Combined Arms on Airless Worlds

[chimericoncogene]

Assuming a plausible mid-future setting:

How exactly would North Callisto and South Callisto make war against each other?
Or Oceanus Procellarum Autonomous Region and Mare Tranquilitatus Protectorate (Luna)?
Or Tombaugh Regio Settlement and Tatarus Dorsa Colony (Pluto)?

Examples of considerations:
(The exact nature of hostilities and the weapons employed would of course depend on the available infrastructure and exact setting)
How useful are terrestrial analogs for considering warfare on airless worlds?
Would mechanized forces and armor remain useful on airless worlds? Infantry? Artillery? Ballistic missiles?
Would spacecraft in low orbits dominate?
Would hoppers (small rockets flying ballistic trajectories) be a good analog for air support?

[Patroklos]

To a certain extent weapons will resemble those used in open space. With no concerns for aerodynamics, atmospheric interference of beam/radiation weaponry, complete absence of pressure waves you just have space with a bit more geography.

Some specific differences beyond the effects of encasing all the squishy biological in pressure vessels:
1.) No restriction of vacuum frequency lasers
2.) Radiation weapons are going to be much more effective as direct radiation damage mode weapons (vice atmospheric fireball inducing mechanisms)
3.) Sensors will be far more effective without atmospheric refraction, reflection, or ducting. But note this means they are all strictly line of site.
4.) Comms are now effectively line of site too as there is no atmospheric bouncing, unless there are some curious magnetic field properties to the planetary body.
5.) While its still possible to look out of windows and helmet visors, they simple fact is all combat C4I input will probably have to be via third part electronic means. When you are bouncing around weapons grade lasers in a vacuum you can't have people using their MK1 eyeballs for anything directly. Granted, even today most high end combat involving ships/planes/tanks already rely on third party sensors for everything, combat happens at such ranges the eyeball is useless anyway. But for infantry warfare the sensors are still mostly the same as when Grog hit Brok with a mastadone bone 10K years ago. Biological eyes and ears (obviously there will be no ears either). This will no longer be the case.
5a.) So combine the insane vulnerability of eyeballs to lasers necessitate fancy third party sensor systems and the cumbersomeness of suited vacuum protected infantry (even more so in low gravity), I don't think you are going to get much MoonRackeresque space suited infantry battles. Its going to be vehicle based.

Something that will drastically impact the character of the warfare is gravity (as always). All of your examples are for very low gravity environments. The character of non-atmospheric warfare would be vastly different in low and high gravity circumstances. For very low gravity "planetary" warfare will just be regular spaceships fighting close to the body. In high gravity we may have things still recognizable as "ground forces" to a modern observer.

[chimericoncogene]

One also supposes that airless worlds might be more desert-like terrain-wise, with no foliage for cover, making armor even more dominant over infantry. But then Europa has all those crags...
It seems that artillery might have much more range and possibly superior accuracy. A modestly-sized artillery piece might have ranges of over a thousand kilometers.

[Broomstick]

4.) Comms are now effectively line of site too as there is no atmospheric bouncing, unless there are some curious magnetic field properties to the planetary body.

More like no magnetic fields (barring iron ore deposits or other local concentrations of magnetic elements, and maybe not even those). I know the Moon has no overall magnetic field (compasses are useless on the Moon), neither are other small bodies without a liquid, moving core.

5.) While its still possible to look out of windows and helmet visors, they simple fact is all combat C4I input will probably have to be via third part electronic means. When you are bouncing around weapons grade lasers in a vacuum you can't have people using their MK1 eyeballs for anything directly. Granted, even today most high end combat involving ships/planes/tanks already rely on third party sensors for everything, combat happens at such ranges the eyeball is useless anyway. But for infantry warfare the sensors are still mostly the same as when Grog hit Brok with a mastadone bone 10K years ago. Biological eyes and ears (obviously there will be no ears either). This will no longer be the case.

