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They will need to streamline their pilot training to increase throughput.
Japamese empire & it's Navy had no means to have it all - BBs, CVs, CAs, CLs, DDs, submarines, air service, escort/anti-submarine force - in good numbers and in good 'quality'. In order to have something of any of that more and/or better, something else will need to take a cut. Especially concerning that Japan had every intention to battle it against the established powers, and over what is basically half of Earth's surface.
Taking the immense distances involved into account, the air service needs to be prioritized, meaning that aircraft carriers, embarked air groups and land-based aircraft are now 'capital' stuff. In return, that means that other 1st line assets should've been tailored to protect the aircraft carriers, and to act as support for the expected far-flung air bases and naval stations.
So I'd go even lower wrt. the battleships, making them to be similar to the Dunkuerque and Richelieu, ie. 2 x 3 x 16in guns, all-forward, with a lot of place devoted to the 100-127mm multi-purpose guns and the 40mm AA guns, and ~30 kt speed.
Make a series of light cruisers to be the 'bodyguard ships' for the CVs, task being to deal with air and submarine attacks.
Modify the Ise and Hyuga into the full-blown aircraft carriers before 1942?
Most people today have an unrealistic idea of typical WW2 carrier task force operating speeds.
Generally they were in the region of 15-25 knots, lower if attached to a convoy. USN practice for island strikes in the 1942-44 period was for an overnight run in to the launch area at 25 knots. In 1944-45 when Task Groups lingered in support of landings the whole group would run at c15 knots and increase by a few knots for TG launches. If a carrier needed to operate her aircraft out of sequence with the TG she would adopt a speed to allow launch / recovery as quickly as possible while remaining within the rings of escorts. The BPF while operating off the Sakishima Gunto in April / May 1945 was generally operating at 17-21 knots (in the first two weeks of April TF57 speed couldn't exceed 24 knots due to Illustrious operating with only 2 props).
TG speed was also affected by the ships operating with the carriers and the need to keep the whole group together, or at least relatively close to each other, for defence. So operating with most battleships would slow things down. The operating area also played a part. The South Pacific seems to have enjoyed calmer winds that most other areas.
At Philippine Sea Taiho & Shokaku were operating at 25-26 knots when torpedoed. (Taiho was hit just a few minutes after the launch of her strike, and was not slowed by the hit).
The Junyos were perfectly capable of operating the B5N & B6N torpedo bombers as well as both the D3A and D4Y dive bombers. The light carriers however generally did not operate dive bombers, due to their relatively small air groups with the emphasis on fighters. The next generation B7A dive/torpedo bomber was designed to operate from the Taiho & later carrier designs and would probably have been beyond the capablities of the earlier carriers unless the IJN had succeeded in getting a working catapult to sea on its carriers. Otherwise they would have had to have relied on RATOG.
The IJN CVE spent most of their time as aircraft transports.
When designing the Colossus / Majestic classes the RN concluded that 25 knots was adequate for the role they envisaged for them in 1942 but raised it to only 28 knots in the 1943 Centaur class. Nothing like the 30-32 knots of the various armoured carrier classes or the 33 knots preferred by the USN, or even faster speeds favoured on the whole by the Japanese for their fleet carriers.
Even if we ignore the treaties, to which Japan was still a signatory when these decisions would have to be made(?), as mentioned before ~1942 nobody was really sure that carriers were the new kingmakers of naval warfare. If you were in charge of naval strategy and procurement before that and you suggested to stop investing in battleships and go all-in on carriers, you'd be sacked for recklessly endangering your nations naval power!
I'm not sure such a halfway position is that useful. You either have a battlefleet that has some chance of beating the enemy battlefleet, or you don't. If you don't, use your money for something else than building a fleet that will certainly be roflstomped by the enemy fleet.As it can be read in the post quoted, I've not suggested that investment in the BBs is stopped, but just that the investment is smaller.
I'm not sure such a halfway position is that useful. You either have a battlefleet that has some chance of beating the enemy battlefleet, or you don't. If you don't, use your money for something else than building a fleet that will certainly be roflstomped by the enemy fleet.
This is where you run into the problems of which period and which navy you are discussing.Where carrier speeds mattered is turning into the wind and/or returning to the task force. Also, Judys used RATO on smaller carriers to help with taking off. I think the Jill did, too.
