High altitude air defense of Japan

Indeed, and actually a variant of Ki-83 (Ki-103?) was planned to replace the Ki-46 in service. If somehow the japanese would have managed to get the Ki-83 in service, even in a derated form, the B-29s would have been in a world of hurt so to say.
 
97,

A lot of back and forth could be eliminated if you would familiarize yourself with the realities of of a B-29 high altitude mission, and the differences if the long climb was to be eliminated.

Overload takeoff would be the same for both missions, with earthmoving equipment stationed at the end of the runway to remove disabled aircraft from the path of following aircraft already on the roll. As a pilot this already makes me uncomfortable, particularly after having had results described to me in O-Club conversations many years ago with pilots who were there.

If you would visit the engine technology sites that I suggested, some of the problems endemic to the carburetor equipped non-silverplate B-29s might be clearer. On takeoff at full throttle and sea level density, the ducting between the superchargers and the engine intake valves is packed with compressed air and 140 octane gasoline vapor. One sticking intake valve or backfire and the the volume explodes. The results might be as harmless as loosing the engine on takeoff and aborting the mission, or as often happened (including the first prototype B-29) the magnesium accessory case, followed by the crankcase itself ignites. The adjacent wing spar is next in line.

Available discussion in several of the referenced websites details the shortcomings of air-fuel mixture distribution (too little fuel and cylinder head temperature climbs past the maximum limit, too much and the spark plugs foul), chronic leaking cylinder cooling air baffles allow overheating, particularly involving back-row cylinders, leading to accelerated exhaust valve failures. The B-29 after a heavily loaded takeoff is essentially trapped in a situation where full throttle (not Maximum Except Take Off) is required to establish climb, but the cooling air outlet flaps on all four engine cowls must remain full open for engine survival. Look at a photo of a B-29; the cooling flaps are substantially larger then other radial engined aircraft, and produce increased aerodynamic drag, and turbulence over the wing, reducing lift when they are opened. There isn't much power available to climb until the airplane has consumed enough fuel to permit speed to be increased and ram cooling air flow thru the engine allows a reduction in cowl flap opening. At this point the required climb to 30,000 feet+, as compared with the power required a cruise-climb to 1/5 that altitude, makes a substantial difference in the survival of an incompletely developed and poorly manufactured engine. The increased manifold pressure required to climb to high altitude, like takeoff, is considerably harder on engine survival than long range cruise at lower altitudes. Abort to Iwo Jima or complete a much less demanding mission?

Mission completion rates (without regard to enemy action) were increased for low altitude raids. I'm looking for my copy of LeMay's biography which goes into the political aspects of the change to low altitude operations.

I can't help but believe that the certainty of your opinions originate with a lack of technical comprehension.

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

Indeed, and actually a variant of Ki-83 (Ki-103?) was planned to replace the Ki-46 in service. If somehow the japanese would have managed to get the Ki-83 in service, even in a derated form, the B-29s would have been in a world of hurt so to say.

Ki-83 was realy awesome - a no-nonsense twin engined performer. Shortcomings being that it was too late, and powered by experimental engines. Install the Homare on Ki-46?
 

thorr97

Banned
Dynasoar,

I can't help but believe that the certainty of your opinions originate with a lack of technical comprehension.

Seriously? Well, I guess my twenty five years working in the aerospace industry is all for naught then...

Please go back and actually read what I posted. Not once have I questioned whether or not the B-29's engines were problematic. Not. Once.

You however, have asserted that it was the engine problems alone which caused the change in tactics from high altitude bombing to low altitude.

That assertion however, ignores the fact that the engine problems continues despite the altitude change.

Thus the engine problems can not therefore be the cause for the change in tactics.

Yes, not having to climb to 30,000 feet meant less stress on the engines. It also meant not having to carry as much fuel aboard the planes since they avoided that fuel consuming climb.

That reduction in required fuel was seized upon by the mission planners as it meant they could stuff the B-29s with more bombs equivalent to the weight of that "saved" fuel. Thus the bombers still continued to be overloaded and the engines still had to be maxed out. And, what a surprise, the engines still continued to catch on fire.

Those engine problems continued and that meant they still continued to destroy aircraft and that they still continued to kill aircrews.

What also continued were the bombing missions.

The difference - and the only difference that counts - is that the change in tactics resulted in getting more bombs on target.

