High altitude air defense of Japan

high altitude air defense of Japan
Leo et al.

I'm waiting for the " but the CW R-3350 became the postwar standard engine for air transport, worldwide". To which I'll reply: " the only components common to the wartime and postwar engines were nuts, bolts, piston rings and, for a while, connecting rod bearings".

"The Torque Meter" the journal of the Aircraft Engine Historical Society has gone into the origins, development problems, CW non-solution to problems, aircraft losses and corporate intrigue in detail, naming names, etc. Much of Wright's second team were assigned to the wartime '3350 while the top guns were assigned to the stillborn R-2160 Tornado program.

Dynasoar
 
Leo et al.I'm waiting

NASM-A19771008000-NASM2014-04876.jpg


Okay. The R-3350 isn't the topic. The Shoda-Hikoki Shoda-Ken #1 12 cyl. inverted V-12 air-cooled engine of 24 Litres/1464 cid, 1433 lb, 1,200 hp, was described as a two-stage/dual supercharged engine, with viscous variable speed drive. The hot-fused cylinder head fins are a distinctive feature also utilized on the Nakajima Homare through subcontract with Shoda. I don't know if the supercharger is dual or two-stage. Just the question for an aero-engine expert.
 
Leo, The wait was worthwhile. Where did you locate data on this, to me, totally unknown engine. Just last Tuesday I was leaning on a Ranger IV-770 at Santa Paula, California airport. A 12 cylinder air cooled engine about half the size and HP of your Shoda-Ken. Reminds me of prewar Renault inverted V-16s.

Dynasoar
 
Leo, The wait was worthwhile. Where did you locate data on this, to me, totally unknown engine. Just last Tuesday I was leaning on a Ranger IV-770 at Santa Paula, California airport. A 12 cylinder air cooled engine about half the size and HP of your Shoda-Ken. Reminds me of prewar Renault inverted V-16s.

Dynasoar

Small world. Not too long ago while disputing the various aspects of motor-cannon, I googled a picture of the Ranger 770 just for giggles, and through the mysteries of google, came across the picture through the courtesy of the NASM, which has the engine down in the vault next to the Ark of the Covenant. The Shoda-Ken is smaller but based on DB-601, and also features FI.
 

CalBear

Moderator
Donor
Monthly Donor
Let's assume that it is mid 1943 and Japanese air defense planners believe that American Boeing B-29 and B-32 strategic bombers will live up to the performance specifications they were designed to meet. (IOTL these aircraft were only marginally successful due to engine performance and durability shortcomings and for this reason, high altitude day bombing was largely abandoned.)

Anticipating mass strategic raids at 30,000 feet and above, what technical approaches could be employed to combat the bombers? Hitachi turbosuperchargers were seldom made to work long enough to complete a high altitude interception- other means? Raids on US bases in China and later the Pacific island bases. German rocket interceptors or Kamikazi missiles?

What would you do?

Dynasoar
Actually the reason the High Altitude bombing was such a failure had little to do with the shortcoming of either the B-29 or B-32. Firstly it was tried before sufficient combat mass had been reached to allow for a real Bomber offensive (can't show up every week to 10 days and expect much in the way of results). Secondly weather conditions at high altitude over Japan, particularly the jet stream, played havoc with bombing formations and bomb patterns. Most importantly, however, was that the entire theory of strategic bombing was flawed, despite the devastation wrought across Europe, the idea itself was incorrect (actually both versions were incorrect; the American precision daylight was not achievable with weapon systems in the 1940s while Bomber Command's dehousing program lacked sufficient mass to achieve its overall goal of destroying the enemy will to fight AND their ability to continue to produce armaments).

However, what the Japanese could have done to deal with the expected high altitude raids was actually build up its defenses, especially AAA. The Japanese produced around 1,000 Type 99 88mm guns (a copy of the German SC/30 naval gun not the Flak 18/36) and only a couple thousand of the Type 88 75mm AAA gun (which was a marginal choice for use against aircraft at 28-30k). By comparison the Reich constructed over 21,000 8.8cm 18/36/37/41 AAA along with over 4,000 of the FlaK 38 10.5cm and a few dozen of the spectacular 12.8cm FlaK 40.

