Kinetic Energy Penetrator (KEP)

[Grand_dm]

For background this a munition I added to our campaign, available in all eras. Especially post HELM core after studies on its utility created renewed interest. I promised to share more of our special munitions so enjoy, YMMV.

About

A kinetic energy penetrator (KEP) is a type of ammunition designed to penetrate armor using a solid, high-density projectile. Like a bullet, this type of ammunition does not contain explosive payloads and uses purely kinetic energy to penetrate the target. Early cannons fired kinetic energy ammunition, initially consisting of heavy balls of worked stone and later of dense metals. Although the high muzzle energy allows for greater distance, the damage capability does drop off.

Affiliation: All Houses
BV Weapon Modifier: x1.5
Used By:  Autocannon 20/10

Game Rules:

Adjust range brackets and damage based on the chart below.

Code: [Select]

Type Short              Medium          Long
AC20 1-4, 20-damage      5-8, 15-damage 9-12, 10-damage
AC10 1-6, 10-damage      7-12, 8-damage 13-18, 6-damage


[Daryk]

I'm really not sure how that's supposed to interface with the TL C innovation of hyper-accurate high-rate fire.  That would generally imply a lower round size for standard autocannons...

[DevianID]

Range is more a function of barrel length, which ammo can't really change.  A gun launched missile is a real thing that exists, so might I suggest using the range and damage of a thunderbolt 5 and thunderbolt 10 for this longer ranged lower damage more expensive ammo?

[Daryk]

That would make sense to me.

[Grand_dm]

Range is more a function of barrel length, which ammo can't really change.  A gun launched missile is a real thing that exists, so might I suggest using the range and damage of a thunderbolt 5 and thunderbolt 10 for this longer ranged lower damage more expensive ammo?

Fair enough, we just were looking for a way to use drop-off with a munition. So a KEP (which probably uses a sabot) seemed like a good way to rationalize it.

[Daryk]

I think the missile angle was a way to try to compensate for the drop off.  Physics gives you LOTS of ways to skin this particular cat...

[DevianID]

The base damage dropoff rounds remind me of the heavy gauss rifle, which was always a bit wonky in how quickly it shed damage.  Really, a KE round that keeps the same damage across a longer range makes more sense to me, aka the improved HGR.  Still, the concept of a damage dropoff round is a thing, regardless of what tech enables it.

For BV balance, an ac10 is 123/15 and ac20 is 178/22.  Your 20/15/10 ac20 is a bit over, at 192.  At 18/14/10 damage, the BV is 177/22, for almost perfect BV equal.  For the AC/10, the 10/8/6 is over at 126/16 BV, while 10/8/5 is 123/15, for a perfect BV comparison. 

[Grand_dm]

The base damage dropoff rounds remind me of the heavy gauss rifle, which was always a bit wonky in how quickly it shed damage.  Really, a KE round that keeps the same damage across a longer range makes more sense to me, aka the improved HGR.  Still, the concept of a damage dropoff round is a thing, regardless of what tech enables it.

For BV balance, an ac10 is 123/15 and ac20 is 178/22.  Your 20/15/10 ac20 is a bit over, at 192.  At 18/14/10 damage, the BV is 177/22, for almost perfect BV equal.  For the AC/10, the 10/8/6 is over at 126/16 BV, while 10/8/5 is 123/15, for a perfect BV comparison.

You are correct. The HGR was another inspiration.

When mulling this over I liked the idea of a heavy 'bullet' without a chemical explosive just losing velocity over distance.

[CVB]

A modern APFSDS KE penetrator of good aerodynamic shape loses about 5% of its velocity in the first second of flight after leaving the muzzle. Given that during that second it passes ~1 hex sheet or in other words its BT long range (v₀ between 1600 and 1900 m/s) the OP damage reduction values seem much too drastic.

[Grand_dm]

A modern APFSDS KE penetrator of good aerodynamic shape loses about 5% of its velocity in the first second of flight after leaving the muzzle. Given that during that second it passes ~1 hex sheet or in other words its BT long range (v₀ between 1600 and 1900 m/s) the OP damage reduction values seem much too drastic.

It's hard to try and convert real life munitions into BT, because well GAME, right?

[CVB]

True, but the BTU is also a kind of future history. We need so much head canon gymnastics already that I would prefer not to abuse basic physics principles like gravity, momentum and aerodynamics any more than necessary.
All IMHO, of course :)

[Daryk]

Sadly, BT abuses all of them constantly...  :D

[Hellraiser]

Wouldn't a KEP already be in game as the Armor Piercing ammo w/ the Crit Hits rolls?

Also, Gauss is described as a KEP isn't it?

[DevianID]

I believe the OP was going for a HGR version of the AC shell, which lost damage rather drastically over range too.  Purely a gameplay gimmick.  A more grounded version would be like the iHGR with constant damage.

The iKEP without damage fall off, keeping the same BV, would be a 15 damage ac/20 alternate ammo with range 12 for 178/22 BV--the exact same BV as the base gun.  The iKEP ac/10 with 8 damage to 18 hexes would be 118/15 BV, so a few BV under but with the same ammo BV.  The iKEP also share the gauss and light gauss damage values in addition to matching the base gun's BV, so are a bit more physics realistic.

[Grand_dm]

Wouldn't a KEP already be in game as the Armor Piercing ammo w/ the Crit Hits rolls?

Also, Gauss is described as a KEP isn't it?

It may very well be, it's just what came to my mind when dreaming this up.

[Grand_dm]

I believe the OP was going for a HGR version of the AC shell, which lost damage rather drastically over range too.  Purely a gameplay gimmick.  A more grounded version would be like the iHGR with constant damage.

The iKEP without damage fall off, keeping the same BV, would be a 15 damage ac/20 alternate ammo with range 12 for 178/22 BV--the exact same BV as the base gun.  The iKEP ac/10 with 8 damage to 18 hexes would be 118/15 BV, so a few BV under but with the same ammo BV.  The iKEP also share the gauss and light gauss damage values in addition to matching the base gun's BV, so are a bit more physics realistic.

You are correct, that was my inspiration.

[CVB]

At least one AC20 brand was fluffed as using KEP, the  Zeus-75 Mark IX installed in the MechBuster "fires a four-round burst of hyper-velocity depleted uranium armor penetrators" (TRO3026).