# Orbital Drop Pods: Useful?

Orbital Drop Pods are a new-coming part of Futuristic science fiction. Triple A games like CoD: AW and Titanfall feature them as ways to easily reach ground level by cramming armament (such as soldiers or Titans) into metal pods equipped with descent thrusters or shock absorbers to slow the fall. Like a H.A.L.O drop in a tin can.

What I'm asking is this: are they militarily sound compared to other alternatives, like the common parachute? What do they have to offer in terms of benefit, or are they just expensive health hazards?

• You might want to look at the HALO universe where drop pods are used to deploy special forces from space. Or even earlier Heinlein's Starship Troopers. – dot_Sp0T Nov 26 '17 at 10:04
• Check out Starship Troopers (the book, not the movie). Chapter 1 has a well described and engineered drop pod system, and heinlein describes how to make it tactically sound. Book is copyright 1959. – pojo-guy Nov 26 '17 at 13:11
• Worth noting: terminal phase ballistic missile defense programs like THAAD are literally designed to shoot things like this out of the sky. – Cort Ammon Nov 26 '17 at 16:08
• In re shootdown: just like you wouldn't do an amphibious landing without air superiority, you wouldn't use drop pods without space superiority and air superiority including taking out the air defences. This implies you need some kind of space-to-atmosphere fighter/bomber too. – pjc50 Nov 27 '17 at 10:31
• @Malkev Except WH40K is not exactly innovative when it comes to concepts. As pojo-guy says, Heinlein had this idea in "Starship Troopers" in 1959. Even then, it's only a space equivalent of military gliders which were heavily used during WWII. – Graham Nov 27 '17 at 13:20

# Retro-propulsive landing

Pros:

• Fine control over landing location
• Softest landing of all
• Cheap re-usability
• Potential to land on bodies with little or no atmosphere (mars, the moon)

Cons:

• Anything near the landing location will get burnt to a crisp
• Expensive production

# Parachutes

Pros:

• Cheaper production
• Safe landing (unless you happen to end under the drop-pod)
• Passive system requiring little supervision

Cons:

• Unable to land on bodies with little or no atmosphere
• Little control over landing location*
• Little potential for re-usability

# Hard-landing / Lithobraking

Pros:

• Fast delivery
• Cheapest production
• Can land anywhere
• Requires no supervision

Cons:

• Very hard landing, unsuitable for human use and delicate cargo
• No control over landing location*
• Non-reusable

# Bottom line

Considering the above, I'd say each system has it's uses.

• Retro-propulsion is best for landing delicate cargo and people in friendly territory on designated landing locations or behind enemy lines for critical missions (too costly to use unreservedly).

• Parachutes are a good way to drop cargo or people in a wide area, useful for for large scale attacks or incursions where precision is not essential but numbers are.

• Lithobreaking is a practical and inexpensive way to quickly deliver durable supplies such as food, water and certain types of ammunition in case of an emergency.

* Both parachutes and hard landings can be guided with specialized equipment (steerable parachutes and aerodynamic control surfaces) in exchange for an increase in cost and the need for active control and guidance systems

If you are asking about the benefits of an orbital drop versus a non-orbital drop, then it simply depends on whether the things you are dropping come from/are manufactured in space.

If you need to lift things to space just to drop them back down in the same planet then it hardly has any benefits at all. Unless you have an inexpensive way to get things to space, such as a launch loop, in which case the greatest benefit is speed.

