Spaced Armor

[seppw]

shaped charge jets need a optimum standoff for the jet stream to form properly. This is understood to be ~ 2 caliber diameters for 1st gen warheads [WW-II into 1960s]. This allows about 3-4 caliber penetration of armor under optimum circumstances. IE 3" warhead should penetrate ~ 9-12" armor with 2 diameter standoff. Once this standoff is increased by a spaced plate - the effective penetration drops steadily from peak to 2-3 diameters penetration @ 4-5 diameters standoff - down to 1 diameter penetration at over 6 diameters standoff .

The Next gen shaped charges materialized in the 1970s and needed optimum standoff of 6 calibre diameters- generating penetrations of up to 10 projectile diameters. Given the general warhead size of 4-6" - that means they need 3-5 feet standoff. To defeat such a warhead by spaced plate alone , you'd need over 14 diameters standoff or 5-7 feet standoff.

Having said all this, the WW-II shaped charge makers didn't always know this and full calibre tank shells could not offer more than 1/2 diameter standoff. Worse since all these shells were spun by gun riffling , any increasing standoff sharply decreased penetration.

However there were German shells that were spun shells with small standoff. These were able to get just over 1 diameter penetration. SMALL SPACED plates should actually increase penetration in initially [to the 2 diameter optimum standoff], but with even small increase in standoff - the penetration should plummet again.


BTW German spaced plates/mesh was originally designed to defeat Soviet hard core ATR and defeat HE shells from tank guns. The benefit for shaped charges was only realised later.

I guess you meant "up to 5 projectile diameters" or "10 projectile radii".

[Christian Ankerstjerne]

Interesting, another thing to consider is that the schützen/side skirt plates were installed on ~10 deg downward slope the idea being small caliber rounds would deflect down into the ground.

Do we have any information that this was by design? Against anti-tank rounds, which were fired very close to the ground, a vertical surface would offer a greater relative slope and thickness. Anything hung so that the center of gravity is beyond the mounting point will see its lower part pivot towards the side of the mount.

[seppw]

A post-war US report (WAL 710/930-1) had the following to say

There are conflicting data on the performance of spaced armor arrangements against shaped-charge shell. Tests during World War II showed that the 105 mm HEAT M67 shell could be defeated by spaced armor consisting of two 1-1/2" thick homogeneous armor plates spaced 12" apart. NDRC reported that spaced armor is superior to solid steel on a weight basis for protection against shaped charged shell. This advantage was attributed largely to the effect of the increased standoff caused by the spaced armor arrangements. The British report that "Hollow charge shell likewise exhibit a similar degradation of performance against such combination targets [...]. The efficiency of the jet deteriorated markedly with space distance [...]."

More recent information on newly designed shaped-charge shell indicate that they are not degraded by spaced armor combinations unless the skirting plates are placed at distanced from the main armor which are impossible from a practical engineering viewpoint to use in actual vehicle designs.

Thanks for sharing this, Christian. What I think is the most remarkable statement is the following: "More recent information on newly designed shaped-charge shell indicate that they are not degraded by spaced armor combinations unless the skirting plates are placed at distanced from the main armor which are impossible from a practical engineering viewpoint to use in actual vehicle designs."
That's obviously wrong. The track effectively dictates that a sideskirt will be track_width+x far away from the side armor plate without making the vehicle much wider.
Sideskirts are even used in mordern tanks, although not exclusively to stop HEAT, but also in order to stop jacketed APFSDS.

[Paul Lakowski]

shaped was originally designed to defeat Soviet hard core ATR and defeat HE shells from tank guns. The benefit for shaped charges was only realised later.

I guess you meant "up to 5 projectile diameters" or "10 projectile radii".

Yes there were no sub calibre shaped charge projectiles back then.

[Yoozername]

Also angle of impact seams to of been as important as a normal HV AP projectile,

Interesting, another thing to consider is that the schützen/side skirt plates were installed on ~10 deg downward slope the idea being small caliber rounds would deflect down into the ground.

I think you are just making things up. The plates used for the 'skirt armor' were mild steel. The original design intent was to cause anti-tank rifle rounds, specifically the Soviet 14.5 mm tungsten ammunition, to shatter or become unstable. Testing showed this to be effective. They would also detonate HE rounds set on super-quick fusing. Of course, they would also detonate HEAT rounds.

Can you cite any information regarding your downward sloping consideration????

[Yoozername]

Interesting that the Panzerfaust were sample tested using plates with an air gap!

