Internal combustion engines for Mars

SpaceNut · 2020-12-22 19:37:48

Aluminum oxidizes quite easily and while stainless steel is low it will in time corrode if moisture is present with any chlorides which mars has a ton of outside of the habitat to move about but a stationary engine would see less and we can give a wind shield to keep the soils from sand blasting the engine.

https://advancedplatingtech.com/blog/co … l-plating/

Electroless nickel plating can provide a robust solution to corrosive attack across a range of corrosive mechanisms including galvanic corrosion, chemical attack and erosion. Electroless nickel plating (EN) can be applied to a wide range of basis metals including steel, copper, brass and aluminum alloys. Electroless Nickel plating is currently utilized to promote corrosion protection performance across a diverse range of industries including heavy equipment, oil & gas, power transmission & distribution, automotive, marine and railway to name a few.

On earth aluminum blocks tend to have steel sleeves for the cylinders and they would be protected by lubricants.

Another coating process https://www.cybershieldinc.com/aluminum-finishing/

Calliban · 2020-12-22 19:38:24

The very thought of being anywhere near a liquid CO tank freaks me out. I would personally be more comfortable being close to a nuclear reactor than a tank of CO. Even a small leak into a confined space would be fatal. It also sounds as if there are serious materials compatibility issues. I thought the plan was to use liquid methane? In previous posts, there was discussion of solid oxide fuel cells that have much greater efficiency than any conceivable IC engine. Why not use those instead of IC engines?

S-CO2 power generation loops may not be as impressive as they sound for vehicle based systems. Whilst the turbines are incredibly compact, the heat exchangers are far bulkier. And to get those really high efficiencies, you need working pressure above 20MPa and hotleg temperature greater than 550C. For a ship, I can see this being a promising option. Maybe even a train.

tahanson43206 · 2020-12-22 19:49:09

For Calliban re #52

Thanks for pitching in to move the topic along. This topic ** is ** dedicated to Internal Combustion engines on Mars. There are numerous other topics where other technologies can be and are being advocated.

That said, your caution about the CO tank certainly needs to be a part of the thought process. My impression is that Mars is deadly all by itself. A little CO wouldn't make much difference in how quickly a human would expire without an Oxygen breather and a suit which is impermeable to incoming atmosphere molecules.

Taking your caution to heart however, I can imagine the designer of a vehicle which would be propelled by a CO/O2/CO2 IC engine would have a cabin which is itself secure against leaks, and able to sustain humans and other living creatures inside safely.

The technology that "wins" the hearts and minds of the consumers on Mars will be capable of:

1) sourcing locally
2) manufacturing locally
3) assembling locally
4) operating in the environment reliably
5) less costly (in terms of whatever metrics make sense) (money (of course) makes no sense in the context of Mars)
6) maintainable locally

There are probably other factors that are important that I've missed, so I hope members will fill in whatever gaps there are.

Edit#1: Both kbd512 and Calliban have reminded the reader of this topic of the risks associated with Carbon Monoxide.

The idea (originally inspired by SpaceNut and his work on a 2005 Subaru motor) that a Mars settler would haul the IC rover engine into the habitat for a gasket replacement appears to be off the table, due to the contamination of the metal with CO molecules.

Any such maintenance would have to be performed using teleoperation, and ultimately pure automation.

(th)

SpaceNut · 2020-12-22 19:53:36

A co tank would never be inside of a confined space as its only allowable outside where its does not matter.

Co molecules are no more a problem inside of a large habitat than they are inside of a closed up garage for braking down an engine.
All engines would enter via an air lock with space suited crew inside to do the initial break down so as to reduce the levels of trace gasses present and cooling liquids.

An engine will automatically be a methane engine to burn the boiloff and as far as bottled fuel goes we do it all the time in warehouses all the time on forklifts. One only needs to monitor the run time and levels with in the confined space we call home...

I have not looked at the S-co2 power loops and refer that to kbd512 and others....but the train would seem to fit for use.

tahanson43206 · 2020-12-23 08:17:06

For SpaceNut re #54

The Internal Combustion Engines for Mars topic could become the focus of a competition at the high school / college level. It has the distinct advantage of being a technology familiar to millions of parents, whose support would be helpful as students consider participation.

The Mars Society has already created competitions of various kinds, and from what I can see, many of them have been quite successful. A few have fizzled, but in the Capitalist System, failure of initiatives is part of the process.

In this case, the competition would be to design all components of an infrastructure that would use CO/O2/CO2 as the gas combination to power Internal Combustion Engines in all sorts of applications, from the smallest brine pump to the largest bulldozer.

All aspects of the infrastructure would be in play, from sourcing the gases using Solar Power (and Nuclear power as an alternative) through the details of fabrication of components using 3D printing.

Because 3D Printing would be specified as a requirement for all physical components, it would be possible to print all components in plastic on Earth, to confirm they would interact with other components correctly. Compressed air could be used as the simulation of combustion. I have seen this method used successfully on Earth, at a steam engine model demonstration.

(th)

SpaceNut · 2020-12-23 10:52:27

One more engine type is the hydrogen and oxygen boil off engine of which this can be an internal operated engine as we would not want the water exhaust to escape back into the wild and while a fuel cell might also work to do the same as well.

I agree that a competition for developement of these 4 plus engine types would need to be pushed further down the road for a mars settlement usage. It would also be held in conjunction of fuel productions required to feed them as well as for safety requiements for safe use of the.

We should also look at the energy for the poles to mid lattitude location transferring so as to keep a station manned as this is something we would want to do on mars If going with a solar array system and batteries to mars.

tahanson43206 · 2020-12-23 11:15:19

For SpaceNut re #56

Thanks for adding momentum to this suggestion ....

A concern I have is scattering of focus ....

A hydrogen oxygen Internal Combustion engine is both practical and well studied ... My recollection is that this method of fueling an Internal Combustion engine was put into practice in Germany many decades ago.

To the best of my knowledge, the CO/O2/CO2 gas combination has not been tested anywhere on Earth, for all of recorded history.

The NewMars forum, as a part of the Mars Society, has the opportunity to encourage original research.

It is even possible for a person with reasonable mechanical skills to carry out a feasibility study right now, on Earth, using discarded engines from the scrap yard. The test would involve preparing CO/O2 and CO2 in the proportions suggested by GW Johnson and kbd512 in their multiple posts on the subject.

Taking Calliban's warning into account, a test on Earth needs to be done with extreme caution due to the toxic/hazardous nature of CO.

That said, hazardous chemicals are routinely handled safely on Earth in 2020, and I expect they will continue to be safely handled in 2021.

(th)

kbd512 · 2020-12-23 11:53:19

tahanson43206,

Let's define how this Mars-ready Liquid Oxygen / Liquid Carbon Monoxide powered Super-Critical Carbon Dioxide thermal power transfer gas turbine power pack would operate, what it would be made from, and what practical applications it can be used for. The primary use case for this type of combustion engine is as a power plant for vehicles and backup generator on the surface of Mars or in the atmosphere of Venus. For virtually all of human history after the invention of combustion engines, the availability of Hydrogen-bearing gases / liquids / solids was taken as a given. However, on other planets that have atmospheres rich in CO2 but poor in readily usable H2O, production of gaseous or liquid hydrocarbon fuels presents an extreme petrochemical engineering challenge. Basically, there are no easy-to-acces water sources on Mars or Venus. Even if there were, synthesizing hydrocarbon fuels from scratch is an extremely energy-intensive and very complex process, if for no other reason that precisely zero existing infrastructure for synthesizing such fuels exists on Mars or Venus.

As such, it would be a mission enabler if we could still synthesize an oxidizer / fuel combination from a single common atmospheric gas, namely Carbon Dioxide, since that requires minimal input energy to obtain that gas in useful quantities, which we would then use to produce both an oxidizer (O2) and fuel (CO) using a single-step solar powered synthesizer, which requires minimal and lightweight equipment with very few moving parts, and then use our gas compression / heat exchange cooling technologies, colloquially known as cryocoolers, to densify that oxidizer and fuel into batches of more easily transportable cryogenic liquids. Moreover, we would like the combustion byproduct to be exactly the same product that we took from the atmosphere to begin with to avoid resupply issues.

Whereas alternatives such as photovoltaic panels require sensors and electronics to avoid drastically reduced power output through the accumulation of atmospheric dust or clouds, simple and relatively small fresnel lenses that can be periodically spray-cleaned with compressed CO2 can concentrate natural sunlight in order to produce the extreme temperatures required to cleave Oxygen from Carbon Dioxide, in the presence of specialized catalysts. A solar-pumped solid-state UV laser is another possibility for photo-dissociation of Carbon Dioxide. The relative efficiency of these processes is far less important than the fact that the input power is supplied by a source we don't have to transport, the low total parts count and very low moving parts count, which would be subject to degradation or destruction through mechanical wear. The inherent reliability of such a system, over decades of operation, as well as the low mass of the components required, is highly desirable since such systems will have to be transferred to another planet.