• Retro propulsive, con: heavy, due to weight of fuel. – Draco18s no longer trusts SE Nov 26 '17 at 17:34
• Retro propulsive, con: not stealthy at all. Anything nearby will hear and anything from up to a mile away or more will see the landing, and any sleeping enemies will be woken up by the sound of a rocket landing in their backyard. – TylerH Nov 26 '17 at 19:03
• @kingledion no, it isn't. A parachute can easily be (and is traditionally) made of non-conductive materials which are challenging (though not impossible) to resolve on primary radar, while powered flight components tend to be reflective. But it's a somewhat moot point - pretty much any aerobraking re-enty will leave behind an outstandingly radar- (and likely optically) visible ionization and abalation trail that would cue interested parties to make a more intensive radar search for the subsequent and perhaps more stealthy subsonic landing phase. – Chris Stratton Nov 26 '17 at 19:46
• Retro Propulsive Landing > Cons > "Anything near the landing location will get burnt to a crisp". One would think that in a battle, behind enemy lines, this would be a benefit. You have swathes of enemy forces heading towards a location. Dispatching troops to counter the forces in this method not only destroys a large amount of the existing force, but also (after a momentary orientation of the soldier inside -- which could probably be offset/reduced through training) helps to get rid of the rest of the force, and helps to disrupt the formation. It brings a whole new dimension to battle. – Finn O'leary Nov 27 '17 at 0:38
• You probably mean lithobraking? – Ville Niemi Nov 27 '17 at 6:20

Always keep in mind that landing method is determined by the cargo. Humans can only survive a certain amount of G-forces (deceleration, velocity change, whatever term you want). Exceed that amount, the person dies.

Likewise, equipment can only survive so much. A lump of iron can take a lot more punishment than a person or a computer, but it has its limits.

I state this stuff up front because it changes the nature of each drop pod.

For Humans, Heinlein gave the best description of a useful, effective pod that I have ever read. It has multiple layers, and gives off chaff and decoys as it falls. Each layer gives a different bit of decelerating technique starting with free fall and just plain taking advantage of the idea of terminal velocity, followed by streamers, then parachutes, and finally Jet braking that were part of the combat suit. The biggest downside is that the element of surprise is pretty much non existant. Once your guys hit the atmosphere, the enemy aware they are coming. The different layers shed off and create chaff so that anything looking to track heat or Radar will have a nervous breakdown.

Same thing can apply for equipment, but it can fall faster and hit harder for the most part. Just keep in mind the durability limits of whatever you drop. there may be some things you cannot drop at all and will need to use some sort of shuttle craft for.

TLDR; Drop pods are viable and useful, so long as you pay attention to the cargo.

• The problem with chaff as layers shed is that they're shed, so by definition they're going to start reacting differently to atmospheric friction, and slow down faster than the more intact drop pod, which means the pod is going to leave them behind very quickly. By the time the pod has slowed to a terminal velocity, the chaff will be left far behind and the pod is going to be a prime target. – Keith Morrison Nov 27 '17 at 4:11
• @KeithMorrison That depends on the type of cargo: a highly trained, genetically engineered supersoldier in a robotic suit with nanoweapons would probably worth using a dozen decoys. – zovits Nov 27 '17 at 16:03
• @zovits But in the case of Heinlein's Jump Infantry, the imperative is to bring the gear back. You're cheap and replacable. The hardware is not. =) – Cort Ammon Nov 27 '17 at 18:57
• @Keith Morrison The simple solution to this is that early drop pods create a chaff cloud for later drop pods. Put a small wave of decoys through the atmosphere first with real pods following a fraction of a second after. ;) – Muuski Nov 27 '17 at 19:06
• Secondly, if the chaff is magnetic and the pods have a field around them: the chaff tries to follow the pods and could act as resistance/parachutes. Although the field potentially gives another way to track the pod... – Muuski Nov 27 '17 at 19:09

One benefit to using drop pods for an orbit-to-ground assault is that they are a much harder target to hit than a drop ship. Due to their small size and high entry velocity, it is really hard for AA guns to aim for individual drop pods. A drop ship, on the other hand, would be much heavier (requiring a slower velocity), would be a much larger vessel to hit.

Drop pods with individual soldiers or small groups of personnel are also much cheaper and more expendable than drop ships carrying tens of soldiers on board. If the enemy were to shoot down a one one-man drop pod out of a hundred, it would be a much less damaging loss than if they shot down a ship with a hundred people on board.