The Pzf 30 (groß)’s 140mm warhead was found to be effective against
T-34s, KV-1s, Shermans, Churchills and Matildas. It might not have
always penetrated the frontal armour or gun mantlet, but it was effective
with flank and rear shots. There were instances when the penetrating jet
went out the opposite side of a turret after piercing the near side. Test
firings had been conducted against 5cm and 10cm plates with a 5cm air
gap between them. Factory proof testing was conducted by firing
randomly selected Panzerfäuste at three 5.5cm armour plates with 6cm air
spaces between each. No efforts were made to improve the penetration on
later models. However, some testing was undertaken to find a better lining
material for the shaped-charge cone. Tungsten was found to be more
effective than the sheet steel in use. They apparently never discovered that
copper was the most effective liner. Regardless, tungsten and copper
were scarce materials. Further development concentrated on improving
the range, accuracy and reliability of new Panzerfaust models. The firing
systems on both models proved highly susceptible to moisture.
The concept of small and large Panzerfäuste was dropped for subsequent
models. Having mostly non-interchangeable components complicated
manufacture, and the Pzf 30 (klein) did not offer much of a cost saving.
Also, units were requesting mostly the Pzf 30 (groß) and not bothering
with the Pzf 30 (klein).

[Yoozername]

This video shows a Panzerfaust 30 Grob being fired at a Sherman tank target during training. Note the clean holes in the armor. The warhead had a very thin sheet metal skin, and it does not make much in the way of fragmentation. you can skip to the 30 second mark.

[seppw]

Also angle of impact seams to of been as important as a normal HV AP projectile,

Interesting, another thing to consider is that the schützen/side skirt plates were installed on ~10 deg downward slope the idea being small caliber rounds would deflect down into the ground.

I think you are just making things up. The plates used for the 'skirt armor' were mild steel. The original design intent was to cause anti-tank rifle rounds, specifically the Soviet 14.5 mm tungsten ammunition, to shatter or become unstable. Testing showed this to be effective. They would also detonate HE rounds set on super-quick fusing. Of course, they would also detonate HEAT rounds.

Can you cite any information regarding your downward sloping consideration????

Yep. The test I remember showed that the sideskirt didn't stop the projectiles, but rather rendered those unable to penetrate the tank's main side armor. In the test the tank(/the target representing the tank) was shot from 3 or 9 o'clock, though. Perhaps the ammo would bounce at less favorable angles. Whether it was angled in order to do exactly that or simply damage the round even more is a different question.

[Christian Ankerstjerne]

Yep. The test I remember showed that the sideskirt didn't stop the projectiles, but rather rendered those unable to penetrate the tank's main side armor. In the test the tank(/the target representing the tank) was shot from 3 or 9 o'clock, though. Perhaps the ammo would bounce at less favorable angles. Whether it was angled in order to do exactly that or simply damage the round even more is a different question.

What were the projectiles that were tested, and by whom?

[Yoozername]

The Germans did test using the Soviet antitank rifle. I believe it was Spring of 1943.

Even with larger Tungsten ammunition, spaced armor was effective in WWII. It was found that the APCR round had bolts of tungsten carbide that could be defeated. Not so much by the thin skirt armor, but rather by two thicker plates. The first plate would shatter/disturb the penetrator, which would fail on the next plate. Even the mighty US 90mm APCR showed this failing in tests. Post WWII, the bolts were put in hardened steel sheaths and even had caps of some sort.

The failure mode that light antitank weapons had on the skirt armor was not stand-off, but rather damaging the actual front of the hollow-charge. The US troops in Vietnam used chain-link fencing and it worked well against the older RPGs. This method also defeated the RPG round by disrupting its electrical fuse.

[Christian Ankerstjerne]

The Germans did test using the Soviet antitank rifle. I believe it was Spring of 1943.

I know. My question was in regards to the claim that the mild steel skirts were hung at an angle to deflect the projectiles into the ground.

[Mobius]

10° is not going to deflect anything into the ground. If the angle was in fact set at this angle it may be just a construction factor meant for the bottom edge to be closer to the tank so it wouldn't be hung up on vegetation. In that picture the bottom edge looks like it is interior to the outer track edge.

[Christian Ankerstjerne]

10° is not going to deflect anything into the ground. If the angle was in fact set at this angle it may be just a construction factor meant for the bottom edge to be closer to the tank so it wouldn't be hung up on vegetation. In that picture the bottom edge looks like it is interior to the outer track edge.

I'm not in any way supporting, or even entertaining, the argument that the inclination was intended to deflect projectiles. As I wrote above, it is possible that it isn't even intentional design feature, as anything hung loosely from one side will have such a slope.

What I'm saying is that member who made the claim in the first place needs to back it up, or stop passing off uninformed guesses as facts. Without any information, the rest is just speculation.

[Tankdriver1]

I have somewhere a test report of different German variants shielded armor. In short, it was intended not only against cumulative munitions, but also against conventional armor-piercing caliber shells with an explosive chamber. When you break the screen worked, the fuse, the projectile has lost orientation and hit the armor had side or even the rear portion of the projectile.
Especially strongly it was in contact with the projectile at an angle (as is usually the case in reality).
The screens also worked very well against the sub-calibre projectiles falling at an angle. The tracks, hung on the tower's armor, were hit by a sub-calibre projectile, but only a scratch remained on the armor. Without trucks, this armor at the same angle made its way through.

[EdwardRobert]

I understand about angled and sloped armor but what exactly does it mean to have spaced armor? What tanks use it and what ammo is best to defeat it?