Proximity fuzes in GL?

[rocketman]

I might be misremebering things, but were proximity fuzes not available until late 1944 in the Battle of the Bulge? Noticed in the Monte Cassino campaign, mission 2, that you can do "personnel" (air burst) mission for one of the arty assets. Is this correct? Or is it something introduced in the upcoming module that covers the later period, but it has creeped in already via the patch?

[Michael Emrys]

The "personnel" rounds are indeed air bursts, but they are timed fuses, not VT (influence) fuses. If you watch closely, you may notice that the timing is off on some of them and they actually function as contact fuses.

Michael

[General Liederkranz]

I believe that the Personnel setting is also only available for missions plotted before the game starts, or near TRPs--on the assumption that the artillery knows the exact range to TRPs, or has time to measure it before the game starts, so they can set the fuses appropriately. 

[MOS:96B2P]

On 7/17/2019 at 4:51 PM, rocketman said:

I might be misremebering things, but were proximity fuzes not available until late 1944 in the Battle of the Bulge? Noticed in the Monte Cassino campaign, mission 2, that you can do "personnel" (air burst) mission for one of the arty assets. Is this correct? Or is it something introduced in the upcoming module that covers the later period, but it has creeped in already via the patch?

In WWII titles personnel airburst rounds must be requested during preplanned bombardment or in range of a TRP to work.

In CMFB a (VT) equipped asset can fire personnel airburst rounds anytime without a TRP.  

[rocketman]

Good to know. Wouldn't it be incredibly difficult to set the timer exactly to obtain a burst at an optimal height? For a shell travelling far it must be a matter of a fraction of a fraction of a second that makes all the difference. Could they do that or does it work in a different way? I might do a test mission to try to acertain how many "good" airbursts you get out of a mission.

[Michael Emrys]

19 hours ago, rocketman said:

Wouldn't it be incredibly difficult to set the timer exactly to obtain a burst at an optimal height?

I would guess it didn't matter too much. If you fire enough shells (and think of how many were fired in important missions), enough will go off at effective heights to get the job done. It's still better than firing only shells with contact fuses.

Michael

[rocketman]

6 hours ago, Michael Emrys said:

I would guess it didn't matter too much. If you fire enough shells (and think of how many were fired in important missions), enough will go off at effective heights to get the job done. It's still better than firing only shells with contact fuses.

Michael

This is true - IRL it would't matter as they did enourmous prep bombardments. But it does, in-game, per shell fired, give the impression of "high-tech" that is way too efficient. Maybe that is a design choice as we don't fire that long missions. Just my 2 cents.

[MikeyD]

In WWII US artillery was considered an art form. They took great pride in their ability to perform the seeming impossible. I recall an anecdote of a Japanese soldier, after being captured, requesting to be shown the fabled US 'automatic artillery'. Because they couldn't imagine artillery of such precision from mere standard artillery practices.  US artillerymen in NW Europe openly despised the Calliope  artillery rocket system because the concept ran counter to everything an artilleryman held dear.

[rocketman]

I don't doubt that they considered atillery an art form and that they were very skilled. But isn't that in consideration to coordination of assets, planning and accuracy? If shell fuzes can't be timed to fractions of seconds because of tech limitations, then it doesn't matter how skilled the artillery sections and FOs are really - the shells will burst at varying height from the ground. I did my military service as a FO and I'm not saying that I was a fully fledged expert, but I remember it being said in training that (and this was in 1991) that it is extremely hard to predict how wind up high where the shells travel will affect accuracy and that it can vary quite much from minute to minute.

[Ultradave]

On 7/19/2019 at 9:34 AM, rocketman said:

Good to know. Wouldn't it be incredibly difficult to set the timer exactly to obtain a burst at an optimal height? For a shell travelling far it must be a matter of a fraction of a fraction of a second that makes all the difference. Could they do that or does it work in a different way? I might do a test mission to try to acertain how many "good" airbursts you get out of a mission.

No, it's not difficult at all. There are firing tables and "slide rules" that will calculate trajectory to the target impact point. For a timed fuse airburst, there is a correction to make so that the elevation to fire makes it so it passes over the target at the desired height, rather than hits the target. The first calculation is to the target ground point so you know the time of flight. Set the time fuze for that time of flight and BOOM, it goes off 10m (or whatever you calculated) right over the target as it passes over. 