The non-combat operational loses continued at an appallingly high rate - no matter what altitude the planes were flown at.

But the new tactics were getting the results the Army demanded while the high altitude bombing tactics weren't.

Your assertions are thus invalid.

We do not disagree that the B-29's engines were horribly - and lethally - problematic. The losses they incurred were not however, sufficient for the Army Air Force to change its tactics. It was the failure of bombing from high altitude to achieve great enough damage quickly enough which dictated the change. Proof of this can be seen in the fact that the Army was quite willing to accept the continued non-combat operational losses the engines incurred so long as the B-29 raids were putting enough bombs on target.
 
Remember it was not just the altitude and time of day that changed for the B-29, it was also the bomb load. The USAAF decided that the distributed nature of all the "mom and pop" machine shops etc meant that pinpoint bombing, even if achievable, was not going to be as effective as desired. Therefor incendiaries were needed, even if mixed with HE. With the jet stream you can't drop incendiaries effectively from 30K ft. Given the poor state of Japanese air defense especially at night, the accuracy issues, and the switch to primary incendiary raids THAT is why the tactics were switched. As long as the loss rate, whether combat or noncombat, was at an" acceptable" level for the results achieved things would continue.

The USA was willing to adjust if the risks of using a given pane or tactic were seen as too much - look at the Corsair, it was restricted to land ops where it was very successful until operational issues with being safe to operate on a carrier were solved.
 
look at the Corsair, it was restricted to land ops where it was very successful until operational issues with being safe to operate on a carrier were solved.

Here we go again. "safer" was the operative word rather than "safe", but is not in fact the case. Fighting 17, Jolly Rogers, or Blackburn's Irregulars, developed and were cleared for carrier ops on Bunker Hill en route to Pearl when they were re-assigned to a land base for logistical reasons, honest. There's plenty of room for argument here, but the gist is true. They were no safer later, but they were faster than Hellcats.
 
97,

Seriously. Since you bring it up, I believe if we were to compare resumes in aerospace, you would come out on the short end by quite a margin.

First, I believe that somewhere in your responses you conceded that that the B-29 mechanical attrition rate was high and the R-3350 less than satisfactory.

You repeatedly stress no difference in these rates between the high altitude bombing missions the aircraft was designed to perform and the low altitude night raids of February through July 1945. This is nonsense!

In reality, the resumption of high manifold pressures required during the more than two hour climb from sea level cruise to design bombing altitudes was destructive to these marginal engines and resulted in significant aircraft losses enroute. Many flight methods were tried to reduce the crew and aircraft losses including step climbs with level cool-off periods between, steady climbs with rate adjusted to relative air density and abandonment of attempt to maintain formation (continuous throttle adjustment required).

When Ewo Jima became available (after the switch to low altitude night raids) over 2400 B-29s aborted there for a variety of reasons, but still flying. These generally survivable diversions further reduced the home front pressures to investigate non-combat crew losses.

The switch to incendiary raids was not entirely LeMays idea, nor did he bring tons of incendiaries with him to Saipan. In reality the AAF strategy from the outset was to bomb Japan with a mix of incendiaries and conventional HE from the B-29s design altitude. According to balkanoglasi.com an extensive replica of Japanese construction was built at at Dugway and tests were conducted between May and September 1943 to develop specialized incendiary bombs (M-47, M-69).

On Nov 29 & 30, 1944 the first high altitude mixed incendiary-fragmentation raids on Tokyo were termed highly successful. Perhaps the wind wasn't blowing on those days. During July and early August 1945, High explosive raids were resumed, this time at altitudes where it was calculated that the loss of B-29s to enemy interceptors relative to losses from friendly R-3350s was to be optimal. 12,000 feet. Accuracy was said to be acceptable.

Though at the moment I have no references, I believe that most of LeMay's (actually my far distant early CO before transfer to ATIC/ARDC at Wright Patterson) low altitude raids allowed the weight reduction arising from deletion of gunners and armament to reduce aircraft losses on takeoff, rather than to load on more incendiaries. A sop to the Truman committee?

