Are there any good alternatives to firearms for 1920s aircrafts?

Question

Short and simple are there any actually effective alternatives to firearms as the main alternative for WW1-1920s era aircraft including biplanes and airships?

Rules:

1: The weapon must be able to be mounted on the vehicle.

2: The weapon must be actually effective at either dealing with hostile aircraft (assumed using similar or the same weaponry), infantry, armored vehicles, or all of the above.

3: The weapon must not be a conventional firearm in any way. This means no self contained projectile that use black, smokeless, or chemical explosive to propel a projectile via combustion. Rockets are an exception to this.

Research and argument:

In short I am wanting to design hypothetical weapons for a universe in which technology has advanced into around 1920s tech generation wise, but there are no fire arms to speak of. Please do not ask why it is massively complicated, and yes gunpowder, fireworks, and explosives exist. No massive cannon artillery, no machine guns, no rifles or pistols in the conventional way.

For ranged weaponry I have come up with several ideas that can be utilized to great effect I feel. These being mechanized crossbows using compressed gas to cycle a feeding mechanism and reset the tension system which can either use a conventional bow shaped tension bar or even springs. Think something like how the Hellsing crossbow functions in the movie, but actually plausible. These crossbows can be semi or fully automatic. There would also be large mounted ballista type weapons for the equivalent of cannons that even have explosive tips for armor piercing capabilities.

Another ranged weapon I have an idea for is simply a high powered air gun. Lethal air guns have been around for quite a long time. We’ve had air guns since 1580 and they were used to hunt big game like boars and deer from the 17th to 19th century and could reach velocities of over 1000 feet per second. There have also been airguns used in war such as the Windbüchwe or the Girandori rifle, both of which were noted to have great lethality and effect when in the hands of experienced marksmen. So simply I thought that considering the lack of conventional firearms would cause significant advancement into airguns. These would mainly exist as either the equivalent of bolt action requiring manual cycling of the ammunition store or semi automatic. There would also be fully automatic handheld and mounted airguns.

Expanding on my airgun idea, I also thought of utilizing large caliber air cannons to deliver explosive payloads, as well as armor piercing rounds that could have internal rockets that aid in propelling the projectile further through the armor. This idea is a logical upscaling of airguns and draws inspiration from historical weaponry, such as the dynamite cannons used on the U.S.S. Vesuvius that had a range of over a mile and were capable of blowing cellar-sized craters into the earth.

Next up we have rockets as these could be a really good ranged weapon. Unfortunately you won’t see any Gyrojets here as those were kind of a laughable failure. My main ideas for rockets would be to use them as long range artillery in the form of Katyusha-like launcher systems as well as anti-vehicle weapons.

There are various other weapon ideas I had such as compressed air grenade launchers, flamethrowers, and electrified melee weapons, along with air or spring propelled tasers. Bolas and electrified nets fired from guns were considered as well.

The problem I am having is a coming up with a creative and effective ranged weapon for air-to-air dog fights and anti-infantry ground attack runs for aircraft. Crossbows are not the best idea unless they're explosive tipped or fully automatic, and specifically constructed to function on a plane. While I like the idea of using airguns for planes, and having large air machine guns that can utilize the extra power from the engine and additional air from the intake to fill the compressors easily, for some reason it doesn't feel as satisfying to me. It seems like it's just a "gun reskinned" and lacks creativity.

Finally, small air-to-air unguided rockets with a small explosive payload mounted in rocket pods have been proven over and over again in real world combat and rockets were used to great effect by planes in WW1, but if the rockets are too large then ammunition would be very limited, and if they are too small they could be underpowered.

Ultimately I want to form a creative solution to all of these problems, hopefully using a mixture of all the ideas I came up with and possibly hear any weapon concepts I may have overlooked or have no knowledge of. Any help would be appreciated.

(Also sorry if my format is off, my grammar or writing is bad, or this ask just doesn’t make any sense as I am writing this late at night and this is my very first post here.)

Answer 1

Problems: Drag and speed

There are two problems with low-tech projectiles aerial combat:

1. High relative speed of aircraft, which leads to high maneuvering speed.

When you shoot an arrow (average 50 m/s mid-arc velocity) at a ground target, the fastest it can be moving is 10 m/s, and usually not even that. So you need to aim at most about 20 degrees to the side of the target.