Diesels were a rapidly advancing technology in the 1920s-30s-40s. Even a few years made difference.Keeping on the topic of Japanese engines, what about diesel engines for ships? In particular, low speed two stroke ones, having several advantages (which is why they have dominated oceanic shipping post war) :
There are of course also a number of significant disadvantages for this kind of engine, particularly for warships:
- Ability to use the same cheap bunker fuel that steamships use.
- No need for an expensive and heavy reduction gearing nor reversing gearbox as the engine itself is reversible. Thus the engine is directly connected to the prop shaft.
- Very high thermal efficiency, about 40% can be expected in the WWII time frame. Including at part load. This could be a significant advantage, as a large fraction of the Japanese oil supply was used as fuel oil for the IJN.
- With a piston ported design, as was common for two stroke diesels of the time, no valves and valve gear needed.
- If using crankcase scavenging, no need for a blower either.
- No risk for a steam explosion if the ship is hit.
- Poor power density. Contemporary low speed diesels have about half the power density of medium speed diesels. In the WWII time frame medium speed diesels were somewhat worse than steam plants (the Deutschland class, for instance), but newer diesels at the time being somewhat better. OTOH without reduction gearing, separate cruising and reversing turbines etc, the low speed diesel can claw back some of that disadvantage. Further the much better fuel efficiency allows carrying much less fuel than a comparable steamship.
- Height of the engine. And not only the engine itself, there needs to be space above the engine for piston and conrod replacement. For a gunship, this probably means a bump in the citadel roof above the machine room spaces. OTOH the machinery spaces are probably shorter than for an equivalent steam plant, enabling a shorter citadel.
- Availability of large enough engines. The largest pre war diesel I'm aware of is the 22500 hp B&W 2000. With a four shaft ship, that might be enough for roughly a cruiser sized ship. OTOH with a concerted effort bigger ones might be designed.
Historically, the Japanese experience with diesels for high speed warships wasn't a happy one. They were seriously considering diesels for warships, e.g. several of the design studies leading up to the Yamato class were diesel powered, in part and total. But experience with a ship using the selected engine (sub tender Takei(sp?)) was very bad, and instead an all-steam design was chosen. Somewhere I read that at the time they were chasing the double acting diesel chimera, also resulting in a number of submarines that had to eventually be reengined with lower power single acting engines.
In 1928 Mitsui licensed the B&W marine diesel portfolio, in the interwar years the market leader in that segment. So it seems they could have built decent enough diesels, at least had they avoided the double acting chimera.
The Japanese could have done a lot to improve training right before Pearl Harbor and in 1942/43. But the main things that needed to changed were attitude, doctrine.Admiral Koga Mineichi was possibly the most boring admiral of the IJN. He managed to reach the top without making many enemies or achieving anything too notable. Koga was promoted to Vice-Admiral and placed in command of the Training Fleet on 1st December 1936. The Training Fleet had for some time operated the ancient armoured cruisers Yakumo Imperial Cruisers, Iwate Imperial Cruisers and despite being damaged Asama Japanese Cruisers. Koga historically used his influence to persuade the IJN to order a class of four training cruisers, the Katori Class Katori-class cruiser - Wikipedia, which were built quite slowly if very cheaply.
So let us assume that an Alien Space Bat decides to offer some minor help to the IJN when Koga takes command. It persuades (forces?) Koga to order a squadron of rather different ships and uses its powers to cause the IJN to accept the increased cost. Katori is built as a Japanese copy of a Colossus Class aircraft carrier with a slight increase in length to allow it to carry half of an Agano Class cruiser's machinery giving 50,000 shp rather than the 40,000 shp of Colossus. As well as allowing the cadets to learn about aircraft handling, part of the hangar could also become a classroom if desired.
In addition, two Matsu Class destroyers Matsu-class destroyer - Wikipedia are built to enable the cadets to learn how to use guns and torpedo tubes and two of the Shimushu class (ideally redesigned to make them easier to produce as in the later classes) Shimushu-class escort ship - Wikipedia to introduce the cadets to Diesel engines and to practice anti-submarine tactics with the Matsus. The last ship of the new Training Fleet is an early Ashizuri Ashizuri Class to allow the cadets to learn the mysteries of underway resupply of a carrier with aviation gasoline, bombs, torpedoes and other supplies.
