Competition: Californium 2250

[Toxn]

@N-L-M What is the mass and thickness-effectiveness of light and heavy NERA?

[N-L-M]

Pinning a single number is difficult due to the dynamic interaction of the armors with the penetrators; the effectiveness in terms of penetration "eaten up" by the armor is therefore also dependent on the threat impacting. See Appendix 1 for details on armor protection estimation.

[Toxn]

16 minutes ago, N-L-M said:

Pinning a single number is difficult due to the dynamic interaction of the armors with the penetrators; the effectiveness in terms of penetration "eaten up" by the armor is therefore also dependent on the threat impacting. See Appendix 1 for details on armor protection estimation.

Hmmm. It doesn't mention NERA though.

[N-L-M]

Quote

Light and heavy NERA use the same k1 curves as their ERA equivalents.K2 is 2 for ERA and 1.5 for NERA.

Note that the NERA sandwiches are thicker but require less open spacing between them to function.

[Lord_James]

I don’t understand the difference between K1 and K2 in those calculations. 

[Toxn]

7 minutes ago, N-L-M said:

Note that the NERA sandwiches are thicker but require less open spacing between them to function.

Thanks

[N-L-M]

10 minutes ago, Lord_James said:

I don’t understand the difference between K1 and K2 in those calculations. 

K1 is the dynamic portion that breaks up the penetrator, reducing its overall penetration by a certain factor, and is modelled as being angle-dependent.

K2 is the erosion of the penetrator by feeding material into its path, and is modelled as being constant.

[Collimatrix]

Cell D33 of the specs xls, the text is cut off.  What is the frontal armor array of the upgraded Norman supposed to be?

[N-L-M]

That's the plain old Norman: 60mm HHA- 20 cm gap- 200mm RHA LOS. The dedication to defeating speculative future Cascadian perfidy ahead of time is, however, lauded.

[Collimatrix]

The Cascadian entity can make thicker HHA than we can, have tungsten monobloc darts, and are putting the finishing touches on beam riding atgms?

 

Well, fuck.

[Sturgeon]

6 hours ago, Lord_James said:

To the Honorable Diane Feinstein VIII and other nobles related to this contest, 

 

I have questions about the metallurgy of DPRC. As my company, Song Heavy Machine Works, has only experience in large agriculture and multi-axle transport vehicles, along with the civilian grade materials used in them, we are in need of additional information pertaining to the questions I have given below, if that is acceptable for release. In regards to weapon and vehicle design expertise, we have contacted the ‘Mann Ltd’ corporation (Ms. Hillary Mann was kind enough to send several designers, as well as research, to assist our efforts), so information pertaining to those aspects does not need to be sent. My questions are as follows: 

 

1. Are there Uranium or Tantalum mines within our territories; and if so, what is the level of technology for refining those metals? 

 

2. Are these high hardness steels brittle or are they alloyed well? What kind of alloying materials would we have available for armor grade plates? 

 

3. Is face hardened armor available for use, or is the industry / processes not developed? 

 

I may send additional queries, but for now these are our biggest questions relating to the new heavy tank. Long live the DPRC, and long live the Feinsteins! 

 

Sincerely, 

 

Song Liu-Haack, CEO and Lead Designer of Song Heavy Machine Works. 

 

Shoulda made your last name Yee. @RobotMinisterofTrueKorea

[Sturgeon]

43 minutes ago, Collimatrix said:

The Cascadian entity can make thicker HHA than we can, have tungsten monobloc darts, and are putting the finishing touches on beam riding atgms?

 

Well, fuck.

 

Fear not, our gender-neutral industry will produce something their patriarchal technology can't ever hope to match! It'll be a crushing success, just like the Mojave Agricultural Project!

[Collimatrix]

OK, I am doing some basic derived-spec number crunching based on the requirements thus far:

 

The widest possible tracks are tracks that stretch out all the way to the very edges of the vehicle, or the 4m maximum.  The track center to track center distance is the width between the track edges minus the track width (unless you're using asymmetrical tracks... which you probably shouldn't).

 

If we go with 800mm wide tracks (tiger combat tracks were 725mm) at maximum width, the target 1.5 length to width contact ratio gives us 7.68 square meters of contact area.  With the maximum weight of 120 tonnes, that comes to a Nominal Ground Pressure (NGP) of 153 kN/M².  The ground pressure requirements are specced in Mean Maximum Pressure (MMP), which is about 1.8x-3x NGP, depending on details of road wheel and track configuration.  But even with that lower bound (which would almost certainly require interleaved road wheels), that's well above the threshold requirement.

 

If we bump it up to meter wide tracks (that's like, fucking twice as wide as most tanks have) and the threshold track contact ratio, that gives us 10.8 square meters of contact, which means an NGP of 109 kN/M², which is a bit high, but is within the bounds of sanity.  But then we're only allowed four pieces of side skirt armor, and they need to pack on to the vehicle in such a way that they don't violate the height or width requirements.

 

So,

 

Conclusion Number One: It's actually very hard to max out the weight requirement without maxing out the ground pressure requirement first.

 

If you go for a max-weight vehicle, get ready to use some shenanigans like hugenormous side skirts, or transportketten, or extra road wheels that are lifted above the ground so that they don't count for the contact length but do count for the ground pressure (TOG II did this).

