WWII began with the ability of aircraft to sink capital ships still an open question. It turned out that while it wasn't impossible, it was very difficult, and the British1 looked at options beyond the typical bombs and torpedoes to make the job easier.
The longest-running was the buoyant bomb, or B-bomb, intended to take advantage of the vulnerability of ships to underbottom explosions. The basic idea was a bomb that would be dropped in front of a moving ship, and sink with the momentum of its fall, then rise back to the surface as the ship passed over it, detonating underneath its target. Work began in the early 20s, although the initial plan may have looked more like an air-dropped drifting mine than what the B-bomb became. The idea was to drop the 250 lb bomb, carrying 113 lb of Torpex, directly in front of an enemy ship. The bomb would plunge to 50', then slowly ascend back to the surface. If it was in the right place, it would hit somewhere in the aft half of the ship and go off, doing significant damage.2 If it missed, then after about 10 minutes, enough water would leak into the buoyancy chamber built into the body to send it to the bottom. In practical terms, this wouldn't have been easy, but it might well have worked better than conventional level bombing, particularly for aircraft which couldn't carry torpedoes. Although the B-bomb was ready when war broke out, the RAF showed no particular interest in using it, and despite development work continuing into 1943, it never saw service.
The B-bomb was unique in being a long-running pre-war program that failed to bear any sort of fruit. All of the other British programs were crash efforts during the war, primarily intended to deal with one particular capital ship: Tirpitz. The German battleship lurked in the Norwegian fjords, menacing the convoy routes to North Russia, and a combination of the fjords, torpedo nets, heavy AA defenses and smoke meant that numerous attacks with conventional bombs failed. Eventually, Tirpitz would be sunk by massive Tallboy bombs, but the two and a half years she lurked in Norwegian waters saw a number of unique weapons proposed to deal with her.
The first, developed in the course of only a month, was the 1,000 lb Spherical Mine. It was an air-laid spherical moored mine, with the innards scooped out and replaced by a large explosive charge and a hydrostatic pistol set to make it go off about 15' down. The idea was to attack at low level, where normal AP bombs would be ineffective, landing the mines in the water alongside Tirpitz. Much as Billy Mitchell had done to Ostfriesland, they would do great damage to her sides and bottom. Sadly, it was not to be. Two attacks were made in late April 1942, and in neither case did the bombs land close enough to damage the German vessel.
Tirpitz under air attack
Nor was the Spherical Mine the only attempt to make low-level attacks practical. The British also worked on the so-called Capital Ship or CS bomb, which was an attempt to apply the principles of shaped charges to an anti-ship bomb. Three different variants were tested before a final version was developed. First, the classic shaped charge, with a hollow cavity in the explosive to focus the blast, possibly lined with metal to produce a jet that would penetrate deep into the target. Second, the "plastic nose", essentially a flexible charge in the nose of the bomb that would flatten out on the ship's armor and then detonate, usually knocking a big chunk off the back of said armor to go bouncing around doing damage inside the target. Lastly, the disc or ring charge, which recognized the fact that the bomb might not land on the armor itself, and attempted to produce a more effective projectile using the Misznay-Schardin Effect, where a disc, probably strengthened around the edge, was blasted by an explosive charge. The conventional shaped charge was soon discarded, and work began on the other two types.
It was soon discovered that the resulting weapons would have to be very large, with the plastic nose bomb needing to be 36" in diameter and about 3,000 lb, while the disc ring bomb would have to have a diameter of 45" and weigh 5,000 lb. These both were quite large for the day, and the disc ring in particular could only be carried by the Lancaster. A smaller version, 38" in diameter, was also developed when it was decided to pursue the disc ring setup for the CS bomb, but it was still clearly a weapon for heavy bombers. Further tests showed that the bomb would need to hit the target nearly nose-on, as anything more than 30° from vertical would kill penetration, and 15° was preferable. This was a serious problem, as the easiest way to have the bomb fall near-vertically was to drop it from high altitude, which rather undermined the point of using explosives as a substitute for velocity so it could be dropped from an altitude where it might actually hit. The other option was to use a parachute, but British parachute technology wasn't up to the task of stabilizing anything over 30", so a third version of that diameter was developed.