In summary, the B-29 was designed for over-target altitudes on the order of 30,000 feet, like its predecessor aircraft, the B-17 and B-24. It proved to be unable to do this reliably, which provoked congressional investigation(s), considerable adverse publicity and a massive shakeup of the military leadership involved in its use. In reality over-Japan operations the high altitude were unnecessary due to inadequate enemy interceptors (Remember? It was the topic of this discussion) and jetstream winds were sometimes encountered which could explain poor "precision" bombing results in the absence of quantities of incendiaries originally developed for use against Japanese cities.

The B-29 engines improved with experience- engine change time dropped from several days to a few hours- but, as I remarked in post #1, the aircraft did not reliably meet its performance specs. But as an investment comparable to the Manhattan Project, it was "Too big to fail". I believe that Lemay's strategy was clearly war winning, but precision bombing combined with newly available cannister contained incendiaries (E-46) conducted at less windy and more attainable lower altitudes would have worked as well.

Dynasoar
 
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thorr97

Banned
Dynasoar,

Once again you have failed to uphold your premise.

You have nothing but your own assertions that it was "problematic engines" which were what caused the change in tactics. On the other hand, several of us in this thread have already demonstrated - repeatedly - the link between the increased damage done to Japanese targets and the bombing of them from the lower altitudes. This, while the R-3350s continued to be used in those bombing raids and continued to be problematic, continued to catch fire, continued to destroy aircraft and continued to kill their crews. All of which rather decisively rebuts your assertions as to the effect of the engine problems on the strategic bombing tactics employed against Japan.

I see that you're fully enamored of that most recent B-29 book you've read which details the woes of Wright's Duplex-Cyclone engine program. That's wonderful. That engine program makes for an excellent study on many levels; technical, industrial, and historical. The thing is, no one in this discussion thread has contested - or even hinted at contesting - that the R-3350s were problematic engines which caused loses in their use. You however, seem to believe that it was the engines and engines alone which were the ultimate force in the history of the B-29's use in World War Two. And thus you are being willfully blind to the facts which contradict and demolish your premise.

If the high altitude B-29 raids had been getting the results the military demanded then they would've continued - despite the loses continued use of the R-3350s incurred. That adopting low altitude bombing attacks achieved better results than the high altitude attacks meant that they become the tactic of preference - this, despite the continued loses incurred from continuing to use the R-3350s. The military deemed those loses worth the cost being able to put more bombs on target and thus continued with those raids.

You are also focusing on the engine problems out of context. The overall loses the B-29s incurred in their operations in the Pacific against Japan were at a significantly lower rate than the loses the B-17s and B-24s incurred over Europe. The B-29s also flew vastly greater distances than those other bombers of their missions and carried vastly greater bomb loads. All of which were factored into the military's continuing to use the B-29s to wage the airwar against Japan despite the problems with the plane's engines - problems which continued no matter what altitude the plane's were flown at. Yes, climbing to high altitude placed a significant strain on those engines. But being maxed out on bomb and fuel loads while flying at low altitude also placed a significant strain on those engines. As a result, they caught fire sometimes. And sometimes that fire went out of control which caused the loss of the aircraft. And sometimes that also caused the loss of the crew.

You can cite "air-fuel mixture distribution" "high manifold pressures" and "cylinder head temperatures" all you wish but that doesn't change the fact that it was getting bombs on target which drove the tactics used. Bombing from high altitude didn't get enough bombs on target. Bombing from low altitude did. Non-combat operational loses continued at whatever altitude the missions were flown. The military planners deemed those loses acceptable and continued sending the planes out on those raids despite those engine problems.

Thus it can not have been the engine problems which caused the change in tactics.
 
I see that you're fully enamored of that most recent B-29 book you've read which details the woes of Wright's Duplex-Cyclone engine program. That's wonderful. That engine program makes for an excellent study on many levels; technical, industrial, and historical. The thing is, no one in this discussion thread has contested - or even hinted at contesting - that the R-3350s were problematic engines which caused loses in their use. You however, seem to believe that it was the engines and engines alone which were the ultimate force in the history of the B-29's use in World War Two. And thus you are being willfully blind to the facts which contradict and demolish your premise.

A little snarky, 97. Yes, I've read books, and also written several thousand pages of technical analysis for the Air Force, most funded by Wright Air Development Center. If you are interested, using the Forum search function, you could piece together some of my resume. My views on wartime and postwar B-29 performance were formed long ago, when assigned to the WP Powerplant Lab and encountered senior officers who had been there. If I had anticipated word parsing in my initial posting, I might have added "...and the increasing availability of quantities of area weapons", even though it was unnecessary in the context of the Topic.

