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

[GregP]

Nice pic Jabberwockey.

Everything inside would have been doable ... and I see the oscillator-detector-amplifier-thyatron bundle looks like tubes. Since there is an oscillator, I am assuming either Continuous Wave (CW) or pulsed CW operation, which would make perfect sense because by the time I came along (in the 1980's), everyone knew that CW fuzes could be jammed and we weren't using CW any more. My bet would be simple CW transmission.

In one of the prox fuzes I worked on, there was a circuit with a variable threshold and if it detected jamming, it would raise the threshold until the jamming was overcome or until the circuit would no long work. If threshold circuit was swamped, the fuze guidance would home in on the jammer! The theory was that if you got the jammer, then later missiles, which were assumed, would not have to contend with it. There might be another one or several other jammers. but this particular one would not be functional.

That type of circuitry was simply not available in WWII, particularly an airborne agile jammer. VT was probably a CW fuze. A radar beam goes out, some signal bounces back, when you reach a preset threshold, function the detomator. Except for the tubes, it looks pretty contemporary! They still have impact-activated batteries and the shells still have about the same outline and available volume for the fuze.

 

[OldSkeptic]

Greg it was doable ... because they did it. Like the anti V1 flak and later artillery.

 

[pattle]

Then short answer is "yes". If you look at the improved performance of proximity fuses when they were introduced against the V1s then you could easily extrapolate to an significant improvement in the effectiveness of German flak. In fact you would expect it to be far greater, in that PFs used against V1s had only a short engagement time (due to low altitude and speed), against slow and high 'heavies' (both night and day) you would expect considerably better performance. Possibly to the point where operations against targets that had them would have had to have been curtailed.

Bomber Command would have been put out of the area bombing business for example.

This is the same as what I was thinking. The only two doubts I have is what people are now saying about the possibility of electronic counter measures being used to stop these shells from exploding next to our planes and my knowledge of electronics goes about as far as being able to wire a plug so I have no opinion on how possible this was. The other thing I can't decide on is whether proximity fuses would have been more deadly against the USAAF bombers flying in close formation or the RAF flying in a bomber stream. My own opinion is that I don't think it would have made much difference how the bombers arrived as with a close formation in daylight all the guns would have been firing at once at lots of planes in a small area which they couldn't miss while at night the guns should have been able to pick the bombers off pretty much one by one as they flew past in the bomber stream. I am not sure just how close RAF and USAAF bomber losses already were to being unsustainable but I feel that German use of proximity fuses could have tipped the balance here.
Just to add one more point if the Germans had of been able to use proximity fuses in the flat open areas of the Steppes then I think the results there may also have tipped the balance.

 

[Civettone]

I wouldn't assume that the proxy fuses were that effective against the V1. There were more factors at play, which make it difficult to assess the fuses seperate from the other factors.

I haven't seen real evidence that the Germans had proxy fuses for use in artillery shells.

Kris

 

[cherry blossom]

The proximity fuses used in WW2 were easy to jam and a jammer could apparently be produced in only two weeks, admittedly by scientists who knew everything about the fuse that they were jamming. As I mentioned, the fuse could even be accidentally jammed by other radars operating in the area. The British design, using the Doppler shift to find the closest approach might have been more resistant. The jamming resistant German electrostatic approach could have led to at least a patent Patent US3871296 - ELECTROSTATIC PROXIMITY FUSE - Google Patents if not a successful fuze. It would be fun trying to find if the American work post-war developed from German ideas but, alas, we have just missed being able to ask Philip Krupen by two years and Laurence Heilprin died in 1993.

 

[pattle]

I wouldn't assume that the proxy fuses were that effective against the V1. There were more factors at play, which make it difficult to assess the fuses seperate from the other factors.

I haven't seen real evidence that the Germans had proxy fuses for use in artillery shells.

Kris

I have read that by the end of the war they were on their way so to speak, but they could have been in use much earlier if Hitler hadn't of stopped their development in 1941. I am only surmising as to how they could or whether they could have changed things. As with most what ifs I think this makes an interesting talking point, but that's about all.

 

[Conslaw]

What kind of fuse did the Germans use for their "tree burst" artillery during the Battle of the Bulge?

 

[nincomp]

What kind of fuse did the Germans use for their "tree burst" artillery during the Battle of the Bulge?

I may be mistaken, but I believe that the "tree bursts" were caused when typical shells with contact fuses hit trees and exploded.

