Challenger II & Leclerc Armor for SB

[Stuart Galbraith]

Those two pages you posted are remarkably similar to 'A study of main battle tank options to replace Chieftain' or DEFE 48/250. I really must post that up sometime, they were looking at different options such at JagdChieftain, MBT80 and Aluminium Chieftain.

 

Thats very interesting, but what is the date on that?

 

I know a lot has been said about the Greeks being surprised how low the protection was, but is that possible they were actually offering a non DU insert version?

[Stuart Galbraith]

I dont know if this has been posted before or not, its the official report on the Friendly Fire incident in 2003 when a Challenger was destroyed by another firing HESH.

https://webarchive.nationalarchives.gov.uk/20121109064050/http://www.mod.uk/NR/rdonlyres/C2384518-7EBA-4CFF-B127-E87871E41B51/0/boi_challenger2_25mar03.pdf

[methos]

Based on numerous declassified documents, the British military changed the protection requirements for its various tank projects numerous times, which lead to the FVRDE developing several different arrays of Chobham armour - each optimized for a specific, but different levels of protection. In the 1970s for example one Chobham array had a weight efficiency of up to 3 against shaped charges, but provided no additional protection over steel against APFSDS ammo, while another array was designed to provide 1.5 times as much protection against APFSDS round than steel armour of equal weight, but was only slightly better than that against shaped charges.

 

It seems that the Chieftain Mk 5/2 and Aluminium Chieftain utilized Chobham armour arrays optimized for protection against shaped charges - the frontal armour of the former tank for example was able to stop a 6 inch HEAT warhead with a penetration of 711 mm (28 inches), but could be penetrated at close ranges by 115 mm APFSDS ammo with steel core (and tungsten slug?). Later tanks used armour with different goals and optimizations.

 

E.g. for the MBT 80 tank, I've seen six different protection levels, with KE protection at the turret ranging 405 mm (second concept, after armour was more optimized against HEAT warheads following the discovery of more powerful Soviet ATGMs) to 540 mm (after it was discovered that contemporary Soviet main battle tanks mounted a 125 mm instead of a 115 mm smoothbore gun). The weight of the early MBT 80 concepts was just 55 tonnes, the heaviest protected one (540 mm RHAe vs KE along the frontal arc of turret and hull) had a weight of 69 tonnes and was subsequently rejected.

 

 

It seems that the Challenger 1 was using a Chobham array optimized for providing protection against APFSDS ammo - at least this is what seems to have been planned in 1980/1981. While the turret armour reaching 500 mm vs KE was sufficient to stop the projected 125 mm APFSDS rounds of Soviet tanks at one kilometre range, the frontal armour was apparently believed to be penetratable by Soviet AT-5 Spandrel and AT-6 Spiral ATGMs, both estimated to reach an armour penetration of up to 700 mm.

Based on the statements by Dick Taylor (Lieutenant colonel of the RTR and author of the book, from which the comparison between Challenger 2 and M1A2 armour is taken), the Dorchester armour fitted to the Challenger 2 is optimized for reaching a high level of protection against HEAT warheads. This makes sense, given that the FVRDE believed the Soviets to field ATGMs with penetration levels between 1,000 and 1,300 mm RHA in the 1990-1995 time frame. According to Taylor, the Challenger 2's Dorchester armour reached a significantly higher level of protection against shaped charges than the turret of the M1A2 with DU armour, the latter being put at 900 to 1,300 mm RHAe by reliable sources.

 

Essentially it seems that the Challenger 2 kept a similar level of turret protection against KE, but thanks to its Dorchester armour improved hull protection against KE and doubled the protection level against HEAT warheads, all while staying at a similar weight (speaking of which: In the Challenger 1 brochure/flyer you posted sime time ago, the combat weight of the CR1 is listed as 59.5 tonnes - some other sources list it as 62 tonnes. Do you know the reason for this differences? Is this related to the applique side armour used in ODS?). I've also seen mentions regarding the Challenger 2 featuring improved roof armour over the CR1, albeit I do not know how reliable these claims are.

