How would the Oerlikon GDF...

[DerGiLLster]

...fare as anti-aircraft artillery in the Second World War? Would it prove to be superior to the 40mm Bofors of that time period?

I am aware that it is powered by fire control radar and not by human gunners. So just use whatever fire control radar they had in the Second World War. Even late war fire control radars if you wish.

 

[swampyankee]

Well, higher muzzle velocity and greater rate of fire would be pluses. Of course, after you ran out of shells, it would be a tad useless. Also, the fire control systems of the time couldn't deal with the fuze setting or velocity measurement systems that are included in may applications of the 35 mm.

 

[DerGiLLster]

Well, higher muzzle velocity and greater rate of fire would be pluses. Of course, after you ran out of shells, it would be a tad useless. Also, the fire control systems of the time couldn't deal with the fuze setting or velocity measurement systems that are included in may applications of the 35 mm.

So it would be better to make it human operated then? Probably would be better to make it fire roughly 400 rounds and not 550. That number seems to high for me. Could better converse ammo.

When did fire control systems know to deal with fuze settings and velocity measurement?

 

[swampyankee]

So it would be better to make it human operated then? Probably would be better to make it fire roughly 400 rounds and not 550. That number seems to high for me. Could better converse ammo.

When did fire control systems know to deal with fuze settings and velocity measurement?

Well, the USN 5"/38's FCS could set fuzes before ww2, but it couldn't set them as the shell was leaving the muzzle, which is what the 35 mm Oerlikon and the 40 mm and 57 mm Bofors do. A lot of these guns also measure the muzzle velocity of each round. I don't think this capability either capability could be put into a gun in service before the early 1990s.

 

[TheMadPenguin]

The VT fuse could be made in WWII small enough to fit in a 75mm shell (and leave half the shell volume for the bursting charge). THAT would trump the 20 and 40mm.
Before the VT fuse, but with radar gun control, 40 vs 20 was an uncertain question.

 

[DerGiLLster]

Snip

Why isn't it enough for the auto cannons fire control to anticipate where to shoot the plane? Like find that it gets in range and shoot at it? Kinda like a early version of the Phalanx CIWS.

Was the technology in world War two there to allow CIWS weapon systems on ships or no?

 

[Glider]

Any modern automatic AA gun is going to have significant advantages over a WW2 weapon. Rate of fire, better fuses, better control systems. Using ww2 technology would still leave a better ROF. The 40mm Bofors went from 120rpm to I think 300rpm and they did that for a reason, they had to with the greater threat as aircraft performance increased.

 

[TheMadPenguin]

Why isn't it enough for the auto cannons fire control to anticipate where to shoot the plane? Like find that it gets in range and shoot at it? Kinda like a early version of the Phalanx CIWS.

Was the technology in world War two there to allow CIWS weapon systems on ships or no?

Pointing at the incoming plane under radar fire control is easy. It's also not likely to hit unless the plane is heading straight at you or is very close. Combining radar fire control and lead-computing (developed late war for fighter gun aiming/firing), however, could do the job.

 

[Shortround6]

Radar just gets you range and bearing to the target.
Repeated range and bearing data points allow you to figure out course and speed.
How fast your "computer" (micro chips or hand wheels and dials) can give you a solution and how fast that solution can be transmitted to the guns and either the gunners apply the solution to their hand wheels or joysticks or the "computer" directs the electric motors on the mount really govern how accurate the AA fire is against fast moving close targets.

Computing gun sights could figure rough course and speed from the angular change per unit of time and at close the range the time of flight was a matter of a few seconds. But they did not solve the full equation. They also did not set time fuses.

Germans did try mounting four 30mm MK 103 guns on an AA mount.

But it was too light and the vibrations/firing shock threw the aim off.
at just under 400rpm per barrel the concept was certainly there.

 

[tomo pauk]

...fare as anti-aircraft artillery in the Second World War? Would it prove to be superior to the 40mm Bofors of that time period?
I am aware that it is powered by fire control radar and not by human gunners. So just use whatever fire control radar they had in the Second World War. Even late war fire control radars if you wish.

