Plane-dropped minisubs

I find minisubs to be fascinating. I was writing a fiction series involving navies using all those wacky ideas in WWII that never really took off. I know the Japanese in WWII used minisubs in many applications, and there are plenty of examples of unconventional uses for vehicles.

My idea is to have a minisub that is air-dropped to increase its operational range/speed. They would be deployed in a picket ahead of enemy fleets/merchant ships. Air transport would also be extremely useful for gettting around natural obstacles, like capes, sandbars, or reefs- rather than having to navigate through a windy channel a plane could fly straight to open water and plunk the sub there. Having multiple little submarines attacking a single target might be more effective than a single submarine firing a torpedo spread, and multiple ‘layers’ of minisubs would make a nice force multiplier, with an enemy fleet constantly getting harassed. If they were carried by plane, this also means they could be land-based, allowing a plane to take off from an airbase (allowing a bigger plane to carry them, or carrying a bigger minisub). The minisubs themselves would be semi-suicide craft; theoretically they might have the range to work their way back to a friendly fleet/port, but being air-dropped would mean they might be deployed in an area where there’s simply no way to recover them.

How feasible is this? I’d be surprised if no military ever even romanced with the idea; hell the soviets had airdropped tanks dropped via parachute :eek:

I think the biggest challenge would be weight- the sub would have to be small and light enough to be carried by an airplane of reasonable range and speed, yet have a torpedo warhead strong enough to be an actual threat to larger ships, and enough speed and range to both maneuver and possibly return home.


Oh yeah, and I also almost forgot about that whole ‘finding a way to get this miniwondersub dropped from the air to the water without it shattering like a lightbulb’ :eek:

My initial reaction is that to make this practical, you simply need to go with unmanned minisubs. These could be much smaller and lighter, would not have all the logistical limitations that crews entail, and would deal rather efficiently with the problem of being sometimes unlikely to make it home.

Another name for “unmanned minisub” would be “long range torpedo”. The point of a submarine is to launch torpedoes, if you have an unmanned sub that can launch one torpedo what’s the point of the sub half of the system?

I think the biggest problem is that a submarine’s greatest asset is secrecy. You want them waiting where no one suspects them. If you see a bunch of enemy planes dropping little submarines into an area of the ocean, you’re probably going to sail to some other part of the ocean.

Better still, if you see an enemy plane that carries a sub, send up one of your planes with depth charges to the same place. They drop the sub, you blow it up.

Dropping the subs is easy, with a big enough parachute you can get a relativily gentle landing. The problem is that the light weight of the subs would reduce the crush depth so the subs would have to stay near the surface. This makes them more vulnerable to sub hunting aircraft and ships.

You might be able to do it with a specially modified (and very large) flying boat- fly to the launch point, land, open a section of the bottom of the hull, deploy midget submarine, close hull section, plane takes off, sub commences mission.

Bear in mind that some 1940s flying boats could carry other (smaller) aircraft, so it’s not completely unrealistic…

No particular reason why such a device should be limited to a single torpedo. In addition to torpedoes, there could be sensors and the ability to relay information.

Japanese Midget Subs had quite a big psychological impact in Australia despite only have two torpedoes each in them. Their larger “mothership” submarines also caused panic by shelling Sydney harbour with their 140mm main guns, although they didn’t actually cause a great deal of damage.

Didn’t they also cause concern for Gilligan’s Island?

David Brin used this idea in his story Thor Meets Captain America (which despite its title has nothing to do with Marvel superheroes).

It wasn’t just the Japanese who used minisubs – the Allies did, too, especially in the Mediterranean. See the Ballantine Illustratedf History of WWII series book Weapons #42Midget Submarines

AFAI Can Recall, no one air- dropped them. In the first place, they weren’t all that robust. In the second place, they were all about stealth, so they tended to be launched underwater.
If you’re doing it in the modern day, I can easily see a dropped unmanned minisub used for surveillance, traffic monitoring, and maybe attaching a few limpet mines.

I was coming in here to mention this (very, very cool) story.

So did the United States, no big deal.

What you’re probably thinking of is the Soviet flying tank.

I can’t really see the point of dropping a midget sub in front of a ww2 convoy…the sub needs to do a lot of tasks (run for several hours on heavy lead batteries, be able to sprint to position using big diesels, etc) which are hard to fit into a tiny sub. If you have a plane big enough to carry the sub into mid ocean, why not just have it torpedo/divebomb the convoy outright?

