Technical question about extended range artillery ideas applied to AAA

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Deleted member 1487

In modern artillery extended range, full bore shells with base bleed enhancements have been known to extend range heavily, though at some penalty to accuracy. Would these concepts, both of which were known by WW2 and the former apparently somewhat tested by the Germans for AAA and both for artillery, applied to AAA have improved performance without penalty to accuracy? Supposedly there is some turbulence caused by Base Bleed projectors, while I still haven't found a reason by ERFB wasn't used by anyone in their AAA. The closest that anyone got is the Mark VI QF 3.7 inch British gun that had a liner that smoothed out the driving bands on a shell, which reduced wind resistance.
Could these technologies in WW2 have been introduced to make AAA more effective or were they only viable for artillery, or perhaps only viable post-WW2, but by which time SAMs rendered then unworkable?
 
The purpose of base-bleed is to keep velocity up at the top of the ballistic arc, where velocity is lowest. However, AAA shells only need to reach altitude, which means that maximizing explosive payload is more important than range.
 

Delta Force

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The purpose of base-bleed is to keep velocity up at the top of the ballistic arc, where velocity is lowest. However, AAA shells only need to reach altitude, which means that maximizing explosive payload is more important than range.

Getting to altitude quickly is important too, but that's what the large powder charges are for. Maybe rocket assisted shells could be useful for extending the reach of some weapons though?
 

Deleted member 1487

The purpose of base-bleed is to keep velocity up at the top of the ballistic arc, where velocity is lowest. However, AAA shells only need to reach altitude, which means that maximizing explosive payload is more important than range.
That doesn't seem to be the case. Based on the latest technical info the base bleed gases are used for the first 1-2 seconds to keep muzzle velocities up to push it higher in a ballistic arc, not keep up velocity at the top of the arc.
https://en.wikipedia.org/wiki/Base_bleed
Most of the drag on an artillery shell comes from the nose of the shell, as it pushes the air out of its way at supersonic speeds. Shaping the shell properly can reduce this greatly. However, another powerful source of drag is the low-pressure area left behind the shell due to its blunt base. This drag is difficult to remove, because the shell must be "nose heavy" in order to have proper ballistics, and cannot easily be shaped into a more aerodynamic form.

Base bleed can reduce this drag without extending the base of the shell. Instead, a small ring of metal extends just past the base, and the area in the rear of the shell is filled with a small gas generator. The gas generator provides little to no thrust, but simply increases the pressure in the area behind the shell with an inflow of gas, dramatically reducing the drag. The only disadvantages are a small loss of accuracy due to the somewhat more turbulent airflow, and a small loss in explosive payload due to some of the space inside the shell being taken up by this mechanism.

Since base bleed extends the range by a percentage, it is only really useful on longer range artillery where some 5 km to 15 km increase can be achieved. Until the late 1980s the small gains in range was not considered worthwhile for field artillery. Base bleed shells are becoming more common in units equipped with modern artillery which have far greater range than the old ones.

Getting to altitude quickly is important too, but that's what the large powder charges are for. Maybe rocket assisted shells could be useful for extending the reach of some weapons though?
I thought about the rocket assisted part too, but it seems that there are still issues with the motors and propellants that when fired from an artillery piece disrupts their proper functioning. During WW2 the Germans did have RAP for their rail guns:
http://www.lonesentry.com/ordnance/28-cm-r-gr-4331-rocket-assisted-prerifled-projectile.html
Maybe it is doable for say a 105mm shell?

Looking further into German developments it seems they tested a number of discarding sabot or flanged shells that improved muzzle velocity at least 20% or more, which would dramatically shorten time to altitude and increase range of the projectile. The issue there though is the resulting projectile is significantly smaller. Perhaps the improved accuracy from being faster is better than having a bigger shell?
 

Delta Force

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I thought about the rocket assisted part too, but it seems that there are still issues with the motors and propellants that when fired from an artillery piece disrupts their proper functioning. During WW2 the Germans did have RAP for their rail guns:
http://www.lonesentry.com/ordnance/28-cm-r-gr-4331-rocket-assisted-prerifled-projectile.html
Maybe it is doable for say a 105mm shell?

Looking further into German developments it seems they tested a number of discarding sabot or flanged shells that improved muzzle velocity at least 20% or more, which would dramatically shorten time to altitude and increase range of the projectile. The issue there though is the resulting projectile is significantly smaller. Perhaps the improved accuracy from being faster is better than having a bigger shell?

Some sources indicate that the sabot rounds of the time had reduced accuracy due to the separation process being less developed.
 

Deleted member 1487

Some sources indicate that the sabot rounds of the time had reduced accuracy due to the separation process being less developed.
That was the British 77mm Sabot round, as it didn't come apart easily, not something I've seen as a problem for the German ones, which apparently had some valve that the propellant of the shell filled and it fell off without a problem once outside the barrel. Apparently it came apart so easily though that it had problems working with muzzle breaks. That wasn't an issue for FLAK guns, but for tank guns and AT guns it was an issue.
 

