Talk:Indirect fire

Definition

This definition of indirect fire manages to miss most of the key points.

Indirect fire has to be used when a target cannot be seen through the gun's sights. It may be visible to the crew and it may be used even if the target is visible through the sights. Modern indirect fire emerged in theory in the 1880s and in practice in the 1890s when all necessary instruments became available. Indirect fire originally emerged to get gun positions out of direct fire from the enemy. Subsequently the primary purpose became to engage targets that were not visible from the proximity of the gun position.

Indirect fire involves setting firing data on the sights. This data involves something to give the azimuth to the target and something to give the range to the target. The former involves some sort of aiming point as a reference and the latter is usually converted to something relative to the horizontal plane. Modern practice is to take the target's grid reference or coordinates and calculate firing data between this and the gun's location, early indirect fire used other methods.

Indirect fire may be observed or predicted. Observed fire means a human observer or target acquisition system locates the target and can if necessary adjust the points of impact of the projectiles. The firing data for observed fire may or may not include corrections for non-standard conditions. In modern armies it usually does but this was not always the case.

Predicted fire means the target is accurately located by some means and firing data always includes corrections for non-standard conditions. The basic methods were developed and refined in World War 1. The objective of predicted fire is to avoid having to adjust the points of impact or to attack targets that cannot be observed due to their position, weather or darkness. Variations to standard conditions are caused by differences from standard air temperature, air pressure, wind speed and direction and the muzzle velocity of the gun (which has several sources including propellant temperature, projectile weight and the extent of barrel wear).

Nfe 02:54, 25 January 2007 (UTC)

redirect!

Is this some sort of a joke to redirect the direct fire to indirect?! The two have almost nothing in common as forms of ordnance delivery other then using basic ballistics principles.--mrg3105 (comms) ♠♥♦♣ 02:36, 5 April 2008 (UTC) I take it back, this was not a joke...just written by someone not seemingly aware of military history and technology--mrg3105 (comms) ♠♥♦♣ 02:38, 5 April 2008 (UTC)

Direct/Indirect relation

Is it correct to say that (technically) if a 45 degree shot (by elevation) reaches the longest distance, then a 30 degree (45-15) will reach the same distance as a 60 degree (45+15) shot? If so, could the lower-than-45 shot be considered direct fire, and the higher-than-45 shot considered indirect fire? If so, I think this is a great explanation (or one way of viewing things). —Preceding unsigned comment added by 79.181.124.87 (talk) 09:54, 22 July 2008 (UTC)

No, it is not technically correct in atmospheric conditions to say a projectile fired at 30 degrees and one fired at 60 degrees travels the same distance. In fact, ONLY in a vacuum will the range of the projectile be at its greatest at 45 degrees. In atmospheric conditions, the range is at it's greatest somewhat below 45 degrees. This is because the trajectory curve is a non-rigid trajectory as a result of other forces besides gravity (wind resistance, etc.) and is not parabolic, but semiparabolic. See http://www.eugeneleeslover.com/USNAVY/CHAPTER-17-A.html

As far as defining indirect fire as anything other than "non-line-of-site" I firmly disagree. In indirect fire, the guns are aimed off reference points that essentially mimic a compass, and the firing elevation data is based on calculating range-to-target. The guns don't see the target. An observer calls in the target location, the Fire Direction Center calculates the trajectory, the guns lay on said data, and fire the mission. Elevation of the guns is irrelevant. We already have terms for that (High Angle [above 45 degrees] and Low Angle [below 45 degrees]) This is why I disagree with Ft. Sill reecently deciding to (FA proponent, US Army and Marines) call "[Killer Junior]" Observed Indirect Fire. If the guns see the target and "direct lay" on it, it's not indirect anything. Caisson 06 (talk) 21:26, 10 July 2009 (UTC)

Somebody please explain the 45 degrees rule!

...an provide the graph. I couldn't even find a picture or diagram on Commons showing this. (Looked in Commons:category:Ballistics and Commons:category:Parabolas.) Here is one external link with the textbook image and a reference:

• When Sledding...You May Encounter a Jump...

I guess you will find the same image in "Serway and Jewett" on page 87. -- Petri Krohn (talk) 23:45, 2 March 2009 (UTC)

--Explanation: Let's assume you fire a gun so that the projectile leaves the bore exactly parallel to the ground (the ground is assumed to be level). The projectile's initial velocity is all directed horizontally. But immediately, gravity starts accelerating said projectile downwards. If the bottom of the barrel's bore is four feet above ground, the projectile will strike the dirt in just under half of a second. If the muzzle velocity is 1615 ft/sec, that of the WWI 18 pounder, the projectile's range is 805 feet (I'm disregarding air resistance, and rounding to the nearest foot).

Now imagine the gun is still firing completely horizontally, but from the top of a hill or cliff. The projectile has further to fall, so it stays in the air longer, and the range is increased.

