Competition: Californium 2250

[Toxn]

3 hours ago, N-L-M said:

What kind of array areal densities are you getting?

This sort of thing is typical:

 

~650kg/m2 for the hull front, 1.2m thickness

 

The array design, in case of the (likely) event that I messed up the calculations. From the base outwards:

- 45mm RHA @ 30' from vertical

- 2 layers heavy NERA @ 70' degrees from vertical

- 3 layers light NERA @ 70' from vertical

-1 layer heavy NERA @ 70' from vertical

- 1 layer light NERA @ 70' from vertical

 

Level of protection: 450mm KE, 360/960mm, 0'

 

 

Edit: here is a better optimised version (after reworking the spreadsheet I was using):

- 45mm RHA, 30'

- 3x light NERA, 77'

- 25mm HHA, 30'

- 1x light NERA, 77'

 

Level of protection: 500mm KE, 360/960mm CE, 0'

 

Areal density: ~500kg/m2

Thickness: ~850mm

[Lord_James]

well, this is all ball park, but my new 3.51kg, 760mm long rod (same 740mm rod with a 0.12kg / 20mm long cap), flying at 1850m/s out the muzzle can penetrate (with the 15% segment reduction) 741mm of armor PB, and (using the same penetration ratio as the previous round) 431mm at 2km... as my penetrator is tapered, and the whole thing is sheathed with a cap, are there any other modifiers I should / could put on this? 

 

Edit: Max pressure is 42200 CUP / 47000 psi, barrel length is L/44 (rifled, too), and the charge is separated /semi-combustible similar to 2A46 ammo, 28455 cm³ total capacity. 

 

Edit 2: The low pressure Cockerill Mk.3 has a 30500 psi max pressure (sourced via internet), which would be the cut off point for our precision HEAT, I assume? 

[LostCosmonaut]

One of us is making a math error somewhere, here's my array;

 

25mm HHA at 55 deg from vertical

4 layers of light NERA at 67 deg from vertical

76mm RHA at 55 deg from vertical

 

Total weight is 2740 kg/m2, thickness of 613mm

 

Protects against 500mm KE and 360/960 CE

[Xoon]

1 hour ago, N-L-M said:

Dowrating would solve a lot of the issues, yes.

Opposed pistons have one shaft with a 13-17 deg lead angle to allow good axial scavenging, so they aren't perfectly inherently balanced; at the same time, the individual crankshafts cannot be perfectly balanced in a "straight 5" config, so you have both shafts badly vibrating inside the engine.

Upping the 5TD to 6 cylinders would go a long way to solving some of these problems. And in fact, this is what the Kharkovites did. The 6TD is a more reliable beast (if still not reliable in absolute terms). 

 

That explains it, I only though about the pistons. 

 

I think I will be running with a opposed piston engine, because my special tonk needs to be even more of a special snowflake. 

 

I also did a quick mock up:

 

Weights roughly 10 metric ton, made out of aluminum. For now, purely structural (45mm thick). 

 

 

Also, do we know if the filthy enemies rounds bounce at a certain angle, or penetrate more when angled? 
I remember that the old soviet APFSDS bounced at 75 degrees. 

 

Also, CHA and RHA are equal yes?

[N-L-M]

Enemy rounds can be expected to bounce/fail to fuze at approximately 80 degrees from the normal.

CHA and RHA are broadly equal, yes.

[N-L-M]

1 hour ago, Toxn said:

~650kg/m2 for the hull front

That's approximately 90mm steel LOS equivalent, less than a single NERA-H plate at the stated angle (140mm LOS steel alone), so I strongly suggest you check your math. 

[Toxn]

31 minutes ago, N-L-M said:

That's approximately 90mm steel LOS equivalent, less than a single NERA-H plate at the stated angle (140mm LOS steel alone), so I strongly suggest you check your math. 

Fair enough. If a math error can happen I'm pretty likely to make it so. I'm tired though, so tomorrow.

 

Edit: yeah, there's some kind of concatenated fuckup with how the spreadsheet is calculating mass. My optimised array should be over 1400kg/m2.

[Xoon]

I feel that the hydrostatic powertrain is about ready.

 

Hydraulics:

 

 

Flow schematic:

 

EDIT:
AND OF COURSE I MESSED UP THE HYDRAULICS. 

 

Late nights and pens are a bad combination......

[DIADES]

Power densities and baseline dates.   I think we have inconsistencies in the specified example engines.  The 5TD is specified in its original form but the AVDS-1790 is specified in the 5A version at 908 hp which is a much later development.  The 1960 AVDS-1790 is the 2A as used in the M60A1 which develops 750 hp.  Both engines have later developments - 5TD up to 1050 hp.  Very latest (2000s) AVDS-1790 up to 1,500 hp - that has common rail injection and modern electronics.  Similar story with the 838.  The early version with 850 hp is provided but there are later versions with 950 hp and the peak version has 1,400 hp.  The point I am laboriously making is that the present baseline inflates the mass/volume power density of the AVDS.

