Internal combustion engines for Mars

kbd512 · 2021-07-20 18:34:37

tahanson43206,

I went on eBay Motors and saw listings for dozens of EZ30 motors, along with numerous other Subaru engines. I obviously can't evaluate the internal condition of the engine by looking at a bunch of pictures of the outside of the engine, but all of them outwardly appear pretty good. A few of them had significant rust on the pulleys and I'd probably avoid purchasing those examples, but there were lots of others that were about as pretty as you could reasonably expect of 10+ year old engines. If you get a re-manufactured long block, then you can be reasonably sure that the motor will run the way it's supposed to.

It'd be very helpful to know if the motor he already has is truly "cooked", or just has a few minor internal parts like bearings or camshaft lobes that are messed up.

SpaceNut · 2021-07-20 22:32:20

Thanks all as mentioned its a gamble when making use of used from junkyards as there is no guarantee as what you get for the money will be any good for long term use no matter whom the seller or reseller says for engine condition. The mechanic that is the friends garage makes use of the ebay plus others to aid for engine replacement as well.
Since the 2005 escape is running the push for quick replacement can proceed with selection for long term in mind. The big thing is to get a good engine that can last as its costing to much to have bought the vehicle which is growing into a money pit....

tahanson43206 · 2021-07-21 06:11:30

For SpaceNut re #202

Thanks for the good news the Escape is running!

One option available to you that might not occur to you, since you are still (relatively) youthful in the context of this forum, is to take a tax benefit by donating the Subaru to a charity that is set up to accept such donations. The car is in running condition (albeit with a knock) so you should be able to claim whatever the blue book value is. If you can pull that off, you'll have cash in hand for your next venture.

I am (of course) unable to know what options beyond that might look feasible to you, in your specific situation, but I would imagine you would be happier over the longer term if you were able to (somehow) wangle an all-electric transportation solution.

The manufacturer might be thinking about offering an electric vehicle, and they might be willing to consider a demo driver for a test vehicle, if you were to inquire.

(th)

kbd512 · 2021-07-21 12:19:56

tahanson43206,

In general, open-deck block designs using thin wall castings, which is what the EZ30 motor is, are not particularly durable engine designs. They're made that way to achieve a specific manufacturing cost target. That probably explains why there are so many of them for sale on eBay Motors. Subaru's previous design that the EZ30 series replaced, while still open deck, used much thicker casting walls, and there's a dramatic difference between the prior generation motor and the EZ30. Overall, the EZ30 is every bit as heavy as a LS V8 Aluminum block design, also an open deck Aluminum block design from GM, but the LS has much thicker cylinder sleeves and casting walls, at least 3 times as thick when you include the thickness of the iron cylinder bore liners, as those on the EZ30. The LS block is also a single piece casting. Everything I've read about the EZ30's design is that it consumes more oil than it should, is not particularly fuel efficient with a turbo added to it (a poor turbocharging design / setup, but they come from the factor that way), and is very prone to head gasket sealing failures in stock (unmodified) form due to cylinder bore distortion. Any small local warping or hot spot caused by improper torquing of the bolts (distortion during assembly) or from coolant loss (warpage due to boil-off of the engine coolant) around the cylinder, and it's time from a rebuild. None of that describes the LS series, which is why the engine is so popular for swapping into older model vehicles.

All or most of the aftermarket Aluminum LS blocks are closed deck designs, so that should tell you how open deck Aluminum block designs are perceived by the performance world. They save the OEMs a few extra dollars on a few extra pounds of Aluminum, but they're bad news for ultimate durability if they're almost exclusively engineered to save the manufacturer money rather than achieve good durability. Open deck cast iron blocks tended to be much more forgiving, but this cost and weight savings measure doesn't directly translate to an equivalent Aluminum block with equivalent external dimensions (packaging sizes), meaning you must either greatly increase the thickness of the sealing surfaces for sake of rigidity in alloy blocks, or use a closed deck design. The simplest solution is to use a closed deck design. It costs more money, but it's also very rigid, so there's very little deflection / cylinder bore distortion when the engine is hot and under load.

