Could proximity fuses have halted the bomber offensive against Germany in 1944?

[pattle]

This is just another what if thread so I don't think anyone can say with any certainty what exactly would of happened had the Germans of had access to proximity fuses, but for me one things for sure and that is it would of helped the Germans more than it helped the Allies. Under the circumstances that the Germans were in during late 1944-45 it sounds to me as though proximity fused ground defences would have been a safer bet than Me262's and the other wonder weapons. I think though that the Me262's and jet fighters are in general a far more interesting topic for discussion than boring old artillery fuses and this is why we don't hear so much about them. Nobody looks at a picture of a fuse and says wow.

 

[OldSkeptic]

This is just another what if thread so I don't think anyone can say with any certainty what exactly would of happened had the Germans of had access to proximity fuses, but for me one things for sure and that is it would of helped the Germans more than it helped the Allies. Under the circumstances that the Germans were in during late 1944-45 it sounds to me as though proximity fused ground defences would have been a safer bet than Me262's and the other wonder weapons. I think though that the Me262's and jet fighters are in general a far more interesting topic for discussion than boring old artillery fuses and this is why we don't hear so much about them. Nobody looks at a picture of a fuse and says wow.

Agree, my take on this is that if the Germans had managed to mass produce (and don't forget, re my earlier post, they had a big head start, ref Oslo Report) a proximity fuse then a lot of the day and night USAAF/RAF long range bombing campaigns would have failed and been called off. With unforeseeable impacts, though some would argue that it would have been better for the Western Allies that way.... just saying.

 

[parsifal]

I have to admit, I am having some second thoughts about this discussion. VT fuses, were valuable, its a question of whether they would make a difference for the German situation

 

[JtD]

If a proximity fuse was devastating, would the Allies cancel the bombing or invent counter measures?

 

[stona]

Nobody convinced me that the proximity fuses would transform Luftwaffe flak into a weapon system capable of devastating allied formations. The Luftwaffe originally thought they needed to get the shell (88mm) within 30m of a bomber to destroy it. This was revised down to 3m. That's the problem. Your projectile needs to pass within 3m of the target to be "devastating" and nothing here has convinced me that this was possible often enough to have a huge effect on allied losses.
Cheers
Steve

 

[yulzari]

If we assume that artillery shell proximity fuses were a task too far for the Luftwaffe, but that rockets could have carried a feasible Luftwaffe proximity fuse then the discussion has looked at the guided rocket projects.

However, could this not be more easily done by unguided air launched rockets? Simply (and I know it is not quite that simple) amend existing air launched rockets to be proximity fused instead of the normal fusing? e.g The Wurfgranate 21 that was in use from mid 1943. Accuracy would be less important so it would be sufficient to launch them at the USAAF 'box' rather than a specific aeroplane and from out of effective range of the .5" defensive bomber guns. In fact a logical response could be to remove the defensive armament to allow the bomber to fly higher and cruise faster to make them more difficult targets, relying on fighter escorts to engage the Luftwaffe fighters.

At night the heavy bomb loads demanded by the RAF left them well within standard 88mm range so an AA proximity fuse would be more to be feared by the RAF. In fact, by the time a night fighter is close enough to identify it's target it is probably close to the damage range of a Wurfgranate 21 warhead and not far off the proximity range of such a fuse.

 

[bbear]

In 1944 Germany would not be able to produce VT fuses for AA. It took a US programme of a scale and duration comparable (smaller but of the same 'heavy weight' category) with the Manhattan project. In the age of glass 'radio tubes' it was extremely difficult. Even if they worked out what the VT fuse did, I doubt that the radio tubes would be that easy to come by and manufacture into rocket fuses. 3-6 moths perhaps?

To explain the level of apparent anxiety in Allied command about the use of VT on the continent - I mentioned ground based guided rockets in daylight - air to air rockets unguided but close range is a better option.

 

[pattle]

The Germans were testing proximity fuses by the end of the war and allegedly they were close to being put into production, that much we know. I don't think this thread requires anyone to be convinced that proxy fuses would have wiped out bombers in such numbers that bombing would have to be abandoned, expecting anyone to be convinced is a little much to ask because it was never put to the test. I think proximity fuses could have caused losses serious enough to suspend the bombing of Germany, when I say could I don't mean would, I just think it possible. I am neither a scientist or a Marshall of the Royal Air Force, my opinion is only based on what little I know through reading for pleasure.