When you shoot the same 50 m/s arrow at an aircraft, that's a 100 m/s target. If it's moving in any direction other than your own, you basically have to shoot sideways. It's unintuitive and very hard for a human to predict where the flight paths will cross. Often, the target will have to be outside your field of vision to hit it.

Try it in a combat flight sim - even with a modern cannon, which has 3x the velocity of a maneuvering aircraft, it's difficult without using the HUD to assist you. It's easier with slower WWII aircraft, when the bullet is 5x-8x as fast as the airplane. But arrows and crossbow bolts offer, at best, 1x, which just isn't enough to hit in any position other than a straight tail chase. Shooting arrows at a plane is like chasing a rabbit by releasing tortoises at it - if you time the tortoise just right...

2. Extremely high drag, which quickly saps the energy from any projectile.

For the purposes of drag, the velocities of your projectile and the aircraft are added together. Drag grows as v^3. So a 50 m/s bolt will experience 27 times more drag when it's launched from a 100m/s aircraft ((100+50)^3/50^3).

It means that its range, in terms of covering the relative distance between the planes, is reduced to just 1/27 of what it was on the ground. OK - maybe not that badly, if you're at altitude, where the air is less dense. But you're still looking at an effective range of less than 100 meters, which, in the air, is extremely close to collision.

High drag also greatly reduces the kinetic effect of the projectile.

3. These two problems synergize. High drag makes relatively slow projectiles even slower mid-arc, further increasing their flight time, and thus the distance the target can move.

Due to these two problems, low-tech alternatives don't work. Airguns don't have enough velocity, and the balls produce too much drag to be useful at all. Problems 1 and 2. Arrows and crossbow bolts are shaped a little bit better - like a missile - but they really lack in velocity. Air combat requires guns with high supersonic muzzle velocity just to reach the target.

We've had a question with multiple exhaustive answers on how non-ballistic means of powering a projectile can work on the ground. Very effectively. The common feat of non-ballistic weapons, however, is a combination of high mass and low velocity. The sole exception is electric guns, which are high-tech and definitely not 1920s-doable.

"Slow and heavy" simply doesn't work for aircraft, which fly faster than any arrow, airgun pellet, or whatever else, short of a bullet.

Directed Explosives

Enter explosives. What you're looking for is something akin to a Claymore Mine.

It doesn't have to be propelled, just mounted on the airplane in a fixed position. Attach it to wingtips or below the wings, like a missile.

Or it can be propelled by a rocket, or even a spring. Any propulsion is just a means of protecting yourself from the back blast. Basically, you try to intercept the opponent's path and deliver a wide spread of fragments in their general direction. Explosive-driven fragments exceed 1 km/s, which is generally what you need for aerial combat.

The "directed" part is important. Without firearms or missiles, even with propulsion, your range is going to be so short that your own aircraft will tend to be in the blast area of a conventional unidirectional explosion. Directionality is provided by shaping the charge and installing a thick backplate that can survive it.

It still beats ramming the enemy aircraft.

Rams

Without firearms or explosives, your fastest, most accurate, and most potent weapon is yourself. Hitting one aircraft with another takes some skill, but it's been done.

Aerial ramming has been used successfully in WWII. It was highly effective and the rammer often survived. After the Soviet success, the Germans even created a ramming unit (same link). With a dedicated, jettisonable/brekaway ram, mounted below the propeller, you'd be able to approach a 95% survival rate.

Ramming the opponent with the front of your vehicle is quite instinctive, in some ways easier than aiming a cannon, much less a slower projectile. That's one better use for steel balls than shooting them out of an airgun.

To improve your survival rate, you just need to add a ram that is tougher than the aircraft you're ramming. It's not hard - most airplanes are built out of relatively fragile materials, like thin aluminum skins, or outright canvas and wood in the 1920s. Just fitting a strong keel, like on a flying boat, will greatly improve your chances in a collision.

A better dedicated ram can be simply a hardened steel pole, which can even be made jettisonable. It will wreck any airplane it collides with, and hopefully you can detach it if it's bent or stuck. There's going to be extra weight, but the impact on aerodynamics is quite small.

In Antiquity, ships' main weapon was rams. They must've read this. Arrows weren't good enough to finish the fight, and only with rifled guns did ramming tactics go away entirely. You're going to have the same issue as ships, but much worse, in the air without guns.

Answer 2

Flechettes: a real WWI-era anti-infantry weapon.

