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Old 08-14-2020, 10:03 PM   #41
Rupert
 
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Default Re: using spaceships for battletech-style tactical mecha combat

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Originally Posted by ericthered View Post
How many armor systems did you use? what values where you expecting?
Eight armour systems, as 40% of displacement as armour was fairly typical of a battleship. I assumed three would be spread over the hull as plating and light splinter protection. I assumed that the other five would be the side and deck armour, and cover about 2/3rds of the ship's length. The sides and ends would be three times thicker than the deck, and the bottom of the ship would have no armour other than the plating.

This gave just 1.4n inches for the 'unarmoured' ends and the bottom, about 4.7 inches for the deck, and a little over 11 inches for the sides and fore and aft bulkheads. This was without counting the x1.4 multiplier Pyramid 3/24 would give.

For a 30,000 tons full load battleship (which means a WWII superdreadnought) this is very roughly right but including the x1.4 multiplier, which it should get (cruisers of the period of under half the displacement were often almost as big as battleships, simply because they carrier so much less armour), this becomes far too much.
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Old 08-14-2020, 11:00 PM   #42
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Default Re: using spaceships for battletech-style tactical mecha combat

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This gave just 1.4n inches for the 'unarmoured' ends and the bottom, about 4.7 inches for the deck, and a little over 11 inches for the sides and fore and aft bulkheads. This was without counting the x1.4 multiplier Pyramid 3/24 would give.
Let me see if I can follow.

You get 150 DR (human scale) armor over a third of the ship per system. You took three systems and spread out that armor evenly, which comes out to an even 150 DR over the whole ship. So far so good.

Then you take 5 Systems, each giving 300 DR on one facing. we divide this between 9 two-thirds facings, one of which is the deck, and four on each side. That gives us an additional 250 DR for each of the 9 sections, so a 400DR deck, and a 1150 DR sides.

What size of shell should this armor resist?
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Old 08-14-2020, 11:31 PM   #43
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Default Re: using spaceships for battletech-style tactical mecha combat

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Let me see if I can follow.

You get 150 DR (human scale) armor over a third of the ship per system. You took three systems and spread out that armor evenly, which comes out to an even 150 DR over the whole ship. So far so good.

Then you take 5 Systems, each giving 300 DR on one facing. we divide this between 9 two-thirds facings, one of which is the deck, and four on each side. That gives us an additional 250 DR for each of the 9 sections, so a 400DR deck, and a 1150 DR sides.

What size of shell should this armor resist?
Actually, I assumed it was streamlined, so DR100 per system per section.

Also, I assumed a deck four times the area of a side. Counting the ends (1/4 the area of a side), and smearing the armour all over, it came to DR785 for the sides and end bulkheads, DR328 for the armoured deck, and DR100 everywhere else.

Using Pyramid 3/34's rules for 'Armor and Volume', this should be multiplied by x1.4.

This is a little thinner than the thickest parts of a Queen Elizabeth-class battleship's belt (but the belt would be much deeper than the Queen Elizabeth's was), with deck armour a bit thicker and more uniform. As it was a slight upgrade from an Iron Duke's it was intended to protect against the expected performance of the 13.5" APC shells of the time (and the higher velocity but smaller 12" shells of the latest German battleships).
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Old 08-16-2020, 06:17 AM   #44
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Default Re: using spaceships for battletech-style tactical mecha combat

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Actually, I assumed it was streamlined, so DR100 per system per section.

Also, I assumed a deck four times the area of a side. Counting the ends (1/4 the area of a side), and smearing the armour all over, it came to DR785 for the sides and end bulkheads, DR328 for the armoured deck, and DR100 everywhere else.

Using Pyramid 3/34's rules for 'Armor and Volume', this should be multiplied by x1.4.

This is a little thinner than the thickest parts of a Queen Elizabeth-class battleship's belt (but the belt would be much deeper than the Queen Elizabeth's was), with deck armour a bit thicker and more uniform. As it was a slight upgrade from an Iron Duke's it was intended to protect against the expected performance of the 13.5" APC shells of the time (and the higher velocity but smaller 12" shells of the latest German battleships).
I don't think 785 DR will hold up against 12 inch shells. That's 30 cm. Using spaceships numbers, thats 450 dice of damage. A more conservative estimate based on high-tech numbers gives 300 dice of damage. And that's without armor peircing effects, which anti-ship shells should arguably have.
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Old 08-16-2020, 09:35 AM   #45
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Default Re: using spaceships for battletech-style tactical mecha combat

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I don't think 785 DR will hold up against 12 inch shells. .
<shrug> DR 785 is 11 inches and change of RHA. That is a reasonable armor belt for a heavy combatant is not the biggest of the war.

Such ships in WW1 and II do not actually have a great record of bouncing heavy shellfire. Engagements tended to be either long exchanges where no one could hit anyone else or bloody shambles.
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Old 08-16-2020, 09:36 AM   #46
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Default Re: using spaceships for battletech-style tactical mecha combat

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I don't think 785 DR will hold up against 12 inch shells. That's 30 cm. Using spaceships numbers, thats 450 dice of damage. A more conservative estimate based on high-tech numbers gives 300 dice of damage. And that's without armor peircing effects, which anti-ship shells should arguably have.
Historically it's about right. Using Spaceships you're getting shells that are much faster than historical ones, which would be hitting at 1/2 a mile per second and less. Yes, they'd count as AP, but they would also often be at 1/2D range or more.

