Sabot-ed FLAK shells

[Yoozername]

I will check on some things, but some things really stick out here. I question a 88mm FlaK 18/36 needs 30 seconds to reach top altitude. The increase in performance you are saying would require a substantial increase in muzzle velocity.

[stg 44]

I will check on some things, but some things really stick out here. I question a 88mm FlaK 18/36 needs 30 seconds to reach top altitude. The increase in performance you are saying would require a substantial increase in muzzle velocity.

Just going by the linked report. The General of FLAK said an average of 30 seconds to reach 8000m. Significantly less for 128mm FLAK though.
I gather standard 88mm FLAK shells rapidly lost speed due to high drag as a result of the poor aerodynamic shape of the shell.

[Yoozername]

That report does not say that. It mentions engagement time.

[stg 44]

That report does not say that. It mentions engagement time.

Went back and checked, you're fight. I have seen the 30 second number elsewhere though, I think Ian Hogg's book on German artillery, which has a subsection on AAA. Of course he might have been referencing something similar (a 30 second engagement time) as well. That said I have seen a chart for velocity drop off in an 88 shell, which within 5 seconds had fallen from the muzzle velocity of over 800mps to around 500mps.

[Yoozername]

It might be around 15-20 seconds. The 88mm FlaK 18/36 ceiling was below the B17 altitude. If one were to use a 75mm HE in a 88mm sabot, It would be maybe a 13 pound sabot vs. a 20 pound 88mm full bore. Maybe giving a muzzle velocity of 1200 M/s. Again, it might get up to the B17s, but it is less fragments. Flight time might be quicker to the height that a normal 88mm HE would achieve, but it must also include the extra time to get to the B17s.

[T. A. Gardner]

This still comes down to the same problems. The main one is that by 1944 it's becoming apparent to everybody that aircraft will be flying higher and faster than a gun can economically shoot shells to in quantity.
Even if you reduce the flight time and raise the altitude some, you still can't shoot more rounds than before. The loading / firing sequence doesn't change for the gun. So, as the plane's altitude and speed increase the amount of firing time decreases and the number of possible shells fired decreases with it.
Even raising the accuracy some makes the whole proposition iffy at best. If each shell costs more to make, and possibly increases barrel wear shorting its life, then you're back at achieving only limited better results for the extra cost and effort.
That's why everybody went to SAMs. You needed radar and a fire control system anyway. If you can get a SAM to hit say 25% of the time, and firing four means a certain hit, it could be economically more feasible to use a SAM than fire say several hundred rounds from dozens of guns. The other plus is a SAM has far greater altitude and range than a gun meaning you have far more engagement time. It also means you need fewer SAM batteries to obtain the same coverage as guns would take. The reduction in manpower alone is probably sufficient to make it economical even if a SAM costs far more than the equivalent number of shells required for a shoot down.

That's why postwar projects like Green Mace got cancelled. A huge sabot firing gun was just not economical, not to mention nearly immobile.

[stg 44]

It might be around 15-20 seconds. The 88mm FlaK 18/36 ceiling was below the B17 altitude. If one were to use a 75mm HE in a 88mm sabot, It would be maybe a 13 pound sabot vs. a 20 pound 88mm full bore. Maybe giving a muzzle velocity of 1200 M/s. Again, it might get up to the B17s, but it is less fragments. Flight time might be quicker to the height that a normal 88mm HE would achieve, but it must also include the extra time to get to the B17s.