The great thing about completely mechanical systems with very few moving parts is that stationary parts tend to require very lengthy timeframes prior to failure and electronics or sensors that aren't present to begin with, likewise can't fail. The efficiency of such systems may not be as good as they possibly could be using electronic control, but absolute efficiency only matters in conjunction with utter reliability. A highly efficient but unreliable system is of little interest to space exploration and colonization for the purpose of supplying life-sustaining chemicals to a technologically advanced human civilization engaged in a relentless battle against nature while operating in a highly lethal environment to human life.

There are other available forms of highly concentrated input power that we could use, such as nuclear power, in order to synthesize the chemicals we need to construct a second branch of human civilization, and we will no doubt use them where appropriate, but such power systems may not be as easy to employ and typically require significant forethought to avoid accidents. By their very nature, nuclear power systems are most appropriate when incredibly high constant power output is required and a well-developed resupply infrastructure already exists. For example, a city on Mars with a million people living in it is not going to supply all of their power needs using photovoltaic panels, especially if that city's residents will grow their own food on Mars- and the incredibly high energy and thus monetary cost of transport dictates that they will. Prior to delivering new colonists by the thousands, we will need to create all the infrastructure necessary, often from scratch, to support them. This primarily entails locating / storing / transporting local natural resources, as well as creating pressurized and temperature-controlled living spaces for humans. All of those activities are done here on Earth using hydrocarbon-based fuels. On Mars, supplying the Hydrogen for hydrocarbons is a bit of a problem. Any water you can easily obtain also has lots of other uses for it that are directly related to life-support. To obtain water, you either have to travel to the poles and operate in a permanently cryogenically cold environment, or you have to stay in the milder mid-latitudes and drill for water, much as we drill for oil here on Earth. Combustion engines would make those tasks far easier to accomplish since heavy off-road vehicles are required to travel around on Mars and heavy construction equipment is required to fabricate living space from scratch. Here on Earth, precisely zero heavy off-road vehicles are battery powered. We simply lack the technology, at present, to produce batteries with energy densities comparable to any type of chemical reaction.

As continuous power or operating time requirements go up, the power density issues affecting battery-powered vehicle weight and range are not amenable to the types of vehicles and equipment we truly need to build another branch of human civilization on another planet. Much as the tyranny of the rocket equation dictates that nearly all of our rocket mass is propellant, the tyranny of the energy density equation dictates that nearly all of our vehicle mass is battery. The solution most commonly used here on Earth in such circumstances is to forego batteries in favor of more energy dense liquid chemical fuels. We're fortunate to not need to carry the oxidizer with us here on Earth, but no such luck on Mars or Venus. While the extreme environments of Mars and Venus may require fundamentally different solutions, all of the physical laws governing how the universe works are still in full effect on Mars. As such, we absolutely must have operating environment appropriate internal combustion engines to power vehicles, construction equipment, and backup generators.

Now let's consider a practical purpose-built internal combustion engine design that maximizes the use of readily obtainable local resources.

Principles of Super-Critical Carbon Dioxide Gas Turbine Operation

SCCO2 (Super-Critical Carbon Dioxide) gas turbines use the flow of supercritical CO2 working fluid through the turbine to produce electrical power by spinning an attached electric generator. In general, this power generation system uses a gas burner akin to a rocket engine's injector pintle and combustion chamber to produce very high temperatures that super-heat the supercritical CO2 working fluid, which is kept in its supercritical fluid phase using immense pressure. After flowing through the turbine housing the CO2 enters a special type of very high surface area heat exchanger known as a printed circuit heat exchanger, which is essentially a series of very small (hundreds of 1mm half circle channel etched into the heat exchanger plate) perpendicular gas channels with alternating hot and cold plates stacked on top of each other and diffusion bonded to each other to prevent cracking / rupturing, in order to transfer some of that heat to a radiator plate that radiates excess or waste heat into the surrounding environment. The general idea is to produce a useful temperature drop between the hot and cold loops without excessive pressure loss, since that would necessitate re-compression of gaseous CO2 into supercritical CO2, in order to continue to reap the power density benefits of using a working fluid with a density quite similar to liquid water. The thermal power transfer fluids operate in a completely closed loop, but the combustor operates in an open loop, meaning once the heat of combustion acts upon the working fluid, the exhaust gas byproduct from combustion is discharged into the atmosphere. In this case, the oxidizer is Oxygen stored in a LOX vacuum thermos and the fuel is Carbon Monoxide stored in a LCO vacuum thermos. A small amount of thermal power is siphoned off from the thermal power transfer loop to pressurize both the oxidizer and fuel thermos and to vaporize both cryogenic liquids prior to injection into the combustor, in preparation for injection via the pintle that feeds the combustor chamber. Flow restricting valves permit heat transfer rate variance to control the O/F mixture in accordance with the power being demanded from the turbine. Both gases are then injected separately through very small channels in the injector pintle, inducing them to swirl / mix in the combustor chamber / tube where they super-heat the CO2 working fluid in the power transfer loop, prior to being fed into the turbine, using a separate SCCO2 tube / feed line passing through the combustor chamber. In short, the flame produced inside the combustor torches the SCCO2 tube. The O/F mix is ignited by both the very hot operating temperatures and a specialty high energy ceramic spark plug akin to that used to assure ignition in the Space Shuttle Main Engine.

The temperature drop in the heat exchanger core produces expansion of the CO2, along with a pressure drop, and that is absolutely necessary to continue moving the SCCO2 working fluid through the gas turbine to produce mechanical output power (shaft horsepower that spins an attached electric generator) and to prevent build up of excessive heat, but excessive expansion would necessitate re-compression to keep the CO2 in its supercritical fluid state. The fantastic power density of the gas turbine is the result of pushing a very dense working fluid under extreme pressure through the thermal power transfer loop. The challenge is producing a heat exchanger that can simultaneously withstand high temperature / high pressure / highly oxidizing working fluid, sufficient surface area and compact dimensions. The use of LCO presents another set of material selection challenges, since the use of virtually all suitably refractory metal alloys in the combustor can would form lethal metal carbonyl chemical compounds that extreme precautions must be taken to avoid.

Material Selections and Explanations

Oxidizer and Fuel Supply System - To substantially improve volumetric energy density and decrease weight, both the oxidizer and fuel will be stored as cryogenic liquids in PTFE-coated 5083 Aluminum vacuum thermos tanks. For purposes of differentiation, green will signify LOX storage, white will signify LCO storage, red will signify LCO2 storage, and blue will signify H2O storage. The PTFE coating is intended to minimize unwanted chemical reactions between the liquid Oxygen or liquid Carbon Monoxide with the Aluminum storage tank. All fittings will be oxide-based ceramics and flexible feed-lines will be PTFE coated CNT fibers. Those specific materials are certified for chemical compatibility and to withstand cryogenic operating temperatures, which is why they were selected. Although overall volumetric efficiency of the storage tanks will suffer, each cryo tank will contain roughly 1.55 cubic feet of cryogenic liquid (~50kg for LOX, ~35kg for LCO). The intent behind using such small tanks is to maintain hand-transportability of cryogen tanks by a pair of humans in space suits, without the need for cranes or other specialized lifting equipment that may not be available. By utilizing these smaller tanks, supplies of oxidizer and fuel can be refilled at the atmospheric conversion stations and lugged a short distance to an awaiting vehicle or generator.

Combustor Can - The gas burner is a refractory fiber toughened ceramic can, near-net-shaped, baked in a vacuum oven at very high temperature, and then machined, as required; this is one of four hot section components in direct contact with hot CO, which is why it must be ceramic rather than metallic; same material used in military jet engine hot section fan blades / combustor cans / convergent-divergent exhaust nozzle petals

Injector Pintle - This assembly will also be a fiber toughened ceramic since it's in direct contact with CO

Spark Plug - Ceramic body with a Platinum electrode since it's in direct contact with CO; not strictly necessary in steady state operations, but there to assure ignition during rapid power changes

Gas Turbine Wheel - A precision-machined single-piece of Inconel billet; apart from the thermal power transfer tube, none of the gas turbine or thermal power transfer assemblies are exposed to CO in normal operations

Gas Turbine Housing - An Inconel thick-walled tube or billet using Inconel ARP bolt fasteners

Thermal Power Transfer Tube - An IR-transparent material such as Quartz or Sapphire; the only part of the thermal power transfer loop that passes through the combustor can

Printed Circuit Heat Exchanger - This assembly, by far the most complex to machine and fabricate, will be made from Inconel plate, the micro-channels will be acid-etched onto the surface of each plate, and then the plates will be stacked and diffusion bonded