While it was difficult to extract, you seem to ultimately concede that a two hour climb might possibly result in more engine problems than sea level cruise. In this regard, for the last week or so, I've been searching for a Doctoral Thesis I was asked to review some time ago. Finally located it on the internet It contains several direct quotes from Gen. LeMay on this topic which you will probably find in error, but let's try anyway.

Interestingly, it would be difficult to conduct massive incendiary raids until the bombs became available in quantity; The final report of the Joint Incendiary Committee (look it up) was not issued to the War Department until late September 1944 for bomb procurement. The incendiaries used on the November raids were leftovers from ETO.

I'm ending this post so that it is not lost in my uploading the thesis excerpts
 
Hopefully the things can be steered in calm waters :)
Back on the topic. Mitsubishi produced an engine that does not get much talk about, the Ha 42, that was used to power the Ki 67 bomber. At least 1500 of those engines were produced, judging by the number of the bombers produced. The 18 cyl engine was making 1640 HP at 20000 ft, diameter 54 in, dry 2080 lb, fan cooled; technical data from the Allied TAIC document. Design a Tempest-sized fighter around one of these, 4 cannons, and call it a day?
 
To me is not could Japan have designed a decent high altitude interceptor, they probably could have. Given the difficulties Japan had with producing high power engines and difficulties with metallurgy, their issues with amounts of high octane AVGAS, and the overall issues with Japanese aircraft production in the late 1944 period and beyond, exactly how many could they have produced. Once produced how much could they fly - would Japan use AVGAS for interceptors or keep hoarding it for the kamikazes saved for "invasion"? Given these would be the most advanced/high tech fighters Japan produced, maintenance will be an issue. Given the poor state of Japanese radar/air defense, how effective would be the relatively limited numbers of high performance high altitude fighters be against the daylight raids at high altitude - they won't have much time to get to altitude before the B-29s drop their bombs. Once the USAAF shifts to low altitude night time and incendiary raids, these fighters are pretty useless - single seat fighters with no radar direction and no onboard radar were shown to have limited effectiveness.
 
97 et al

Here, entirely unedited, are pages from 131 to 136 of a document that I recalled covering B-29 operations during the transition from high altitude precision bombing to low altitude area incendiary saturation and back to medium-low precision bombing. Some of my statements and conclusions appear to be endorsed by quotes from LeMay, but of course he may be wrong.

<<180 Degrees Out: The Change in U.S. Strategic Bombing Applications, 1935-1955

By C2008

John M. Curatola B.A. University of Nebraska, 1987

M.A. George Mason University, 2001

M.M.A.S. U.S. Army Command and General Staff College, 2002

Submitted to the Department of History and the Faculty of the Graduate School of the University of Kansas

In partial fulfillment of the requirements for the degree of Doctor in Philosophy

