Can flak or some other method be used to detonate WWI-style artillery shells mid-air?

Question

I'm working on a steampunk-inspired low-fantasy setting where combat is primarily conducted via WWI-style artillery. Airships are employed extensively in ship-to-ship and ship-to-ground warfare, and are countered by fixed ground batteries that are more powerful and longer range than those employed on airships. (Airship weight problems are not in scope here.) These ground batteries cannot move and must be connected to centralized power stations. Infantry are used to disable and capture ground positions, including disabling these batteries, which are usually some distance from the area that they are meant to defend.

This means that if a city is under attack and its defensive batteries are destroyed or disabled, the attacking fleet has effectively won, since aerial bombardment could presumably flatten a city once the fleet is in range. I was originally going to introduce mages that work effectively as sci-fi bubble shield generators, but that solution feels a little too contrived and tailored to this specific situation. My current idea is to have cities defended by short-range flak towers, which will attempt to detonate shells mid-air before they reach their target. Is this a feasible approach to countering high-altitude mobile artillery, and are there any other counters that could be possible with Industrial Revolution–WWI technology?

Answer 1

Interception of large high velocity artillery shells would require;

1. The existence of exceptionally sensitive Radar or Ladar detection systems In real life artillery fire can be detected by ground based radar units with enough accuracy that the trajectory of the shells can be calculated and then back tracked to the firing positions allowing an opponent to call in 'counter batter fire' on the guns which fired the shells. But what your requiring is at least 10 orders of magnitude more difficult.

2. Advanced high speed calculating machines capable of readings from the detectors, in real time and processing it (again in real time) to determine an interception point. These machines in turn would need accurate, real time data on local atmospheric conditions at the time of firing including e.g air pressure, temperature, wind velocity & direction etc.

3. High speed/accurate clocks and precise maps (to assist in making the relevant calculations)

4. Automated gun systems linked to and directly controlled by the calculating machines

In short your looking for a super hyped up version of something like Israel's 'Iron Dome' system or some kind of Phalanx CIWS. Which is, I suppose 'doable' in a Steam Punk setting but really? It's still veering more into conventional Hard SF.

On the plus side, as is the case with the two systems named above your guns don't have to be long ranged. The idea is to hit incoming shells before they impact so rapid, accurate, short range fire is the key not hits at long range. (Lasers if you have them?)

The issue you have though (if you insist on a WW1 setting) is that in real life there were no WW1 or even WW2 technological systems capable of identifying artillery shells on the fly and plotting intercept courses. Artillery fire control calculators were bulky electrical/mechanical devices and that initially relied on the Mark 1 eyeball for targeting information then later during WW2 on radar. No system then in existence was capable of plotting an intercept for an incoming artillery shell in real time.

Answer 2

Frame Challenge -- Blimps are Squishy

You want to balance Blimp vs City combat. You are worried the blimps are too powerful. The solution is to realise that blimps are also hyper vulnerable bags of air.

It is much easier to make a hole in a big bag of air than to make a hole in a ground-based gun emplacement.

The blimp's only defense is being high above the ground. This protects it from smaller guns. On the other hand it can drop bombs from as high as it needs since they fall due to gravity.

To balance the combat simply impose a flight ceiling to the blimps. If they fly too high they will be blown around by the weather or they cannot aim their bombs correctly. This is WW1-era so the bombs are unguided.

The best thing about this solution is you do not need to decide the exact ceiling. Too high makes the blimp invincible. Too low gets the blimp snagged on radio antennae and goat horns. Somewhere in between lies the ideal height for your plot. Purposefully leave the details unexplained.

With the blimps a safe 2000ft or so, it is much easier to shoot them down. You don't need big mortar emplacements. You just need something one stage up from a soldier's rifle. Think a Vickers but built as a big rifle rather than a big machine gun.

Those things can easily be moved around by hand. Heck, even a team of riflemen can have reasonable success with sustained fire at a blimp.

Answer 3

Short answer: no.

But there are a few other ways to spin this, especially if you look towards reality.