One MBT 80 concept (and the MBT 80 is a more weight-efficient design) reached a protection level of 480 mm vs KE at turret and upper glacis while weighing 62 tonnes, another concept reached 540 mm vs KE at the same areas at a weight of 64 tonnes.

 

 

There are however some issues: Taylor claims in his book that the Challenger 1 reached a protection level of 430 mm vs KE at the turret front and 315 mm vs KE at the hull front - this raises questions wether the goals set in 1980/1981 were met and if they are relevant for the CR2. He doesn't provide a source and this level of protection isn't very promising, given that this is essentially identical to the Leopard 2, despite the CR1 weighing 4 tonnes more. Maybe he took the data from the Shir 2 export tank or one of the MBT 80 concepts?

 

Another declassified document from the FVRDE/British military mentions that the Challenger 1 was superior in protection against KE and HEAT to the M1 Abrams, yet the hull protection and relatively low level of protection against HEAT warheads wouldn't necessarily be superior to the Abrams (unless its armour protection has been over-estimated).

 

Thats very interesting, but what is the date on that?

 

These pages are from DEFE 25/576 "Future tank policy (pre and post 1995)", dated 1. August 1980 to 31. October 1981.

 

I know a lot has been said about the Greeks being surprised how low the protection was, but is that possible they were actually offering a non DU insert version?

 

I've never seen any source stating that the Challenger 2 has DU armour or would feature elements made of DU in its armour array. From the way the DU armour has been described in declassified British documents, it seems that the Challenger 2's Dorchester has nothing to do with that.

 

The Challenger 2 apparently wasn't focused on resisting APFSDS ammo to the same degree as other tanks, because ATGMs were the main source of worry of the British military. In some sense, the roles of UK and US military (who at first optimized the armour of the M1 Abrams against HEAT, but then ended up with DU armour, which is less efficient against shaped charges, but better against KE rounds) reversed.

Edited February 21, 2019 by methos

[Stuart Galbraith]

Based on numerous declassified documents, the British military changed the protection requirements for its various tank projects numerous times, which lead to the FVRDE developing several different arrays of Chobham armour - each optimized for a specific, but different levels of protection. In the 1970s for example one Chobham array had a weight efficiency of up to 3 against shaped charges, but provided no additional protection over steel against APFSDS ammo, while another array was designed to provide 1.5 times as much protection against APFSDS round than steel armour of equal weight, but was only slightly better than that against shaped charges.

 

It seems that the Chieftain Mk 5/2 and Aluminium Chieftain utilized Chobham armour arrays optimized for protection against shaped charges - the frontal armour of the former tank for example was able to stop a 6 inch HEAT warhead with a penetration of 711 mm (28 inches), but could be penetrated at close ranges by 115 mm APFSDS ammo with steel core (and tungsten slug?). Later tanks used armour with different goals and optimizations.

 

E.g. for the MBT 80 tank, I've seen six different protection levels, with KE protection at the turret ranging 405 mm (second concept, after armour was more optimized against HEAT warheads following the discovery of more powerful Soviet ATGMs) to 540 mm (after it was discovered that contemporary Soviet main battle tanks mounted a 125 mm instead of a 115 mm smoothbore gun). The weight of the early MBT 80 concepts was just 55 tonnes, the heaviest protected one (540 mm RHAe vs KE along the frontal arc of turret and hull) had a weight of 69 tonnes and was subsequently rejected.

 

 

It seems that the Challenger 1 was using a Chobham array optimized for providing protection against APFSDS ammo - at least this is what seems to have been planned in 1980/1981. While the turret armour reaching 500 mm vs KE was sufficient to stop the projected 125 mm APFSDS rounds of Soviet tanks at one kilometre range, the frontal armour was apparently believed to be penetratable by Soviet AT-5 Spandrel and AT-6 Spiral ATGMs, both estimated to reach an armour penetration of up to 700 mm.

