  Total embodied energy will be lower, but only modestly so.  There is, however, a radical difference in the embodied energy of thermal vs electrical energy storage in electro-chemical batteries.  The major difference between mirrors and photovoltaics is service life before unacceptable degradation occurs, the kinds and abundance of materials required, the use of field repairable vs factory replaceable technology units, and ease as well as completeness of recycling.  All similarities between mirrors and photovoltaics end there.  As previously stated, the Silicon that comes out of photovoltaics recycling is not readily usable in brand new photovoltaics, because the energy intensity of photovoltaics recycling significantly exceeds that of mining and refining virgin materials.

Supply Chain Management
Types of materials required by solar thermal generation and storage tend to involve very simple manufacturing processes by way of comparison to photovoltaics / control electronics / wiring / power transformers, so the supply chain is much shorter.  Complete onshore manufacturing of stamped steel is possible for major economic powers.  Materials and components don't need to crisscross the globe multiple times.  Transport energy is lower as a result.  The steel stamping / welding / hot-dipping equipment is far less energy-intensive per kg of finished good.  All electronic devices require extensive supply chains.  A myriad of highly specialized facilities are required to fabricate Silicon wafers and power electronics equipment.  No single country contains all the materials or hosts all the facilities for photovoltaics and electronics manufacturing.  There is such a thing as a purely mechanical dual-axis Sun tracker that uses solar thermal power to deliver torque to the mirror array.  No control electronics are required until we arrive at the single electric generator and step-up power transformer.

Plant Security and Assurance of Supply
The most sophisticated hackers in the world will have a very difficult time affecting a mechanical solar thermal or mechanical wind turbine plant.  Their ability to affect operations inside a solar thermal plant itself is near-zero without direct physical access.  If the Sun is momentarily masked by clouds, all that built-up thermal inertia continues to drive the turbine and electric generator.  Solar thermal plants can also include 8 to 16 hours of onsite thermal energy storage provided by tanks of pulverized rock or molten salt, because it's cost-effective to do.  Only large storage tanks of heated material are required.  That means generation doesn't end entirely at sunset.  Strictly speaking, given sufficient onsite thermal energy storage, no complete backup power plant is required when collection ends at sunset.  In large installations, the temperature delta between start of stored energy consumption at or near sunset and resumption of collection at sunrise, varies by less than 1C.  It's similar to a nuclear power plant in that regard, but without the security requirements.  If you managed to get your hands on some molten solar salt, apart from burning yourself, what else could you do with it?  Perhaps most importantly, the entire grid can't crash the way Spain's grid did, due to the fact that purely electrical photovoltaics and wind turbines provide zero grid inertia.  Vertical power spikes and drops are only possible when the turbine, electric generator, or step-up power transformer catastrophically fails.  That greatly simplifies grid operation.  Even if you did eventually have to burn some fuel due to seasonality or catastrophic equipment failure, you have hours to perhaps days to spin-up natural gas turbines, which means they don't need to run in the background 24/7/365.  You only run them for supplemental winter power.

Solar Thermal Materials Details
Cold-rolled steel and steel-reinforced concrete are the primary materials required by solar thermal, plus a small amount of Aluminum applied using the exact same technology required to create typical factory automotive exhaust tubing and mufflers (stamped and welded cold-rolled sheet steel hot-dipped in Aluminum).  The total mass of materials required per square meter of mirror surface area is not significantly more or less than the mass of materials required for photovoltaic panels.  There are no existing materials limitations when it comes to delivering enough steel, concrete, or commercially pure Aluminum coating.  We don't need to wait additional decades to centuries to acquire enough high purity Silicon, Copper, Lithium, Aluminum, rare earths (for the control and power inverter electronics) from extraction.

Materials Recycling Processes
The recycling process for Aluminized steel involves heating the shredded sheet metal to melt-off the Aluminum coating, and then stuffing the now-uncoated shredded steel back into an electric arc furnace.  Presumably, most of the Aluminum and steel can be recovered.  I'm not entirely familiar with the process used to recover concrete.  My understanding is that ground-up / powdered concrete can be and presently is mixed into fresh batches of concrete, but like so many other composite materials, it's not 100% recyclable into brand new concrete, strictly-speaking.  The steel rebar can be recovered and recycled at near-100% rates.

