AHC: Peerless Air Ministry

Deploying proximity fuses means running a risk of them being captured. That was one big allied fear that stoped their deployment in the ETO.
AIUI (and IIRC correctly from a previous discussion on another board) the Allies were VERY paranoid about VT shells
to the point that initially they were only deployed where there was little chance they might be found and copied

In the ETO an early large scale use of AA VT was vs the V1
but it took an appeal by Eisenhower to release the stocks for use during the crisis stage of the Bulge
- not as AA but for Antipersonnel barrages

(Supposedly, Patton loved VT ... saying something like "this is going to change the face of land war" )
 
thanks for that information, any links available? they would be much appreciated.
YAVW

Most of the above is dredged out of my mental archive from a previous discussion on this subject.
(I am was an engineer of sorts so such technical detail tend to stick even when I forget where I put down my reading glasses 🙄 )

I'll see if I can find either that chat or the sources that were used.

Added Later after a bit of google fu:

Try this ... https://smecc.org/radio_proximity_fuzes.htm however TOTALLY "USA! USA!"

even wiki is useful https://en.wikipedia.org/wiki/Proximity_fuze
 
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perfectgeneral

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The valve museum: http://www.r-type.org/index.htm
J Owen Harries was quite the expert. Worked at Hivac Co. Ltd.
Put EMI engineers Cabot Bull and Sidney Rodda on the team.

Starting point is probably the hard to make inch and a bit across acorn pentode: http://www.r-type.org/exhib/aaa0109.htm
The acorn envelope is 14 mm in diameter and, including the base pins, is 45 mm tall.
References: Datasheet. Type 956 was first introduced in 1936.

Or hearing aid valves. Acceleration acts on mass.
You want strong and small with well spaced and insulated contacts.
I'd expect contacts to radiate out like on the acorn to cope with very high frequencies.

Plates should all be vertical. Preferably oriented radiating from the centre to cope with spin, but it still needs to have a heater and collectors that work!
170px-Pentoda_symbol.svg.png

My "VT Acorn" should appear at size on a 1080 laptop

The anode cools off by radiant heat. So large surface area.
Found it. http://www.r-type.org/addtext/add032.htm
VTtube.jpg

Sub-miniature valves roughly 7 x 9 x 30 mm

Valve (or tubes as the USA have it) are heat sealed in glass in a vacuum. The need for temperature regulation is about zero. You might have issue with wax used to improve capacitance. So use resin, but only when you are sure it is finished. Cardboard or particle board circuit mounting would need to be resin and spun glass mat composite. Glass fibre >>fibreglass circuit boards. A solid plate of copper is bonded onto the surface and then etched back into separate conductive tracks with acid (oxalic?) Holes drilled at contact pads allow insertion of component "legs" for soldering into the circuit.

I used to do a lot of that in my summer holidays as a kid.
Given the acorn valve prototype starting point I think Harries would have a VT fuse awaiting the right battery before you get the Canadian battery. He needs a 3.7inch AA gun test rig on a quiet airfield somewhere he can fire into water to recover development prototypes. Hivac go into mass automated production six months later? Companies that can't make acorns won't be able to make these. Glass base. High vacuum. Reliable methods of alignment of pentode parts at speed in a vacuum introducing hot glass and pinch sealing. Put the whole machine in a vacuum rather than just the "work area" of the components.
 
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perfectgeneral

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Since ARL make Araldite (synthetic epoxy resin) and have already used it to bond clutch plates for tanks and to make the Mosquito, there is a lot of demand, but only local supply. I don't think the USA has anything as good for isolating contacts, components and full circuits. This stuff is like water proof and low conductivity steel, but conducts heat better than air. it is the outer layer that solve a lot of problems. Like explosive acceleration.
 
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Thanks Guys, please keep feeding the boiler!
As you wish

(though I suspect you may come to regret it)

I have not yet found a viable POD to butterfly an earlier proximity fuse. If someone has information as to how the VT fuse could have been produced earlier, i'm all ears!!
I think the key to your dilemma is that you have actually asked two separate questions and have been looking for only one answer.

To clarify, IMHO the PAM should first be looking for a way to create any effective anti-aircraft weapon with a proximity fuse (whatever the weapon format)
and only secondarily finding a way to use proximity fuses in shells fired from the most common conventional heavy/medium AA guns.

