How to correct aim in aerial airship combat?

Question

Report! Correct aim 2-20 fore, figure in enemy speed at negative 15 knots relative decelerating. Ready? Fire in Sequence on my mark... MARK!

LCDR Arnold Dering, Commander of the "X"-Turret, GKS-B-RW41 "Adamanta"

---

NOTICE: I am looking for a solution within the confines given in the question. If your answer does not work without introducing anything to the world (e.g. super precise lenses, magical hotstones, etc.) please take the time to weigh up the pros & cons of whatever you introduce.

---

In my mind-bogglingly breathtaking conworld heavily armoured airships majestically float through the skies with help of a science-defying, yet well thought-through lighter-than-anything material¹.

Above the skies they duke it out between each other armed with machine guns, flak, artillery. Machine gun & flak fire saturating patterns & methods against flying enemies are well enough explored and used in our world. What I would like though, is to have the larger airships not only use their artillery to reduce bunkers and buildings to rubble, but fire shells at each other - in the air!

The only issue I see is a way to properly report misses in order to adjust aim for the next salvo. If they miss, the shell will simply hit something on the ground - potentially miles away from the target.

To solve this I was thinking about introducing a marker shell being fired until a promising bearing is achieved. This marker shell could either be something along the lines of traditional tracer bullets, or a self-detonating shell being primed to explode after a certain time (distance / speed).

In my understanding this would provide the spotter/targeter/aimer with a reference point - quite similar to the splash used by World-War navy gunners - being close enough to the target to be actually useful.

_{¹Here's a question about how to control altitude with this physics-defying figment of my imagination.}

---

Q: Are there any issues with the described technique(s)?

A good answer should address the following topics:

• What is the advantage/disadvantage of tracer shells over the detonating shells?
• What is the advantage/disadvantage of detonating shells over the tracer shells?
• If none of the techniques can work, why - what fact about aerial combat did I miss out on?

In addition it would be amazing if answers that explain why this does not work, to include a section proposing alternative solutions come close/to a similar result as what I am describing in the above prose.

---

Technology: The world is set technologically somewhere between the industrial revolution and the invention of internal-combustion-engines. There's been heavy development and optimizations regarding steam-driven-engines as there is, at least in parts of the world, little to no oil available.

Electricity is something fairly new and so far doesn't go further than being used for creating light aboard airships and being used for telegraphing (little to no electric infrastructure).

While oil is found and burned in other parts of the world, in this part of it the most commonly used fuels burned for heat are coal and peat. Additionally natural-gas, coal-water-slurry and fishoil are most commonly burned in lanterns to provide light.

---

Speeds: These Airships, most of the time, consist of two or more parallelly arranged lifting bodies with most of the mass of the ship hung between them, the center of mass being below the lifting bodies. This arrangement is intended to give them a sort of stability in the air similarly to a catamaran.

While some airships have multiple dedicated steam-engines, most of them feature central engine-rooms where work-power is diverted to engines, winches, etc. using gear-assemblies, drive-belts, drive-shafts, air compressors, ...

Under normal weather conditions military airships rate average speeds between 60-90kph. Military ships feature multiple, often pivotable, engine-pods along their hulls, allowing the application of thrust in almost any direction; the bigger the ship, the more pods naturally. In general speeds, etc. are based on WW1 & Interwar-Period craft, such as the Schütte-Lanz Airships.

---

Tactics: There are different classes of ships that refer to different sizes, armaments and tasks of the ship, the largest of these reaching widths of up to 160m and lengths of up to 400m. Aspect ratios vary from smaller ships @7:2 to larger ships @5:3.

Armament and engagement-tactics are loosely based on WW1/WW2 naval combat. That is cruisers/battleships would primarily fire heavy shells over vast distances (mostly for land bombardment), while smaller/medium ships would feature lighter weaponry to engage in ship-to-ship fighting (e.g. destroyers).