Luftwaffe studies found that it took around 3,000 8.8cm rounds fired to account for a single B-17/B-24. AAA is a pure numbers game, throw enough metal into the sky and some poor soul will fly into a bit of it. The Luftwaffe defended the Reich with over 25,000 heavy AAA guns. The Japanese tried to defend all of the the Home Islands, along with Formosa, with 1,000 good heavy guns and around 2,000 barely adequate 75mm. Considering the immense difficulty the Japanese had to deal with simply to engage High Altitude bombers (most Japanese cities are along the coast, this reduces the amount of time the bomber stream can be engaged*) the Japanese needed several time more AAA guns to be equally effective as the Luftwaffe, instead the Japanese had 87% fewer guns available.

* As an example: Any bomber attempting to strike Berlin had a minimum 140 mile flight from the coast to Berlin (this involved cutting across the neck of the Danish Peninsula and approaching Berlin from the Baltic) with a direct route bing over German occupied territory for almost 450 mile each way. This scenario gave defenders at least a full hour to engage the aircraft as they crossed multiple defensive belts, with the direct route being over Reich controlled territory for over four hours. Bombers attacking Tokyo/Yokohama were only over Japanese territory for a total of 90 miles combine in and out of the target. Maximum exposure to AAA was around 20 minutes. There isn't a single place in the Home Islands that is 100 miles inland, with almost all the main targets right on the coast (and it is the South/Southwest coast the side that faces the direct route from the Marianas meaning U.S. strikes came straight in from the water)
 
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However, what the Japanese could have done to deal with the expected high altitude raids was actually build up its defenses, especially AAA. The Japanese produced around 1,000 Type 99 88mm guns (a copy of the German SC/30 naval gun not the Flak 18/36) and only a couple thousand of the Type 88 75mm AAA gun (which was a marginal choice for use against aircraft at 28-30k). By comparison the Reich constructed over 21,000 8.8cm 18/36/37/41 AAA along with over 4,000 of the FlaK 38 10.5cm and a few dozen of the spectacular 12.8cm FlaK 40.

Luftwaffe studies found that it took around 3,000 8.8cm rounds fired to account for a single B-17/B-24. AAA is a pure numbers game, throw enough metal into the sky and some poor soul will fly into a bit of it. The Luftwaffe defended the Reich with over 25,000 heavy AAA guns. The Japanese tried to defend all of the the Home Islands, along with Formosa, with 1,000 good heavy guns and around 2,000 barely adequate 75mm. Considering the immense difficulty the Japanese had to deal with simply to engage High Altitude bombers (most Japanese cities are along the coast, this reduces the amount of time the bomber stream can be engaged*) the Japanese needed several time more AAA guns to be equally effective as the Luftwaffe, instead the Japanese had 87% fewer guns available.
...

I'm afraid that you rise good points to why the immense increase in production of AAA is not the option for Japanese.
Germans were needing 4000 heavy shells (88mm and bigger) to down an WAllied A/C in 1942. That means aircraft are flying mostly under 20000 ft, the radars are used, crews are trained and proficient, guns are relatively new.
The situation from 1944 is a catastrophe for the heavy Flak efficicency and people on the ground. Experianced crew went to the Luftwaffe ground units after the Stalingrad disaster (replacements are not up the task), guns have a varying degree of barrel wear, American bombers are present and they fly at 25000 ft routinely, elctronics, at least for night duties, can be spoofed - net result is that it now takes 16000 (16 thousand) of heavy rouds fired to kill a WAllied A/C. In 1944, Germany used between 9000 and 10000 heavy AA pieces between Atlantic and Poland, between Batic and Alps.
All data from Westerman's doctoral thesis on German Flak.
The US bomber losses, once LR escorts removed LW fighters as a threat, went down well into single digits.

Japan has the geographical disadvantage, that is an elongated country indeed. Thus any bombing raid will be contested by perhaps 10% of the AAA, while ability for the fighters to concentrate on an incoming bomb raid will be much better, provided they indeed have Dowding-san in command.
 
...
Okay. The R-3350 isn't the topic. The Shoda-Hikoki Shoda-Ken #1 12 cyl. inverted V-12 air-cooled engine of 24 Litres/1464 cid, 1433 lb, 1,200 hp, was described as a two-stage/dual supercharged engine, with viscous variable speed drive. The hot-fused cylinder head fins are a distinctive feature also utilized on the Nakajima Homare through subcontract with Shoda. I don't know if the supercharger is dual or two-stage. Just the question for an aero-engine expert.

Thank you for the information. At least until an aero-engine expert chimes in:
The engine looks like having two compressor stages, one per each side (linky). The compressor at the left side (port; 1st stage here) of engine supplying the compressed air to the compressor at the right (starboard; 2nd stage here). The second stage, as expected, was to feed the compressed air to the cylinders. Similar system was used on several DB 2-stage engines, that never went into mass production, though the German engines used the compressor at the starboard as 1st stage.
Unfortunately (fortunatey?) for the Japanese, they never attached similar compressor system to the Ha-40.

edit: not unit, but until
 
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CalBear,

I don't dispute the reasons you presented for the failure of strategic high altitude bombing of Japan, however in my view they are incomplete. The B-29 program represented an expenditure comparable with the Manhattan project (possibly in excess- totals vary). To admit that the performance goals were not achieved because of shortcomings in the engine- and this was confirmed in 1944 by the (Harry S.) Truman Committee- in a wartime setting is damning. Yet Truman accused Wright Aeronautical of sacrificing design and quality (hence performance and reliability of the end product) in the interest of quantity production.

I tried to locate references for B-29 reliability in comparison with B-17 and B-24 operations. Gross 'accident' rate of B-29 is presented as 33% higher.

From the standpoint of mission losses, ww2airmen.net presents a USAAF chart that shows the following: 20th AF, 1944 70 total, 25 in combat 45 losses noncombat (Mechanical and other 64%). In 1945 10 total, 4 in combat, 6 mechanical.
The 21st AF, 1944 25 aircraft lost total, 5 in combat, 20 other on mission. In 1945, 309 lost, 196 other mission related aircraft losses- again about 64%.

B-29 aborts to Ewo Jima after capture, 2400. Considering an early high altitude raid from Saipan to Tokyo conducted by 21st AF as reasonably representative, 103 aircraft took off, 85 bombed targets, 1 was lost to enemy aircraft and 17 aborted enroute.

Later, with the engine killing climb to the substratosphere eliminated, non-combat losses decreased substantially. Is this making a virtue of necessity?

Dynasoar
 
The change in bombing strategy, from daytime high altitude HE to lower altitude night incendiary tactics, renders the need for Japanese high altitude interceptors moot. Once the fighter strength of the Japanese was low enough, daytime raids at low altitude also happened. The major daytime high altitude usage of B-29s (and eventually B-32s) was for photo recon. Diverting limited Japanese industrial capability to try and hit these recon flights is simply not worth it. What Japan needed was a combination of decent radar that could pick up raids while well offshore, lots of flak with central direction, and radar equipped/directed night fighters. That combination would have a shot and making the cost of night low altitude incendiary raids higher, and not let Lemay send in B-29s with some guns/gunners removed for better bomb loads.

The problem is that for Japan to have such a system available in 1945 they would have needed to begin developing it and devoting resources to it much earlier. Even if they could produce adequate radar and radar equipped aircraft, which is problematic, their industrial capacity was tied up doing other things seen as more vital earlier in the war.
 

thorr97

Banned
Dynasoar,

You. Keep. Missing. The. Point.

Yes, climbing to altitude exacerbated the B-29's engine problems. But at high altitude or low, those engines remained problematic. While continued operations with B-29s using those engines meant lost aircraft and dead crews, the USAAF deemed that an acceptable price to pay for getting bombs on target in Japan.

And that's the key point - getting bombs on target.

As I and others have repeatedly pointed out, the original tactic of bombing from high altitude was failing to get those bombs on target. It wasn't failing due to engine problems or structural issues with the B-29s, it was failing due to atmospheric conditions. No one had previously attempted to conduct strategic bombing from such high altitudes and thus no one had run into the atmospheric conditions we now call the jet stream. At best, previous encounters at those altitudes with such conditions were labeled just as "winds aloft" and were deemed as temporary things. This, due to the relative rarity of aircraft even being able to routinely operate at or above 30,000 feet altitude. Over Japan, the jet streams were an almost ever present atmospheric condition and it served to greatly slow the bombers over target and also blew all over the place the bombs they dropped. Hence the unacceptably poor CEP those high altitude raids achieved.

If, despite those atmospheric conditions, the B-29s were still getting enough of their bombs on target to do the job then the USAAF would've simply accepted the operational loss rates due to the engine problems and kept the raids going from high altitude. This, as USAAF strategic bombing doctrine called for.

Instead, the results were too poor and were taking too long to destroy Japan's war making capability. So, LeMay got sent out to the Pacific with orders to get more bombs on target - by whatever means necessary.

The change to low altitude night bombing was all - and only - about that. About getting enough bombs on target to do the job. The engine problems continued. Planes continued to be lost due to engine failures and fires. Crews continued to be killed due to those engine failures and fires. But as the new tactics were getting enough bombs on target those loses were deemed acceptable and the raids continued.

It was not the engine problems or any "structural issues" with the B-29s that caused the change from high to low altitude bombing - it was the failure of the bombing from high altitude to get enough bombs on target to do the job.
 
97,

You continue to confuse disagreement with much of what you declare, with missing the point. During much of late 1944-early 1945, as word of the operational losses of B-29s unrelated to enemy interception reached continental US despite censorship, it became a political football. The Truman Committee (with Harry Truman now vice president elect) continued its investigation of CW (the R-3350 program specifically), together with a mirror minority party group. It is a matter of record that indictments were discussed. Pressure was also exerted by military dependent groups. I do not know specifics but several general officers were transferred prior to LeMay' arrival on the scene and the (possibly political) change in mission structure.

I'm sure you and others are correct in stating that jet stream winds interfered with already inaccurate bombing. The winds did not blow continuously and their relationship to pressure patterns was becoming predictable. Bombing from lower altitudes on the basis of information on winds aloft from scout aircraft was also considered. Jet streams were not a surprise. Wiley Post employed jet stream boost to demonstrate ground speeds of up to 340MPH cross country in his Bendix supercharged Lockheed Vega at altitudes of 40,000 feet+ in 1934. In 1935 Tommy Tomlinson of TWA flew jet stream surveys, routinely, in a turbocharged Northrop Gamma, feeding data to what became the Irving Krick group. Daylight high altitude bombing of specific targets could have been continued at accuracy levels shown in Europe (I know, not very good there either) -if the airplane had been capable of reliably performing the mission at a (politically?) acceptable loss rate. As shown by the need to "silverplate" the nuclear delivery aircraft, the B-29 flown on normal missions was not.

Dynasoar (See Below)

Additional info. The Wiley Post Vega was two stage supercharged with an experimental Bendix oblique-flow blower the first stage and the integral supercharger the second. Post wore a full pressure suit on his high altitude flights which, unofficially reached in excess of 50,000 feet. He initiated a transcontinental non stop jet stream flight which encountered engine failure. His aircraft dropped its landing gear after takeoff and landed on a belly skid. This introduced problems with both the NAA and the FAI record recognition.

The Tomlinson TWA, so called 'overweather laboratory' jet stream exploratory flights were largely between Kansas City and Newark.
 
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On more mundane technical matters, come to think of it if the POD must be in 1943 i would think there is little time to do much, so to get a more effective high alt defence perhaps the POD should be earlier, like having the Ki-64, or rather a variant with conventional radiators, given priority. The concept was contemplated as early as 1939 by Takeo Doi apparently, so this actually have a good chance to be built in time. Like other japanese engines and aircraft of the era, the complicated extended shaft and the inline engines will give headaches, but nevertheless fitted with the O2 boost and four cannons, it will be a formidable machine despite the unreliability issues, far more effective than the OTL obsolete Ki-45.

Another favourite of mine is the Ki-94-I, this beast would have had two 30 and two 37mm guns iirc, so if it's not cancelled (development started in 1942 btw), and is given priority, it might possibly make it in production in 1944, but again the issue is the engine, so you either need to somehow get the engine earlier, or perhaps have it designed around two of the available Ha-45 fitted with O2 boost, with less power than the Ha-211 powered machine, true, but the resulting machine will still be a much more effective B-29 killer than any of the best OTL machines the japanese had.
 
I'm nowhere near as knowledgeable as you guys despite having tons of books on this very topic. However, I feel I should add my two cents from what I do know. The Japanese night-fighter force was deficient in two major categories, speed and radar. The two main night-fighters were the J1N1 and the Ki-45, used by the Navy and Army respectively. Both would have proved adequate against any other heavy bomber except for the B-29. This was because both were much slower than the B-29. In addition, only the J1N1 was given radar to any significant extent. Only a dozen Ki-45's ever got radar. Both of these problems could have been easily solved if the Ki-46 had been used instead. Not only was the Ki-46 faster than the B-29, it had relatively good high-altitude performance. According to the book Ki-46 Dinah by Martin Ferkl three of these planes were equipped with radar.
 
Not only was the Ki-46 faster than the B-29, it had relatively good high-altitude performance. According to the book Ki-46 Dinah by Martin Ferkl three of these planes were equipped with radar.

The Ki-46 was a stunning recce aircraft for speed and altitude. It had poor climb, and poor handling and failed at everything else.
 
Leo, et al
One of the possibilities for Japanese high altitude interceptors (which, after all was the topic of the thread) was explored on the back of an envelope. Turbine heat resistance using the alloys available in Japan at that time was relatively poor. Creep under centrifugal load essentially ruled out axial turbines which were the predominant type then in use. Back in the thirties Ohain in Germany used the radial inflow turbine to drive the compressor in his early turbojet engine. This is the turbine configuration used in automotive turbosuperchargers, and is much more resistant to thermal effects due to basic shape (good loadpaths) and more uniform rotor temperature conduction resulting from generally thicker sections. I'm not certain about the alloys used today, but they probably are not very exotic. Alternatively, I explored the following possibilities:

Inability of Japanese axial turbines to withstand exhaust gas temperature calls for some means of active blade cooling. Hollow sheetmetal blades come to mind with cooling air flowing outward driven by centrifugal force. Nothing new there and certainly possible in 1943 Japan. Similarly a portion of the exhaust shroud could be sectored out, allowing the blading to force externally ducted cooling air through the turbine disc. This would reduce power to the compressor, so a bigger turbine would be required. My great idea was to inject water into the engine exhaust, to reduce temperature while bursting into steam, to lower the temperature and increase the volume of the working fluid. Sounds ideal, but the numbers don't support it, at least on first analysis. At constant pressure the reduction in volume of the cooled exhaust is not compensated for by the volume of steam evolved. Similarly, the reversal of blade loading in the sectored cooling scheme might rapidly fatigue the turbine. Back to the hollow blades.

Dynasoar
 
Your POD specifies 1943, and Japanese turbo-jet development started in 1942, with a centrifugal compressor engine developed by Yokosuka. Low output spurred the addition of axial flow stages, making it too heavy. A further development was planned, but shelved favoring the Ishikawajima Co.'s efforts cloning a BMW from photographs. Mitsubishi and Hitachi had efforts to build centrifugal engines, but they had other things on their plate. Speaking of plates, it is possible that the habit of favoring chopsticks and sushi over cutlery and fried foods affected their odd taste in high-temp alloys. They had a yen for non-nickel alloys. Anyway, the Ishikawajima Ne-20 would always have come up a nickel short, time-wise and power-wise, at being a contender in the show. I think the longest running time was under 12 hours. There is an example on display at NASM.
 

thorr97

Banned
Dynasoar,

And yet the losses due to engine problems continued despite the change to low altitude bombing. If it were engine problems which caused the change due to the concerns over the losses they caused then those concerns would've only increased as the change in tactics did not end those engine problems or their losses.

Thus your assertion that it was engine problems is invalid and illogical.

What did change was the results achieved. By switching to low altitude bombing LeMay was able to get more bombs on target and that, in the end, was what mattered. B-29s were still being lost due to engine failures. B-29 crews were still dying due to engine failures. But more bombs were getting put on target and thus the non-combat loses were deemed acceptable for the increased results that came with them.
 
The Ki-46 was a stunning recce aircraft for speed and altitude. It had poor climb, and poor handling and failed at everything else.

The climb was indeed poor - almost 8 min to 5km (early versions), or 12 min to 8km. A peek at fuel carried ad engine power installed might give us a clue to the reasons of poor climb and handling. 1500L of fuel early on, to almost 2000 L (3 times as much as Ki 61) for late versions. More fuel than Bf 110 or contemporary P-38s but less engine power. The Ki-46, being a recce bird, we can compare it with recce Spitfires - they were fast, but we not much of climbers due to high weight.
Thus, the 1st step should be removing of some of fuel tanks to reduce it to 1000 L max - should suffice for an interceptor. Add a drop tank facility for just-in-case (in OTL there were two wing racks on later versions).
2nd step - more power at any altitude, but especially high up. By 1945 the Japanese need to have a working 2-stage engine in production and in service.
 
The climb was indeed poor - almost 8 min to 5km (early versions), or 12 min to 8km. A peek at fuel carried ad engine power installed might give us a clue to the reasons of poor climb and handling. 1500L of fuel early on, to almost 2000 L (3 times as much as Ki 61) for late versions. More fuel than Bf 110 or contemporary P-38s but less engine power. The Ki-46, being a recce bird, we can compare it with recce Spitfires - they were fast, but we not much of climbers due to high weight.
Thus, the 1st step should be removing of some of fuel tanks to reduce it to 1000 L max - should suffice for an interceptor. Add a drop tank facility for just-in-case (in OTL there were two wing racks on later versions).
2nd step - more power at any altitude, but especially high up. By 1945 the Japanese need to have a working 2-stage engine in production and in service.

Essentially, it requires a redesign for a different role. They did that, and called Ki-83.
 
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