Well, unless you wind up in a hand-to-hand combat situation which, while unlikely in many ways, is still possible. But since all parties will have to be in pressure suits "bash with rock" techniques could still be quite effective. It's just that instead of trying to breach the enemy's skull to let out his brains you'll be trying to breach his suit to let out the air.

Would it be possible to have visors that filter out the most common/most likely laser frequencies to prevent blindness but also to allow vision without need for powered tech?

5a.) So combine the insane vulnerability of eyeballs to lasers necessitate fancy third party sensor systems and the cumbersomeness of suited vacuum protected infantry (even more so in low gravity), I don't think you are going to get much MoonRackeresque space suited infantry battles. Its going to be vehicle based.

Unless the vehicles break down.... as I said, hand-to-hand will be unlikely but still possible. With low gravity heavily armored pressure suits are a possibility, in which case the aim will be to somehow breach the enemy's suit rather than kill him with blunt force trauma.

We will definitely have vehicles - hell, the Apollo program had a "Moon buggy" which is presumably still on the surface somewhere. There will be differences in how they're powered - an internal combustion engine requires oxygen which will be in short supply on an airless surface. Either these vehicles will be carrying their own oxygen, using some sort of fuel with a built in oxidizer, running on solar, or... something. Once you solve the problem of powering them without an oxygen-rich atmosphere it's pretty straightforward after that. Well, you might need some different lubes for low/no pressure environments and a few other details, but they're details, not major concept changes.

[madd0ct0r]

I can't decide if the lack of atmospshere, and assumed lower gravity (since high grav places tend to collect atmosphere) means that artillery will be incredibly powerful, accurate and long ranged, or desperately predictable and easy to intercept by laser.

Can a laser get enough time and energy on target to negate kinetic impactors?

[LaCroix]

Without atmosphere, all ballistic unguided projectiles become extremely predictable, accurate, powerful,and long ranged.
V0 equals Vimpact at all practical ranges.
Unless you shoot at something above or below, but even in a trajectory, the gravity -induced speed loss and gain cancel each other mostly out without drag.

[Imperial528]

Direct impacts will receive a significant boost, but I wonder how this affects the traditional use of artillery.

Blast-optimized warheads will be next to useless without an atmosphere unless they're aimed at a fortified position or something underground.

I imagine you'd see more cluster-fragmentation warheads for use against infantry. The environment may well make guided kinetic penetrators more cost effective on the basis of higher kill rates.

Possibly some sort of mini-MIRV that splits out into a group of unguided penetrators above the target in order to overwhelm vehicle point defense and try to get plunging hits.

[KraytKing]

Here's something a bit interesting: if the gravity is low, but you train troops on Earth, I would imagine you add specifically weighted, unpowered armor to bring the trooper to what their weight would be in their home environment. Have separate armor designs for every planet you can be expected to fight on so your troops never leave their comfortable range.

[Elheru Aran]

Here's something a bit interesting: if the gravity is low, but you train troops on Earth, I would imagine you add specifically weighted, unpowered armor to bring the trooper to what their weight would be in their home environment. Have separate armor designs for every planet you can be expected to fight on so your troops never leave their comfortable range.

I would be more inclined to use the same design wherever possible, in order to save money. The tweak for each planet is inertial feedback; increase feedback proportionately to gravity/atmosphere. So in low gravity/no atmosphere like Luna, nearly no 'inertia', minimal feedback; on Terra, plenty of feedback (supplemented by local gravity/atmosphere).

In other words, if we are talking about powered armour here, in theory it would require minimal assistance in a low gravity environment since it's not using nearly as much of its own power to simply remain upright and move, the wearer can use more of their own strength.

Re artillery: I would expect anti-laser countermeasure rounds to become a thing. Since the trajectories are going to become -extremely- predictable in low/zero atmosphere, expect large amounts of laser countermeasures. Mobile artillery might become more important; mount a gun on a self-propelled carriage, fire from one area, move to another area and fire again to introduce variables to the trajectories. That said fixed artillery is just asking for trouble anyway, since it should be easy to home missiles or drones into the staging area.