Pictured is the Cold-war vintage model, the GDF.
It would've been certainly superior to the ww2-vintage 40mm Bofors - yes, the shell weight is 550g vs. 900g, but the RoF is several times higher (550 rd/min per barrel), and MV is 20% greater. Ground mounts are usually twin for the 35mm GDF, the 40mm Bofors not that much.
The device on the muzzle is the muzzle-velocity measuring device, the fuse setter was added with advent of the AHEAD type of ammo in the 1990s.

 

[Koopernic]

...fare as anti-aircraft artillery in the Second World War? Would it prove to be superior to the 40mm Bofors of that time period?


View attachment 574630

I am aware that it is powered by fire control radar and not by human gunners. So just use whatever fire control radar they had in the Second World War. Even late war fire control radars if you wish.

Range of round at 45 degrees from NavWeaps Naval Guns of the United States of America - NavWeaps

40mm POM POM HV shells 5,000 yards (4,572 m)1,700 yards (1,550 m) rate of fire was about 90-100 RPM

BOFORS 40mm 11,133 yards (10,180 m) US guns rate of fire was about 120-140 round per minute
BOFORS 40mm 10,750 yards (9,830 m) UK guns rate of fire was about 120-140 round per minute

German Navy 3.7 cm/83 SK C/30 9,300 yards (8,500 m) rate of fire about 30 rounds per minute, semi automatic (spent case ejected and drew in the manually loaded shell)

German Navy 3.7 cm/57 (1.5") Flak M43 7,100 yards (6,500 m) 250 rounds per minute cyclic (this was an adaption of the FLAK 43)

US NAVY 1.1"/75 (28 mm) Mark 1 and 2 40.9 degrees 7,400 yards (6,767 m) Cyclic: 150 rounds per minute

JAPAN NAVY 25 mm/60 (1") Type 96 Model 1, 7,439 yards (6,800 m)
(based on French Hotchkiss)

German Navy 2 cm/65 (0.79") C/38 AA MG 5,360 yards (4,900 m) rate of fire 480 round per minute cyclic


Oerlikon 20 mm/70 4,800 yards (4,389 m) rate of fire 450 round per minute cyclic
Oerlikon was used by both sides though by axis in small numbers.

I was a little to lazy to put in the muzzle velocity but its mostly around 800-900 m/s except the POM POM which is under 700

The modern Bofors Trinity has a muzzle velocity of 1025 to 1100 m/s and 13,670 yards (12,500 m) range. The Oerlikon 35 mm Oerlikon GDF-003 has a velocity of 1150 so the range should be about the same. ROF is nearly 300 for both Bofors and 500 for Oerlikon.

The 40mm bofors was extremely succesfull. USN reckoned 20% of kamikaze attacks were destroyed b 5", 40% by the Bofors and 40% by the 20mm.

It was important to have good predictors and guns sighs eg lead computing gyro sites.

Both the US (SCR 584) and Germans (FuMG 64 Mannheim) developed tack lock radars. Both had computing mechanisms to calculate the aim point, firing time and fuse setting.

These were being miniaturised. SCR-584 had a 6ft 1.8m attena and FuMG 3m.

The Germans adapted an prototype 3cm night fighter radar for the Navy and mounted it to a highly modified quad 2cm FLAK and had a version called "ballspiel" for type XXI U-boats.
The Russians captured some and we have the Russian reports on them now. They didn't enter service but got to prototype testing,
UK and US navy was developing such things as well for the boffors.

Germans were going for a 5.5cm gun called 'Geraet 58' concept latter developed by Russian as SU-57mm. It had a very high muzzle velocity of 1100m/s, ROF 140 RPM and was designed to kill a 4 engine bomber with 1 hit. This was computer controlled and designed for 'hit to kill' tech rather than airburst. Germans had electronic cold cathode tube electronic timers which they were planning to create a programable air burst with the shell programmed in the breech of the gun.

Modern guns measure the muzzle velocity at the muzzle and some even program the airburst there. Many track the round and correct for aim.

 

[Shortround6]

Was the technology in world War two there to allow CIWS weapon systems on ships or no?

No, at least in the modern sense. It took dozens of individual 20mm cannon for instance to form a CIWS system on a WW II ship. When the Kamikazes showed up the black humor was that when the 20mm guns opened fire it was time to hit the deck (prepare for impact) for the other sailors.


The ability to predict the future flight path of an airplane or Kamikaze with a high degree of accuracy did not exist.

