American militarism pre-WW2 and the Ultimate Battleship

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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by Terry Duncan » 18 Feb 2021 21:37

It was the 12,000lbs Tallboy that sank the Tirpitz, and it could reliably penetrate 12" of steel. The Disney Bomb, the 4500lbs rocket propelled bomb, could penetrate 16" of armour. The Grand Slam is a 22,000lbs bomb, which struck at near supersonic speed so good luck with keeping those out. If it didnt cause catastophic damage inside the ship it would be pretty likely to exit the bottom of the hull and explode under the keel in some circumstances, an almost certain broken back for the ship. They were working on radio guided versions too.

https://en.wikipedia.org/wiki/Grand_Slam_(bomb)

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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by T. A. Gardner » 18 Feb 2021 22:36

Terry Duncan wrote:
18 Feb 2021 21:37
It was the 12,000lbs Tallboy that sank the Tirpitz, and it could reliably penetrate 12" of steel. The Disney Bomb, the 4500lbs rocket propelled bomb, could penetrate 16" of armour. The Grand Slam is a 22,000lbs bomb, which struck at near supersonic speed so good luck with keeping those out. If it didnt cause catastophic damage inside the ship it would be pretty likely to exit the bottom of the hull and explode under the keel in some circumstances, an almost certain broken back for the ship. They were working on radio guided versions too.

https://en.wikipedia.org/wiki/Grand_Slam_(bomb)
Well, if those didn't do the job you could always up it to the 42,000 lbs. T-12 Cloudmaker bomb. This was the American version of a super-sized Tallboy. There was even a planned 100,000 lbs. version that never was made!

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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 18 Feb 2021 22:37

Terry Duncan wrote:which struck at near supersonic speed
320 m/s, which is only 62% of a plunging 16in shell's velocity (39% kinetic energy factor).
Terry Duncan wrote:good luck with keeping those out.
Luckily it's not a matter of luck; it's a physics problem susceptible to analysis. Steel doesn't know the difference between bombs and shells; heavy penetrator bombs like Grand Slam and Tallboy probably behave largely like shells.

Per the best empirical research, penetration is proportional to:
  • Weight^.55
  • Diameter ^-.65
  • Velocity^1.1
Using the W/D/V deltas between Tallboy and Grand Slam, the latter should be able to penetrate ~16in of steel.

So the megaship should have no problem keeping a Grand Slam out of the citadel/girder. The problem is one of velocity: bombs just aren't as fast plunging shells; thus why a 12,000lb Tallboy has significantly less penetrating power than 2,700lb naval shell.

Beyond the citadel a Grand Slam would do a lot of peripheral damage. Multiple Grand Slam hits would certainly destroy the megaship's CV capabilities, for instance.

But good luck hitting a 40kn target with such a bomb, which has to be dropped from >20,000 ft to have great penetrating power.

Additionally, any bomber carrying a Grand Slam is going to be flying quite slowly. Against the megaship concentrated heavy AA (including 1,000 18in guns), you're going to lose most of whatever heavy bomber force is dispatched.

To trade the (small) risk of repairable damage to megaship against hundreds of heavy bombers and expensive Grand Slam bombs would be efficient.
Terry Duncan wrote:explode under the keel in some circumstances, an almost certain broken back for the ship.
This is also a question that requires some engineering analysis. As I'm not an engineer, let's consider crude scaling effects:

Whether an explosion breaks a ship's back is matter of the force of the explosion and residual strength of the hull girder. While the 660lb warhead of a G7e torpedo could break the back of 10,000-ton merchant ship, against a 3.85mil ton megaship you'd need a 254,100lb warhead for the same effect.

While it's probably true that not all 660lbs are required in the baseline G7e/merchant case, if only a 300lb warhead is required you'd still need >50t of warhead to cripple the megaship.

...and that's assuming the megaship's hull girder isn't excessively strong on account of its dual role (as I suspect it is).
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 18 Feb 2021 22:43

T.A. Gardiner wrote:Well, if those didn't do the job you could always up it to the 42,000 lbs. T-12 Cloudmaker bomb.
Once again, we have some means of analysis and don't need to rely on pictures.