In addition almost any ship down to corvette-size carries a compliment of spotter/fighter/bomber biplanes. While a corvette would carry at most 1-2 planes, a destroyer would already carry a wing of 3-6 planes, a battleship half a squadron (~a dozen planes), up to carriers hauling multiple scores of plane (being basically huge flightdecks with underslung multi-story hangars).

Answer 1

What you are describing is more like the art of Rangefinding

This was a major research area in both World Wars. The main issue was battleships from WW1 onwards, because of the large ranges involved, had enormous difficulty judging distance. It was generally regarded that the British had the best Rangefinding techniques, but even so only 3% of fired shells actually hit their intended target.

As targets are far away from each other, there is no advantage to 'smoker' shells. Keep in mind at a distance of 30km or more, it takes a long time for a shell to ballistically reach its target, even several minutes. In this time the ship could move, wind factors could alter, and the tactical situation may change. Your 'marker' shells would be more the go to detect if there was a hit, although close observation from spotter towers may give you this data anyway.

In early (prior to WW1) battles Russian battleships were not successful against newer Japanese battleships. This was in part due to the technique of the Japanese firing a large salvo with each shell of a different range. This 'shotgun' technique allowed them to find the right range quicker, whereas the Russian ships would still firing one at a time. Other nations quickly adopted this, but with the advent of range finding computers, devices mounted on spotting towers (hence the many platforms in a typical Battleship) accuracy became greater from the first salvo anyway. Later, radar was the preferred method of range finding, combined with computers to increase accuracy. Artillery nowadays can be very accurate on the first firing.

In your world, airships however move in 3-dimensions. I would expect the following then:

• Spotter towers on your airship, with platforms extended as far 'wide' as possible, to try to increase the accuracy of your range finding system. Rangefinding devices mounted to the platforms, and data fed to a central command deck with tables/calculators to determine range.
• Shells to be fired more often and in multiple salvos. Unlike battleships though, your target could be a different altitude in addition to direction, so your shotgun approach would be to fire multiple shells in a grid / hexagonal fashion to maximise chances of a hit. All shells should be effective to give you the most advantage in the shortest time frame.
• There is a great advantage to height. The higher you are, the greater your effective range of shells. Therefore I would expect your airships as soon as detected would both try to rise as high as possible. Unlike battleships, as an airship captain lifting your airship is as good as a higher range gun, so airships over the top of you have a distinct advantage. I would imagine 'emergency blow orders' would be the first command that would be given.
• However at the end of the day, it may well be that your battleship airships give way to being carriers. This is because instead of range being measured in the tens of kilometres, with smaller, lighter, faster craft (such as mini-airships, gliders or planes) force can be projected over hundreds of kilometres - each with its own armament. This means a smaller faster craft can come in to close range, or at 'high altitude' and be equally if not more effective than a large heavy vessel. This happened in real-life, leading to the demise of the grand Battleship, which simply became bombing targets for more agile lighter craft.

Answer 2

Which you use depends on what you're firing.

If you're firing a machinegun (a "hose") then tracers just make sense: you can see where the line of what you're firing connects with what you're shooting at, how much you have to lead, how much up you have to fire, etc.

If you're firing a volley of single-shot things, then having them explode colorfully on fuzes at roughly the right distance gives you some great advantages: stuff that "misses" has a second chance to do damage from shrapnel; and you can see the pattern it paints around the target.

Tracers and rainbow-shells both help your foe locate you and return fire.

[Edit: it has been pointed out to me that there are tracers which only shine backwards towards the firer... which seems like it would reduce the problem, but not eliminate it unless every round hits, since they'd see the ones that missed and went past. If every round hits, you don't need tracer rounds anyway.]

Say you always fire a rainbow of shells. The foe, on observing a red explosion to their port and an orange explosion closer but still to the port, will know that you are astern of them. Even if you don't fire in color, a foe seeing an explosion to port and then a later one to the starboard will know you are to port.

You could stagger your volley deliberately, to make them think you're in a different direction, but that would also reduce the accuracy of your information from the volley.

