90 replies to this topic

[Gabriel Amarell]

Like many of you I’ve loaded up Mechwarrior 4 and been playing through it again: 1 because I like it, even with all its flaws it’s still a fun title, and 2 not as “training” per-se for MWO but as a way of getting back into mech piloting in general. While doing this I noticed something that I never noticed before, when your mech is being knocked around by enemy weapons fire it makes targeting really problematic. In MW4 it doesn’t seem to make any difference what kind of weapon it is, they all seem to have at least some degrees of knockback. Now, by knockback, I mean that being hit by a weapon causes your mech’s torso to turn and pitch away from where it was pointed prior to the weapons impact, consequently forcing you to readjust the angle to get the retackle back on target.

When I noticed how troublesome it was when used against me I decided to see if it might hamper the cpu generated opponents and sure enough it does. I loaded up Large X-Pulse lasers because they fire rapidly (2.25 sec recycle) and have decent damage per shot (7 dmg/shot) figuring the amount of damage might translate into how much knockback the weapon has. I took my Large X-Pulse toting Awesome for a spin to test my theory and the result was better than I had expected.

Set on chain fire with 4 of the weapons (and 24 heat sinks) I was able to pepper the enemies continuously and it interfered with their targeting significantly. The results got me thinking if I were to take a defensive role in MWO (assuming knockback is similar to MW 4) it might be worth it to load up weapons that fire rapidly and have decent knockback rather than going for the most “powerful” weapons.

It seems to me that knockback effect and the resultant interference with targeting might really be useful in a defensive role, and perhaps in the scout role, if the AC-2/AC-5 were relatively rapid fire with decent knockback they might really let a pilot utilizing them hamper the effectiveness of an opponent, and doing this might partially offset their glairing deficiencies. I would still argue that the AC-2/AC-5 need to be made smaller and lighter, or they need to fire more rapidly, but that’s another topic.

If Energy weapons (PPC not withstanding) had no knockback, and ballistic/missile weapons did, and if knockback truly interfered with targeting as much as it did in MW 4 it could add a defensive element to the game that I think would be great. I know Piranha has already announced knockback, but I for one hope that ballistic weapons really knock you around and make it hard to stay on target, I think it would add weight to some of the smaller weapons that are not traditionally very useful (small AC’s SRM-2, LRM-5?)

[Dr Roshima]

I do not undersatnd why Lazzors should knockback your enemy. Lasers are beams of light resulting to melt the enemys armor because of the heat they produce. There s no kinetic energy involved which could knockback the enemy mech.

Would you "knockback" when i ´d show you a lamp ?

Edited by Romeox, 20 March 2012 - 12:23 AM.

[Duncan Jr Fischer]

I can't see why there should be any knockback from lasers unless they instantly vapor out considerable mass of armor, causing some imbalance (which is not so common for lasers), but there positively should be a knockback from kinetic weapons. Kinetic weapons impact should be stronger, I guess. PPC hit effect is similar to lasers (little to no knockback) but has to interfere with HUD and maybe poke a pilot's view inside the cockpit rather than shake the mech itself. That's my opinion.

Edited by Duncan Jr Fischer, 20 March 2012 - 12:24 AM.

[CCC Dober]

OP: The DPM (damage per minute) approach to defense, requires substantial exposure and armor to work 1vs1. That's not gonna work when you are facing multiples (very likely), unless you have shoulder mounted autonomous AI turrets that can keep them busy (read: throw their aim).

P.S. Knockback received from impacting lasers, as far as I understood it, is related to the ablative armor concept, where damaged armor layers fall off and affect the Mech's center of gravity. It's not so much the laser that is causing knockback, but the way the armor works. If your 10m Mech is suddenly missing 0.5 tons worth of armor from a laser broadside on his front, you can be sure it's gonna unsettle the gyro and make the Mech stumble a bit.

Edited by CCC_Dober, 20 March 2012 - 12:56 AM.