Using the formulas referenced above and assuming the Cloudmaker is a straight escalation of the Tallboy to 42,000lbs, I get 18-19in of penetration for the Cloudmaker.

The 100,000lb bomb is up to 24-25in, depending on assumptions about terminal velocity. That's possibly capable of penetrating 30in of high-tensile construction steel (25.5in armor equivalent).

So if the megaship is operating in an environment against 50-ton bombers, it will need to reinforce its decks. That would be part of its 1960's upgrade, I suppose.
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by T. A. Gardner » 18 Feb 2021 23:45

Even if it failed to penetrate whatever armor was there, it would almost certainly crack and damage it sufficiently to spray splinters and fragments on the far side, and then still detonate. Since it is carrying 17,600 lbs. of RDX for a charge, there's going to be one big earth shattering kaboom! at the receiving end in any case.

Then there's the Hydrobomb. While this didn't proceed beyond some testing, GALCIT did enough research to get it to prototype. This is a 1,300 to 3,200 lbs. bomb with a 600 to 1250 lbs. warhead that was hydrodynamic and propelled by a rocket motor, including underwater. It would be released at a distance and then enter the water and travel on a reliable trajectory somewhat like a torpedo but at much higher speed (70 to 100 mph underwater).
That too will leave a mark...

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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by OpanaPointer » 19 Feb 2021 00:23

The Doolittle bombers were parked along the center line of the ship in an overlapped configuration. When it came time to launch they were herringboned back aft. Their main landing gear was "barely onboard" according to some of the crews.
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 19 Feb 2021 00:46

T. A. Gardner wrote:
18 Feb 2021 23:45
Even if it failed to penetrate whatever armor was there, it would almost certainly crack and damage it sufficiently to spray splinters and fragments on the far side, and then still detonate. Since it is carrying 17,600 lbs. of RDX for a charge, there's going to be one big earth shattering kaboom! at the receiving end in any case.
Re 22k lbs Grand Slam, splintering doesn't seem likely. A shell/bombers possessing only half the power required for penetration isnt likely to cause spalling. This is like expecting 8in hits on Yamato to do so. Furthermore, ductile armor is less likely to spall: this is one of the advantages of using ductile construction steel instead of brittle armor. Even if splintering occurs, it's not catastrophic. Maybe you can knock out one of 15 turrets with a lucky hit? IMO the prospect of hitting a 40kn ship - even a huge one- from >20k feet is negligible. The formation's bomb-release timing is a simple arithmetical problem, in the 30 seconds between bomb release and intended impact a 40kn target will be half a mile from the aiming point. The megaship would swerve as the formation approaches the aiming point, requiring a massive formation to reform and make another run. All the while it'd be being decimated by heavy AAA. You'd be lucky to trade 500 heavies for a single non-lethal hit on megaship.

Re KABOOM! so what? KABOOM! The ship sails on. Meanwhile you've lost hundreds of heavy bombers to megaship's AAA.

I find it odd that our typically Allied-disposed friends are analyzing non-lethal threats to megaship as if creating these threats were economically cheap or even feasible for the Axis. America spent $3bn on the B-29 program, something similar would be required of Germany/Japan to have a slight chance of non-lethal damage to the megaship.

Had megaship merely forced Japan/Germany to develop and expend hundreds of heavy bombers against her, that alone would justify her cost.

Remember the question I'm investigating regards the economic use of resources.
Last edited by TheMarcksPlan on 19 Feb 2021 00:48, edited 1 time in total.
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by Richard Anderson » 19 Feb 2021 00:47

Terry Duncan wrote:
18 Feb 2021 21:37
It was the 12,000lbs Tallboy that sank the Tirpitz, and it could reliably penetrate 12" of steel. The Disney Bomb, the 4500lbs rocket propelled bomb, could penetrate 16" of armour. The Grand Slam is a 22,000lbs bomb, which struck at near supersonic speed so good luck with keeping those out. If it didnt cause catastophic damage inside the ship it would be pretty likely to exit the bottom of the hull and explode under the keel in some circumstances, an almost certain broken back for the ship. They were working on radio guided versions too.
Actually, the calculated penetration of homogeneous armor plate for a Tallboy was 6.6 inches. For the Grand Slam it was 9 inches. Of course, that was the penetration for an intact bomb and fully function fuze, which means in the first case, after burrowing 6.6 inches into the plat, the tail fuze would activate and set off a 4,880 pound charge or RDX and in the second case, after the 9 inches 9,200 pounds of RDX would go off.

