Jump to content

Recommended Posts

Just curious about all those images we have seen of blown up T-72 and their variants, where a massive explosion blew the turret off the tank. Was this an issue with their Automatic Fire Extinguishing Systems, or was it an integral weakness of the design? Would a more sophisticated western made fire suppression system have prevented this? Modern AFES activate in milliseconds. They should have been able to put out any catastrophic fire within the T-72s. Would the T-72 and its variants be a safer tank if a better AFES were retrofitted to it?

Edited by On the way
Link to post
Share on other sites
  • Replies 79
  • Created
  • Last Reply

Top Posters In This Topic

I don't think that a fire suppression system can handle more than combustions from minor aerosolized hydraulic oil and other burn processes that require atmospheric oxygen. The blown turrets come from chain reactions of ammunition propellant stored in the carousel. The only way to prevent that is to not have propellant stowed in locations like that.

Link to post
Share on other sites

Yep.

 

OTW,if you watch the twitch stream of 'Gunner Heat PC' that ive linked on the game forum (or heck, just download the demo) you will see the nature of the problem. You might be able to slow a slow burn of propellent to get the crew off, but that is going to be about it. If the warheads cook off, its goodnight Vienna.

 

The real problem I think was less the way the ammunition was stored in the tank (they stored it mostly the right way, below the ring). The problem was the complete overmatch of the silver bullet rounds against the armour package on T72M1. Against a T72BV or T90 it might have been different, at least frontally. Low internal volume probably doesnt help any of course.

Edited by Stuart Galbraith
Link to post
Share on other sites

Show me a "slow burn of propellant" inside a tank. :P

 

Slow is a highly relative term here. Sure, it burns "much quicker" (=detonates) when ignited in the gun chamber because of the confinement, and if spilled open and burned only in small quantities it's merely a conflagration. While it may be possible for a turret crew to survive the spontaneous combustion of one cartridge ripped open in the breech and partially spilled, given the choice I'd rather avoid it, fire suppression system or not. In case of propellant cartridges in close proximity to each other, in the immortal words of Ron Burgundy, "Boy, that escalated quickly."

Link to post
Share on other sites

The cellulose shells of the propellant charges cannot burn without oxygen. I personally found that. But the thickness of the cellulose shell is not very big. So it has to work extremely quickly.

The older fire extinguishing system's heat sensors take a short time to react. To do this, flame and excessive heat must act on the sensor tips. Only then is the interior flooded with extinguishing gas. And of course the old sensors are not everywhere. Under unfavorable circumstances the fire has to grow to warm up the old sensors. However, if the propellant powder catches fire, no oxygen is required for further burning. Then no extinguishing gas will help...

 

The new Russian fire suppression systems use infrared sensors to quickly detect a flame or heat spot. The response time is then so short that the extinguishing gas floods the interior extremely quickly. In this case there is a good chance of suppressing the fire.

 

The unfavorable fact remains that so much ammunition is stored in the crew's room. A lot of fatalities can still happen. And, very important, the fire suppression system must be kept ready for use!

 

Another shortcoming, btw, you cannot trigger the system from the outside.

Edited by Stefan Kotsch
Link to post
Share on other sites

Was shrouding the carousel ever considered ? Even a lightweight shroud could stop some fragments of a long rod that would otherwise be deadly. Of course the turret floor protects it somewhat already.

 

Working from memory here but there's the turret floor, and inside the carousel each cartridge is in its own metal tube to hold it in place and to give it some extra protection. But 1mm aluminum tube isn't going to protect against much.

Link to post
Share on other sites

Show me a "slow burn of propellant" inside a tank. :P

 

Slow is a highly relative term here. Sure, it burns "much quicker" (=detonates) when ignited in the gun chamber because of the confinement, and if spilled open and burned only in small quantities it's merely a conflagration. While it may be possible for a turret crew to survive the spontaneous combustion of one cartridge ripped open in the breech and partially spilled, given the choice I'd rather avoid it, fire suppression system or not. In case of propellant cartridges in close proximity to each other, in the immortal words of Ron Burgundy, "Boy, that escalated quickly."

Well its the difference between a keg of gunpower going off and a rocket I guess. There is clearly a difference, though Ill concede few inside a burning tank ever get to appreciate much of a difference. Kahalani is one, he was stuck in the bottom of a burning Centurion and somehow got out.

 

One of the advantage of a bagged charge system surrounded by suppressant, though we did partly spoil the effect by leaving HESH rounds in the crew cabin.

 

Ive got a nagging feeling I read somewhere the Iraqi's DID fit fire suppressant equipment, French, to at least some of their T72's. It doesnt seem to have made much difference.

Link to post
Share on other sites

The cellulose shells of the propellant charges cannot burn without oxygen. I personally found that.

 

Uh, sorry, but No.

Cellulose nitrate will burn without air oxygen, period. It can be made "less sensitive" to spontaneous combustion but once that it burns you won't stop the reaction by removing the air around it. Cellulose trinitrate is obviously most sensitive, less so dinitrocellulose, and mononitrocellulose (also known as celluloid) is least sensitive. But even then there are documented cases of self-combustion (such as on a hot June afternoon in Paris, 1959). But even celluloid is only "relatively safe" to handle. And of course it's possible to mix the cellulose nitrate with other materials to desensitivize it for normal operating conditions. I don't know how you conducted your test but I'd suspect that you didn't reach the ignition temperature of whatever sample you may have had in your hands.

Link to post
Share on other sites

 

The cellulose shells of the propellant charges cannot burn without oxygen. I personally found that.

