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Do Tanks "Recoil" when Hit ?


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GeoMonster #1 Posted Mar 13 2018 - 17:02

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Is it my imagination, or do enemy tanks occasionally "recoil" from a broadside hit (or any other hit).  That is, the enemy tank actually rocks in response to a shell hit.  I've noticed this more at higher tiers when I seem to have fired a ghost shell.  That is, the enemy tank seems to rock due to the hit but there is no damage or verbal feedback from the game.  And no, I don't have a lot of ghost shells, just very occasionally and many times it seems the enemy tank rocks in response to the shell hit, but nothing happens.

 

Thanks.



Blackhorse_One_ #2 Posted Mar 13 2018 - 17:06

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Depends upon the mass of the projectile, relative velocity, and explosive yield, but yes, it does happen.

 

(That's the real-world answer)


Edited by Blackhorse_One_, Mar 13 2018 - 17:49.


Doublenut #3 Posted Mar 13 2018 - 17:15

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think it is eye candy only they can only screw up so many game mechanics at a time

 



Ape_Drape #4 Posted Mar 13 2018 - 17:16

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View PostGeoMonster, on Mar 13 2018 - 17:02, said:

Is it my imagination, or do enemy tanks occasionally "recoil" from a broadside hit (or any other hit).  That is, the enemy tank actually rocks in response to a shell hit.  I've noticed this more at higher tiers when I seem to have fired a ghost shell.  That is, the enemy tank seems to rock due to the hit but there is no damage or verbal feedback from the game.  And no, I don't have a lot of ghost shells, just very occasionally and many times it seems the enemy tank rocks in response to the shell hit, but nothing happens.

 

Thanks.

 

You're not seeing it rock from getting hit. You're seeing it dodge the round like in The Matrix.

Guido1212 #5 Posted Mar 13 2018 - 17:17

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There will always be an effect when two masses collide.  Whether you see it or not is another question.

GeoMonster #6 Posted Mar 13 2018 - 17:18

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So, if the recoil is in fact a game attribute when a shell hits, then ghost shells are probably NOT cause by lag since the shell is actually hitting the enemy tank (per visual observation).

Lesser_Spotted_Panzer #7 Posted Mar 13 2018 - 17:22

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View PostApe_Drape, on Mar 13 2018 - 11:16, said:

 

You're not seeing it rock from getting hit. You're seeing it dodge the round like in The Matrix.

 

Nice!

Ash_Canadian #8 Posted Mar 13 2018 - 18:00

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View PostBlackhorse_One_, on Mar 13 2018 - 11:06, said:

Depends upon the mass of the projectile, relative velocity, and explosive yield, but yes, it does happen.

 

(That's the real-world answer)

 

I concur, espically true when hit from the side by sabot/APCR. The kinetic energy transfer is tremendous.

PaperArtillery #9 Posted Mar 13 2018 - 18:45

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Granted, a modern round (again), but firing range footage of a 120mm M831A1 tracer round vs. an M113 APC. Great example of the energy expended; there's less "recoil"/knockback here because the round penetrates like the vehicle is made of butter (the M113A2 topped out at 38mm frontal armor). The GIF is kinda horrifying for pyrophobes, so I spoiler'd it.

 

https://fas.org/man/dod-101/sys/land/m831.htm

 

https://en.wikipedia.org/wiki/M113_armored_personnel_carrier

 

Spoiler

 

EDIT: fixed the description.


Edited by PaperArtillery, Mar 13 2018 - 18:55.


BillT #10 Posted Mar 13 2018 - 19:35

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I did some simple calculations based purely on conservation of momentum.  If projectile, with mass = mp and velocity = vp, collides with a tank with its own mass mt and velocity vt, and the two objects stick together and wind up moving at final velocity vf, then to conserve momentum:

 

 mpvp + mtvt = (mp + mt) * vf

 

If the tank is stationary, vt = 0.  And since the mass of the shell is negligible compared to the mass of the tank, this all simplifies to:

 

vf = mpvp / mt

 

Suppose an E 100 shoots its 15cm KwK 44 L/55 AP shell at a Sheridan.  The data:

 

Shell mass = 43kg

Shell velocity = 865 m/sec

Sheridan mass = 15,200 kg

Barring friction, the Sheridan would wind up moving at 2.4 m/sec.