• Depending on the type, some AA guns have explosive shells that detonate making a shotgun effect in order to have more % of hitting the enemy aircraft , not to mention computer tracking with laser is not that hard to implement if you know you need to blow up some targets like these. – Kaotis Nov 27 '17 at 15:49
• If it was that easy to hit high-velocity stuff with AA, no-one would be freaking out about North Korea getting missiles. – Dan W Nov 28 '17 at 22:37

It all depends on actual engine technology used.

If reliable and cheap enough (better than SpaceX) the benefits, from military point of view, are:

• brake at lower altitude (less time being a an anti-aircraft target).
• large part of incoming trajectory at high speed (same as above).
• last-second maneuverability to chose the right landing spot.
• largely unaffected by meteo conditions (especially wind).
• possibly a softer landing (no final "bump", dangerous with heavier equipment).

Where do the drop pods come from?

If they're dropped from an orbital platform, like a space station, then logistics are a nightmare. You'd need to keep the station manned with enough combat troops and pods so you can drop them at a moment's notice. The men will need food and the equipment needs maintainence.

"Moment's notice" is also a problem. Assuming a low-earth-orbit, you'd probably do one orbit in about 90 minutes. If something happened right after the station left the target, you'd have to wait 90 minutes to drop, maybe more if the target is significantly north or south of the station and you have to wait for things to line up.

The element of surprise is not that great either. Even amatuer astronomers can watch the international space station using off the shelf equipment. If any nation on Earth built an orbital platform for deploying drop pods, every other nation would monitor that platform 24/7. As soon as a pod was deployed, its likely landing zone would be estimated.

The low orbit also makes it vulnerable to attack. China has already demonstrated the ability to attack orbiting satellites. Even North Korea could probably knock out something like the ISS.

Finally, this gets back to logistics, what happens after you drop your super-soldiers way behind enemy lines? Who comes to pick them up?

Furthermore, what purpose do the drop pods serve that can't be met with conventional technology? We already have ICBMs capable of hitting any target on Earth within 30 minutes. We can get B2 bombers to any target in far less than 24 hours. What niche do the drop pods fill?

• Territorial conquest. – WorldCraftTrainee Nov 27 '17 at 5:27
• I think OP's drop pods are meant to be used when invading other planets - when a race have the capabilities to take their military to a different celestial body (possibly even a different star system), the logistics problems you raise here are probably negligible. – G0BLiN Nov 27 '17 at 13:42
• When you mentioned estimating the drop zone, the first thing I thought of was launching an artillery barrage that would land at the same place same time....Ouch. – Muuski Nov 27 '17 at 19:11
• @Muuski that probably wouldn't be all that difficult to arrange, Unless the drop pods have some kind of technomagic drive that just completely ignores physics, there's going to be a blazing beacon (in radio, visible light, and infrared) pointing right at the dropzone from the re-entry heating. – Leliel Nov 27 '17 at 19:25
• I took the OP question to mean a ship comes in, drops stuff, maybe orbits a few times, then retrieves and leaves after the area has been sufficiently pummeld. Drop troops, for the most part, are not stealthy. – Paul TIKI -Monica come Home Nov 27 '17 at 21:32

Something I haven't seen anyone else mention.

Drop pods aren't remotely stealthy, it'd be virtually impossible to make them so. So make the problem a feature. Consider the massive element of shock and awe this sort of assault would produce. Sonic booms, streaks of fire across the sky, it'd be the stuff of myth and have an exceptional effect on morale, both yours and your enemy's. The arrival behind your lines of well equipped fresh troops alone is a serious problem that will demoralise your forces.

From orbit, you can see the disposition of the enemy, see their emplaced defences and such. If you can place fresh and well equipped troops wherever you want at about three or four minutes notice that gives you a tremendous ability to reshape the battlefield.

Comments here discuss the idea of drop pods being deployed from a permanent military facility in orbit as a rapid-response force, that's one option, but depending on the setting that's not the only platform to launch them from.