If it sounds like I'm biased, it's because I am. I'm biased towards designs that have proven their durability in operation over many years and many hundreds of thousands of miles of driving, with boring regularity, because that means we don't need to redesign or re-manufacture things after they've been produced by the millions. If there's a simple solution such as using head studs vs bolts, and that resolves a design problem, then I'm also biased towards the simplest and cheapest solution that actually works.

To that point, there's nothing intrinsically wrong with using lots of Aluminum and plastic in the engine, so long as it doesn't lead to a never-ending series of very expensive repairs. If you can make something just as durable as steel, but lighter and cheaper, then do it. The problem is that most of the time you can't.

High temperature plastic is a boon to cold air intakes by reducing absorption of heat from the engine by the intake charge. Plastic fluids reservoirs and caps never rust. Fiber reinforced plastic oil pans can be lighter than Aluminum or steel, but not less expensive. Some types of plastic are nearly impervious to the corrosive chemical compounds formed in engines or hydraulics or coolant systems. Aluminum seems to be the material of choice for pistons / heads / radiator cores / pump housings. Steel is the material of choice for crankshafts / camshafts / connecting rods / rocker arms / valve springs / studs or bolts / etc. Engine blocks can be made from Aluminum or Iron, provided that they were specifically designed to be made from those materials. Titanium is good for valve spring retainers and large intake valves in order to reduce weight and valve train loading, but little else. A stainless steel or Inconel is best for exhaust valves. Nearly all racing / marine / aviation engines use Inconel exhaust valves, and it's nearly a requirement if the engine has been turbocharged or supercharged. Powdered Ductile Iron is good for hardened valve seats. No other material has held up quite as well over the long term, although many different specialty valve seat materials have been used for specific applications. Modern connecting rods can also be made from powdered steel and give very good performance in most applications not related to pure performance. Ideally, cranks and cams would be machined from forged billet stock. Main caps for crankshafts can be cast ductile Iron or Aluminum or steel, but billet steel is by far the strongest for a part with that can't tolerate significant dimensional changes. If dimensions could be changed at will, then Aluminum alloy would be the material of choice due to weight and stiffness for a given weight. Pretty much every moving part subjected to metal-on-metal wear lasts a lot longer with WPC treatment (a micro shot peening process that drastically reduces friction, to an even greater degree than polishing, comparable to very expensive low friction aerospace coatings).

For combustion engines designed for use on Mars, there's no benefit to "making the engine a little bit cheaper", so high grade steels with liberally applied aerospace coatings and/or micro shot peening should be used throughout. Large displacement engines running at low-rpm will also help with service life by reducing friction-related wear associated with smaller displacement engines running at much higher rpm.

The synthetic oils that GW mentions are little better than traditional motor oils for extended duration engine operation, but for engines that experience frequent starts and stops, synthetic really shines there. However, over time a hard flaky plasticized layer forms on parts subject to frequent thermal cycling, where the oil's additives package has polymerized onto steel components like the cam and crankshafts and bearing surfaces. When you take an engine that used full synthetic apart, this residue comes off as small hard / sharp flakes of what is essentially plastic. If you change the oil more frequently, then this is less of a problem, but synthetic oil is typically changed less frequently because it's more expensive than conventional motor oil, due to that additives package. You can still run the cheapest oil available so long as you change it more frequently. In the same way that an electric fuel pump starts running before you crank the engine over, if you also had an electric oil pump that produced sufficient oil pressure to ensure that all bearing surfaces were properly lubricated before engine start, that would have the same net effect as synthetic motor oil, without the use of a much more expensive oil. That said, virtually no engines used outside of racing have that design feature, because that's one more part that could break or fail.

