71 replies to this topic

[NighthawK1337]

Snowbluff, on 11 February 2017 - 10:47 PM, said:

The larger projectile has more drag. That drag causes losses as heat.

Drag is a resultant force. It doesn't mean that all the kinetic energy loss is transformed into heat, a significant percentage of the kinetic energy loss is also transferred in moving the air in the trajectory which also causes drag.

Well assuming that the difference in projectile is large there will be more drag but that doesn't mean that there'll be significantly more friction and heating. Shape has a bigger impact. MWO gauss could be heavier but in terms of volume it wouldn't make much difference in terms of heating because they'll be aerodynamically similar.

Edited by NighthawK1337, 11 February 2017 - 11:07 PM.

[Y E O N N E]

LordNothing, on 11 February 2017 - 10:57 PM, said:

impossible, no. but not from a 5/6 ton weapons system? i know light gas guns can get that fast, but the barrel length would be rather impractical as a weapons system.

Don't actually know whether it requires that long of a barrel. The laboratory light gas guns do, but the experimental artillery piece looked like it was within the expected dimensions for a piece of its caliber, if a bit bulky.

And TBQH, it's kind of ridiculous that something as puny as the AC/2 weighs 6 metric tons. There's got to be something special going on there to justify that mass.

[NighthawK1337]

Yeonne Greene, on 11 February 2017 - 11:14 PM, said:

Don't actually know whether it requires that long of a barrel. The laboratory light gas guns do, but the experimental artillery piece looked like it was within the expected dimensions for a piece of its caliber, if a bit bulky.

And TBQH, it's kind of ridiculous that something as puny as the AC/2 weighs 6 metric tons. There's got to be something special going on there to justify that mass.

Maybe the auto-loader system? It does pull ammo from weird places like the legs. The mechanism might just weigh a few tons given that it also moves a few tons worth of ammo.

[LordNothing]

NighthawK1337, on 11 February 2017 - 11:21 PM, said:

Maybe the auto-loader system? It does pull ammo from weird places like the legs. The mechanism might just weigh a few tons given that it also moves a few tons worth of ammo.

i agree here, if you look at a gau-8 pulled out for maintenance, you notice the ammo drum and feed belts are bigger than the gun itself. now throw in belt switches, multiple magazines, and power transfer linkages and you got some real bulk to deal with.

Edited by LordNothing, 11 February 2017 - 11:31 PM.

[Snowbluff]

Yeonne Greene, on 11 February 2017 - 10:56 PM, said:

Not necessarily true. Geometry matters. A lot.

NighthawK1337, on 11 February 2017 - 11:03 PM, said:

Drag is a resultant force. It doesn't mean that all the kinetic energy loss is transformed into heat, a significant percentage of the kinetic energy loss is also transferred in moving the air in the trajectory which also causes drag.

Well assuming that the difference in projectile is large there will be more drag but that doesn't mean that there'll be significantly more friction and heating. Shape has a bigger impact. MWO gauss could be heavier but in terms of volume it wouldn't make much difference in terms of heating because they'll be aerodynamically similar.

Consider that we know the mass and velocity of the gauss round. Now, tell me how much drag/the shape of the projectile if it only goes a kilometer.

[Snowbluff]

Probably Not, on 11 February 2017 - 11:53 PM, said:

Just a bit of a sidenote about ranges in Battletech: they're completely bonkers. Don't try and make sense of them. For example: there is no reason a RL MG would have a sub-200m effective range.

Less facetiously, I always figured the ranges presented we the effective ranges against battlemech armor, due to it's spectacular hardness and resilience before ablating.

[NighthawK1337]

Really weird wording. I did the math for energy with basic approximations if that's what you're looking for.

Snowbluff, on 11 February 2017 - 11:50 PM, said:

Now, tell me how much drag/the shape of the projectile if it only goes a kilometer.

Assuming Ferrous ammunition.

Iron specific heat = .450 J/g
Iron Incandescence temperature = 480 Celsius
Projectile weight = 10ammo/ton * .5 (assuming half is sabot weight) = 50kg
Kinetic Energy = 50kg * 2000^2 = 200000000 Joules
Energy needed to raise projectile temp by 1C = .45*50000 = 225000 Joules
Change in temp assuming 5% conversion to heat = .05*200000000/225000 = 88.88* Celsius

It'll only glow if it leaves the barrel at about 390 Celsius, which is weird if it's a gauss rifle since only railguns have problems with barrel friction. Assuming thermal equilibrium with the surrounding at most 110 C at Terra Therma, you need like +25% energy conversion which is unrealistic.

Even 5% energy loss to heat is too much. In real life only about >1% is lost through heat during flight. Most of the kinetic energy is lost by the transfer of kinetic energy to the air. Not transformation to heat.


This is a simplified equation using only simple Thermodynamics with generous approximations.
A better formula would be to get the initial speed and downrange speed of the projectile, then subtract it to get the change in energy. And probably use a real life Ballistic coefficient to go along with it. But then it'll even have less chance of glowing.

CryEngine doesn't support changing projectile speed while in mid flight(I think) so the best we can do is approximate in percentages instead of measuring the change in speed then getting the energy loss.

Edited by NighthawK1337, 12 February 2017 - 12:25 AM.

[NighthawK1337]

All these railgun talk made me remember this guy.




Some more videos.






DAMN, that muzzle flash looks just like what we have in MWO.

And the sounds in the last one. really really close.

As we can see, no glowing projectile but lots of muzzle sparks and really loud.

Edited by NighthawK1337, 12 February 2017 - 12:42 AM.