Radiator - The radiator will be a Copper plate that's been silver-solder brazed to the heat exchanger; no part of this component is in direct contact with CO or CO2 in normal operation; back of the radiator plate will have a ceramic thermal barrier coating applied

Piping / Fittings / Seals - All thermal power transfer feed piping to the radiator will be made from Inconel, to include the seals, since no other materials will meet the pressure / temperature / oxidation resistance / thermal-hydraulic effects requirements

Insulation - All exposed piping, fittings, housings, and the back of the radiator will use Oxide-based thermal barrier coating to inhibit unwanted heat transfer into the engine compartment

Electric Generator - On account of how fast a small SCCO2 gas turbine spins, the most practical type of generator to produce power would be a Variable Frequency Generator (VFG) of the type used in aircraft such as airliners. A VFG requires frequency regulation using high speed solid state switching electronics to frequency-stabilize its output, but direct attachment of the VFG to the gas turbine's shaft, without reduction gearing, is the principle benefit provided. I've mulled over whether or not an Axial Flux Permanent Magnet Motor-Generator (AFPMMG) would be a more efficient alternative for supplying motive power, with appropriate reduction gearing. However, the low total weight of the VFG and frequency-fixing power electronics, along with the high reliability of those electronic switches in aircraft use, makes me think that the VFG could pull double duty so we don't have reduction gearing and power electronics for voltage regulation required to use AFPMMGs to supply direct motive power or function as a power supply to hub motors. The use of two different solutions for traction motors vs backup generators also creates another supply headache that we don't need. The AFPMMG was a much better proposition for use in conjunction with the compression ignition piston engine that we're not going to be able to implement in any practical sense if we limit ourselves to Carbon Monoxide fuel, since someone will eventually have to service either type of power plant. VFGs are most suitable for complex load environments, and the requirement to provide motive power, life support, and lighting certainly qualifies. There's probably some way to use the stationary generator to capture thermal power from the radiator to heat a water tank, both to keep it liquid and use it for showering or cleaning on the base.

Applications

On account of its weight and bulk and high continuous power output, this type of power plant is best suited to heavy off road vehicles, construction equipment like bulldozers, and stationary backup generators, rather than small vehicles like road-bound motorcycles or passenger cars. That's not much of a problem on Mars, since there are no roads and the overall durability and protection that an all-steel tracked armored (against radiation, rather than incoming projectiles) vehicle provides is much greater than that of lighter vehicles. In physical form / layout, the engine proposed here would somewhat resemble the removable self-contained diesel or gas turbine power packs used by main battle tank. That's a good thing, since it will be used in a very similar vehicle with various construction-related attachments, rather than a turret. If you've ever seen armored engineering / tank recovery vehicles, that's pretty much what I had in mind. They're heavy and powerful enough to move small boulders and pull other vehicles out of the mud. Instead of turrets, they typically have a bulldozer blade, crane, winch, and various hand tools.

tahanson43206 · 2020-12-23 11:59:37

For kbd512 re #58

Thank you for a significant contribution to SpaceNut's topic here!

SearchTerm:CO Comprehensive review of infrastructure for use on Mars
SearchTerm:CarbonMonoxide

http://newmars.com/forums/viewtopic.php … 25#p175225

For SpaceNut .... can you think of anyone in your community who would be interested in pursuing a study along these lines?

I have to read Post #58 in detail, but at first scan it appears to contain much of the distilled knowledge a local high school teacher or perhaps a junior college professor could use to set up a class project that should (** should **) yield a useful paper or two.

The inquiry of SpaceNut goes double or triple for forum members who live in regions rich with educational resources.

I would be willing to post a Letter-to-the-Editor about this kind of initiative, if we (forum collectively) were to come up with wording that would pass muster with Dr. Zubrin. The reputation of the Mars Society would be on the line, so his approval for such a communication is mandatory.

(th)

kbd512 · 2020-12-23 13:38:46

Calliban,

Why does the thought of a LCO tank that's left outside in a near vacuum freak you out? These are liquid cryogen tanks. You're not going to be sleeping with them. As SpaceNut stated, cryogen tanks will never be present in any pressurized living areas, for the same reasons that LPG tanks are stored outside here on Earth. We already know that they're intrinsically dangerous.

The use of LCH4 is dependent upon a steady supply of Martian ground water not required for other life support or return propellant applications and a highly reliable and efficient Sabatier reactor. All of the liquefaction equipment is required for either solution. I would prefer LCH4 over LCO for its energy density, but LCO is much easier to obtain from atmospheric CO2 processing and just as easy to store.

The SOXE fuel cells are, to my thinking, better than combustion engines, but the entire fuel cell is a porous brittle ceramic that operates at a temperature quite similar to a jet engine combustor can. There have been problems with cracking from rough handling, but off-road vehicles will jostle them around quite a bit by the nature of how they're operated, and we still don't have a really good mounting solution. For an on-road vehicle or ship or train or aircraft that doesn't see repetitive double-digit gravitational acceleration, they should work just fine. The high power density (3kW/kg) types that NASA developed are constructed as single pieces, much like the printed circuit heat exchangers that Heatric (UK-based corporation) developed for SCCO2 gas turbines developed by NREL and others. You don't have to crack the entire cell to destroy it, but no acceptably oxidation-resistant metal super alloys are available for the temperatures involved, as all of them will readily oxidize at the normal operating temperatures of SOXE cells, and that's the primary reason they're made from doped ceramics to begin with.

To tahanson43206's point, small gas turbines are frequently employed in oilfield operations involving pumping of fluids, which generally requires constant high power output from a portable package that can be easily moved about the drilling platform and to/from the well. The diesels are used to drive variable loads associated with drilling itself (power output can vary remarkably, dependent upon what you're drilling through, which would make a gas turbine far less fuel efficient, and fuel has to be transported to the well site), typically electric motors used in top drives. Both activities certainly could be accomplished with a fuel cell and electric motor, but here on Earth hydraulic or electric motors with power supplied to them by diesel generators are most frequently employed for variable power activities. The diesel is mounted to the deck of the drilling platform, it spins a generator, and a much lighter (than a V12 marine diesel engine) electric cable runs electrical power from the deck to the top drive electric motor. Hydraulics tend to get used in rock crushing more than drilling, but both electric and hydraulic motors are used. I have to believe that the engineers who design such systems for these activities base at least part of what they do in ultimate efficiency and practicality in actual operation. Diesel engines can operate on heavily contaminated fuel that would kill a gas turbine or fuel cell, but this type of gas turbine is more like a gas burner in a CO2 boiler than a jet engine. The turbine portion of this jet engine operates in a completely closed loop for that very reason. The burner is small and easy to clean without major disassembly, whereas the power turbine is not.

Theoretically, you could erect a solar panel field near each well site, but that might take a month or two for a proper setup, and the photovoltaic panel output is highly dependent upon atmospheric conditions / latitude / seasonality, whereas stored chemical power is not. You still need solar power to produce the oxidizer and fuel, but then you get to decide how / when / where to use it because it's so easy to transport off-road, relative to batteries or ceramic fuel cells. In theory, we'd prefer the fuel cell for its increased "well-to-wheels" efficiency. In practice, we're probably talking about stationary generators that have been carefully emplaced and supplied with super grade reactants nearly free of any contaminants. Given the austere environment, unavailability of spares if those spares are very large or heavy, and quantities of pure reactants required, that may not be practical until upgraded chemical processing facilities become available. The military routinely operates an incredible range of gas turbines in the most austere and inhospitable environments found on Earth. Thee's little reason to think we can't do the same thing on Mars. I'm a proponent of SOXE fuel cells here on Earth because they'll be operated in relatively benign acceleration environments aboard aircraft and ships or round-bound vehicles. I would certainly like to see one ruggedized to the point that an off-road truck like a JLTV (a military "Trophy Truck" with armor and weapons) can use one in lieu of its diesel, but I've seen no such applications thus far. The military has used SOXE fuel cells in relatively small portable electric generators.

tahanson43206 · 2020-12-23 18:21:05

For kbd512 re #60 to Calliban

SearchTerm:CO2 Explanation of benefits of using indigenous least-cost fuel/oxidizer infrastructure on Mars
SearchTerm:CarbonMonoxice
SearchTerm:FieldOperations for mining on Mars

http://newmars.com/forums/viewtopic.php … 27#p175227

(th)

kbd512 · 2020-12-23 19:31:06

Part of the mythology that we should dispel is the notion that it's practical or even feasible to complete major construction activities, over years or even decades of continuous operations, using anything less the highest quality all-steel tracked vehicles that money can buy. As heavy as steel is, that's the material of choice for construction and hauling equipment. We still manage to break such all-steel construction equipment with regularity here on Earth, where supplies of replacement parts are plentiful and far easier to transport. If anyone thinks we're going to complete a decade's worth of construction on Mars using a carbon-fiber bulldozer chassis, you're quite mistaken. If it was even feasible to fabricate such a vehicle, irrespective of cost, then someone would've done it by now, if only for testing purposes. Nobody's doing it because it's waste of time and money, not because they're interested in making more money. If CFRP was practical, then someone would be selling premium construction equipment and somebody with more money than uncommon sense would be buying it.