[LordDeathStrike]

beam and pulse lasers should not have a knock back, not enough to notice over the mechs gyros, light has no impact energy since that would require mass X velocity, light has alot of velocity, but zero mass.

now ppc's missiles and ac's, they all have varying effects, missiles go fast have mass and explode, ac shells are heavy and moveing, and getting hit by a ppc is like being struck with lightning, repeatedly.

should ppc's have alot of push? no, they dont have much mass if any, but they should have a tazer effect, literally, mechs have muscle fibers, they will spasm when shocked this hard.

[Hayashi]

The funny thing is that when you're hit by a laser, due to the loss of mass, your 'Mech should pitch forward towards where the laser hit, but traditionally laser knockback was away from the hit location. Hmm.

Anyhow, PPCs are literally Particle Projection Cannons... so I suppose there'd be some effect to getting smacked by it. By lasers should have no movement, or just slight movement towards the hitsite, yup.

And LBX-AC20s should blow the Flea clear on its back.

It'd be interesting to see pilots constantly pepper an Atlas with AC/2 until it can't shoot straight... all things considered it seems like an interesting addition to the tactics light pilots can employ to not be useless after they've already spotted the enemies and/or NARCed them.

[cinco]

only explosive and kinetic weapons should result in any form of knock back or disbalancing. as others have pointed out, lasers shouldn't knock you back.

slow firing long bored cannons should have the most knockback power as the impact is most concentrated, the projectile most heavy, and the kinetic energy most large.

[ChalybsUmbra]

Well, I'm no particle physicist, but these are some numbers I ran through for that PPC. Assume the following:
Proton at near speed of light (from Large Hadron Collider)= 299,792,455 m/s
(Large Hadron Collider) measured relativistic mass of said proton= 1.1822e^-23 kg
Assume one mole of hydrogen -note- this is only about .000101 kg or 1.01 grams originally
1 mole= 6.022e²³ molecules (in this case, hydrogen protons)
momentum = mass x velocity = [(1.1822e^-23) x (6.022e²³)] x (299,792,455) = 2,135,762,520 newton seconds

Okay that doesn't mean much, but as comparison, a legal max weight semi-truck is 36,287 kg (40 tons), and it would need to travel at 131,660.478 mph to reach the same momentum. Or think of it as a 100 ton Atlas traveling at 52,663.7437 mph.

... from 1.01 grams of hydrogen. Again, I'm just a college student not evening majoring close to this stuff, so someone please prove me wrong, because those numbers are ludicrous. But let's try not to emulate this gameplay-wise though.

Edited by ChalybsUmbra, 20 March 2012 - 03:29 AM.

[Hammer Strike]

interesting thread marked for checking up on later

HS

[Hayashi]

AC/2 flies damn fast and far. They're much smaller than AC/20s yes, but they're damn fast, given their range.

There is quite some potential for knockback there, inasmuch as shooting someone with a bullet has stopping power of sorts. Not as much as a hammer to the face, but quite a bit.

I guess my point is that it shouldn't scale linearly with calibre. While I agree that a single AC/20 should have more knockback than a single of anything else currently available, 8x AC/2 should be way more disruptive than a single AC/20 is.

[Hayashi]

ChalybsUmbra, on 20 March 2012 - 03:19 AM, said:

Well, I'm no particle physicist, but these are some numbers I ran through for that PPC. Assume the following:
Proton at near speed of light (from Large Hadron Collider)= 299,792,455 m/s
(Large Hadron Collider) measured relativistic mass of said proton= 1.1822e^-23 kg
Assume one mole of hydrogen -note- this is only about .000101 kg or 1.01 grams originally
1 mole= 6.022e²³ molecules (in this case, hydrogen protons)
momentum = mass x velocity = [(1.1822e^-23) x (6.022e²³)] x (299,792,455) = 2,135,762,520 newton seconds

Okay that doesn't mean much, but as comparison, a legal max weight semi-truck is 36,287 kg (40 tons), and it would need to travel at 131,660.478 mph to reach the same momentum. Or think of it as a 100 ton Atlas traveling at 52,663.7437 mph.

... from 1.01 grams of hydrogen. Again, I'm just a college student not evening majoring close to this stuff, so someone please prove me wrong, because those numbers are ludicrous.