VT is a little different in that you don't need the time setting, just the correction for 7m height above the target point. The transmitter will receive a strength signal from the ground return and explode at 7m height (not sure what that height was in WW2 but in my artillery days it was 7m). There IS a time setting so it doesn't go off prematurely, but you don't need exact time to the target.

All the firing data is well tabulated. Just a matter of running some calculations, which don't take long, just a few extra seconds for the calculations (10-30), and a few (less than 10) on the gun to set the fuze (top of the fuze rotates - just match the hairline to the time desired). My artillery experience predates GPS and computers - all manual calculations, so my experience is MUCH more like WW2 and Korea than it is present day artillery (which is all computerized whizz-bang magic  )

So the answer to your question is any competent fire direction center can make the calculations in little more time than a PD (point detonating) mission, and you should get a battery sheaf of airbursts all at once. Devastating to troops in the open, and effective against trench lines. Adjusting rounds are done with ground bursts to make it easier for the FO to see where the round landed (hard to judge and airburst). Then FFE with the time or VT rounds.

Hope that helps.d

Dave (ex-US Army CPT,  2/321st FA (Abn), 82d ABN DIV)

 

[edit] one other thing I thought of. We only carried about 20% time and/or VT fuzes with us. The rest were PD. Don't know what the ratio exactly was in WW2 and probably varied but my understanding is that they were probably about the same and VT was rare.

Edited July 22, 2019 by Ultradave

[rocketman]

Thanks for the detailed information. So I guess my follow up questions would be: 1) In what increments could the fuze of a WWII shell be set? Tenths of seconds? 2) How well could they in WWII time the flight to target? They didn't really have advanced timepieces in the field - right? Would a 1 sec mistiming lead to a failed mission, given the scale of most CM missions?

Another question of interest is what an "optimal" height for an airburst would be, given flat open terrain? I suppose it would vary for the caliber fired. My impression is that all airbursts in CM occur at the same height - but I have to double-check that.

[Frenchy56]

While I can't give you any concrete material, be reminded that the artillery has been referred to as an 'intellectual' arm since the 18th century.

Edited July 22, 2019 by Frenchy56

[rocketman]

Again, no doubts whatsoever about artillery being an intellectual task or that the US/Allied forces were professional - I'm trying to figure out if the kind of airbursts we see in the WWII titles are realistic or not or a matter of game engine limitations and/or design choices. That's all.

[Ultradave]

Our time fuzes had 0.1 second increments. You'd need that to get the detonation where you want. I can't say for sure about WW2 but I would expect they'd have to be the same just to have any chance of exploding where you want it to. I really don't think time fuzes changed from WW2 to the 70s.

Super accurate timepieces - not really that necessary. The firing data has been accurately tabulated for each model howitzer. For example, we had "firing sticks" that were essentially slide rules that gave elevation and time for the range. There is a different stick for each charge (number of powder bags used). Typically we tried to fire at a range requiring charge 4 or 5 - most accuracy. Then you make a correction to raise the elevation so that the round passes over the target. My experience was with M102 105mm howitzers (the 82d Abn is a light unit so no heavy artillery). Smaller rounds, lower airburst, only because the effective radius of the burst is less for smaller caliber artillery. 

Given time in a position, we would add corrections to individual guns for their position so that the grouping of rounds came out evenly, and additional corrections to hit a center point. We also flew weather balloons to get winds at altitude levels and added corrections for those (daily). And corrections for the rotation of the Earth, which of course varies by 1) latitude, and 2) the primary axis of fire (direction the guns are pointing). Howitzers are low velocity, relatively high elevation weapons so all these things make a difference. 

Adjusting fire - stopwatch is handy in the fire direction center. We know time of flight. In game you can here shot, splash over the radios. Shot is obvious. Splash means 5 seconds to impact. So if the FO is keeping his head down, the splash gives him 5 seconds to take a look, and re-orient himself to the direction. Then he quickly decides corrections, covers again and radios the directions in (left 200, drop 400, etc).

The one time you really need accurate timing is a time on target mission. One battery is 4 or 6 guns. A battalion is 3 batteries. A battalion time on target requires each battery to calculate its time of flight to the target, the battalion fire direction center to synchronize everyone (whether time of day mark or a say, 60 seconds to TOT). Then the batteries each fire at the right time for their time of flight so all rounds arrive together. It can be even more interesting if one battery is firing time rounds and the other two PD rounds. The battalion fire direction officer coordinates all that (I did that job too as  the asst ops officer for the artillery battalion). 