Pardon? The 88 was used against the B-17 historically throughout the war and was probably the primary shoot down caliber against all bombers. The effective ceiling (ability to engage for 30 seconds) was at an altitude of 8000m:
https://en.wikipedia.org/wiki/8.8_cm_Flak_18/36/37/41

Also the Germans trialed a number of discarding sabot (not HE-FSDS) with the cup sabot design or ring sabots at the mid-section and base and there was a ring based sabot model that achieved over 1100mps with a 7cm projectile. As I said though accurately getting the timing right to blow it up in it's effective blast radius is nearly impossible barring luck given the mechanical variations of within .5 seconds during which a timed fuse shell would travel outside it's effective blast radius. That's on top of the extra time needed to set the fuse to the right time as fed by the gun laying computer that will result in further inaccuracies. During testing the Germans found it was actually easier to get direct hits against heavy bomber formations rather than downing them with mechanically timed blasts in box barrages. So a faster, more accurate shell which without a pause to set the timer enables a faster rate of fire and increased chance of hitting a bomber actually has a substantially increased chance to hit and kill a bomber versus even an impact fused standard 88 shell.

[stg 44]

This still comes down to the same problems. The main one is that by 1944 it's becoming apparent to everybody that aircraft will be flying higher and faster than a gun can economically shoot shells to in quantity.
Even if you reduce the flight time and raise the altitude some, you still can't shoot more rounds than before. The loading / firing sequence doesn't change for the gun. So, as the plane's altitude and speed increase the amount of firing time decreases and the number of possible shells fired decreases with it.
Even raising the accuracy some makes the whole proposition iffy at best. If each shell costs more to make, and possibly increases barrel wear shorting its life, then you're back at achieving only limited better results for the extra cost and effort.
That's why everybody went to SAMs. You needed radar and a fire control system anyway. If you can get a SAM to hit say 25% of the time, and firing four means a certain hit, it could be economically more feasible to use a SAM than fire say several hundred rounds from dozens of guns. The other plus is a SAM has far greater altitude and range than a gun meaning you have far more engagement time. It also means you need fewer SAM batteries to obtain the same coverage as guns would take. The reduction in manpower alone is probably sufficient to make it economical even if a SAM costs far more than the equivalent number of shells required for a shoot down.

That's why postwar projects like Green Mace got cancelled. A huge sabot firing gun was just not economical, not to mention nearly immobile.

Green Mace got cancelled because SAMs finally started working. It's hard to beat a guided missile for accuracy and adjustments in flight. That said in WW2 we aren't talking about jet bombers flying at 50k feet, so at 25k feet a 1500mps AAA dart shell is going to have a ton more utility and accuracy than against Cold War Jet bombers, especially because SAMs are not technologically viable in WW2.
Each sabot shell would actually be cheaper than a standard 88 shell and wouldn't increase the wear rate on the barrel given a smooth bore barrel. In fact it eliminates the cost of making a liner and relining a barrel periodically. There is actually a reduction in barrel wear because it would take fewer shells to down bombers, which means guns don't fire as long or as much to achieve effect. When you only need 1/3rd or less the shells to achieve a kill you're actually limiting the amount you need to fire per gun, which saves gun wear and the material needed to make shells.

[Yoozername]

Boeing B-17 Flying Fortress Specifications
Maximum Speed: 318 mph (511 km/h) at 25,000 ft (7,625 m)
Cruise Speed: 160 mph (257 km/h)
Service Ceiling: 30,000 ft (9,144 m)

[stg 44]

Boeing B-17 Flying Fortress Specifications
Maximum Speed: 318 mph (511 km/h) at 25,000 ft (7,625 m)
Cruise Speed: 160 mph (257 km/h)
Service Ceiling: 30,000 ft (9,144 m)

So the max speed height is within the effective range of the 88, while the max height, not something they flew often if ever, was below the max height of the 88 (9900m):
https://en.wikipedia.org/wiki/8.8_cm_Flak_18/36/37/41

Again though the saboted shells would be able to reach further than the standard shell and do so faster, so they could extend the range of the 88 to over 10,000m for effective ceiling.

[Sheldrake]

Each sabot shell would actually be cheaper than a standard 88 shell and wouldn't increase the wear rate on the barrel given a smooth bore barrel. In fact it eliminates the cost of making a liner and relining a barrel periodically. There is actually a reduction in barrel wear because it would take fewer shells to down bombers, which means guns don't fire as long or as much to achieve effect. When you only need 1/3rd or less the shells to achieve a kill you're actually limiting the amount you need to fire per gun, which saves gun wear and the material needed to make shells.