 

[parsifal]

hard to know how effective VT fuses were, because the allies were facing a different problem to the germans

The USN investigation into the effectiveness of their flak was that it was responsible for destroying about 2000 Japanese aircraft. Ive seen and read the study, somewhere, but it would take some finding. However that same study estimates that in1942, the average rounds per kill of HAA was about 2500. By 1944, that number had dropped to to an estimated 500 rounds per kill

For the British throughout the whole of 1940, the claimed AA kills were 400, but in reality it is thought that the number of kills was under 100. That was using basically obsolete guns with virtually no modern gunnery aids.

Throughout 1941-2 the estimated rounds per kill for Genneral Pile's AA command was about 3-5000 heavy rounds per kill. That is almost exactly the same as the Germans, who, according to Westermann were expending around 4000 rounds per kill. This was before the introduction of VT techs. AFAIK, there was not an appreciable increase in efficiency due to the VT techs on conventional a/c. People should however be very careful of this....we dont know if german countermeasures such as Duppel or the tendency of the germans to oerate at night had any effect on Allied AA effectiveness. One would surmise that it was likley to degrade effectiveness, so maybe VT offset these german initiatives.

At that time (1942) the germans had many advantages...a high percentage of radar directed batteries, fully trained, professional crews, a relatively new an unworn artillery park, and aircraft not able to operate above the effective ceiling of their gun park (about 24000 feet). Importantly also, the germans were not hampered by Allied coiuntermeasures However, by 1944 a number of suignificant things had crept in such that the average RPK had risen to about 12000. Most German batteries were now manned by part timers, German radar performance was significantly downgraded (most AA fire was now no longer directed fire, it was mostly barrage type), there was excessive gun wear in the park (which effectivellowered the effective ceiling to 21K or less and also affected accuracy and increased jams) , and many more aircraft were operating above the effective ceiling of the park. In that environment, I dont see the introduction of a single piece of tech as having much impact on German fortunes at all....

 

[OldSkeptic]

Looking around for some examples of PFs effectiveness we get:

V-1 flying bomb - Wikipedia, the free encyclopedia

These electronic aids arrived in quantity from June 1944, just as the guns reached their firing positions on the coast. Seventeen percent of all flying bombs entering the coastal 'gun belt' were destroyed by guns in their first week on the coast. This rose to 60% by 23 August and 74% in the last week of the month, when on one day 82% were shot down. The rate improved from one V-1 destroyed for every 2,500 shells fired initially, to one for every 100.

Other technical fixes were introduced at the same time (such as better calculators and faster swivel mounts) so difficult to pin point exactly the difference PFs made, but obviously considerable.
As for countermeasures, people forget the huge numbers of bombers (both RAF and USAAF), fitting every one with a radar countermeasures would have been difficult in the extreme, assuming it could be done of course.
For the tight groups used by the USAAF this might have been counter productive. Even the later (and tighter) RAF bomber streams would have been at risk.
Opened up the chance to use the bombers' own counter measures against it too. The Germans had become very adapt at detecting them from their emissions.

The Germans started developing their PFs quite early on, then cancelled development, they took the path of doing it electrostatically, not sure how you'd countermeasure that.

As for the Germans using them against the high flying RAF and USAAF bombers, they would have made a heck of a difference. You have to remember that as the war went on they were using poorer and poorer trained people (old men, kids, forced labour, etc). They also were hampered (to the best of knowledge) with poor calculators and insufficient radar guides (they had them, but not nearly enough).

All you'd have to do was get the shells into the bomber group (or stream) and the probability of a hit would have gone up massively. This even more so for the RAF's night bombers, where individual spotting was impossible.

If they had managed to mass produce them for their 88s and 105s (?) then life, as they say, would have got very interesting for the bombers.

 

[cherry blossom]

For comparison, some of you may like to look at the thread Axis History Forum • 1944: Flak Alone Blasts the Allies out of the Sky which I found while looking for information on the German use of contact fuses. The Germans may benefit more than the USN because they were using a less automated fuse setter and thus might be able to increase their rate of fire more. However, they are not shooting at a target approaching them directly, so the problem of getting the shell to the correct place is more difficult. Thus the fuse setting errors may be a smaller proportion of the German problem than the USN's problem

 

[Tante Ju]

As for the Germans using them against the high flying RAF and USAAF bombers, they would have made a heck of a difference. You have to remember that as the war went on they were using poorer and poorer trained people (old men, kids, forced labour, etc). They also were hampered (to the best of knowledge) with poor calculators and insufficient radar guides (they had them, but not nearly enough).

All you'd have to do was get the shells into the bomber group (or stream) and the probability of a hit would have gone up massively. This even more so for the RAF's night bombers, where individual spotting was impossible.