Based on the statements by Dick Taylor (Lieutenant colonel of the RTR and author of the book, from which the comparison between Challenger 2 and M1A2 armour is taken), the Dorchester armour fitted to the Challenger 2 is optimized for reaching a high level of protection against HEAT warheads. This makes sense, given that the FVRDE believed the Soviets to field ATGMs with penetration levels between 1,000 and 1,300 mm RHA in the 1990-1995 time frame. According to Taylor, the Challenger 2's Dorchester armour reached a significantly higher level of protection against shaped charges than the turret of the M1A2 with DU armour, the latter being put at 900 to 1,300 mm RHAe by reliable sources.

 

Essentially it seems that the Challenger 2 kept a similar level of turret protection against KE, but thanks to its Dorchester armour improved hull protection against KE and doubled the protection level against HEAT warheads, all while staying at a similar weight (speaking of which: In the Challenger 1 brochure/flyer you posted sime time ago, the combat weight of the CR1 is listed as 59.5 tonnes - some other sources list it as 62 tonnes. Do you know the reason for this differences? Is this related to the applique side armour used in ODS?). I've also seen mentions regarding the Challenger 2 featuring improved roof armour over the CR1, albeit I do not know how reliable these claims are.

One MBT 80 concept (and the MBT 80 is a more weight-efficient design) reached a protection level of 480 mm vs KE at turret and upper glacis while weighing 62 tonnes, another concept reached 540 mm vs KE at the same areas at a weight of 64 tonnes.

 

 

There are however some issues: Taylor claims in his book that the Challenger 1 reached a protection level of 430 mm vs KE at the turret front and 315 mm vs KE at the hull front - this raises questions wether the goals set in 1980/1981 were met and if they are relevant for the CR2. He doesn't provide a source and this level of protection isn't very promising, given that this is essentially identical to the Leopard 2, despite the CR1 weighing 4 tonnes more. Maybe he took the data from the Shir 2 export tank or one of the MBT 80 concepts?

 

Another declassified document from the FVRDE/British military mentions that the Challenger 1 was superior in protection against KE and HEAT to the M1 Abrams, yet the hull protection and relatively low level of protection against HEAT warheads wouldn't necessarily be superior to the Abrams (unless its armour protection has been over-estimated).

 

Thats very interesting, but what is the date on that?

 

These pages are from DEFE 25/576 "Future tank policy (pre and post 1995)", dated 1. August 1980 to 31. October 1981.

 

I know a lot has been said about the Greeks being surprised how low the protection was, but is that possible they were actually offering a non DU insert version?

 

I've never seen any source stating that the Challenger 2 has DU armour or would feature elements made of DU in its armour array. From the way the DU armour has been described in declassified British documents, it seems that the Challenger 2's Dorchester has nothing to do with that.

 

The Challenger 2 apparently wasn't focused on resisting APFSDS ammo to the same degree as other tanks, because ATGMs were the main source of worry of the British military. In some sense, the roles of UK and US military (who at first optimized the armour of the M1 Abrams against HEAT, but then ended up with DU armour, which is less efficient against shaped charges, but better against KE rounds) reversed.

 

Yeah, I can see I misread what is written in the Dick Taylor book on Challenger 2, where I thought it said DU but refered to Dorchester as 'prior to the introduction of DU' on the Abram's. I believe you are right.

 

So what would seem likely is, its inferior to the Abrams vs KE, but possibly slightly superior against HEAT?

 

I really must get that Haynes book on the Abrams I can see now.....

[methos]

From what I've read, it seems that the M1A1 HA and M1A2 have superior armour at the turret front against KE, but only along a very small arc (i.e. ±20°). The Challenger 2 has a higher level of protection against HEAT based on Taylor's statement, however he didn't quantify it. Given that the British considered the higher protection level against shaped charges enough to offset a 15% weaker turret front vs KE, it likely is more than just a slight difference in protection.

 

The hull and the side armour of the turret of the M1A2 tested in Sweden were rather weak (350 to 480 mm vs KE at 20° impact angle), so the Challenger 2 likely is better protected in these areas against APFSDS ammo aswell. Unfortunately the declassified documents do not clarify, wether the 500 mm RHAe required protection vs APFSDS are achieved along the front surfaces only or along a certain frontal arc. For the British test results of the Leopard 2A4 tanks, Taylor apparently used values for a 60° (i.e. ±30°).