[U.P. Cinnabar]

Also seed low orbit with ortillery platforms, and use their attitude thrusters to maneuver them to new positions.

Purely as a supplement to close air support and mobile ground artillery, of course.

[bilateralrope]

4.) Comms are now effectively line of site too as there is no atmospheric bouncing, unless there are some curious magnetic field properties to the planetary body.

Or something to relay the comms through. Satellites, drones, cellphone towers, etc

[Batman]

All of which are...line of sight

[chimericoncogene]

Flechette shells might be more effective against scattered troops and even armored vehicles while remaining somewhat less susceptible to laser defenses... unless lasers get really good at predicting which flechette hits what.

Drones are tricky. From what I can tell, autonomous UGVs ("rovers?") are harder to make than UAVs ("drones?") because air is empty, while ground clutter makes it hard for robots to navigate. There's no air on the Moon or Callisto, so all drones will have to be little spacecraft or disposable single-use projectiles.

[chimericoncogene]

Orbital ortillery platforms will have predictable orbits - as will hoppers - unless they have Unreasonably Powerful rocket engines. Hoppers might be effective as logistics platforms, but I consider them too vulnerable to long-range lasers (heck, artillery rounds are vulnerable to lasers) for use as close support or cavalry - however awesomely romantic "orbital cavalry" sounds.

[chimericoncogene]

A small combustion gas self-propelled gun (2km/s muzzle?) will be able to shoot at things a continent - or even half a planet - away, like ICBMs today. This may alter the game of artillery support somewhat... you can literally call on every artillery gun this side of the moon to shoot at the enemy about to overrun your position - and of course every enemy laser this side of the Moon can take a crack at the artillery shells...

[Patroklos]

4.) Comms are now effectively line of site too as there is no atmospheric bouncing, unless there are some curious magnetic field properties to the planetary body.

More like no magnetic fields (barring iron ore deposits or other local concentrations of magnetic elements, and maybe not even those). I know the Moon has no overall magnetic field (compasses are useless on the Moon), neither are other small bodies without a liquid, moving core.

Yes that is what I meant. There are many nifty tricks in communications to use the atmosphere to bounce or bend signals for OTH connectivity, all of which would be lost without said atmosphere. I added that caveat because as you say, the atmosphere isn't the only way to get those effects, even if those other ways are probably not going to be available or as useful in most circumstances.

5.) While its still possible to look out of windows and helmet visors, they simple fact is all combat C4I input will probably have to be via third part electronic means. When you are bouncing around weapons grade lasers in a vacuum you can't have people using their MK1 eyeballs for anything directly. Granted, even today most high end combat involving ships/planes/tanks already rely on third party sensors for everything, combat happens at such ranges the eyeball is useless anyway. But for infantry warfare the sensors are still mostly the same as when Grog hit Brok with a mastadone bone 10K years ago. Biological eyes and ears (obviously there will be no ears either). This will no longer be the case.

Well, unless you wind up in a hand-to-hand combat situation which, while unlikely in many ways, is still possible. But since all parties will have to be in pressure suits "bash with rock" techniques could still be quite effective. It's just that instead of trying to breach the enemy's skull to let out his brains you'll be trying to breach his suit to let out the air.

What I was getting at is that your space troopers will have to be looking at an artificial representation of their surroundings. This can be as simple as a straight visual feed a suite of optical cameras feeding a display inside an enclosed helmet (or a direct neural tap as is sometimes popular in scifi), or some thing more fancy like a recreated artifical representation via lidar, radar, etc. Or a combination of both overlayed with each other.