In Warhammer 40,000, Drop pods are used extensively to get power armoured shock-troops into the fight, the doctrine displayed there is to arrive in orbit aboard a large dedicated barge and begin raining pods immediately. give no time to react or respond. For comparison (and the original inspiration for the Warhammer example) Starship Troopers in Heinlein's book of the same name are fired at the planet in individual pods and collected after the fact in dedicated dropships. Those pods arrive surrounded in chaff, flares and ablative plating from their own pods, making it essentially impossible to pick out the trooper himself with anti-aircraft fire.

In the Halo franchise, the same concept is applied to the rather tellingly named "Orbital Drop Shock Troopers"

In every case I've seen in fiction, Shock and Awe is one of the primary effects and goals of drop pod assaults.

I've never read of a pod that arrived using parachutes as its primary deceleration technique. All of them used retro-rockets, sometimes drogue chutes as well. The goal was to arrive as hard and fast as possible without injuring the passengers.

• I'd also like to mention that in Section 8, you are dropped from a high-altitude ship, but each soldier is dropped individually to land in their combat suits. They are able to fall and change their course like sky divers (if desired), but without having to worry about deploying a chute and with a person sized radar blip. The other option is to sacrifice movement for higher speeds and just crash into the ground at terminal velocity (though they do flip over at the last seconds to land on their feet). I'd also say that nothing is more Shock and Awe than landing on the enemy also. – bubbajake00 Nov 27 '17 at 15:05
• "The goal was to arrive as hard and fast as possible" - also because of anti aircraft fire. This is not "move troops", this is "Normandy Landing" in a space environment. it is about trying to avoid losses as much as possible / feasible - and there is no good solution unless you can do a full stealth landing, which has serious physics issues (orbital velocity, hiding in space) and requires a very high near magic tech level. So, arrive, start dropping kinetic strikes, start dropping chaff and dummies and drop pods and hope most get through. What are the alternatives? – TomTom Nov 27 '17 at 15:53

I'd say it depends on the tech level of the adversaries. Let's drop a pod from orbit...

Unless it uses flummoxion-drive antigravity or something, it will have to decelerate using atmospheric braking, like the space shuttle, or retro-rockets ala SpaceX, or both.

This means it will get very hot, and become a perfect target for cheap heat seeking missiles.

Atmospheric braking works well for fast objects, but once most of the speed is lost, you will still drop like a brick unless you have wings, parachutes, or any other means of propulsion like rockets, helicopter rotor, MHD thrusters, etc. Deceleration needs to occur over a sufficiently long time span to not kill the people inside from G overdose, so you can forget about shock absorbers.

So... your drop pod is still very hot from the orbital descent, and now it is slowing down and preparing for a soft landing (since it contains squishy humans) under a parachute.

Just fire a Stinger or other man-portable air-defence. According to Wikipedia, it costs $38000, but in your near future world it should be cheaper. It is also available on the black market pretty much everywhere. Note this would work day or night... IMO in order not to be shot down the drop pods should aim for a point far enough away from the hot zone, then deploy some wings and fly the rest of the way hugging the ground at low altitude. Add some automated guns to shoot down any incoming missiles... why not. So you get something like an helicopter, more or less. Or an A-10 with a mech strapped under the wing ready to be dropped. Except it has to survive orbital descent, which presents an interesting problem. • Maybe you make the heat-shield detachable (after loosing most of the speed)? – Paŭlo Ebermann Nov 26 '17 at 19:41 • Targeting a drop-pod with a stinger won't work. Something like THAAD would be required to intercept at that kind of speed – unless your drop-pod burns off all its speed too soon and decends slowly for 10 mins on a parachute at the end, which would be kinda pointless, and would pretty much be a parachute deployment, not a drop-pod (the OP is asking about drop-pods as opposed to parachutes). – Dan W Nov 28 '17 at 23:31 Consider who might be using them, and in what situation. In the Night's Dawn book by Peter F. Hamilton, an opposing force uses the cover and resulting debris from a destructive orbital engagement to seed a planet with drop pods. Since the occupants of the drop pods are supernatural in ability, they only have to hit the surface of the planet to successfully infiltrate it. It's a very large target after all. Obviously this tactic would get significantly harder against a planet that has good defenses, but on a developing, or poorer world this would be most effective. Considering that the scenario is on the same planet country vs country: For landing troops from a strategic point of view a very niche use case scenario where you need x heavy armed extremely well trained guns at point C without going through point A and B, in the case of cargo/munition etc sure it makes sense but if you already have troops in the area you most likely control the area and can transport by land or air which would make it cheaper than a drop pod program. Not mentioning ofc the fact that if your troops are surrounded the corect (not ethical*) strategic decision is to let them get captured then try to rescue them rather than sending them munition which might get in the hands of the enemy and just prolong the fight which will end up killing more of your troops. Heavy armored vehicles sorta make sense only if used to move them fast at choke points and surprise the enemy. Planet vs planet scenario: Most effective way to take the fight to the enemy , landing a full fledged starship might result in being to difficult. So rather than losing trillions of$ in a starship destruction if we lose a few pods/troops at most it will be a few millions .