GW Johnson · 2021-07-21 12:39:06

I can't speak to a junkyard engine, but when buying a used car, look very closely in the engine compartment and underneath the car on its underbelly or frame for signs of oil leaks. They might have cleaned up the engine real pretty, but few get rid of the greasy dirt that accumulates down underneath. The usual culprits for such oil leaks are the valve cover gaskets and the front (timing) cover gaskets and seals.

Look under the running engine for drips of anything. The usual culprits are power steering pumps/lines/rack-and-pinion cylinders. Look also for water seeps or leaks near the water pump, on the radiator, and the hoses and heater hoses. An engine oil drip is not so common to see, and brake fluid drips even rarer. Look closely underneath the bell housing joint from engine to transmission: leaks there are fairly common. If engine oil, the rear main seal underneath the flywheel is bad. If transmission fluid or gear lube, the transmission will need work.

See that it runs smoothly at idle, including feeling the exhaust pulses out the tailpipe. The valves are leaking or the valve timing is bad if these are erratic in strength. They should be tiny and very smooth. Gun the throttle with the hood open, watching for engine motion. If it twists multiple degrees, the engine mounts are bad. If it is bouncing back-and-forth at idle, the compression is uneven. That would call for a dry compression test followed by a wet compression test.

If the dry compression tests shows a low cylinder or two, but not catastrophically low, but the wet test shows all more even, the problem is worn or damaged piston rings. If the wet test shows the same cylinders lower, the valves on those cylinders are not sealing. Worn rings burn lots of motor oil, and you should see blue smoke in the exhaust upon accelerating the car. Leaking valves are going to burn, requiring the cylinder head or heads be removed and repaired.

Jack up the front of the car so that both wheels are off the ground. With the engine running, operate the steering wheel lock to lock. If the power steering fluid level is good, but the pump makes a whine, that power steering pump is worn out and will require replacement. Engine off, grab each wheel at 6 and 12 o'clock, and push-pull feeling for play. If you find some, the wheel bearings are probably bad (and you should hear noise when you spin the wheel). Grab at 3 and 9 o'clock and push-pull for play. If you find some, the front suspension is worn out and requires a rebuild. If you have a 2-foot pry bar, try to pry underneath the wheel to raise it up. If it moves as if free play, the ball joints are bad.

You need to test drive the car. If it has front drive axles, and you hear a clicking noise as you round a curve, the axle joints are worn out. If you hear a grinding noise when you step on the brake, the brakes are shot, and are already destroying the rotors or drums. If it does not immediately "go" when you push the accelerator, there are engine or fuel system troubles. This is especially prevalent with spider injectors on V-6's.

If it handles poorly, push down on each corner of the car at its fender, release suddenly, and look to see if it reverses direction before it stops moving. If it does, the shocks are bad.

If I think about it a while, I could come up with more tests you could run as a prospective buyer. But that's enough right there to scare the wits out of any seller.

EDIT UPDATE 7-22-21: Most vehicles today have timing chains with tensioners. A lot of imports a few decades ago used rubber timing belts. The rubber belts have an approximate lifetime of about 70,000 miles. Anything after that is borrowed time, asking for a belt break, and in many cases that leads to pistons hitting valves, doing very severe damage. About the max you should expect out of timing chains with tensioners is 150,000 miles. Whether you know it or not, at about that mileage, the chains and tensioners need to be replaced. All that stuff comes in a standard timing kit available for each engine. You have to pull off all the accessories in order to pull the front cover (timing cover) to do this. Smart folks replace the water pump, thermostat, any cam seals, and they crank seal while they have it apart.

All of that is why it is critical to get an honest and accurate odometer reading when you look at a car as a prospective buyer. Usually, the rod and main bearings are good for over 200,000 miles, and in the bigger pickup trucks, over 300,000 miles. However, if a rod bearing has "spun" in its mounting, it will make a ticking noise that quickly becomes a rod knock sound. Unrepaired, it will throw the rod. Worn rod bearings never tick, they just knock.