The planned cost of a single Colossus, £1.8 million, is about the same as all four Katori Class (assuming that the last, Kashihara, had been completed). However, the Colossus Class carriers ended up costing around £2.3 million each, possibly because of wartime inflation. Thus we are spending more on the Training Fleet than the IJN planned. However, we might also be setting up some interesting production lines, especially if the carrier can be built in Japan nearly as fast as Colossus was built for the RN. The other consequence is that the staff of the Training Fleet learn useful things whilst baffling their cadets.
The problem here is license when.I'm unsure which direction to go with here; either standardize one of the two cannons for aircraft or license a different, better cannon for standardization.
Problem here is timing. The type 99 mk II is late, coming into service in late 42/early 43. It takes time ( a lot of it) to replace the majority of front line aircraft, 6 months to a year.The Type 99 mark 2 hit reasonably hard (Its HEF shells seemed to pack a punch) and was decently accurate but fired very slowly and could not be synchronized.
Meanwhile the Ho-5 had a blistering fire rate, could be synchronized relatively easily and was highly reliable but was one of the weakest 20 mm cannons in the world and had very poor muzzle velocity. The weaknesses of one were the strengths of the other, and vice-versa.
According to one source the type 99 model 5 production was 10 prototype and 50 pre-production by July 1945. It is basically a non-starter. An extra 200 guns in July of 1945 doesn't change anything.The IJN attempted to fix the low fire rate of the Type 99 with the Model 5 (sources are scarce, Wiki says between 670~750 rpm)
Very true, Japanese army was slow even to get 12.7mm guns into aircraft. And two 7.7mm and two 12.7mm guns was not state of the art in late 1942 or 1943. Especially the Japanese 7.7mm gun and the Japanese 12.7mm guns.Japanese have had even worse problems with their fighters' firepower before these two guns are introduced. The Army 1-engined fighters were without any 20mm cannons for the 1st half of the Japanese-Anglo-American war, while the Zero was with the cannon that had the low ammo count per cannon, and the 1st Type 99 was with just 600 m/s.
The Ho-3 was obsolete, it was more a contemporary of the French HS-7 & 9 guns. Very similar ballistic performance, weight and rate of fire (also drum feed). Basic problem for further development is the 400rpm rate of fire (peak?). A Spitfire VB of mid 1941 could deliver the same weight of fire as three Ho-3s and with 120 rounds in the drums compared to the 150 in the three Ho-3s the total number of shells was 80%. Japanese needed to both speed up the rate of fire significantly and change the feed system. Or get the smaller, lighter, Ho-5 into production a lot earlier.The adopted anti-tank cannons were never installed in the Army 1-engined fighters - while not great, installing a pair of these on a 1-engined fighter would've still brought a good firepower against the sturdy Western aircraft, especially the 4-engined types.
-German mine shell is only of benefit if the country in question can actually manufacture them in quantity at an acceptable scrap rate. Japanese might have gone for a lighter conventional shell if higher MV was really desired.Several things the Japanese can do before they bomb Pearl Harbor:
- to adopt the Mine shell for their cannons ASAP (would've give the Type 99 Mk1 the 700 m/s MV; I consider 700 m/s as a reasonably good MV)
- early adoption of belt feed for the Mk1
- big drum ASAP for the Mk1
- both Navy and Army adopt the Mk2 (Oerlikon FFL) ASAP
- speed up the Oerlikons
Very true, But how light are we talking? and how much ammo?Once engine power is up (1500 HP and more), 4 light cannons are not too heavy to lug around for a fighter.
I'd argue that the IJA single-engined fighters would've been fine had they added another pair of 12.7 mm guns earlier, the Ho-103 was a reasonably capable HMG with good fire rate, decent muzzle velocity and reasonable one-second-burst-mass when they introduced the Ma 102 shell. Most of the aircraft the IJA were facing at that point in the war didn't seem to warrant the installation of cannons much earlier.Japanese have had even worse problems with their fighters' firepower before these two guns are introduced. The Army 1-engined fighters were without any 20mm cannons for the 1st half of the Japanese-Anglo-American war, while the Zero was with the cannon that had the low ammo count per cannon, and the 1st Type 99 was with just 600 m/s.