Date defended: October 21, 2008



The number of problems that the B-29 experienced took years to correct and the Air Force was still modifying the plane when withdrawn from service in the late 1950s.126 As for the R-3350 itself, it eventually became a reliable design and was eventually utilized on the Douglas AD-1 Skyraider attack aircraft and Lockheed Constellation airliner.127 The first operational B-29 raid occurred against the Makasan Rail yard in Bangkok, Thailand in June 1944.128 Despite the promise of the design, this raid yielded disappointing results. Out of the one hundred B-29s launched for the mission, only seventy-six returned to their home station having dropped their bombs.129 Eighteen had to turn back due to mechanical failures and six others had to ditch or land at alternate airfields.130 During the first XXI Bomber Command mission against Japan on November 24, 1944, twenty-six out of the one hundred and eleven aircraft launched were forced to turn back or abort enroute due to mechanical difficulties.131 Natural phenomenon accounted for many aborts as the temperature differential between the tropical conditions on the ground coupled with the freezing temperatures at altitude caused considerable problems for both the airframe and aircrew.132 During these early operations the number of B-29s bombing the primary targets declined as crews either bombed secondary targets or salvoed their bombs harmlessly.133 Most of the aircraft losses during the first B-29 missions were due to mechanical failures as the long climb to thirty thousand feet stressed the R-3350 engine.134 After studying B-29 performance, LeMay decided that he needed to bring 132 the bombing formations down to lower altitudes where the engines and other equipment would not be under such constant strain.135 By lowering B-29 cruising and bombing altitudes, the stress on engines was significantly reduced. This reduction in stress on the engine lowered operating temperatures of the cylinders that increased aircraft operational availability. The long strenuous climb to high bombing altitudes and the fuel weight associated the climb was reduced when B-29 aircrew lowered their operating altitudes from thirty thousand to ten thousand feet. Through his observation of operational missions LeMay concluded that: With the overheating engines, it began to seem that this high altitude stuff was strictly for the birds. The airplanes had been breaking down. There are something like 55,000 different parts in a B-29; and frequently it seemed that maybe 50,000 of them were all going wrong at once. I felt that the majority of our losses were due more to our own mechanical problems than they were to the Japanese defensive system. [The] Main thing to do, it seemed, was to get them [the B-29s] down in altitude. Then we’d get a lot more hours service out of each engine.136 After making mission profile changes, LeMay found that 91 percent of all B-29s bombed their primary targets instead of the abysmal 36 percent from previous missions.137 Because of the reduction in altitude, maintenance “down time” dropped and more bombers became available to conduct bombing raids. Since the engines avoided the stress of climbing to thirty thousand feet, the number of mechanical failures dropped and aircraft availability rose. During the March raids, aircraft availability climbed appreciably from 59 to 83 percent.138 Additionally, the decision to lower bombing altitudes also went hand-in-glove with the desire to avoid bombing through the difficult Japanese weather while also evading the excessive winds of the 133 jet stream. As well, this drop in operating altitudes was to yield a third and more deadly benefit for LeMay and the 20th Air Force. In addition to the heat, fire, and valve problems, the R-3350 also did not produce the power necessary to fly the new bomber and its advertised payloads. Since aircraft performance is dependent upon density altitude (the amount of air molecules in a given body of air), the hot weather combined with the weight of the B- 29 had severe consequences for B-29 aircrew. During CBI operations in October 1944, LeMay wrote to Arnold, and stated: To a large extent our bomb load is limited by gross take-off load. This is in turn influenced by operating technique, runways, high free air temperature and power available. The take-off is a very serious problem with the B-29, and is the high point of any flight. All crews, in discussing a mission, invariably talk about their take-off and not about flak, fighters or other enemy opposition. Even partial power loss from one engine almost invariably results in a crash from which there are very few survivors.139 Later in the letter LeMay further stated: The B-29 airplane is capable of considerable higher performance than the R- 3350 engine now installed will permit, as the maximum gross weight is limited by power available for take-off and climb. Until more power is available, we cannot fully capitalize on the capabilities of the airplane.140 By lowering bombing altitudes, LeMay allowed for increased bomber payloads. Because LeMay was anxious to increase aircraft sortie rates and try to work around the uncooperative Japanese weather, the lowering of cruise and bombing altitudes allowed the B-29 to carry a larger bomb load. According to LeMay: One of the main advantages in going down to less than 10,000 feet over the target was the increased bomb load. We could increase the bomb load of each plane from about two and one-half tons to 10 tons. This was possible because each individual attack required no assembly into formation over the base at the start of the mission, and because aircraft would go directly from base to 134 target and return, saving tremendous amounts of gasoline. Better weather would be encountered at lower altitudes and the heavy gas-consuming winds of high altitudes would be avoided. The weight of extra crew members, armament, and ammunition would go into bombs.141 The amount of fuel a B-29 used to climb to bombing altitude, given a specified weight, could use as much as twelve hundred gallons (weighing seven thousand two hundred pounds) when climbing at a gross weight of one hundred and thirty thousand pounds. In order to compensate for this fuel weight, power settings had to be increased for the long climb to altitude, creating an additional strain on an engine.142 When bombing by prescribed USAAF methods, the weight of bombs carried in the B- 29 had to be reduced from ten to three tons because of the fuel needed to climb to and fly at higher altitudes.143 An average B-29 used seven thousand gallons of gasoline on a mission. The pragmatic LeMay surmised that using over twenty-one tons of fuel to drop three tons of bombs did not make sense.144 He determined that by lowering altitudes, and negating the requirement to carry the fuel used for climbing to high altitude, bomb loads increased significantly.145 The B-29’s poor high altitude performance necessitated the lowering of bombing altitudes and this is turn facilitated higher aircraft reliability figures while simultaneously allowing larger payloads. In this regard mass became an important aspect of the American bombing effort. Increased number of B-29s equated to more destructive and deadly raids. American industry built bombers and fighters at a rate with which the Axis powers could not cope. This massive air armada overwhelmed axis air defenses. Toward the end of the war in both the Pacific theater as well in European, mass itself became an important aspect of the strategic campaign. As more 135 planes and aircrew became available, more bombs were dropped. This same application of mass became ever more important in American strategic methodologies in the nuclear atomic age. The technical problems of the R-3350 engine and the B-29 mandated that mission profiles be adjusted to utilize lower altitudes. This change in profiles in turn facilitated the hauling of larger and more destructive bomb loads of M69 incendiaries. By summer 1945 much of the Japanese homeland became a vast wasteland. Certainly, one of the primary reasons for this was the substantial rise in the number of B-29s over the islands and the greatly increased bomb tonnage dropped on each mission. With lower altitudes, LeMay was able to raise the 2.6-ton load of each aircraft to 7.4 and keep more aircraft in the air.146 The ability to carry more bomb tonnage meant greater destructiveness. Despite the fact that the B-29 was designed for high altitude precision bombing, the state of the 20th Air Force and the imperfect design of the airframe required a modification to bombing operations. The USSBS noted that: The preceding 9 months had seen the B-29 committed in general to the doctrine of very high altitude precision bombing. Designed specifically for this type of operation, it was logical and mandatory that the doctrine be thoroughly tried before it was modified. Many factors militated against the achievement of this objective, among the foremost of which were insurmountable weather obstacles, strain imposed on equipment by high altitude operation, insufficient force, low sortie rate, and low bomb loads.147 The Survey further noted: By lowering the bombing altitude, the effectiveness of each B-29 was increased tremendously. Bomb loads more than doubled; using radar bombing methods the weather ceased to be a serious factor; the number of aircraft dropping on the primary target soared from 58 to 92 per cent . . . decreasing bombing altitude meant less operating strain which added up to more sorties per air craft.”>>