Fuel pump failure is getting to be quite common. These are electric pumps mounted inside the fuel tank, integrated with the fuel quantity gauge mechanism. They fail for any number of reasons, and often quite suddenly. If you have spark and compression, check for fuel at the fuel injectors by spraying brake cleaner spray into the air inlet. If the engine runs while spraying, but not otherwise, your fuel injectors are delivering no fuel. Be sure and change out the fuel filter while you are changing the pump out. It's a big, dirty job, no point in screwing around, just do it right.

GW

Last edited by GW Johnson (2021-07-22 12:27:12)

kbd512 · 2021-07-21 14:14:45

tahanson43206,

You should put search terms in for that post that GW just made.

GW,

Thank you. If you do have time to commit to writing other simple tests for evaluating a motor vehicle and engine / transmission, feel free to post them here.

SpaceNut,

I'm thinking about creating a separate topic for Earth-bound land motor vehicle evaluation.

Edit:

One simple way to evaluate a vehicle is to take a qualified and experienced mechanic with you before you purchase a vehicle. That can save many thousands of dollars and a lot of grief further down the road.

Edit #2:
A car having bad shocks or bad brakes is not necessarily a deal breaker, but it should be reflected in the price of the vehicle. If you can reasonably do the repair work yourself, then the most you can save on a typical repair bill is in the 30% to 40% range, as the rest is parts and equipment to conduct the repairs.

Last edited by kbd512 (2021-07-21 14:28:46)

tahanson43206 · 2021-07-21 17:39:04

For kbd512 re #206

I completely agree! The only question (for me) is how to do justice to GW Johnson's post #205

SearchTerm:Used car evaluation
SearchTerm:Car used evaluation of guide by GW Johnson

Many of those tips I've heard before, but some are new.

In any case, the advice by kbd512 is what I've used over the years, with the slight difference that I've paid for a trusted shop manager to inspect a prospective purchase. In my way of thinking, the investment up front is more than worth every penny.

Related is service history. I've paid extra to have a dealer handle service when I have one available, and I record every service in the owner's manual. Those are becoming less common, apparently, with computer record keeping (by dealers for sure).

For kbd512 re #204

Thanks for another comprehensive review of engine design considerations and results in the field.

SearchTerm:block engine aluminum vs steel and many other aspects of engine design

(th)

SpaceNut · 2021-07-21 19:52:13

Actually tahanson43206, I have heard of people that have taken the car in for an auto inspection while out on a test drive as well.

The replacement engine is also be evaluated even if the auto has been heavily damaged during running conditions with putting enough time on and check ing many of the things that GW has suggested as you get the best chance for success from one you can know its condition on rather than the one which has already been pulled from the vehicle.

GW Johnson · 2021-07-21 21:52:45

Well, a couple of years ago, I came out of retirement to help a friend. His auto repair shop was undermanned. 2 years later, I am still helping. What I described for engine and vehicle evaluations is just what we do in that shop. There's also things like alternators, air conditioning, and power windows and power door locks to worry about. I didn't talk about that stuff in the post. But I could. Brakes, too.

I had done my own maintenance and repairs on ancient air-cooled VW's for some years while serving as a defense industry engineer. That plus getting ASE certified in engine repair and engine diagnosis got me my first job after the rocket plant closed. That was in an automotive and manufacturing engineering program at Minnesota State. That cert expired 2 decades ago, so what I knew then is obsolete now, except for very old cars. But, despite that obsolescence, I have been able to effectively help diagnose and service at least some aspects of even the latest models.

I just helped fix an air conditioner today; I noticed a leaking fitting, and I found an O-ring of the right size (and material!!) to replace the bad one that caused the leak. From there, it was just evacuate, confirm no further leaks, and load freon. Yesterday, it was assisting a much more experienced mechanic to drop a fuel tank, replace the fuel pump, test that pump (and the fuel quantity gauge), and reinstall the tank. What wouldn't run before, ran just fine afterward. We had to diagnose it off a fuel injection rail pressure test; it flowed fuel, but at far-insufficient pressure to make the injectors work.