To summarize: For most combat situations drop pods would be absurd both strategically and economically. Not to mention that any anti air defense system would result in heavy loses .

Edited* : Just a thing i forgot : if you have the tech to launch effectively and rather securely pods on X location where most likely there are enemies ... i would suggest dropping some MOAB/FOAB s -like sized bombs rather than risking the life of your troops.

• The problem with dropping a bunch of MOABs and moving on is that massive destruction is not the point. The purpose of war/bombing/invasion is to get a group of people to do what you want or stop doing what you don't want. Annihilation is almost never the goal. Getting boots on the ground to hit and selectively destroy and kill stuff is more effective as you can wreak havoc and leave use-able infrastructure. Use the right tool for the job. – Paul TIKI -Monica come Home Nov 27 '17 at 21:29
• Well i was thinking more in the lines of storming a heavy fortified target so instead of hitting a hard target with troops the idea would be to soften them up a tad bit – Kaotis Nov 29 '17 at 7:07
• Taking a fortified target is one of things where you have to analyse your end goal. You can use them against the enemy if you leave them intact, but the cost is high in manpower because you need to be way more precise to neutralize defenders without damaging fortifications. If you don't need the fortifications, by all means, reduce it to rubble. Just depends on the strategy – Paul TIKI -Monica come Home Nov 29 '17 at 17:22

Let's consider ICBMs as a starting point. Re-entry time from 100kms is 2mins, and speed is typically 7km/s. Until they start re-entry, they're hard to track, as there's no rocket or re-entry heat. (Data from wikipedia)

100kms is obviously way lower than LEO. Two options are possible:

• They could be fired from LEO or a higher orbit. A number of other answers point to the high visibility of a retroburn. That may not be a huge issue if you don't know where they're going to land – and because they're hard to track until re-entry, it's not unlikely that the trajectory could remain hidden; I don't think a retroburn would necessarily be enough to make their trajectory known, especially if we try to obfuscate them; I think from an LEO even a fairly small change would have a substantial impact on landing point. Also, just because current reentry methods are very visible, doesn't mean we can't develop more subtle ones. There's never been any need to do so, so I doubt much research has been done. A civilisation otherwise capable of space travel would likely have other options.
• They could be dropped from high-altitude space-ships, or even deployed surface-surface via a missile system.

In either case, whilst in space, they're pretty safe, as they're hard to spot.

We've now got the issue of breaking something from ~7km/s.

Wikipedia gives the max acceleration for a human on a rocket sled at 46g. (wow!) Let's take that, and assume that a civilisation otherwise capable of droppods can find a way to reduce the effects of deceleration. We're thus looking at decelerating from 7km/s: 46g = 7000m/s / 152s – so two and a half minutes of breaking at max deceleration. It's gonna have to be rockets; parachutes won't provide that deceleration. Lithobraking will be Lithobreaking, unless we've got some handwavium device to reduce the effects of deceleration – or we're dropping from substantially lower.

But, hold on a minute, why are we assuming we're dropping humans, and not combat robots? Suddenly, the deceleration issue largely disappears. We can decelerate a robot very fast (though again, probably not pure lithobraking – very little will survive that kind of impact).