Graf Zeppelin at Gdynia
Like the Spherical Mine, the CS bomb saw very limited service. A few 38" prototypes were dropped on Gdynia in August 1942 in an attempt to destroy the German aircraft carrier Graf Zeppelin, but all missed. Another sortie was launched against Tirpitz in early 1943, but cloud cover forced the bombers to turn back. By this point, the British were becoming disenchanted with the large-diameter bombs, as the standard 2000 lb AP bomb had equal penetration when dropped from altitude and could be carried in larger numbers. For some reason, the 30" version seems to have never been tried in combat, probably due to concerns about penetrating power. By mid-1943, the whole program was dead, and the existing bombs were scrapped.
But even as the CS bomb was going into action, another weapon, even more specifically designed to take on Tirpitz, was being developed. The Johnny Walker or JW bomb was, in essence, an oscillating mine. After being dropped in the water, it would sink, then rise back towards the surface, hopefully hitting the target ship. If it missed, it would sink back down, moving 30' laterally in the process. There were various limitations, most notably a minimum depth of 50', which restricted its use in many ports, but the fjords were Tirpitz lurked were deep enough. A parachute would make sure it was moving slow enough on impact, and the cast-iron nose cap would detach after it hit the water. A hydrogen reservoir in the nose would empty the buoyancy chamber in the tail, allowing the mine to oscillate. Between them was a 100 lb shaped charge, which would be set off if/when it hit something. The exact mechanism for moving side-to-side remains obscure, as the weapon was only used once, in a September 1944 attack on Tirptiz that saw the battleship hit by a Tallboy bomb, and the plans were subsequently destroyed.
A Highball prototype
But the most promising of the unusual anti-ship weapons was known as Highball, and it was based on the same principle as the famous "bouncing bomb". Highball was somewhat smaller than the weapon used against the dams, a 1200 lb spherical weapon carrying 600 lb of torpex. It was spun up before launch, and then skipped across the water towards the target. On impact, its spin would carry it down below the target, and a hydrostatic pistol would set it off at a depth of 30'. Release required the airplane to fly at 60' and 360 mph, faster than most torpedo deliveries, but still quite a feat in the face of defenses. Sadly, while development went well and no obvious problems surfaced by the time it was ready in mid-1943, Tirptiz was moved to northern Norway, outside the range of the Mosquitoes that carried Highball, just before it was ready to use. A year later, the program was reactivated for use against the Japanese fleet, and Mosquitoes were modified for carrier launch and landing. A squadron was dispatched to the Far East in late 1944, but it was never actually used, and in June 1945 the squadron was again disbanded.
Ultimately, none of these weapons ever had a major impact, and all proved to be dead ends. But the ingenuity displayed in answering the question of how to attack capital ships is fascinating, and worth a bit of study, as some of the weapons, most notably Highball, had real potential.3
1 Possibly others as well, but I only have sources on the British. ⇑
2 Amusingly, the only case I am aware of where this mechanism actually sunk a ship was the USS William D Porter, which shot down a kamikaze, then ran over the wreck, which floated up and broke her back. ⇑
3 I wonder if the existence of these weapons explains the lack of British guided weapon programs during WWII. They seem to fill largely the same niche, although the stress on the British electronics establishment probably had a lot to do with it too. ⇑
Comments
Bringing this to contemporary relevance, what sort of warheads do we see if someone has the crazy idea that their antiship missiles ought to be able to actually sink enemy warships, and isn't willing to bet on the enemy sending out firetrap ships with inadequate damage control?
"Weird British Anti-Ship Weapons of WW2, Part 1 of many"
@John Schilling: the Soviets came up with some pretty effective (if crude) way of solving this problem.
@John
Ships only sink when you let water in, so you need to get the warhead to the right place to do that. I can think of two major options. One is to have the missile detach the warhead and have it dive under the target. The other is to make use of one of those fancy multi-EFP warheads and try to get it deep enough that it will riddle the bulkheads. Both are at least somewhat sketchy, and a mission kill is as good as an actual kill.
@Blackshoe
This is all that was in the book I have on the subject, sadly.
@bean
Are modern torpedoes expected to actually sink a mid-size ship (say a DDG, but not a CVN), or are they also most likely to result in a mission kill because damage control and ship design are so much better than they used to be?
Modern destroyers aren't that much bigger and tougher than those of 50 years ago, and as the video at the top demonstrates, those were very vulnerable to heavyweight torpedoes. If the first hit isn't enough, the second almost certainly would be.
I've never understood the tirpitz obsession. Why not just mine the shit out of the fjord it was hiding in? or sink some hulks. Sure, the germans would eventually clear it out, but you'll buy yourself a lot of time each time you do it, and that had to be cheaper than the shenanigan they got up to.