The problem I see is that hampered by inexperienced, part time crews who could not shoot accurately enough. IF you can get the shells into the bomber group, that assumes good accuracy (which is diminished if the target rather out of the effective ceiling of the gun, as any FC errors are magnified) and then normal timed fuses should do. That was actually the major problem, as US bombers flew rather high, quite on the edge for the most common 88s. Now the FC elements could probably calculated rather well, especially for such big formations, but the problem was that the shells took rather long time to get their, which magnified the calculation errors enourmously. Thats why the rarer long 88s, 105s and 128s were so much more effective - they had higher effective range and shorter flight times.

Perhaps a VT fuse would give more consistent results (fuse variations eliminated), but for BOTH fixed-time and variable time fuse has the prequisite is that you need to lob shells close to the target. If you cant get them close, neither will be effective.

The shipborne AAA is bad parallel example, since they had very very different problems to face. Getting a shot near to relatively close range targets on a more or less straight path towards you is easy, but setting the fuse right isn't. VT fuses cured this effectively. This is an exact opoosite of the problems faced by German flak, so I do not think VT fuses would change a lot.

 

[swampyankee]

Would be interesting to see what could withstand the g-force in 1945 .... I have built stuff with that vintage parts and it isn't very durable when you talk about thousands of g's. I'd disbeileve it unless it was mechanical with something a broomstick sticking out of the shell nose ... we did that in Vietnam to get through the jungle canopy.

Without a shematic and the projected parts list, I say BS. Must be somethinhg simple and mechanical or a fabrication. No way tubes can do it. If nothing else, the filaments won't take 5,000 g-s much less more.

US proximity fuzes used radio, and tubes. See http://www.history.navy.mil/faqs/faq96-1.htm#anchor1191195

As an aside, George O Smith, the sf writer was said to have worked on this project. A different sf writer, Arthur C Clarke, worked on GCA.

 

[delcyros]

Delcyros, some say that CIOS report is bogus. I read somewhere that all these CIOS reports are listed, except that one ...


GregP, does a fuse with electrostatic sensor also require a transistor?


Kris

Ok, I have taken time to get through it. Actually I couldn´t find a CIOS item, too, and I have generally good access to these sort of documents. However, I guess it may have been a mistake by someone. The reports do indeed exist but the relevant content for Rheinmetall proximity fuses is filed down under the ALSOS files, not under the CIOS ones.

I quote the relevant reports:

Series II----ALSOS-C:
U.S.Naval technical Mission to Europe Ordenance target No.22 -Report on the proximity fuse development of Rheinmetall-Borsig A.G., June 1945

Series II----ALSOS-E:
U.S.Naval technical Mission to Europe -U.S.Army technical Mission to Europe Fuse reports (files "a" to "f").

 

[cherry blossom]

There is an interesting book, "American Raiders: The Race to Capture the Luftwaffe's Secrets" by Wolfgang W. E. Samuel, available on the internet at ftp://s208.math.msu.su/572000/153b165a481f89e812c6bfee9c12b7be. This seems to relate "Status Report of Exploitation Divison" under a USAAF Brigadier General George C.McDonald. Page 158 has:

For the Great Enzian and other German surface-to-air missile developments to be effective, a proximity fuze was needed. To no one's surprise, one of McDonald's teams reported, "A proximity fuze development for artillery shells has been recovered. It has been ascertained that the fuze operates on electro-static principles and, accordingly, will be a very difficult fuze against which to employ countermeasures. . . .German research had under development no less than fifteen different projects involving proximity fuzes. Although it is evident strict supervision from a central agency should have controlled the related projects, it is now apparent no such control existed and that activities were poorly coordinated. A number of the projects originated in 1930s,were halted in 1940, and revived in 1943 when the danger from air bombardment became more acute. Not a single proximity fuze has seen service, and only two could have been placed in mass production within two years."22

The reference 22 says:

22. Status Report of Exploitation Divison, Tab G, pp. 72-73. To obtain optimum results with their surface-to-air missile developments required a proximity fuze or a homing device. According to Post Hostilities Investigation, German Air Defenses, Volume I, page 4, of the four methods of fuzing examined by the Germans—photoelectrical, electrical, acoustic, and infrared—at the end of the war none of the projects had gone past the development stage and no fuze had been developed that was small enough for a flak projectile and could withstand the shock of being fired from a gun. Proximity fuzing coupled to antiaircraft artillery and SAMs was the most cost-effective approach to defeating Allied air superiority, yet only peripheral resources were brought to bear in this important field, an area in which American science excelled.