Solar Thermal vs Photovoltaics Service Life
A photovoltaic array has meaningfully faster degradation over time than a much simpler polished metal mirror, thus a shorter useful service life.  Metallic mirrors can easily last for a human lifetime, possibly several lifetimes with periodic re-polishing.  Some of humanity's oldest mirrors, made from materials like obsidian, predate our discovery of metallurgy.  Metal mirrors with corrosion protection should last at least 3X longer than photovoltaics.  In a very hot and dry desert, only scratches will degrade mirrors over meaningful timeframes.

I can simplify this obviously contentious issue to a pair of YES/NO questions:

1. Is 10 years of global (at 2024 production rates) steel, commercially pure Aluminum (the only kind that comes directly from the smelter), concrete, and solar salt or crushed rock production enough to deliver the solar thermal collector surface area, or mechanical wind turbines to compress air in places that are not sunny, plus 28 days of thermal and air energy storage to account for seasonality, enough to provide 70% of humanity's Total Primary Energy Supply?

2. Is 10 years of global (at 2024 production rates) high purity polySilicon, Copper, Aluminum, Lithium, and rare earth metals production enough to produce the photovoltaics, electric wind turbines, electronic control systems, and electro-chemical batteries for fast storage, to store 28 days of electrical energy to account for seasonality, enough to provide 70% of humanity's Total Primary Energy Supply?

Allowable Concessions to Dreamers
I'm perfectly willing to concede that potential future advances in photovoltaic and battery tech may be able to do what has thus far proven functionally impossible, provided that you are able to supply realistic materials demands estimates for all required materials.  If you can't do that, then there's nothing to compare.  You're presenting a fever dream with no numbers to evaluate.  We don't judge merit on the basis of "nothing".  In point of fact, we would say that "nothing" is entirely without merit, therefore any argument over the future potential of nothing is without merit.  It's entirely belief-driven, much like religion.  Maybe it will work beautifully, or maybe it won't, but nobody actually knows, so why are we pursuing religion when our problems are math-based?

The arguments put forth by our photovoltaics / electric wind turbines / batteries enthusiasts are exactly like debating the merits of man-made fusion reactors.  Thus far, no self-sustaining made-made fusion reactor exists.  We don't know if it's even possible because nobody has been able to make it work.  Fusion is another future technology with potential, nothing more.  Any argumentation over what it might potentially provide is without merit.  Do the hard work to create a fully functional example of the tech first, and then we'll know what merits it does or doesn't have.  I'm not going to bet the future prosperity of my children on tech that doesn't actually exist.  No sane and rational parent would tell their child to simply "believe" that everything will work itself out, without a pointed admonishment about putting in the work to make sure it does happen.

I have materials consumption figures from actual solar thermal installs, which were helpfully compiled by US DoE and NREL, to use as sanity checks for my materials demand estimates.  I don't need to dazzle anyone with futurism "nothingness" when I can show real numbers for real machines that produce reliable power.  Opportunistic power seems to provide an irresistible temptation to people who deal in possibilities, rather than probabilities.  Business and government operates primarily on probability.  The US federal government spends some money on maintaining nuclear weapons on the basis of the rather low probability but high impact of a nuclear war.  It spends many many more dollars on conventional fighting forces, because all wars to date have involved a lot more shooting than nuking.  That's why track record and trust through reliable action are so important to business and government.  They'll give you a golden opportunity, but then they expect you'll show up to do the work.  That's what our "all-electric dreamers" have failed to do thus far.  When it comes to sourcing the wish list of materials to put their ideas into practice, they think belief or possibility or "the market will figure it out" is an acceptable substitute for demonstration.  I've seen no practical demonstration of a grid run primarily on their favored technologies.  All the examples they point to are back-stopped by hydro dams, nuclear reactors, or coal / oil / gas.