What this means is a greater dependency on technology, and a more expensive infantryman. Some would say that the sensory benefits of such optics would necessitate their use anyway, and they are probably right. But I wanted to make clear that what we often see in movies, characters fighting in space or future environments looking out transparent canopies with MK1 eyeballs, is probably highly unlikely. Not just because they will need better sensory instuments to be effective than the eyeball, but because the eyeball will be ridiculously vulnerable (far more so than in current combat). We will probably see fully encased helmets spider eyed with cameras, and pebbled with miniature transmitter/receiver panels. Basically Iron Man.

As a bit or relevant trivia, there are international treaties against using lasers as blinding weapons in combat. So we are actually already at this juncture, its just that lasers are still uncommon enough that its not considered a particularly hobilling restriction to impose on combatants.

Would it be possible to have visors that filter out the most common/most likely laser frequencies to prevent blindness but also to allow vision without need for powered tech?

To a certain degree, yes. But by the time we are conducting ground invasions of Callisto, I would think laser technology would be such that defeating any non opaque casual visor coating would be trivial. The energies will just be too high.

5a.) So combine the insane vulnerability of eyeballs to lasers necessitate fancy third party sensor systems and the cumbersomeness of suited vacuum protected infantry (even more so in low gravity), I don't think you are going to get much MoonRackeresque space suited infantry battles. Its going to be vehicle based.

Unless the vehicles break down.... as I said, hand-to-hand will be unlikely but still possible.

Yes, there is always some niche circumstances where some dude will encounter some dude in sup optimal hand to hand circumstances, be we don't design our warfighting around these. Hand to had combat is barely a thing now, and while bayonets and martial arts are still a thing in armies they are a vanishingly small portion of the overall training regimen. We don't train to it because we don't expect it to happen at relevant frequencies, and those expectations have proven overwhelmingly correct.

So unless someone has a reason for the trend against hand to hand combat over the last few centuries since the firearm to reverse, I see no problem assuming it to be at least as uncommon as it is now.

With low gravity heavily armored pressure suits are a possibility, in which case the aim will be to somehow breach the enemy's suit rather than kill him with blunt force trauma.

"Low gravity heavily armored pressure suits" sounds suspiciously like vehicles. Once you stop relying on the muscle power for locomotion, I am hesitant to not call whatever you are encased in a vehicle. I can't think of a good reason to have a non powersuitesque combat pressure vessels at the tech levesl we are likely to see these scenarios take place at.

[SpottedKitty]

"Low gravity heavily armored pressure suits" sounds suspiciously like vehicles. Once you stop relying on the muscle power for locomotion, I am hesitant to not call whatever you are encased in a vehicle. I can't think of a good reason to have a non powersuitesque combat pressure vessels at the tech levesl we are likely to see these scenarios take place at.

Agreed — I'm visualising something like the one-man deep sea suits that don't actually have legs, just thrusters like an ROV. And IIRC some early SF stories by Arthur C Clarke and Patrick Moore (yes, the astronomer, and yes, he did write SF way back when) included this kind of suit for orbital construction work.

[madd0ct0r]

artillery firing patterns - much like we use chaff at the moment, the leading shells in a bombardment may be designed to explode into 'smoke' clouds to try and make it more difficult for lasers to incept the following rounds.

Said smoke needs to be cheap, stable as an incredibly fine powder, light, and capable of absorbing a lot of energy by providing lots of atomic bonds that will need energy to snap. Answers on a postcard.


Thermal imaging would be incredibly powerful. No way to shed heat easily. So cover then becomes important. Mass as armour. Do we see a return to trench warfare, just with tank size trenches? Sand drift deserts with near surface moles as the best areas to hold.

[LaCroix]

Said smoke needs to be cheap, stable as an incredibly fine powder, light, and capable of absorbing a lot of energy by providing lots of atomic bonds that will need energy to snap. Answers on a postcard.

Aluminium powder comes to mind. Light, can take a lot of energy before it vaporizes away, and is blocking visual, laser and even radar/microwave sensors to a degree.

Mix it with some iron dust, and you will have occasional burst of thermite ignition when lasers hit it, so it might affect thermal sensors even more by giving false positives for missile flare.