A possible use for an air dropped midget sub might on the other hand be to sneak around in a harbor to mine something anchored there, much as the Brits tried to do with the Tirpitz in Operation Source.

To be effective they’d need freakin’ lasers on top of their freakin’ heads.

I think it’d be more efficient to just drop unmanned UAV-esque submarines, either with torpedoes on them or dropping the torpedoes separately.

Not very feasible. For one, you have a pressure vessel that is highly sensitive to stress, and yet you’re dropping it from some height onto the ocean surface, which is like dropping an egg on concrete. (Even with parachutes, the fall rate will still be at least a few feet per second.) A torpedo actually damages a submarine not by direct impingement (contact or shrapnel), but by creating a large void that causes the hull to be overstressed and crack; ideally, a bubble is created under the midships that causes the hull to fold and snap like a string bean. As you can imagine, a hard landing on the ocean surface would be very hard on hull integrity.

Second, as noted, dropping a sub inside of a harbor or inland sea would be suicidal. It is better to sneak, say, a commando team in on kayaks or transiting underwater using a diver propulsion vehicle (DVP) at night to perform reconnaissance, attach limpet mines, or deploy netting to interfere with shipping. Although electric minisubs can be very quiet, their utility is quite limited, and are mostly used in modern navies for exploration and rescue operations (like the DSRV).

Third, modern submarines don’t fire a “spread of torpedoes”; this technique may have been used during WWII era (although the limited carrying capacity of most subs would have caused most captains to be parsimonious with their unguided torps), but modern submarines will deploy one or two ‘fish’, which are generally controlled remotely by spooled wire. A defending sub will often return by firing a ‘fish’ at the attacker in hopes of forcing the latter to cut wires and run, breaking the engagement and leaving the attacking torps with only local homing capability which is easier to defeat with tactics and countermeasures.

Fourth, a minisub couldn’t carry large enough torpedoes to attack a sizable target. While the Japanese did deploy two man ‘midget subs’ in the Pacific during WWII (and after reading the Mad Scientists’ Club story about this I wanted to acquire one), the reality is that these were basically harassment and were not much of a threat to either warships or shipping.

A better plan is autonomous underwater vehicles (AUV) that are capable of running independently, reporting back data, and if armed, attacking shipping or enemy vessels in the same way that UAVs do for airspace warfare. The US, Great Britain, France, Russia, China, and India are all spending significant effort to develop this capability. In addition, an air-dropped version of the Russian supercavitating Shkval torpedo would be a very effective long range submarine weapon, especially if it could be deployed from a cruise missile-type platform or a ballistic maneuverable re-entry vehicle (MaRV). This would allow a long range attack into protected harbors without any suicidal mission planning.


My idea was based on WWII tech. Minisubs have some advantages over conventional subs: Their small size allows them to navigate through shallower water. They are cheaper to build and require less manpower (The Japanese built hundreds in preparation for a US invasion that never came).

Deploying them via air means you can put them in places the enemy will not be expecting. Obviously it would be foolish to let the enemy see your squadron of planes carrying minisubs in some direction. Air transport overcomes 2 inherent disadvantages of minisubs- range and speed. Planes could quickly deploy them to where they might be needed, and they could (ironically) be based on land, far from ports or submarine pens. The planes could transport them long distances, greatly increasing their operational radii.

The point of having planes that carry little submarines that carry torpedoes (as opposed to simply planes carrying torpedoes) is an issue of endurance. The planes could deploy the submarines as a picket, which could lie in wait, harass, ambush, or reconnoiter enemy ships, while the planes themselves can only stay in the air for so long.

Its true that smaller torpedoes make a smaller bang. But it doesn’t take a lot of oomph to break a ship’s keel or blow off a propeller or rudder.

I don’t think I’ve made a Grail reference in years, but for some reason I’m hearing “now, Lancelot, Galahad, and I wait until nightfall and leap out of the rabbit, taking the French by surprise!”

Clearly not the same, but … but … how do the brave submariners get home?

“Hello! Hello out there! Can anybody hear me? I’ve eaten my sandwich. I’d like to go home now. Hello? Anyone?”

The Japanese midget submariners solved that knotty conundrum by not expecting to get home- the crews of the midget subs that attacked Sydney all committed suicide rather than be captured, and they must have known it was unlikely they’d get into Sydney Harbour, torpedo some ships, then get back to their motherships in one piece.