Mortar fire

[Ulzgoroth]

Originally Posted by Michele

The opposition exists in the very texts you mention.
It's in the word "area". Note it is absent in the second definition. With a mortar, a howitzer, an orbital weapon, an unguided torpedo, an ICBM and even a 406mm battleship battery firing from 15 miles away you are firing at a place. It changes little if you yourself can see it.

That doesn't hold water at all. Gunner can be used to attack areas as well as point targets. (As can Guns, Throwing, and any other ranged attack skill delivering an area-of-attack payload. Box on p414.)

And things designated under artillery are routinely used to attack specific targets. In some cases you could construe that as attacking an area, but that's only true in the same way that rifle fire aimed at an individual is actually aimed at either the area that that individual occupied when the shot was taken, or the area the individual was expected to occupy when it arrives. In some cases, you couldn't even make that claim - Artillery (Guided Missile) is almost always about directing that missile to a specific individual target, wherever it may be when the missile gets there.

Certainly many of them can be used to make actual ground-pounding area attacks, and some of them usually are. But I doubt there's a single Artillery sub-skill that has to be.

Originally Posted by whswhs

On one hand, that's true. But on the other, it's not what is meant. Yes, if I throw a toy mouse across the room to pass just over my cat's head, it's following a curved trajectory. But the basic mental process is still "point and shoot [throw]." The arc followed by the mouse is close to the line from my eyes to the target. If I toss it up in the air, I can focus either on the toy or on my cat, but the one I don't focus on will be in my peripheral visual field, or even out of sight. Or I'll have to shift my gaze between them.

I...do not find I have any need to aim my eye along the initial trajectory when performing a lobbing throw. If for some reason I wanted my eye on the thing to be thrown I'd be looking down, but that isn't really relevant either. I think your analogy breaks pretty badly.

Now if you're using a launcher (or firearm) with the sighting arrangement set along the barrel, yes, you start to have a problem when the angle between the line to the target and the barrel grows. But sighting arrangements that are set to the side of the barrel and thus can point forward while the barrel points up are a thing used for direct-lay of large guns at long ranges.

Originally Posted by Anthony

For all shots at less than absolute max range, there are two solutions to the ballistics equations, and they are quite different; mortars use the higher angle solution, and are also very low velocity.

Consider a shot at 300 meters, which is a reasonable infantry engagement range. In all cases I am ignoring air resistance.

A rifle bullet will have a travel time of about 1/3 of a second, and must be aimed slightly over a meter over its target (assuming the sight is zeroed at 0m; if it's zeroed at 200m you only need to aim about 40cm above).

A pistol bullet will have a travel time of 2/3-1s, and thus must be aimed 5-10 meters above its target.

A 150m/s direct fire round (similar to a mortar) has a 2s travel time and must be aimed 40m above the target.

A minimum velocity round, fired at 45 degrees, has a velocity of 54m/s (38m/s v and h) and a travel time of 7.7s.

A 150m/s high angle round aimed 300m away has a travel time of 30s...

Yes, this is something that I think my posts would have told you I know. What are you getting at, though?

[Anthony]

Originally Posted by Ulzgoroth

Yes, this is something that I think my posts would have told you I know. What are you getting at, though?

That it's a somewhat fundamentally different problem? The way GURPS defines artillery vs gunner is that it's indirect fire vs direct fire, and it goes on to say that indirect fire is 'to put fire onto a target area via a high ballistic arc or similar path'.

This doesn't make sense for several of the specialties (I would argue that the skills artillery (beams), artillery (guided missile), and artillery (torpedo) don't actually exist), but for guns at least it's clear enough. I guess you could say that any situation where the attack hits the target at a high angle (say, >30° or 45°) should use artillery rules, though artillery (torpedo) still fails to make sense.

[Ulzgoroth]

Originally Posted by Anthony

That it's a somewhat fundamentally different problem? The way GURPS defines artillery vs gunner is that it's indirect fire vs direct fire, and it goes on to say that indirect fire is 'to put fire onto a target area via a high ballistic arc or similar path'.

This doesn't make sense for several of the specialties (I would argue that the skills artillery (beams), artillery (guided missile), and artillery (torpedo) don't actually exist), but for guns at least it's clear enough. I guess you could say that any situation where the attack hits the target at a high angle (say, >30° or 45°) should use artillery rules, though artillery (torpedo) still fails to make sense.