Particle Projection Cannons don't fire at the speed of light. If they did, I'd blow my own 'Mech's arm off should I attempt to fire 2 PPCs from the same arm. They are, however, pretty fast. Given the speeds of travel from MechWarrior 4 (which of course, wouldn't be completely accurate) they would travel at 1000 metres in 2 seconds, or about 500 ms-1. This is WAY slower than the speed of light - about a million times slower, in fact.

Secondly, I doubt they fire only 1 mole of hydrogen.

Given the balancing factors and all, it's not too hard to see how it could have an equivalent momentum impact of a 10 ton arm moving backwards at 2 km/h, depending on how much particles it actually shoots, which won't be enough to rip it off my torso. Yup.

[theaptpupil]

we should definitely have a Kinetic and Ballistic weapons class knock back. that was my favourite thing about MW4

[ChalybsUmbra]

Hayashi, on 20 March 2012 - 03:28 AM, said:

Particle Projection Cannons don't fire at the speed of light. If they did, I'd blow my own 'Mech's arm off should I attempt to fire 2 PPCs from the same arm. They are, however, pretty fast. Given the speeds of travel from MechWarrior 4 (which of course, wouldn't be completely accurate) they would travel at 1000 metres in 2 seconds, or about 500 ms-1. This is WAY slower than the speed of light - about a million times slower, in fact.

Secondly, I doubt they fire only 1 mole of hydrogen.

Given the balancing factors and all, it's not too hard to see how it could have an equivalent momentum impact of a 10 ton arm moving backwards at 2 km/h, depending on how much particles it actually shoots, which won't be enough to rip it off my torso. Yup.

In which case I'm assuming 100 moles, which I think is extremely impressive, and 500 m/s, and normal mass of a proton. I get about 50.8778 newton seconds. Which is your 10 ton arm moving at about 2.276 mph or 3.663 kph. That makes much more sense, and it fits in with the gameplay and canon much better.

[Jehan]

Actually, PPC's particle stream contains kinetic energy, so they generate both knockbak and recoil when firing.

MW4 followed the tabletop rules for knockdown, forcing a check when the mech recieved X amount of damage in a given time, independently from the source of damage.

And regarding lasers forcing knockdowns, since they contain no kinetic energy it seems unlikely to happen, however, if we were forced to find an explanation, we could teorize that once the focused beam pierce through armor (easy for a strong laser, and even easier for a pulse laser), they start to cut myomers and other sensible equipment. Cut myomers maybe would produce a *snap* when they break, similar to internal 'spasms' which not only physically disturbs mech's movement but also could send 'feedback' to the pilot's neurohelmet, making difficult maintaining mech's balance under heavy fire and severe damage.

[Strum Wealh]

Strum Wealh, on 11 March 2012 - 10:02 AM, said:

"Enforcers use big, ten-round clips that are easily slipped into and out of the 'Mech's back."

Additionally, TechManual states (on page 208) that the reason that Ultra Autocannons cannot use any of the special munitions is because "their own magazines are tailored to the high-speed firing modes, which can be dangerous or detrimental to most specialty ammo".

"Mounted on the Quickscell Hetzer Combat Vehicle, this weapon [Ceres Metals Crusher Super-Heavy Cannon (AC-20)] fires shells in the 150 mm range in ten shot bursts."

[EDMW]CSN, on 01 December 2011 - 12:47 AM, said:

Anyway just to add on a few examples

The AC-20 of a Mechbuster is 4 x hyper-velocity depleted uranium armor penetrators (HDUAP) of questionable size. http://www.sarna.net/wiki/MechBuster

The AC-20 of a Hetzer is 10 x 150mm rounds in rapid succession.
http://www.sarna.net...usher_SH_Cannon

While the AC-20 on a Demolisher fires 1x 185mm Chemjet shell.
http://www.sarna.net/wiki/Demolisher

I seriously do not mind if AC were classed as rapid firing, burst or single though (with rotaries and Ultras firing even faster !)
As long the DPS remains the same. It also keeps people guessing all the time.

However burst fire and rapid fire ACs kinda lose the 1 shot big hurtin damage ability, maybe they should be better in keeping the enemy rocking.