(For the time being the fact that proximity fuses are useful in land warfare can be ignored,. It the Perfect Air Ministry after all )

Looked at from that angle it's not such a great step to imagine that iTTL the UP rocket systems to be fitted with the Thyratron based radar fuses
(rather than the snagging wire systems used iOTL that proved such a failure.)
Later Edit: just found that the initial intention for the 3" variant was not the wires but an experimental optical proximity fuze!

You would probably have to accelerate the development of both launchers and radar fuse a bit, but that is not too large a jump
(especially as Lindemann has less impact iTTL)
Aside: it may be better to limit the variants of the rocket to only 7" and 3" variants (Y and Z batteries?)
Not so unlikely given the new fuze.

The low acceleration and lack of spin from the rockets mean that the technology is producible in Britain
and given the low volumes needed for these applications, the Americans need not be involved in 1940
(which matches well with TTL Tizard Mission parameters)

In truth, I doubt that enough UP batteries would available to make much difference in the BoB
but they very well might make the later stages of the Blitz harder for the Luftwaffe

Fortunately, being used only as supplementary AA at Sea, in Britain (and maybe few bases like Malta) security is less of an issue.

The PAM would not forget the second stage and so development, including the cooperation in Canada, would still go on during the Winter of 40/41.
The new valve and battery give the British all the design elements of a gun-fired proximity shell ... but probably insufficient production capacity.
The British can build and test a few batches in spring 41.
At that point, the British could approach the Americans with a proven design that is "patented" (rather than a "possible" concept that can be "improved").

The result would be a production contract in August 41 on favourable terms in return for allowing the US to build the same mechanism in their calibres.
This would avoid most of the nearly years delay while the US reverse-engineered the British design and repeated their tests.

Hey presto, the RN get 4.5" & the Army 3.7" VT in early 42 and the USN 5" VT in Mid 42.
From that point, the technical track is as OTL with US firms making changes to ease production
and US scientists leading the way in miniaturisation so that the Bofors 40mm can have VT too, perhaps even a little earlier than OTL.

1582575238629.png


OTL multiple 3" version in 1941
 
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Wow that is a really good synopsis, now I just have to compose and write a plausible story lie. Thanks for the idea.
Again YAVW. However, in return I do ask one favour.

Please can you also find a way to avoid the Bethnal GreenTube station Tragedy.
Basically a crowd entering the station as an air raid shelter panicked when a newly located Z battery fired,
someone slipped on the stairs and many were killed in the resulting crush.

A few years back, my youngest girl lived within walking distance of that Underground Station.
The hairs on the back of my neck always rose when climbing down those same steps.

There always was a simple plaque

1582580349694.png


but now there is a larger memorial in the nearby park

1582580325860.png


History all around us
 
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perfectgeneral

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In truth, I doubt that enough UP batteries would available to make much difference in the BoB
but they very well might make the later stages of the Blitz harder for the Luftwaffe

Fortunately, being used only as supplementary AA at Sea, in Britain (and maybe few bases like Malta) security is less of an issue.
How about 3"VTUP batteries at airfields? In the early part of the BoB, before the Blitz got started in response to the Berlin raid, The Luftwaffe were targeting airfields a lot. Pretty effectively too. It was thought that the RAF would lose if that continued. Not so accurate with the area of sky attacked, the VTUP would be much more accurate on getting the detonation timing (height) right. An area effect weapon would work on a bomber formation though. Less effective against individual dive-bombers. The fighters/interceptors will have to address that issue.

RN use might offer some hope in the steep sided Fjords of Norway. Malta took a lot of bombing. So more effective UP there would make a big difference to the readiness to the airbases and the consequent number of convoy interdictions of Italian convoys attempting to back the Axis African forces.
 
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ITTL if you excuse the pun the PAM has put a rocket up the Armies arse and have been developing their own rockets. Up does not exist (in it's the wire launching guise) but work is proceeding on unguided AA rockets and their proximity fuses. I will do an update on that subject when I finally finish with the BoB (only been write that for a year so far!!!)
Order Of Battle and moving high rank officers around is occupying my research at the moment.
 
