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Excluding teleportation, the most rapid way of delivering troops to an operation planeside is by dropping them out of orbit in a steel can. Whether a small QRF or a few thousand marines dropping in to suppress air defenses and establish a foothold, drop pods are a staple of scifi stories. However something they can never seem to agree on is how many people these pods should carry. What are the potential benefits and drawbacks of choosing a larger 2-5 person pod over a small single person pod and vice versa?

In-universe considerations

I'm not going for a particularly hard science fiction approach so some degree of handwavium is acceptable when it comes to technology. Example: An artificial gravity well can be created that will make passengers in a vehicle more resistant to high G shocks, but, you still need to worry about the vehicle itself staying together.

Electronic warfare has advanced to a point where highly complex electronics are of limited use in a conventional war this can effect the following:

  • Robotic soldiers exist but have only basic problem solving capabilities, organics (real people) must also be on the field to direct their mechanical comrades.
  • AI targeting systems are very accurate but easy to fool, most guided gun and missile systems must have an organic gunner, not necessarily to aim and fire, but to make corrections where needed. Expect late WWII level hit probability on particularly fast moving objects
  • Wireless communication can be easily jammed, the EM spectrum of a battlefield is ridiculously noisy, whoever has the stronger signal wins in the broadcasting theatre of a battle.

QRF: Quick Reaction Force

Please let me know if you need any further elaboration or clarification!

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  • $\begingroup$ What is a QRF? {padding to make comment engine happy} $\endgroup$
    – JBH
    Commented Jan 31, 2022 at 19:39
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    $\begingroup$ @Join JBH on Codidact QRF: Quick Reaciton Force, thanks for looking out for me. $\endgroup$
    – Boo Radley
    Commented Jan 31, 2022 at 19:48

9 Answers 9

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I'd say the biggest driver of drop pod strategies would be the kind of resistance you expect. Ideally you'd have one drop pod (or drop ship, potentially) per objective, and you'd load each one up with enough personnel and equipment to achieve their goal.

Problem is though, if the objective is defended in any way then there's a risk that a particular drop pod could be destroyed before it landed, with all the resulting loss of life and material that entails. Intercepting hypersonic re-entry vehicles isn't trivial, but remember the existence of things like Sprint and Spartan that demonstrated the ability to intercept ballistic re-entry vehicles using nuclear warheads that allowed for pretty big margins of error. Those two projects used 1970s missile and radar technology, and by the time you're considering mass troop drops from space you might reasonably expect to have improved both of those things somewhat.

By using multiple smaller re-entry vehicles, together with what Cold War military strategists referred to as Penetration Aids (no giggling at the back) the chances of wiping out an entire task force is vastly reduced. The penalty is that now you need to spread your drop pods over a much wider area (if they were too close to each other, then a big nuke could either destroy them or kill their meaty centers) which makes the contents of each pod much more vulnerable to what it might meet on the ground, compared to the single big drop that's the alternative when there's no risk of hostile aerospace defence.

The lower size limit would be set by how widely you were willing to spread out your troops, and how much you were willing to risk individual soldiers (or very small groups) whilst they tried to link up with the rest of the force in potentially hostile and unfamiliar terrain.

It is also worth considering that the drop pod following the classic blunt-body re-entry vehicle design is great for use in a non-hostile theatre, but what you probably want for combat drops might reasonably look a lot more like a hypersonic glide vehicle optimised for unpowered but manoeuvring flight that retains high speeds at lower altitudes, making it somewhat harder to intercept (at least, by modern-day standards). That means it'll probably end up looking more like this:

Artist impression of Raytheon's hypersonic boost glide vehicle (Artist rendering of Raytheon's Tactical Boost Glide flight system. Image credit: Raytheon)

than something pod-like.

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    $\begingroup$ With regard to dispersion, the maneuverability your individual infantry person would be the driving factor here. If we look at Robert Heinlein's Starship Troopers, the Marauder suits were capable of covering several kilometers in a single jump and deployed in individual pods. By contrast Warhammer 40K Space Marines are limited to "normal" infantry speeds. They use 5-person pods in tighter formations because they are expected to disembark as fireteams and quickly form up as demi-companies to take objectives. $\endgroup$ Commented Feb 2, 2022 at 16:23
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    $\begingroup$ @VinnieFusca yeah, Heinlein was a big fan of omnicapable individuals. Plausibility of his infantry aside, there's much to be said for operating in groups or at least pairs, whenever possible. $\endgroup$ Commented Feb 2, 2022 at 16:54
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It is a tradeoff

One big drop ship is cheaper than many small ones. Big pods have a higher volume to surface area, plus there are certain components you need 1 and only 1 of regardless of pod size like navigation computers, landing cameras, etc. Also, one big component is often cheaper to mass produce than lots of little ones; so, making 1 big landing thruster is cheaper than 5 little ones even if both sets produce about the same total thrust. So, it is cheaper to drop a given number of troops in the bigger pods.