 

[OldSkeptic]

On 4 November 1939, Captain Hector Boyes, the Naval Attaché at the British Embassy in Oslo, received an anonymous letter offering him a secret report on the latest German technical developments. To receive the report, he was to arrange for the usual announcement of the BBC World Service's German-language broadcast to be changed to "Hullo, hier ist London". This was done and resulted in the delivery of a parcel a week later, which contained a typewritten document and a type of vacuum tube, a sensor for a proximity fuze for shells or bombs. The typewritten document accompanying it became famous after its existence was revealed in 1947 and would go down in history as the "Oslo Report".[1] Boyes quickly appreciated the Report's potential importance and had a member of the embassy staff make a translation which he forwarded to MI6 in London along with the original. The Oslo Report was received with indifference or even disbelief by British Intelligence, with the notable exception of Dr. R.V. Jones, a young Ph.D. physicist who had recently been put in charge of a new field called "Scientific Intelligence". Jones argued that despite the breadth of information and a few inaccuracies, the technical details were correct and argued that all the electronic systems divulged therein be further explored. In a 1940 report, Jones summarized his thoughts.[2]

Fortunately for us the Germans cancelled it.

 

[delcyros]

I tend not to overemphasize the effect. Remember, the Proximity fuse does not change the problem to get a projectile close to it´s target in the first place- and many do not work at all. It definitely increases efficiency, however.

 

[bbear]

mostly for GregP to comment (quality warning junior at work - it is ii bbear currently 1 sensible comment in 20 attempts - well you did say 'go figure')


thyratron = SN-856-F or close cousin (credit radiomuseum.org ludwell sibley

receiver valve possibly cv122 but in any case linked to US patent US3113235 - RUGGED VACUUM TUBE - Google Patents

original type 32 and 40 patent looks like Patent US3166015 - RADIO FREQUENCY PROXIMITY FUZE - Google Patents

key book : the deadly fuze by Ralph B Baldwin part of the original team (out of print, no I don't have one - going on reputation)

I have no firm source on how the structural/potting component of the design worked but it feels as if that was the biggest secret. Lucite - 'obsidian appearance' might it be rubber toughened? Valves suspended in rubber 'pots' with polymerised Tung oil or similar as a 'wax' as described in the later 1958 patent? The only thing I can think of is some avoidance or treatment of axial and centrifugal forces to avoid 'bending moments' which would shatter a tube n an 'AAA shell in one orthogonal direction or the other. But the valves must remain fixed with respect to each other according the patent....
More figuring to be done...

Talking of airburst in trees - the british WW1 106 fuse later 115 type in wwii seems to be the original 'setback and centrifugal acceleration manager': sprung loaded hammer knocks forward pin releasing copper tape - result an ultra sensitive contact fuse that arms in flight and detonates with the he/shrapnel just above ground, or on barbed wire, tree twig...

And I think it may not be the straight artillery flak that top brass were most worried about when the Germans captured VT fuses during the Bulge (Wright field didn't take two weeks to develop a jammer/predetonator : reading between the lines it was a two week deadline I think).

Germany had some good AA rockets that could reach 30,000 ft from surface IIRC (rocket: low setback acceleration no need for fancy vacuum tubes ) and scary glider bomb controls... 2+2 + VT fuse : = no more large formation flying for sure. A bomber carrying the first wright field solution for ECM could also quickly be- a homing beacon

so my temporary answer to the original question is no it couldn't stop the allies, but it wouldn't have been fun finding out

btw the video footage quoted above in the thread all seems to use clips from a training aid : Film Bulletin 197 from 1945 which shows the unpacking disassemly adjusting and reassembly of a VT rocket - on you tube , fascinating stuff

 

[bbear]

and here are the links

Radiomuseum article for Sylvania SN-856-F prototype thyratron
SN-856-F (SN-856-F)
to save time the links that Mr Sarbell gives for Sylvania general discussion and the best cutaway drawing http://www.radiomuseum.org/forumdata/upload/Sylvania_TechNews_page1.jpg
http://www.radiomuseum.org/forumdata/upload/Sylvania_TechNews_page2.jpg

And an online source from someone who melted off the cerese wax (petroleum product - substitute for original tung oil) potting to reveal the construction
http://www.tubecollector.org/equipment/proximity-fuse.htm

and also gives the reference to british type CV122 or us type 2E27 with 2D29 as a thyratron : tbc

see the construction: tubes are one atop the other in a metal can along the axis and is that a glass fuse I see on the left half hidden

note the support flange is at the top - the electronics unit is suspended from forward in the direction of travel not fixed at the base

the two VT assembled fuzes seem quite different one looks an earlier Lucite type and the other may be post war - i'll need to look

The book 'the deadly fuze' gives hardly any technical detail. It does say the original lucite/plexiglass was replaced by Teflon so that explains the black 'obsidian' appearance of the type 53 and similar later vintage fuses.