[N-L-M]

4 hours ago, DIADES said:

The point I am laboriously making is that the present baseline inflates the mass/volume power density of the AVDS.

The only real difference between the -2 and -5 AVDS was the size of the radiator. Later AVDS versions changed the injection and timing and so on, but the -5 is very close to the -2, to the point where IMO its a no-brainer.

Of course with 20/20 hindsight stuff like RISE would be built in from the start.

[Toxn]

Okay, so after thoroughly failing at numbers, here is a reworked version of the armour calculator:

 

https://drive.google.com/open?id=1Fg4nX85R86fBVpQzkc1WSL0PYejQwAWY

 

The calculator now handles areal density properly (I think) and calculates the effect of active layers correctly (I hope).

Note that the calculator is limited to 5 layers or ERA and 10 of NERA for calculation purposes.

 

Edit: air gap calculations still don't work though.

[Zadlo]

My base so far - I'm thinking about enhancing fuel tanks but it may look ok.

[Toxn]

Brick junior gained weight thanks to my poor grasp of maths, and had to be put on a diet:

All-up weight is now 63 tonnes fully loaded, but the ammunition capacity has been lowered to 30 rounds (20 in the primary ammo rack and 10 in the secondary).

 

I'm at the point where I have to decide whether it's worth slimming it down more, going for a bigger engine or starting on Brick senior. With a stretched AVDS-derived mill the all-up weight will probably be close to 70 tonnes, but the power available jumps to 1205hp. This should provide enough grunt to push over the minimum power-to-weight requirements (Brick jr is currently a hair under). On the other hand, it might be worth stretching out properly and getting that 200mm gun I've been wanting to throw into this competition...

 

Edit: here are the rounds for the 150mm smoothbore gun:

 

- Common: all rounds use a seperate tubular 150x1000mm propelling charge section (semi-combustible with a aluminium or steel case stub). Some rounds include extra propellant in the warhead section. Reload rate is approximately 15 seconds per round.

 

- HEAT-FS (HEDP, steel liner): 545mm RHA penetration, 35kg, 950m/s.

- HEAT-FS (single, copper liner): 610mm RHA penetration, 35kg, 950m/s.

- HEAT-FS (tandem, copper liners, high-precision cones + improved pressing): 250/700mm RHA penetration, 35kg, 950m/s.

- HE-FS: 60mm RHA penetration, 43kg, 850m/s.

- APFSDS (maraging steel): 375mm RHA penetration at muzzle, 5.1kg penetrator, 10.4kg total, 1900m/s (note: due to excessive barrel wear, this round is restricted to a maximum of 3 per combat load).

- APFSDS (maraging steel with 20x21mm tungsten carbide tip): 410mm RHA penetration at muzzle, 5.2kg projectile, 10.4kg total, 1900m/s (note: due to excessive barrel wear, this round is restricted to a maximum of 3 per combat load).

[N-L-M]

On 3/30/2019 at 10:16 PM, LostCosmonaut said:

One of us is making a math error somewhere, here's my array;

 

25mm HHA at 55 deg from vertical

4 layers of light NERA at 67 deg from vertical

76mm RHA at 55 deg from vertical 

 

Total weight is 2740 kg/m2, thickness of 613mm

 

Protects against 500mm KE and 360/960 CE

I'm getting that the precursor, main warhead, and KE threat all poke slightly more than they're supposed to and that the array is defeated by a very small margin in both cases.
Are you using the published K1 equations?
And are you only counting the steel in the NERA towards the LOS feeding component (K2)?

Either of those are minor changes that take the array from "working" to "not".

I'm getting similar density and thickness for the array, so the math there is likely fine.

[LostCosmonaut]

1 hour ago, N-L-M said:

I'm getting that the precursor, main warhead, and KE threat all poke slightly more than they're supposed to and that the array is defeated by a very small margin in both cases.
Are you using the published K1 equations?
And are you only counting the steel in the NERA towards the LOS feeding component (K2)?

Either of those are minor changes that take the array from "working" to "not".

I'm getting similar density and thickness for the array, so the math there is likely fine.

 

I just checked, there were two cells where I typed "$C$1" instead of "$C$2", which caused it to point to the k2 value for ERA instead of NERA for one of the early layers.

 

Cranking up the NERA angle slightly solved the issue, added a bit more mass and thickness but no big deal.