Airships didn't play the role you envision them for a few reasons:

• They are slow. A defender has lots of time to prepare.
• Low service ceiling

WW1 means no pressurised hulls, which imposes a pretty hard limit on the service ceiling. Also, the higher you get, the lower the lighter-than-air lift. All WW1 airships I could find, have a service ceiling <3000m, most <1000m. That makes them vulnerable to a lot of weapons that couldn't hit a plane.

• They are huge and thus easy to hit
• They are literally air balloons filled with explosive gas, so one hit can take them down.
• They can't carry a lot of bomb weight (max I could find for WW1 was around 300kg)

Initially, the airship was considered a very dangerous bombing weapon. But soon the men in charge noticed, that they were to easy and soft targets for frontline warfare.

So how can you use this in your setting?

First, how to make airships effective?

• Use lots of (possibly leash-guided) decoy ships to draw fire away from the real ships.
• airships should fly their combat missions as close to the service ceiling as possible (even if the crew might occasionally pass out). This will limit their payload, so if the skies are safe, they can fly lower and carry more.
• Camouflage the airship. Maybe use dazzle paint?

How to counter this?

• FLAKs can easily shoot down airships. I randomly googled WW1 FLAKs and found some with a vertical range of almost 7km, which is more than double what the airships can fly to.
• Counter balloons with balloons: the city people could "drop" small hydrogen balloons with proximity trigger shrapnel grenades, which would float up and try to explode when they get close to the airship. These would need to be brought out in carpet style, but that should be possible.

Bonus: Why do lighter-than-air vehicles fly so low?

The main issue is that a lighter-than-air vehicle needs to be actually lighter (meaning less dense) than the surrounding air to fly. Air density decreases the farther up you get. That means, if you want to fly higher, the aircraft needs to be less dense. Less dense means less weapons, lighter (less stable) structure and overall less payload.

Combine that with the very limited choice of low-density-high-strength work materials available during WW1 and you end up with airships that can either fly low and actually carry something to make them worth being used, or fly high and empty.

Also, if you fly higher, you also need a pressurized cabin for the crew. This adds a lot of weight and wasn't too feasible in WW1 era at all.

Bonus: Why are armoured lighter-than-air vehicles not a thing?

The oldest tank I could find used 6mm steel armor. 6mm is not a lot. It can stop regular gunfire, but it won't work wonders for bigger guns or even explosive/armour piercing rounds. Also, an airship has large, almost unsupported surfaces. A round hitting this armour will create shockwaves and all in all 6mm of steel armour will probably not help much. But, for argument's sake, let's say it's good enough.

Also, let's say, our aircraft should be able to fly at 3000m height. That's about as high as the best lighter-than-air aircraft in WW1.

Also, let's assume, the crew, payload, engines, fuel, internal structure and everything else weighs nothing.

This means, our aircraft would have to have 15.7 million m³ of volume. If the ship has the same radius of the massive Hindenburg, it would have to be 11.7 km long.

If it's supposed to fly at 7000m height, the volume would be 57.5 million m³ of volume, and the length would be 42.7 km. That's roughly the diameter of London.

Edit: all the calculations are for the perfect shape to reduce surface area while increasing volume: a sphere. So if you actually want to build this in the shape of an airship, it's going to be much longer than the above mentioned numbers.

Answer 4

Barrage balloons

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

The problem with flak is that the area of denial is so fleeting - you have to catch the shell as it goes through the sphere of flak.

Your world has airship tech. Use that. Barrage balloons were used to hang cables down and prevent aircraft from approaching. Nets of cables could intercept some shells. Between the cables that come with the ballons are a web of ad hoc planks and scrap wood (wood because it is light) tied along ropes (also light) in hopes of increasing the area of denial provided by the balloon. Some of the wood is unmodified - chairs, church pews, wagon wheels, tree limbs.

For the hanging cables there could be very high balloons with long cables. If this is an anime there needs to be a scene where an enemy airship gets fouled in the cables. Defenders climb up the cables and commandeer the airship, turning its air artillery around and firing on other airships.