It can get pretty technical but really it's no more than high school math level, and knowing what to do with the data. It helps being good at mental math and visualizing things spacially - being able to know instantly that data sounds incorrect (biggest fear was hitting your own troops accidentally). Today things are much different of course, but I was there in the late 70s and 80s. Computers were just coming in. We had one GPS in the division and it took up the whole back of a jeep. We had an analog computer but it never worked after being dropped in the back of a truck so we stuck with "charts and darts". Batteries were surveyed in position from landmarks. No GPS. You really had to be good (excellent really) at map reading.  So I suppose you could say it was pretty "intellectual"  It doesn't feel that way really. You practice and practice so calculating firing data becomes routine. 

[Ultradave]

33 minutes ago, rocketman said:

Again, no doubts whatsoever about artillery being an intellectual task or that the US/Allied forces were professional - I'm trying to figure out if the kind of airbursts we see in the WWII titles are realistic or not or a matter of game engine limitations and/or design choices. That's all.

They seem about right to me. 7m for VT, for time fuzes we would set the gun elevation to achieve a certain height. 10 meters usually for time rounds.

Also, you can't fire VT over water. The return from the water will be too strong and set off the round.

[Michael Emrys]

28 minutes ago, Ultradave said:

Also, you can't fire VT over water. The return from the water will be too strong and set off the round.

That's interesting. I hadn't heard that before. Thanks.

Michael

[rocketman]

2 hours ago, Ultradave said:

Our time fuzes had 0.1 second increments. You'd need that to get the detonation where you want. I can't say for sure about WW2 but I would expect they'd have to be the same just to have any chance of exploding where you want it to. I really don't think time fuzes changed from WW2 to the 70s.

Super accurate timepieces - not really that necessary. The firing data has been accurately tabulated for each model howitzer. For example, we had "firing sticks" that were essentially slide rules that gave elevation and time for the range. There is a different stick for each charge (number of powder bags used). Typically we tried to fire at a range requiring charge 4 or 5 - most accuracy. Then you make a correction to raise the elevation so that the round passes over the target. My experience was with M102 105mm howitzers (the 82d Abn is a light unit so no heavy artillery). Smaller rounds, lower airburst, only because the effective radius of the burst is less for smaller caliber artillery. 

Given time in a position, we would add corrections to individual guns for their position so that the grouping of rounds came out evenly, and additional corrections to hit a center point. We also flew weather balloons to get winds at altitude levels and added corrections for those (daily). And corrections for the rotation of the Earth, which of course varies by 1) latitude, and 2) the primary axis of fire (direction the guns are pointing). Howitzers are low velocity, relatively high elevation weapons so all these things make a difference. 

Adjusting fire - stopwatch is handy in the fire direction center. We know time of flight. In game you can here shot, splash over the radios. Shot is obvious. Splash means 5 seconds to impact. So if the FO is keeping his head down, the splash gives him 5 seconds to take a look, and re-orient himself to the direction. Then he quickly decides corrections, covers again and radios the directions in (left 200, drop 400, etc).

The one time you really need accurate timing is a time on target mission. One battery is 4 or 6 guns. A battalion is 3 batteries. A battalion time on target requires each battery to calculate its time of flight to the target, the battalion fire direction center to synchronize everyone (whether time of day mark or a say, 60 seconds to TOT). Then the batteries each fire at the right time for their time of flight so all rounds arrive together. It can be even more interesting if one battery is firing time rounds and the other two PD rounds. The battalion fire direction officer coordinates all that (I did that job too as  the asst ops officer for the artillery battalion). 

It can get pretty technical but really it's no more than high school math level, and knowing what to do with the data. It helps being good at mental math and visualizing things spacially - being able to know instantly that data sounds incorrect (biggest fear was hitting your own troops accidentally). Today things are much different of course, but I was there in the late 70s and 80s. Computers were just coming in. We had one GPS in the division and it took up the whole back of a jeep. We had an analog computer but it never worked after being dropped in the back of a truck so we stuck with "charts and darts". Batteries were surveyed in position from landmarks. No GPS. You really had to be good (excellent really) at map reading.  So I suppose you could say it was pretty "intellectual"  It doesn't feel that way really. You practice and practice so calculating firing data becomes routine. 

Again, awesome insightful post.