Void,

Photovoltaics of the 2010s, which were about 15% efficient, used 99.99999% pure Silicon.  Photovoltaics of the 2020s, which are 25% efficient, use 99.999999999% pure Silicon.  99.999% pure Silicon may allow you to create photovoltaics with 10% conversion efficiency, which may be fine for use on the lunar surface because there is near-zero atmosphere.  40% efficient triple-junction photovoltaics do not use 99.999% pure Silicon.  Add another eight "nines" to the end of that purity value.  Greater efficiency comes from much higher purity materials, exponentially more energy input, and more exotic materials.

Blue Origin's electrolysis furnace is innovative, but much like Boston Metal's electrolysis-based steel making process, it does in fact use significantly more energy.  That is a mathematical certainty, not a guess.  We've had electrolysis cells for high purity metal production for many decades now.  All that fortified food made here in America uses extreme purity Iron created through electrolysis, but there's a massive energy cost to producing it, which is why it's more expensive than Pig Iron and steel.  The energy input into Blue Origin's electrolysis cell, per kilo of metal produced, is conspicuously absent from their fluff piece.  If they had something truly remarkable, they'd be monetizing it.  The metals smelting industry would be throwing money at them.

To their credit, Boston Metal has been completely honest and very public about the fact that their CO2-minimized steel making process uses more energy than traditional Blast (Pig Iron) and Basic Oxygen Furnaces (steel).  They're producing the same steel product at the end of the day, but it's more energy-intensive.  The principle benefit is greatly reduced CO2 emissions, which is a worthy goal, but the implication of what consuming more energy means is that more energy of ALL TYPES (which includes hydrocarbon fuels) will be consumed.  Shifting where the CO2 gets generated doesn't change the fact that it's still being generated.

The reason engineers used Carbon in so many reduction processes is pretty simple.  Carbon drastically reduces the input energy for metal ore reduction.

The reduction zone in the blast furnace, where Iron ore undergoes reduction reactions, takes place between at or under 1,000C.  The hearth zone of the furnace where molten Iron is collected, is heated to at least 1,600C.  Pure Iron melts at 1,538C.  The blast zone can be much hotter, since forced air induction is used to ignite the coking coal.

The Hall-Héroult process takes place just below 1,000C, and the use of a cryolite bath and Carbon anodes is what allows Aluminum smelting to take place at this temperature.  Even at Al2O3's boiling point, which is just shy of 3,000C, Oxygen will not thermally dissociate from Aluminum, because the bond is so incredibly strong.  There are other methods for making Aluminum, all of which consume a lot more energy.

Silicon melts at 1,414C, but quartz is heated to at least 1,500C, so the 1,600C reduction temperatures mentioned in the article seems like a plausible value to me.

If regolith is simply scooped up off the lunar surface and dumped into an electrolysis furnace, whereupon every kilo of regolith is heated to 1,600C, even though not all metals need to be heated to that temperature extreme for reduction, then by definition you're using a lot more energy to do that.  After you produce liquid metal, then you need selective high temperature separation methods to produce the various different kinds of metals you want.  That issue is created by deliberately starting the process with a hodgepodge of different oxidized metals, rather than locating deposits of high grade ores, separating them using a grinding and flotation process, and then proceeding with reduction.

All parts of the metals extraction and refining processes were deliberately optimized by engineers to reduce energy consumption.  We don't use targeting of rich ore grades / grinding / flotation, "just 'cause".  We don't extract Lithium from sea water for the very same reason.  When compared to chemical reaction methods, every electrolysis process I'm aware of consumes more energy to produce the same end product.  We do tend to use electrolysis when high purity and excellent temperature control is required.  There are real benefits to using electrolysis, but energy efficiency is not one of them.  The Hall-Héroult process is an electrolysis process, but we use it in conjunction with heating and a chemical (cryolite) bath to reduce the reduction temperatures.  This assertion of fact applies to Iron, Aluminum, and Silicon.  It may not apply to certain technology metals.

If electrolysis was energy efficient, then we'd already use it to produce most metals.  It's not, though, and that's why we don't use it to produce metals, unless required, as is the case for Aluminum smelting.  There are no "free lunches" to be had here.  Nobody here wants to hear that, but it's still true.  Once again, hope is not a valid systems engineering strategy for creating the next generation of the largest machines humanity has ever created.  If you want to use natural energy sources, then you have to stop fixating on electrical technology and start understanding how energy is actually used, and then accept that only low energy input and readily recyclable materials are suitable to task.