But if the target is another E 100 at 130,000 kg, the target would only move at 0.29 m/sec.

Because the targets in fact have extremely high friction, they don't actually move, they just rock.

 

Now, there are some big assumptions that undermine this math.  I've assumed the tank completely stops the shell that hits it. If the shell goes clear through the target, or bounces off, then it retains lots of momentum and the target doesn't rock as much.  I've ignored the fact that in penetrating the armor, the shell converts much of its energy to heat.  So the numbers I calculated are probably high, maybe by a factor of two or more.


But still, I think they justify why the target should rock when it's hit by a big, fast projectile.

 

Bear in mind that the mass of the projectile scales with nearly the cube of the bore diameter.  (The 2.5th power of the bore is reasonably close, and this doesn't apply to APCR or APDS, just normal AP.)  So the impact of smaller-diameter rounds scales down very quickly.  Against the Sheridan, a 90mm M3 gun firing the M82 APC round (11 kg @ 810 m/sec) produces a final velocity of only 0.59 m/sec, and a 76mm M1A1 firing the M62A1 APC round (7 kg @ 790 m/sec) only produces 0.36 m/sec final velocity.  So guns below about 120mm may not produce much of a visible effect against most targets.



Frostblitz20 #11 Posted Mar 13 2018 - 20:24

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In real life back in ww2 tanks getting hit by rounds did kill crew members due to they didn’t have helmets or padding on there heads so recoil led to many tank crews deaths

PaperArtillery #12 Posted Mar 13 2018 - 20:31

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View PostFrostblitz20, on Mar 13 2018 - 14:24, said:

In real life back in ww2 tanks getting hit by rounds did kill crew members due to they didn’t have helmets or padding on there heads so recoil led to many tank crews deaths

 

A lot of the deaths resultant from a lack of head protection was due to spalling, frankly. The whole idea behind a penetrating round is that it, well, penetrates, meaning that it needs to not push the target back and expend unnecessary energy — just like a round from small arms, you don't want to blow the target backwards, you want to put as much kinetic energy in a small enough footprint to punch through and inside to do damage. It's undeniable that with the caliber and mass of AT/AV rounds that the target will likely "recoil" a bit, but AP rounds especially are designed to penetrate with minimal resistance (thus, with modern rounds, sabots are a "silver bullet" that's basically a long dart). See my post above; true, it's filmed at very high speed, but that's an example of ideal AP performance: cuts through with minimal loss of energy and destroys the target with spall, the superheating of the armor on hit, and overpressure in the crew compartment.

 

True, I'm sure some headgear-related casualties were tied to the vehicle being thrown around, but that's more likely in the case of HE/HESH/HEAT rounds, and even then, the cause of death by "recoil" would've been superceded by other causes such as spalling, fire/lung injuries, traumatic blunt force trauma to other parts of the body, overpressure, or what I've heard referred to generally as "SBT" (sudden body translation), meaning an overall "parts of your body are suddenly a foot away from where they were less than a second ago".


Edited by PaperArtillery, Mar 13 2018 - 20:34.


PaperArtillery #13 Posted Mar 13 2018 - 20:48

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Here's another M113 taking a 120mm Rheinmetall DM33 APFSDS-T round: note that it's not an HE round (i.e., no explosives are involved), but the overpressure and kinetic energy converted to heat generated is sufficient to blow out several panels and hatches. The vehicle does rock slightly from the impact, but it's negligible compared to the damage to internal systems and crew (in a real combat situation, obviously).

 

Spoiler'd again for cringe factor.

 

Spoiler

 

Entry and exit points afterwards:

 

Spoiler

 

EDIT: It's APFSDS-T, not just APFSDS.