I'm surprised that no one has brought them up. As KerrAvon2055's current top answer notes notes,

If any other weapons had been effective, they would have been used.

During WWI, another weapon was effective and was used, in active combat, by the French, and later, by the German and British forces (so they were at least effective enough to copy). These were flechettes, five-inch metal rods, sharpened at one end, and airdropped in bundles over infantry.

Cheap, easy to produce, silent, smokeless, and viciously lethal.

They punched through infantry helmets as readily as they did through trees.

The Germans, when copying the French flechettes, even paired them with an engraved taunt:

"Invention Français, Fabrication Allemande", or "French invention, German made."

I don't know of any instances of the flechettes being used against enemy aircraft, unfortunately, but it doesn't seem impossible to me that they could be used that way, if not as reliably or practically as machine guns.

Answer 3

No

Let us take a brief look at the development of military aviation in WWI. First, aircraft on both/all sides were unarmed and waved to each other cheerfully as they carried out reconaissance and artillery observation missions. Then they started carrying pistols and shooting at each other, then rifles, to no effect. Finally, they started carrying machineguns, which was the point at which the first air-to-air casualties were inflicted. In other words, lots of projectiles needed to be sprayed in order for some flight-critical hits to be achieved, single-shot or semi-automatic weapons were completely ineffective on a relatively fast-moving but unstable firing platform shooting at a fast-moving target.

Subsequent developments were adding more machineguns - in both fixed mounts and turrets - and eventually crossing the fuzzy line from machineguns to cannons during WWII. However, until guided air-to-air missiles were introduced, the intentional non-suicidal casualties were caused by very fast-moving pieces of lead. (In WWI especially there was a non-trivial number of losses resulting from head-to-head engagements where neither aircraft broke off and both were destroyed in the subsequent collision, but I am assuming that swapping aircraft one-for-one by ramming is not considered a viable weapons system.)

This is not to say that there were no other causes of aircraft losses - there definitely were aircraft "shot down" by running into ejected cartridge cases which tore the flimsy fabric or damaged tensioning wires sufficiently to cause catastrophic damage. With the number of aircraft flying around each other at ridiculously short ranges from each other in the latter stages of WWI there were all kinds of weird accidents, but nothing that could be adapted to reliably knock down another aircraft.

Addressing a few of the weapon systems suggested, please remember that the aircraft of the 1920s were still very flimsy, mechanically unreliable and limited in their payload by the standards of even two decades later, though the wood and fabric had been somewhat replaced with metal.

• Crossbows or anything with a spring - no, the "muzzle velocity" is far too low to be effective. Crossbow bolts are also surprisingly unstable after even a relatively short range - they slow down quite quickly and then are not aerodynamically stable. Further, the motor to re-cock a powerful crossbow quickly will be a significant weight penalty - there is no such thing as a "plausible" Van Hellsing full-auto crossbow. The closest thing would be...
• Air rifle / air machinegun - air rifles can be as powerful as some firearms, but a seriously heavy mechanism would be required to create a powerful air rifle that could fire at machinegun rates. Not completely impossible - I think - but mechanically it would be much more complex and significantly heavier than a conventional machinegun.
• Air-to-air unguided rockets - please provide a link to any documented occasion where these have been used successfully, outside of a Hollywood movie or TV series. (Airwolf, I'm looking at you! I'm not sure if You Only Live Twice counts as a Hollywoood movie, but you get the idea.) These have all the disadvantages of low rate-of-fire firearms plus low velocity compared to firearms plus a huge weight-per-shot - their only advantage is that they give a spectactularly dramatic kill on a computer monitor or TV screen.

The best argument I can give you is that, despite the number of bullets fired per aircraft destroyed being enormous, guns and cannons were the only effective air-to-air weapons available until guided missiles came along. If any other weapons had been effective, they would have been used.

Answer 4

Trained birds of prey

Hawks and eagles can reach speeds faster than WW1 era aircraft, especially when diving from a higher altitude.

The birds could be trained to either attack the pilot directly, or to carry incendiary bombs and drop them on the plane. They would have superior agility compared to the airplanes of the time, making evasive actions difficult.

Answer 5

Nets and Cables

You would only get one to a few "shots", but large steel-wire nets would be effective against most pre-1930 aircraft.

The net is carried in a pod under the fuselage or wings; practical limit seems likely to be five pods for an aircraft small enough to be considered for attacking air-to-air.