Humanity's 24/7/365 energy consumption is about 20TW, so 70% is 14TW.  Existing photovoltaics will require 311.808Mt of polysilicon to deliver a constant 14TW.  Photovoltaics are currently produced using High Purity Quartz (HPQ) sand.  Global annual production is about 1.6Mt, excluding the highest purity quartz used in microchips.  Kerf, which is primarily generated by sawing polysilicon ingots into wafers, results in a loss of about 40% to 55% of all the polysilicon produced, even though it's recyclable and is mostly recycled.  Global annual net production of polysilicon for photovoltaics is therefore around 0.96Mt (960,000t), best-case scenario.  In reality, kerf consumes 50% of total polysilicon production for 0.5mm thick wafers, so 0.8Mt/year is available.  A 1m^2 photovoltaic panel made from 0.5mm thick wafers contains about 1.16kg of polysilicon.  That means it would take almost 390 years, using 2024's polysilicon production rates, to create enough usable polysilicon to deliver that constant 14TW.  Unfortunately for us, photovoltaics only last for 25 to 30 years before significant capacity (defined as 20% or more) is lost.

If average photovoltaic panel efficiency is 25%, then 1m^2 of photovoltaics generates about 1.25kWh/day (1,000W/m^2 * 0.25 * 5hrs per day).  Humanity's daily Total Primary Energy Consumption is about 336TWh (14TW * 24hrs), which means we need 268,800,000,000m^2 (336,000,000,000,000W / 1,250W/m^2) of photovoltaics to deliver equivalent constant power using 5 peak generating hours per day.  Any extra power generated during off-peak hours will likely be devoted to polysilicon production since we don't have enough HPQ.  At 1.16kg of polysilicon per square meter of photovoltaic array, we will need 311,808,000t ((268,800,000,000m^2 * 1.16kg/m^2)/1,000) of polysilicon.  Any theoretical efficiency gains over combustion will be immediately offset by vast additional production demands using lower purity materials or sub-optimal materials.

311,808,000t / 800,000t per year (2024 polysilicon production rate, minus 50% kerf)  = 389.76 years of polysilicon production at 2024 production rates, presuming 0.5mm thick wafers

What is high purity silica quartz sand, its main mine and manufacturers

We do recover and re-cast almost all of the kerf generated by sawn ingots of polysilicon, so that's good news, but both production capacity and proven HPQ reserves are sorely lacking.  However, we don't have enough Copper for the fast storage batteries, nor do we have enough HPQ to come within a country mile of supplying most of humanity's Total Primary Energy Consumption, by primarily using polysilicon-based photovoltaics and Lithium-ion batteries- the only technologies in mass production at the present time.

Can we use lower grade Silicon-bearing ores?

If you don't care about the energy input, anything is possible.  We'll be forced to do that fairly soon if we significantly ramp-up production rates.  There will be an exponential rise in energy consumption to refine lower grade quartz sand to the degree required, but it could theoretically be done with considerable effort and energy expenditure.

The lack of materials abundance, as it relates to current photovoltaics, wind turbines, and batteries technologies, doesn't bode well for them becoming the dominant energy source in the foreseeable future.  We need 390 years of 2024 polysilicon production, which requires more HPQ than exists in known reserves, plus more Copper than exists in known reserves to provide 28 days of fast storage, in order to deliver the first batch of Gen III solar and battery tech at sufficient scale to mostly displace hydrocarbon fuels.  Certain rare earth metals used in electric wind turbines require thousands of years of production at current rates, making them even less practical in some ways, though much better in others.

Existing PWRs like the AP-1000 design, Gen II solar thermal, and Gen I mechanical wind turbines, are looking like the only near term realistic solutions for displacing most hydrocarbon fuel consumption.  All Gen III tech is severely materials limited at the present time.  CO2 emissions keep going up every year because current Gen III tech cannot offer sufficient capacity for significant displacement of hydrocarbon fuels.