How interceptable are these? Hmm... A stinger can be ignored; if that worked, they wouldn't have had to develop THAAD. We can assume THAAD isn't anywhere near 100% effective, as if it were, we'd not care about NK's missiles. Also, it's very expensive per shot.

So if we drop some empty pods or similar, we can easily make it too expensive to shoot them all down. Also, how many anti-drop-pod missiles would be available to fire concurrently? We can likely just drop far more pods than can be shot down at once.

So survivability is likely to not be an issue.

Back to the original question: are they militarily viable?

• Currently, the vast quantity of rocket fuel they'd require would make each one extremely expensive, but a civilisation capable of space flight has presumably overcome the fuel cost.

• They'd not be stealthy, but given the speed, how quickly a target would realise they were the target and respond is debatable.

• It's unlikely they'd be fast-response, due to the time required to plan for their launch and be in the right place in orbit to launch (unless they're deployed by some kind of missile?)

TL;DR:

So we're looking scenarios which require a planned, but very fast, deployment. Potentially preceded a few seconds earlier by a bombardment (which also might intercept interceptor missiles). Great for any kind of attempt to secure a logistics point (bridge, transmitter, etc) or other asset which wouldn't respond meaningfully in the max ~2 mins warning they'd get. Probably not so great for a coup d'etat, as they're more likely to realise they're being targeted and respond, but still a viable option.

If we're dropping combat robots rather than humans, then much more viable.

Is dropping into the sea an option? Whilst an unprotected human hitting the sea at high velocity is pretty fatal, inside a drop-pod might allow a fairly high-velocity landing? (I've not run any maths).

This might be a cheap way to deploy a large number of soldiers at high speed (and hence harder to shoot down). They'd probably have to slow enough that they could be shot down, but if you're doing a large invasion, the numbers would mean that shooting down a sizeable proportion would be problematic. Also, there's significantly less defences at sea.

Of course, this means your troops are now deployed at sea, but you could either land somewhere safe and then attack from there, or do a direct sea assault (you'd probably want to drop entire squads in amphibious/submarine capable landing vehicles).

Might be an effective way to land troops past planetary defences that might be capable of taking out a few large spaceships, but no use against a few thousand squad-sized drop-pods. Dropping to sea would allow much faster deployment than parachute to land, and the sea would hide them as soon as they go under.

• While I was mostly considering land targets, launching armament into the ocean is A Really Good Idea. With future technology, we could easily launch sea mines, drones, and other non-human devices into naval ops. Interesting idea! – WorldCraftTrainee Nov 28 '17 at 23:42

Depending on what you want to do, laser-powered drop pods may be a good option.

External laser propulsion is studied today as an alternate to chemical rockets for launching payloads to orbit, with massive ground laser installations. This is essentially the same concept inverted.

It is similar to powered drop pods, but the energy source is a laser battery on the carrier station/ship. It is rather similar to conventional rockets, but the propellant is heated by the external laser instead of an on-board chemical or nuclear reaction. This allows the pods to be significantly simpler, lighter, and more robust as they don't carry a massive energy source that may want to blow up or otherwise fail in unfortunately energetic ways.

Obviously, the lasers may also be used for orbital bombardment to suppress, for example, ground defences threatening the pods.

Those pods would use on-board propellant for manoeuvring in vacuum, but they wouldn't need a big reserve compared to chemical or even most nuclear propulsions: the laser can heat the propellant up to very high temperatures, meaning that the engine is much more efficient in its propellant consumption.

Once in atmosphere (if there is any) and once aerobraking (the "shooting star" phase) is done, they can use atmospheric air as propellant, so they have effectively unlimited manoeuvring range as long as one laser station is overhead. They can even use the drive to get back up to suborbital trajectories for coming back to the station - though they will still need some propellant reserve to finish putting themselves on orbit, as the last burn has to be outside of the atmosphere.

This is of course assuming you have orbital superiority (or that it is not a contested landing), but you would probably not want to send infantry if there was still heavy weapons pointed at you anyway.