Regardless, the shotgun volley lets you tell where in that volley the foe was, and to focus your fire around that.

But once you've found the right place to shoot at by the outcome of your volley, you want a way to continue range-finding as each ship maneuvers around each other.

You need a computer, but you don't have even the most basic electronics.

If we are to go by history, you have two options: gears/cams, and pigeons.

Cams and gears are pretty freaking incredible.

Back in WWII, we couldn't carry computers around in planes. Computers were the size of buildings, and needed a fleet of engineers just to keep them running and to fix all the bugs.

Instead they used mechanical systems. The resource you want to read on this -- and I suspect that, given the work you've put into building your world already, you actually will read this, once you get how important it is to your setting -- is Ordnance Pamphlet 1140: Basic Fire Control Systems, Section 2, which you can find at: https://maritime.org/doc/op1140/

Think the differential gear in your car was just a thing that let the wheels rotate at different speeds? No, it's a computing system that does addition and subtraction! And similar things let you multiply, divide, differentiate, calculate trig functions, and more!

This is something that steampunk worldbuilders typically don't get. Cams and cogs aren't decoration, any more than chips are decoration for chip-punk. They are essential parts of mechanisms. Inputs and outputs are hand-cranks, levers, switches, and probably even a targeting reticule that drives two axes which are integrated together. Line it up with the target to get X and Y, slide the range slider, merge with inputs from the wind-speed and direction sensors, the gyroscopes to predict rotational velocity in pitch, roll, and yaw, and then the velocity with which your targeting reticule moves as you track the foe in order to calculate their relative velocity and get a "lock"...

Which is where pigeons come in.

Because, sure, you've fired the thing in basically the right direction, but if your shell has vanes on the tail, it can direct its flight to actually hit the thing you fired it at.

But fitting even a mechanical computer into a shell, particularly one which could recognize a ship from any possible angle and target towards it... not possible. But you know what can do all that, and is light and portable? Pigeons.

So Project Pigeon was born:

One to three pigeons, trained by operant conditioning to recognize the target, were stationed in front of the screen; when they saw the target, they would peck at the screen with their beaks. As long as the target remained in the center of the screen, the screen would not move, but if the bomb began to go off track, the image would move towards the edge of the screen. The pigeons would follow the image, pecking at it, which would move the screen on its pivots.

From: http://www.historynet.com/top-secret-wwii-bat-and-bird-bomber-program.htm

the pigeons learned to rap out as many as four pecks a second for more than two minutes without a break, and would work feverishly to prevent the target image from moving off dead center.

[...] The pigeon had to peck correctly or he got no food at all. According to the report on these experiments: ‘There wasn’t a single washout in the entire class of 64. Every bird earned his wings with an A grade.’

[...] Target pistols were fired only a few inches from a bird’s head. The pigeons didn’t miss a peck, didn’t even look up. Other extremely loud noises were introduced. Again, the pigeons stayed at their task. Skinner also put the pigeons in a pressure chamber, setting the altitude at 10,000 feet. They were also whirled around in a centrifuge, put on pure oxygen and exposed to bright flashes, simulating shell bursts. High vibrations were also introduced, and the birds were subjected to massive G forces without harmful effects.

[While] pigeons were never used to bomb enemy targets, the test results show that they could have.

If electronics had not come along, organic control would likely have become the main way of making guided missiles.

TL;DR: As well as tracers (for guns) and fuzed detonation (for cannon), you may also want to look into cams, gears, and pigeons.

Answer 3

Tracers are nice for a visual image of your projectile but they rely on light, and are obviously more visible at night; fighting above the clouds in bright sunlight might also hinder this.

In order to keep effective artillery shells, I would reccommend using smoke trails as a form of tracer. Similar to the colored smoke you see stunt planes release at air shows.

I believe this would solve the visual element of what a tracer would provide; and as an added bonus the lingering smoke would provide an idea about air currents relative to the target as well.