There is substantial evidence to support the claim that ACs in BT/MW are clip-fed or magazine-fed weapons, where the listed "ammo per ton" indicates the number of clips or magazines available, where each clip or magazine contains multiple individual shells (ten shells per clip/magazine in the examples of the Enforcer and Hetzer).

Assuming 10 shells per clip/magazine is fairly standard, a rate-of-fire of two shells per second (one shell fired every half-second) is reasonable - with a BT turn representing a 10-second period, the clip/shell would be emptied in 5 seconds, with the replacement of the clip/magazine taking another 5 seconds (with both the ROF and clip/magazine-replacement times decreasing for both the Ultra ACs and Rotary ACs (when they come along) when set to their respective high-ROF modes).
(Additionally, my thoughts on calibers, ranges, and muzzle velocities are detailed here.)

As far as knockback... as the common AC shells are explosive rounds (High-Explosive, Armor-Piercing or HEAP rounds, to be more specific), their primary damage mechanic would be the transfer/conservation of kinetic energy and momentum combined with the concussive effects of an explosion (as opposed to depth of penetration, as with a kinetic energy penetrator).

Again assuming a 10-shell-per-clip/magazine standard:

• AC-2: 45 clips/magazines per ton -> ~450 shells per ton
  
• AC-5: 20 clips/magazines per ton -> ~200 shells per ton
  
• AC-10: 10 clips/magazines per ton -> ~100 shells per ton
  
• AC-20: 5 clips/magazines per ton -> ~50 shells per ton

Since 1 ton = 1,000 kg:

• AC-2 shell = 1000 kg/450 shells = 2.22 kg (4.89 lbs) per shell
  
• AC-5 shell = 1000/200 = 5.00 kg (11.02 lbs) per shell
  
• AC-10 shell = 1000/100 = 10 kg (22.05 lbs) per shell
  
• AC-20 shell = 1000/50 = 20 kg (44.09 lbs) per shell

(Go figure - AC class number ~= mass per shell in kilograms )


Using supposedly-similar real-world weapons as a point of comparison (Yeah, I know... ), I propose the following average muzzle velocities:

• AC-2: ~1500 m/s
  
• AC-5: ~1200 m/s
  
• AC-10: ~900 m/s
  
• AC-20: ~600 m/s

Using those and the per-shell mass, we can calculate the per-shell KE and momentum (p):
AC-2

• KE = 0.5*m*(v^2) = 0.5 * 2.22 * (1,500^2) = 2,497,500 J = ~2.50 Megajoules (MJ)
  
• p = m*v = 2.22 * 1,500 = 3,330 Newton-seconds (N-s)

AC-5

• KE = 0.5 * 5.00 * (1,200^2) = 3,600,000 J = 3.60 MJ
  
• p = 5.00 * 1,200 = 6,000 N-s

AC-10

• KE = 0.5 * 10.00 * (900^2) = 4,050,000 J = 4.05 MJ
  
• p = 10.00 * 900 = 9,000 N-s

AC-20

• KE = 0.5 * 20.00 * (600^2) = 3,600,000 J = 3.60 MJ
  
• p = 20 * 600 = 12,000 N-s

Of note is that the AC-5 shell and the AC-20 shell have the same kinetic energy, but the latter has much more momentum than the former.

As a point of reference, a 1000 kg vehicle moving at 160 kph (44.44 m/s) has approximately 1 MJ of KE and ~44,444.44 N-s of momentum.

Modern armor-piercing shells "tend to have a far thinner body material and higher explosive content (4–15%)".
Assuming BT/MW shells are similarly proportioned and use particularly powerful explosives (like Octanitrocubane (~2.7x more powerful than TNT) or Heptanitrocubane (~1.7x more powerful than TNT) - because they've probably figured out mass-production of such materials):

• AC-2 shell explosive power: 2.37-3.76 MJ
  
• AC-5 shell explosive power: 5.33-8.47 MJ
  
• AC-10 shell explosive power: 10.67-16.95 MJ
  
• AC-20 shell explosive power: 21.34-33.89 MJ

And each of those values represents one shell; most ACs seem to fire in bursts of 4-10 shells...

So, yeah... knockback should be a fairly significant factor in AC-use...