Ran a test in the scenario that caught my attention - second of the Polish campaign, "The Gorge": 200m area mission of TRPs, flat area, with the 140 mm howitzer, full 120 rounds mission. Almost all landed within the target area. 52 airbursts (37%) that landed from just above ground and estimated up to what equals a level 3 building. @Ultradave: does this seem reasonable to you? How fast does a shell travel when hurtling toward the ground? Must be several hundred of meters per second. So even a one tenth of a second mistiming would result in much higher airburst or missing the target zone. Or am I missing something again?

[Ultradave]

1 hour ago, rocketman said:

Again, awesome insightful post.

Ran a test in the scenario that caught my attention - second of the Polish campaign, "The Gorge": 200m area mission of TRPs, flat area, with the 140 mm howitzer, full 120 rounds mission. Almost all landed within the target area. 52 airbursts (37%) that landed from just above ground and estimated up to what equals a level 3 building. @Ultradave: does this seem reasonable to you? How fast does a shell travel when hurtling toward the ground? Must be several hundred of meters per second. So even a one tenth of a second mistiming would result in much higher airburst or missing the target zone. Or am I missing something again?

I guess what I was trying to get across in with all my narrative was that while artillery is an area weapon because of it's circular error probability (CEP), in general, firing data from howitzers used for the calculations is VERY VERY accurate. The powder is of high quality and consistent, so you can be pretty well assured that firing round after round they will perform very much the same. The data and the calculations for trajectory, time of flight, etc are very accurate and can be done very precisely. That would be the part you are maybe missing, - maybe I didn't emphasize it enough.

I would never be surprised that ALL of the time rounds from a battery exploded in the air over the target. In fact, I'd be surprised if there were a lot of "misses" where the rounds hit the ground. It is MUCH more likely for that to happen because of an error calculating the data, than the variations or inaccuracies in the rounds and fuzes. They are very consistent. Muzzle velocity of our M102's from my era was about 500m/s. Impact velocity a little less due to air resistance. So yeah, they are moving but nowhere near a tank gun velocity. But we can calculate the trajectory and the time very precisely. 

When I was the Bn FDO we did battalion TOT missions with a combination of ground and airbursts. 3 batteries, (18 guns), 6 rounds each. ALL the rounds landed in a 200m diameter and the time rounds made a cloud of explosions over the target. Frightening in its effectiveness. Satisfying as the man in charge   Think of that as an enemy infantry company or two in the open and 18 rounds explode all at once, then 5 more volleys spaced about 5 seconds apart. After the first round of TOT the guns fire when ready so it's a continuous series of explosions for the rest of the 108 rounds. It works like a charm.

Note that I can only speak for the US, Canadian and British armies as those are the only ones I have direct experience with.  Also, I'm not trying to oversell the FA. Only that I have experience that's pretty similar to calculating firing data was in WW2. The main big difference we had was an FO (sp4 in this case) with each infantry platoon and a FIST chief ( 2LT) with the infantry company commander, so we could control more missions and were more responsive to what was going on right in front. Each infantry LT platoon leader had an FO from the FA battalion attached to him. It's no problem controlling more than one mission in a battery at once. Gets hectic but we were required to handle two simultaneously. 

[Erwin]

Since you are an arty guy, perhaps you can help with a question...  How did one use the Fire Support vehicles?  Am wondering how best to use these vehicles (FIST etc) and their specialized equipment in the CM2 games. 

While leg FO's can move to good vantage points on top of buildings and hide etc. the Fire Support vehicles are way too vulnerable and have to generally sit around safely in the rear doing nothing.  

[Ultradave]

Well, you'd need a guy assigned to a mech infantry division or an armored division. I stayed in the 82d Airborne so no FIST vehicles for me. Once we hit the ground we either walked with the infantry or got moved by chopper. 

Hull down, or moved to a good covered location and dismount to an OP would be my options. But someone with actual experience could say more.

[MOS:96B2P]

1 hour ago, Ultradave said:

I stayed in the 82d Airborne so no FIST vehicles for me. Once we hit the ground we either walked with the infantry or got moved by chopper.   

+1  ALL THE WAY, Sir!!!

[rocketman]

17 hours ago, Ultradave said:

I guess what I was trying to get across in with all my narrative was that while artillery is an area weapon because of it's circular error probability (CEP), in general, firing data from howitzers used for the calculations is VERY VERY accurate. The powder is of high quality and consistent, so you can be pretty well assured that firing round after round they will perform very much the same. The data and the calculations for trajectory, time of flight, etc are very accurate and can be done very precisely. That would be the part you are maybe missing, - maybe I didn't emphasize it enough.