Answer 4

You have two major options aside from tracers/smoke-trails. One is to build a human intuition for it. Leading an aircraft in flight in order to shoot it down is a skill that is ecan be obtained with sufficient practice. I imagine that if you practice with tracer/smoke rounds (to speed developing the intuition), you could then take your trained gunnery-officer onto a real battle field and he could do a fairly good job at getting near the enemy without tracers at all. The difference between having the tracers for training and not having them in battle could make for some interesting challenges for young gunnery-officers

The other option is to build a mechanical computation device to help you out. I imagine the use of one would go something like:

1. Estimate the distance to the target
2. Line up eyepiece number 1 with the craft
3. Wait five seconds
4. Line up eyepiece number 2 with the craft
5. Enter the elevation and azimuth of both eyepieces into a table, look up the distance, and read off the required azimuth/elevation for your guns.
6. The table would be valid for a fixed point in time from the readings, so communicate these to your crew and fire your guns.

Building such a device would not be hard, so long as trigonometry and parabolas are known mathematics (as they have been for hundreds of years now). One cool thing is that it uses the relative velocity between the craft - so it doesn't matter if both vehicles are moving, rotating or whatever, it will all get factored in with the same basic math. Similarly, so long as the relative timings between aim1-aim2 and aim2-shoot are consistent, the exact timing wouldn't be too important (though faster would be more better).

Tables may not be efficient with six entry points, so perhaps you could wire the eyepieces into a mechanical calculator of sorts. I can forsee some fun-shaped cams containing the balistics information.

I can imagine you could build such a system directly into a gun-turret. You have one dial for the distance estimate, and then you line up the one marker, wait five seconds, line up the next marker, and some mechanics places a third marker where to shoot. If you have two-man gunner teams, and some way to get a round into a moving breech, one man could reload while the other aims. Aim, aim, shoot. Aim, aim, shoot.

Depending on the size of your vessels and the distances you are working at, and the accuracy of your measuring devices (stereo offset from the bow/stern of your craft) or your intel about the size of the enemies craft (measuring by relative angle from front to rear of there craft via lenses), you could potentially have a person who's duty it is to measure the distance to the enemy and inform all the crew members. Whether the information could reach the gunners in time for it to be useful is another question.

So what is the feasibility of building this mechanical aiming device? Yes it is possible. People built mechanical "differential analysers" and extremely complex mechanical computers during WW2. Here's one for calculating a ship's position, and really, this whole concept is just an extension of devices such as the Kerrison Predictor - during the wars, they had to try aim ground-based guns at high-flying bombers, which is virtually the same problem. Quote from wikipedia:

The [Kerrison] Predictor solved the problem by doing all of the calculations mechanically through a complex system of gears. Inputs to its calculations included wind speed, gravity, ballistics of the gun and the rounds it fired, angle to the target in azimuth and altitude, and a user-input estimated target speed. Some of these inputs were fed in by dials, which turned gearing inside the Predictor to calculate the range (from the change in angle and estimated speed) and direction of motion.

Here's a fun idea: lighter-than-air torpedos. I suppose they're actually called rockets, but if you can make them neutral buoyancy due to your handwavium, you could fit them with gyroscopic stabilisers [complete service manual], and point them on their way.

Answer 5

How to blast an airship

You must fire tracer rounds

In order to find range, an airship opens fire with tracer shells until a suitable range is detected. Tracer shells will burn brightly when fired. Each gunnery team has a crewmember whose job is the spotter. Their important job is to track the time it takes for the shell to cross the plane between the firing and target airship. Whether the shell passes in front of, or behind the target, that time is all that is needed.

A tracer round must be used; smoke or detonation is not an acceptable alternative. In WWI style naval gun battles, all ships in an inferior firing position will be actively emitting as much smoke as possible to obscure their own positions. A assume your airship battles will be the same. The only reason not to deploy smoke is if you are entering battle with overwhelming force. Smoke will make targeting very hard in the absence of any radar. For this reason, very bright tracers are crucial to being able to tell where your shots are landing.

