I don’t understand how they can accurately aim artillery. When they fire the whole machine moves a great deal and it would seem any calibration of its position would be lost.
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The time it takes for the shell to leave the barrel is a fraction of a fraction of a second. There can be things like barrel whip and a tiny little bit of the overall recoil that has an effect on the gun as the shell is travelling down the barrel, but those can be accounted for easily in targeting as they are always the same for every shot. The same principles apply to long-range small arms shooting as well.
You can get a pretty darn accurate shot if you have all of the environmental and gun variables accounted for.
– Muzzle velocity
– shell weight
– shell spin rate, because of the gyroscopic effect
– air temperature (and therefore density)
– wind direction
– wind speed
– altitudes of firing point and target
– barrel whip, maybe even barrel temperature
– distance to target, to account for spin and curvature of the earth
– probably a few more variables I don’t remember
They use ballistic calculators. The calculator factors weight of the projectile, elevation of the barrel, power of the propellant, gravity and Earth’s rotation.
The fact that you see the artillery piece (or vehicle) move violently is largely irrelevant, as the projectile has already left the barrel by that point. Lastly, they do not have to land on an exact “spot”, simply within a few meters is sufficient for their task.
Simple mathematics in terms of the normal aiming. As for calibration/zero after firing, the sight unit is routinely checked during firings. This will tell you if the angle or direction of the barrel has changed and allow you to correct for it.
Typically you will choose suitable ground and fire “bedding in” rounds much like a mortar to help compact dirt beneath the gun Something like a 105mm gun will still roll back slightly, but this is by design to mitigate recoil. A slight delineation is not significant in the context of indirect fires as they are not pin point accurate anyway.
I used to be in a mortar platoon. Before we arrive at a firebase an advance party comes in and surveys the area. (gps may have changed this somewhat since I’ve been out for a number of years) They leave stakes in the ground. We roll up and drop our mortar on a stake. There is another one a few hundred meters away. There is a sight on the mortar which has level bubbles, a direction scale in mills (1600 graduations instead of 360 degrees) and a small telescope with a reticle. A computer or a guy with mad math skills plots out the numbers required for direction and elevation and calls them out to the mortar crew. They dial in the direction and elevation into the sight and then have to turn handwheels to adjust the elevation and direction of the barrel to 1) have the far stake in the reticle of the sight and 2) have all the bubbles showing level. Once that is set the team calls “on” and waits for a command to fire. Mortars have a 3 man crew. The number 3 is in charge of prepping ammo and handing it to number 2. Number 2 drops the round into the barrel and then grabs the next. The number 1 is in charge of the dials and bubbles. After each shot the number 1 will glance down and make small adjustments if required due to the gun jumping or pounding itself down into the ground. As long as the bubbles are level and you are aimed at the stake the rounds will go to the same spot.
If you look at older cannons back in the Age of Sail or American Civil War days when there was no recoil mechanism, and the whole gun was on a single trail and would kick back into the ground, yes aiming and accuracy was very much something that varied greatly between shots. At sea and on land closing the range was the surest way of ensuring accurate fire. Another way was to mass fire. Gather a lot of guns and fire together at the same target. More guns, more likelihood of getting a hit.
Recoil mechanisms changed that. These are tubes filled with hydraulic fluid that are attached to the cannon. When the cannon fires, the cannon still recoils but now the force of the recoil is transmitted to the hydraulic tubes and whole gun carriage is not rocked back. In some guns (like the French rapid fire 75 mm field gun developed before WW1), the mechanism was smooth enough that a rapid accurate rate of fire was possible. But accuracy still largely depended on a human being aiming it.
At sea range finders (think binocular telescopes 20-40 feet across) could accurate determine ranges out to thousands of yards. Mechanical gear and cog calculators could factor in the ship’s speed, the target’s speed and the relative bearing and produce a set of aiming for the guns of the ship.