Edited February 21, 2019 by methos

[RETAC21]

Thanks Methos!

 

If I can abuse you a little more, what does FEM, FES and HDS mean?

[Stuart Galbraith]

Yeah, its really good Methos, thanks for that.

 

Incidentally I meant to answer that about the weight of Challenger 1, ive got the manual upstairs ill look it out and see what the official figures are. Ive no idea what the disparity is, unless he is measuring in the wrong tons.

[methos]

Thanks Methos!

 

If I can abuse you a little more, what does FEM, FES and HDS mean?

 

Fully exposed moving - fully exposed static - hull down static.

[Stuart Galbraith]

Yeah, they learly acknowledge that the hull of the challenger is an issue. It would presumably be around this time they were considering the ERA and side armour upgrade.

[GARGEAN]

The hull and the side armour of the turret of the M1A2 tested in Sweden were rather weak (350 to 480 mm vs KE at 20° impact angle), so the Challenger 2 likely is better protected in these areas against APFSDS ammo aswell. Unfortunately the declassified documents do not clarify, wether the 500 mm RHAe required protection vs APFSDS are achieved along the front surfaces only or along a certain frontal arc. For the British test results of the Leopard 2A4 tanks, Taylor apparently used values for a 60° (i.e. ±30°).

TBH those values for M1A2 are quite surprising, considering how thick side turret is and how big LoS thickness must be at that angle? Was it median for hull and turret maybe? And was HEAT tested in same angles?

[Stuart Galbraith]

Just as a matter of interest, has there been any discussion on protection against top attack munitions? I seem to recall that C2 was improved in this respect, im just curious how much we can expect. Im thinking 20mm as ive currently got it in the Armored Brigade editor is way too low, unless you are counting the engine deck.

[Stuart Galbraith]

Methos, it has this in the introduction for the Challenger 2 manual (this is a page marked October 88 Amdt 8 so it should be prior to uparmouring).

 

Weights

 

Combat, loaded (cw ammo, fuel, ces items crew stowage but not crew----62 tonne (61 ton)

 

Training (combat loaded weight less ammo)---- 60.9 tonne (59.9 ton)

 

I hope that clarifies a bit.

[methos]

I wouldn't say that the protection levels of hull and turret sides of the M1A2 are surprising, considering that the depleted uranium armour is located at the turret front only - this means that the hull armour of the M1A1 HA/M1A2 variants is likely/largely unchanged from the M1A1 variant.

 

The frontal section of the hull side armour consists of 2.47 inches of steel armour (62.7 mm) and a 65 mm thick composite armour skirt panel (which seems to be mostly made of steel, with a hollow center and two thin inter-layers to act as NERA).

At 20° impact angle, this means there is just 373 mm material in the path of the projectile. Reaching a KE protection equivalent to 350 mm steel is rather expected. There is a reason why the Leopard 2 had three types of side skirts with much greater thickness (a design concept also found on other tanks like the Leclerc). The side skirt module of the Leopard 2A5 is 150 mm thick, assuming a 60 mm steel plate for the side hull armour, the thickness along the side of line will be 811 mm at 15° or 700 mm at 17.5° (in the Swedish trials, the Leopard 2A5's frontal hull side armour managed to resist a 120 mm APFSDS round with 700 mm penetration at impact angles up to 15°/17.5° depending on prototype).

 

Directly from the front the hull armour might provide a higher level of protection, although I am inclined to doubt that, given that only a limited amount of weight - if at all - was added to the frontal hull armour going from the M1 Abrams of 1980 (with 320 mm vs KE on the hull front according to British documents) to the M1A1 HA/M1A2.