That was all calculated for any altitude of 15,000 feet, since a higher drop altitude would result in a higher striking velocity, but while it might marginally increase penetration, it would also make it likely the case would deform, reducing penetration, and resulting in a low-order or no detonation.

https://ww2aircraft.net/forum/attachmen ... pg.249666/
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 19 Feb 2021 02:38

A bit more on carrier operations:

The base point is that a megaship's carrier operation would differ fundamentally in the following respects:
  • 1. Megaship possesses at least two runways capable of operating independently (probably three). The two main runways hang partially above the waterline beam, completely free of centerline guns and superstructure.
  • 2. Megaship possesses ample topside space to spot aircraft even if all runways are in use.
  • 3. Besides topside spotting space, megaship possesses a "deck loader" beneath the main runways hanging above the waterline hull. This is a crude but protected space abutting upper hangar decks into which planes can be rolled from the hangars. From the deck loader is a 5% gradient ramp to topside; presumably AC can taxi up this ramp (see diagram).
  • 4. The two side runways are at least 2,000ft long. As the ship can do 40kn, and as this distance is around the takeoff/landing ground runs for land-based aircraft, the megaship can launch land-based AC when sailing with the wind except in typhoon-like conditions (when no enemy flying will occur anyway).
  • 5. Due to square/cube effects, megaship's hangar capacity is practically unlimited relative to even its large airfield capacity: using 20% of the 2.3mil GRT hull gives ~60 CV-equivalents in hangar volume (Essex class hangar was 654x70x18ft). As the ship can't operate 60x an Essex-class CV (6,000+ AC), the cost-benefit analysis of plane size versus plane quantity shifts towards larger and more capable planes.
Due to factors 1-3, the biggest constraint on typical WW2 carrier operations does not apply: the megaship can continuously and simultaneously spot/launch/recover airplanes. Even when under air attack, the "deck loader" can continue spotting the next strike under bomb-proof protection.

Due to factors 4 & 5, the megaship can operate planes with longer range and/or greater capability per plane. It would, for instance, board several Catalina amphibious planes for aircrew rescue and long-range reconnaissance. It would operate P-38ish long range fighters in addition to F4F's. B-25's would comfortably take off and land (the larger planes requiring sailing into the wind).
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 19 Feb 2021 03:41

The characteristics of a megaship addresses most of these points already, but to circle back...
T.A. Gardner wrote:Yes, you can have too many aircraft aboard a carrier, as well as too few. The USN found the optimal size was to have 3 or 4 strikes worth of aircraft aboard ship and size the carrier to that.
Optimal size differs fundamentally if the carrier has space to spot/launch/recover simultaneously. The operative constraint moves closer to airfield capacity for a land-based aerodome - the takeoff/landings per hour of the runways.
T.A. Gardner wrote:The strike size is the number of planes you can launch before you have to clear the deck to allow the last strike to land. That cycle time dictates how many aircraft you can have aboard that are usable.
Again, this constraint is not operative if spotting/landing/launching can be done simultaneously on separate decks and via separated runways.
T.A. Gardner wrote:As you can see, the size of the plane on an Essex class nearly overwhelms the flight deck. It would be difficult to carry many aboard and their deck space for launches and landings would eat up a lot of room that could be used with smaller planes.
Again, not applicable to megaship. With at least 60x the hangar space, stowage is not the operative constraint.

If three runways can each launch/land one plane every 15 seconds, total plane throughput capacity could be up to 720 planes/hour. That limits the feasible operating group to maybe 2,000 or so planes (~3 hours of launching/landing time each on a day when the full group is used. In a 12-hour daylight period that allows 6hrs for combat missions and/or cushion).

With 60x the hangar capacity of Essex, megaship could carry 6,000 planes. You could hold a large portion of spares for a sustained attritional campaign with the extra space and/or much larger planes than normal. P-38ish long range fighters for recon and air superiority, for instance.