I wouldn't agree that it's fundamentally different provided you have high-angle sights - the most fundamental difference is that you push the barrel down for more range rather than up...and that at short ranges you have to have much more accurate range information. But moreover, it's extremely questionable whether GURPS means 'high ballistic arc' that way. Early 20th century guns and modern gun-howitzers alike can and do perform long-range non-direct fire at low angles. You probably aren't intended to use Gunner for that.

Your thing about the angle the attack hits at is really not advisable, since that would make shooting a handgun or rifle down out of a helicopter into an Artillery task for no useful reason.


My own theory for the uniting but still questionable logic behind the Artillery family is that notionally aiming them is a more technical and (often, though not always) calculation-oriented process rather than a matter of perception and coordination. Hence the IQ rather than DX basis. Which is mostly fair-ish if we take Artillery (Cannon/Catapult) to be about fire that isn't direct in the sense used in the Gunner text, or fire where there's line of sight from gun to target but you still use mostly the same procedures as you would if there wasn't. That seems to me to make Artillery a relatively coherent concept. Though still a bit of a dubious fit for dive bombing. EDIT: It also implies that the same gun can potentially make the same shot with Artillery or with Gunner, depending on whether you have somebody lay it over a range-calibrated sight attached to the weapon, or somebody using separate instruments and calling a bearing and elevation that the gunners follow.

[Curmudgeon]

Originally Posted by geppo_68

Dear all,
could you someone explain to me in detail the use of mortars with a line of sight to the target?

They obviously use always indirect fire, but:
a) do you use the Artillery skill?
b) does the range/size/speed chart apply?
c) could you Aim and then use the Acc bonus?

conversely, I reckon that without line of sight as in High Tech p 139
"Observed lndirect fire" they
a) use Artillery skill coupled with the FO skill
b) do not use the Range/size/speed chart
c) do not use the Aim or Acc bonus
d) they can use the bonus given by the FO rolls only to offset the intial -10 "shooting blind" malus

And "Predicted Indirect fire" they
a) use Artillery skill
b) do not use any bonus/ malus for range or other reason, just the flat Artillery skill

Is it the correct interpretation?

Thanks and best regards

First, mortars do not always use indirect fire, though, by definition, they will always fire high angle, i.e. no less than 45° elevation.

Second, at least one mortar that is unambiguously a mortar, the Ordnance ML 2" Mortar was only able to be fired in direct fire mode. In direct fire, the Gunner skill is the right skill to use and the range/speed chart would apply. The key to both the ML 2" mortar and the Japanese knee mortar (another direct fire only weapon) was the ability to make rapid corrections, coupled with a relatively high rate of fire.

It is commonplace to say you use indirect fire in those cases where you don't have direct line of sight to the target. It isn't strictly true, though even real world gunners do often oversimplify it that way.

The real difference between direct and indirect fire is in the sighting system used. For a direct fire sighting system, like a rifle, in order to hit the target, you lay your sight on the target. An indirect fire sighting system has you lay on an aiming point (that is not the target) to point the barrel at the target.

Generally speaking, direct fire weapons, like rifles, machine guns and tank guns cannot use indirect fire because their sights won't allow you to align the barrel with the target if you look anywhere but at the target. Indirect sighting systems sometimes have the an option to partially swap sights allowing them to engage in direct fire as well. I say a partial swap because you usually only need to swap out the range/elevation sight, but that depends on having separate sights for bearing and range/elevation.

[Rupert]

Originally Posted by Curmudgeon

First, mortars do not always use indirect fire, though, by definition, they will always fire high angle, i.e. no less than 45° elevation.

By some nations' definitions. Others use the term to describe the means by which the round is propelled, or the general design of weapon. 'Mortar', like 'howitzer', can be a precise term but it's one that can have different meanings to different users. The US' definition of a mortar as high-angle only, and howitzers as high or low angle isn't how the Soviets defined them, for example.

[Michele]

Originally Posted by Ulzgoroth

That doesn't hold water at all.

Please keep in mind that, while I have some passing knowledge about how these things work in real life, I'm chiefly trying to answer the OP's question, which was about the GURPS RAW. Now, if you dislike the fact that the GURPS weapon tables listing mortars begin by "Artillery (Cannon)", you can come up with your own house rules, YMMV.
But that doesn't help the OP.

That said, you didn't notice the difference in the rules' descriptions, the one between "target areas" and "targets". I pointed it out to you. I can't help it if you are unhappy with it.

Now on to the rest. Yes, even with a rifle, using Guns, you have to choose an aiming point that is not exactly onto your target object - in some cases. I.e., mostly when you fire at long or very long ranges. You then consider bullet drop, bullet travel time, target movement, and even weather. However, you can do so instinctively, intuitively - and in that case you are using Guns as it is, with huge penalties (range/speed, wind etc.). Or, and it's what present-day military snipers do, you can prepare the shot. To do so, in GURPS, you may use for instance Precision Aiming (GURPS Tactical Shooting, p. 26). That means using some of the following aids: ballistic tables, a wind gauge, a spotter (yes). Those snipers also use laser rangefinders, rangefinding binoculars or scopes, range cards, GPSs, and whatnot (p. 27). In short, an array of device and procedures that remind us of what the FO's and artilleryman's jobs are. And GURPS RAW give bonuses if you succeed at using all of that.

What about present-day tank guns? Still used with Gunner, of course, even when engaging enemy tanks at extreme ranges. Yet, they all come with their own computer - which does a lot of artillery-like work for the gunner before he fires the round. And GURPS RAW factors that in as a bonus modifier.

In other words, when you have to calculate a non-intuitive trajectory that doesn't depend on your eye-hand coordination and DX, to a target area, GURPS rules say, you use Artillery. And even when you use a weapon that's designed for DX rather than for calculations, like a rifle, if you are using it in some way as to target an area, you will be better off if you can use some artillery-like aids.

Gunner can be used to attack areas as well as point targets. (As can Guns, Throwing, and any other ranged attack skill delivering an area-of-attack payload. Box on p414.)

Absolutely! Never said you couldn't attack areas with weapons that are listed for use with Guns, Gunner or Throwing. I said you can't use Gunner with weapons that are listed - because designed - to be used with Artillery.

That said, please note that you are reading a box from a chapter titled "Special Combat Situations". And that the description of the Throwing skill specifies that it's different to try to hit a target object or "to lob an
object into a general area.". The latter is easier, but, of course, you won't be necessarily hitting the target object if you succeed - you'll hit the... general area.
In other words, the use of Gunner, Guns, Throwing or DX to do artillery-like trajectories is an outlier.

As to the general idea that you have that Gunner could be used if the operator of an Artillery weapon can see the target, if so, then why aren't unguided torpedoes always used with the Gunner skill? They were never ever fired with the help of a FO. The submarine captain saw the target, so why can't we say he had a Gunner (Torpedo) skill that he could use?

I think that's because after seeing the target, and observing it for a while, he then did rather complex calculations, assessing his and the target's position, speed and course, then more calculations to decide the best combination of speed and run time of his torpedoes. Then he made his Artillery roll to send the torpedo spread to the area he expected the target to be in, in maybe ten or more minutes.

[Michele]

Originally Posted by geppo_68

This Is my initial problem in interpreting the rules of High Tech:what are the tables and mods involved in each of the 3 scenarios described in my first post? The thread Is derailing a bit...

Definitely you use speed/range. It's not as if artillery had the same accuracy at all ranges.

And speed is critically important. Mortars can certainly hit a non-moving area, even though, possibly, after two tries. That's how they are used. But if you try to use a mortar against a light tank zig-zagging at full speed across the battlefield, good luck.

Indeed, the way for a WWII battery of mortars to engage a moving platoon of tanks is for the battery commander to have pre-planned a fire mission for a choke point, and then, once the tanks are sighted, to calculate in how much time the tanks will arrive there, and to fire at that area accordingly.

A direct hit would still be lucky, but if the commander succeeds in his Artillery roll, the tanks will walk into the barrage, possibly suffer some minor damage by near misses, and be forced to close their hatches.

[Ulzgoroth]

Originally Posted by Michele

Now on to the rest. Yes, even with a rifle, using Guns, you have to choose an aiming point that is not exactly onto your target object - in some cases. I.e., mostly when you fire at long or very long ranges. You then consider bullet drop, bullet travel time, target movement, and even weather. However, you can do so instinctively, intuitively - and in that case you are using Guns as it is, with huge penalties (range/speed, wind etc.). Or, and it's what present-day military snipers do, you can prepare the shot. To do so, in GURPS, you may use for instance Precision Aiming (GURPS Tactical Shooting, p. 26). That means using some of the following aids: ballistic tables, a wind gauge, a spotter (yes). Those snipers also use laser rangefinders, rangefinding binoculars or scopes, range cards, GPSs, and whatnot (p. 27). In short, an array of device and procedures that remind us of what the FO's and artilleryman's jobs are. And GURPS RAW give bonuses if you succeed at using all of that.

What about present-day tank guns? Still used with Gunner, of course, even when engaging enemy tanks at extreme ranges. Yet, they all come with their own computer - which does a lot of artillery-like work for the gunner before he fires the round. And GURPS RAW factors that in as a bonus modifier.

In other words, when you have to calculate a non-intuitive trajectory that doesn't depend on your eye-hand coordination and DX, to a target area, GURPS rules say, you use Artillery. And even when you use a weapon that's designed for the above, like a rifle, if you are using it essentially to target an area, you will be better off if you can use some artillery-like aids.

The 'intuition', and it's really not 'instinct', isn't doing the same thing as the calculation. It's just doing it faster and usually less accurately. And using tools that embed the computations automatically.

Originally Posted by Michele

Absolutely! Never said you couldn't attack areas with weapons that are listed for use with Guns, Gunner or Throwing.

You chose to point out the absence of the word "area" in Gunner. If you prefer to focus on its presence in Artillery, well, please see the entire second paragraph of the post you chose to respond to only the first three sentences of. The idea that 'artillery weapons' must attack an area rather than an actual target is insupportable.

Originally Posted by Michele

As to the general idea that you have that Gunner could be used if the operator of an Artillery weapon can see the target, if so, then why aren't unguided torpedoes always used with the Gunner skill? They were never ever fired with the help of a FO. The submarine captain saw the target, so why can't we say he had a Gunner (Torpedo) skill that he could use?

I think that's because after seeing the target, and observing it for a while, he then did rather complex calculations, assessing his and the target's position, speed and course, then more calculations to decide the best combination of speed and run time of his torpedoes. Then he made his Artillery roll to send the torpedo spread to the area he expected the target to be in, in maybe ten or more minutes.

That's a somewhat overblown model of a torpedo attack, but it might be not too terribly far off for a submarine. (Aside from the emphasis on 'area', I'll get back to that.) But torpedoes were never submarine-specific weapons. Torpedoes were also weapons fired from the decks of destroyers. And from fixed tubes or exposed drop mountings on speedboats that sometimes had more automatic weapons mounted than they had sailors, fully intended to be launched while charging straight into the teeth of major surface combatants. They're not going to be spending minutes at the plotting board while that's going on, let alone trying to tinker with the torpedo's propulsion settings. Leading a ship with a torpedo isn't really different from deflection shooting of guns. The travel time involved is certainly rather longer, but both the concept and the execution are not so very different.

The idea that torpedoes attack an 'area' is an absurd distortion in the case of your submarine attack. The entire point of the attack is hitting a specific target. There's no question about whether the torpedoes will pass through the area that they're aimed through, barring a mechanical malfunction. The task is hitting the ship, not hitting any given patch of water. Tangentially, torpedo boat or destroyer torpedo attacks could have a legitimate area attack element - a spread of torpedoes fired into an enemy formation is highly disruptive even if all the ships are able to maneuver to avoid being hit. Of course, infantry machine gun fire is primarily a disruptive area attack, but it's handled with Gunner.

So you pose the question, why Artillery (Torpedo) rather than Gunner (Torpedo)? I think the most substantive answer would really be because launching torpedoes is decidedly unlikely to hinge on coordination or reflexes, so giving them an IQ-based skill makes more sense than a DX-based one. Torpedoes do not "put fire onto a target area via a high ballistic arc or similar path." Nor do most guided missiles. It's a stretch even for bombs! The textual rationale does not stand inspection as a unifying concept.

My question would be why Age of Sail cannon-fire is stuck under Gunner, considering that any adjustment to gun pointing (aside from waiting for the ship to roll, if your gun is on one) would take multiple seconds and often several men to effect.

[Michele]

Originally Posted by geppo_68

Michele, your suggestions seem spot on.

By the way, could you tell us which kind of mortar you plan to use? I mean, ideally we all like a general, comprehensive rule. But if it will be a 32-cm siege monster, whose crew can see the enemy because of an unexpected turn of events,... then we can, at least for the time being, stop worrying about the gun-mortars, the weird mortar/HMG combo, the small-caliber Japanese 89 Shiki "grenade discharger" and Italian Mod. 35 "assault mortar", and other similarly marginal cases.

[jason taylor]

Originally Posted by Michele

Indeed, the way for a WWII battery of mortars to engage a moving platoon of tanks is for the battery commander to have pre-planned a fire mission for a choke point, and then, once the tanks are sighted, to calculate in how much time the tanks will arrive there, and to fire at that area accordingly.

Could infantry mortars pentrate tank rooftops?

Did they have scatterable mines in WW2?