CalBear

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The reality is that the size of the shell, the bursting charge and the resulting amount of and lethal range of shrapnel is vastly more important to AAA than range extension. Getting an extra 5,000 feet of altitude is of little use if the 128mm gun is now firing what amounts to a 25mm light flak shell or an 8.8cm Flak 41 throwing up a 12mm exploding bullet.
 

Deleted member 1487

The reality is that the size of the shell, the bursting charge and the resulting amount of and lethal range of shrapnel is vastly more important to AAA than range extension. Getting an extra 5,000 feet of altitude is of little use if the 128mm gun is now firing what amounts to a 25mm light flak shell or an 8.8cm Flak 41 throwing up a 12mm exploding bullet.
I get what you're saying, but the sped to altitude resulted in a lot more accuracy. The 128mm FLAK was several orders of magnitude more accurate and required far less shells to bring down a bomber than the old 88. The 88mm sabot round was supposed to be a 65mm or 70mm exploding round with over 1000m/s muzzle velocity (a flange version apparently got over 1100m/s muzzle velocity instead of the regular 800m/s). 105mm guns used saboted 88mm rounds.
https://books.google.com/books?id=6...AEIHDAA#v=onepage&q=flak triebspiegel&f=false

In another thread the Germans found out they had 2-3x more shoot downs with contact fuses rather than timed, so if they are going for accuracy and direct hits then nothing above a 50mm shells with a direct hit is necessary to bring down a B-17/24 or Lancaster with one hit.

The Allies had an even bigger advantage if they saboted their AAA as they had the SCR-584 to guide theirs plus proximity fuses. Of course historically the Brits got good late war performance out of the Mark VI QF 3.7 inch AA gun with a quasi-sabot version of their gun:
https://en.wikipedia.org/wiki/QF_3.7-inch_AA_gun#Mk_VI
Like the Mk IV this was based on the 4.5 inch barrel design lined down to 3.7 inches, and using the 4.5 inch size cartridge. However, Colonel Probert changed the barrel to have gradual rifling: the rifling groove depth decreased to zero over the last five calibres of the barrel before the muzzle. This smoothed the two driving bands of a new design shell giving reduced air resistance and hence better ballistic performance, and causing far less barrel wear. The maximum ceiling for the gun was about 15,240 metres (50,000 ft). It was mounted on the Mounting Mk IIA and therefore deployed in static emplacements only. In service from 1944 to 1959.
I'm gathering it was a 113mm barrel and propellant charge behind a 94mm shell and a section that had a semi-squeeze bore principle to smooth out the driving band and eliminate that drag on the shell. Apparently this dramatically improved the velocity of the shell and increased range by a huge margin.
 

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I get what you're saying, but the sped to altitude resulted in a lot more accuracy. The 128mm FLAK was several orders of magnitude more accurate and required far less shells to bring down a bomber than the old 88. The 88mm sabot round was supposed to be a 65mm or 70mm exploding round with over 1000m/s muzzle velocity (a flange version apparently got over 1100m/s muzzle velocity instead of the regular 800m/s). 105mm guns used saboted 88mm rounds.
https://books.google.com/books?id=6-UDDQAAQBAJ&pg=PA169&lpg=PA169&dq=flak+triebspiegel&source=bl&ots=Vi4maglFxT&sig=GdUrLdo9jMqha0pjdxgu_TIXmcg&hl=en&sa=X&ved=0ahUKEwixx6TLwd7QAhXGRCYKHc2YAeEQ6AEIHDAA#v=onepage&q=flak triebspiegel&f=false

In another thread the Germans found out they had 2-3x more shoot downs with contact fuses rather than timed, so if they are going for accuracy and direct hits then nothing above a 50mm shells with a direct hit is necessary to bring down a B-17/24 or Lancaster with one hit.

The Allies had an even bigger advantage if they saboted their AAA as they had the SCR-584 to guide theirs plus proximity fuses. Of course historically the Brits got good late war performance out of the Mark VI QF 3.7 inch AA gun with a quasi-sabot version of their gun:
https://en.wikipedia.org/wiki/QF_3.7-inch_AA_gun#Mk_VI

I'm gathering it was a 113mm barrel and propellant charge behind a 94mm shell and a section that had a semi-squeeze bore principle to smooth out the driving band and eliminate that drag on the shell. Apparently this dramatically improved the velocity of the shell and increased range by a huge margin.
The 12.8cm shell was close to three times the weight of the 8.8cm, that gave it a vastly larger shrapnel radius and a correspondingly higher hit probability.

The 128mm had a higher velocity because it was propelled by roughly 400% more power in each charge. redesigning the 8.8cm Flak breech to handle higher pressure would allow the same sort of velocity.

What is the reference for the Luftwaffe preferring contact rather than timed? Contact is exceptionally difficult against a target moving several hundred miles an hour that is 6-10 miles away, with crosswinds at various altitudes, and almost literally impossible at night. Contact detonation would also result in a rain of 8.8cm, 10.5cm and 12.8cm bombs falling across the target area to detonate when striking the ground or roofs (be more dangerous than the air attack itself).
 