Balloons themselves could be used as a flying shield. Surfaces facing the expected approach of incoming shells will be armored and shells will spend themselves against the aircraft.

For armored balloons I like the idea of many small balloons rather than a few large airships. For one if a hit balloon is destroyed it is less of a loss. Possibly lightweight armored balloons will be thrown sideways but not ruptured by the shell.

Reactive armor was not developed until after WW2 but I think the needed tech was available WW1 - it is essentially a counterexplosion triggered by the impact of a shell. One could have balloons with armor so light that the shell would pass through it, but the balloon provides a counterexplosion that diverts the shell (and destroys the balloon). Those would be fun for a fiction because maybe later in the story some of those reactive armor balloons are used for other purposes.

Answer 5

With WW1 tech, probably not.

you would need highly sensitive detection equipment to detect incoming shells, like radar, then you would likely need a computer to calculate its speed and trajectory and all that good stuff, then you would need a very accurate weapon that is likely not controlled by a person but rather by that computer. And you would probably need proximity fuses for your shells which were not invented until ww2. Without them, you need an insane degree of accuracy.

Hypothetically though, maybe?

If the incoming artillery shells were extremely slow, like WW1 aircraft speed, and extremely bright, like from some kind of artillery shell tracer or the shells being highly reflective, and the flak dense enough, you could potentially spot and shoot down a shell. if the shells are moving at actual artillery speed, then there isn't any way you're going to shoot it down. Not only that, but you would likely need proximity fuses for your flak to shoot down the shells. Without them, you would need a direct hit on the shell, which a bullet hitting a larger bullet potentially hundreds of feet away while everything is moving at high speeds is very unlikely. But unfortunately for the defenders, proximity fuses were only really invented in WW2.

What could work

So its unlikely we can just shoot down incoming artillery (even if we could they could always just keep firing shells at us). Well, bring down the airships. We probably have aircraft available to us, like biplanes. We could bring the fight to the airships. They can probably just send another at us, but we can buy ourselves some time if we keep downing them. We could bring mobile artillery/AA weapons. We sally out of our cities and fight them before theyre in range of the city. Even if large caliber artillery is needed to consistently kill them, we can at least harass them or disable unarmored pieces of their ship like propellers and lighter armored crew areas.

we could even board them, which i think would make for great storytelling. We get our guys on their airship, either by having them drop from planes, or some ground based launch tech (its steampunk low-fantasy, im sure we can come up with something) with rifles, explosives, melee weapons, even flamethrowers (they would do very well in the close quarters of a ship). I doubt the enemy has any marines on their airships and even if they do, it would not take long for saboteurs to do plenty of damage. They would've either blasted huge chunks in your ship, set everything on fire, or just slaughtered tons of defenseless crewmen.

Answer 6

For such close-in interception of artillery I would also have to wonder at the usefulness even if you succeed. Your counter-fire isn't going to remove the danger of the incoming round, only lessen it somewhat, all that material is still going to hit your position (assuming the trajectory was accurate to begin with).

Answer 7

What you ask directly is impossible, but also not needed for your scenario

You want a defense for your cities. You mention ground emplacements, which also more than suffice, because the ground-based guns can outsize and therefore outrange airships considerably.

WW1 style airships have a very low service height, so the height-based height advantage is negligible when you consider what size of gun you can have on an airship in relevant numbers (plus ammunition) in regards to weight.

This means that airships simply cannot go near any city which had some time to prepare a defense cities near any dangerous border would likely have permanent gun emplacements, and all others have rail-based prepared fortifications, with anti-airship guns on standby somewhere in the country, to be ready within the hour if an enemy approach is spotted (don't forget that airships are slow as well). Once in place these ground-defenses could force enemy airships to keep multiple kilometers away, because one hit on an airship is enough to bring it down, while ground based bunker systems can easily take a hit or two.

Tl:dr: there is no need to intercept airship shells because they won't dare to get into range