@redRover: heavyweight torpedos are absolutely assumed to be ship-killers to modern surface combatants.
@bean: seems like someone will think about using a high-diver (like, say, a MARV, or maybe a hypersonic glide vehicle) and attaching some kind of penetrator to that would make it punch through the decks with a warhead that would explode deep in the hull/underwater.
IIRC, the USN used runway penetrator LGBs on the Iranian ship Sabalan during OPERATION PRAYING MANTIS, resulting in cracking her keel (credit to the NEDAJA, they got her back to port and repaired her).
@Blackshoe The runway penetrator that would have been mostly useless against the runways of many Warsaw Pact airports, given that many of those were... tiled...
@Blackshoe
I thought they were just using standard LDGP bombs, which should have plenty of penetration against a typical frigate or smaller. Not sure what a runway penetrator would add.
@Emilio
Huh? Changing from concrete to tile isn't going to keep a thousand-pound bomb out. If you build the runway out of steel, maybe, but that gets expensive and you need a lot of it.
@cassander
Probably because they had to be 100% sure she was out of action before they could meaningfully reduce the forces committed to containing her. Mines are great for keeping a ship bottled up for a few days or weeks, and hulks might extend that to a month or two, but those are the timescales it takes to move ships somewhere more useful.
A missile equivalent of the Japanese "diving shells" is sort of the obvious solution, except that those didn't work terribly well in practice. Might still be worth trying them again with active terminal guidance, though. Multi-EFP warheads are potentially useful even if you're just going for a mission kill.
And mission kills are only as good as hard kills in the context of a single mission. In a campaign or a war, it's not so clear. An alternate Midway where the Kido Butai sails home with holes in all the flight decks but the Yorktown is still sunk, leads to a different Solomons campaign. And what does the Falklands look like when Glasgow, Glamorgan, Antrim, Argonaut, Plymouth, Galahad, and Tristam are all sunk outright?
There are also sea denial strategies based on inflicting unacceptable costs in a limited war, where sinking an enemy ship has a much larger effect than sending it home under its own power.
Are Exocets considered capable or killing a modern destroyer? Or are they getting a bit old?
I wasn't so much thinking of the diving shells as the plunge bomb used on the AUM-N-6 Puffin.
With modern warships, a mission kill has a pretty good chance of being a constructive total loss. Or at least of taking way longer than the conflict lasts to fix up. Note that most of the ships you mention were at the very least out of action for the rest of the Falklands campaign.
Exocet has been pretty marginal against destroyers for decades. Stark survived a hit from one, as did Glamorgan.
@John Schilling On sinking ships, bring back the torpedo bomber with Mark 48 or Spearfish?
Don't think they'd fit in the bays of an F-35 but an F-18E or coastal command F-15E should be able to carry a couple. Wire guidance obviously won't work, but drop them 40km away, programmed to run towards the target for 15 minutes and then go active?
No. Aerial torpedoes are not the same as submarine torpedoes, and there would be a tremendous amount of reengineering to do to make those capable of airdrop. Also, guidance would be a pain, because the target can move almost as fast as the torpedo, so just telling it to run in a straight line doesn't work.
I'd speculate that most non-total wars are won or lost in the newspaper headlines and press conferences of the participants.
A ship that is actually sunk looks far, far worse to the general public than "we were able to fight off the attackers and returned home triumphant for some repairs."
The fact that the repairs might take 3 years and/or end with the ship being written off entirely won't make it to the headlines in time to affect public opinion.
Love the topic!
Bean wrote "Modern destroyers aren’t that much bigger and tougher than those of 50 years ago, and as the video at the top demonstrates, those were very vulnerable to heavyweight torpedoes. If the first hit isn’t enough, the second almost certainly would be.".
I'm not sure I understand this. Comparing any WWII destroyer (maybe 2000-3500 tons) to something like a Type 45 (>7000 tons) ... a destroyer today is like an unarmored cruiser back then.
@Bean, a tiled runway does not keep the bomb bout, but it should make repairing it so much faster than repairing a large slab of concrete or tarmac.
https://en.wikipedia.org/wiki/BezmerAirBase#/media/File:BulgarianSu-25KFrogfoot.jpg
https://en.wikipedia.org/wiki/BezmerAirBase#/media/File:BAFSu-25andUSC-130.jpg
@Kit
It appears I misremembered the displacement of the Type 12, and that it's actually around 3,000 tons, significantly lower than I thought. That said, I know the range for a WWII destroyer, and by the 1970s (which was actually 50 years ago) ships had grown a fair bit. The USN was starting to build the Spru-cans, which are essentially the same size as the Burkes.