The 40mm Bofors in the US Navy often used the MK 51 director in the lower left part of the picture.
The MK 51 weighed 710lbs above deck.
The MK 52 was a modified MK 51 carrying Mk 26 range-only radar. However this boosted the weight to 1710lbs above deck and 1320lbs below deck, WW II electronics was neither compact or light.
These directors were used post war for the 3in AA guns.
Operating limits for the Mk 52 according to one source was lead angle 20 degrees, target speed 350kts, range for surface fire 12,000yds, for AA fire 7,000 yrds (this limits sound like they are for the 3in gun.)
The MK 63 was a MK 51 with tracking radar mounted on the gun mount.

Weights went between 3900lbs and 5400lbs.
Detection range is given as 37,000yds.
Tracking range is given as 35,000yds.
Computing range is given as 7,000yds.
The above decks director pedestal weighed 1300lbs.

 

[TheMadPenguin]

A short round person said:
"When the Kamikazes showed up the black humor was that when the 20mm guns opened fire it was time to hit the deck (prepare for impact) for the other sailors."

ASSUMING the incoming plane is doing about 200MPH, that's about 300 feet/second. Effective 20mm range being around 3000 feet, you have about 10 seconds to kill the plane before it hits you. So, yeah, when the 20's open up it's time to hit the deck. 20mm was labelled "a weapon of vengeance" meaning (formerly) the plane attacks us (and hits with a bomb) and we shoot it and it doesn't ever return (splash or excessive damage). Kamikaze attacks render this interdiction moot; from their point of view you have a 100% chance of killing the plane with your hull and deck... So over time the 20's went the way of the .50 cals, becoming 40's, which in turn went away becoming 75mm.

Problem: A gun big enough to kill the incoming plane far enough away to prevent damage to the ship is heavy enough that it can't traverse and elevate fast enough to engage jet fighter-bombers. Thus the missile-only and missile-mainly destroyers and cruisers of the 60's-80's. ALCMs brought back the 20mm as a CIWS. Now they're also programmed for swarms of speed boats and drones that are worth 100 rounds of 20mm but not a RIM-116 at near $1Mil/shot.

*sigh*

Next Episode: Lasers & railguns & NEMP! Oh, my!

 

[Koopernic]

No, at least in the modern sense. It took dozens of individual 20mm cannon for instance to form a CIWS system on a WW II ship. When the Kamikazes showed up the black humor was that when the 20mm guns opened fire it was time to hit the deck (prepare for impact) for the other sailors.


The ability to predict the future flight path of an airplane or Kamikaze with a high degree of accuracy did not exist.

View attachment 574902
The 40mm Bofors in the US Navy often used the MK 51 director in the lower left part of the picture.
The MK 51 weighed 710lbs above deck.
The MK 52 was a modified MK 51 carrying Mk 26 range-only radar. However this boosted the weight to 1710lbs above deck and 1320lbs below deck, WW II electronics was neither compact or light.
These directors were used post war for the 3in AA guns.
Operating limits for the Mk 52 according to one source was lead angle 20 degrees, target speed 350kts, range for surface fire 12,000yds, for AA fire 7,000 yrds (this limits sound like they are for the 3in gun.)
The MK 63 was a MK 51 with tracking radar mounted on the gun mount.
View attachment 574903
Weights went between 3900lbs and 5400lbs.
Detection range is given as 37,000yds.
Tracking range is given as 35,000yds.
Computing range is given as 7,000yds.
The above decks director pedestal weighed 1300lbs.

There is a history here: History and Technology - The Mark 51 FCS - NavWeaps
The Mk 34 radar was added to the Mk 51 FCS very late in the war. Id say to late to use in Europe but of use in the war in the final stages of the Pacific war. For the most part the aimer tracked the target with an initial estimate range. This FCS would add super elevation and lead and then servos would point the guns would get the shells falling close to the target. The aimer then corrected by tracking the tracer. I don't think the range was continuously adjusted. The Beauty of the Boffors was that firing could commence as early as 4000 yards and it therefore could intimidate an target well before it got to bomb or torpedo release range. Gyro sights allowed US Oerlikon gunners to be accurate a 2000 yards and they were instructed to open up at 2200 yards. That's nice but just about at Torpedo release range (about 1 mile)

The British did use 50cm Type 282 radar on the The Pom-Pom director Mark IV from 1940. The radar could find a target and provide range but was not capable of tracking it for blind fire. This system was the most advanced for its day and included man in loop servo gun pointing though it lacked gyro stabilisation. The British ships had plenty of radars with multiple separate units for the POM POM, 4.5, 4.7, 5.25 inch guns and Main guns. The problem with this impressive system was the short range of the POM POM. They switched to the Boffors wherever they could.