The adopted anti-tank cannons were never installed in the Army 1-engined fighters - while not great, installing a pair of these on a 1-engined fighter would've still brought a good firepower against the sturdy Western aircraft, especially the 4-engined types.
Those seem to be the most future-proof options.Several things the Japanese can do before they bomb Pearl Harbor:
- to adopt the Mine shell for their cannons ASAP (would've give the Type 99 Mk1 the 700 m/s MV; I consider 700 m/s as a reasonably good MV)
- early adoption of belt feed for the Mk1
- big drum ASAP for the Mk1
- both Navy and Army adopt the Mk2 (Oerlikon FFL) ASAP
- speed up the Oerlikons
Let's say that 3 of these suggestions are actually accepted and proceeded with. For the Navy, that would've gave them less need for the Zeros to land and rearm, with major consequences during the battles of 1942, especially at Midway. For the Army, that means they actually have cannon-armed fighters between 1941 and 43, again meaning that hits are transformed into kills much more reliably.
Once engine power is up (1500 HP and more), 4 light cannons are not too heavy to lug around for a fighter.
For what it's worth, the army did scale up the Ho-3/5 system to create the 37 mm Ho-203 and Ho-204 respectively, the latter of which was arguably the best 37 mm guns of their class (BK 3.7, 37 mm M4, NS-37, Vickers S). There's also the Ho-155 which was a Ho-5 scaled up to 30 mm, which was also a very capable and surprisingly lightweight cannon for its class.More adventurous suggestions:
- neck-out the Army 20mm gun to 23mm
- a 25mm gun, with lower MV than the 25mm AA gun but with greater RoF, lighter and more compact
- adopt the MK 108 but with lighter & shorter shell for the greater MV
As mentioned earlier, the two guns were created around the same time, the Mark 2 was only introduced that late due to IJN preference and political corruption. Stamping that out makes the Mark 2 appear much earlier than it did historically.Problem here is timing. The type 99 mk II is late, coming into service in late 42/early 43. It takes time ( a lot of it) to replace the majority of front line aircraft, 6 months to a year.
The Ho-5 being the weakest 20mm requires a 2nd look. Since it was also a rather light cannon and it's ammo was light it's power to weight ratio was good.
The blistering rate of fire soon vanished. Lack of chrome and nickel for high quality steel alloy parts soon required a drop in rate of fire to 700-750rpm. Which is still pretty good.
The rate of fire does mean that the weight of shell/s delivered is still pretty good. Even it's 'normal' HE shell (79 grams) held 4g Cyclonite + 3.7g of incendiary which put's payload higher than than the Soviet 20mm gun/s. (6.1g?)
Compared to the 10g HE in the type 99 shells it is a around 75% but the HEI shell in the type 99s held 5g TNT + 3g incendiary so the explosive/incendiary effect was closer.
If Wiki is right and the main change of the Mod 5 is the stronger buffer springs, I'd imagine it would be relatively easy to introduce that earlier in the timeline, no? The fire rate doesn't need to be stratospheric, but 480~500 rpm is unnaceptable for a 20 mm.According to one source the type 99 model 5 production was 10 prototype and 50 pre-production by July 1945. It is basically a non-starter. An extra 200 guns in July of 1945 doesn't change anything.
The Ho-3 was obsolete, it was more a contemporary of the French HS-7 & 9 guns. Very similar ballistic performance, weight and rate of fire (also drum feed). Basic problem for further development is the 400rpm rate of fire (peak?). A Spitfire VB of mid 1941 could deliver the same weight of fire as three Ho-3s and with 120 rounds in the drums compared to the 150 in the three Ho-3s the total number of shells was 80%. Japanese needed to both speed up the rate of fire significantly and change the feed system. Or get the smaller, lighter, Ho-5 into production a lot earlier.
Good call on the 'classic' lighter shell for better MV.-German mine shell is only of benefit if the country in question can actually manufacture them in quantity at an acceptable scrap rate. Japanese might have gone for a lighter conventional shell if higher MV was really desired.
What does it take? Inspiration supported by money and resources.Very true, But how light are we talking? and how much ammo?
and depending on the gun, what does it take to go from drum to belt? Hispano gun specs often do not include the belt feed device 8-10.5kg? but then a 60 round drum was around 10-14kg(?)