JEWELLLW@VM.CC.PURDUE.EDU (Larry W. Jewell) (02/05/91)
From: "Larry W. Jewell" <JEWELLLW@VM.CC.PURDUE.EDU> ----------------------------------------------------------------------- One nice thing about discribing something poorly is that you get more answers than you could have hoped for otherwise. Both views below are interesting in that they represent differing philosophies about "add-on" armour. I still think I would prefer a nice cozy 17 inches of hard plate (Go "Big Mo"!). ------------------------------------------------------------------------ In article <1991Jan28.041718.10532@cbnews.att.com> you write: > > >From: "Larry W. Jewell" <JEWELLLW@VM.CC.PURDUE.EDU> >Footage from Sandy Arabia shown M-60's with large flat plates attached >to the turret. Is this reactive armour? Any idea how it works and how >much confidence the tankers have in it? I've seen T-72's with smaller, >and much more numerous boxes attached to the turret. Is this difference >demanded by the rounder shape of a "T" or is it Soviet thinking? > Larry, A few answers... 1) Is this reactive armor? -Yes 2) Reactive armor is basically just blocks of explosive attached to the tank. It works by disrupting the hot gas jet put out by a HEAT (High Explosive Anti Tank) round. These rounds work by exploding a shaped charge about a foot away from the armor, which forms a very thin, superhot gas jet which then burns through the tank's armor. (This is the reason HEAT rounds and antitank missiles such as the TOW have a foot long spike on the front-to get correct standoff distance for the jet formation. But I digress...) The idea behind reactive armor is to disrupt this jet as it forms by exploding a charge as the HEAT warhead goes off. The jet, to use language from my real job, is "very susceptable to initial conditions" Disrupting it even a little bit vastly reduces its effectiveness. On average, you can expect reactive armor to halve the penetration ability of a given HEAT round. The M60 series desperately needs the additional armor protection. The M1 series' Chobham armor is especially designed to defeat HEAT rounds, which is why you don't see it attached to the M1s. Reactive armor has started a whole new mini arms race. The TOW IIA has a small explosive charge in front of the main one, to set off the reactive armor before jet formation. I've been told that the Soviets now have countermeasures to this, .... Reactive armor is a godsend to tankers in another way. Back when the Sagger came out, people began to predict the demise of the tank from the proliferation of cheap antitank guided missiles. However, reactive armor has now cast great doubts on the ability of these ATGMs, all armed with HEAT warheads, to kill modern tanks equipped with it. However, RA does nothing to stop a sabot round, the tank's main anti tank round, so tanks again become the premiere anti tank weapon.... (A sabot round is basical- ly just a big bullet- no explosive at all.) 3) How much confidence do tankers have in it? I can't speak for all my brethren, but I'll lie, cheat and steal to get it on my M60A3 if I get called up... 4) I don't know why the Soviets have many small blocks compared to our few large ones. I'll ask around- someone at my unit might know... Hope this helps.. -- Eric R. | "Any quantity of interest can be found by solving edremy@d31ha2.Stanford.EDU | the Schrodinger equation of the system. The Chemistry Dept, Stanford U | solution is left as an exercise for the reader." ======================================================================== 7 From: "Nicholas C. Hester" <IA80024@MAINE> Date: Wed, 30 Jan 91 16:47:00 EST I'm sure others have sent you letters already, but just in case, the large flat plates are applique armor. This is simply extra armor welded in place. <Routing material edited from second e-mail, LWJ> >From what I have gathered, it is to add thickness to certain area, enhancing protection. There was an extensive discussion of this on sci.military in the past few months. Alas, Bill has no FTP account to reach archived material. <THAT'S OK, BILL, *I* FORGIVE YOU! LARRY> Applique is different than reactive armor where the round is pre-detonated or the blast force is retarded by the shaped charge of the reactive armor. Anti- tank missiles get around this by a penetrator rod that pre-detonates the charge. Hope this helps. Nicholas C. Hester | | ia80024@Maine.Bitnet | Farhvergnugen: "I've fallen, and I can't get up" | ia80024@Maine.Maine.edu | | ************************************************************************ *The world will never have lasting peace so long as men reserve for war* *the finest human qualities. * *********************** John Foster Dulles ***************************** Larry W. Jewell JEWELLLW@VM.CC.PURDUE.EDU
thos@softway.sw.oz.au (Thomas Cohen) (02/07/91)
From: thos@softway.sw.oz.au (Thomas Cohen) In article <1991Feb5.043146.6128@cbnews.att.com> JEWELLLW@VM.CC.PURDUE.EDU (Larry W. Jewell) writes: > > [ lots of stuff about reactive armour and HEAT rounds ] > >the tank. It works by disrupting the hot gas jet put out by a HEAT >(High Explosive Anti Tank) round. These rounds work by exploding a >shaped charge about a foot away from the armor, which forms a very >thin, superhot gas jet which then burns through the tank's armor. >(This is the reason HEAT rounds and antitank missiles such as the TOW >have a foot long spike on the front-to get correct standoff distance >for the jet formation. But I digress...) The idea behind reactive While the standard explanation has been for years that a hot stream of gas 'hoses' its way through the armour, Ian Hogg in his "Encyclopedia of Ammunition" says that the 'slug' which was the metal lining of the shaped charge has a velocity ~32 000 fps (which is somewhat faster than the speed of detonation of the explosive) and with this velocity, it penetrates using its kinetic energy. He also admits that that is simplified so I am a little bit confused. Are there any real-type ammunition experts out there who can shed light on this? And also how the speed of the slug is faster than the detonation speed? Bunker killing: In another thread, people were talking about penetrating concrete bunkers with whatever came to hand. In the same book, there is mention of a "Rochling" concrete piercing shell, designed during WW2 in Germany, and used early in the war. The shells were made from some hard metal (Vanadium or Tungsten &c) and they didn't make many before they realized they needed the metal to make machine tools. Hitler was also paranoid about the Allies finding ones that hadn't exploded and had to give permission for them to be used. Accounts show that they were very effective when they were used : one test against the Maginot Line fortifications (after they'd been captured) penetrated 5m of earth, 36m of concrete, a layer of broken stone (doesn't say how thick) through a chamber and 5m into the floor of the chamber! It wasn't fused so it did not explode (if it had been fused correctly it would have exploded in the chamber). Which brings to mind a question : How long does it take 36m of concrete to cure, or would they put it down in layers? -- thos cohen |Softway Pty Ltd "Stopping to pick up passengers would disrupt |ACSnet: thos@softway.oz the timetable" - Alderman Cholerton, on why|UUCP: ...!uunet!softway.oz!thos the council's buses didn't stop for passengers|Internet: thos@softway.oz.au
rakoczynskij@ncar.UCAR.EDU (Jurek Rakoczynski) (02/11/91)
From: asuvax!gtephx!rakoczynskij@ncar.UCAR.EDU (Jurek Rakoczynski) In article <1991Feb7.012722.118@cbnews.att.com>, thos@softway.sw.oz.au (Thomas Cohen) writes: > > How long does it take 36m of concrete to cure, or would they put it down > in layers? I worked a few years as a field inspector for a civil engineering firm. While the technology of concrete is complicated, here are a few typical guidelines to use for discussion (1, this is very simplified, 2, references typical, run-of-the mill, average concrete, and 3, from memory 15 years ago): The concrete pour of a slab (like for a roof of a bunker) would probably have been done as a continous pour within the limits of working in the day light, and the strength of the forms to support the horizontal loads of the poured concrete (like a dam). The cure time (and strength of the concrete) is not typically affected by the thickness, to the extent that moisture, temperature, salt (curing agents) remain fairly constant. Don't confuse drying out the surface of concrete with curing concrete. Once you have the proper moisture content, you want to prevent the water from evaporating or being removed from the mix so that the cement can hydrate. The hydration is how the strength develops. Typical 2500 - 3500 psi concrete will achieve % of strength as follows (from memory): 1 day = ~80% max 3 day = ~90% max 30 day = ~95% max and continues to cure for several years. If I am REALLY off, please correct me, but I think it's accurate enough for discussion. -- UUCP: {ncar!noao!asuvax | uunet!zardoz!hrc | att}!gtephx!rakoczynskij Inet: gtephx!rakoczynskij@asuvax.eas.asu.edu Voice: +1 602 581 4867 Fax: +1 602 582 7111