The Germans did have the Seetakt radar mounted on the main directors. The latter versions had a type of lobe switching on receive and could provide blind fire for bearing though not elevation to the 10.5cm guns, in theory they could send this data to the 3.7cm guns by adding appropriate computers and dial indicators, don't know if they did this. There is tantalising information that the Germans added height finding ability using phasing similar to the type they used on their Wassermann (Aquarius) early warning radars.

The 2.0cm quad FLAK C38 was an effective weapon with gyro sights and a full crew to keep the 20 round clips fed (continius fire could be maintained by firing 2 of the 4 guns at the time.) but obviously it was lavish in crewing requirements.

 

[DerGiLLster]

No, at least in the modern sense. It took dozens of individual 20mm cannon for instance to form a CIWS system on a WW II ship. When the Kamikazes showed up the black humor was that when the 20mm guns opened fire it was time to hit the deck (prepare for impact) for the other sailors.

What if they had 20mm miniguns?

You could fit those and ammo large enough for a minute of firing on a ships, maybe a few destroyers. Faster rate of fire would help.

Could be primed to fire 5 seconds when you press the trigger and then you can move the gun for the rest 3-4 seconds. I bet that would have aiming much easier, so all they can do is move the gun, while the rounds fire off for a few seconds. Helps having a higher rate of fire.

 

[Shortround6]

I am not sure where this fascination with modern guns in WW II comes from. You do have to feed the things.

A small portion of the 20mm guns on an aircraft carrier.
the whole point of the 20mm guns was to add firepower without needing support from the ship in the way of electricity or hydraulic power. The guns shown would fire for about 8 seconds with the drums shown.
A ship mounted gatling gun has the same problem as an aircraft gatling, trying to feed 70-100 shells per second.

BTW there is no such thing as a "20mm minigun", you either have a 20mm Vulcan gun or a 7.62mm minigun. So called because it was a miniature 20mm Vulcan.

When additional firepower was wanted but room was scarce they resorted to twins.

900 rpm not counting drum changes. No electric cables for power or director control. Fairly simple maintenance.

 

[Koopernic]

Radar enhanced 2cm Flakvierling 38 RETTIN. The Radar was the AEG FMG 45 RETTIN. I believe based on a FuG 245 3cm Bremen Radar developed for Luftwaffe Night fighters. This was a German Navy project but could be used on land.

This was a range only radar though I suspect it had track locking for the range gate (which is highly accurate, 6m on the FuSE Mannheim Radar and filters out jamming, chaff better than a human can). By providing an accurate range and closure rate the gyro sight would be able to provide the correct superelevation and lead into the reflector sight.

The other way it could be used in a fully blind fire mode with a central radar track locking radar such as FuMG 75 Mannheim Riese or the FuSE 64 Mannheim or presumably the FuMG 76: Marbach ( a microwave unit) or the FuMO 231 Euklid Z (German Navy Fire Control Radar). The gunners would then presumably just crank to match the dial gauges from the kommandogeraet predictor. A gun with better ballistics, servo control would have been nice but also beyond the ability to mass produce.

Note the rather large crew to keep this beast of a gun fed continuously. It doesn't matter how big your magazine. Your either going to fiddle with 1 big had magazine or lots of small easy ones.