 

 

The turret side armour at 20° will have a LOS thickness comparable (or slightly larger) to the turret front of the Leopard 2 (note that for the Abrams, the side armour at the crew compartment is about 100 mm thinner than the side armour protecting the turret bustle). While the thickness is rather good, the armour composition seems to be the issue: for achieving high levels of protection against kinetic energy, the US military had to adopt depleted uranium armour at the turret front. No DU was added to the sides of the turret.

 

The armour protection provided by the side armour is slightly higher than what seems to be the protection provided the frontal armour of the Leopard 2 from 1979 and slightly lower than that of the 2A4 model from 1988, which is probably related to the fact, that the side armour likely isn't as dense as the frontal armour. It is also worth noting that achieving 480 mm steel equivalent protection against modern APFSDS rounds (that are optimized to defeat multi-layered armour arrays) is a lot harder than reaching a protection level of 400-500 mm RHAe against APFSDS rounds available in 1979-1983.

 

____

 

As for the roof armour of the CR2, I am curious aswell, if it is designed to deal better against top-attack threats. The C1 Ariete supposedly uses a roof liner made of an elastic material to defeat the top-attack EFP warhead of the TOW-2B. Similar armour systems are offered for the modern versions of the Leopard 2 (i.e. the Evolution armour kit from IBD Deisenroth and the RoofPRO armour from RUAG), while some versions of the Leopard 2A5 and one of the Leopard 1A6 prototypes used thick passive armour to defeat artillery sub-munitions. The Challenger 2 at least seems to have thickened roof sections, though this may or may not be armour:

Edited February 22, 2019 by methos

[Stuart Galbraith]

Ive read that at least part of the roof structure was cosmetic steel to make it look prettier. Which clealry didnt help the export market much, but at least its pleasing to the eye.

 

Would 70mm be a stretch? After all, they were managing 40mm on WW2 Tigers so....

[RoflSeal]

 

Then there is an older document from the FVRDE, which actually pre-dates the Challenger 2 development, including a Challenger II and a Challenger III concept - how much Vickers Defence System followed this concepts when developing the Challenger 2 is not known:

 

Regarding the Challenger II upgrades outlined

The new clutch and hydro static steering units were developed for the Challenger 1 throughout 1982.

The weight of the Challenger 1 from 1983 to 1988 in two seperate documents increased by 2.5 tonnes (59.5 to 62.0) Even with the addition of TOGs/ICSS, the additional weight is probably a new armour package in the front hull for increased protection.

 

On the proposed changes.

A new gun was only ever fitted on one Challenger 1 IIRC, so they did not go through with this upgrade.

The new FCS (ICSS) was began fitting in 1987 and was prioritised for CAT '87 Challengers. It incorporated an Independent Aiming Mark for better on the move firing capability.

 

 

 

 

 

 

 

There are however some issues: Taylor claims in his book that the Challenger 1 reached a protection level of 430 mm vs KE at the turret front and 315 mm vs KE at the hull front

 

Doesn't this refer to the physical thickness of the armour modules?

Edited February 23, 2019 by RoflSeal

[methos]

The new clutch and hydro static steering units were developed for the Challenger 1 throughout 1982.

I don't see how this is directly relevant to the Challenger II concept. It is an improvement in terms of mobility, but not in the same sense as mentioned for the concept.

 

The weight of the Challenger 1 from 1983 to 1988 in two seperate documents increased by 2.5 tonnes (59.5 to 62.0) Even with the addition of TOGs/ICSS, the additional weight is probably a new armour package in the front hull for increased protection.

While I agree with the weight difference being unexplained by the addition of TOGS, I don't see any indication that the hull armour package was upgraded; not that this would be impossible, but armour thickness at the frontal hull remained unaltered (comparing photographs from the Challenger 1 Mark 1 brochure that Stuart posted a few months ago to photographs of the actual tank). Unfortunately the available sources do not explain much regarding the state of the tank in 1980/1981; we do for example not know if the tank in 1980 (with a weight of 59.5 tonnes) actually reached the desired levels of protection. Another factor is that the changes between Mk 1 and the later CR1 Marks are not always documented, specifically the weight change caused by them. For example the armoured ammunition bins and the new clutch might be the reason for at least some of the weight gain. Maybe some protection was added to the hull, we don't know.