That said, ever heard the saying "don't put all your eggs in 1 basket"? If you have to drop 5000 men into hostile territory, and the enemy has the capacity to hit 1000 of your pods on the way down with AA weapons, then deploying in smaller pods means 80% of your ground forces will survive the decent, but if you send fewer larger pods, you risk your whole invasion force being wiped out.

This makes the question of drop pod size directly proportional to how much your civilization values an individual life. If your civilization sees human life as cheap and expendable, then bigger pods make more sense. If your civilization places a higher value on human life, then smaller ones make more sense. That said, there are also situational factors to consider. If you are trying to deploy a lot of assets into a fully secured LZ, then drop "pods" may not be the way to go at all. A single large transport ship can store a lot more troops, supplies, and hardware if it's not wasting a ton of capacity on drop pods at all; so, your initial "beach head" invasion will probably be done with a swarm of these small pods, but once you have secured a place to land, you would want to bring in full sized landing ships full of not just troops, but tanks, artillery, AA batteries, etc.

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  • $\begingroup$ +1 as it's basically what I'm thinking. However, I think onpy the movies do the 'only one kind of x' thing. If they do not value life and equipment as much they can still use small drop pods if it can give them an advantage. Any military would use what is appropriate, though their doctrine will steer in certain ways more often. $\endgroup$
    – Trioxidane
    Commented Jan 31, 2022 at 19:42
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For a given shape, the surface to volume ratio increases with the decrease of the size.

Aerobraking is affected by the cross section of the object, while the amount of energy that is has to shed is affected by the volume.

Therefore, for a given shape, the smaller it is the more easily it can aerobrake. If you apply this reasoning to the descent pods, a single passenger pod seems to be more efficient than a multi-passengers pod.

Then you need to make a trade off with the availability of materials: here the advantage goes in the other direction, with bigger being better.

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  • $\begingroup$ So smaller drop pods are more efficient when it comes to slowing themselves down, what about the re-usability of these pods? Would it make sense to collect together thousands of pods from a landing zone after the front has moved on? $\endgroup$
    – Boo Radley
    Commented Jan 31, 2022 at 18:28
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    $\begingroup$ @BradleyKnauer What if instead of collecting them for another drop you actually use them as fence posts? Build structures out of them. Open the can in the middle so it looks like a UU and make a fence like this UUUUUUUUUUUUUUU. $\endgroup$
    – mcbecker
    Commented Jan 31, 2022 at 19:15
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    $\begingroup$ @BradleyKnauer, given your intent to reuse the contents of the pod it's reasonable for the pod itself to be sacrificial to protect said squishy contents. Think car crumple zones. All you're getting from used pods is scrap metal. $\endgroup$
    – Separatrix
    Commented Feb 1, 2022 at 14:04
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    $\begingroup$ The cross section vs volume argument only works if the shape stays the same density, which isn't likely for a drop pod. A larger drop pod would likely be a lot less dense since a higher proportion of it would be full of air. That argument also assumes that the pod stays the same shape, which also isn't likely. If you make a pod for 4 people instead of 1 you don't need to make it any taller, you only really have to make it wider, which increases braking cross section much more than it does weight $\endgroup$
    – Kevin
    Commented Feb 1, 2022 at 23:20
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4 person team pods.

The problem with orbital drops is inaccuracy. Your soldiers might be scattered over a large area. It is bad for morale to be a single soldier all alone. A team of 4 persons can support each other and is big enough to get things done.

And 0 person pods.

rupert the paradummy

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

Here is Rupert the paradummy. Fake paratroopers are good for soaking up bullets. So too empty pods. A lot of your pods will be empty, or might be full of propaganda. They are to divert attention from the pods with people in them on the way down.

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  • $\begingroup$ Wouldnt it be smart to make the pods have a low stealth signature to decrease its radar cross section, so you can then scatter smaller decoys with a similar signature which are less expensive than throwing empty real drop-pods? $\endgroup$
    – Demigan
    Commented Feb 1, 2022 at 9:20
  • $\begingroup$ One can combine this and this answer instead of empty drop pods. $\endgroup$
    – Nuclear241
    Commented Feb 1, 2022 at 16:46
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It's complicated

First off there is a good chance steel will be used much less frequent. Polymers (like plastic) will have advanced in a great way, allowing for better drop pods.