Certain concessions to reduce weight we can get away with, whereas attempting to do that in other areas is only inviting an early catastrophic failure. For example, the hoods on late model Class 8 heavy duty trucks are now fabricated from lightweight (lighter than Aluminum or sheet steel and less prone to corrosion) fiberglass, because we know how to fabricate parts that can withstand that particular use case. However, every single production Class 8 truck on the road today uses a steel frame rails to connect the engine / wheels / suspension components to. We have experimented with Aluminum, Titanium, GFRP, and CFRP, but the crushing weight of the engine / fuel / loaded cargo trailer and unfavorable fatigue or heat resistance properties of those lighter substitutes were simply not amenable to typical operating environment, so that's as far as it went. In so many different applications, old-fashioned steel is really tough to beat.

NASA may pretend that they're going to invent construction or hauling equipment using spindly little composite and Aluminum wheeled vehicles more suitable for carrying passengers than cargo, but actual long duration torture testing will demonstrate the folly of that approach. No re-invention of the wheel is required here. We already know what works. Yes, it's a pity that durable off-road vehicles are so heavy, but that can't be helped. I noticed that their regolith collection robots for their ISRU equipment "evolved" from Aluminum and CFRP to steel really fast. All the countless billions of dollars spent on development and testing projects keep telling us what we already know, over and over again.

Anyway, a Mars-ready construction vehicle looks a lot more like a Russian T-55 bulldozer than that MMSEV abortion that someone at NASA dreamed up to satisfy their cravings to prove how clever they were, rather than how practical they could be. A T-55 dozer blade-equipped vehicle weighs 28t (28,000kg), but only 10.64t (10,640kg) on Mars. It's dimensions are 6.88m L x 3.39m W x 1.58m H. It can climb over a 0.8m vertical obstacle and cross a 2.7m trench. On Earth, it's equipped with a 426.59kW diesel, for a power-to-weight ratio of 15.24kW/t. On Mars, it'll be equipped with a pair of 125kW SCCO2 gas turbines and sealed electric traction motors with magnetic reduction gearing, for a power-to-weight ratio of 23.5kWt. The tracks are 580mm wide. There's probably at least a ton of garbage included in that vehicle's weight that's part of its original design as a tank and a pre-electronics combat vehicle, but roughly speaking, this is the sort of vehicle chassis with the durability required to withstand continuous off-road use for at least a couple of decades.

Here's a website with a picture of what this former tank-turned-bulldozer looks like:

BULLDOZER BZ-55 (CHASSIS T-55)

This is just to give people an idea of what I'm talking about. I'm not suggesting that we rip out the diesel engines and send T-55s to Mars after we re-equip them. Even if we did do something that ridiculous, it'd still be a more practical vehicle than the various "experiments" I've seen over the years. However, this is intended to clue people in on what a durable off-road vehicle actually looks like. It's not light, it's not pretty, it's not an off-road truck that boys love to play with so much, but it is a simple, practical, durable, and effective piece of construction equipment that will withstand the severe use we would subject it to.

tahanson43206 · 2020-12-25 06:44:48

This quote is from a recent post by kbd512 in the Electrically powered construction equipment topic:

We still need to figure out what the minimum thermodynamic requirement is to split CO2 into CO and O2, then add an inefficiency factor using known processes.

http://newmars.com/forums/viewtopic.php … 56#p175256

This unmet need should be addressable by one or more members of the forum, if there is time.

It is also entirely possible the answer has already be published in the existing forum archive.

In any case, it should be possible to design and build an end-to-end duplicate of the CO/O2/CO2 IC engine infrastructure on Earth.

The only details (that I can think of) not already achieved include (a) using CO2 instead of Nitrogen as the buffer gas, and (b) exhausting into vacuum.

Exhausting into near Mars atmospheric pressure can be achieved by running the engine at altitude comparable to Mars, and that can be achieved with a balloon flight, if computer modeling does not adequately confirm the system will work fine.

(th)

tahanson43206 · 2020-12-25 11:52:22

For kbd512 re possibility of a textbook evolving from discussions in NewMars forum

After thinking about the idea overnight ... I think it is practical to consider an eBook format ...

I'd like to see some support from the Mars Society .... Fortunately SpaceNut is taking care of contact with the Powers that Be ....

It is possible the Mars Wiki format might be suitable for developing an eBook textbook that would stand the test of time.

Whatever format this becomes, it needs to be good enough for a settler to study (a) and use as a reference (b).

A practical handbook is a format used by engineers on Earth since at least the days of the Pharaohs, but I admit I'm speculating a bit, because I don't recall seeing anything quite like what we have today in the records or observations I've seen about the period.

Perhaps a way to approach this is to consider titles for a library an engineer (or student) would take along to Mars ...

Something like the (by now ancient) Handbook of Chemistry and Physics would seem (to me at least) a basic title for any engineer's library.

What I have in mind for this topic is a handbook containing everything knowable ahead of time about the entire infrastructure to be built on Mars.

There are others (in the forum and elsewhere) who are hard at work on all-electric solutions to the Mars problem.

This topic seems to me to have a sensible constrained focus on eminently practical, maintainable technology that is ** also ** likely to turn out to be most energy efficient AND robust over the long run.

Hydrogen and Oxygen systems will give CO/O2/CO2 systems a run for the money at some point, but (I suspect) not for a while, and certainly not until after the CO/O2/CO2 systems have excavated the water needed.

If there is a member of the forum with ideas about how such an eBook textbook might be structured, this is a good time to pitch in.

(th)

SpaceNut · 2020-12-25 17:45:56

Well the only way that we do not get co is if we do not use a moxie system to break it down to provide oxygen under other considerations for how to get it since free standing water is a problem for deriving the oxygen in quantity and its really about the hydrogen from a soil source at that point to make the fuel....

We also know that we can break the bond in liquid co2 by using a zo. which is real electrolysis to which moxie is not.

https://en.wikipedia.org/wiki/Electroch … on_dioxide

Then again we can now dissolve of a electrolytic solution....
Scientists turn CO2 ‘back into coal’ in breakthrough carbon capture experiment

We can also now do it with both present in the solution as well in what I would call a hybrid in that it does some conversion like a fuel cell and others like an electrolysis....
Carbon Dioxide and Water Electrolysis Using New Alkaline Stable Anion Membranes

The cell operates at a current density of 140 mA/cm2 at a cell voltage of 3.5 V. The power consumption for production of formic acid (FA) is about 4.3–4.7 kWh/kg of FA. The second process is the electrochemical conversion of CO2 to CO, a key focus product in the generation of renewable fuels and chemicals. The CO2 cell consists of a two-compartment design utilizing the alkaline stable anion exchange membrane to separate the anode and cathode compartments. A nanoparticle IrO2 catalyst on a GDE structure is used as the anode and a GDE utilizing a nanoparticle Ag/imidazolium-based ionomer catalyst combination is used as a cathode. The CO2 cell has been operated at current densities of 200 to 600 mA/cm2 at voltages of 3.0 to 3.2 respectively with CO2 to CO conversion selectivities of 95–99%. The third process is an alkaline water electrolysis cell process, where the alkaline stable anion exchange membrane allows stable cell operation in 1 M KOH electrolyte solutions at current densities of 1 A/cm2 at about 1.90 V. The cell has demonstrated operation for thousands of hours, showing a voltage increase in time of only 5 μV/h. The alkaline electrolysis technology does not require any precious metal catalysts as compared to polymer electrolyte membrane (PEM) design water electrolyzers.

So the problem is not that we can not get carbon is any oxygenated for its that lack of power we need to make it happen which is the issue.

What we are trying to do is run via insitu resource a combustion engine on mars with fuels that we can create and or use with respect to boiloff which can only be slowed and not prevented....

We may also have another ignitor of the fuel in a plasma as some one once suggested....

kbd512 · 2020-12-25 19:04:36

First, on behalf of our New Mars Forums staff, Merry Christmas and Happy Hanukkah to all of our readers out there in Mars Land. Happy Festivus to my fellow jokers, admittedly, a couple of days late. While we worship high strength metals around here, there will be no airing of grievances this year and feats of strength will be substituted with feats of electrochemical engineering.

We need to consider the technology and power requirements for our portable oxidizer and fuel source for our Super-Critical CO2 (SCCO2 or sCO2) gas turbines, which must be produced by Solid Oxide Electrolysis Fuel Cells, commonly abbreviated as SOXE or SOFC. These units will be supplied with thermal power from Concentrated Solar Power (CSP) and electrical power by Recompression Closed-loop Brayton Cycle (RCBC) SCCO2 gas turbines driving electric generators to avoid having to keep acres of photovoltaic panels relatively clean on a planet where the entirety of its surface very closely resembles "The Great Dust Bowl" of American Depression-era fame.