 

[parsifal]

I don't think this thread requires anyone to be convinced that proxy fuses would have wiped out bombers in such numbers that bombing would have to be abandoned, expecting anyone to be convinced is a little much to ask because it was never put to the test

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I need convincing, and so does Professor Westermann who wrote the defeinitive English language version on the German flak arm. There were numerous other problems facing the German flak arm, VT fuses would have helped, but I dont know that they would be a total game changer for the germans.

I do think they would have helped, but I remain unconvinced they would completely turn the battle around. Westermann sort of agrees with that

 

[pattle]

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I need convincing, and so does Professor Westermann who wrote the defeinitive English language version on the German flak arm. There were numerous other problems facing the German flak arm, VT fuses would have helped, but I dont know that they would be a total game changer for the germans.

I do think they would have helped, but I remain unconvinced they would completely turn the battle around. Westermann sort of agrees with that

Well both you and Prof Westermann are perhaps taking this a bit to seriously if you actually need convincing, the war ended 68 years ago so the answer is of no consequence. I am not trying to convince anyone of anything, to me this is only a hypothetical topic for discussion.

 

[bob44]

I believe there is more to it than just having the VT fuse. The German's were effective when the bombers where over a concentrated flak area. The Allies took great steps to avoid the flak areas. If the German flak was even more widespread, precise and/or could not be avoided, no doubt the Allies would target them directly. But would the VT fuse have stopped the bombing, I say no. At least not for long.

 

[bbear]

I hope that now I have the security and general operational story, according to Ralph B. Baldwin "The Deadly Fuze".

The security anxiety was possibly centred around the use of VT for anti-personnel army use and the need to preserve that effect until the right strategic moment
. Numerically the largest fraction of VT production was for army Howitzer use.

Section T (R&D team for VT) developed jamming solutions so they could test whether the technology was vulnerable to jamming by the enemy. They tried jammers for land use and for aircraft. The aircraft version was simple but gave reasonable performance. But the early VT fuses were easily 'prematurely detonated' by a complex 'jammer' at ground level almost as soon as they left the gun muzzles. Fortunately the Automatic Volume Control feature developed to reduce the chance of a 'premature' when firing low across the waves also rendered the anti personnel VT less susceptible to this kind of jamming.

AA VT early types started in production sometime in 1942. Anti-personnel howitzer and rocket VT fuzes were approved for mass production around August/September '43. By roughly april/may 1944 the VT AA fuzes were used over allied home territory against V1s, or at sea (Pacific: mostly against low flying Japanese attack or in the Mediterranean similarly by the nature of the conflict against low/diving attacks). The book gives limited references to the effect on high flying formations as by that time these would be rare. There is an account of one engagement against Japanese 'Spotter' planes in the Pacific.

VT fuzes were only authorised for use on 'liberated' land in any theatre after October 1944. In 1943 a single 'dud' fired from a sea vessel at an enemy a/c but landing onshore in Sicily provoked a shore party operation to recover it.

Section T used two teams to develop jammers neither of which appears to be connected to the Wright Field team. So what the USAAF were concerned about remains something of a mystery - aggressive rockets or aggressive AA or defensive jammers against our own efforts against LW bombers?

That's as far as I can go on security matters and 'overall sub plot'.

 

[bbear]

Nobody convinced me that the proximity fuses would transform Luftwaffe flak into a weapon system capable of devastating allied formations. The Luftwaffe originally thought they needed to get the shell (88mm) within 30m of a bomber to destroy it. This was revised down to 3m. That's the problem. Your projectile needs to pass within 3m of the target to be "devastating" and nothing here has convinced me that this was possible often enough to have a huge effect on allied losses.
Cheers
Steve

Not 3m for a proximity fuse. I take it that the mechanism in that case was the blast damage breaking structural member. Which makes sense for an ordinary shell (because the fragments arriving mseconds after the blasdt wave would be within the 'preblasted' region if the shell exploded at all early (3 meters before the shell reached the airframe) or wouldn't impact at all if the shell burst past the aircraft. In a VT shell the detonation distance from the plane is adjusted by trial and error research to use the fragments and the blast wave together. (Maybe the blast wave to 'pre stress' the metal panels and thus the load bearing members of a plane the fragments arriving milliseconds later taking the combined stress past failure - either blowing away large areas of skin or doing worse damage. At least that's the way I imagine it. )

The distance of detonation may have been 20ft. In any case the area of 'lethal' destruction at minimum with the smallest 3.5" shell was very roughly equivalent to about 25ft radius with the best type 53 fuse and a 5"3/8 shell about 46ft radius, estimated using test ammo against a test plane suspended from pylons - mostly a 'Kate'.