(Also, I suspect that looking up the references for this post, particularly those with regard to the various explosives, has just put me on so many watch-lists... )

Edited by Strum Wealh, 20 March 2012 - 04:28 AM.

[Hayashi]

Jehan, on 20 March 2012 - 03:56 AM, said:

Actually, PPC's particle stream contains kinetic energy, so they generate both knockbak and recoil when firing.

MW4 followed the tabletop rules for knockdown, forcing a check when the mech recieved X amount of damage in a given time, independently from the source of damage.

And regarding lasers forcing knockdowns, since they contain no kinetic energy it seems unlikely to happen, however, if we were forced to find an explanation, we could teorize that once the focused beam pierce through armor (easy for a strong laser, and even easier for a pulse laser), they start to cut myomers and other sensible equipment. Cut myomers maybe would produce a *snap* when they break, similar to internal 'spasms' which not only physically disturbs mech's movement but also could send 'feedback' to the pilot's neurohelmet, making difficult maintaining mech's balance under heavy fire and severe damage.

Though once again, the myomer, if snapping, would cause the movement to occur in the direction towards which the laser was fired, so it'd be more like knock-forward. This, however, is unlikely; for that to be the case the effect can occur only when the laser already penetrates the armour, and would have no effect prior to that. I'd still go for 'no effect' to be easier to explain and code.

ChalybsUmbra, on 20 March 2012 - 03:55 AM, said:

In which case I'm assuming 100 moles, which I think is extremely impressive, and 500 m/s, and normal mass of a proton. I get about 50.8778 newton seconds. Which is your 10 ton arm moving at about 2.276 mph or 3.663 kph. That makes much more sense, and it fits in with the gameplay and canon much better.

If we're talking about 50 N.s or 50 kgms-1, then a 10 ton Atlas arm wouldn't move much. In order to move the arm at 2km/h, or 0.556m/s, we'll need a momentum of 5.56 ton.m/s, or 5556 kgm/s. I'm not sure I follow your calculations...

Each mole of protons weighs approximately 1 gram, so that'd be 100 grams of protons. Not at all bad. Density of air is 1.2 kg/m3 approximately. If we consider an Atlas at 16 metres tall, the size of a PPC that can be mounted on it would likely be about 4m by 0.5m by 0.5m, given reasonable estimates on barrel size and length of cannon, as depicted by drawings of Uziel arms, which I assume are large enough only to hold a single PPC. Thus, actually approximately 1m3. This means we could expect there to be about 1 kilogram's worth of gaseous particles to use as reactant, should no pressure be applied.

If we were to assume that we can ionise and propel the full mass of 1.2 kg of gas forwards at 500m/s, we will obtain only 600kgm/s momentum, when we need 5556.

The only solution to make it possible will be to assume that the PPC first pressurises the gas to at least 10 atm before ionisation and propulsion, which isn't exactly difficult to do. The ionisation part I mean. The propulsion part is way out of current tech.

Strum Wealh, on 20 March 2012 - 04:01 AM, said:

AC-2

• KE = 0.5*m*(v^2) = 0.5 * 2.22 * (1,500^2) = 2,497,500 J = ~2.50 Megajoules (MJ)
  
• p = m*v = 2.22 * 1,500 = 3,330 Newton-seconds (N-s)

AC-5

• KE = 0.5 * 5.00 * (1,200^2) = 3,600,000 J = 3.60 MJ
  
• p = 5.00 * 1,200 = 6,000 N-s

AC-10

• KE = 0.5 * 10.00 * (900^2) = 4,050,000 J = 4.05 MJ
  
• p = 10.00 * 900 = 9,000 N-s

AC-20

• KE = 0.5 * 20.00 * (600^2) = 3,600,000 J = 3.60 MJ
  
• p = 20 * 600 = 12,000 N-s

Of note is that the AC-5 shell and the AC-20 shell have the same kinetic energy, but the latter has much more momentum than the former.



As a point of reference, a 1000 kg vehicle moving at 160 kph (44.44 m/s) has approximately 1 MJ of KE and ~44,444.44 N-s of momentum.

