Design considerations for living inside of a tank/apc in extended combat and travel operations

Question

In my setting armies are extremely mobile for a multitude of reasons. Pure static defensive lines are just asking to be completely destroyed by smart and devastating weapons, the light particle shielding in the setting is not enough to allow a static target to take repeated fire. The planet's surface is constantly changing, and the local wildlife isn't always friendly. Some are more than capable of ripping through fortifications or destroying a static encampment with relative ease. There are few safe zones, and resources in those areas are already depleted. Resources are scavenged for and processed across the planet. Nearly all the land can be traversed by a vehicle however, some areas are tougher. But it's not going to be mountainous, swampy or environmentally hostile where too routes are commonly blocked off.

Armies in this world operate heavily on the idea of high-low. They are extremely mobile across various terrains with a combination of light and heavy armor along with an attached logistical element. When an advance force scouts out some resources it usually leaves a contingent force to both process and defend the area with resources that just popped up. Usually infantry. The rest of the force is running defensive screens and defending or counterattacking against enemy pushes. Because no one is interested in blowing up the few precious resources that popped up, fighting in the resource areas are more surgical and precise. But the areas surrounding it are a completely different story.

Most APCs like the MRAP or IFVs like the M2/3 Bradley aren't designed to actually let embarked soldiers sleep and live in their vehicles. In my case infantry soldiers need to be able to live and disembark from their vehicles. For tanks, they just need to be able to live. Ignoring fuel, obviously there is a size limit for both a practical and logical consideration. Too big and you're going to be sinking into the ground or suffer in mobility. You're also a large target. Too small and you can't transport many people or sustain combat effectively.

From what I've seen so far, I'm not entirely sure if current designs are suitable for long term use. From both a physical and psychological perspective. MRAPs, LAV25s, and Strikers seem to offer the best designs from reality. But add in some troops, basic gear, backpacks, weapons, personnel affects, and things get crowded and sweaty very fast. Plus, extended sleep is a nightmare especially for anyone in the back.

In this setting simply flying people isn't an option. Expeditions can take days or weeks, so task forces usually travel as a caravan and drive for long distances over long periods of times. There is advanced computing and navigation, but drones work only works in relatively close proximity to the emitter. Long distance drone or even radio control/communications isn't a guarantee.

What would an NBC capable armored personnel carrier or tank look like if it were required to take into extra-long deployment living conditions? What would be the most important features?

These vehicles wouldn't need to carry everything, logistical trucks carry extra food, ammo, water, medicine etc. But ideally soldiers shouldn't have to be going over to the next truck over to grab a water bottle or an MRE all the time. You can completely ignore generator/fuel source for this question. Sleeping and living doesn't have to be a luxury, its fine if people have a cramped bunk or even have to share a bunk. A closed cabin approach is a MUST. The air isn't always healthy enough to breath in without filtering. Sometimes its fatal within seconds to minutes, though harmless through an air filter.

Answer 1

Combat sustainability

People cannot operate continuously at peak, or even acceptable efficiency without high quality rest. For sustained, continuous operations over several days to a week, there need to be at least 2 and preferably 3 shifts so that people get sufficient sleep and rest. Let's assume that there is a tank with a fully reliable autoloaded that requires a driver, gunner and commander to operate efficiently, then for continuous operations 24 hours per day then it needs a crew of 6 or preferably 9, with the facilities available in a typical RV - bunks, kitchenette, toilet, basin and a really good internal air conditioning / recycling setup to handle the funk that will build up in a vehicle that is sealed up all the time. The crew model you need to think of is more akin to a small naval vessel than a real-world armoured vehicle.

As far as weight goes - this is mostly empty space and maybe a ton of people, furniture and consumables, which is trivial when looking at a tank that will weigh many tens of tons already. The big impact on the vehicle design is that it is much bigger, making it a bigger target and either heavier due to the extra armour or less heavily armoured.

This is basically a standard Traveller TTRPG ATV/AFV with the optional weapons fitted. It will fare very badly against a dedicated MBT which is a more compact, dedicated weapons platform, depending on the relative importance of active defences vs physical armour. So what are some other options?

• Build normal tanks without the extended accommodations and operate them like fighters from a modern aircraft carrier. Every 8-12 hours, rotate the tanks back to the big "crew sustainability" RVs protected in the middle of the formation and put a new crew in. Each tank will still need a toilet and some comfortable reclining seats along with the food and water that would be carried anyway, but removing the need to sleep comfortably means there is a relatively minor negative impact on the tank's size.
• Operate the tanks as drones, keeping all the crews back in RVs that are protected in the middle of the formation. This is the most sustainable solution, but is vulnerable if the enemy can somehow target the RVs or jam the communication links. (However, if the enemy can break through and target your logistics element then you have probably lost anyway.) One advantage of this policy is that if a tank is badly damaged then there is no rush to recover the crew, which is one of the many advantages of using drones as front line combat vehicles in any situation.
• Use manned AFVs but make them slightly smaller by allowing crews that are resting/sleeping to slave their vehicle's weapons to another vehicle in their platoon/troop, as happens in some of the Hammers Slammers stories. This means that each AFV only needs accommodations for 3 and can still operate to some extent continuously.

