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So purely electric vehicles are clearly the future. Battery tech is getting better every day and EVs are gradually getting cheaper. However, they don't sound cool. They don't really sound like anything at all. So let's say humanity advances to the point where we find several habitable planets that we begin colonizing. Because of the lack of infrastructure, would it be more practical to have ICE vehicles that we can synthesize fuel for? Or would it still be more sensible use a centralized power source to charge battery vehicles? Let's assume that humanity found FTL by some means but did not develop the technology themselves. I think expanse-level tech is probably as advanced as it gets in this setting.

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    $\begingroup$ The title of the question asks about piston engines (which are probably doomed to be consigned to the museums), but the body of the question asks about internal combustion engines in general (which I am quite sure will be used for a very long time). These are very different questions. Rocket engines are internal combustion engines. Turbine engines are internal combustion engines. (Think about steam engines. Piston steam engines are long gone, but turbine steam engines are widely used to in electric power plants and atomic submarines and so on.) $\endgroup$
    – AlexP
    Mar 14 at 18:11
  • $\begingroup$ hydrogen internal combustion engine vehicles could be used for contaminated, surplus, or just low quality rocket fuel. Stuff that would not work well in a fuel cell. especially if they are mining gas giants for hydrogen. Gasoline vehicles became common because gasoline was a waste product and thus dirt cheap. $\endgroup$
    – John
    Mar 14 at 20:17
  • $\begingroup$ What do you specifically mean by "has a place?" We have societies on Earth today who use horse-drawn carts. I still play vinyl records. People still use shovels rather than renting mini excavators. It's trivial to come up with rationale to excuse the use of combustion engines among space-faring civilizations... but that depends on your definition of "has a place." After all, if they only exist in museums, that's a place. $\endgroup$
    – JBH
    Mar 14 at 21:23
  • $\begingroup$ BTW, while I agree that electric vehicles are "clearly the future," you should be mindful of phrases like that. EVs only exist here in Montana in the bigger cities for in-city use because the batteries still can't handle the cold or the distances. And we're still charging those lovely batteries with primarily coal, propane, or diesel fueled power plants, which isn't an improvement over gas (but the driver feels self-righteous, that's enough, right?). When EVs are powered by solar, nuclear, or hydrogen fuel (or similar), then they're "clearly the future." Until then, they're just a novelty. $\endgroup$
    – JBH
    Mar 14 at 21:29
  • $\begingroup$ Totally depends on the intended level of handwaving involved. Have we invented anti-grav? Small cold-fusion power sources? teleportation? Sub-orbital ramjets? Whatever is sent, can the people there tear it down and fix it? They're at the loooong end of a supply chain. Possibly a micro-organism there breaks down whatever material is used to create the things, so now they rely on muscle power, or 6 legged cat power, or... where are you going with the STORY, not the trivial supporting things. $\endgroup$
    – CGCampbell
    Mar 15 at 14:30

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This is a false dichotomy

You present the choice as being between synthesized, transportable fuel (distributed?) and a "centralized power source".

The beauty of electricity as a power source is that there are myriad ways to generate it, and the electricity thus generated is indistinguishable from electricity generated by any other of those means.

So I would say that if battery technology is Expanse-level, it makes more sense to have electric vehicles rather than internal combustion. ICEs are incredibly complicated mechanical marvels - an electric vehicle can be made very simple. They're easier to maintain, with futuristic high-efficiency solar cells, you will never be stuck anywhere without fuel - they are wildly more practical.

So, where do I get to hear the roar of the engines?

Borrowing an idea from the Honorverse, may I suggest: the Society for Creative Anachronism.

These days, the SCA is mostly concerned with Medieval or Renaissance tech, but if you've got spaceflight and are conquering new planets, the 70s are going to seem a long way off. So you have a collection of hobbyist weirdos who spend their evenings and weekends building perfect reproduction models of 1970s coupes, cruisers, and muscle cars. (Running on alcohol, obviously, because no one's going to bother to set up a fossil-fuel industry.)

So Piotr Suzuki-Schmidt (SCA name: Tony Malone) has a replica Dodge Challenger that he races on Sundays against his fellow SCA members while other colony members watch, bemused, from the sidelines.

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  • $\begingroup$ In the Honorverse internal combustion engines burning hydrogen are widely used. Honor H. herself is almost killed when the Grayson freedom fighters shoot down a hydrogen powered shuttle she was riding on, and Queen Elizabeth III comes to power due to a tragic accident suffered by a hydrogen powered pleasure yacht. True, piston engines can only be found in quaint places. $\endgroup$
    – AlexP
    Mar 14 at 18:48
  • $\begingroup$ My impression from those scenes was that the hydrogen was present to power an internal fusion bottle, but it still leaked and exploded the normal way if the fuel tank was ruptured. $\endgroup$
    – jdunlop
    Mar 14 at 18:50
  • $\begingroup$ In fact, Weber states this explicitly - small craft are powered by laser-inertial fusion (rather than the mag bottles on larger ships). So it's not a combustion turbine, it's electrical, with a big tank of fuel that can still go "boom". $\endgroup$
    – jdunlop
    Mar 14 at 18:54
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    $\begingroup$ Calling an electric vehicle simple is only sort of true. Keep in mind the one thing keeping EVs from having already taken over on Earth: making a good battery is actually incredibly complex, far more complex by itself than the entire drivetrain of an ICE vehicle. A colony is probably unable to make batteries and will need to import them if they break, however ICE vehicles can be fixed fairly simply without a specialised foundry. $\endgroup$
    – Turksarama
    Mar 15 at 2:04
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    $\begingroup$ @Turksarama: What makes batteries complex is the need to have parts of them chemically deform and refofrm without their shape being distorted in such a way as to short out or create other similar problems. Manufacture of primary-cell batteries is pretty simple if one can get the raw materials. If e.g. a colony was located in a crater on a planet which received an essentially unlimited supply of solar energy, a facility that could reduce the by-products from spent primary cells and build new cells wouldn't require anything overly exotic. $\endgroup$
    – supercat
    Mar 16 at 21:07
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Of course you can have them!

Electric vehicles would be charged either from local power plants or from the power grid. Local systems might be solar cells, hydropower, geothermal, stuff like that. Perhaps even burning wood. Mining coal requires a scale that would no longer be local, it would be the colony-wide grid. Other means to power a grid might be fission or fusion.

Assume that a colony-wide power grid is not an option at first due to the dispersal of the settlements and the terrain in between.

Using a solar array on the roof of your house to recharge the rover sounds really good if the rover spends most of the day next to your house, and only occasionally ventures to the fields or to the market village. If the rover is roving a lot, you might need several battery packs, leaving some at home while the others are used. That's expensive, and batteries don't have an infinite number of cycles, either.

Drilling for fossil fuels and refining them might look really good from a storage-and-distribution viewpoint. The tanker truck makes the round of the farms, refuels their tanks, and the rovers and tractors are refueled from there.

An alternative to fossil fuels might be biofuel, either vegetable oils or alcohol. Again they can be stored in liquid tanks. These fuels might be viable at a smaller scale than oil refineries. Imagine little stills or oil mills in every farm, making them self-sufficient in fuel!

On top of that, you get the question of local repairs to the vehicles. Historically, electric vehicles used to rival internal combustion, but at the beginning of the 20th century combustion completely outclassed them. Only in the last years has battery power started to catch up. If high tech is limited by the need to build the tools to build the tools, the easier technology might win.