[madd0ct0r]

I didn't think this through. Smoke stays aloft from brownian motion in the air. On the airless planet, it would fall at the rate of g.
Any gassing effect from laser hitting it would create pressure bubble to instantly dissapate, blowing the nearby falling dust away. Fire a laser on a pulse and it'd cut straight through it. Idea retracted.

[chimericoncogene]

Heat dissipation can be partially achieved by putting radiators on tracks... i.e. using the dirt as a heat sink. A system to collect subsurface dirt and pump it into chambers for cooling may be possible (in shaded areas, or in areas where the subsurface dirt is cool enough for it).

[chimericoncogene]

Dirt might also be a good source of protection. Could projectors throw enough powdery dirt into the air (on ballistic trajectories, of course) for protection from lasers and projectiles? (Unlikely, current tanks do not do so even though it might disrupt projectiles)

[Elheru Aran]

Heat dissipation can be partially achieved by putting radiators on tracks... i.e. using the dirt as a heat sink. A system to collect subsurface dirt and pump it into chambers for cooling may be possible (in shaded areas, or in areas where the subsurface dirt is cool enough for it).

Sounds overly complicated. As for the throwing-dirt-in-the-air idea... it suffers from the same problem as smoke; no atmosphere to hold up the dirt, it'll all fall at the rate of local gravity. Perhaps as an emergency expedient, but I doubt it would be very useful as a general thing.

Better, I think, to simply accept that heat dissipation is going to be compromised under combat conditions, and design your engines and vehicles accordingly. Perhaps use backup liquid coolant systems, make use of shade, and so forth. Tunnel networks could be of use, though they would add to the cost of settlements in vacuum. Of course, some sort of underground tunnels are probably inevitable in environments such as Luna, as they would be among the safest ways of building habitats.

Now I'm picturing 40K-style mole-mortars and breaching drills...

[Imperial528]

For heat dissipation I've had the idea of coolant-pipe drag lines trailed under vehicles to conduct heat into the ground; though that was to adapt vehicles which would need such extra heat disposal just to operate i.e. ones powered by nuclear reactors or large RTGs. I imagine vehicles meant for what is essentially Lunar combat would have plenty of radiator area built into them from the start if it was necessary.

[Sea Skimmer]

artillery firing patterns - much like we use chaff at the moment, the leading shells in a bombardment may be designed to explode into 'smoke' clouds to try and make it more difficult for lasers to incept the following rounds.

Said smoke needs to be cheap, stable as an incredibly fine powder, light, and capable of absorbing a lot of energy by providing lots of atomic bonds that will need energy to snap. Answers on a postcard.

The problem with this idea and no air is that anything you disperse won't stay in a cloud, it will all fly away on ballistic arcs meaning very rapid dissipation. Also anti artillery lasers could be at all kinds of angles relative to the path of the shells. I think for unit of mass fired you'd get further just armoring the shells with heat resistant coatings.

But also remember with no air nothing stops you from firing even very lightweight shells at very high velocity and low angles, greatly reducing exposure to enemy fire. And weapon ranges in general will all skyrocket, IIRC a 155mm shell that goes 30km in the earth atmosphere would go 70km without drag. So you'd probably have some direct support artillery that looks more like tank guns and can do stuff that wouldn't work out on earth, while the long range artillery can incredibly mass firepower. Something like a 120mm sabot at 1,600m/s would go over 100km easily. You'd need guidance to hit anything, but whatever it's an option.

And while lasers work better, any kind of missile is a lot more expensive to implement since it has to use reaction jet controls rather then simpler cheaper steering fins.

Thermal imaging would be incredibly powerful. No way to shed heat easily. So cover then becomes important. Mass as armour. Do we see a return to trench warfare, just with tank size trenches? Sand drift deserts with near surface moles as the best areas to hold.

Thermal imaging would be much more effective, but then by the same card it will also be much easier to locate enemy optical systems, and blind them with lasers because air isn't masking them either.