@Emilio
Ah. I suspect the tiles wouldn't actually render them ineffective, although it would make repairs somewhat faster. Maybe 50%?
Doesn't going to tiles for your runway surface negatively impact the weight of aircraft that can use it? Because the weight isn't spread across the under-surface structure as well. Anti-runway munitions, AIUI, work by a camouflet mechanism, blowing a hole underneath the runway and collapsing the surface into it. Tiles mean you only lose the surface above the resulting crater, but it also means the runway has a lower load capacity because of the lack of spreading load.
Mission-kill the target well enough that it doesn't have any way to defend itself and then hit it with something big and unwieldy?
Or something with a small enough CEP that you can hit the same spot a bunch of times and drill a hole into an important bit.
Trouble with the mission-kill-then-cato-kill angle is escorts. If you're trying to grease a lone FFG, sure, chewing its radars to rat chow with ARMs then planting a dozen 1000kg LGBs in the engine room might work. Try that with a CVBG, though, and you might chew up the outermost Burke only for the next wave to catch a dozen SM6 fired by the Tico they never even got close enough to shoot at.
@bean Sure, a Mk48/Spearfish would need a new casing at minimum for air drop. But a "tremendous amount" of reengineering? The current day Mk 46 ASW torpedo seems to be available in surface launch and air launch versions without much change.
Wikipedia gives the Mk48 top speed as 55 kn and the Spearfish as 80 kn, which not many warships can outrun. (Happy to be corrected by more accurate sources.) My back of the envelope calc for the "no escape" range for a Mk48 against a 30 kn warship in a tail chase is just under 10 nm, a Spearfish 18 nm
That's the worst case, attacks from ahead do much better. Aircraft aren't as stealthy as subs, but they can get into position much faster.
Not saying that this is a super weapon, just interested in the pros and cons.
@Hugh
Mk 46 Weight: 500 lbs Length: 8.5 ft
Mk 48 Weight: 3700 lbs Length: 19 ft
These are very different propositions from an aircraft ordnance perspective.
As noted by the esteemed Directrix above, torpedos carried by aircraft (and surface ships!) are generally considered "lightweight torpedos"; torpedos carried by submarines are considered heavyweight torpedos.
The Soviets (again, those crazy bastards) actually had missiles that threw HWT (notably the Metel Complex/SS-N-14). Go find some pictures of them; they are truly gigantic things.
Could you strap a HWT to an airplane? I mean, sure I guess, if you tried hard enough. But it's going to have to be a very large aircraft, which probably means it's not going to be a very fast aircraft, and it's also probably not going to be a very stealthy aircraft, which means in the end it's not going to be a very survivable aircraft.
Blackshoe:
So you can't attach it to a B1?
Blackshoe:
Blackshoe:
I think the real problem is that it won't be a cheap aircraft.
The Mk 46 was designed from the start for air launch. The Mk 48 was not. You could design a heavyweight torpedo for air launch, but it would be a major redesign to deal with things like the loads of water entry. As for range, it's primarily a guidance issue. Torpedoes generally can't detect a target from that far away. A straight-running torpedo is unlikely to get close enough to a target to do any good. Also worth pointing out that most torpedoes show a tradeoff between speed and range, which is usually reported very poorly. I think I talk about this a bit in Carrier Doom 4. So the no-escape range for a Spearfish is likely to be quite a bit lower. Also should be noted that ships can turn and run away, which they will do if they see you dropping torpedoes.
No, he's right about survivability being the problem. Nobody wants to have to bring their fancy plane within 20 miles of the target, particularly if that fancy plane is a B-1, because it's a very good way to lose said plane in the face of modern defenses. If the B-1 needs to kill a ship, it's going to do it with LRASM, which has an order of magnitude more range.
@Directrix Gazer and @Blackshoe The GBU-28 bunker buster bomb is 5000 lbs and 19 ft, same length but heavier than the Mk 48, and the F-15E has dropped those. The British Spearfish is longer but still lighter than the GBU-28. So a bigger plane isn't necessary. (Although I imagine something that size isn't for aerodynamics.)
@bean Thanks, that makes sense. Hadn't thought about the limited range of active homing. And will read Carrier Doom 4 when I get the chance.
Regarding the CS bomb, Guy Gibson had a few things to say about it in Enemy Coast Ahead, as his squadron (106) had trained to use it: