High altitude air defense of Japan

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
 
First and foremost, get GM1 to boost existing planes combat ceiling. Next get any or all of the next generation heavy interceptors in production - all fitted with GM1, and forgetting about turbos, namely any or all of Ki-64, Ki-83, Ki-94-I, Navy's J5N. Try to get multistage engines on them. Get an Ki-84 variant fitted with larger wings and GM1, then with multistage Ha-45 engine, and get the Ki-87 and/or Ki-94-II with a simplified engine (no turbo), as well as the Navy's A7M-J, and N1K-J types. Finally, develop jet fighters such as Ki-200 fitted with AA rockets and also Ki-201 with same (get them from the germans somehow).

This is of course off the top of my head as far as fighters go, the ideal response to the threat which could be within Japan's technological reach, however whether the japanese can do it due to the known resource limitations is another matter. But getting at least few of these possible responses in production should be doable, and any of them will be a far cry in capability compared to what they had in OTL.

As to AA, perhaps getting super-heavy AA guns might be possible, and/or of course rockets and guided missiles, but of course such advanced technology might not become available in time to make any impact (after all the americans will still get the atomic bomb in mid-1945).

As to other responses, kamaikaze the heck out of any B-29/B-32 base in range regardless of the cost, any B-29/B-32 destroyed is one less above the mainland, send suicide commandos as often as possible, and other such tactics.
 
There was no great secret that aero engines needed more than one stage of compression in orcer to achieve good hi-alt power. Bristol and Junkers captured several altitude records with engines that employed 2-stage superchargers, Junkers even experimented with 3-stage S/C. So the Japanese engineers need to recall what was done less than decade a go, and engineer the 2-stage supercharged versions of their most capable current engines (say, Kinsei, Kasei, Ha-109, Ha-40) as a 1st step of 'conquering' altitudes of 25000 ft and above.

Please note that terms '2-stage' and '2-speed' S/C are very different terms. Japanese have had many aero engines where the supercharged was geared via 2-speed gearbox, but their in-service engines wers always employing 1-stage compressing of the fuel/air mixture.

At any rate, I'd avoid spending money on the heavy AAA. Though, guided missiles might work?
 
Please note that terms '2-stage' and '2-speed' S/C are very different terms. Japanese have had many aero engines where the supercharged was geared via 2-speed gearbox, but their in-service engines wers always employing 1-stage compressing of the fuel/air mixture.
I'm aware of that, on the note of high altitude engines i recall reading about various engine variants (Homare, Kasei, MK9 etc.) with single-stage THREE-speed superchargers, which perhaps it's not quite as good as a two-STAGE variant (with 2 or more speeds), but still an improvement. Wonder which one is easier to built? The germans toyed with such 3-speed designs too afaik.
 
Unquestionably less engine power is diverted into a more efficient compressor, and a multi-stage centrifugal machine usually requires less power for a given level of (high pressure ratio) performance. At high altitude, at low air density this is a major factor, with increased blower RPM ratio cubing the power required, thus an increasing percentage of engine shaft power is expended driving the the multi-speed blower. The ideal means of maintaining high manifold pressure would be a mature turbosupercharger. Japan expended quite a bit of R&D examining and testing turbos from downed US aircraft, including flight test of an installation on an indigenous airplane (I have no info as to type or results). Lots of effort by several well known groups to develop a workable unit, but a long-lived turbo was never available.

If it had been up to me to develop a means of getting interceptors to B-29 flight levels with a minimum of powerplant modification, I'd certainly have considered the use of some readily available oxidizer. As I recall, both N2O, (nitrous oxide) and high test hydrogen peroxide were not readily available in late-war Japan-nor were nitro or tetranitromethane, hydrazine or other rocket exotics. Considering the first two, both of which were used by the Germans (GM1 was N2O) to boost engine performance, neither was able to stored in volumes sufficient to be available throughout late climb and anti-bomber manuvering. N2O in liquid phase had to be held in a pressure vessel and weighed 44 units for each 16 units of oxygen (using molecular weights); Hydrogen peroxide (assuming 100%) cost 34 units for each 16 units of oxygen, and did not require pressurization, but 18 units of water or steam had to be dumped overboard. I believe the answer was readily available liquid oxygen, metered into the carb along with appropriate fuel enrichment (16 units of O per 16). Power to blower would drop directly with air density, while engine power output would be about sea level rated. (Reduction in blower load would be a little less than loss due to compression pressure decrease- High compression pistons might easily restore this.)

Liquid oxygen into the standard blower, evaporating, would produce a desirable temperature into the cylinder, restore sea level power during climb and at altitude for a much longer time (for installation weight) than GM1.

Naturally aerodynamic mods, regardless of interceptor type would be necessary- higher aspect ratio wings of increased area with bomber capable cannon for starters.

But much more technology and tactics would be necessary to drive off B-SAN.

Dynasoar
 
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I'm aware of that, on the note of high altitude engines i recall reading about various engine variants (Homare, Kasei, MK9 etc.) with single-stage THREE-speed superchargers, which perhaps it's not quite as good as a two-STAGE variant (with 2 or more speeds), but still an improvement. Wonder which one is easier to built? The germans toyed with such 3-speed designs too afaik.

The DB 601/603/605 were featuring an infinite number of speeds for their 1-stage superchargers, yet a two-stage, 2-speed Merlin bested them at altitude. German 3-speed gearbox for the S/C was incorporated on the Jumo 213E and 213F that were also 2-stage engines. Pratt & Whithey engines with 2-stage S/C were featuring geaboxes with high, low and disengaged 1-st stage, so with a bit of good will we might also consider them as 3-speed types.

My point is that 2-stage supercharging brings real advantage above 25000 ft, while 3-speed gearbox is a nice-to-have item. It would've probably been easier for Mitsubishi to came out with 2-stage supercharged Kasei than it was case with the fan-cooled variant, while Nakajima might have easier time to produce the 2-stage Ha-109 than go with all-new Homare. Or Kawaski forgetting the Ha-140 and going on with 2-stage Ha-40.
 
The Japanese need engines they can't produce. Get missile technology from Germany but let's face it, it won't work well if at all. And that's assuming they can produce any of it at all.

Japan did have a 100mm and a 120mm AA gun, maybe get the German 128mm and 150mm into production.

Surrendering sounds like a reasonable plan at this point...
 
It may seem like a small point, but the Japanese seemed to have had an effective fighter force to meet high altitude B-29 raids from China in 1944, giving the raid of August 20, 1944, on the steel industry at Yawata an unsustainable loss ratio. The smelter wasn't hit again until after Hiroshima, by a low altitude night raid by 3 times the number, and highly burned out. It has been said that this raid saved Kokura from the Bomb, because Yawata's smoke obscured Kokura. A more effective night-fighter force might have come in handy at some point. In the end, with the taking of Tinian and Saipan, surrender sure did sound reasonable. Opinions differ.
 

thorr97

Banned
Dynasoar,

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.)

Say what? "Only marginally successful due to engine performance and durability shortcomings?" Where'd that one come from? The reason the high altitude daylight raids were dropped in favor of the low level night raids was the jet stream. Bombing from 30,000 feet altitude put our bombers up at altitudes where they encountered jet streams for the first time on a regular basis. Those blew our bombs all over the place and made getting the desired target destruction rates too slow. The Japanese were horrified at the damage the B-29s were inflicting by those raids.

The USAAF planners however, wanted faster results and thus they demanded something different. LeMay went for the low altitude incendiaries to burn it all down. It wasn't the engines or durability which was the problem it was encountering newly discovered atmospheric conditions combined with an increased demand for faster results.
 
Thorr 97

The performance and reliability problems with the Curtiss Wright R -3350 engine in the B-29 are a matter of sad record. Try reviewing the recent thread " Earliest possible introduction of B-29 bomber" and get back to me.

Dynasoar
 
continuing with possible late war Japanese countermeasures to high altitude B-29 raids; There were several programs involving "barrage rockets". At least one, the Funryu 4 (see spacelines.org) was liquid fueled, had an initial weight of 4190 pounds and could attain 650 MPH climbing to 105,000 feet. While there was a warhead, I haven't been able to document its weight. Combining this propulsion with an Ohka-like airframe might provide a manned SAM that, depending on warload, could shoot on the way up and detonate coming down. Certainly a weapon that would not have to rely on German technology.

Dynasoar
 

FBKampfer

Banned
Unquestionably less engine power is diverted into a more efficient compressor, and a multi-stage centrifugal machine usually requires less power for a given level of (high pressure ratio) performance. At high altitude, at low air density this is a major factor, with increased blower RPM ratio cubing the power required, thus an increasing percentage of engine shaft power is expended driving the the multi-speed blower. The ideal means of maintaining high manifold pressure would be a mature turbosupercharger. Japan expended quite a bit of R&D examining and testing turbos from downed US aircraft, including flight test of an installation on an indigenous airplane (I have no info as to type or results). Lots of effort by several well known groups to develop a workable unit, but a long-lived turbo was never available.

If it had been up to me to develop a means of getting interceptors to B-29 flight levels with a minimum of powerplant modification, I'd certainly have considered the use of some readily available oxidizer. As I recall, both N2O, (nitrous oxide) and high test hydrogen peroxide were not readily available in late-war Japan-nor were nitro or tetranitromethane, hydrazine or other rocket exotics. Considering the first two, both of which were used by the Germans (GM1 was N2O) to boost engine performance, neither was able to stored in volumes sufficient to be available throughout late climb and anti-bomber manuvering. N2O in liquid phase had to be held in a pressure vessel and weighed 44 units for each 16 units of oxygen (using molecular weights); Hydrogen peroxide (assuming 100%) cost 34 units for each 16 units of oxygen, and did not require pressurization, but 18 units of water or steam had to be dumped overboard. I believe the answer was readily available liquid oxygen, metered into the carb along with appropriate fuel enrichment (16 units of O per 16). Power to blower would drop directly with air density, while engine power output would be about sea level rated. (Reduction in blower load would be a little less than loss due to compression pressure decrease- High compression pistons might easily restore this.)