Well the Luftwaffe didn't agree with your calculations......

[stg 44]

Each sabot shell would actually be cheaper than a standard 88 shell and wouldn't increase the wear rate on the barrel given a smooth bore barrel. In fact it eliminates the cost of making a liner and relining a barrel periodically. There is actually a reduction in barrel wear because it would take fewer shells to down bombers, which means guns don't fire as long or as much to achieve effect. When you only need 1/3rd or less the shells to achieve a kill you're actually limiting the amount you need to fire per gun, which saves gun wear and the material needed to make shells.

Well the Luftwaffe didn't agree with your calculations......

Got a source? They didn't have a working HE-FSDS shell by the end of WW2 and the Brits continued to develop it; they were trying to get one working for the 105mm FLAK based on the Peenemunde arrow shell but I have the British testing document and it was breaking up upon firing. It took them a while to get a working arrow shell doing post war too, a couple of years I think, so the Germans just started too late to get it going and didn't put enough resources behind it. They did a lot of fantastic work with the ring and cup sabot rounds, but weren't production capable with them given the war situation as of mid-1944.

So what I'm positing is that they start work on an arrow type shell in say 1940 so that it is production ready in 1943 and making an impact as of that point when it would be possible to start making some.

[Yoozername]

No. 8000 m (26,240 ft) effective ceiling for the 88. It can lob things higher, but again, the effective time of engagement falls to nothing.

[stg 44]

No. 8000 m (26,240 ft) effective ceiling for the 88. It can lob things higher, but again, the effective time of engagement falls to nothing.

Yes, that's what I said. Effective ceiling is the altitude at which the gun could engage for at least 30 seconds. At it's max ceiling it could engage for about 14 seconds.

[T. A. Gardner]

Yoozername has it right. It isn't the maximum ceiling for the gun, but rather the slant range that really matters. For the 8.8cm bombers flying at 25,000 feet give it just a few minutes of engagement time assuming they fly almost directly over the battery. Also, by 1944 the problem is no longer the B-17. It's becoming what follows it. Now you have aircraft like the:

B-29 Cruise 220 mph, ceiling 31,850 flying at say 28,000 feet
or
B-29D Cruise 244 mph, ceiling 36,900 feet flying at say 30,000
or
B-36 Cruise 230 mph ceiling 43,600 feet flying at 30 to 35,000 feet.

That doesn't even include jets that are on the horizon in 1944-45.

The slant range of a battery of even 12.8cm guns is growing so small as to be nearly useless. All sabots do is buy a bit of range and engagement time. Better to begin work early on a SAM that can engage up to say 20 to 25 miles from the battery to say 50,000 feet than bother with trying to upgrade the guns.

Looking back on what was possible, a SAM with a 25 mile, 50,000 foot ceiling would have been possible to build. You use a ballistic flight trajectory so the missile is falling on the target from above at a slant rather than heading into it from below. Using a simple interferometer and continuous wave radar in the final stage of intercept was well within possibility. All you need now is a proximity fuze. That too is doable as space isn't as limited in a missile, nor are the G's so violent and excessive as in a gun's shell. The hard part would be getting it to work when it goes sonic.
If you build one that carries say a 100 kg to 200 kg warhead you only have to get close...
The Germans have radars that would suffice for search and guidance. Using a ballistic flight path for most of the intercept simplifies that to using either beam riding or simple gyroscope guidance. The terminal guidance is within the possibilities of analog and electro-analog equipment.

That would give a battery on the order of 10 to 15 minutes engagement time against WW 2 era bombers. With just a 10% kill rate it would be doing better than guns. The biggest problem the Germans would face in service with such a weapon would be jamming of the electronics. Even if the missiles cost say a third of what an Me 109 did, it would be cost effective at 10% kill rates.