As previously stated, our reasoning behind using CSP is the relative ease of cleaning mirrors versus electro-statically charged photovoltaic panels, the relative durability and longevity of closed-loop gas turbines driving electric generators, the relative abundance of atmospheric CO2 and the ease with which it may be obtained, and the relative simplicity of the very well established technologies required, relative to drilling a water well a couple of kilometers deep or landing at the cryogenically cold Martian poles and running a MW-class Sabatier reactor to synthesize Methane in an automated fashion, since that still requires the development of all the technologies proposed for use here, which is an even more energy-intensive process. We know absolutely nothing about the available ground water supplies, so we've no clue if we're getting a high salinity brine laden with corrosive chemicals or a frozen mud loaded with abrasive volcanic ash, or some combination of both. Either way, turning that raw resource into potable water or a liquid hydrocarbon rocket fuel will come at fantastic energy cost and require very specialized equipment. To merely arrive at the point where we can concern ourselves with water wells and rocket fuel, we really must have a type of "starter fuel" that's more energy dense than current commercial batteries and less complicated and energy intensive to make than Methane. We would naturally prefer to land next to a fully-functional petrochemical refinery and multi-megawatt class power plant, but this is Mars we're talking about and we've no such luck, on that front.

While we would prefer SOXE to power our vehicles, but as we're about to learn, there are some long term challenges with doing that. To begin with, the US Army has had better luck with SOXE in portable generators than vehicles. Perhaps Private Snuffy is too rough with his off-road truck, but he seems to be better than average at breaking those fuel cells in off-road vehicles. The US Navy also had a bit of bad luck while trying to implement SOXE fuel cells aboard ships, although we're unlikely to encounter the same marine diesel fuel contamination or corrosion issues that plagued their pilot program. Some of those problems have since been solved, but the requirement to not bash the fuel cell about has not. It turns out that when you repeatedly thermally cycle a porous thin-walled ceramic membrane from ambient to 1000C while subjecting it to 20G+ "jolts" from driving over rocks and ditches, bad things can happen to the structural integrity of said ceramic, especially if it must be rigidly mounted to the chassis of the vehicle its powering. Most of these vehicles need a fuel cell that weighs as much as an engine block, so mounting it with bungee cords isn't very practical. We also need bungee cords that withstand blow-torch temperatures. This should not be too surprising to anyone who's ever driven home with a pane of window glass in the bed of their pickup truck- without decent padding, it just doesn't work very well. Heavier tracked vehicles are also notorious for comparatively rough rides, but traction / low vehicle CG / serious hauling capability are all necessary and good features of well-designed construction equipment, so we're exploring the use of tiny closed-loop gas turbines heated with rocket engine / boiler technology as a potentially more practical alternative that can withstand the years of abuse that we need our Mars-based ground vehicles to tolerate to remain in service.

The first order of business after arrival, presuming we wish to live on Mars indefinitely, is to construct a long term viable power plant that will still be operating 50 to 100 years down the road without enormous and continuous material inputs delivered from Earth, tens of millions of miles away. To that end, we're going to employ small nuclear reactors to collect / purify / liquefy our first batches of CO2. The other gases collected are important for providing buffer gas for humans to breathe (Nitrogen), lighting up our "Open For Business" sign or welding (Argon), and filling balloons that environmentalists will worry will land in an ocean somewhere that Mars doesn't have to begin with (Helium). In all seriousness, though, we need those other gases and ideally, we want to feed pure CO2 into our SOXE device, so we don't have lots of other electrochemical reactions to concern ourselves since this device is hot enough to melt Copper. At the very least, we definitely don't want any Iron Oxide particulates entering into that device, or the results will be very bad.

Apart from sufficient power for the production of the desired quantity of LOX and LCO, there are two key performance factors affecting the viability of our SOXE cells that make LOX/LCO.

The first is the Faradaic Efficiency (FE) of the SOXE cell that does the electrochemical splitting of CO2 into our O2 oxidizer and CO fuel. This is a measure of selectivity for the production of Carbon Monoxide. If FE is much less than 100%, then at the production rates required, a fairly rapid plate-out of the cell catalyst membranes with Carbon will occur, which tends to ruin the cell. To prevent that from happening, getting the input heat and voltage correct is very important.

The second is Electrical Power Conversion Efficiency (EPCE). The electrical power required to sustain this process must be supplied by equipment landed on Mars, therefore the total system weight is a big deal. The total electrical and thermal power required by different types of fuel cells is closely related to FE and EPCE. It just so happens that Yttria-Stabilized Zirconia SOXE cell run at around 100C produces a FE of 100% and a EPCE of 92%, which is the absolute highest of all tested types of electrochemical reactors / fuel cells. It's almost as if those engineers who designed and built MOXIE actually knew what they were doing. As a result, that type of fuel cell requires about 2.4kWh/Nm3 of CO produced, and 1Nm3 (normal cubic meter) of CO gas weighs 1.229kg. Roughly speaking, we need to supply 1.95kWh for every kilo of CO that we produce. That's only the power requirement for producing the Oxygen and Carbon Monoxide, not the power required to collect / purify / liquefy the input CO2 feedstock, nor the power required to liquefy and store the LOX/LCO produced.

Finally, ideally we would prefer that the waste heat from this process matches the input heat required, or be used to recompress gas in our attached electric generator that supplies electrical power to our fuel cell and cryocoolers.

Minimum LCO2 liquefaction power requirement: 1,867kWh (must be supplied by the CSP system's SCCO2 gas turbine)
Minimum SOXE fuel cell thermal power requirement: ? (must be supplied by the CSP system)
Minimum SOXE fuel cell electrical power requirement: 2,787kWh (must be supplied by the CSP system's SCCO2 gas turbine)
Minimum LOX/LCO liquefaction power requirement: ? (must be supplied by the CSP system's SCCO2 gas turbine)

This is already looking pretty unfavorable in terms of energy input, but perhaps there's a bit of an "escape clause".

1. A very healthy portion of the waste heat produced from CO2 / CO / O2 compression and liquefaction, which will be substantial, some of it high grade, could be recycled back into the system through the PCHEs inter-coolers between compressor stages.
2. If we recapture the hot CO2 exhaust from the combustor can, feeding its thermal power back into the gas turbine's PCHE for recompression into liquid CO2, which imposes a mass and space claim penalty on the vehicle, then we could feasibly re-capture most of the CO2.
3. If we fed that recaptured CO2 back into the LOX/LCO production process, then the total energy input drastically decreases and we're essentially making up for losses. Alternatively, we're gradually accumulating enough LOX/LCO to send a Starship back to Earth every 2 years, although I would argue for using it to power hundreds of pieces of construction equipment.

I don't see how we can build a city for a million people without hundreds of pieces of construction equipment in any reasonable amount of time. As such, first order of business is to land a handful of small nuclear reactors to provide that all-important startup power. Going back to our battery charging conundrum, if we have to provide 4MWh to assure any kind of acceptable battery life, then that's at least 14t worth of battery for the vehicle itself and then another 14t for the battery we have sitting on the charger. Presumably, we can't charge a vehicle battery while the vehicle is in operation.

For every 26t (I subtracted the weight of the diesel engine from the T-55, but not the transmission, since that weight will be replaced by electric drive motors) piece of construction equipment that needs 250kWh of continuous power, we're looking at a nearly equal weight in terms of batteries. Suppose that we need to send 100 pieces of construction equipment. That's 2,600t for the equipment and 2,800t for the batteries. In about 10 years, we'll need to send another 2,800t worth of batteries to keep the equipment running. I might be the only one, but that seems impractical to me. Naturally, we'd expect improved cells in another 10 years to lower the supply tonnage, but that's still an incredible tonnage of batteries that we can't recycle into something new. With 2,800t to play with, we could easily deliver a multi-hundred megawatt nuclear reactor, with shielding, or all the components of a 20MW CSP farm, which will still be operating 30 years later, unlike photovoltaic panels. We can't ship a reactor that size, even though it would make life so much easier, because we don't have a rocket that can lift the pressure vessel. However, what we can do is ship a CSP / Molten Salt / SCCO2 gas turbine setup with storage tanks for LCO2 / LCO / LOX / LN2 / LAr / LHe, such that we have the chemical precursors for living there. I don't think we can save any mass on the power plant with batteries and photovoltaics / CSP / nuclear, but at least we can "buy once, cry once" with suitably durable solutions.

kbd512 · 2020-12-25 20:30:01

tahanson43206,

You should really consult real engineers, instead of a complete amateur who's completely fascinated with going to Mars. Given enough time and self-learning, I can probably figure out everything I need to know, but we need real formally-trained engineers who are willing to donate their time to make this happen, or it's not going to happen. I'd be willing to bet second or third year engineering students know far more about these topics than I ever will. I learned about some of that stuff related to SOFCs, as of yesterday. The only type of systems I have practical experience with are computer control systems, databases, data modeling, and reporting. When I was a kid, I built radios and other electronics, repaired electronics, built my own rockets and RC aircraft, but I recognized early on that I understand computer programming and can write code for pretty much any problem I understand, so that's what I do. Most kids who grew up in the 1980s probably didn't receive a computer and a C compiler for their birthday. Apart from piston engines and flying piston engined aircraft, that's about the extent of my experience with anything related to engineering. I am trying to design and build my own aircraft, but it seems like a continuous learning process without end.