The potting latest hunch: is dense, and either malleable (cerese wax) or low strength crackable (tung oil) at ground temperature and under shock undergoes a 'state change' to fluid (cerese wax melting point is 180F) thus managing the
set back (rotation and linear) by movement to average the kick out and absorb energy from then on like a shock absorber damper and
side shock (rotational) - likewise by viscous losses in the fluid and
steady state centrifugal forces - the lighter valve assembly 'floats' to the centre automatically. Note if the 'can' fits fairly tight to the tubes the microphone effects would be common to all tubes held by the can and the fixed relationship of the tubes is assured as required in one of the patents-

that may be the sought after 'mechanical assembly' that is referred to but not described in the navy history or other material referenced so far : all surmise of course - just as a clue



and the book gives a few more details on the germans : they did pick up a 'dud' and worked out it was electronic but not what it did. patton called it 'the funny fuse' germans at Bastogne called it 'bauschboom' - puffbang I think. British AA army called it BONZO. Land army 'Air-burst' possibly. US Army mostly called it VT or 'Pozit'

Guided Wasserfall AA rockets might have been the biggest threat - never quite completed but....

I'll edit in the other links later

 

[Reegor]

I tend not to overemphasize the effect. Remember, the Proximity fuse does not change the problem to get a projectile close to it´s target in the first place- and many do not work at all. It definitely increases efficiency, however.

I must be missing something. It seems to me that a proximity fuse would at least double the kill rate. To be effective, AAA needed to explode a shell inside one of the boxes each containing about 20 aircraft. (This is for combat formations of 8th Air Force bombers.) The problem of firing on a trajectory that intersected a box is not changed. But setting the fuse timing correctly is solved by the Proximity fuse.

Pkill = P(trajectory that intersects a bomber box)
x P(shell explodes at same altitude as bomber box, if it passed through the box)
x P(causes major damage to an aircraft)

The first probability is unchanged. The second probability goes from ? to .99. I can't believe that probability of correct time fusing was more than 50%, and perhaps a lot less.
The third probability increases moderately, since the proximity fuse is designed to explode at the moment of closest approach.

All together, the effectiveness of German AAA would at least double, and perhaps triple or better. Doubling would be 31% higher overall losses, according to the paragraph below. In 1945, this would not have mattered. But in 1944 it would have been serious, although probably not enough to halt the American attacks. Indirect effects of flak were to reduce bombing accuracy. Since Allied heavy bombing accuracy was so poor to start with, I don't think that proximity fuses would have had much impact on the results of bombing.

In comparison to their British counterparts, flak defenses accounted for over half of the USAAF's combat
losses during the war in Europe, downing almost 5,400 aircraft compared with the 4,300 aircraft shot
down by Luftwaffe fighters.3
The Eighth Air Force lost a total of 1,798 aircraft to flak during the war.4
This number represents approximately 31 percent of Eighth Air Force bomber losses during the war due to
all causes, including weather, accidents, mechanical malfunctions, and fighter attacks.5
In comparison
with the Eighth Air Force, estimates by the Mediterranean Allied Air Forces (MAAF) concerning the
proportion of aircraft lost to flak are significantly higher for this theater. In terms of all types of aircraft
(fighters, medium bombers, and heavy bombers), the MAAF lost 2,076 aircraft to flak compared with 807
brought down by enemy aircraft in the period between January 1944 and February 1945, a ratio of 2.6 to 1
in favor of the flak.6
Specifically, the Fifteenth Air Force lost 1,046 heavy bombers to flak between its
activation in November 1943 and its final bombing mission in May 1945. The heavy bombers lost to flak
represented 44 percent of all Fifteenth Air Force heavy bomber losses.7
Approximately 10 percent of these
losses occurred during attacks on the oil facilities in the vicinity of Ploesti, the "graveyard of bombers," the vast majority as a result of flak.8 In addition to the strategic air forces' loss of heavy bombers,
Luftwaffe flak defenses claimed a total of 2,415 aircraft from the Ninth Air Force and the Twelfth Air
F

Source: Flak: German Anti-aircraft Defenses 1914-1945
Edward B. Westermann
University Press of Kansas