 

It is also possible, that the 2.5 tonnes weight difference are refering to the applique armour for the hull; the same armour package used on the initial Challenger 2 main battle tanks (or at least an armour package with identical external appearance) added 2.5 tonnes to the combat weight according to Tankograd Publishing's booklets on the Challenger 2.

 

A new gun was only ever fitted on one Challenger 1 IIRC, so they did not go through with this upgrade.

You seem to imply that the Challenger II concept is in any way or form related to the Challenger 1 upgrades. I haven't found any indication that this is true (or that the Challenger II and III concepts were pursued in any shape or form, other than possibly serving as inspiration for some of the features of the Vickers' Challenger 2 design).

 

The new FCS (ICSS) was began fitting in 1987 and was prioritised for CAT '87 Challengers. It incorporated an Independent Aiming Mark for better on the move firing capability.

The ICSS isn't really a new FCS, it is literally called Improved CSS - but the document from 1980/1981 also only mentions a modified FCS.

 

Doesn't this refer to the physical thickness of the armour modules?

Not as far as I know. While Taylor wrote rather cryptically about "equivalent amounts" of armour, the end note is referenced in a paragraph of his book, which also cites GSR 3572, taking figures for the MBT 80 from there. In GSR 3572, these figures are RHA equivalent protection figures (RHAe), not physical thickness - this implies (unless Taylor made a mistake), that he isn't talking about physical armour thickness (with a thickness of just 430 mm or even just 315 mm, this also would be extremely thin armour modules).

[Stuart Galbraith]

ROFLSeal, many thanks for the documents, Ill happily add them to my collection.

[GregShaw]

I wouldn't say that the protection levels of hull and turret sides of the M1A2 are surprising, considering that the depleted uranium armour is located at the turret front only - this means that the hull armour of the M1A1 HA/M1A2 variants is likely/largely unchanged from the M1A1 variant.

 

The frontal section of the hull side armour consists of 2.47 inches of steel armour (62.7 mm) and a 65 mm thick composite armour skirt panel (which seems to be mostly made of steel, with a hollow center and two thin inter-layers to act as NERA)

At 20° impact angle, this means there is just 373 mm material in the path of the projectile. Reaching a KE protection equivalent to 350 mm steel is rather expected. There is a reason why the Leopard 2 had three types of side skirts with much greater thickness (a design concept also found on other tanks like the Leclerc). The side skirt module of the Leopard 2A5 is 150 mm thick, assuming a 60 mm steel plate for the side hull armour, the thickness along the side of line will be 811 mm at 15° or 700 mm at 17.5° (in the Swedish trials, the Leopard 2A5's frontal hull side armour managed to resist a 120 mm APFSDS round with 700 mm penetration at impact angles up to 15°/17.5° depending on prototype).

 

 

Where is the peanut butter?

Edited February 24, 2019 by GregShaw

[RoflSeal]

 

 

Doesn't this refer to the physical thickness of the armour modules?

Not as far as I know. While Taylor wrote rather cryptically about "equivalent amounts" of armour, the end note is referenced in a paragraph of his book, which also cites GSR 3572, taking figures for the MBT 80 from there. In GSR 3572, these figures are RHA equivalent protection figures (RHAe), not physical thickness - this implies (unless Taylor made a mistake), that he isn't talking about physical armour thickness (with a thickness of just 430 mm or even just 315 mm, this also would be extremely thin armour modules).

 

 

The page it refers to, and as I read it, it refers to the geometric thickness of the armor module itself.

 

 

 

 

 

 

You have to remember, Challenger's armour is sloped at 60 degrees, turning 315mm and 430mm to 630 and 860mm LOS thickness. The former figure is definitely in the right ballpark for the correct thickness.

Edited March 16, 2019 by RoflSeal

[methos]

The page it refers to, and as I read it, it refers to the geometric thickness of the armor module itself.