Rangefinding with tracers

The time that the shell spends in the air, along with the angle of fire of the gun, along with the known muzzle velocity of the gun (assuming the cartridges are produced with such quality that the muzzle velocity is well known), are all you need to know to calculate the range of the tracer. The angle of fire of the gun must be known with respect to an absolute level. The airship will presumably have some roll (and possibly pitch and yaw, too) that will affect the firing of the guns. The absolute angle of the gun relative to the ground is what you need to know.

Let $\beta$ be the angle of the gun as fired, $v_c$ be the known muzzle velocity, and $t$ be the time in the air. Now let $\alpha$ be the angle between the firing vessel and the target vessel, and $d$ will be the distance we calculate. It will look like this:

First off, you can calculate the horizontal distance that the projectile traveled before it passed the target, simply, using

\begin{equation} d = v_ct\cos{\beta} \tag{1}\end{equation}

If he tracer passed in front of the target, then this distance is short; if it passed behind the target, then this distance is long. Adjust accordingly.

However, there is additional value in calculating the angle of engagement between you and the target. The equation for the height above reference of a projectile, a one dimensional distance, based on the initial elevation above reference, and the initial velocity (in the one, vertical, dimension only), is \begin{equation} d = \frac{gt - v_c\cos{\beta}}{\tan{\alpha}} \tag{2}\end{equation}

What did all this math get you?

You can now create a lookup table with the solution to these equations. Given $t$ and $\beta$ you can find out how far your shell traveled, and thus, how far away your target is. Each table of lookups will be for a certain cartridge or powder size (however your guns work), such that $v$ is constant for one table.

Equation (1) gives you a simple estimate of the distance at which your shot passed either in front of or behind your target. Equation (2) gives a further way to you a way to estimate what angle you should make your first few shots before you range in. This second equation also lets you cover expected changes in relative elevation, such as if your are climbing or descending relative to your target. You can measure $\alpha$ with a sextant or a similar piece of equipment. The lookup table will be used the same way, except it will be a three way lookup table with $\alpha$ included.

How do you range in on the target?

Alright, let us imagine that the airship has its guns mounted in a limited set of turrets, the way that an Iowa-class battleship has its nine guns arranged in three turrets. Each turret is going to fire tracer rounds at first, to get a range in on the target. As it is firing, the gunnery officer for that turret will note the times to target, elevation of the gun that fired the shot, type of cartridge involved, and approximate angle to the target.

Using all this information and the lookup tables, for each shot you can develop two separate estimates of distance to target. You write these distances on a board in front of you in chalk or grease pencil or something appropriate, in two colors, noting near and far. With use of the targeting board, you will quickly be able to use the multiple guns of the turret to range in on the target.

Once you are close, you switch to firing real, explosive rounds, with perhaps every fifth shot being a tracer to ensure you are on target. With all the smoke, and explosions and other ships firing on your target, this won't be easy. But with gun crew training, a competent crew should be able to keep on target during a pitched battle in the skies.

Answer 6

Problems with exploding marker shells:

• You need a flight time estimate to make the shell detonate at the right point. Where does it come from? If you have distance and speed with sufficient precision to set the fuse, why do you need ranging shots?
• You might or might not have reliable time fuses. Also, they would have to be set before the shell is loaded, which could be a lengthy process for a big gun.

Advantages of exploding marker shells:

• You can make them explode in separate colors for separate turrets, so each turret can tell theirs from the others.

Problems of tracer shells:

• They work best for a relatively flat trajectory. On a ballistic arc the tracer might no longer point towards the observer.
• They affect the ballistics. The destructive shells might have a different trajectory.

Advantages of tracer shells:

• Simply make all of your shells tracers, that way the first shell to hit already does damage. With an airship, even an armored one, that first hit could be decisive.

General problem:

Your airships maneuver in three dimensions, and they will probably be faster than watercraft. That could make any long-range, indirect fire artillery questionable. The best WWII fighter pilots had the nerve to close in with the enemy and to fire a devastating burst. Hitting at more than a few hundred yards was almost impossible.