So you might have:

  1. The initial expedition brings battery-powered vehicles, which recharge from the reactor of the starship or shuttle. They are limited to a certain radius around the landing field.
  2. Early settlers bring a mix of fuel-cell vehicles and internal combustion, fueled by biofuels which can be produced in outlying farms.
  3. As the colony grows, they debate going to a fossil fuel economy (if such fuels exist), or to expand the power grid from the starport/capital city to the outlying settlements, or both. The decision depends on geographic and political factors.
  4. The niche for internal combustion with biofuels or fossil fuels shrinks, but it never goes away completely until the population becomes big enough to worry about man-made climate change.
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    $\begingroup$ Given the tech described, I don't see a role for fossil fuels (with the massive infrastructure required to support them) or biofuels (since you need a lot of excess crops for that) but just hydrogen: you've got cheap, efficient fusion. As long as you have water, you have fuel. That said, I think that the argument that ICEs will compete with batteries falls a little flat when faced with an interstellar civilization. I'm pretty sure they'll have better battery chemistries. $\endgroup$
    – jdunlop
    Mar 14 at 19:42
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    $\begingroup$ @jdunlop, hydrogen is not as easy to store as gasoline. $\endgroup$
    – o.m.
    Mar 14 at 20:49
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    $\begingroup$ True, but much easier to make in terms of up-front investment. And you could store it as methane or ammonia. And, again, interstellar civilization. Pretty sure their materials science is also better than ours. $\endgroup$
    – jdunlop
    Mar 14 at 21:54
  • $\begingroup$ @jdunlop, that would perhaps be stage 3 in my model of colony development, not stage 2. There is something to be said for a fuel which can be poured back and forth in jerrycans, which methane cannot. $\endgroup$
    – o.m.
    Mar 15 at 5:35
  • $\begingroup$ @jdunlop Why would you bother storing it as ammonia when ammonia has lower energy density? $\endgroup$
    – DKNguyen
    Mar 16 at 5:25
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In the far future, novel means of electric power storage may outperform our current electric vehicles in terms of charging time, energy density and harvesting renewals such as solar and wind energy. Maybe fusion will save us from reliance on petroleum even if solar and wind don't catch-up with our increasing appetite for more energy.

However, in the mean time, you can implement some reasonable energy-efficient means to generate synthetic fuel.

  1. The Germans synthesized fuel during WW2. Unfortunately, this used coal as the source material. True, it uses more energy sources to generate fuel but it is not more renewable than coal mining.

  2. Biofuel Methanol. Brazil has been using sugar from sugar cane to generate Methanol. It is more efficient than growing corn for that purpose, but still needs some land allocated to the task. That hurdle is what caused the burst of the "dot-corn bubble" (compared to the "dot-com bubble") because that same land could have instead fed more people, and not fuel-guzzling cars.

  3. Methane from sweage water - That's much better - Use anaerobic sewage processors. Modify sewage processing plants to work anaerobically and generate lots of Methane which can be used as fuel. You can do the same with cow manure in farms. Rather than composting them through the thermophillic process, use the anaerobic fermentation to generate Methane.

  4. Carbon sequestation - Collect carbon dioxide from the atmosphere and make it react with water to generate Methanol. Methanol has more energy, so you need energy input in order to make an energy source. You cannot make energy from "nothing". Gladly, you can use catalysts whose process is powered by things like solar energy. This process is still in its infancy.

So in general, this is possible, but I think that in the long run transportation would rely more on electric motors rather than ICEs. Methane generation from sewage water seems to offer the best promise because it treats waste materials while at the same time generating fuel from them. Our current technology allows us to use Methane as fuel for an internal combustion engine, but in the future, it may be possible to build a fuel cell that produces electricity directly from it.

