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Transfer of Projectile Momentum Energy to Soft Target (Human)
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I think that a huge opportunity for BI to take a step forward with regards to realism, in either ARMA 3 or ARMA 4, would be to develop a system of momentum energy transfer from a moving projectile i.e. bullet to a soft target.

IRL the energy that bullets dump into their targets is really very large;

Muzzle energy for standard speed 5.56 is around 1700 Newton meters and you can almost double that for 7.62 to around 3400Nm.

This is a huge energy with regard to a humans standard weight. For the 5.56 it is the equivalent of having a 170kg weight attached to a meter long lever which is attached to the body at the site of impact and for the 7.62, similar except with a 340kg weight.

Very few humans alive can stay standing unsupported with such torques applied to them.

I think therefore this is an opportunity for BI to develop their realism further by introducing this force transfer into game, even in a reductivist system which sacrifices accuracy of calculation for speed of calculation.

One thing I find missing in ARMA is the "first hit advantage" i.e. in a firefight the guys who land the first hits would typically knock over their enemy, or at least totally skew their aim, or cause them to momentarily drop their weapons even if the rounds are caught by body armor (most high quality armor these days will defeat 7.62 even at close ranges).

I think this area is really something BI could use to take another step in front of other offerings within the milsim gaming sphere.


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DisasterMaster set Category to Engine.Dec 11 2015, 7:36 AM
DisasterMaster set Reproducibility to Always.
DisasterMaster set Severity to None.
DisasterMaster set Resolution to Open.
DisasterMaster set Legacy ID to 1071807123.May 8 2016, 1:18 PM
Moach added a subscriber: Moach.May 8 2016, 1:18 PM
Moach added a comment.Dec 12 2015, 4:57 AM

This is valid only as long as the victim completely stops the projectile all but instantly

this would be maybe the case of a soldier with substantial body armor that would not shatter, but completely absorb the energy of the impact.

yet modern body armor is made to dissipate as much energy as possible, and not all the momentum of the is transferred directly, as it most unusual to land a hit at such a right angle (in which case, even body armor might fail depending on conditions)

in any case where the projectile does not decelerate almost instantly, the basic equations for energy transfer are largely unfit - without armor, a 7.62 round will almost always result in a fairly gruesome exit wound -- 5.56 often has higher velocity, and with a lesser area it exits the target even more frequently

so not all the energy in the bullet-victim system is transferred kinetically at the point of impact, which is why it is in fact reasonable a person who is not killed could remain standing from a physics standpoint alone

also -- the OP's math did not account for the added weight of gear a soldier would carry... also, in combat it is not wise to stand upright too much, which lowers the torque arm as well...

some modded versions of the M82 .50cal rifle DO actually deliver enough power to lift a target off his feet and land his expired remains several feet behind himself... those are pretty fun to try in the arsenal (and some MP servers DO allow those as well)

also very much noteworthy -- how come doesn't the shooter flip backwards himself according to your logic?

the recoil energy acting on a gun and being absorbed by the shooters arms will almost certainly exceed the total momentum of a projectile onto its target, after having travelled through air friction and leading-shock compression (bullets go supersonic, air will compress before giving way at that speed, hence that "crack" when they go by, a tiny sonic boom)

if the shooter can fire and not topple on his back, the target can conceivably receive the round and remain upright

the M82 mentioned earlier is fitted with a very beefy recoil damper system - it is also not meant for firing whilst standing up (bipod and prone, lest lots of hurt to him behind the buttstock)

and lastly - this can only be verified for certain by way of experiments, of course -- yet I don't think it'll be easy trying to find test subject volunteers

PiepMGI added a subscriber: PiepMGI.May 8 2016, 1:18 PM

totally agree with this ticket which should be as feature request. There are somethings to do here because AI's continue to fight, aim and keep their skill even if they are drastically wounded (say damage 0.7).

Moach added a comment.Dec 12 2015, 6:01 AM

the basis for the concept here by itself may be logically unsound - however the gameplay implications of the "first shot advantage" mentioned is perfectly valid

this is a fact, even if not because of the kinetic exchanges taking place as claimed - the physics at the receiving end of projectile energy transfer may not hinder a soldier's ability to fight back per se -- but "getting shot" definitely will

once shot, the AI almost instantly resumes trying to kill you back - much like an arcade shooter character who still has "more in the health bar" to keep going as if nothing happened

once shot, an AI character should be some several moments impaired, if not completely unfit to fight (or even move) for the remainder of the engagement, and/or the rest of his shortly-ending life... whichever comes first

it's not very realistic how they continue to shoot seemingly undisturbed after being struck - if anything, at least it does look like the recovery is much too quick to be believed

ceeeb added a subscriber: ceeeb.May 8 2016, 1:18 PM
ceeeb added a comment.Dec 12 2015, 7:03 AM

Newton meter is a measure of torque. Joules is the unit you are after.