Even if you extend the ranges to a mile or two, the big guns would have to be fired in a very flat trajectory to hit.

Answer 7

How advanced are your computers? Firing guns against targets at different altitudes is a lot trickier than just trying to hit something at the same level. The US artillery had a real problem fighting in Italy, as the range tables weren't very useful when the artillery and target were at different heights.

Correcting fire is not going to work well, as the airships are apparently reasonably fast and can move in three dimensions. The shells will have to be tracked, and a straddle would be some going over the target and some going under. Tracer rounds will not be all that useful if they have different ballistics than the real ammo. If you can put some sort of tracer in the base of the shells, you can more easily tell if you've got a straddle. (Look, you've got lieutenant commanders commanding individual turrets. Those have to be some pretty big shells.)

One way to fight is to get sufficiently close that trajectories will be pretty much flat. At that point, we're looking at something pre-WWI, with individual turrets firing at will without any sort of central fire control. At that range, you can probably keep track of those huge shells with binoculars. It also keeps battles more compact, which is better if you're doing them visually. In WWII, for large ships, two miles was ridiculously close range. I know of one photograph from WWII with ships from both sides on it, and you can hardly see the Japanese.

Answer 8

Since you are already bending the rules a bit, perhaps use a smoke tracer round?

A smoke trail naturally blows away in the wind, but thats not what you'll be using it for. Like fireworks the smoke would have a color that changes over time. This allows the artillery battery to gauge the time it took before the shell flew by the enemy. An additional advantage is that the smoke left behind will blow passed the enemy and give a reference point to judge how close it went passed, combined with the color of the smoke trail you have a good idea of your shot, for a relative amount of "good" when talking about two fast moving ships in 3 dimensions in different light&weather conditions that judge distance based on something that literally moves with the wind.

Answer 9

Special forces aerial attack

I agree almost entirely with the answer by flox. For that reason I won't repeat the arguments.

I'll offer a different solution and that is human attack missions. I'm not talking about the Japanese Kamikaze pilots. That is a possibility but it's expensive in destroyed equipment and lost human life and also involves turning the large craft into an aircraft carrier.

Instead I propose gaining height on your opponent and launching one of your crack team of wing-suit flyers. The flyer carries a magnetic mine and when within suitable proximity, pulls the pin and lobs it at the enemy.

Then they peel off and head towards a land base where they can prepare for their next mission.

The following video shows just how precisely these wingsuits can be piloted.

Video of Wingsuit Flight Through 2 Meter Opening - Uli Emanuele https://youtu.be/-C_jPcUkVrM?t=84

I'll see what I can come up with for velocity and glide slope. I'll just say that they are such small, fast targets that they will be very hard to shoot down.

Answer 10

Wire-guided missile

The problems and explanations have been thoroughly explored as I type this. I won't repeat them. I'll offer a different solution.

Electrical wire guidance dates back to the 19th century https://en.wikipedia.org/wiki/Wire-guided_missile

A direct hit is not necessary. Aim high and the missile will fly over the enemy craft. Course adjustment happens in flight. It doesn't have to be electrical. The missile then falls and can be reeled in until a magnetic switch detects the enemy's hull at which time it explodes on the far side of the craft.

Passive missile with cable

As above but doesn't doesn't allow for course correction.

Answer 11

Use Math

...So, I know this is an old question, and you may not care anymore, but it caught my eye in the related questions panel of something else about airships.

Flox was right that this is a matter of rangefinding, but forgets the best possible method for it: Triangulation. This does not require fancy electronics. For this to work all you need is 2 spotters. I would suggest 1 at the bow and 1 at the stern sitting in predetermined places. Each spotter has a crosshair attached to a 2-dimensional swivel where each swivel is marked by a vertical & horizontal compass. Such technology was already common in the form of sextants.