Liquid oxygen into the standard blower, evaporating, would produce a desirable temperature into the cylinder, restore sea level power during climb and at altitude for a much longer time (for installation weight) than GM1.

Naturally aerodynamic mods, regardless of interceptor type would be necessary- higher aspect ratio wings of increased area with bomber capable cannon for starters.

But much more technology and tactics would be necessary to drive off B-SAN.

Dynasoar


The Germans had good experience with methanol-water injection (and late model 109's were able to carry a sufficient volume that on a low-flow setting, they would expend their fuel before the MW50).

I would expect this to be a more effective answer to Japan's problem.
 
F.B.,

Water-methanol injection is employed to suppress detonation, typically encountered at low altitude, high manifold pressure and temperature conditions. During high altitude operation the problem is inability to develop the intake manifold conditions that would produce detonation at all. The engine is starving for oxygen. An ideal situation for W/M injection, full time and at a rate approaching fuel flow, is flying in the Reno unlimited pylon race.

Dynasoar
 

thorr97

Banned
Dynasoar,

The performance and reliability problems with the Curtiss Wright R -3350 engine in the B-29 are a matter of sad record. Try reviewing the recent thread " Earliest possible introduction of B-29 bomber" and get back to me.

Please note where I stated that the B-29's engines were not problematic. Go ahead, we'll wait...

In the meantime, it wasn't the engine problems which caused the high altitude bombing campaign to be abandoned - it was the atmospheric conditions at those altitudes which reduced the bombing accuracy to unacceptable levels. Well, unacceptable levels for the USAAF command at the time in the war. Hence the change to the low level incendiary raids.

And also note that those low level raids were conducted by the same B-29s using those same Curtiss Wright R-3350 engines with their "engine performance and durability shortcomings." If, as you assert, it was the failure of those engines which caused high altitude day bombing to be "largely abandoned" then continuing to have used those same engines would've meant continuing having the same "engine performance and durability shortcomings" sufficient to cause that bombing campaign to be abandoned as well.

Seeing as how the bombing missions continued even with those same problematic engines it could not therefore be the fault of the engines that the high altitude attacks were discontinued.
 
97,
While you are waiting, visit the Aircraft engine historical society website, which has an extensive non-member area. There you should be able to learn a little about the CW R-3350 and the of the massive overheating and explosive backfire problems encountered during takeoff and climb to altitude, together with the B-29's inability to climb effectively with cowl flaps open as needed to provide some degree of engine cooling. The short term solution was to eliminate the engine killing climb to altitude without admitting aircraft shortcomings.

Warning- it is a little technical. You might do better by first referring to the post I suggested to you in my previous #11, "Earliest possible introduction of B-29 bomber".

Also, look up "Silverplate" in this context. Standard issue B-29s, even in mid 1945 were not considered sufficiently reliable for nuclear missions, largely for the engine issues you appear to casually overlook. The entire carburetor fuel metering system (source of many aircraft losses), had to be replaced with an intake port fuel injection system, cylinder cooling baffles custom fitted, intake and exhaust valves sonic tested for leaks, together with ignition system rework and a number of other modifications unavailable to regular aircrews.

Dynasoar.
 
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B-29 engines weren't good early on, or even in the middle, but they were capable of bombing Japan from China in 1944, ay 30,000'. The abort rate was high, and non-combat losses high as well. In the Aug. 20, 1944 raid I mentioned, combat losses were high as well. In addition, it was discovered that only one bomb landed within the target area of the steel works, causing minimal damage, although a fifth of the city's housing was destroyed. The logistics effort, much by the same B-29s themselves, to stage this raid by 71 B-29s, was monumental, and the result achieved was one bomb on target. Japanese sent up 100 intercepters, no turbos or two-stage superchargers, and took a fair whack at the bombers, suffering losses as well. A look at performance figures show that even an Oscar can intercept a B-29 at 30,000' in 12 or 13 minutes, while the figure is 10 minutes for a Hayate/Frank. Japanese efforts to built turbocharged fighters preceded the OP's time frame, but bore only as much fruit as efforts to make a reliable R-3350. The standard Hayate's Homare engine wasn't the pinnacle of reliability either. Nor was the quality of Japanese fuel. Nor was the quality of Japanese fighter radios, at least for the Zekes. Not much of any information on Army fighter radios exists. Japanese radar was in operation by both the Army and the Navy, but there was no overall fighter control command, and, of course no cooperation or communication between Army and Navy. There was no Dowding-san. The augmentation of high-altitude performance doesn't seem like such a critical factor during the China period of B-29 attacks. By the time of the loss of Tinian and Saipan, Iwo Jima, and Okinawa, it was all pretty much moot anyway.
 
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Japanese sent up 100 intercepters, no turbos or two-speed superchargers, and took a fair whack at the bombers, suffering losses as well.
...

Just a nit-pick: Japanese aero engines from mid- and late-war were outfitted with two-speed superchargers.
 
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