APC problem - If operating an APC for a prolonged period in a toxic environment then it is going to be big. Not only will it need accommodations for an entire infantry squad, but it needs an airlock big enough to fit the entire squad into. If they just "drop the ramp" as on a M113 then the entire atmosphere will need to be scrubbed before anyone can undertake actions without a sealed suit on. If they use an airlock that can only take one or two armed and armoured infantry then they are likely to be picked off one or two at a time - infantry must be able to debus as a group quickly. This means that the airlock alone will need to be as large as the entire rear crew compartment on a M113, which will make the carrier as a whole enormous and therefore a BFT (big fat target). It would be far preferable to keep the "crew sustainability" RV and the "battlefield delivery" APC as separate vehicles if possible.

Maintenance - Armoured vehicles are maintenance gluttons. Even without battle damage they throw tracks or break down in other ways more often than most people appreciate, even in ideal terrain. The terrain described in the question is far from ideal. If the tanks and APCs are going to be RVs with masses of extra armour then they will require similarly outsized recovery vehicles, massive mobile workshops to let people work on them in a shirtsleeves environment etc etc...

The importance of rest - Back in the early cold war days, the United States experimented with the idea of having some fighter pilots sleep in their aircraft so that if nuclear-armed Soviet bombers were picked up then the pilots could be woken up and take off immediately to intercept. The accident rate in training and readiness drills among pilots who had just been woken up and told to take off was horrendous. This led to some of the first rigorous military research on how long it takes after waking up before a person can operate at full mental efficiency. Do not underestimate the impact on effectiveness of lack of sleep or insufficient time to wake up when planning sustainable operations.

Answer 2

Don't bother. IFVs don't have enough range away from their base to make it worthwhile. Even much lighter, lower-consuming civilian vehicles rarely have that much longevity.

You say that

Expeditions can take days or weeks, so task forces usually travel as a caravan and drive for long distances over long periods of times.

Fuel, food, ammo, and other consumables for a "caravan" of IFVs and their attendant troops comes to a massive load. You will need transports to carry that load, and the services (such as medical care and maintenance) that would normally be offered by your base of operations. Otherwise you can't use anything like modern IFVs; they aren't designed around the premise of complete isolation from support and supply.

The main bulk of your caravan is a slow-moving train of big cargo haulers with mobile forces of tanks and IFVs that range out from it to a) attack and b) keep raiders away from the vulnerable cargo vehicles. It will also need to stop periodically, unless you want to be performing surgery or machining spare parts in the back of a moving truck (which you don't).

So the answer to "where do your soldiers eat, sleep, and live" is simple: with the caravan. Your caravan spends eight hours a day moving and sixteen hours operating as a mobile field base (setting up temporary defenses and work spaces, fixing things, mending people, distributing supplies, receiving communications, etc.). During that time you have ample opportunity for people to sleep in the field base, either in tents or in/on the trucks.

Don't worry about the air filter. If you can build an air filter into a vehicle, you can build it into a tent. And if something goes wrong, it's far easier to get your spare tent out of storage than it is to fix your IFV in the middle of the night.

Answer 3

• Volume under armor is more expensive than volume in soft-skinned vehicles.
  When a seat is put behind the turret or glacis armor of a MBT, that requires a larger armor plate, which requires larger engines and tracks, which again raises weight, etc.
  So there might be a class of "armored logistics/support vehicles" rather than armored fighting vehicles. They are designed as a survivable transport of various services, but not to fight. That should make them cheaper per ton of payload than an AFV.
• Tracks or wheels?
  As far as useful volume goes, a tracked vehicle is not necessarily worse than a wheeled vehicle. Compare the troop compartment of the M113 and the Stryker. MRAPs have better troop compartments, but they are not exactly fighting vehicles. They're for counter-insurgency.
  Wheels have the advantage in mobility and maintenance requirements on roads and good off-roads terrain. Tracks chew up roads, and they need to be replaced every thousand kilometers or so. But they are better in bad off-roads terrain.
• Living in moving vehicles, or living in halted vehicles?
  It will be considerably more difficult to have bunks, kitchens, toilets, and all that in a bouncing, tilting vehicle. Much easier to design if it works when the vehicle is halted, and possibly leveled on jacks. So reconsider if you really need people to rest in moving vehicles.
  A halted vehicle could be designed as expando-van or with attached tents for greater volume. That requires sentries who to provide warning time to move the camp.
• How much NBC threat?
  Decontaminating troops takes time, effort, and supplies (lots and lots of hot water, among other things). So if the NBC threat is high, there would be an incentive to spend a long time in one vehicle. Sleeping, washing, cooking in one vehicle, and switching from that to the combat vehicle for a long period of fighting (and sleeping in seats, and peeing in cans). If the threat is low, there can be daily visits to the shower truck.