When each spotter puts the target in his crosshairs he calls out the vertical and horizontal angles. Both spotters should have the same approximate vertical angle, meaning that your actual relevant data set is θY, θX1, and θX2. Well trained spotters will be able to not just aim at the target, but lead it appropriately as there will be a delay of several seconds between marking the shot and everything that goes into landing a hit.

Then you will have a 3rd person using look-up tables to make good use of the spotter's info. Let's call him the gunnery commander. He can use the numerical values to find an approximate firing solution. The lookup tables were of course compiled through months of meticulous calculations and testing prior to the battle and is specific the the distance between your spotters and the guns in question. But once the gunnery commander has looked it up, he then calls the angle and elevation the gunners need to fire at. With everything pre-calculated and the gunnery commander well trained, this should only take a couple of seconds at most. Once the firing solution is called out, all of your gunnery operators will swivel their cannons to the angle and elevation called out and fire. All of the shots should come pretty close to the target, but slight deviations of human error between gunners will make sure that not every shot hits the exact same spot; so, the shots will saturate the general area that the enemy ship is precalculated to be without having to fire a single tracer shot at all.

EXAMPLE:

Spotter 1: -17 mark 126.3

Spotter 2: 125.8

The gunnery commander standing next to a giant rolodex of charts upon hearing -17 flips his carts to those where the enemy elevation is determined to be -17 degrees. He then finds the row for 126.3 and then tracks to the column for 125.8. He then calls out the contents of the cell

Gunnery Commander: -14.3 mark 126.05!

...and everyone swivels their cannons to fire at that angle.

The reason this works is because it follows the law of sines which states that you can resolve all 3 angles and sides of a triangle knowing only 2 angles and 1 side. The known side here is the distance between the spotters and the 2 angles are θX1 and θX2. So, the average of these two angles gives you the angle to fire at, and the distance is determined by the average of the two remaining sides of the triangle that a mathematician calculated for your in advance. Also, the angle you need to fire at is determined by the velocity of your cannon which you should already know. The distance to target which you just determined, and the elevation to the target which is determined by θY. This means that your mathematician can skip showing his work and jump straight to telling your what elevation you need your cannon to fire at to intersect the target at that range.

All of the math required to do this within a fair degree of precision existed by the late 1700s; so, it should work within your setting.

Answer 12

"Marker shells" only work for consistent fire from a stable platform because only in a fixed position is your next shot sufficiently similar to make it worthwhile. So-called 'walking your shots' was firing from a comparatively more stable platform than airships, but even then they threw out a lot of ordinance for each actual hit. Artillery between airships renders the guess-and-test shooting functionally useless due to too much movement through the air and including the added difficulty of changing relative heights. The force of firing a shell (remember your Newtonian mechanics) is significant and will move the airship in addition to the continuing maneuvers of both combatants though 3 dimensions.

You would probably not 'fire in sequence' like some 18th century ship of the line as the recoil from each shot will make the next one even more wildly inaccurate. A far more plausible approach would be to give each gun independent operation - the officer waits until their shot is lined up as the aircraft keep moving relative to each other, then fires. Some coordination should be made to ensure two crews do not fire at roughly the same time and waste the second shot in a wild miss, but otherwise each gun should be independent. It would take electronic controls to get your firing of different cannons across different parts of the ship to be so precisely coordinated that they all fire at exactly the same moment (the slightest delay would throw the shot way off). Again, firing that shot will make the aircraft rotate around its center of mass in an somewhat unreliable way - air is simply not viscous enough to push against like that.

This could be somewhat mitigated with a recoilless gun - that would fit within a first world war level of technology (an approach historically used to try to get heavier ordinance on early aircraft both for the destructive effects of recoil on an airframe as well as avoiding the significant weight of a traditional artillery piece). While this does allow aircraft to use heavier guns, much of the power is spent out the back to balance the forces which cuts the effective range. If engagements are less than a kilometer you could even go with an technical setup of a modified machine gun geared to a recoilless gun or two. If the ammunition for the machine gun is calibrated to have the same ballistic profile of the big gun, you just need to walk the bullets until a spotter sees them hit, then fire the big gun. Even here you should be careful of using tracer rounds - it is difficult for the eye to perceive properly and even led to the US to stop using tracers on their bombers during WW2 as they apparently found it tricked gunners into consistently missing targets due to how the eye incorrectly perceived the shots (trust the mechanical sights, not intuitive eyes on distances and speeds your eyes did not evolve to judge well).