My knowledge of how to build solid rockets and solid gas generators is just as grounded in practical experiences as in theory and design analysis, as my mechanics abilities. That extends to test as well as design. It applies to ramjet work as well. And I did fire protection work, foundation design, and hazardous waste disposal, too. As well as teaching (from 7th grade math to graduate school strength of materials). Plus I did aircraft STC work with the FAA.

Did a lot of things. Did them well. I'm an old guy. There was time to do all that stuff.

GW

Last edited by GW Johnson (2021-07-22 12:14:14)

Mars_B4_Moon · 2021-11-29 19:42:55

It is great that the Raptor was developed by SpaceX keeping Mars in mind. One thing I liked about the Russians is even during Soviet times they explored un-conventional fuels in some of their rockets and sanctioned convince Russia explore its own different types of rocket fuel. Why SpaceX uses Methane in Starship...because he's not going for the Moon because Musk's Starship is going to skip the Moon and it really is a rapidly reusable Mars rocket?

tahanson43206 wrote:

the Russians have a lot of experience working in the far North.
I wonder if there are public documents about their experiences with machinery, and their "best practices" guidelines.
(th)

Speaking of cold, I watched an interesting 'reality tv' show once called 'Ice Road Rescue' I don't know how real this shows are, sometimes I feel they add more drama but it was mirrored on vimeo or dailymotion or some place I will see if I find a link again during the week on some video streaming site, there might even be clips on you tube. The show was a rescue show dealing with people stranded in the ice cold mountains of Norway, rescue workers help stranded people stuck in the snow, then tell them what they did wrong a nd try to repair or save their problem on the side of the road. Some of it was pretty simple resuce stuff like pulling a Truck back onto the road that had almost fallen down an icey cliff mountain while hoping the cable didn't snap and other times they faced more complex problems. I'm pretty sure there is a Canada or US verison of the show called Ice Trucker or Ice Highways or something.

SpaceNut wrote:

Here is my post of the use of the pair in a solar chimney design

Very interesting read, thanks for the link

Last edited by Mars_B4_Moon (2021-11-29 20:28:20)

SpaceNut · 2021-11-29 20:05:22

Not really in the correct topic Mars_B4_Moon thou close Yes this topic is about the use of fuels not normally thought to be ones for use in an engine and if we are using what we would normally not use for other things which we have expended energy to create its a waste not want not that we are trying to leverage.

Calliban · 2021-12-20 08:10:22

Given that fuel is something that we must manufacture on Mars and batteries must either be manufactured or imported; grid connected transportation may ultimately be more desirable in many applications.
https://www.lowtechmagazine.com/2009/07 … trams.html

Modern factories on Earth are huge 2D floor spaces, with machinery positioned on a grid arrangement. Transportation within this environment could be provided by electric vehicles drawing power from an overhead cable or mesh and grounding through a steel floor. Likewise, for common transit routes on Mars, wheeled or tracked vehicles could draw power from a single overhead cable, which is segmented to provide sections of both +ve and -ve. This allows use on unimproved tracks. But it does require the presence of a pole carrying the cable. These arrangements allow electrical energy to be consumed as it is generated, without any need for storage and without the weight imposed by batteries or fuel tanks.

On another thread, the topic of nuclear powered heavy vehicles is being discussed. These have the similar advantage that power is generated as needed, without the requirement for storing energy. However, the need for shielding and power-weight limitations may impose limits on where this solution is appropriate.

Last edited by Calliban (2021-12-20 08:14:22)

tahanson43206 · 2021-12-20 10:38:49

For Calliban re #212

Thanks for providing the seed for a possible new topic, with focus upon grid transportation.

It is possible we do not have such a topic, and if that proves to be the case, please consider starting one.

This ** particular ** topic is about internal combustion engines designed for optimum performance on Mars.

We are showing over 200 posts in this topic, so it is possible significant contributions have already been made to the collection of knowledge, best practice, good advice for those designing equipment for Mars.