When released, a sequenced set of catches let paddle-like "wings" on the trailing edge of the net pull it out of the pod and spread it, and additional "wings" on the leading edge, pulling the opposite direction, would keep it spread as it falls (the fall wouldn't be perfect, but doesn't really need to be). The tactic would be to fly close over the enemy and release a net from above and ahead, with the intent that the spreading net would foul the propeller or damage the fabric on flying surfaces, forcing the aircraft down (if not damaging it so much it broke up).

IMO, this would be the kind of thing only invented by folks who didn't have practical air-to-air gunnery. It would be more effective against airships, especially if also equipped with flares scattered over the net surface and hooks to punch through the airship's envelope and ballonets and allow igniting the hydrogen. The flares and hooks would give some increase in effectiveness against airplanes, as well, so likely would be on all or nearly all nets (there might be a tactical advantage for "clean" nets in some situations).

A possible variant of this would be a bolas-like contraption, a long wire with weights on the ends (or three wires connected at a center with three weights); this would tumble as it fell and be very difficult for the target to evade because it would be quite hard to see. If it strikes, it would wrap around wings or fuselage and constrict, possibly hard enough to tear through the frame inside the skin, or it would foul the propeller as a net would.

Answer 6

This might constitute as a frame challenge:

Firearms have a plethora of advantages over their alternatives. That is why we use firearms so extensively.

A plane with 1920's technology might be a disaster with many of the alternatives. They are either too heavy, or space requirements make the plane clumsy and thus vulnerable, or they are so slow (firing rate and projectile velocity) that they are downright useless in an aircraft. Or, they are just ineffective, lacking firepower.

This effectively rewrites the rules of aerial combat. The planes cannot be utilized like the planes of WWI in our world, and the dangers they face are also different. The weapons function differently, advantages and disadvantages are different, the countermeasures are different, requiring different counter-countermeasures, etc. Replacing firearms with something else is only the first step.

But, how the battle is changed? That is entirely another question, and the answer depends on the evolution path of the weaponry.

Answer 7

Airguns and proximity explosives

Airguns might seem like reskinned guns, but there is probably a good reason for them not to habe been used. I haven’t checked the particulars, but a quick guess is that they have several weaknesses. My guesses are that they are less reliable, less powerful, less quick to fire and more prone to damaging the aircraft.

You need to pressurise each container that will fire a bullet. This takes time and power from the engine. You might have enough gas, but you need to push it forcefully into the container to work. This costs extra power for the engine, which should be used for flight.

Power will be an issue. You can only pressurise a container so much before it'll reach it's max. The more powerful you try to make your shots, the more heavy and dangerous your pressurised cartridges will be. If they explode your plane won't be happy.

Quickly pressurising and depressurising a tank is also not recommended. I can imagine few use cases that are worse for the longevity of a pressure tank. It's not that there aren't use cases in the real world where you quickly pressurise and depressurise a tank, but here you're pushing everything yo the maximum.

Your planes will fire more slowly to accommodate all this, with lower velocity. This will make your guns more reliable and less prone to self destruct, but lose on power.

Proximity explosives

Losing power of your shots and less shots per minute will definitely not do well in dogfights. To compensate you make the ammo more dangerous with proximity explosives.

Proximity explosives weren't around in 1920, but your time line is different anyway. Necessity breeds ingenuity, so the lower lethality can spark interest in the field of proximity explosives.

The idea behind it is simple. You use any signal, like acoustic/optical/magnetic/radio, to detect distance to a plane. When a certain threshold is reached the payload is detonated. To prevent activation before it's time or the power source is spent before time you use the rifling of a bullet in your favour. When spinning fast enough things inside are flung against the bullet walls, which opens up the middle or bridges electronics for example. Thus you have a more dangerous ammo that explodes when close to an (enemy) plane.

Do note that this ammo is more expensive and difficult to make, making ammo more precious than it already is.

How it will look

Planes will zoom through the sky as they always did, dogfighting in the sky. But instead of spraying the air with bullets in the hopes to hit your opponent you'll fire more slowly and sparingly. You don't want to stress the pressure cylinders too much or waste too much of your precious ammo. Only when more certain your rounds get close you'll fire a volley of a few rounds, hoping their detonation will render the enemy as a 'neutral' party.

Higher skilled dogfighters can more quickly get a kill, have less stress on the gas tanks and use much less ammo.