(A VT fuze can give you a detonation disatnce correct to about 2or3 ft as far as I can tell/guess - or be a dud/premature completely)

Just running through the advantages of VT as I understand them:
No fuze setting - increases rate of fire (for the British vs V1s about double) x2 advantage to VT

Crew or autoloader can load VT, then wait and fire (there is no 'race' to predict aim and fire gun before the fuse setting becomes obsolete) shots taken are always at the highest accuracy possible. guess - another x2 advantage?

Depth (time accuracy factor) eliminated : to get a detonation within 3 meters either side at 1200ft per second typical approach speed with a fuze capable at best of 0.1second innate precision (never mind the accuracy of time of flight calculation) is a chance of 1 in 4 in the depth dimension at best. 20 - 25% accurate vs VTs 90% reliability. a x4 advantage

Bigger lethal diameter due to different mode of action about 23 feet radius minimum 46ft maximum: call it 15 m diameter from the surface conservatively : 'hit rate' advantage to VT of about x5?

If that's somewhere in the right region then a VT shell on average would be on the close order of 40 times as lethal as an ordinary shell against B17s and the like. Worth having - but not decisive on its own? (by on the close order of 40 I mean somewhere around 20 to 80). That's consistent with the reported UK result vs V1s of 2500 shots/kill to 100 with VT and still getting better.

Further advantage against low fast targets? - you get one more aimed shot in before the target closes or is obscured ?

 

[stona]

I'm only repeating the Luftwaffe's own opinion. An 88mm shell had to explode within 3m of the bomber to ensure destruction. Whether that was a timed fuse or a proximity fuse doesn't seem to make 5x the difference to the destructive radius in anyway I can see. I'm not an explosive ordnance expert
Cheers
Steve

 

[cherry blossom]

There is a 1946 US report on the effectiveness of Japanese anti-aircraft artillery http://www.fischer-tropsch.org/prim...Reports/USNTMJ-200F-0370-0383 Report O-44.pdf that presents Japanese Army estimates of a "radius of rupture" to compare with the German estimate. The estimate on page 11 was a 7 metre radius for a 88 mm shell. I am not sure what any of these guesses mean because aircraft are not point targets but I suspect were sometimes treated as points to simplify the maths. It is also clear that the fragments from a moving shell will destroy targets in something more like a cone than a sphere.

Note that I am not suggesting that Japanese shells were better than German. In fact, I have heard that German shells were more effective than those of similar weight from other nations because they were cut during manufacture to generate "optimal" sized fragments. I suspect that most nations did static tests which would generate an estimated radius of effectiveness. However, it might be important to check the extent of damage that was estimated to lead to a targets destruction. From a German point of view, a British aircraft that crashed on the way home was as destroyed as one that crashed immediately. However, the anti-aircraft battery would only be credited for the one that was immediately destroyed. Also for a USN ship firing at a kamikaze, damage that would have stopped the aircraft getting home was less significant.

 

[bbear]

To be clear i am no munitions or ballistics expert but i just want to make sure the VT gets its proper balance of advantage it won't change the outcome but it's best to have understanding.

I suspect that both german and japanese figures quoted by both of you are based on the pure explosive 'shock wave' damage. That is exactly because they are expressed as radii from detonation point (pressure shock wave doesn't move forward with speed of shell) whereas just as you say fragment damage would be expected to be a cone - the 1000 or so fragments disperse at around 2200 ft per second in whatever direction - added to the vector of the shell.

The VT developers could actually select the sensitivity of the fuze to set a distance ( i now find that for most shells and fuses they used this turned out to be 70 feet). They found an improvement in what they classified as 'lethal damage area ' of up to 25 or 50 times in area compared with the damage done by contact fuzes (thats ones that actuallly made contact). The VT performed best in 'head on' approach compared with a contact shell.

