7 replies to this topic

[Zakatak]

I got really bored one stormy night, so I decided to figure it out.

The PPC, as stated in canon can "take off 2 tons of standard military-grade armor in 3 shots", or 667kg of armor per shot. However, ferrofibrous armor is 12% stronger then standard armor, so a PPC would be able to melt away, when rounded, about 585kg of FF.

Besides "damage", no unit is given concerning the energy discharge of weapons. Since FF reacts the same to all types of weaponry, a set amount of energy will break or melt amount of mass regardless of whether energy or ballistic weapons are used. The Heavy Gauss Rifle fires 250kg slugs that do 25 "damage" at short range. Using CBT ammo rules, and MW4 as a reference point for velocity, I got...

Kinetic Energy = Half Mass x Velocity Squared
Ke = (.5)(250)(2400)^2
Ke = 720MJ (or 720 million joules)

The standard PPC however does 10 damage, which translates to about 288MJ. That means it takes 288 million joules to melt 585kg of FF armor, or, when generously rounded up, about 500MJ to melt a ton of it. Cast Iron is the a good metal for comparison. The energy to bring iron to its melting point, or 1811 K, is around 13800J/mol, and a mol of iron is 55.85g or so. Approximately 247.1 J/g, or 247 MJ/t.

Energy to melt 1 ton of iron: 247 MJ (247000000 joules)
Energy to melt 1 ton of FF: 500MJ (500000000 joules)

Ferrofibrous is only 2.02x stronger then iron, which is weird considering that it is a weave of titanium, steel, and diamond. FF, considering that it is equally "good" in all areas, you could also say that it has a Tensile Strength of 404 MPa, since Cast Iron has a tensile strength of 200 MPa (1 million pascals).

So basically, it is way way way weaker then it should be. It isn't even half as strong as titanium. Peace out.

Edited by Zakatak, 10 April 2012 - 06:38 PM.

[Evedro Solais]

I don't remember enough from Chemistry and Physics to argue not that I need to and your math looks solid. However the way I see it is that standard armor is ablative, meaning it is designed to absorb energy and melt to prevent internal damage. I suspect it dissipates the energy in such a way that it prevents the energy from boring straight through, resulting in a much greater loss of armor mass than you expect.

[Monky]

Armor most likely has baffles built in to it. Specific structures designed to deflect or mitigate the direct damage output.

Also, many things in the MW/BT universe are technically impossible/highly impractical, but that doesn't stop it from being fun!

Edited by monky, 10 April 2012 - 07:02 PM.

[Gunmage]

In lore, it was stated that mechs use not homogenous metal armor, but composite metal-ceramic armor. Also, this amount of energy would not melt armor, but evaporate it at the point of hit, and blast away surrounding armor with deformation forces. Even if I'm wrong, gauss lugs surely don't MELT armor. So your calculations are somewhat off.

Also, when talking about armor strength, you should look not only at its heat capacity, but at its elasticity, slug stopping effect, its capability to retain defensive capabilities after being damaged. So there must be more to Ferro-Fibrous =)

I still don't get why they weave diamonds there. It's one of the most brittle minerals on Earth.

[Der Kommissar]

The tabletop rules are necessarily abstract, and I caution against using the video games - especially Mechwarrior 4 - as a reference point.

If you're wondering how tough Battletech stuff is, I suggest going and bothering Cray over at the official forums. Guy's a materials engineer and, if I remember right, has put pen to paper more than once to describe how hard things hit and take hits in Battletech.

[Helmer]

Yeah.... Uhhh ... That looks about what I was thinking .... Uhh ..I see you carried the thing and divided by the other thing. Good job.




Cheers.

[BerryChunks]

thats 12% more than tanks get. Ideally, people would see the idea of battletech as materials and mechanics that are better but harder to come by set onto a very mobile legged tank as opposed to track or wheel (or hover lulz) tanks. all the special equipment and other parts required to run a mech at full capacity are rare enough or expensive enough, that producing them on a mass scale for regular tanks would be problematic at best. It's simpler and easier to make some really good machines that can take out mediocre machines rather than making all those mediocre machines (the tanks) just a little bit better.


It's the same reason the U.S. has expensive fighter jets and bombers and can keep buying them, yet can't afford to give body armor to all of its infantry.

tanks in BT are like current era infantry in terms of power and importance. mechs fall somewhere between jet and tank.