However, introduction of batteries or electric power lines, railroad tracks or tunnels is not a good fit for this topic.

(th)

SpaceNut · 2021-12-20 13:54:24

We need independent vehicles for mobility and having to add in infrastructure to make a set path function goes against mobility that is flexible early on. Having rails means we are no longer in exploration but are sedimentary.

SpaceNut · 2022-01-17 20:45:49

Astron Aerospace Reimagines The Internal Combustion Engine

The Astron Omega 1 is a one-of-a-kind design. Astron has divided a four-stroke engine's four strokes into two independent chambers, with a pre-chamber in between. Two primary shafts are stacked vertically and coupled with synchronizing gears so that they rotate at the same RPM in opposite directions. Four rotors are placed on the two shafts and run in two pairs, one on the front end for intake and compression strokes and the other on the back end for combustion and exhaust strokes. A rotary disc valve and a pre-chamber are located between the two sets of rotors.
If you're thinking what I'm thinking, that this motor resemblers a Wankle rotary engine, you'd be right.
Astron Aerospace, The Omega 1, in its current form, tips the scales at just 15.9 kilograms and produces a whopping 160 horsepower and 170 pound-feet of torque. It idles at 1000 RPM and redlines at 25,000 RPM.

kbd512 · 2022-01-17 21:31:23

Given a 25,000rpm redline, that thing will last for a matter of hours before it eats the seals. The eccentric shaft and rotors may hold up fine, but the seals in the Wankel design (all of them) have always been its Achilles heel. These engines suffer from severe differential heating, and I've spoken to a number of different engine shops and custom fabricators who work on Mazda 13b engines. All of them have said it's an intractable feature of the design, and no matter what they tried, it didn't work. You can boost the living hell out of them, which has been done by virtually all racers, but you'll be tearing the engine down to replace the seals in no time.

There was one British design, by Advanced Innovative Engineering UK, that recirculated the exhaust gases around the motor in an attempt to evenly heat the rotor housings. I've no idea how successful they've been, but they do offer small engines for light aircraft. Roton is another UK-based corporation that makes Wankel engines for drone-type light aircraft. A bunch of different aerospace and automotive companies have sunk crazy money into Wankel engines, but only Mazda's Wankel engines have withstood the test of time. That said, for constant high power output in a small / lightweight package, only gas turbines are capable of greater sustained output. Anybody with the money will choose a gas turbine over a Wankel for that reason.

SpaceNut · 2022-01-27 18:21:06

Some more on a new design wankel.
This New Engine Could Save Internal Combustion From The Scrap Heap

The Omega 1, which is designed to work with a variety of fuels, is compact and powerful with the goal to produce very low or no emissions. It lacks an offset crankshaft, reciprocating pistons, and eccentric shaft, just like a Wankel rotary engine. However, the Omega 1’s design circumvents at least one issue with Wankel engines – exhausts gas overlap.
The Omega’s one design has a pair of chambers with a pre-chamber separating cold intake air from hot exhaust gas. The Omega uses four rotors mounted on two shafts, running in pairs. The front pair handles intake and compression while the other handles the combustion and exhaust. The stacked rotors are coupled with synchronization gears, so they rotate in the opposite direction at the same speed. Astron also says the Omega’s design doesn’t suffer the same sealing problems, and it’s an entirely linear unit.
The engine’s design allows someone to stack multiple ones together, increasing the output. The standard Omega 1 engine weighs just 35 pounds and can produce 160 horsepower (119 kilowatts) and 170 pound-feet (230 Newton-meters) of torque. The company claims it has a working prototype, so maybe the internal combustion engine isn’t dead after all.

tahanson43206 · 2022-04-28 17:16:40

For GW Johnson re question about CO/O2 operating temperature for an existing, stock, internal combustion engine.

The last post in this topic was fairly recent, in January of this year.