[Toxn]

So I guess I should put up my armour packages too:

 

Hull front/mantlet:

- 10mm HHA, 30' from vertical

- 5 layers light NERA, 70' from vertical

- 25mm HHA, 30' from vertical

- 60mm RHA base, 30' from vertical

- Areal density: 2731kg/m2

- Thickness: 665mm

 

Upper hull sides:

- 15mm HHA, vertical

- 3 layers light NERA, 70' from vertical

- 45mm RHA base, vertical

- Areal density: 1593kg/m2

- Thickness: 376mm

 

Hull roof:

- 10mm HHA, horizontal

- 2 laters light NERA, horizontal

- 5mm HHA, horizontal

- 45mm RHA base, horizontal

- Areal density: 725kg/m2

- Thickness: 137mm

 

Turret superstructure roof (all sloped at ~8' from the horizontal):

- 5mm HHA

- 5 layers light NERA

- 5mm HHA

- 45mm RHA base

- Areal density: 940kg/m2 (measured face on)

- Thickness: 235mm

 

Everything else (turret superstructure sides, pulpit, lower hull sides, hull rear, hull floor) is 45mm RHA.

[Toxn]

So while working out the details for a 200mm gun (which, well, let's just say that you shouldn't bother to load anything other than HE) I had a go at optimising for penetration using minimum muzzle energy. I settled on 465mm of penetration from a steel rod, as an insert could probably then bump it up to 500mm.

 

Anyway, what solver spat out was basically this, loaded hot and capable of firing 47mmx700mm(!) APFSDS. So one the one hand it apparently takes a siege gun to get up to 500mm of penetration using steel. But on the other, I'm not sure if ERA/NERA will work at all on what amounts to a stubby tool-steel telephone pole being thrown at it. So the actual penetration value versus a reactive array might cease to matter. 

[N-L-M]

18 minutes ago, Toxn said:

I'm not sure if ERA/NERA will work at all on what amounts to a stubby tool-steel telephone pole being thrown at it. So the actual penetration value versus a reactive array might cease to matter. 

Considering the reported effectiveness of Kontakt 5 against M829A1 and A2, which are of broadly similar dimensions and made of DU, with the A3 and A4 likely having sacrificial tips to avoid getting similarly wrecked, I'd say that heavy ERA/NERA will likely work against a steel LR of those dimensions.

 

[Toxn]

35 minutes ago, N-L-M said:

Considering the reported effectiveness of Kontakt 5 against M829A1 and A2, which are of broadly similar dimensions and made of DU, with the A3 and A4 likely having sacrificial tips to avoid getting similarly wrecked, I'd say that heavy ERA/NERA will likely work against a steel LR of those dimensions.

 

I don't know. We're talking a 75% thicker diameter here. But again, I don't know.

[Toxn]

40 minutes ago, Sturgeon said:

>not using a 205mm gun with a 105kg full-bore AP projectile

Psh. Amateurs.

Only 105kg? Pffft, what sort of peashooter are you designing?

[N-L-M]

21 hours ago, Toxn said:

35kg

 

42 minutes ago, Sturgeon said:

105kg

The Oversight Committee for Enforcing Absolute Norms (OCEAN) is interested in knowing how these rounds are to be loaded, both onto the vehicle and into the guns.

9 hours ago, Toxn said:

- 10mm HHA, 30' from vertical

- 5 layers light NERA, 70' from vertical

- 25mm HHA, 30' from vertical

- 60mm RHA base, 30' from vertical

- Areal density: 2731kg/m2

- Thickness: 665mm

I'm getting that the areal density is right, but the LOS thickness is off, unless that is thickness from the normal to the array. For LOS thickness I'm getting 740mm or so.

I'm also getting that this array gets poked by the 500mm KE, but not by the 450mm KE.

[Toxn]

10 minutes ago, N-L-M said:

 

The Oversight Committee for Enforcing Absolute Norms (OCEAN) is interested in knowing how these rounds are to be loaded, both onto the vehicle and into the guns.

Brick jr's loading is via an autoloader running from a conveyor on the floor (the ammo rack is built like a vending machine, and dispenses propelling charges and warheads onto the conveyor from 5 vertical stacks) to a vertical rail that punches the warhead and charge in sequentially. The entire assembly is modelled, if roughly, to check clearances.

[Toxn]

8 minutes ago, N-L-M said:

 

I'm getting that the areal density is right, but the LOS thickness is off, unless that is thickness from the normal to the array. For LOS thickness I'm getting 740mm or so.

I'm also getting that this array gets poked by the 500mm KE, but not by the 450mm KE.

The thickness is normal from the array I think.

 

The hull requirements specify 450mm, but I can bump it if needed.

[Xoon]

29 minutes ago, Toxn said:

Only 105kg? Pffft, what sort of peashooter are you designing?

If this power creep keeps up, then by the next competition this will happen:

 

"You call that a cannon? THIS IS A REAL CANNON. Your puny 500mm cannon is nothing!"

[N-L-M]

3 minutes ago, Toxn said:

The hull requirements specify 450mm

The mantlet needs some love, being on the turret and all that.