The virtue of having longer-range land based planes and "normal" shorter-range carrier planes is that you can launch a maximal strike that consists of several hours of deck output: the long-range bombers loiter while awaiting the short-range planes, the long-range fighters conduct a forward air superiority sweep over the enemy carrier group (and strafe any assembling planes on deck). Then once everyone is aloft, you strike the enemy carriers with 1,000 planes. The long-range planes can stay aloft and land after the short-range planes. P-38 and B-25 could stay aloft all day, for instance, with SBD's, Avengers, and F4F takeoff/landings sandwiched between P-38/B-25 airfield operations.
T.A. Gardner wrote:So, it's unlikely the USN would willingly want to build a huge budget busting carrier just so they could launch medium bombers. There is no real practical value in that.
Well that's not the case - medium bombers are a side-benefit of megaship rather than its raison d'etre. The megaship is cost-efficient as a BB and transporter alone, the ability to carry and operate a massive air arm is a marginally cheap side-product. Taking all the benefits in the aggregate, the project seems efficient given sufficient foresight about U.S. global warfare (a big if).
T.A. Gardner wrote:Better to get two smaller carriers with usable air wings that are flexible and can carry out a range of missions. The other value in that is you now have two targets not one. If the mega CV is damaged and unable to launch you have no air power. If one of two of your smaller carriers is damaged you still have 50%+ of your air power good to go.
I'm agnostic as to whether the megaship would be cost-efficient solely as a CV.

The proper comparison, however, is not to two CV's. As discussed above, megaship - even when only part CV - should be able to operate at 10-20x a normal CV's number of airplanes and better ones to boot. It will be immensely more survivable and possess practically unlimited operating range.

If the megaship costs $2.5bn that's the equivalent of ~35 Essex-class ships. On CV value alone, megaship probably loses on that analysis.

Most of megaship's cost relates to its gunnery, however. It might be "only" $1bn if just a CV while possessing additional CV capability beyond the hybrid model. If that's the case, it's probably better than a dozen or so Essex's, especially if the choice is, say, 10 CV's and a megaCV versus 22 CV's. As part of a fleet that includes 10 other CV's, the megaCV's extra hangar space constitutes a virtually inexhaustible source of spares. It would also act as super fleet oiler, giving the other CV's practically unlimited range.
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 19 Feb 2021 05:18

Richard Anderson wrote:Actually, the calculated penetration of homogeneous armor plate for a Tallboy was 6.6 inches. For the Grand Slam it was 9 inches.
Thanks for the cite. I was being generous/lazy in assuming the proffered Tallboy figure as true and working from the formulas to escalate its size.

To be fair to the anti-mega case, however, I should note that the either Tallboy or Grand Slam could conceivably have been built with thicker casings (and lower charges) designed to penetrate steel rather than concrete - basically air-dropped shells (recall IJN used BB shells in Pearl Harbor for this reason).

Under that approach, a US super-heavy 16in shell escalated to 22,000lbs would be ~32.2in. Applying the above-referenced formulas and assuming higher terminal velocity (340 m/s instead of 320) - and then adjusting for 16in's angle of fall* - I get 25.5in of homogenous armor penetration.

* 1 / sin(53.25) = 1.244

...which is too close for comfort. While a high-altitude hit is unlikely, we can't risk the ship (and anything within a mile) being destroyed by a magazine explosion. So megaship's deck armor has to be ~36in instead of 30in. That protects against ~35k lbs air-dropped shells. It adds ~76k tons, ~2% of displacement.

See now we're having fun... I (IMO correctly) point out a flaw in Terry's reasoning, Richard points out that my counter-reasoning is based on flawed data and appears to provide evidence supporting my broader point, but then examining Richard's evidence makes me realize I was wrong at a deeper level about feasible threats to the megaship.
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 19 Feb 2021 06:11

TheMarcksPlan wrote:(340 m/s instead of 320)
Okay I neglected that the speed of sound at sea level is 344 m/s and that it's lower in colder, higher air (metric still befuddles this Yank).