(th)

kbd512 · 2022-04-29 08:16:22

tahanson43206,

CO flame temperature when combusted with air (O2/N2 mix) is variously reported as 2,121°C, 2,400°C, or 2,468°C. CO flame temperature when combusted with pure O2 is stated as 3,220°C. CH4 flame temperature in pure O2 is 3,460°C and H2 is 3,080°C. Wikipedia reports that CO's autoignition temperature is 609°C and its flashpoint is -191°C, lower explosive limit is 12.5% and upper explosive limit is 74.2%.

We'll use the flame temperature values from this article in Science Direct:
Flame Temperature

I believe they were derived from this textbook:
Combustion (Fifth Edition) by Irvin Glassman, Richard A.Yetter, Nick G.Glumac: Chapter 1 - Chemical thermodynamics and flame temperatures

Engineering Toolbox states that complete combustion with Oxygen / O2, you get about 18.2% of the thermal energy of Methane / CH4 (23,867BTU/lb) from Carbon Monoxide / CO (4,344BTU/lb).

1BTU = 2.326kJ/kg

However, this document from NIST reports different values based upon experimental data obtained by the Fixed Nitrogen Research Laboratory:

THE HEATS OF COMBUSTION OF METHANE AND CARBON MONOXIDE By Frederick D. Rossini (Bureau of Standards Journal of Research)

They did have difficulty igniting the CO, so they added 0.1% H2 gas to the CO to make ignition easier (may explain the different energy output values, or it may not).

kbd512 · 2022-04-29 08:43:38

tahanson43206,

Anyway, what all of that data seems to suggest to me is that CO / O2 is most practical using a high-compression spark-ignited direct-injected engine with some level of CO2 diluent added and/or exhaust gas recirculation. Someone makes a spark ignition system that delivers so much energy that it produces plasma. Roughly speaking, I'd say you need about 3X more ignition energy to initiate combustion. I don't mean 3 plugs per cylinder, either, I mean 3X more Joules of electrical energy delivered per plug. If a typical high-energy spark plug delivers about 200mJ, you might need 600mJ or more. There may be a way to get the engine to "diesel" using a greater percentage of hot CO2 from the exhaust gas, but lighting off will be tricky to say the least. The engine will have to run hotter than normal to reduce ignition energy. The autoignition temperature of Carbon Monoxide is 3X that of diesel fuel, well in excess of both gasoline and diesel. This is going to be similar in difficulty to trying to light off Nitro-Methane in a top fuel dragster at WOT, where so much fuel is being dumped into each cylinder that it's pretty close to hydro-locking the engine if the mixture doesn't light off.

GW can tell you if he agrees or not.

tahanson43206 · 2022-04-29 11:38:49

For kbd512 re #219 and #220

Thanks very much for the research and links to help to develop this idea. Using CO2 as a diluent is a concept I recall from earlier rounds of discussion. That CO2 needs to be well filtered, just as is the case with atmosphere on Earth.

The difficulty of ignition you discovered in your research is a challenge. Priming with Hydrogen is more convenient on Earth than it would be on Mars.

If a design team is working on a concept for a tunnel excavation machine, I can imagine comparing alternatives, with electric operation having an advantage due to the confined volumes.

On the other hand, an expedition or a surface construction team might find an all chemical IC solution more practical.

In either case, if a nuclear plant is not readily available, then it seems to me likely a chemical energy storage solution may prove more practical than a battery energy storage system.

(th)

kbd512 · 2022-04-29 14:59:00

tahanson43206,

You'll definitely need to run this kind of engine a bit "hotter" than most liquid-cooled piston engines. Some kind of non-aqueous coolant is required, the engine oil needs to be a full synthetic with higher viscosity and good thermal breakdown resistance, steel pistons will be used in hopes of creating a "hot spot" on the piston crown to assist with mixture ignition, and, as already noted, the spark plugs need to deliver a massive wallop of energy to get the party started. I don't think pure compression ignition operation would be practical and it might be unworkable. Basically, you'll need hotter operating temperatures, plus diesel-like compression ratios, plus direct-injection of all working gases, plus high energy spark delivery, plus high temperature exhaust gas recirculation to bring the mixture somewhere near to autoignition. You'll probably also have to advance ignition timing more than usual to ensure the combustion event happens when you want it to.