 

Uh, sorry, but No.

Cellulose nitrate will burn without air oxygen, period. It can be made "less sensitive" to spontaneous combustion but once that it burns you won't stop the reaction by removing the air around it. Cellulose trinitrate is obviously most sensitive, less so dinitrocellulose, and mononitrocellulose (also known as celluloid) is least sensitive. But even then there are documented cases of self-combustion (such as on a hot June afternoon in Paris, 1959). But even celluloid is only "relatively safe" to handle. And of course it's possible to mix the cellulose nitrate with other materials to desensitivize it for normal operating conditions. I don't know how you conducted your test but I'd suspect that you didn't reach the ignition temperature of whatever sample you may have had in your hands.

 

He means the cellulose combustible case. There is likely sufficient inert cellulose fibres that it requires oxygen to burn.

Link to post
Share on other sites

Carousel is surrounded by a lot of barriers. Top is covered with a sheet steel cover that has anti-radiation lining on both sides. It's basically laminated UHMWPE, and it works as a shield against fragments. Sides are either behind fuel tanks or some sheet steel barriers. And then the ammo itself is held within steel trays (not aluminium, IIRC).

Link to post
Share on other sites

Fine, so it's steel ... and helps against 95% of the 10,000 fragments that are flying around after an APFSDS impact. That still leaves 500 white hot metal fragments that can perforate into the propellant cartridges where but a single is sufficient to trigger the chain reaction. ;)

Link to post
Share on other sites

Setting off ammo with fragments requires high kinetic energy. The heat of the fragments is practically irrelevant, not because it isn't hot enough, but because it can't transfer that thermal energy instantaneously.

 

If the armour is breached by an APFSDS round, I don't think it's physically possible for there to be more than a few fragments capable of setting off ammo unless you've fired a round that overmatches the tank's armour by a huge degree.

 

There's also a funny side effect of using tough modern alloys for long rod penetrators: they resist breaking apart when penetrating complex tank armour, including ERA, which also means that they don't break apart easily after perforating the armour. That means drastically less fragments compared to the shitty steel APFSDS that the Soviets used half a century ago. Food for thought.

Edited by Interlinked
Link to post
Share on other sites

Well, you have to punch through before you can start worrying about behind-armor effects. Your shitty steel APFSDS will never get the chance to show off its awesome destructive potential in the first place.

Link to post
Share on other sites

Was shrouding the carousel ever considered ? Even a lightweight shroud could stop some fragments of a long rod that would otherwise be deadly. Of course the turret floor protects it somewhat already.

It is shrouded. From the top and partially from sides. Relatively thin so won't hold any direct hits, but can help with spalling.
Link to post
Share on other sites

Still can't find the alloy that lets a long rod penetrator keep its strength and ductility while penetrating complex armour but can break apart into 10,000 fragments afterward, though.

 

So, by your count, how many fragments are to be expected (and do you count penetrator fragments only, or also armor plate material).

Link to post
Share on other sites

There is no unified model for calculating penetrator and armour fragments. Some studies have been made and there is at least one semi-empirical model that I know of, but it is based on a monolithic steel target which is not relevant for modern tanks.

 

That said, if you shoot 120mm APFSDS at the hull of tanks that can only stop certain 105mm APFSDS, the outcome isn't so hard to predict.

Edited by Interlinked
Link to post
Share on other sites

So then, what's your estimate of the number of fragments generated by perforating APFSDS in a T-72 (above Xg mass or Xmm diameter, your pick), if you're sure that "it's not 10,000", and why?

 

I deliberately picked a round number to indicate that it's not an empirical measurement but I'd be surprised if I was off in the order of magnitude. I'm willing to learn, though.

Link to post
Share on other sites

I can't help but notice two things:

1. You make a lot of demands, but feel no obligation to back up your own claims.

2. You seem to have a personal vendetta against T-72s and fantasize about them being destroyed.

 

Anyway...

 

To achieve a 50% probability of igniting the propellant, you need fragments that have approximately 12-14 kJ of KE, equivalent to the ability to penetrate 30-40mm of aluminium plate. (http://btvt.info/5library/vbtt_1981_01_ujazvimost_vistrelov.htm)

 

If you fired a solid chunk of WHA the size of a fire extinguisher at the tank, then yeah, you will get your 500 fragments, each capable of setting off the ammo. But if you were just firing something like M833, you should only expect less than 10 fragments. There's just not enough KE in the residual penetrator, and most of the fragmentation will be particles so small that they turn into sparks, or dust that can barely penetrate skin, or small pieces that can only penetrate a few millimeters of sheet aluminium.

Link to post
Share on other sites

M829 and M829A1 massively overmatched the T-72M and T-72M hull front armour and particularly the side armour, and it was not uncommon to shoot until the tanks brewed up.

 

Where exactly do you see a contradiction between this and the laboratory results?

Link to post
Share on other sites

M829 and M829A1 massively overmatched the T-72M and T-72M hull front armour and particularly the side armour, and it was not uncommon to shoot until the tanks brewed up.

 

Where exactly do you see a contradiction between this and the laboratory results?

Right - winning rather than losing the battle makes a huge difference in the efficacy of various survivability measures because taking multiple hits will be rare for the winning side and routine for the losing side, and a tank which is disabled can be expected to be covered on the winning side somewhat better.

 

No protective system is possible which will permit a tank to be penetrated many times by long rods and not be a total loss or near enough to a total loss.

Edited by KV7
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...