Answer 8

I think in these cases, it is worth working out what is different about your world

Is some part of the physics or tech different? If you have, through some weird quirk, naturally occuring room temperature superconductors and extremely high capacity batteries, you might go with rail or coil guns, or the particle beam cannons proposed by Nikola Tesla

Otherwise, you could go with gas guns - not far off a petrol engine in operation. You spray an aerosolized mix of fuel into a tube, ignite it, and, instead of the piston, you have your projectile at the end. Can be made nice and fast firing.

Answer 9

Crossbow bolts big weakness is size. You can't carry as many as you can bullets.

Perhaps an airgun firing an exploding canister of ball bearings or similar? If it was automatic you'd basically be able to pepper quite a large area like a shotgun does. If it explodes on impact it should do some damage. And used on ground troops it would do damage just hitting the ground between them.

Answer 10

A combat kite

A kite-like structure is located behind the pilot, hidden under a moveable panel. When the pilot engages in a counter course attack vs his adversary, he should aim his plane below the enemy, then pull the trigger on the kite. The structure jumps off the plane, quickly gaining height due to being pulled by inertia and wind, and pulls out a string of steel wire, probably with some weight attached at the other end, that was initially folded in the same compartment. The enemy plane collides with this surprise, at worst the wire gets the propeller entangled and locks up the engine, at best it gets wound around a wing, possibly tearing it in parts due to collision force and the potential tug of the kite. Having had its lifting capability impaired, the enemy plane would likely have to take a forced landing, or if the damage would be enough, will just crash. These things can be packed in numbers aboard a single plane, taking about 10 kg weight apiece, and a special hatch like a bomb hatch could be use to deploy them in combat. (Better have airplanes with double tail structure while using these, as a locked wire could damage your own plane if malfunctioned at launch. And the opponent could well pepper your own plane with flechettes resulting in double crash.)

Answer 11

Therac gave you some excellent reasons why airguns, crossbows and rockets are problematic. In general gunpowder projectiles are fast enough and efficient enough to be effective, most others really aren't. If that is the case, then tactics would likely change.

If you can not shoot forward with any real capability, then backward and down are your only options left. Any kind of rear-projected or gravity release flak (flechettes, nets, etc., as mentioned above), would be your most effective weapons. Fighter tactics would then be a race to maintain both height and position.

Gravity drop weapons are certainly harder to aim and less effective, but height is an asset that is hard to beat. The only way to do so is to climb, slowing down your groundspeed and making yourself easier to hit. The most effective weapons would be rear-release when you can be closer to the opponent and their speed works to smash them in to your projectiles.

I think you'd see lots of shot-like weapons. Fuel/air aerated explosive or napalm-like sprayable incendiary liquid. Incendiary gas or liquid may be skirting the chemical line, but the actual material is not dangerous, it is only dangerous if you ignite it. Something as simple as a length of chain could do incredible damage to a light wood, wire and fabric aeroplane. A handful of razors or even just a stack of sheet metal strips about 2 inches by 1 inch and a sixteenth of an inch thick could make a lot of trouble when hit going over 70mph.

Your planes would need to therefore get in front fast and stay there. Your fighters should be optimized for speed. Maneuverability doesn't matter as much as getting out of the way and getting in front, so thinner, more aerodynamic bodies, more cowling and less efficient wings (which reduce drag) would be important. 'Dogfights' would consist of command and control boxing in a number of enemy fighters with circular patrols and passes until 'bombers' can be brought in range. 'Bombers' would need to ascend quickly, so they'd need bigger wings and slower speed, but they should be able to blanket an entire area with chaff and flak, making operation in the area for anyone impossible.

There would likely be a lot of collisions with 'friendly' ordnance. Once it is released, it is dangerous to everyone.

Answer 12

In the James Bond movie "You Only Live Twice", the gyrocopter "Little Nellie" dropped parachute-borne bomblets above and in front of enemy helicopters, which detonated on contact with their fast-spinning rotors. Contact with a fixed wing aircraft's propeller or induction into a turbine engine would have worked as well.

https://www.youtube.com/watch?v=xFozWDLne7c&t=3m7s

The parachute guidance mechanism and trap-door box deployment are light and do not take up much space. A pilot could even pour them out the side of the plane from a bag, if they are sure not to strike any portion of that aircraft. No other weight or volume is consumed in bringing the weapon to the target, although obviously aim is greatly limited and consequently dogfights consist of trying to get directly in front of and above the enemy.