Flak is most useful for aircraft. These basically have timed fuses - the artillery crew sets a time on them, based on a best guess, so the shells explode in rough proximity to the aircraft. Actually expecting to score a direct hit is far too difficult.
In surface ships, a near miss can still be somewhat useful as the shell explodes when it hits the water, but you don't get that in aircraft - missing by just a hair is still a complete miss with no effect whatsoever unless you are firing explosive shells on timed fuses. A miss isn't even any good at telling you how close you got to hitting - it is too difficult to perceive how close a tiny fast moving object got near the target from so far away.

With heavy ordinance every shot needs to count - if nothing else the sheer weight of shells you must carry is far more of a concern for an airship than it would be for a surface vessel. Visual observation should be able to use parallax to get an effective range, levels should get them an inclination, and a little calculus (easily and quickly done on a mechanical calculator) should give them a good firing solution (what angle up/down and how long before the shot should reach the target). This would still only work with very slow airships at close range - at long distances and 3 degrees of freedom, it may be practically impossible to hit. It would probably be more efficient to ditch the heavy cannon and carry that weight in bombs to drop on ground targets, while relying on small arms to defend against any light attack aircraft getting close.

Answer 13

My first thought was some kind of tracer round. Coat the back of your shells with a slow-burning, brightly-colored smokeless substance and follow the gaze. The problem comes in using your airship for defense, as now you will be hitting whatever is on the ground if you miss. You'll hit them with a pretty-colored piece of metal, but it will still cause damage.

I would probably instead use some kind of timed-delay shell to determine the angle. You would then judge based on the position of the explosion, and adjust your next shot.

Modern jet fighters (what this has been likened to) use missiles that are designed to go off at a certain range/amount of time. They do it there to limit collateral damage, but minus the speeds they travel at it could be used to aim.

The way it would work is that your initial explosion to propel your shell also lights a fuse. These shells (common even in the 18th century) look a lot like the cartoon cherry bombs, and fit perfectly. The shape could be adjusted to whatever you want as well, provided you had the right chemicals on your fuse.

My question to you is: Why are you depending on singular heavy shells? Some kind of grape shot or chain shot is more viable, and the grape shot can be smaller enough to prevent collateral damage.

Answer 14

I can't believe that no one (almost three years ago) mentioned the method of verifying range for the main gun on a tank, originating shortly after WWI and continuing until computer tracking and aiming became a thing in the 1990s.

I mean the coaxial machine gun.

With American tanks, this was a Browning M2 (.50 caliber, same as mounted in aircraft and used as an infantry heavy machine gun), mounted on the turret and connected to the main gun tube elevation system so it was (after adjustment at armory) aimed to the exact same point as the main gun. This was aided by having specially made ammunition for the coaxial gun that had the same velocity and ballistic coefficient as the main gun's primary ammunition (usually High Explosive Anti-Tank in those days, since that was where precise aim was most needed).

With the tank dug in, there was significant advantage in getting a first shot direct hit on an enemy tank -- and this would be done by firing the coaxial machine gun. The tank commander had the trigger for this, and would call out his aiming, fire a round or a short burst, and either watch for impact or observe the tracer (both methods were used). Based on that, corrections would be made until the coaxial gun's bullets were striking the chosen target, then the main gun would fire.

When coaxial guns were introduced, the first shot hit rate for tank combat increased dramatically (before then, tanks were mostly useful as low-grade mobile artillery -- low-grade because they lacked both the range and the punch of true self-propelled artillery, only barely making up for it by being armored).