Edited by PaperArtillery, Mar 13 2018 - 20:49.


Frostblitz20 #14 Posted Mar 13 2018 - 21:27

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AP rounds usely killed due to when a round pens it usely turns into strapnel and carry with it metal from the area it pens turning the inside into a hornets nest of metal. It does also cause a compression effect too.

Also you can’t compare ammo of today to that of ww1-ww2 a lot of changes and advancements have been made. Today it’s rare to take a hit if all the countermeasures work correctly thanks to reactive armor and anti shell systems that blows up the shell before it comes in contact with the armor by shooting a charge at the shell area and exploding.

PaperArtillery #15 Posted Mar 13 2018 - 21:32

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View PostFrostblitz20, on Mar 13 2018 - 15:27, said:

AP rounds usely killed due to when a round pens it usely turns into strapnel and carry with it metal from the area it pens turning the inside into a hornets nest of metal. It does also cause a compression effect too.\

 

Yep. That's what "spalling" is, which is what I already said.

 

View PostFrostblitz20, on Mar 13 2018 - 15:27, said:

Also you can’t compare ammo of today to that of ww1-ww2 a lot of changes and advancements have been made. Today it’s rare to take a hit if all the countermeasures work correctly thanks to reactive armor and anti shell systems that blows up the shell before it comes in contact with the armor by shooting a charge at the shell area and exploding.

 

Not relevant, particularly, because while the rounds have gotten deadlier and more effective, the principle is the same: a vehicle is going to rock somewhat because in the end, its overall "system" of energy is sustaining additional energy from the round, but penetrating rounds are still going to have the same effect on the fighting compartment of the vehicle. Physics are still physics — even reactive armor blowing off a round still has to "absorb" the energy somehow, and it still counts as a hit, just a non-penetrating one, and ask any modern tanker who's been in a vehicle that's taken a round: it's still deafening, still is a palpable impact, and scares the f#@* out of you. To clarify, I'm not a tanker and never saw combat, but I know a lot of people in both category.



Hurk #16 Posted Mar 13 2018 - 21:45

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View PostGeoMonster, on Mar 13 2018 - 09:18, said:

So, if the recoil is in fact a game attribute when a shell hits, then ghost shells are probably NOT cause by lag since the shell is actually hitting the enemy tank (per visual observation).

ghost rounds have always been caused by a disagreement between the world server and the game server. they published information on it a while back:

 

http://ritastatusrep...-explained.html

Short description

The problem is not the servers nor the clients, it's actually a BigWorld engine fault process that begins when the server fails to calculate a penetration value. In layman terms, here's the process (missing a few filler elements such as shell travel time, tank velocity, gun arc, type of shells, etc etc etc. for the sake of simplicity):

- client is driving
- server receives the "drive command" replies back "you are now driving" and sometime later it determines there is an enemy  tank in sight that the client can see, so it sends the data back saying "you have a tank in sight"
- client now sees enemy tank
- server acknowledges the tank is there and all the aiming mechanics occur 
- client shoots at tank
- server acknowledges the client has shot and triggers the reload timer for the client while also processing the penetration value of the shell, angle, RNG (+/-25%), area to damage and determines, if theres a penetration/ricochet or damage to any internal modules (shoot commander's hatch, driver dies! *trollface*) or (shoot driver's compartment, suddenly tank gets tracks damage *trollface v2*) (Insider: actually this is explained by ricochets inside the tank, but ill leave it at that).
- Bigworld engine which is running along the streamline of the server fails to process the client request and delivers a "null"
- Server: hey, but I just sent the data!
- Bigworld: yes and I say it's null, now obey!
- Server: ??? okay ._.

Server sends the ping back with null value: "lel, tank wasn't there". Client displays a ghost shell event in return.