If there's significant interest in applying engineering principles to practical devices that will work in space or on another planet, then people so interested are either already working for a corporation or government agency on those designs and not talking about it very much, or they're engaging in more of these intellectual exercises that never produce practical flight-qualified hardware. Maybe it's just me, but it seems that NASA is increasingly more interested in satisfying intellectual curiosity than they are in producing flight qualified hardware that we could take to another planet and begin constructing the type of facility that would serve as a proving ground for Mars-qualified construction hardware. As we still can't reprise Apollo missions after more development time than the Apollo program existed, I'm guessing we simply never made it that far, with respect to "next steps" for finally living in space on a permanent basis.

Oldfart1939 is a real chemical engineer
GW Johnson is a real aerospace engineer
Josh is a real thermal systems design engineer
Antius is a real nuclear systems engineer of some kind, but he was booted for some reason and I wasn't curious enough to find out what for, nor would it change whatever policy he violated

I'm none of those things, just some 40 year old kid who wants to see people go to Mars and build a second branch of human civilization there. I don't have all the answers and I'm nearly certain that I flubbed several of the calculations I made on input energy requirements due to lack of understanding of the subject matter. However, I did actually try to take basic principles that I did understand and apply them to a real world problem in a realistic way.

It's tough to find knowledgeable people who are truly interested in space exploration. Most people are initially attracted to fanciful ideas and then they're no longer interested when the rubber meets the road and engineering reality dashes their hopes and dreams. As a child, I had the privilege of meeting some real engineers and scientists (people from NASA's astronaut corps and their engineers) through family and I have a couple of relatives who have worked for NASA on math and physics problems. I work on statistical analysis software, that's all, and these days I don't even get the opportunity to apply much of what I know about that, but a job's a job and it pays the bills. If I had an opportunity for a "re-do" of my life, I would've studied aerospace engineering instead of computer science, but that's a tough call because I really like working with computers and writing code as well.

What I would like to know is how real engineers like Oldfart1939 and GW, or Josh if he's still lurking about, would approach their solutions to the problem of how to supply enough energy to accomplish some real construction work in a severely mass-constrained environment. Maybe they'd all use photovoltaics and batteries and tell me I'm wasting my time. What I do know is that cities with a million people living in them weren't built using battery powered construction equipment and fields of dusty photovoltaic panels. It's a fantastic idea, but we don't seem to have the technology to do that yet. I also know that knowledge is like an onion the size of the universe. Every layer you peel back reveals another layer. If you're truly interested, the only question you need to ask yourself is how deep you want to go, because there's no limit.

To be frank, anyone who wants to go to Mars is going to have to know quite a bit about thermal and electrical systems, because they're going to be dealing with issues related to those types of system every day, even if we take nothing but photovoltaic panels and batteries with us. Batteries still produce waste heat, they still have to be kept warm, power inverters produce waste heat, electric motors produce waste heat, etc. You'll need to know the limits of what your equipment can tolerate and always be mindful of what can happen if you exceed those limits.

The more and more I teach myself out of personal interest, the more I realize that I don't know. One person is not going to be the deciding factor, with respect to gathering the requisite knowledge, implementing practical systems, maintaining those systems, etc. I have learned that you can teach yourself anything. With 6 to 9 months of waiting before landing on Mars, any prospective colonists should receive a crash course in basic engineering principles, possibly approaching military rigor, with particular regard as to how those principles will affect whether or not they live or die. BTW, this is why nearly every astronaut has a PhD. They've proven that they can teach themselves. Apart from embodied knowledge from years of learning, that's all that PhD really means. You've proven that you not only can, but will, teach yourself and that's what humanity, in general, needs to grow and thrive, here on Earth, on Mars, and far beyond.

GW Johnson · 2020-12-26 11:08:35

Internal combustion engines using fuels and oxidizers made locally on Mars make sense only if you have MW of available electricity with which to make the fuels and oxidizers. If all you have is KW available, you can never make enough fuels and oxidizers to power much of anything.

Considering the low energy conversion efficiencies of internal combustion engines, it makes more sense to use the electricity directly to make the shaft power that you need. Those efficiencies range from about 0% at idle to at most near 15% for continuous operation at wide-open throttle. Most electric motors exceed 85% efficiency.

If you cannot get sufficient torque directly from the electric motor, then use it to power a fluid pump for a hydraulic system, and get the torque you need from hydraulics. Hydraulic power and torque is well-known to be enormous, as long as great speed is not required. Most liquid pumps exceed 65% conversion efficiency.

About the only reason you would ever want to incur the low conversion efficiencies of internal combustion engines, especially if you have to store BOTH fuel AND oxidizer the way that you must on Mars, would be when very long range is required, longer than what you could store with a battery exceeding the weight and volume of your fuel AND oxidizer tankage (not just your fuel tank as here on Earth!!!). If you use a diluent gas, you have to include that as part of your oxidizer!

Those considerations are why my own opinion is that construction machinery on Mars should be battery-electric-driven hydraulic, charged at night while people are not at work. Which means you need electricity 24/7 around the clock, even at night. And that means nuclear. You can put some solar on the roof of the machinery to keep the battery from draining quite so fast, but the primary charging comes at night.

Transportation machinery is not construction machinery. That will be as true on Mars as it is here on Earth, although the implementations will be different on Mars than they are here on Earth. The shorter and medium range stuff will likely be battery-electric, with direct electric motor drive. The consideration limiting practical battery size will be space available on-board vs volume of battery required for an amount of usable, deliverable energy. For this, you compare not to the energy in a volume or weight of fuel, but to the total volume and weight of fuel plus oxidizer plus diluent gas (if any), since you must carry all three on Mars, quite unlike only having a fuel tank on Earth.

Only the long range stuff would justify the carriage of sufficient fuel, oxidizer, and diluent gas to cover the range away from any massive sources of electricity with which to make those consumables. And I think that would be a temporary situation. Because, eventually, you will string the wires or create the power plants in-situ to effectively electrify that travel route. Once that obtains, your short range battery electric transport becomes long range with night time recharges along the way.

Sorry, them's just the facts of life on a planet with a near 24-hour day and a chemically-inert inert atmosphere too thin to easily compress. Yes you can create fuels and oxidizers from it, once compressed, but only via massive amounts of electricity that must come from elsewhere. Mars ain't Earth. Not by a long shot. Earth has a dense, oxygen-rich atmosphere. (And it has underground hydrocarbons.)

That situation is totally unlike Mars.

And the moon is different still!

Daylight hours last 14 days on the moon, and darkness another 14 days. You battery charge discharge cycles (and your human awake/sleep cycles) do not mesh well with that situation. Neither does solar power-only. The battery to get through 14 days of darkness is just ridiculous. You will have to be primarily powered by nuclear on the moon.

GW

Last edited by GW Johnson (2020-12-26 11:16:47)

tahanson43206 · 2020-12-26 11:36:44

For GW Johnson re #72

This topic is dedicated to the proposition that Internal Combustion engines will find favor with settlers on Mars.

There are topics where electric powered devices are under discussion.

However, your post #72 deserves and will (I'm sure) receive careful study, because those who will (without a shadow of a doubt) actually design, build, install, operate and maintain IC engines on Mars need to be aware of the problems and pitfalls and disadvantages you've identified.

I would like to see those registered members of the NewMars forum who support the proposition of this topic to pitch in.