Album description

The 2cm Flakvierling 38 was a fearsome weapon, introduced by Rheinmetall its distinguishing feature could be guessed at by its name, "vierling" quadruplet, not one but four barrels. The 2cm Flak was a light flak gun and as such it did lacked range and punch, however the Flakvierling 38 made up for this by being able to fire a large amount of shells into the air very quickly spraying its target at short range.
At the close of WW2 the German army was at the cutting edge of development into radar directed Flak guns and it was on the verge of fielding a series of weapons which the UK, USA, and Soviets didn't field till the 1950s. Among these new weapons was a version of the Flakvierling 38 which incorporated a radar.
The radar enhanced Flakvierling 38 was designed for both land and naval use and employed the AEG FMG 45 RETTIN Flak director radar. The radar scanning dish was located in the centre axis of the four barrels and about 2 inches or so in rear of the four muzzles. The RETTIN radar was linked to a amplifier/display unit Sightgerät FuG 350 ZL for gun laying. This unit was in turn linked to an optical gun sight Visierkopf 45 for final targeting. The Visierkopf 45 also known as Flakvisier 45 was a direct development of the standard Visierkopf 40 which was an optical reflector gun sight used on the normal Flakvierling 38. The new version of the sight incorporated equipment to project radar data onto the optical sight. The new radar enhanced Flak gun could operate in two forms, on its own in standalone mode, or linked computer assisted.

Operating on its own in standalone the RETTIN Flak radar could cover a narrow arc of 53 degrees to a range of 6000 to 10000 meters depending on conditions. The gunner would have to rotate and the gun to sweep the sky while keeping a keen eye on the FuG 350 display unit. When a target was picked up on the FuG 350 unit the gunner would then train the gun onto the target and engage it using the optical reflector gun sight. In standalone mode the FuG 350 sent a dot to the reflector gun sight so the gunner simply lined the dot up with the cross hair and sprayed the target. The gunner could gauge the range to the target from the FuG 350 unit but could only guess at the speed of the target.

Operating linked computer assisted the RETTIN Flak radar was far more powerful. Up to 4 guns could be linked to a truck containing an analogue computer. The computer truck was in turn linked to a FuMG.75 Mannheim Riese track locking radar. Once the Mannheim Riese track radar picked up a target it fed tracking data to the central computer. The individual flak guns would then be instructed to train towards the target. The RETTIN radar in each linked gun then sent its own radar data to the central computer which processed all the data to calculate target range, direction, and speed to calculate a firing point. The firing point data was transmitted directly to the optical reflector gun sight, gunner then trained their gun to the dot and fired, this greatly boosted the chance of hitting the target.

In both modes of operation at no visual contact is required for the gunner to engage his target meaning this system can operate at all times of the day and in all weathers. According to British B.I.O.S. reports post war 2cm Flakvierling 38 incorporating a radar laying device were tested by the Germans and this is supported by photographs of captured guns. However no evidence was found of them being tested linked with FuMG.75 Mannheim Riese or the FuSE 64 Mannheim track locking radar which had been in service from early 1944.

 

[swampyankee]

The USN was thinking about a "free-swinging" 35mm gun shortly post-WW2. It never came to fruition, possibly as a) it wasn't likely to be as good as the 40 mm Bofors b) the 40 mm Bofors was found to be insufficient against kamikazes and was expected to be insufficient against guided weapons (which were in the USN inventory by this time), and c) proximity fuzes.

While a modern 35 mm, like the GDF or the Millennium (especially the Millennium) may be quite effective against WW2 aircraft, their effectiveness depends a lot on modern fire control systems, which couldn't be built before the 1980s, at the earliest. While a Millennium with AHEAD or a 40 mm with 3P ammunition would do quite a lot of damage to incoming aircraft, they'd do far less with 1940s fire control systems and the sort of ammunition that could be made during WW2.

 

[Koopernic]

The USN was thinking about a "free-swinging" 35mm gun shortly post-WW2. It never came to fruition, possibly as a) it wasn't likely to be as good as the 40 mm Bofors b) the 40 mm Bofors was found to be insufficient against kamikazes and was expected to be insufficient against guided weapons (which were in the USN inventory by this time), and c) proximity fuzes.

While a modern 35 mm, like the GDF or the Millennium (especially the Millennium) may be quite effective against WW2 aircraft, their effectiveness depends a lot on modern fire control systems, which couldn't be built before the 1980s, at the earliest. While a Millennium with AHEAD or a 40 mm with 3P ammunition would do quite a lot of damage to incoming aircraft, they'd do far less with 1940s fire control systems and the sort of ammunition that could be made during WW2.

The General Electric XM246 used the NATO standard gun 35mm ammunition in an Oerlikon with the phalanx fire control system.
It was evaluated against the Ford XM247 Sergeant York 40mm Boffors. Due to improvements in electronics Both guns had proximity fuzes, the 35mm one being specially developed.