On land, the properties of weapon and better data (actual muzzle velocity data, consistent ammunition – shells of consistent weight, powder of consistent explosive force) allowed accurate indirect fire based purely on data and not having direct line of sight with the target. When several guns fired on the same target they could cover the area around the target point.
Even more data is now available to the gun crews: wind velocity, temperature, air density, humidity and variations experienced by the gun due barrel heating. These are fed into or available to calculators that rapidly produce elevation and aiming data. In the past, these were done using tables of pre-calculated results but today, computers are available for each battery and gun.
I was in the artillery for 6 years and can provide some accurate information on this. Your question has two parts and i will answer the second one first.
In order to retain calibration there are multiple parts. The first is that even through you see the gun move it is mostly held in place by a large circular piece of metal with spikes on it that the wheels roll up onto. The gun is then connected to this piece of metal to hold it generally in place whle still allowing it to turn. There are also “spades” on the end of the two long legs that counterbalance the barrel which stop the gun itself moving backwards so most of what you see move is really just the recoil mechanism of the barrel. After each shot there is also a thing that looks like a small telescope witha tiny scale inside it and the person responsible for aiming the gun points the guns aiming mechanism at it and this realigns the gun to the same bearing. This is initially setup using a director which is like a theodolite that a surveyor uses to tell the guns the direction they are pointing and to align all of them exacty the same.
For the first part everyone is taught how to do this with basic hand tools before they learn how to do it using the computer, rangefinder and GPS. There is a book that shows every mil of elevation the gun can point and how far it will go with each charge (with artillery, unlike a bullet, the cartridge case or charge bag is separate from the projectile). This means you can look at the book and say that since the target is 5km away you need to use charge 4 at an agle of 400 mils (the army uses mils not degrees for this stuff since it is more accurate) to reach that exact distance. There is also a group of slide rules that do the same thing (one for each charge).
To calculate the bearing the foward observer simply tries to identify the exact location on a map then sends those coordinates to the command post in the battery. The command post operators then work out the bearing the guns need to point using the position of the battery and the position they are trying to hit. It also varies slightly per gun since they are spread out and may also use different types of fire (linear, circular, converging, etc).
A million years ago I was a cannon crewman on the M-109 howitzer. An upgraded version is still in use today, but some of my information may be out of date. In my day there was a fire direction center (FDC) – a tracked vehicle – responsible for a battery of artillery, comprised of about 8-12 M-109’s and their support vehicles. A spotter with eyes on the target would call in a strike to the FDC
I never worked in the FDC but I believe they got coded map coordinates in those pre-GPS days. They would do the math to calculate deflection (left/right) and quadrant (up/down), along with the type of shell, fuse, and quantity of powder. They would relay that to the guns in the battery (one at a time) over a landline run between each gun and the FDC, and we would dial in those coordinates, pointing the barrel just where it needed to go.
Incidentally, you’re absolutely correct that if an artillery piece moves when being fired, the second shot will be wildly inaccurate. That’s a huge problem. Sometime in WW1 or maybe WW2 they developed a solution, to put the whole thing on springs. When the gun fires the springs absorb the recoil, but the base of the artillery piece doesn’t move, so all subsequent rounds will fly true. That’s super important because a lot of the time the first shell is just to dial things in.
Once the spotter sees where the first shell hit they call in an adjustment and we’d start blowing the target to smithereens. In the most standard shell configuration the “kill radius” was said to be 50 meters. That means that if you are within 50 meters of detonation you would be wounded too severely to continue fighting. To some extent the shrapnel wasn’t relevant – if you’re that close the percussion can break bones, burst eardrums, and cause traumatic brain injury. Artillery can kill you without so much as scratching you.
If anyone is interested, here are few more recollections. The shell was about 6″ in diameter, maybe 30″ long. There were several types of shell, high explosive, smoke, tear gas, and there was an illumination round that descended slowly with a parachute while burning brilliantly – that one could turn the darkest night so bright you’d throw a shadow. There is also a tactical nuclear round but I never had anything to do with that.