(th)

kbd512 · 2020-12-26 16:30:34

GW,

I would tend to agree that using a nuclear power source would make every other aspect of using electric vehicles a whole lot easier, but if you haven't noticed, we're living in a nation with a lot of anti-nuclear people. Even if we weren't, there would seem to be other practical aspects that limit our ability to use nuclear power and incredible quantities of batteries on Mars. For example, there's a lower size limit for nuclear reactors, beyond which, you tend to throw away a lot of the thermal power generated as waste heat. I noticed that David Poston's contribution to the Mars Society presentations this year included a "bespoke" Mars-specific KiloPower nuclear reactor design (of the type that Antius and I proposed using some years back) that uses a Brayton cycle gas turbine to spin the electric generator (rather than the "back-and-forth" free piston Stirling cycle design) and a flow-through radiator design that spins a high-speed fan to generate convective cooling through a much smaller radiator surface area. The end result was a drastically more compact and lighter design (large bush vs small tree) that turns almost 50% of the 40kWt reactor's thermal output into electricity. However, to build a city of a million people, we're going to need an incredible amount of power that trash can sized fission reactors can't provide in any practical sense. I think 10MW is a good starting point, but the 500MW-class reactors that the US Navy uses is where we want to be. Unfortunately, we can't deliver 500MW-class reactors to Mars, along with all the other pieces of the plant would have to be imported. I'm trying to come up with some kind of solution that doesn't mandate monopolizing available lift capacity with energy production. Even with Starship, everything has to be delivered to the surface in relatively small pieces. We can do that using CSP. If we could find a way to keep the acres of photovoltaic panels reasonably clean, we could probably do it that way as well, but the efficiency of existing PV will be worse than CSP, same as it is here on Earth. I don't think the electric motors are an actual problem and, if anything, they're an enabling technology. I'm pretty sure that I stated that we would use electric motors and generators in all of the solutions that I proposed.

1. If we're strictly limited to batteries, then any vehicle that requires high continuous power output is going to build up a lot of low-grade heat that has to be removed using giant Aluminum radiator panels that would exceed the surface area of the vehicle, and that means we now have radiator protrusions to consider whenever the driver is operating the vehicle. The first more practical alternative is a high-speed fan that consumes some electrical power to keep the size of the radiator within acceptable limits (the rear or top deck of the vehicle in question). The second alternative is a greatly increased battery capacity that avoids some heat build up through lower current demand. The third alternative is switching to an energy storage medium with an order of magnitude greater energy density. I chose to focus on the last alternative solution since the first two are so unattractive in terms of weight and volume.

2. I don't think anyone wants to go to Mars to ship batteries and solar panels to Mars. That's not a worthy goal unto itself. I know that thermodynamics says we can't win with any solution, and that much is readily apparent to me at this point, but I'm trying to figure out which solution is the "least consumptive" in terms of our available lift capacity, least likely to require a significant resupply tonnage, and apart from small-ish nuclear reactors (10MW or so) and electric power cables, there doesn't appear to be a clear winner.

3. Current Lithium-ion battery technology seems to drastically limit how much useful run time a vehicle has. Volvo has a small electric backhoe called the "ECR25". The manufacturer suggests that it has a maximum run time of 4 hours, but I noticed that it has a 40hp (29.8kW) electric motor and a 20kWh battery pack. Simple math says it can't even run for 1 hour, if maximum power output is demanded by the operator. It weighs 6,019lbs (2,731kg). I want to use construction vehicles 10 times as heavy as that little thing, so that will, in turn, demand 10 times more power. We could make its Mars weight equal to its Earth weight, which means about two thirds of the vehicle would need to be batteries by weight, and then we can actually run a tiny 40hp electric motor at maximum output for 8 hours without destroying the battery pack inside of a year. Seriously, though, we're talking about a 477kWh battery to run a miniature backhoe's electric motor at maximum output for digging and achieve a 50% DoD on the battery so we can count on having its battery last for 5 to 10 years. In this case, the battery would be larger than the vehicle itself, meaning it would physically occupy more volume than the entire vehicle does.

VOLVO ECR25 ELECTRIC

Take a look at that toy and then tell me if you think a city of a million people can feasibly be built using equipment like that, within a human lifetime. If there's supposed to be a joke in there somewhere, then it's not very funny.

Volvo also makes a LR25 electric front loader. That vehicle weighs almost exactly twice what the ECR25 weighs and has almost exactly double the battery capacity, despite the fact that it has a 48hp electric motor and 43hp hydraulic motor. Rather than 4 hours of runtime, it has an estimated 8 hours of runtime (though clearly not using any significant power, since that would drain the battery in just over 1 hour, no matter what it was doing).

Now take a look at what a real backhoe looks like:

VOLVO ECR355E

It's lifting capacity is equal to the weight of almost 5 of those battery powered ECR25 machines, but it requires a 241hp diesel to run it. I've been on construction sites here on Earth and those diesels are running at full song for much of the time the machine is working. They stop for lunch and when the Sun goes down, but that's about it.

There's nothing wrong with current electric motors. They're already within bad breath distance of 100% efficiency, with most of the traction motors achieving 96% efficiency, and some as high as 98% efficiency. Sooner rather than later, there won't be any electric motor efficiency improvements to be had. Similarly, lots of the power conversion electronics are closing in on 100% electrical efficiency. The batteries themselves are also very near to 100% electrical efficiency if they're not over-heated. That means that the battery energy density needs to drastically increase or existing battery energy density will continue to severely hamper practical electrification of vehicles with high continuous power output demands, namely aircraft / ships / heavy off-road vehicles / construction equipment. Apart from Aluminum-Air batteries, I've yet to see a radically more energy-dense battery technology. Those batteries remain impractical on account of the need to reprocess the Aluminum in the battery into new Aluminum, after a single use cycle, because the chemical reaction turns the Aluminum metal in the battery back into Alumina Oxide ore. That battery can store up to 2.5kWh/kg, the "magic number" that must be achieved to replace gasoline, but every 1kg of Aluminum then needs a minimum of 10kWh of input power, or 15kWh/kg in a practical application of the traditional Hall-Heroult process for making Aluminum metal from Alumina Oxide.

In contrast, excluding the liquefaction processes, the input power requirement for LOX/LCO is 2.821kWh/kg based upon actual designs that have actually been tested by NASA, which is almost exactly as much energy as we get out of it when we combust it. If we did have a more durable SOXE fuel cell to use in our vehicles, then we're at ~69% efficiency, excluding the liquefaction processes. I would find it very helpful to know how to compute those numbers using existing devices running in liquefaction plants at the scale we would need for a single piece of construction equipment that requires 250kWe of continuous power. If we recapture the waste CO2 from the combustion engine or fuel cell, then we could be even higher than that since we don't have to collect more CO2.

I absolutely think we should continue to pursue better batteries, but we simply don't have anything ready to implement at this time, so we're either going to need about a kilo of batteries for every kilo of vehicle mass to supply continuous power and recharge power, if nothing but photovoltaic panels and Lithium-ion batteries are used, or the end result will be a substantial loss of productivity and increase in the timeline required to build out that second branch of human civilization.

SpaceNut · 2020-12-26 16:44:09

I wanted to find out the boiloff rate on mars and did a search in bing "mars Lox and Methane boiloff rate" ... low and behold post 26 of this topic showed up in the first page....

Some would think that during the mission outward that a Cryogenic Fluid Management (CFM) technology would be the way to go but what about on the surface of mars and where is the power to run it coming from?

NASA cryocooler technology developments and goals to achieve zero boil-off and to liquefy cryogenic propellants for space exploration

NASA’s interest in human exploration of Mars has driven it to invest in 20K cryocooler technology to achieve zero boil-off of liquid hydrogen and 90K cryocooler technology to achieve zero boil-off liquid oxygen or liquid methane as well as to liquefy oxygen or methane that is produced on the surface of Mars.

Regular insulated tanks
Minimising propellant boiloff on the transinit to/from Mars

The LOX will need to be kept at a pressure of 150-200 kPa (22-29 psi) in order to avoid freezing the methane. This is well within the standard tank pressurisation range so should not be an issue.
The sub-cooled methane will have a vapour pressure of 30 kPa (5 psi) so the differential pressure on the outside of the methane tank will be 120-170 kPa (17-24 psi).

https://space.stackexchange.com/questio … ip-to-mars

kbd512 · 2020-12-26 17:04:09

SpaceNut,

We'll need 77K cryocooler technology (LN2 temperatures) to liquefy / densify / prevent boil-off of all of the cryogens we need, except for Helium and Hydrogen. The use of cryogenic oxidizers and fuels negate the need to use Helium or Nitrogen pressurants and hopefully we'll store Hydrogen in the form of H2O or LCH4.

SpaceNut · 2020-12-26 17:17:36

https://en.wikipedia.org/wiki/Cryocooler

https://cryocoolerorg.wildapricot.org/r … 18/022.pdf
Study on a High-Power Stirling Cryocooler

https://cryocooler.org/resources/Documents/C18/055.pdf
Ultra Low Power Cryo-Refrigerator for Space ... - Cryocooler

https://cryo.gsfc.nasa.gov/coolers/cooler_types.html

https://www2.jpl.nasa.gov/adv_tech/cool … oolers.pdf

https://www.jlab.org/IR/Cryocooler_Fund … -final.pdf
Cryocoolers for Space Applications #3

https://ntrs.nasa.gov/api/citations/201 … 029261.pdf
High Efficiency Megawatt Machine Rotating Cryocooler …

https://mars.nasa.gov/resources/3336/ma … -profiles/

Aug 20, 2010 · Temperatures range from 120 Kelvin (minus 244 degrees Fahrenheit), coded purple, to 200 Kelvin (minus 100 degrees Fahrenheit), coded green.