The GE/35mm system managed to get twice as many direct hits as the Ford/40mm system. In evaluation near misses of the 35mm were discounted because it was a non standard proximity fuse whereas the 40mm near misses were counted as direct hits because it did have a standard proximity fuse. That's how Ford Won.

The XM247/XM246 evaluation was possibly corrupt.

Matsimus has done an excellent video on it.


Sergeant York cost 9% as much as the entire Apollo program yet nothing came of it

 

[Koopernic]

Why isn't it enough for the auto cannons fire control to anticipate where to shoot the plane? Like find that it gets in range and shoot at it? Kinda like a early version of the Phalanx CIWS.

Was the technology in world War two there to allow CIWS weapon systems on ships or no?

The technology was theoretically available. The British tried in 1942.

First I'll explain how British, American and German Predictors (like the Kommandogeraet 40) worked.

Firstly elevation and bearing of the target was tracked and the range was measured by coincidence, stereoscopic, stedometric or radar range finder. These 'spherical coordinates' were converted to cartesian via trigonometric cams. Numbers were represented as shaft turns. Addition/Subtraction was via differentials, multiplication/division was by using cams to convert to logs, adding/subtracting and then using an antilog cam.

The cartesian coordinates in x,y,z were now displayed on dial gauges. In earlier machines operators set the speed of small dc motor that matched a second dial over the top. Latter servos were used to make this job redundant. The speed setting represented the speed of the aircraft. We now had parametric equation to predict the position of the target at any point in the future time (t)
x=mx.t+bx
y=my.t+by
z=mz.t+bz

This was known as tachyometry.

These coefficients was then fed into a predictor which gave the position at any time t in the future. The shell flight time was estimated and some allowance made for loading and it was run through the predictor. The x,y.z was then converted back to spherical (bearing, elevation, range) and this was run through ballistics cams to get super elevation and shell time of flight. This gave the fuze setting and the firing time. The shell bursting time was manually set with a spanner, or they had a fuse setting machine (if you've ever seen a 8.8cm FLAK 37 in a museum there is a machine in which the loaders placed two shells nose down, this machine set the time though they still had to be manually loaded. More advanced guns had a fuse setting machine integrated into an autoloader. The American 5" naval gun had the fuse setting machine in the gripper of the hoist. US terminology was 'fuse cutting' which referred to the literal burning gunpowder and paper fuse that use to provide the time delay, presumably in the days of muzzle loaders.

**************

A CIWS would certainly use the above 'mathematics' to aim the gun. However there would be several additional features to 'trim' the aim more accurately.
1 it might measure the velocity of the round at the muzzle to correct subsequent rounds.
2 it might use program a fuse as it exits the barrel based on the velocity measurement.

3 most likely it will use the same radar antenna that is tracking the target to track the round and correct the aim, this is what Phalanx does. By using the same antenna alignment issues are eliminated.

Would a WW2 system be able to do 3? I think so.

The story goes that Britain started work on the radar proximity fuse and then because they were overloaded with work handed their designs over to the USA who solved the shock hardening problem.

However Britain kept working on a fuse until 1942 and fired some rounds successfully. In their version of the fuse a 'corner reflector' was placed in the base of the standard British 3.7 inch AAA shell. The radar that was tracking the aircraft in range also tracked the shell. When the shell and target echo 'merged' a double radar pulse was sent to detonate the shell.

The British also thought they could track the shell and correct subsequent shots but found that the natural dispersion and deviation of the shell was far greater than the corrective aims for the distances involved. It would have been a matter off developing electronics to separately track the shell and target and only correcting the aim for distances where dispersion is not too great.

Radar operators often reported seeing shells in flight. During the Battle of Denmark straights the type 284 AAA radar operators on Prince of Wales saw the massive 14 inch (35cm) shells on their 50cm(20 inch) radars. SCR-584 operators saw 90mm shells.

So I think a CIWS using the Bofors 40mm round would be possible. I would abandon quad and double barrels and just use a single barrel to maintain accuracy. I would build a heavier barrel and a very solid mount to reduce dispersion and provide a firing pin to achieve individually aimed rounds. The precision of WW2 guns was less.

In those days lobe switching or conical scan was used. It would rotate at a very high rate, say 100Hz/6000RPM and have a very high pulse repition frequency of around 5000 but that was not beyond what was done. (German Wurzburg operated at 5000Hz)