 

 



BillT #17 Posted Mar 13 2018 - 21:49

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View PostPaperArtillery, on Mar 13 2018 - 14:48, said:

Here's another M113 taking a 120mm Rheinmetall DM33 APFSDS-T round: note that it's not an HE round (i.e., no explosives are involved), but the overpressure and kinetic energy converted to heat generated is sufficient to blow out several panels and hatches. The vehicle does rock slightly from the impact, but it's negligible compared to the damage to internal systems and crew (in a real combat situation, obviously).

 

 

Thanks for posting those!  Rocking would be minimal in these cases because the penetrator exited the back side of the target, so it didn't transfer much of its energy to the M113. 



PaperArtillery #18 Posted Mar 13 2018 - 22:01

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View PostBillT, on Mar 13 2018 - 15:49, said:

 

Thanks for posting those!  Rocking would be minimal in these cases because the penetrator exited the back side of the target, so it didn't transfer much of its energy to the M113. 

 

Exactly right. The "recoil" (quotes because it's not really the right word) would be more pronounced if the round didn't penetrate, or stayed within the vehicle, but even with the penetrating component in the GIFs above exiting the other side of the vehicle while maintaining most of its energy, the damage to the fighting compartment would still be catastrophic due to the overpressure, superheated armor, and other miscellaneous spall from the entry "wound".

BillT #19 Posted Mar 13 2018 - 22:02

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View PostPaperArtillery, on Mar 13 2018 - 15:32, said:

View PostFrostblitz20, on Mar 13 2018 - 15:27, said:

AP rounds usely killed due to when a round pens it usely turns into strapnel and carry with it metal from the area it pens turning the inside into a hornets nest of metal. It does also cause a compression effect too.

Yep. That's what "spalling" is, which is what I already said.

 

 

Not exactly.  Spalling is what happens when a round does not penetrate the armor, but hits it hard enough to cause a shock wave that causes a bit of the inner surface to break off and fly away.  It's a different phenomenon from the fragments created by an actual penetration.

 


This image doesn't show normal AP ammo.  It would resemble APDSFS, except it produces more fragments because the AP round is bigger and heavier than the APDS penetrator. (This drawing should show fragments on the HEAT and APDS penetrations, too, but it lacks them.  It was the best image I could find.)

This shows the value of a spall liner.  It won't contain fragments from an actual AP or APDS penetration because the penetrator blows a hole through the liner and the fragments come through with it.  But the spall liner (usually something like Kevlar) can catch the spall from a HESH or HE hit.



PaperArtillery #20 Posted Mar 13 2018 - 22:10

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View PostBillT, on Mar 13 2018 - 16:02, said:

 

Not exactly.  Spalling is what happens when a round does not penetrate the armor, but hits it hard enough to cause a shock wave that causes a bit of the inner surface to break off and fly away.  It's a different phenomenon from the fragments created by an actual penetration.

 


This image doesn't show normal AP ammo.  It would resemble APDSFS, except it produces more fragments because the AP round is bigger and heavier than the APDS penetrator. (This drawing should show fragments on the HEAT and APDS penetrations, too, but it lacks them.  It was the best image I could find.)

This shows the value of a spall liner.  It won't contain fragments from an actual AP or APDS penetration because the penetrator blows a hole through the liner and the fragments come through with it.  But the spall liner (usually something like Kevlar) can catch the spall from a HESH or HE hit.

 

Well, spall does still occur even on a penetration, but it's essentially "overlooked" by the catastropic/fatal damage that the actual penetration causes (i.e., the impact still causes some assorted fragmentation of the armor/hull/whatever around the entry "wound" in addition to the round itself entering the fighting compartment). Spall is still the term for it even on a penetration, but again, compared to the fragmentation of the round itself, the ejected metal solids and slags from the penetration itself, pyrophoric effects (in modern rounds using DU et. al.), etc. makes spall absolutely a non-factor in vehicles being knocked out.

 

EDIT: To clarify, spall is absolutely capable of knocking a vehicle out on its own by virtue of destroying vital systems and/or killing the crew; the above was "in the event of penetration, spall is likely a non-factor".


Edited by PaperArtillery, Mar 13 2018 - 22:16.





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