SpaceNut · 2022-04-29 17:19:04

Sounds like we need molten sodium or salt or other phase metal product for the coolant.

Oil might be a problem due to how hot the block will get even with a cooling system as we need to keep it at liquid temp as well so as to not have solids form.

tahanson43206 · 2022-04-29 20:04:06

For SpaceNut re #223

Molten Sodium or salt is a coolant Calliban would recognize, in his nuclear reactor posts.

It is inspiring to find it considered as a coolant for a standard-issue internal combustion engine from Earth.

For kbd512 re #222

Thanks for continuing to explore this topic further ...

While I can follow most of your description of the situation to be dealt with, I came away from reading the post worried that a stock engine might not be up to the job.

What I was hoping is to find a solution that allows an expedition to include a stock engine (along with lubricants and coolant supplies) in the manifest, with the intention of making CO and O2 on site.

While solar panels are unreliable and risky, for the brief time in which they actually work, they could (presumably) power a system that splits CO2 and stores the products as gases.

Because of the energy required to liquefy these gases, I am guessing that the expedition would decide to simply compress the gases as much as practical and just go with large tanks.

I saw an announcement recently about advances in manufacture of very light weight tanks for hydrogen powered vehicles. Such tanks might work well in the situation we are discussing in this topic.

Thanks again for keeping the topic moving!

***
For SpaceNut ... any chance we could just use water as a coolant?

One concern I do have, and which has not yet been addressed in this topic (as far as i can remember) is radiator design for Mars. Mars is colder, but the atmosphere is a wisp close to nothing, so I'm wondering how well a standard radiator would work?

The fan for a standard radiator might have to spin more rapidly than on Earth?

(th)

kbd512 · 2022-04-30 00:15:35

tahanson43206,

I would try for compression ignition first, but there are no guarantees on that working acceptably well. If we can pre-heat both the fuel and oxidizer using exhaust gas, then perhaps we can make a diesel work. This is something that should be attempted with a Cummins 6BT engine, because so many of the required parts upgrades are readily available.

Draft Parts List
~$1,800 Hamilton Cams "Warhead" improved cylinder head (thicker casting in all critical areas; intake plenum removed)
~$3,300 set of 6 Mahle "Monotherm" forged steel pistons
~$2,500 - $3,300 set of 6 forged or billet connecting rods from any of the following:
CP Carrillo (H-beam) or D&J Precision Machine (X-beam) or Scheid Diesel (billet)
~$1,200 Inconel intake and exhaust valves
~$700 Stainless steel exhaust manifold
$200 Stainless steel exhaust studs and bolts
$1,200 Inconel head stud kit
$1,000 block girdle
$400 Inconel main cap stud kit

After we throw about $20,000 worth of high-end parts at this engine, not to make "big power" but merely "standard power" at greatly elevated operating temperatures, then the engine will be able to withstand 400°F operating temperatures. We also need stainless steel valve covers (nobody makes these), silicone seals, a billet stainless steel accessory case and accessory case cover (nobody makes that, either), and billet stainless steel intake plenum (again, these are normally Aluminum parts). There can't be a single piece of Aluminum on this engine, because it will either crack due to coefficient of thermal expansion differences or it will melt / lose required strength. If the engine was operated in an Earth-like atmosphere, then you'd be able to light a cigarette on many parts of the engine. You'd also have to spin the radiator fan to jet engine rpm levels for it to do any useful work, so that's another custom part that you can't buy. If you had about $100K to spend, then this would be a fun project to tinker with. I think it could technically work, but the fallback would be spark ignition.

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#201 2021-07-20 18:34:37

Re: Internal combustion engines for Mars

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