DR785 will protect against 112d(2), which is a SS 30cm shell at 1/2 mps muzzle velocity at 1/2D range.

It's in the right ballpark.
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Old 08-16-2020, 10:30 AM   #47
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Default Re: using spaceships for battletech-style tactical mecha combat

In addition, any military spacecraft should be using Hardened Armor. One reason why shells and missiles are so effective is that they can suffer point defense. When we are talking about attacks with missiles, each turn could involve the attacker wasting millions of dollars of missiles against the defender every turn.
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Old 08-22-2020, 08:38 PM   #48
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Default Re: using spaceships for battletech-style tactical mecha combat

I'm sorry for taking so long to reply to this, a lot has come up. But I do think the conversation is worth continuing.

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<shrug> DR 785 is 11 inches and change of RHA. That is a reasonable armor belt for a heavy combatant is not the biggest of the war.

Such ships in WW1 and II do not actually have a great record of bouncing heavy shellfire. Engagements tended to be either long exchanges where no one could hit anyone else or bloody shambles.
Its 11 inches and change if 70 DR is a reasonable value for steel. I'm not convinced that it is. The Bismark had 12 inch armor and when they investigated the wreck they found dent marks from 14 inch shells fired at fairly close range--- they just hit the main armor.

I believe battleships do have a fair record of bouncing hits from inferior foes, including the last generation of battleships and the main belts a good record of bouncing hits from other battleships. . Jutland had 25 ships go down, including 4 battlecruisers and 4 other large ships, but not a single battleship went down on either side. The Battle of Denmark strait had a not dissimilar result, with the battlecruiser getting sunk, but neither battleship actually getting through the armor belts: hits were to other areas.

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Historically it's about right. Using Spaceships you're getting shells that are much faster than historical ones, which would be hitting at 1/2 a mile per second and less. Yes, they'd count as AP, but they would also often be at 1/2D range or more.

DR785 will protect against 112d(2), which is a SS 30cm shell at 1/2 mps muzzle velocity at 1/2D range.

It's in the right ballpark.
I don't have Doug's sheet (I need to get my hands on it one of these days), but when I crunched the numbers in high tech a while back the higher-velocity weapons generally did their dice of damage equal to their caliber in mm. A 12 inch/ 30 cm shell in high tech with the high velocity guns should do around 300d of damage. 150d(2) is enough to get through the armor without much fuss.

That's applying 1/2d range to some very large guns, and I made my case for the main belt being able to take those hits above.

I'm also a bit worried about the armor being able to take the explosive force of a shell. 785 DR can resist about 225d of damage, that's around 220 lbs of RDX via the numbers in high-tech -- a quarter of the historical weight of a 12-inch shell.
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Old 08-22-2020, 09:04 PM   #49
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Default Re: using spaceships for battletech-style tactical mecha combat

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I'm sorry for taking so long to reply to this, a lot has come up. But I do think the conversation is worth continuing.


Its 11 inches and change if 70 DR is a reasonable value for steel.ll.
It's fundamental canon in Gurps that the type of steel armor known as Rolled Homogenous Alloy gives DR 70 per 25mm of thickness. If you're trying to dispute that you're going to be off by yourself in a fairly distant area of House Rules land.

Perhaps you were trying to say that battleships (and quite possibly all battleships everywhere) were armored in a better grade of steel thna RHA. If so I believe the burden of proof is upon you. Specifically I believe you will need to document al of the thickness of the armor belt, the material of that belt and the degreee to which it was superior to RHA.

Ah sorry, I didn't catch you're final sentence about explosives until after I posted this the first time. Total weight of shells certainly exceded 220 lbs but there's a very large difference between total weight and weight of filler. The rule of thumb i know for artilery shells is that weight of filler for regular HE will be only approx. 10% of the total weight. Only 5% for APEX.

So your 880 lbs 12 inch shell has only 88 lbs of filler if it's HE and less than that if it's APEX. You'd have to up to a 16 incher such as used by the Iowa-Class to get a little over an effective 220 lbs of filler in HE.
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Old 08-22-2020, 09:44 PM   #50
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Default Re: using spaceships for battletech-style tactical mecha combat

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It's fundamental canon in Gurps that the type of steel armor known as Rolled Homogenous Alloy gives DR 70 per 25mm of thickness. If you're trying to dispute that you're going to be off by yourself in a fairly distant area of House Rules land.
ehh, its less of canon and more of a rule of thumb that has been used in a fair number of high and ultra tech armor situations, especially ones trying to hew closer to reality. It may have been raised to a sort of cannon as a lone number in a few pyramid articles. I do mean to dispute that number, because I find it frequently gives underwhelming results, especially for things that ought to be bouncing rather impressive attacks.

However, searching does seem to indicate that battleship armor was superior to RHA.

Quote:
Ah sorry, I didn't catch you're final sentence about explosives until after I posted this the first time. Total weight of shells certainly exceeded 220 lbs but there's a very large difference between total weight and weight of filler. The rule of thumb i know for artillery shells is that weight of filler for regular HE will be only approx. 10% of the total weight. Only 5% for APEX.
HE shells are only 10% Explosive? that's news to me. I had thought they had substantially more of their weight as explosive. Huh, the things you learn.
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