The reason drop pods are different in size is because each has merrit for a certain kind of attack.

Individual ones allow for a greater spread to capture tactical positions, but are more difficult to put into small clusters. They can be no more than a suit, possibly discarded the moment they touch the ground. This allows freedom of movement and near instant deployment. They can evade fire and detection more easily because of the small cross section and higher manoeuvrability. The scatter can also be a detriment, as well as having no cover. In addition, you need a lot of materials if you cover every single troop in the pod, as well as fill it with technology, fuel and whatever. A single hit is more dangerous to the person, but less to the group.

A multi transport offers cover when arriving. The troops are also concentrated, allowing for better ground control. The transports themselves can still be scattered, allowing for capturing of strategic positions. The technology and materials to support them are less. Each transport can have a team that is build to support each other. Like light and heavy assault, support, medic, etc. They are easier to spot and shoot down. A hit is less severe on a multi transport, but destruction of the transport offers a higher loss of military power. They can often be reused, salvaged or used to bring manpower back into the air/space.

Personally I would have mix. A few single person drop pods to come down in strategic locations, clearing out or tying up the enemy troops. Then multi troop transports come down. I would go for trio transports, each facing a different direction. This will give them a bit of cover as well as 360° firepower each side if they drop right in the middle. These should create a true beach head, allowing the 20, 50 or even bigger transports to land in relative safety. These can bring the heavier equipment, generators and other matetials. At any point you can still drop down the smaller transports where required.

The initial wave of one man and 3 man drops are often sacrificial. Though well trained troops their loss is accepted. But a few of these can drop elite soldiers tasked with important missions, allowing them to drop in less detected and less chance to lose them all if a transport blows up.

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Empty of Flesh

(Full of tungsten)

If you are in a position where you are

  • involved in a war
  • against a planet-bound force
  • the orbitals of which you occupy
  • with n millions of kilograms of matter
  • that you can selectively de-orbit

You have already won. You have the ability to selectively devastate any enemy fortifications, cities, industrial areas, airfields, and spaceports.

Dropping soldiers and equipment is a waste of time. Why drop a 54,000kg tank and its crew when you could just drop 54,000kg of mass moving at orbital velocity on whatever you were planning to have the tank attack?

Once you've leveled any meaningful resistance, you can deliver troops to the surface at your leisure, if you still have any reason to do so.

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    $\begingroup$ But what if they have pretty stuff, and you want that stuff to be your stuff? What if they have hardworking admirable people and you want those people to be your people? Those things require delicacy. $\endgroup$
    – Willk
    Commented Feb 1, 2022 at 2:22
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    $\begingroup$ @Willk In case one, their pretty stuff gets much less messed up than if you were delivering forces to the ground and starting a fight there. Orbital bombardment enables greater precision than the chaos of a battlefield. As for the second, please let me know which recent case of 'boots on the ground' won any hearts and minds. You'll have much better results from a peaceful surrender after you kneecap warfighting capability. Invaders inspire partisans, guerrillas, and insurrections. The instant ability to deliver death from orbit inspires humbly downcast eyes and compliance. $\endgroup$
    – Daniel B
    Commented Feb 1, 2022 at 2:55
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    $\begingroup$ The point of war isn't just to kill people, its to achieve a goal. & killing everything indiscriminately is most likely counterproductive to the goal. $\endgroup$
    – OT-64 SKOT
    Commented Feb 1, 2022 at 5:37
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    $\begingroup$ There are plenty of situation where you can't just nuke from orbit but need boots on the ground. Hostage extraction. Assassination of high-value targets while being certain they didn't get away. Capturing a facility intact. Acquiring fragile resources. Securing intel. Taking prisoners. $\endgroup$
    – Philipp
    Commented Feb 1, 2022 at 11:13
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    $\begingroup$ @Philipp Drop pods aren't much help for a hostage extraction, given that it leaves your troops stranded with no way out on a hostile planet. For assassination, I trust a telephone pole sized chunk of tungsten to reliably kill a target much more than I trust a couple soldiers in an unfamiliar environment. Capturing a facility intact is much easier if you first isolate it with orbital strikes. I'm not saying dropping Rods from God solves every problem, I'm just saying it solves the armed resistance problem, at which point you can deliver soldiers to their LZ at your leisure. $\endgroup$
    – Daniel B
    Commented Feb 1, 2022 at 11:30
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Drop pods have a specific purpose. They arent as versatile as dropships so you have to emphasise their advantages to use them.

Mainly: cheap and hard to hit by using smaller sizes.