I remember reading about the contact shooting too. Just don#t remember where exactly I had read it. Aparently they fuzed teh shell for highest altitude and contact, and shot for contact. Missing shells exploded at max. But the better results mentioned above in terms of bringing down bombers had been mentioned. I guess being hit by an exploding shell is vastly more damaging than suffering shrapnell on your usually lightly armored hull / wings.
I think most of the efficiency increase came from as you no longe tried to guess the correct height and then no longer tried to time the not quite so accurate fuze correctly for the barrage effect, and instead just concentrated on just hitting the bomber. Meaning you no longer had to spend time setting fuzes correctly but just fired as fast as you could.
 
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The reality is that the size of the shell, the bursting charge and the resulting amount of and lethal range of shrapnel is vastly more important to AAA than range extension. Getting an extra 5,000 feet of altitude is of little use if the 128mm gun is now firing what amounts to a 25mm light flak shell or an 8.8cm Flak 41 throwing up a 12mm exploding bullet.
That's flat-out false. Historically AAA has always been some of the highest-velocity artillery in any nation's artillery park, second only to anti-tank guns (which were sometimes based on them). They often sacrificed shell size to achieve this by using necked-down cartridges with a far larger propellant-to-shell weight ratio than other guns. Improvements to AA guns usually focused on increasing muzzle velocity and maximum altitude more than increasing shell weight.

Not only were these highly necked-down AAA shells never necked up to increase shell size (at an expense of muzzle velocity), they were often necked down even further in an effort to increase their potential as AA guns. The QF 13 pounder 9 cwt AA gun was adapted from the QF 18 pounder by mating the 18-pounder's propellant charge with the QF 13-pounder's shell and barrel, and proved a much better AA gun than guns based on unmodified 18-pounder shells. The same principle is implied with wiking's QF 3.7 inch AA gun quote, which states that the British chose to line down the 4.5 inch barrel to 3.7 inches and increase muzzle velocity/aerodynamics/range at the expense of shell weight. At no point did a nation seriously consider producing AAA with a lower velocity and lower maximum altitude in exchange for a heavier shell. The focus has always been higher velocity, higher maximum altitude, and faster rate of fire.
 
What is the reference for the Luftwaffe preferring contact rather than timed? Contact is exceptionally difficult against a target moving several hundred miles an hour that is 6-10 miles away, with crosswinds at various altitudes, and almost literally impossible at night. Contact detonation would also result in a rain of 8.8cm, 10.5cm and 12.8cm bombs falling across the target area to detonate when striking the ground or roofs (be more dangerous than the air attack itself).
I wish somebody really expert like Sbiper but in reverse order,
- it would have a self destruct like even USN 40mm...
- I think its simply an acceptance that calculating timing on a long slow trajectory v a fast moving target is just too hard its better to send lots of cheaper, faster firing, faster flight time shells up.
- don't think night matter you are not trying to actually hit with individual shells just saturate an area with 1000s?
 

Deleted member 1487

What is the reference for the Luftwaffe preferring contact rather than timed? Contact is exceptionally difficult against a target moving several hundred miles an hour that is 6-10 miles away, with crosswinds at various altitudes, and almost literally impossible at night. Contact detonation would also result in a rain of 8.8cm, 10.5cm and 12.8cm bombs falling across the target area to detonate when striking the ground or roofs (be more dangerous than the air attack itself).
I didn't say they preferred it, just that it was tested at the end of the war and found it more effective than timed fuses and contrary to expectation it was a lot easier to hit a bomber in both a bomber box and stream than thought:
https://www.alternatehistory.com/forum/threads/doppelzünder-flak-shell-introduced-in-1942-effects-on-air-war.370250/
There was still a timer aspect to detonate the shells before they hit the ground.

Edit:
here is a report by the captured German General of FLAK describing the contact fuse theory and combat experience:
http://downloads.sturmpanzer.com/FMS/NARA_FMS_D031.pdf

Calbear, you were part of that thread the last time we discussed it about 6 months ago in the thread above.
 
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Deleted member 1487

Surely proximity fusing trumps both timing and altitude ??
What? I mean in terms of getting a shell to explode near a target it was much more efficient as you didn't need to time a fuse, but you still need to put the round near a target, so velocity and ability to actually reach the target trump a proximity fuse in terms of importance (same with accurate gunnery data from a gun laying radar and predictive computer). Even without proximity fuses the Allies were able to get far improved accuracy due to having an integrated 10cm wavelength gun laying radar, predictive computer, and servo-motors as well as auto-fuse setter, with proximity fuses offering a relatively minor buff to shoot downs on top of that. Of course they weren't dealing with German aircraft flying at 25k feet like the B17s were or 30k like the B29s were. But the Brits developed the QF 4.5 inch AAA gun lined/necked down to 3.7 inches to get very high shell velocity to reduce shell flight time and improve maximum altitude so that faster and higher flying aircraft could be engaged. That 1944 gun design continued to be the primary strategic air defense weapon until the SAM was introduced in 1959 in Britain.
 
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