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  • $\begingroup$ The OP does specify an "interstellar civilization", so fuel synthesis is unlikely to be a problem, and they must have some pretty enormous sources of energy available. $\endgroup$
    – jdunlop
    Mar 14 at 19:00
  • $\begingroup$ @jdunlop correct, nuclear fusion is relatively cheap and efficient in this version of the future compared to anything we have today. Somewhere between the expanse and halo universes. $\endgroup$
    – BigDumb
    Mar 14 at 19:19
  • $\begingroup$ So that is to say that biofuel, gassification/liquifaction of solid fossil fuels, or even waste recover is unlikely in the extreme to be necessary. If someone needs a flammable fuel, it can be synthesized from carbon dioxide and water at a substantial energy cost. It still doesn't justify inefficient ICEs, barring very specific applications, though. $\endgroup$
    – jdunlop
    Mar 14 at 19:33
  • $\begingroup$ @jdunlop Local inefficiency is irrelevant if your energy density is massively higher than competitors. $\endgroup$
    – DKNguyen
    Mar 16 at 5:23
  • $\begingroup$ methane from waste should also be cheap which encourages its use. $\endgroup$
    – John
    Mar 16 at 15:06
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The choice between electric motors or ICE ones is a matter of logistics.

If you are only going to be hanging around places with a reliable grid, or if you're capable of generating your own juice with solar panels, electric may be the best option.

But if you have no access to a grid, and you're going to a place where there isn't much sunlight, it would be safer to have an ICE and bring along some fuel.

If you have something hybrid, you can get the best of both worlds.


Notice that it may be preferrable to burn fuel even when you have access to a grid, if the cost of electricity or the total cost of ownership of an electric device is more expensive than the cost of the respective ICE alternative. Right now, in real life, the government of Alberta is ensuring this is the case by taxing the maple out of electric vehicles, for reasons.

When it comes to energy costs, the hybrid option here allows you to have the best of both worlds wherever you go.


Finally, unless the technology of your spaceships is advanced enough to be like magic to us (besides the FTL), you can't propel a vessel in space just with electricity. Solar sails are solar snail slow, and the most usual way use to (relatively) efficiently move around in space involves burning stuff to expel it at high speeds in the opposite direction you wanna go.

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    $\begingroup$ Not strictly true: the most efficient engine that we've conceived of (that still has a substantial delta-V, otherwise I'd be pointing at ion drives) is a nuclear thermal rocket. You still have to expel a thing, but you're not burning it. $\endgroup$
    – jdunlop
    Mar 14 at 19:44
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    $\begingroup$ @jdunlop indeed. I'm fixing my remark $\endgroup$ Mar 14 at 21:56
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My short answer is: Lots of old technologies are still useful. I'm a software developer so I am not at all afraid of new technology. But I often find that the old tech is distinctly better.

I often see articles on the web with headlines like, "10 new inventions that will change your life". And often, after I read the list, I think to myself, "Not only will none of these inventions revolutionize my life, but most of them sound so useless that if you were giving them away for free, I wouldn't bother to walk across a room to pick one up."

Simple example: I used to carry around a paper appointment calendar. I would hand-write dates of meetings, etc, in it, and then each week I'd look at the appointments for that week and plan accordingly.

Then I saw an ad for an electronic appointment calendar. This seemed like a great idea! I could type in appointments rather than having sometimes hard to read hand writing, it could sort and search, make room as necessary, and many other benefits. So I bought one.

I quickly learned that it had many drawbacks. In order to be small enough to fit in my pocket, it had to have a tiny keyboard that was difficult to type on. The display was also small, about three lines of text. So while on my paper calendar I could see a week at a time, on the electronic calendar I could see part of one day at a time. And then one day the software had a glitch and all my appointments were lost. I suppose theoretically I could drop my paper calendar in a puddle and make it unreadable. But that had never happened to me. I never lost an appointment because of a software error on my paper calendar.

I went back to the paper calendar and continue to use paper to this day.

ICE has many advantages over EV today. ICE vehicles are significantly cheaper to build. They have longer range -- the energy density of gasoline is orders of magnitude greater than the energy density of a battery. EV batteries wear out over time and have to be replaced, at significant cost. Etc.

The simple proof is: Governments have to subsidize EVs to get people to buy them, or even mandate that people buy them. Left to their own, most people prefer an ICE.

Perhaps with continued R&D these problems will be overcome so that eventually EVs will be better than ICEs in every way. But that's pure speculation, bordering on wishful thinking. One might just as well say that with continued R&D, ICEs will become better than EVs in every way.