So the radiator for the LN2 will still need to be quite large in the thin mars air..and even sinking it to the planets crust means quite a bit to bury...

SpaceNut · 2020-12-27 16:49:58

Earth reference for electrolysis for direct use is HHO or brown gas.

So after its started we can run off from water.

This one breaks down an alternator for low rpm

http://sewboard.cancamusa.net/wp-conten … erator.pdf

Thinking about exhaust gas at pressure why not use the basalt ballon tank.

Most of the content is here Compressed gas balloon rocket for Mars launch

Now if we are creating power from shaft spin... Home Brew Generator sure this under 1,000 watts but its something that can be done.

SpaceNut · 2020-12-27 20:24:15

Combining my post made back in 2017
http://newmars.com/forums/viewtopic.php?id=7762&p=2

Parameters for this is approximately 5 hrs solar to provvide power to produce all the needed fuel and oxygen to be consumed in a 20 hour period with the life support power being untouched form the panels for the 5 hours activly in use by crew.

Liquid Propane or gaseous natural gas are very simular to what we would be doing on mars for liquid or gaseous methane use.

So would someone please calculate the size of the fuels gaseous and liquid as well as the liquid Oxygen tank needed to satisfiy the burn time of 20 hours. Once we know these volumess then I will or others can search for the standard mass and volume for tanks to hold each on mars. Which leaves each day a 5 hr period to do any maintenance on the generator. Or should we have more of them?

http://www.propane-generators.com/propane_usage.php

http://www.booneyliving.com/906/how-muc … rator-use/

Not Saying that the commercial provides will be all that different than what we can find at the local links that follow and not endorsing them either as there are other providers in the world, just using for numbers for standby generator setup to which is what we would be doing.

Since we need 2k watts for life support and probably the same fr other cycled uses we would want for a 75% rating of the generator output would be 2k x 6 x 2 =24kw during the day or for shifts pretty much continous. So thats a 32kw generator.

This product fits that bill Generac liquid cooled generators or from competitor Generac Protector Qs 38000-Watt (Lp) / 38000-Watt (Ng) Standby Generator this one has specifications on its page.

The Full Load Fuel Consumption gallons per hour (GPH) 5.4 is for the max output in watts with a Fuel Consumption 1/2 Load liquid propane (LP)1.7 and for Fuel Consumption 1/2 Load natural gas (NG) 260

http://www.generac.com/all-products/gen … w-rg038-qs
http://gens.lccdn.com/generaccorporate/ … w-48kw.pdf

Natural Gas Liquid Propane
(ft³/hr) (m³/hr) (gal/hr) (l/hr) (ft³/hr)
75% of rated load 361.7 10.2 4.2 16.2 153

The cooling for mars would need alteration depending air or liquid cooling.
The generator mass is on page 8

WEIGHT DATA ENGINE/KW ENCLOSURE MATERIAL
2.4L 38KW AL
WEIGHT GENSET ONLY KG [LBS] WEIGHT SHIPPING SKID KG [LBS] SHIPPING WEIGHT KG [LBS]
560 [1235] 44 [98] 605 [1333]

So based on methane being in a gaseous state or liquified the changes are to the delivery pressure, and orifice size into the same unit.

The stoichiometric ratio of fuel and oxidizer is 1:2, for an methane:oxygen engine.

CH4 + 2O2 → CO2 + 2H2O

1,000 gallon propane tank....
ASME Propane Tank Dimensions

a local suppliers page
https://eastern.com/residential-propane/propane-tanks

http://www.propane101.com/propanetankdimensions.htm

It is said that its only 80% full for the size. Is boiloff rate the means to pressurization?
http://www.missiongas.com/1000gallontank.htm

http://www.missiongas.com/undergroundtanks.htm

http://www.dvorsons.com/Magikitchen/pdf … elines.pdf

http://www.npga.org/files/public/Facts_ … ropane.pdf

How much does a liquid propane tank 1000 gallon tank weigh? 2350lbs. on average
What is the required distance away from a building for a 1000 gallon propane tank? NFPA 58 generally requires above-ground LPG tanks having capacities greater than 500 gallons to be located at least 25 feet from a building. More as the size gets larger.

According to Antius for 1kg of oxygen is 13.1MJ of chemical energy, which requires about 20MJ of input to an electrolysis cell.

That's 5.6kWh/kg. 5.6kWh divided by 24 hours is 233 watts continuous. Of course, if you are only powering that cell during peak sun, the actual power requirement is 1120 watts for 5 hours.

http://newmars.com/forums/viewtopic.php?id=9160

The generators can not run continously and must have maintenance to keep it going which means we will need serveral backup methane generators which are very simular to the natural and propane gas ones here on earth.
The ratings of the output of a generator is give as a max level but its not capable to running at that level but only for short peak periods. typically they are run at 70% output power levels to ensure that they do not over heat.

Here is a typical 22kw unit

NG Fuel Consumption @ 50% Load 216 ft³/hr
NG Fuel Consumption @ 100% Load 310 ft³/hr
LP Fuel Consumption @ 50% Load 2.56 gallons/hr
LP Fuel Consumption @ 100% Load 3.87 gallons/hr

So if we used say 5 gallons hr then for a day we will use 125 a day and for a week 875 a week which is the typical tank on earth for home use of 1,000 gallons.

https://www.convertunits.com/from/ton/to/gallon+[U.S.]+of+LPG
10 ton to gallon [U.S.] of LPG = 415.25305 gallon [U.S.] of LPG

At full load your example 22kW LPG generator consumes 1 gallon of LPG per hour for every 5,684 Watts of output. That'd be 8,760 gallons over the course of a year to produce 49.8MWh worth of electricity. Each gallon of LPG weighs about 4.2 pounds, so 36,792 pounds of LPG over the course of a year.

I remember the name in the article and I think we had topics during the crash years on the hydrogen fuel cells http://www.hydrogenhouseproject.org/index.html

The main issue for earth is regulations and danger of hydrogen.

I remember that there was a ton of solar cells that were used to split the water and it was stored in 1000 gallon propane tanks, about a dozen or so from what I remember.

So going with ammonia will see some of the same issues for those not understanding the regulations or the handling. This would also go the same for methane if we were making it from a sabetier reactor but I digress..

Its the free daily energy that we are capturing for later use in a storage method that we need in a safe an useable manner.

http://newmars.com/forums/viewtopic.php?id=8974

So why are we not using propane or natural gas or for that fact methane in fuel cells since we have that infrastructure as well which can be used as well?

http://cafr1.com/Hydrogen_vs_Propane.pdf

https://www.electrochem.org/dl/interfac … p40-45.pdf
High-Energy Portable Fuel Cell Power Sources

https://www.energy.gov/eere/fuelcells/types-fuel-cells

http://sitn.hms.harvard.edu/flash/2015/ … a-new-way/

https://www.epa.gov/sites/production/fi … _cells.pdf

https://www.nrel.gov/docs/gen/fy01/30298.pdf
Fuel Cell IntegrationA Study of the Impacts of Gas Quality and Impurities

2006 Prototype Propane Fuel Cell Passes Muster In Alaska

And where are they , how much to they cost, what is the life cycle for them?

https://www.fuelcellstore.com/fuel-cell-facts

https://fuelcellsetc.com/2015/03/what-y … ered-home/

https://www.wattfuelcell.com/uses/residential/

https://c03.apogee.net/contentplayer/?c … er&id=1180

https://www.nrel.gov/docs/fy02osti/32405b25.pdf
LOW COST, HIGH EFFICIENCY REVERSIBLE FUEL CELL SYSTEMS

So where there any which are in use
https://www.energy.gov/sites/prod/files … s_2016.pdf

https://www.wired.com/2007/03/backyard-fuel-cell/

https://www.forbes.com/sites/michaelkan … ch-a-flop/

ammonium is NH4

To make ammonia we need energy to gather nitrogen and then to split water so as to put them into this https://en.wikipedia.org/wiki/Haber_process with the thought process is to use excess power to do the work Renewable Fuels: Manufacturing Ammonia from Hydropower

Haber-Bosch (H-B) process. The process combines hydrogen and nitrogen over iron-based catalysts at about 500 degrees Celsius (C) and 200 to 300 atmospheres pressure to produce Anhydrous ammonia (NH3)
3H2 + N2 —> 2NH3

http://environ.andrew.cmu.edu/m3/s3/08formations.shtml

It takes 420 gallons of water to make a metric ton of anhydrous ammonia.

— Can be stored compactly as a liquid (much like propane) at pressures around 125 pounds per square inch (psi);

— Highest hydrogen density of any liquid (50 percent more hydrogen per volume than even cryogenic liquid hydrogen)

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