For a Type 53 fuze on a 5"38 shell in head on mode the 'lethal damage area' is 6800 sqft

(btw figure are from 'the deadly fuze' book - sorry to keep quoting the same reference but the figure is backed up by one or two 'Bureau' and navy sites - but so much so i think that the books table is closest quote to the primary source)

if you are still puzzled and until a ballistics expert appears you might try the high school physics i used to check this. Starting 6 or 7metres call it 20ft short of the middle of the target calculate how far any fragment travelling at 2200 ft per second radially would get before impact (2200 was a figure i got from online source so a low credibility but it 'sounds right'). Result is about 40 or 50ft right? The area goes up by the square of the distance from target. And that is a 100% swept area as far as the aircraft skin is concerned until the pattern of fragments loses cohesion. Because the fragments take some time to acceelerate to 2200 ftpsec the real radius would be much less - as far as i can tell the 'delayed fragment' diameter of effect would be about - 88 to 100mm for a 88mm shell. Thats why 70 ft distance of detonation is much better than 6 meters or 7 metres

or you may want to remember the effect of 'grape shot' (smooth bore cannon stuffed with bent nails, bits of chain, fragments) in the days of wooden ships at very close quarters. Fire when range is too close and the enemy ship gets a small entry hole big exit hole in the side, too far away and her wood work is pockced with bits of nail, but hit the distance exactly right - 6ft hole and internal space smothered in splinters) - that's the effect the sectiion T team were playing for, calculated and tested. Admiral Blandy 1925 is said to have been one of the many voices pointing this out. The problem was to make a proxdimity fuse that worked.

Up to 50 times advantage, i was going easy at claiming only a factor of 5.

That's nominal, test data, at the 'best angle, - other analysis loosely referred to in the book gives an operational total advantage of VT vs other ammunition of 3 at first going up to 6 to 1. But there was so much going on at the same time with predictors and radar ranging that such analyis must have been difficult (i'm guessing again but i have to make an explanation of why i credit one number more than the other). Of course i only have one real reference and that's written by an insider and will no doubt be subject somehow to 'agency bias' in the attribution of praise but - it still makes sense.

 

[bbear]

And thanks cherry blossom for the effectiveness data: I'd like to use it but I can't see the connection between enclosre A where it mentions rupture radius and the fragment impact analysis in the main body - did i miss something?

 

[cherry blossom]

I don't expect a simple relationship as the calculation of a, b and c etc. was from the IJN, who used a 12.7 cm gun, and the enclosure was from the Army who used 7.5 cm, 8.8 cm, 12.0 cm and 15.0 cm guns.

I mentioned the report on Japanese anti-aircraft shells because I knew that it existed. I suspect that there existed much better American, British and probably German data on the effectiveness of anti-aircraft shells exploding at various distances from aircraft.

I found an example of the detail of American analysis using Google at Office of Medical History but this does not immediately answer the question of how damage changes with distance, especially as the analysis necessarily uses only aircraft that survived. However, the effect of the shell's motion is clear from the data comparing fragment strikes on the top and bottom of the wings: "The figures in columns 3 and 6 of table 237 show that the greatest density of hits occurred on the bottom surfaces of B-17 aircraft. The density of hits on vertical surfaces was only slightly less, whereas the density of hits on top surfaces was approximately one-third as great as that on bottom or vertical surfaces."

 

[bbear]

thnaks cherry b, that source is actually the one i got my approx 1000 fragments dispersing at( from that or another source) 2200ftpsec but with the shell speed of 1,100ftpsec from my 'deadly fuze' book.

the hit data is highly suggestive if you want it to be, but my instinct is that it's not fair to take data gathered for one purpose and use it for another. The doc's had a different problem to solve : where would we put more pilot armour on a b-17 or b 24? That's not the same as what burst disstance, if any, makes armour redundant as in -armour for pilot? pilot of what? (my alarm light labelled 'Respect - always, respect.' just lit up).

Raher than risk explaining any further - you are right I need to find a good contemporary analysis source and read it (preferably 3 sources), then a good modern ballistics book, read it and then come back to you. This will take a few months.

 

[gmsw7]

Have a look at the attached nara fms D031 by Gen W von Anthelm re use of contact fuses (as mentioned indirectly in very good flak book by E Westermann)

Mentions/describes a raid in april 1945 he witnessed where "17 of 180-200 bombers attacking airfields around munich" were shot down

I had a quick look through 8th af missions april 1945 but could not see a mission with such losses - but no expert