805 feet being too short under most circumstances, and hills not being available on demand, the gunner elevates the gun barrel to get greater range. Now, the projectile has an upward velocity, causing it to rise as it moves horizontally away from the gun. Gravity will still provide an acceleration downwards, but the projectile will keep rising till gravity has cancelled the upward velocity. Now gravity starts accelerating the projectile downwards, but from a higher altitude than firing horizontally. The projectile stays in the air longer, and goes further.

But you don't get something for nothing. To get upward velocity, you had to rob the horizontal velocity. The horizontal velocity is no longer the muzzle velocity, but the muzzle velocity multiplied by the cosine of the angle of elevation. If the elevation is ten degrees, the horizontal velocity is now 1590 ft/sec for our 18 pounder. The upward velocity is the muzzle velocity times the sine of the elevation angle, about 280.4 ft/sec for our ten degree angle. Our projectile will now stop rising about 1,221 feet above the muzzle of the gun, 8.7 seconds after firing, and take another 8.7 seconds to fall back to earth (again, neglecting air resistance, and rounding). Our projectile now has a theoretical range of about 27,700 feet, or five and a quarter miles (1590 ft/sec horizontal velocity times 17.4 seconds flight time).

Obviously, the higher you elevate the gun barrel, the longer the projectile stays airborne. But as elevation increases, horizontal velocity decreases. At 45 degrees, upward and horizontal velocity are equal, 1142 ft/sec from our 18 pounder. The range is 40,500 ft, or 7.67 miles. Below 45 degrees, upward velocity increases faster than horizontal velocity decreases. Above 45 degrees, horizontal velocity decreases faster than upward velocity increases, and range drops again. 45 degrees gives you maximum range.

All that is theoretical, though. If you're shooting on a planet with an atmosphere, atmospheric resistance is constantly slowing down your projectile. But said resistance varies with location, altitude and weather. A projectile from a gun with really high muzzle velocity can spend most of its flight in air rather thinner than that where it was launched. And winds vary in direction and velocity at different altitudes too. Are you firing at sea level? From the top of a mountain? What's the barometric pressure, and which way and how fast are the winds blowing at different altitudes and locations? The Paris Gun was fired at 50%, because of the extreme height the shell reached. So depending on location, weather, and muzzle velocity, the maximum range may be obtained at greater or less than 45 degrees. But if you're shooting on the moon, 45 degree elevation should give you maximum range.Saintonge235 (talk) 21:04, 5 December 2020 (UTC)

Prism paralleloscope for indirect fire?

What is this a Prism paralleloscope? This article is an orphan and not have any references or sources. And no other articles in Wikipedia does not mention such a device, including the article Indirect fire. Excuse my bad English. Andrew M. Vachin (talk) 13:33, 7 August 2013 (UTC)

Try here http://nigelef.tripod.com/sights.htm Nfe (talk) 08:52, 8 August 2013 (UTC)

--A simple description is that a paralleloscope is a form of periscope. Unlike a submarine periscope in an old movie, where the Captain has to move sideways as he rotates the 'scope, the head of the paralleloscope can rotate independently, so it can be pointed in different directions without moving the eyepiece. There's also a scale of some kind that allows you to measure the angular deflection from straight ahead.

The device also has a telescopic sighting feature. So think of it as a surveyor's optical level mated to a short periscope and you have the basic idea.Saintonge235 (talk) 21:54, 5 December 2020 (UTC)

Definition

The definition doesn't make any sense to me...it is fire that is outside of visual range? Yet than the person above is saying that "the gun crew may be able to see the target, but it's still indirect fire if the weapon's sight isn't on the target" (or something like that). How do you define "sight"? Are you saying it's fire done entirely by pre-set coordinates and angles on the carriage, without even trying to aim? That said, I thought "indirect fire" included fire that was mobbed in a ballistic arc, like mortar fire. Is not a siege mortar firing over the walls of a Napoleonic fortification firing indirect fire, rather than direct, even though the crew is observing their own fall of shot and adjusting accordingly? I suspect the problem is that we are using the modern NATO definition of "indirect fire", while ignoring that fact that it hasn't always meant exactly that. In my mind, "direct fire" is fire that you point in the general direction of the enemy, making the smallest allowance for ballistic fall possible; "indirect fire" is fire that is intentionally fired at a much steep angle so as to make the shot fall in the same location, but at a much steeper angle (or to make the shot reach past the maximum possible range of a weapon being fired directly). I think we're dealing with two different sets of definitions. AnnaGoFast (talk) 02:33, 11 April 2016 (UTC)

Indirect fire is a method of laying guns without aiming their sights directly at the target (AKA 'direct fire'). It's mostly (99.99etc%) used against targets that cannot be seen from the gun position. It is usually used against targets many km from the gun position.

For example, a mortar is only capable of indirect fire (assuming use as designed) but can deliver it against targets whether or not the operator has a line of sight to them. As noted, indirect fire may be "self observed". "Sights" for an indirect fire weapon often turn out to mean a device designed to set bearing and elevation rather than something the layer views the target through. 93.145.221.210 (talk) 12:40, 30 August 2018 (UTC)