As a body approaches the speed of sound, strong drag-creating shockwaves form - these dissipate beyond the sound barrier:

Image

...so it's probably not the case that a slightly denser shell/bomb can reach .99 mach versus .93 mach for a slightly less-dense shell/bomb (as my last post assumed). Does anyone have a good reference for the aerodynamic qualities of transsonic shells? (there's a lot online about transonic bullets but the mass/drag ratios are orders of magnitude different, as would be the aerodynamics)

The super-heavy 16in shell, by contrast, strikes at 1.5 mach - well past the transonic drag regime.

If we stick with 320 m/s striking velocity for the air-dropped shell, required thickness is 6.5% lower...
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by Richard Anderson » 19 Feb 2021 06:42

TheMarcksPlan wrote:
19 Feb 2021 05:18
Thanks for the cite. I was being generous/lazy in assuming the proffered Tallboy figure as true and working from the formulas to escalate its size.

To be fair to the anti-mega case, however, I should note that the either Tallboy or Grand Slam could conceivably have been built with thicker casings (and lower charges) designed to penetrate steel rather than concrete - basically air-dropped shells (recall IJN used BB shells in Pearl Harbor for this reason).
While I shan't comment on the mega case, a couple of notes.

Yes, The IJN Type 99 No 80 Mk 5 bombs as used at Pearl Harbor were modified 40 cm/45 3rd Year Type AP projectiles.
Under that approach, a US super-heavy 16in shell escalated to 22,000lbs would be ~32.2in.
Grand Slam was actually 46" in diameter. The US 1,600-lb AN Mk-1 AP bomb was 14" in diameter and had a 209 or 215 pound charge and a total weight of 1,590 or 1,596 pounds (it depended on if it had a Explosive D or TNT filling. The Japanese "bomb" was 1,757 pounds with a 49.4 pound bursting charge.

Based on that, you could calculate an American-designed Grand Slam AP bomb as roughly 40.25 in diameter, with a 2,887.5 pound bursting charge and weighing 22,000 pounds. Striking velocity though would be between 1,275 and 1,375 f/s, since it could be dropped at 25,000-30,000 feet, because the problems of case deformity and fuze failure/low-order detonation would not pertain for an AP design. So 388.62 to 419.1 m/s.
Applying the above-referenced formulas and assuming higher terminal velocity (340 m/s instead of 320) - and then adjusting for 16in's angle of fall* - I get 25.5in of homogenous armor penetration.
What do you get with a corrected 18-odd percent greater striking velocity?
...which is too close for comfort. While a high-altitude hit is unlikely, we can't risk the ship (and anything within a mile) being destroyed by a magazine explosion. So megaship's deck armor has to be ~36in instead of 30in. That protects against ~35k lbs air-dropped shells. It adds ~76k tons, ~2% of displacement.

See now we're having fun... I (IMO correctly) point out a flaw in Terry's reasoning, Richard points out that my counter-reasoning is based on flawed data and appears to provide evidence supporting my broader point, but then examining Richard's evidence makes me realize I was wrong at a deeper level about feasible threats to the megaship.
Grand Slam was accurate at up to 80 yards. In the first attack on Tirpitz 1/20 were direct hits, in the second attack, 2/30, with a large number "close". How much bigger a target?
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by TheMarcksPlan » 19 Feb 2021 07:38

Richard Anderson wrote:What do you get with a corrected 18-odd percent greater striking velocity?
Ugh. First another oversight: Grand Slams don't hit vertically unless dropped from a stationary balloon; they hit at 14 degrees per Richard's document. It's only ~3% difference though...

Applying the formula to the W/D/V(max) values you gave, I get 23.7in penetration.

Your D value is too high probably. Escalating the US Mk-1 AP bomb to 22k lbs (cube root of W delta = D delta), I get D=33.54in, which penetrates 26.67in homogenous US armor or 31.37in high-tensile steel.
Richard Anderson wrote:How much bigger a target?
~20x larger (~4.5x L & W).

Tirpitz speed during those raids was zero, however.

Dropping from 30k ft gives ~43 seconds to evade. At 40kn, that's ~970 yards traveled.
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Re: American militarism pre-WW2 and the Ultimate Battleship

Post by Richard Anderson » 19 Feb 2021 16:49

TheMarcksPlan wrote:
19 Feb 2021 07:38
At 40kn, that's ~970 yards traveled.
Oh, that's right I forgot USS Behemoth is also capable of 40 knots and is inertialess. Never mind.
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