So one option would be to have the unit trains a little more mobile than today. Big trucks, a bit like the HEMTT, with living containers. And fighting vehicles with little more endurance than today.

Another option has the same housing trucks, plus fighting vehicles with at least a few bunks, and the ability to cook hot meals, and for crews to relieve themselves.

Answer 4

This is a Frame Challenge

The worst choice you can possibly make is to have your soldiers live in (e.g.) a tank.

1. Every cubic inch of volume dedicated to living space is another cubic inch to protect and another cubic inch to shoot at.

2. Your logistics requirements go through the roof. Additional fuel to move all that extra volume around along with food, water, medical, reading material, cleaning supplies, air conditioning¹... and all the other logistical problems with a Recreational Vehicle live-in-able tank.

3. The bigger something is, the harder it is to move and more expensive it is to build. I give you the Ratte, a Nazi megatank that never made it off the drawing board:

The large size and weight would have rendered the tank unable to cross bridges at the risk of collapsing them, and travelling on roads would soon destroy them. Though its top intended speed was 40 kilometres per hour (25 mph), its huge size and high visibility would have made it extremely vulnerable to aerial bombardment and artillery fire. Its great size would also have meant that once built the vehicle's strategic, operational, and tactical mobility would be entirely dependent on its own drivetrain, for there were no other realistic means of moving it from one firing position to another. No existing railway or train car could bear its weight and its width was too great for existing tunnels.

Logistics are as important as ever other consideration when designing military vehicles

It's easy to say, "there are reasons why no one does this." It's a bit more complex to explain it. Nothing today is stopping the world's militaries from building (e.g.) tanks that can house crews for long periods of time. After all, we do it with submarines, why not tanks?

Well, look at the size of those submarines.

The idea of nuclear-pile-powered mega tanks isn't at all new. Consider Keith Laumer's Bolo Universe.² In fact, you might want do do a bunch of reading in Laumer's universe as he makes a point. It would make a lot of sense for a military to relegate people to support positions (they're easy to damage and take too much time to replace) and use drones (bolos) for primary front-line attack. In other words, what you're asking for doesn't actually make a lot of sense since any really hard bang against the side of the (e.g.) tank will knock everyone inside senseless or simply kill them all.³

What would you need?

• Sleeping quarters
• Staging area
• Eating prep/area
• Waste/shower facilities
• Recreation/exercise
• Food/Water/and-a-lot-of-other-supplies storage
• medical (supplies & area)
• Clothing storage (unless you expect them to do everything in full battle gear)

And that's just off the top of my head. That's a lot of non-combat volume to be hauling around in what amounts to a portable staging area. Why not simply use staging areas? You know, tents and stuff.

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_{¹  Cooling and heating isn't something that can be ignored. I might be wrong, but if I recall correctly, the energy needed to adjust the temperature of a volume of space increased by the square of the volume of space. Every cubic inch needed to do something that isn't strictly necessary comes with a fairly high cost. Not that humans haven't been perfectly willing to pay that cost. But that's another issue.}

_{²  What was I just saying about the Ratte? Look, if you want to do this, do this! Obviously super-big super-it-doesn't-make sense constructions have been used in SciFi before. But if you want to realistically know what you need inside a vehicle used in this manner, go look at the inside of a submarine. I'd consider that your bare minimum. Oh, and suspension. You're gonna need a LOT of suspension. Lots and lots of easily broken suspension.}

_{³  I recognize that tank design attempts to minimize this particular problem. But in reality, all it can do is make the requirement for that big bang bigger. In other words, there's always a big enough shell to knock everyone inside senseless or kill them. Or, if there isn't, the line gets drawn at ripping off the turret and killing everyone inside. My point is that tanks aren't like submarines. They're a lot easier to shoot at than submarines. And every second someone not-part-of-the-necessary-crew is inside is a second where that expensive-to-train-and-equip-and-replace person gets killed.}

Answer 5

Winnebago warriors!

Motorhomes are really comfy for long trips. Yours has guns. There are hammocks hung on springs for when people are sleeping during bumpy rides. Those bumps rock them right to sleep. I invented those spring hammocks just for this concept! There are pulldown shields for the windows in case things get extra gnarly. There is a sweet sound system too, and video games.

Answer 6

Very basic needs are

ITEM	DURATION
Breathable air	Continuous supply
Food	After 12 hours
Water	After 5 hours
Pee	After 5 hours
Stool	After 24 hours
Sleep	7 hours long

People sleep in trucks, vans. A 5' x 3' inflatable camping mattress can be used for sleeping. A small fan in a hole can exchange air. You can keep a lunch box for food and water. There can be hole for pee. You need to stop after 24 hours for stool and refill the lunch box.