Drop pods would be for the initial engagement. You want to be able to clear a space and start landing larger equipment as soon as possible, like vehicles and the supplies your soldiers are dependant on. This means that drop-pods arent just for firing straight into combat, a more likely attack method would be to shoot them a few kilometers away from their target where they have a higher chance of landing safely and then assaulting their objectives so dropships can land and disgorge the real assault.

This means that the size of the drop-pod is dependend on where it is supposed to land, and the effectiveness of the anti-air defenses in question.

The closer to any defenses capable of shooting a drop-pod out of the sky, the smaller the drop-pod is to increase its chances of survival. The farther away the larger the drop-pod can be and land safely. Larger drop-pods also means more volume inside for supplies and heavy weapons, assuming some of the drop-pods dont deploy into small artillery pieces and towable guns.

So its essentially up to you. Want to drop the pods on top of the AA defenses? Small Drop-pods are the way to go. Want to do a more intelligent drop? Bigger one's a ways away from the AA defenses are a solid option.

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They aren't just for transport - they also turn into kinetic warheads

A drop pod has four major components:-

  • Re-entry heat shield
  • High-altitude guidance system
  • Can of meat (ideally not cooked, minced, or otherwise processed!)
  • Low-altitude braking/landing/guidance system

Once you're down to a sensible height and a sensible speed, the first two are simply dead mass when you come to landing. So why not put them to an alternative use?

Once re-entry is done but the pod is still a pretty damn long way up (maybe 50,000 feet), the drop pod can jettison the heat shield and its guidance system. Each pod's heat shield then becomes a rod from God, guided onto targets around the drop zone to clear the area. For bonus points too, the wave of kinetic warheads will swamp anti-aircraft defences and greatly reduce the window where the pods themselves can be targetted.

With this in mind, we have a good reason to have lots of smaller pods for assaulting a defended position. The more pods we have, the more kinetic warheads we have. Larger pods are used for dropping on undefended positions where we don't need that bombardment.

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You have a complex dilemma. Do you use streamlining or atmospheric breaking (AB).

Manned objects entering the atmosphere use atmospheric breaking to decelerate upon entering the atmosphere. Traditionally this is also what SF drop pods have done i.e. rely on AB for their initial deceleration in the stratosphere and higher. And if they have engines at all these are usually just for maneuvering (dodging counter-fire and reacquiring the LZ after having done so) perhaps with a last minute 'kick in the pants' for the occupant to bleed of all but the last dollop of V just before impact. Of course deeper into the atmosphere ailerons can do some of the work as can parachutes. Point is - manned vehicles that do this are not streamlined to resist drag, they depend on it for breaking so they tend maximize the surface area pointed in the direction of their line of flight (think the space shuttle - it came in hull first not nose first) and consequently leave a visible trail behind them.

This is because in most manned flights of the grunt work of deceleration is done by AB which means hull temperatures exceeding 1800 degree C plus a nice long/bright trail of ionized gas. All of which means that despite being able to jam active electronic sensors the capsule are going to scream red on well designed SF style IR sensors. And you'd need massive jamming on the radio frequencies the ionized gas gives off as well.

Second option don't use AB, instead be streamlined.

In this case, like nuclear missiles and hyper-sonic vehicles the drop ship can have have an aerodynamic shape (arrowhead etc) that lets you cut cleanly through the atmosphere like a knife in minimal time and not leave as much of a wake. Except you still have to slow down. Which means once your in the lower atmosphere you have to fly around for a lot longer losing speed until you can land or else install some form of handwavium 'inertial dampener drive' that magically kills off all your velocity.

So either design strategy entails risks (just at different altitudes) and requires (I think) similar flight times without magic engines to save you. Option 1 (AB) you stand out during the high altitude part of the drop. Option (2) You have a quicker, less visible drop to low altitude but then have to loiter there till you kill of most of your velocity. Neither is ideal for obvious reasons.

So if, as you indicate ground defenses are potentially highly accurate the safest answer would appear in the end that lots of small cheap disposable drop pods would be better regardless of the design. They don't have to be one man but you certainly don't want 747 sized pods with a company on board either. Then you just throw them out of your ships like chaff with as many unmanned decoys as possible included in the mix.

EDIT: That's for the initial drop anyway. As your forces secure the drop zone and/or gradually neutralize the air defenses around the DZ you can switch over to larger drop pods, especially unmanned ones stocked with food ammunition and other essential supplies

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  • $\begingroup$ " or else install some form of handwavium 'inertial dampener drive' that magically kills off all your velocity."........ Or a few parachutes. $\endgroup$
    – DrMcCleod
    Commented Feb 1, 2022 at 9:21
  • $\begingroup$ Already mentioned parachutes. $\endgroup$
    – Mon
    Commented Feb 1, 2022 at 9:44

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