 

 

 

 

 

 

You have to remember, Challenger's armour is sloped at 60 degrees, turning 315mm and 430mm to 630 and 860mm LOS thickness. The former figure is definitely in the right ballpark for the correct thickness.

No, it is not. The values cited in this passage for the MBT 80 are not armour thickness figures. Assuming that the author would mix up weight values, armour thickness figures and protection estimates in the same two sentences doesn't make much sense.

[RoflSeal]

 

The page it refers to, and as I read it, it refers to the geometric thickness of the armor module itself.

 

 

 

 

 

 

You have to remember, Challenger's armour is sloped at 60 degrees, turning 315mm and 430mm to 630 and 860mm LOS thickness. The former figure is definitely in the right ballpark for the correct thickness.

No, it is not. The values cited in this passage for the MBT 80 are not armour thickness figures. Assuming that the author would mix up weight values, armour thickness figures and protection estimates in the same two sentences doesn't make much sense.

 

 

 

Screenshot section mentions nothing about protection. "Putting" implies about the geometric thickness of chobham modules mounted. Just like ATR-1

Edited March 16, 2019 by RoflSeal

[methos]

Just read the declassified documents available at the National Archives regarding the Main Battle Tank 80 programme (including General Staff Requirement 3572 - Replacement of Chieftain Tank, which he states as source for his figures, but that is only half correct). The figures in GSR 3572 are protection levels in rolled homogenous armour equivalency rather than physical armour thickness. As a tank commander Mr. Taylor may not have studied English literature and linguistics, so that's why he uses "putting" in the sentence. "[P]utting" hardly implies geometic thickness, as there is nothing be put anywhere (unlike for example actually putting armour modules inside/at a main battle tank), although I agree that his choice of words isn't particularly good.

 

 

Unless the footnote containing the values for the Challenger 1 (for which I haven't manage to find a source yet) is refering to physicial thickness and lieutenant colonel Taylor is mixing figures for equivalent protection with physical dimensions, it should be assumed that he is talking about protection levels.

[RETAC21]

How do you find that in the National Archives? I must be fat fingered because I never get anything of worth.

[Paul Lakowski]

Strangely enough I had a IJIE research paper a decades ago, which was sourced from the Chobham research institute . This paper explored long rod penetration into slanted multiply-spaced- thin plates of steel. Rick and I had an argument about this because it showed major reduction in penetration of the witness block and as such I thought it proved sloped armor to be better. He responded with a contemporary paper showing how sloped armor offered less resistance than vertical block by 1 projectile diameter.

[Interlinked]

Strangely enough I had a IJIE research paper a decades ago, which was sourced from the Chobham research institute . This paper explored long rod penetration into slanted multiply-spaced- thin plates of steel. Rick and I had an argument about this because it showed major reduction in penetration of the witness block and as such I thought it proved sloped armor to be better. He responded with a contemporary paper showing how sloped armor offered less resistance than vertical block by 1 projectile diameter.

 

I think that for complex armour arrays, there are some additional nuances that could favour a sloped armour design. While a sloped homogeneous steel block alone is easier to defeat with an LRP than a flat homogeneous steel block of the same LOS thickness, that might not necessarily be true for the steel back plates of many modern complex armour arrays. It is reasonable to assume that an LRP emerging from a projectile breakup-inducing array will tend to be broken up to some extent and be most likely yawing. When such a penetrator impacts the back plate of the armour array, its behaviour will not be the same as intact and non-yawing long rods impacting flat and sloped homogeneous blocks of steel. The penetration of a yawing LRP is much more sensitive to the yaw angle on sloped RHA blocks than on a flat RHA block.

 

If an LRP is yawing with a upward pitch (tip of rod is yawed away from the surface of a sloped plate) at the moment of impact on a sloped plate, the penetration efficiency is vastly degraded. If an LRP is yawing with an downward pitch at the moment of impact on a sloped plate, the amount of penetration degradation is only a little lower than for a flat plate, and only in a certain range of yaw angles. So if your sloped armour array is made to break up an LRP and generate yaw in the optimum direction, it could be much, much more efficient than a flat armour array of the same mass.