How about 3"VTUP batteries at airfields? In the early part of the BoB, before the Blitz got started in response to the Berlin raid, The Luftwaffe were targeting airfields a lot. Pretty effectively too. It was thought that the RAF would lose if that continued. Not so accurate with the area of sky attacked, the VTUP would be much more accurate on getting the detonation timing (height) right. An area effect weapon would work on a bomber formation though. Less effective against individual dive-bombers. The fighters/interceptors will have to address that issue.

RN use might offer some hope in the steep sided Fjords of Norway. Malta took a lot of bombing. So more effective UP there would make a big difference to the readiness to the airbases and the consequent number of convoy interdictions of Italian convoys attempting to back the Axis African forces.
Agreed that the early models of AA rocket with a prox fuse would be best used as point defence against low-level attacks.
(iOTL they were envisaged as supplements to the 2lb pompom/40 mm Bofors)
With an effective Prox fuse, even Dive Bombers may be vulnerable?

In the UK either Airfields or Radar Stations make sense, especially IF they can be made available in time for the BoB. (Thats down to our gentle author)
Malta in late 40/41 looks a no brainer ... a lot of overwater positions, easy to transport, easy to operate (iOTL 3" Z batteries were given to the Home Guard)
Singapore, Columbo Rangoon etc all seems possible in 42 if supplies are sufficient).

However I haven't been able to determine the effective horizontal and vertical range of either the 7" or 3" variants so not sure about higher formations.
iOTL the larger 7" version was limited by the need to deploy the "minefield". It should do better in pure free flight.
The 3" version (aka Z battery) was certainly in use vs night bombers as late as 1943 (see the Bethnal Green Tragedy)
Unfortunately the optical prox fuze never really worked. I suppose they might have been deployed more for a morale effect that military efficiency.
A working radar fuze might well change that.

In any case, whether 7" or 3" these are NOT seeking weapons, so they would need to be aimed to some degree ... which is another problem for the PAM
iOTL the great British Bodge was applied.

1582626581968.png


Home Guard in 41 loading a single tube launcher.

1582626845680.png


20 tube 7" system on a BB (? early 1941)

Aside: some sources claim that iOTL a limited number of 7" systems built for the RN were used by the RAF for airfield defence in the BoB.
I'll try to chase that down.
 
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Alan I'm confused how is a non salvo fired unguided rocket meant to hit... Anything?

I can understand 20 of the things fired into the middle of a formation a number of times in short order from a battery would at least break it up. But one at a time? What as the doctrine there?
 
Alan I'm confused how is a non salvo fired unguided rocket meant to hit... Anything?

I can understand 20 of the things fired into the middle of a formation a number of times in short order from a battery would at least break it up. But one at a time? What as the doctrine there?
You are quite correct to be sceptical about a DIRECT hit. So were the British in 1940.

iOTL the British developed and deployed 2 completely separate systems using solid fuelled rockets in 1939/40 to supplement close range AA.
Each was designed to work without a direct hit (though neither were a practical success)

The 7" system (code-named Unrotated Projectile) used a 35lb rocket that broke apart to deploy a "parachute mine" linked by wires.
The idea was that an aircraft would hit a wire and draw the killer explosives (~0.5 lb) onto themselves.
Added later: the actual propellant rocket was 3", the wider size was on;y needed for the "mine system".
Typically 10 rockets were fired in a ripple and the resulting "fence" would only fall slowly so theoretically a salvo need not be very accurate.

The usual mount was an unarmoured 20 tube launcher ... which meant quite a lot of explosive was on deck.
It was deleted from Warships in 41 but remained on some Merchantmen.
The Navy later adopted free-flight rockets for shore bombardment (LST LCT Rocket)

This variant was initially sponsored by the Navy but may have been used by RAF airfield defence as early as August 1940.

The 3" system (code-named Z Battery) was a free flight rocket fitted with a proximity fuze .. so that also need not have a direct hit
Unfortunately, the rocket itself did not fly perfectly and the electro-optical fuse design was poor.
The initial design was a single tube but quickly replaced by a double launcher.
The number of tubes was increased eventually reaching 20+ per mount and 100+ in batteries, all ripple firing

This variant was sponsored by the Army and used from "bodged" launchers but later adapted to obsolete gun mountings.
Aside: this variant was used in North Africa as adhoc artillery in '42, leading to the design of "land mattress" bombardment variant used in the ETO 1944/ 45.