Gunmage, on 10 April 2012 - 07:23 PM, said:

In lore, it was stated that mechs use not homogenous metal armor, but composite metal-ceramic armor. Also, this amount of energy would not melt armor, but evaporate it at the point of hit, and blast away surrounding armor with deformation forces. Even if I'm wrong, gauss lugs surely don't MELT armor. So your calculations are somewhat off.

Also, when talking about armor strength, you should look not only at its heat capacity, but at its elasticity, slug stopping effect, its capability to retain defensive capabilities after being damaged. So there must be more to Ferro-Fibrous =)

I still don't get why they weave diamonds there. It's one of the most brittle minerals on Earth.

for the same reason we use diamonds on saws to cut things. And I'm pretty sure hypersonic slugs melt armor. It causes explosions on hitting metal in the first place, you're talking a lot of energy and the obvious friction of passing through the material.

if there was one thing I could change about this game, TT and mechwarrior, it'd be that guass rifles pass completely throuh mechs, possibly doing even less damage than a regular bullet, like FMJs against people with no body armor. The corollary being that they have a high chance of scoring a critical or ammo explosion.

Edited by BerryChunks, 11 April 2012 - 03:54 PM.

[Hawkeye 72]

Where to begin

Zakatak, on 10 April 2012 - 06:27 PM, said:

I got really bored one stormy night, so I decided to figure it out.

The PPC, as stated in canon can "take off 2 tons of standard military-grade armor in 3 shots", or 667kg of armor per shot. However, ferrofibrous armor is 12% stronger then standard armor, so a PPC would be able to melt away, when rounded, about 585kg of FF.

I'll go along with this for now.

Quote

Besides "damage", no unit is given concerning the energy discharge of weapons. Since FF reacts the same to all types of weaponry, a set amount of energy will break or melt amount of mass regardless of whether energy or ballistic weapons are used.

Damage isn't really a unit and cannot be used. This is because your second statement is false. The reactionary forces on a structure will vary based on the application of the force. Obviously a PPC will not cause a force similar to a ballistic projectile or a missile. This is why you have different types of munitions for modern weapons.

Quote

The Heavy Gauss Rifle fires 250kg slugs that do 25 "damage" at short range. Using CBT ammo rules, and MW4 as a reference point for velocity, I got...

Kinetic Energy = Half Mass x Velocity Squared
Ke = (.5)(250)(2400)^2
Ke = 720MJ (or 720 million joules)

The standard PPC however does 10 damage, which translates to about 288MJ.

I would like to know how you used MW4 as a reference and decided upon the mass of a gauss slug. But what you have now done is taken the theoretical kinetic energy of the projectile of one weapon, spread out that energy per an undefined unit of "damage" for that weapon, and then applied that standard to a completely different weapon that uses a completely different method of application of its force.

Quote

That means it takes 288 million joules to melt 585kg of FF armor, or, when generously rounded up, about 500MJ to melt a ton of it. Cast Iron is the a good metal for comparison. The energy to bring iron to its melting point, or 1811 K, is around 13800J/mol, and a mol of iron is 55.85g or so. Approximately 247.1 J/g, or 247 MJ/t.

Energy to melt 1 ton of iron: 247 MJ (247000000 joules)
Energy to melt 1 ton of FF: 500MJ (500000000 joules)

Your comparison here fails because you assume all the projectiles energy is instantly converted to thermal energy and transferred in its entirety to the armor. Armor quality is not based upon the melting point of the material of the armor. It's based upon how it distributes and handles the force of an incoming projectile. Area of impact is very much a factor, Bullet proof vests don't melt upon being impacted by a bullet. The projectile itself deforms as well as the armor.

Quote

Ferrofibrous is only 2.02x stronger then iron, which is weird considering that it is a weave of titanium, steel, and diamond. FF, considering that it is equally "good" in all areas, you could also say that it has a Tensile Strength of 404 MPa, since Cast Iron has a tensile strength of 200 MPa (1 million pascals).

So basically, it is way way way weaker then it should be. It isn't even half as strong as titanium. Peace out.

Understanding this is just fiction and not science, logic should tell you that if a presumed material is a weave of titanium, steel, and diamond and its only twice as strong as cast iron, then perhaps you are the one who made the error. Tensile strength is a measure of the highest point on a stress-strain curve. While the relationship for the material remains constant for a material, this constant does not apply when comparing materials. Therefore to say FF has a tensile strength of 404 MPa based upon the tensile strength of cast iron is very wrong.