Modern armor-piercing shells "tend to have a far thinner body material and higher explosive content (4–15%)".
Assuming BT/MW shells are similarly proportioned and use particularly powerful explosives (like Octanitrocubane (~2.7x more powerful than TNT) or Heptanitrocubane (~1.7x more powerful than TNT) - because they've probably figured out mass-production of such materials):

• AC-2 shell explosive power: 2.37-3.76 MJ
  
• AC-5 shell explosive power: 5.33-8.47 MJ
  
• AC-10 shell explosive power: 10.67-16.95 MJ
  
• AC-20 shell explosive power: 21.34-33.89 MJ

And each of those values represents one shell; most ACs seem to fire in bursts of 4-10 shells...



So, yeah... knockback should be a fairly significant factor in AC-use...

Given again a 10 ton Atlas arm as a target at which we shoot the AC, we would achieve 3333 ish kgms-1, or 3.333 tonms-1. This would move the 10 ton arm approximately 0.33ms-1 backward, or 1.188km/h. Repeating calculations we obtain 2.16km/h for the AC/5, 4.32km/h for the AC/10 and 8.32km/h for the AC/20. This gives the knockback velocity of an AC 5 a similar, but slightly higher value to that of a PPC, which is within reasonable estimates. And it gives people a reason to use the AC/5 over the PPC when IIRC they have the same damage values, the PPC is lighter, and it has no ammunition restrictions/explosion risk.

I approve of these calculations. Not that a random player's approval matters, but I think we got something going here.

However, this is for a single shell. If we're talking 10 of them AC/20s, your calculations give the weapon the capability to accelerate the Atlas arm at 80km/h, which is faster than the velocity of the entire Atlas itself, while also accelerating the entire Atlas backwards at approximately 8km/h. This basically knocks the Atlas over while the arm flies backwards at an appallingly fast rate.

Therefore, we'd probably have to either drop the size of the AC/20 estimate, or reduce the AC to only 1 shell per fire.

[Ulric Kell]

Withstanding the discussion on how lasers affect knockback I like the OP's idea of this being a defensive tactic. I would assume you'd pair a mech with these weapons alongside another mech with powerful weapon systems to work in tandem. Once to mess their targeting/stabilization and the other to actually destroy them.

[MaddMaxx]

Ulric Kell, on 20 March 2012 - 06:16 AM, said:

Withstanding the discussion on how lasers affect knockback I like the OP's idea of this being a defensive tactic. I would assume you'd pair a mech with these weapons alongside another mech with powerful weapon systems to work in tandem. Once to mess their targeting/stabilization and the other to actually destroy them.

And as noted by the OP himself. When on the receiving end, you can actually hear the Sucking sound it makes. That Sucking sound is the actual FUN being sucked right out of the game.

Edited by MaddMaxx, 20 March 2012 - 06:47 AM.

[FlareUKCS]

Got to be careful the knockback isnt too disruptive as that could make it extremely frustrating for a lot of players who are not so hardcore MW fans... not too much fun stomping around in your badass ride, only to get rattled around so badly you couldnt hit the side of a barn wall with a scattergun. Players would run off to hide in the next CoD or BF that comes out.. which may be good for MW fans, but bad for the bottom line of the Devs.

Say that, I would love to have some serious effects personally, blinding lasers if they hit near the camers/cockpit , smoke from eating a salvo of SRM's, knocked around silly if getting pounded by a AC or Guass... doubt you last long if it was a LongTom
That stuff just gives weight to what is happening in game, makes it more brutal and lends the weapons some impact literally.

[El Loco]

The math you did there is all sound and right... nicely put together. I only wonder about the muzzle velocities you used Strum Wealh. Did you take for comparison weapons of equal range? And your explosive powers are not that high, yet still impressive. 1 ton of TNT has 4.184 GJ (thanks wikipedia... to lazy to do the math myself )... so combining your EP per shell equals 9,48 to 338,9 MJ... which is equivalent to less than 100kg TNT. To put this into perspective... here's a little video of a 500 Lb TNT explosion. I don't know about you all, but I don't want to be in the blast radius

As for the PPC... it should have knockback. I'll try to contribute to the PPC and Gauss knockback later... got to go