Z batteries were kept in service until at least 1943 (manned by Home Guard) but were replaced in army service as Bofors and 3,7" became available.

Aside: both systems were sponsored by Lindemann (aka Lord Cherwell), scientific adviser to WS Churchill first as 1st Lord at the Admiralty & then PM

As I said neither system was judged a success as AA iOTL
the question we are discussing is whether either (or both) could have been better with a RADAR proximity fuse in time for the BoB (and Malta and Singapore ... )

iOTL the 7" version was modified to carry test prototypes of the British Thyratron radar fuse and successfully fired against targets fixed to balloons in June 1940
so this may be possible with a push from the Perfect Air Ministry

(Note this is a full 10 months before the US tested their unlicensed copies of the British design in bombs dropped to the ground
with a further year before gun shells were possible)
 
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Order Of Battle and moving high rank officers around is occupying my research at the moment.
I am a bit concerned with Dowding being moved higher. He was supposed to retire pre-war (and thank god he wasn't). However, he was well overage and AIUI he was very very tired after the BoB. hence the relevant authorities did not object when he wanted to stand down. He was supposed to retire in 1939 and was approached to stay on until March 1940 and then events caught up with him and he stayed throughout the BoB. After a number of possibly political postings including one to the USA, he finally retired in 1942.
I have seen a number of TLs where he has been used to push the OP agenda such as being the Inspector General looking at Malta etc.. I wonder of this is simply a way of using a well known and latterly respected figure to make a point???
 
In The PAM, Lindemann is long dead and the airborne parachute mine totally discredited and abandoned. The wire and mine UP system was also abandoned at the same time. the 3" AA rocket is being pursued but is ineffective in October 1940 due to lack of fuse. However the 3" rocket is being developed for air to ground use with Trials actually under way.
How long Dowding stays as Cas is currently a matter of speculation in the PAM. He is seen as a safe pair of hands with the ability to see the usefulness of ne technologies and to push them through.
 

Coulsdon Eagle

Monthly Donor
In The PAM, Lindemann is long dead and the airborne parachute mine totally discredited and abandoned. The wire and mine UP system was also abandoned at the same time. the 3" AA rocket is being pursued but is ineffective in October 1940 due to lack of fuse. However the 3" rocket is being developed for air to ground use with Trials actually under way.
How long Dowding stays as Cas is currently a matter of speculation in the PAM. He is seen as a safe pair of hands with the ability to see the usefulness of ne technologies and to push them through.
There was a school of thought that the UP system aboard Hood might have contributed to her loss - pretty much debunked following the discovery & investigation of the wreck site - as it may have been set ablaze by the first 8" hit by Prinz Eugen. If that were true then this may have been butterflied away.
 
In The PAM, Lindemann is long dead and the airborne parachute mine totally discredited and abandoned. The wire and mine UP system was also abandoned at the same time. the 3" AA rocket is being pursued but is ineffective in October 1940 due to lack of fuse. However the 3" rocket is being developed for air to ground use with Trials actually under way.
That's all to the good.

Essentially iTTL the British are only creating a 3" AA rocket and not deploying until a practical proximity fuse is available
By July 40, the radar principle is already proved in a rocket so only Production is needed.. say first models late 1940, second-gen spring 41.
Since this will be both an Army and Navy weapon I expect the launcher to be close to the OTL Mk 4 Z battery
i.e. with 20+ rails and fitted onto a trailer or an obsolete gun mount especially on a ship.

There was a school of thought that the UP system aboard Hood might have contributed to her loss - pretty much debunked following the discovery & investigation of the wreck site - as it may have been set ablaze by the first 8" hit by Prinz Eugen. If that were true then this may have been butterflied away.
If the above comes true, then I expect HMS Hood would still have its battery of AA rockets (at least 5 x 20 rails)
but iTTL they would be smaller, lighter and less explosive installations.

Aside: Since a reload is quicker and easier for a 3" than the OTL 7", the ready rockets may even be struck below when the AA threat is low but a surface action imminent.
 
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