[jjm1]

I went looking for a MW2 gauss screenshot to be a smartass and found a dopelganger thread: https://mwomercs.com...nd-gauss-rifle/

personally, I think Gauss should leave a visible trail on some cloudy/foggy maps, that would be neat. Also a sound overhaul.

[Lily from animove]

Hit the Deck, on 11 February 2017 - 03:57 AM, said:

The nickel-ferrous melon ball doesn't fly fast enough that the friction between it and the air heats up the projectile so it glows.

like in mw3? it was a green mini ppc back then iirc

[Vellron2005]

If you ask me, something flying that fast would definitely distort air.. and should be able to be traced that way..

[Mystere]

Vellron2005, on 14 February 2017 - 03:28 AM, said:

If you ask me, something flying that fast would definitely distort air.. and should be able to be traced that way..

Show me the math, please.

Edited by Mystere, 14 February 2017 - 08:05 AM.

[NighthawK1337]

Mystere, on 14 February 2017 - 08:04 AM, said:

Show me the math, please.

It doesn't need math. Anything that moves through a fluid distorts said fluid. Even when just walking you distort the air around you.



It's just more noticeable when a fast moving object does it because it leaves behind a cavitation.

Further reading:
http://physics.stack...eally-look-like

Edited by NighthawK1337, 14 February 2017 - 02:40 PM.

[Mystere]

NighthawK1337, on 14 February 2017 - 02:38 PM, said:

It doesn't need math. Anything that moves through a fluid distorts said fluid. Even when just walking you distort the air around you.



It's just more noticeable when a fast moving object does it because it leaves behind a cavitation.

Further reading:
http://physics.stack...eally-look-like

Ahem!

It's already barely noticeable when you're looking almost in-line to the trajectory of the projectile and are anticipating the shot. I doubt it will be really noticeable under battlefield conditions, especially when you're busy looking at something else.

Edited by Mystere, 14 February 2017 - 02:47 PM.

[NighthawK1337]

Mystere, on 14 February 2017 - 02:47 PM, said:

Ahem!

It's already barely noticeable when you're looking almost in-line to the trajectory of the projectile and are anticipating the shot. I doubt it will be really noticeable under battlefield conditions, especially when you're busy looking at something else.

It's more noticeable with a larger and faster moving projectile.

That is a just 30 caliber, flying about 850m/sec at about 45g and I can already see it. A 100kg moving projectile twice that speed would even leave contrails.

[Saint Scarlett Johan]

Probably Not, on 11 February 2017 - 11:58 PM, said:

Well... maybe, I guess.

AC ranges are derped as **** though. We're talking about a system that superseded RL modern-day tank cannons (which are called Rifles in BT and are so useless it's funny). Pretty sure the Abrams' 120mm is effective to multiple km - could be wrong though.

EDIT: Yes, I know these ranges come from the Tabletop and it was all in the name of balance. I know.

Snowbluff, on 11 February 2017 - 11:56 PM, said:

Less facetiously, I always figured the ranges presented we the effective ranges against battlemech armor, due to it's spectacular hardness and resilience before ablating.

There's a ruleset (Total War I think) that basically increases the ranges to everything 5x the CBT ranges.

But that's a reasonable assumption to make, as a 125mm AP round fired from the 2A46-M5 is a fairly harmless to an M1 Abrams at 2000m but absolutely lethal to M109A6 SPH. That's how I've always viewed the ranges in CBT at least.

[Saint Scarlett Johan]

Yeonne Greene, on 11 February 2017 - 11:14 PM, said:

And TBQH, it's kind of ridiculous that something as puny as the AC/2 weighs 6 metric tons. There's got to be something special going on there to justify that mass.

I just assume it's the feed linkages, autoloader mechanisms, mounting hardware, weapon casing, etc. since something like the M2HB is about an 80lb HMG alone and the tripod for it is around 45lbs.

[LordNothing]

Probably Not, on 14 February 2017 - 08:07 AM, said:

Not really. What you MIGHT see is a small vapor cone (and you wouldn't see that even on certain maps), but beyond that you probably wouldn't see much at all. https://en.wikipedia...wiki/Vapor_cone

You SHOULD, however, absolutely hear that bad boy breaking the sound barrier multiple times over. (except maybe on HPG Manifold.)

dont get me started on the thermodynamics of hpg manifold. its all wrong.

[NighthawK1337]

LordNothing, on 14 February 2017 - 05:00 PM, said:

dont get me started on the thermodynamics of hpg manifold. its all wrong.

Yeah, by all means there should be no heat transfer without a medium like air. But then "Laser Heatsinks"... what's up with that.
It's like adding a sci-fi word to a mech word and hoping it means something. Like quantum carburetor or microverse battery. Schwifty.

[LordNothing]

NighthawK1337, on 14 February 2017 - 05:50 PM, said:

Yeah, by all means there should be no heat transfer without a medium like air. But then "Laser Heatsinks"... what's up with that.
It's like adding a sci-fi word to a mech word and hoping it means something. Like quantum carburetor or microverse battery. Schwifty.

i think its a form of sublimation cooling, but then again the laser is going to make more heat. laser ablates a hot brick of metal or some other heat carrier. i dont see it as very heat efficient. its sort of like regenerative cooling in rocket engines, where you take the heat out of the bell and combustion chamber by pumping the liquid hydrogen around it. then the heat goes out the nozzel with the exaust, keeping the engine from melting.

other ways to get heat out of the mech is to evaporate coolant, or through ground coupling (provided the ground is colder than your mech). you would need extra coolant (as if heat sinks had ammo). you can also use radiators for radiative cooling, but that involves a large bulky surface area that doesn't fit on a mech very well. also if hpg is that bad, vitric would be impossible.

Edited by LordNothing, 14 February 2017 - 06:48 PM.