I would never be surprised that ALL of the time rounds from a battery exploded in the air over the target. In fact, I'd be surprised if there were a lot of "misses" where the rounds hit the ground. It is MUCH more likely for that to happen because of an error calculating the data, than the variations or inaccuracies in the rounds and fuzes. They are very consistent. Muzzle velocity of our M102's from my era was about 500m/s. Impact velocity a little less due to air resistance. So yeah, they are moving but nowhere near a tank gun velocity. But we can calculate the trajectory and the time very precisely. 

When I was the Bn FDO we did battalion TOT missions with a combination of ground and airbursts. 3 batteries, (18 guns), 6 rounds each. ALL the rounds landed in a 200m diameter and the time rounds made a cloud of explosions over the target. Frightening in its effectiveness. Satisfying as the man in charge   Think of that as an enemy infantry company or two in the open and 18 rounds explode all at once, then 5 more volleys spaced about 5 seconds apart. After the first round of TOT the guns fire when ready so it's a continuous series of explosions for the rest of the 108 rounds. It works like a charm.

Note that I can only speak for the US, Canadian and British armies as those are the only ones I have direct experience with.  Also, I'm not trying to oversell the FA. Only that I have experience that's pretty similar to calculating firing data was in WW2. The main big difference we had was an FO (sp4 in this case) with each infantry platoon and a FIST chief ( 2LT) with the infantry company commander, so we could control more missions and were more responsive to what was going on right in front. Each infantry LT platoon leader had an FO from the FA battalion attached to him. It's no problem controlling more than one mission in a battery at once. Gets hectic but we were required to handle two simultaneously. 

Pardon me for being stubborn, but another query: You mention impact muzzle as slightly less than 500 m/s, so let's say 450 m/s. If the fuze has increments of 1/10 sec that would mean that each increment off ideal fuze would either lead to the shell exploading on impact or 45 m too high. So could they time the mission with accuracy within 1/10 sec without human error? Or did they for practical reasons, when doing a long prep bombardment mix different fuze settings to make sure that enough were ideal. But in CM we don't do 30-45 min bombardments with thousands of shells on target. So again, shouldn't we see higher air bursts or less of the current accuracy for the typically shorter missions within the scope of the game.

[Ultradave]

It's not coming straight down. Trajectory is actually pretty low. Just not flat like a rifle, tank gun or naval gun. (gun vs. howitzer).

And no, the time is calculated for the mission. All the guns get the same data. The fuzes were quite reliable. And yes, we know the time of flight to very fine accuracy. The calculations are the same as any ballistics calculation you might have done in high school algebra (with the addition of the other corrections I previously noted). And we don't have to calculate on the spot. It's all tabulated data.

The only time it would be coming (almost) straight down would be a high angle mission (say, to fire over the top of a mountain to the valley behind). Physics tells you that you can ballistically hit the same spot from two different firing angles - one below 45deg and one >45deg. You don't use time or VT for those for exactly the reason you are asking. But that's not a normal mission.

[MikeyD]

Interestingly, artillery timed fuzes pre-date reliable percussion fuzes (early 19th century) and even predate 'bullet' shaped spun shells. T&P combo fuzes were introduced around 1867 so the round would explode on impact if the timed function failed or was set for too long. (Thank Wikipedia for that info )

[rocketman]

2 hours ago, Ultradave said:

It's not coming straight down. Trajectory is actually pretty low. Just not flat like a rifle, tank gun or naval gun. (gun vs. howitzer).

And no, the time is calculated for the mission. All the guns get the same data. The fuzes were quite reliable. And yes, we know the time of flight to very fine accuracy. The calculations are the same as any ballistics calculation you might have done in high school algebra (with the addition of the other corrections I previously noted). And we don't have to calculate on the spot. It's all tabulated data.

The only time it would be coming (almost) straight down would be a high angle mission (say, to fire over the top of a mountain to the valley behind). Physics tells you that you can ballistically hit the same spot from two different firing angles - one below 45deg and one >45deg. You don't use time or VT for those for exactly the reason you are asking. But that's not a normal mission.

Yeah, I realized after the post about the trajectory - was thinking mortars. But I must say that the howitzer shells come down quite steep too IIRC (will look again).