A fuse screwed into the top of the shell, and you could set it for airburst or you could time it to go off after it hit, like if you’re aiming for the inside of a building or bunker. The powder came in a separate container and was a bunch of cotton bags tied together, the more bags you included the further/higher the shell would fly. Every once in a while exhausted troops would add the bags to the breech but they’d forgotten to load the shell so only the powder would go off. That made for a truly spectacular flame thrower – the fire would splash all over the front of the gun and go maybe 20 yards. Really something to see! Well, I thought it was neat but then it never happened on my gun so I didn’t have to deal with the investigation.
Finnish mortar platoon leader here.
We did everything very simply manually in 1995 when I was there, no GPS, no computers to calculate. As far as I recall the procedures, here is a very simplified version of things:
You setup your mortars facing to the general direction you want to shoot. Then a compass direction is measured as accurately as you can, with map, 25 meter measure and some calculations – this way you will be able to place a stick (yes a real stick) in front of each mortar.You will place a pin to a map where your mortars are.
When ready to shoot, you will receive coordinates (from observer who sees the target, normally some guys in the front who can actually see enemy, now most likely a drone) where you are going to shoot, you place another pin there. With an artillery measure (calculation stick of sorts) you calculate the compass direction you are supposed to shoot, to SIMPLIFY, 000 north, 090 east, 180 south, 270 west. (The circle is divided in 0-6000 in reality). So lets say you get direction to shoot to 110. Lets say you placed your stick from mortars in direction 090 and this is where you are aiming. Since you want to shoot to 110, you turn your mortars 20 degrees to right. There is an aiming device on each mortar to accomplish this.
After you shoot first rounds out, a forward observer calls you and tells “you are 200m short, 100 meters left, please correct”, so you either lower your tubes to make grenade fly a bit higher, or you could add more gunpowder. Then you turn the tubes 2 degrees right (so some calculated amount), and shoot again. You receive “good hits, shoot full salvo”
very simplified explanation! there are lots of variables to it, weather, ammunition type, different powders, wind.. now they have computers to calculate the parameters but I’m sure they still teach manual calculations also
WW2 defenses for San Francisco are a great example of how this can be done. Along the coast south of the Golden Gate were a series of spotter stations. No guns, just a small bunker with a high-precison compass and a communication line.
Farther inland and out of sight of the ocean were artillery batteries. Through careful surveying and trigonometry the correlation between any location off the coast and the azimuth/angle settings for each artillery piece to hit that spot was created. Any enemy ship approaching the coast would be sighted by the shore observation posts – each post radioing the target angle (from their perspective) and heading/speed.
The guns would receive these datapoints, look them up in a book, dial in the azimuth/angles indicated and fire. Hypothetical example: station 1 – 272 degrees, station 2 – 265 degrees would correspond to 35 degree azimuth, 285 degree angle. Gun fires… Enemy starting seeing splashes all around them with no idea of where they’re coming from. High precision continuous shots until they’re either hit or retreat.
Really cool bit of history and a very clever system.
Forward observers out on an OP will see bad guys. They can use laser/gps equipment that will give them up to 10 digit MGRS grid location that can be plotted on a map. They can also use direction+distance from their location to get the target location as well. In the absence of technology they can use compass/protractors plus terrain association (translating the landscape you see to a map) to determine a six digit grid. 10 digit grids are accurate to like a meter. Six digits grids are 50 meters if I remember correctly. I’ve been out for a decade. It was considered an effective hit if the round landed within 50m of a target.
The FO will send the target data to Fire DIRECTION Control (FDC). They do some nerdy computer stuff and translate the target data, weather, battery location etc, that is sent to the guns. Gun crews input data, load a round, pull string go boom.
If the round misses the FO will spot it and provide the adjustments to get on target. Artillery isn’t a precision weapon, close enough is good enough. That’s also why it only gets like a week to play in a war then everything goes to precision munitions.
I’m sure more current 0861s or the army equivalent can add to this or correct me.
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