Sorry for the lengthy excerpt, but it was presented without editing. The numbers, of course, reference footnotes. Anticipating some quibbling, the term "insurmountable weather obstacles" refers to cloud cover and fog as well as winds. When I have more time, I'll paste the web address so you all can read all 200+ pages including footnotes and more of LeMay's observations about where the "bugs" resided in the '29.

Dynasoar
 
Dr Curatola's Thesis which presents LeMay's quotes in support of my comments initiating this thread:

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.)

can be found here

Some of them are pretty lively, particularly his description of where the B-29 bugs were to be found. (under the engine cowlings....)

Returning to the subject of this thread, Japanese air defenses required to counter a B-29 capable of meeting its performance specifications-

As a kid, I used to spend my Junior High School lunch money buying used magazines, six for a quarter. (The contents of that store would be priceless in copies of thirties Astounding Science Fiction alone) I would buy Popular Science, Popular Mechanics and Mechanix Illustrated. In one of these, circa 1940 was an article on what would later be called guided missiles. The one that caught my attention (in the absence of rocket boosters and RADAR was a surface to air device powered by a wild two-stroke engine driving coaxial pusher propellers. It had three slender wings at 120 degrees, and at the tip of each wing was a probe supporting a directional microphone filtered to be most receptive at bomber engine frequencies. The electronics required to blend the three inputs to home on the target were trivial, even at that time. The missile (pilotless airplane) was intended to have enough thrust to climb vertically, and be able to overtake a bomber in a tail chase.

A hypothetical 1943 version would doubtless be rocket propelled, but a simple and cheap SAM predecessor.

Dynasoar
 
I doubt that napkinwaffe would work. You'll need to filter out the noise from the engines/props of the "missile" before it can find a bomber, and the same applies for rocket noise. Furthermore, most bomber formations/streams are dense enough it would be difficult for such a system to home in on any one bomber...
 
The same questions about ability to filter out boundary layer noise and discriminate a target in a dense formation occur to me as well. No real problem making the sound sensor sufficiently directional to eliminate propulsion noise from rear.

It seems to me that acoustic homing in air might have been tried prewar (Britain?), but can't find any info.

Dynasoar
 
Before radar sound location equipment was used to aircraft detection and location. UK, US, Germany, Japan and others all had this - it was not terribly effective.
 
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