 

 

Next, I took a look at the protection of the Cascadian Entity's Norman MBT.  The reference protection is given as 60mm of HHA (how do the infidels have better armor science than Scientologists?!  We're really good at science!  It's in the name!), a 20mm air gap, and then 200mm of RHA.  So, working backwards, 60mm HHA definitely counts as thick enough to invoke the spaced armor rules.  So we have main armor (subtractive), air gap (multiplicative), and HHA (subtractive).  The air gap is 200mm, which gives it an exponent of 2 against the base protection of 1.05 for KE threats, which means it blunts KE threats to down to 90.7% effectiveness.  Multiply the recipricol of that by 200mm, and we get 220.5mm, and add 120mm (60mm *2 because it's HHA), and we get a final protection of 340.5mm vs KE and 362mm vs CE.  For KE, the Californian gun technology sounded slightly better than the U-5TS.  So, something along the lines of early 2A46 ammo should do the trick.  So, basically a gun along the lines of an L11 or Soviet 125mm firing fairly primitive APFSDS should meet the requirement.  For CE, this is easy-peasy.  If the Californian gun-fired heat can penetrate 5 charge calibers, 362mm can be poked with a 72.4mm charge.  Accounting for shell wall thickness, something like a 20 pounder (84mm) firing HEAT should kill the Norman just fine.

You know, right up until they rush ERA kits to the front.

 

Conclusion Number Two:  It's way easier to meet the lethality requirements with a HEAT-firing weapon than it is with an APFSDS-firing weapon, provided that the Cascadian Entity doesn't slap reactive armor on their tanks to make themselves overnight immune to them.

 

If you want to be a total memelord, you could arm your tank with a KwK 36... that fires HEAT-FS rounds.

[Collimatrix]

OK, I have further questions:

 

 

1)  What is the actual penetration of the ATGM and RPG threats?  It looks like it got truncated in the spreadsheet.

 

 

Edit: NVM, I see that this information is in the OP.  The RPG is 250mm and then 500mm penetration and the ATGM is 360mm and then 960mm penetration.  Goddamn but that's mean.

 

2)  How exactly do the .50 cal SLAP, DPICM and 155mm HE threats work?

 

 

3)  How do tandem warheads interact with NERA?  If the precursor warhead penetrates into a NERA element, is that element considered "expended?"

[N-L-M]

2 hours ago, Collimatrix said:

But then we're only allowed four pieces of side skirt armor

4 pieces requiring a crane.

Components under 25 kg (like Kontakt 1 bricks, for example) are not limited in number.

2 hours ago, Collimatrix said:

2)  How exactly do the .50 cal SLAP, DPICM and 155mm HE threats work?

DPICM- 40mm HEAT, 4 CD= 160mm pen.

.50 cal SLAP

30mm at 750m

35mm at 500m

40mm at 250m

45mm at 50m

155mm HE fragments:

40mm at 15m

45mm at 10m

50mm at 5m

HE may be assumed to be airburst, both fragments and SLAP ignore dynamic effects of armor (k1) but not LOS feeding (k2).

Will be added to the spec soon.

2 hours ago, Collimatrix said:

If the precursor warhead penetrates into a NERA element, is that element considered "expended?"

Yes.

[Toxn]

Can I mention that the hardest thing for me right now is keeping the width under 4m?

[DIADES]

5 hours ago, Collimatrix said:

.

 

If we go with 800mm wide tracks (tiger combat tracks were 725mm) at maximum width, the target 1.5 length to width contact ratio gives us 7.68 square meters of contact area.  W

 

The rule of thumb 1.5 is just that, a rule of thumb.  It dates to the 50s and there was work in the 80s that continued to advocate it in public domain material.  It is the outcome of a calculation that has several simple parameters.  The most critical of these relate to the structural limits of the soil/sand whatever that the vehicle is maneuvering on.  The magic number can go a high as 3 depending on the soil data used.  Does not correlate well with experiment and the experiments are limited to very hard flat ground.  I reckon the professionals have their own metrics.  I calculate LEO 1 to be 1.85 - comfortably over the 1.5 limit.  I don't recall the users complaining about LEO1 maneuverability!  Recent publications also show that number of road wheels has an effect.  More road wheels = better theoretical maneuverability.  Track tension also important, lower is better.

[DIADES]

Stowed kills.  Being able to penetrate a given target at a given range is one thing, being able to hit it in the first place is another.  Agree, the 2A46 is up to the job from a round performance POV, but 4k?  Anybody have any data on accuracy at that range?  It will be probabilistic which will directly feed into how many rounds need to be carried to meet a particular stowed kills goal.  20 is of course the only rational goal....

[N-L-M]

9 minutes ago, DIADES said:

Stowed kills

The stowed kills requirement is for the given number of rounds, with a Phit over 50%. 

So if we assume for example a M60A1 carrying 20 APFSDS, which have 50% Phit rates against Norman-sized targets at 2km, it counts as 20 stowed kills.

[DIADES]

4 minutes ago, N-L-M said:

The stowed kills requirement is for the given number of rounds, with a Phit over 50%. 

So if we assume for example a M60A1 carrying 20 APFSDS, which have 50% Phit rates against Norman-sized targets at 2km, it counts as 20 stowed kills.

OK, just to be certain.  In this case, 20 stowed rounds = 20 stowed kills?

[N-L-M]

Yes, for rounds with a Phit above 50%.

For rounds with less than that, they count as less, by the number required to get a Phit of 0.5.

So if we have HEAT rounds with a Phit of 0.3, the chance that of 2 rounds at least one will hit is 1-(0.7*0.7)=0.51.

So every 2 HEAT rounds carried count as 1 stowed kill.

[DIADES]

All good  - where are these hit probabilities from?

[Toxn]

@N-L-M Can you give the equations used for the graphs in appendix 1?

 

I have some optimisation I want to try out...

[N-L-M]

Somewhat optimisitcally modified from the numbers in the TRADOC bulletin for the T-62.

[N-L-M]

6 minutes ago, Toxn said:

@N-L-M Can you give the equations used for the graphs in appendix 1?

 

I have some optimisation I want to try out...

Sure, I'll post them later.