To make it work in a story, one need only pick ONE advantage of ICEs and create a situation in your story where that advantage is critical. Like, ICEs have longer range. On your remote world, it is not practical to maintain a large network of charging stations. Thus, EVs may be the primary mode of transportation back on civilized and highly-developed Earth, but they are not practical on Aldebaran IV.

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There are entire planets covered in giant lakes and seas of hydrocarbons, liquid methane, etc. or covered in hydrocarbon ice.

There are also gas giants with layers of extremely high pressure methane deep enough to lose 100 Earths in them.

Hell, there are even free floating comets and asteroid of this stuff.

basically, fuel for ICEs is abundant in the universe, and in many cases, you need to get rid of it to make the planet habitable (ex: you cannot have lakes of methane on a planet that you want to Terraform, or build a colony on a surface soaked in benzenes. You need to get rid of this stuff, and whats better way than burn it?)

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Have a series of really tiny nukes go off to generate electricity that ultimately drives the wheels. Hand-wave some reason for not operating in continuous mode, maybe that would simply generate too much energy, making the engine wasteful.

When this tech is ubiquitous, none bothers to store energy, or transmit it on power lines, the generation is at source.

Large objects, like houses, can afford good shielding that muffles the sound to nothing.

Portable objects, like motor cars can only afford bare basic shielding against radiation, but not the mechanical noise of things expanding, etc.

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  • $\begingroup$ Hi Dirk, I think you're not really addressing the question, which is asking for a comparison between types engine given the technological scenario. $\endgroup$
    – Joachim
    Mar 15 at 7:40
  • $\begingroup$ True, I'm offering a creative solution to work around the tech level issue. $\endgroup$ Mar 18 at 8:58
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So you have a colony on a new world. It might not have fossil fuels at all. The obvious path to transport is the one we followed here. Start with feet. Next step is riding animals, horses, donkeys, camels, whatever is appropriate to the local ecology. The next step after that is steam. The fuel can be practically anything that burns. If water isn't readily available, you don't have much of a colony. Steam gives you railways, trucks, cars, and in cities can power cable-cars. Internal combustion comes next, but you need the industrial base given by steam to make it. You might be able to bypass ICE for EVs, but I seriously doubt you can bypass steam. Given the level of pollution involved in making EVs, let's hope that any future civilisation that goes in for them has figured out how to make them last much much longer than ours do. Show a character preferring to inherit her grand-grandfather's car rather than get one from a fabber.

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Depends if there is scalable generation of power from other sources is available. That is relatively small scale nuclear or fusion generators. From few Megawatt to few dozen Megawatts scale.

If not internal combustion engines make lot of sense for use case like ocean ships or simple backup power generation. That is when you need to bootstrap other generation and you have run out of battery power. And even smaller generators might make sense to power some remote locations when solar or wind is not available and power for communication is needed.

Fuelling even piston engines is relatively simple too. There is wide enough range of options beyond fossil fuels. Such as biogas, alcohol, biodiesel from crops and fats or even hydrogen. That is quite wide range of options that might not require too complicated infrastructure.

Piston engines could also be relatively simple to build. Basic machining and simpler electronics or even no electronics depending on production level of colony allow local industry to be capable to build them relatively quickly. Meaning that everything does not need to be supplied from off planet.

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Let's address this massive misconception first:

So purely electric vehicles are clearly the future.

That's unlikely at best. Unless you count hydrogen fuel cells as 'purely electric' or you're talking about a very far future where portable fusion is commonplace.

Battery tech is getting better every day and EVs are gradually getting cheaper.

It's changing, but not necessarily getting better. The current round of developments are cheaper and less prone to thermal runaway, but they're also significantly heavier. EVs are already heavier than equivalent ICE-powered vehicles.

Because of the lack of infrastructure, would it be more practical to have ICE vehicles that we can synthesize fuel for?

Absolutely it would. At least until we start producing something equivalent to Mr Fusion:

Mr Fusion

You're going to have to build up a major materials extraction and processing infrastructure before you'll be able to provide the raw materials you need to build EVs for your colonists. Extraction of raw materials takes a lot of energy, and all of the current methods use ICE-powered machinery (and slave labour in some cases, but let's not talk about that) to pull stuff out of the ground and move it around. Lithium extraction and refining is a dirty process, so let's hope we've found something much cleaner in future.

It's going to be a long drag on the way up to EVs, so how are we going to fill that gap?

The same way we did it the first time: animals, steam, then ICEs.

First, ship a sustainable breeding population of horses with your colonists. Might need some food supplements to keep them healthy, but once we replace native vegetation with Earth grasses and so on that won't be a problem. Get started on breeding them early so that you'll have new riding animals within about four years.

With horses we have horse-drawn and horse-powered vehicles and equipment. A cart is easy to throw together out of pretty much any materials you have to hand and a little bit of work. Horses still pull plows today in some places, no reason you need to ship expensive and heavy tractors.

While the farmers are working on their thing, get started on mining and processing the simple stuff: iron, copper, tin, etc. Once you have a supply of reasonable quality iron you make steel and then... well, any half-decent machine shop can make you an ICE that will run on moonshine. Contrary to popular opinion, ICEs are actually quite simple. And producing biodiesels would make the ICEs even simpler. Bonus points: the carbon released came from C-negative sources, so it's technically C-neutral.

These alcohol ICEs will be around for a long while until you reach a high enough level of colonial development to be able to manufacture intricate machinery like the very precise electric motors and the processors that they require to operate. And the roads that they need to maintain their efficiency advantage.

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  • $\begingroup$ Colonization doesn't mean giving up all technology, it is a bootstrapping process, You don't drop people naked in the wilderness. fuel is worse than batteries for portability because solar panels are a thing. Fuel still need to be refined and distributed. $\endgroup$
    – John
    Mar 19 at 20:07
  • $\begingroup$ @John Travelling to another star is an expensive process. The more you have to carry the more expensive it gets. You don't ship thousands of tons of cars you send the minimum you can expect to get away with, with a little redundancy. Better to send the tools to make primitive craft, juvenile breeding stock of animals and so on. Every extra kg of cargo is costly, so you minimize as much as possible. $\endgroup$
    – Corey
    Mar 20 at 9:53
  • $\begingroup$ @John As for fuel... it's trivial to produce alcohol from pretty much any plant life if you're not concerned about taste. Or toxicity. Solar panels are fine if you have a lot of them - direct solar-powered cars don't exist for a very simple reason after all. We're talking about a few tons of solar panels per vehicle per day of operation. Or a simple brew-and-distill process to get fuel-grade alcohol using a few grams of tailored yeast, a few kg of gear and whatever compatible plant life you have to hand. And just try to stop your colonists from brewing alcohols. I dare you. $\endgroup$
    – Corey
    Mar 20 at 9:57
  • $\begingroup$ And a still if you have a month to wait to fill your gas tank. solar panels can fill it in a day, less if you have a detached power pack. And as the Russians learned the problem with using alcohol as fuel is stopping people from drinking it. and who said anything about direct solar powered cars? also the tools to make cars are also the tools to make nearly everything else you need, a horse on the other hand is really only useful for one thing. which one is saving weight again? $\endgroup$
    – John
    Mar 20 at 20:38
  • $\begingroup$ @John You're ignoring the fact that you need to ship tons of solar panels for each car to get enough of a charge to use them for the day. Or you can ship a small amount of fuel for the few alcohol-powered cars - which incidentally can be much lighter as well - to keep them running until your fuel production is online. As to people drinking the fuel... yeah, desperate, hopeless people with nothing to look forward to and nothing to do with their lives will do stupid crap. Your colonists hopefully aren't in that category. $\endgroup$
    – Corey
    Mar 20 at 22:30

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