You'd put the containment armor directly around the engine. It wouldn't take dozens of inches. Whether you use Newton's rule of thumb (penetration ends when the mass of armor displaced equals the mass of the shell that hit it) or more modern rules - a failing turbine disk is neither a precision-engineered anti-armor weapon, nor a heavy battleship shell.
I'd bet the plane would still be able to take off, if it made it that far. But it never would - with the extra weight guaranteeing that no airline would buy it, Finance would never sign off on funding to even complete the design work.
(Yes, the reality behind my quips about Sales and Finance is more complex:)
Full containment is probably possible, but it would render the aircraft nearly useless, not just economically uncompetitive.
A 70kg chunk of nickel alloy is very dense, and at 800m/s , that’s 20 MJ. Thats about the same as 5kg of TNT, but focused on a small area.
For comparison, a modern 120mm artillery shell fired from a tank or similar field artillery has 10-20 MJ of kinetic energy.
A couple thousand kg of armour could likely contain that kind of energy, but it would also translate that energy to the engine mounts, wing, spar, and fuselage if it was not going to become a projectile itself. You could easily stop a fragment and critically damage a spar attachment, rupture a wing fuel tank, or end up with translational shock damage to any number of critical systems and structures. You’d probably have to double or triple your engineering margins of the entire aircraft, probably doubling the weight of the airframe.
So yeah, possible probably. But not on an aircraft designed to carry passengers or freight. It would be the biggest 6 seat aircraft ever built lol.
Interestingly, if you work backwards from that cargo capacity, you can arrive at a much smaller aircraft that could possibly feature full containment, because engine diameter and energy goes way down and containment starts to look much more practical. I would not be surprised if containment could be achieved in the small biz jet scale, with just significant sacrifices in cargo or range.
OTOH even the A10 warthog does not have full disk containment, and it’s probably the strongest candidate ever fielded for such a project… so, ymmv.
- which bear no resemblance to a failed turbine disk. And have about twice the muzzle velocity, which makes huge difference in penetrating a modern armour systems. Ditto their far greater density, vs. nickel alloy.
OTOH, your "A couple thousand kg of armour could likely contain..." seems too charitable. High-bypass jet engines are big. Beyond that, I'm more optimistic about mitigating shocks and such.
A critical parameter here - https://en.wikipedia.org/wiki/A380#A380F The freight variant was to have a 6,400 mile range carrying 150t of payload. So we could squander 25t per engine on disk containment and shock mitigation, and still have a 50t payload. Or a 3-digit passenger headcount.
Bottom line, there is no real-world difference between your "nearly useless" and my "disastrously uneconomical". Neither one will be designed, let alone built.
For the A10, I'd say military priorities would always block full disk containment - because every pound used for that is a pound they don't have for more weapons or munitions or range or armour or fuel or runway length or electronics or whatever. And over most of the 360 which disk fragments could exit a warhog's engines, there's nothing critical which they could hit.
Good counterpoints all, I think. I’m impressed that we could write off 50t and still have an airplane. That seemed so preposterous that I did not consider it, honestly. Turns out big stuff is big.
Now we can go to the running of the bulls with our respective napkin backs, and see who attracts the bull!
Yes but on the warthog the discs are very far away from the pilot. Or pretty much anything else that matters. The fuselage can take a lot of a beating.
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You'd put the containment armor directly around the engine. It wouldn't take dozens of inches. Whether you use Newton's rule of thumb (penetration ends when the mass of armor displaced equals the mass of the shell that hit it) or more modern rules - a failing turbine disk is neither a precision-engineered anti-armor weapon, nor a heavy battleship shell.
I'd bet the plane would still be able to take off, if it made it that far. But it never would - with the extra weight guaranteeing that no airline would buy it, Finance would never sign off on funding to even complete the design work.
(Yes, the reality behind my quips about Sales and Finance is more complex:)
Full containment is probably possible, but it would render the aircraft nearly useless, not just economically uncompetitive.
A 70kg chunk of nickel alloy is very dense, and at 800m/s , that’s 20 MJ. Thats about the same as 5kg of TNT, but focused on a small area.
For comparison, a modern 120mm artillery shell fired from a tank or similar field artillery has 10-20 MJ of kinetic energy.
A couple thousand kg of armour could likely contain that kind of energy, but it would also translate that energy to the engine mounts, wing, spar, and fuselage if it was not going to become a projectile itself. You could easily stop a fragment and critically damage a spar attachment, rupture a wing fuel tank, or end up with translational shock damage to any number of critical systems and structures. You’d probably have to double or triple your engineering margins of the entire aircraft, probably doubling the weight of the airframe.
So yeah, possible probably. But not on an aircraft designed to carry passengers or freight. It would be the biggest 6 seat aircraft ever built lol.
Interestingly, if you work backwards from that cargo capacity, you can arrive at a much smaller aircraft that could possibly feature full containment, because engine diameter and energy goes way down and containment starts to look much more practical. I would not be surprised if containment could be achieved in the small biz jet scale, with just significant sacrifices in cargo or range.
OTOH even the A10 warthog does not have full disk containment, and it’s probably the strongest candidate ever fielded for such a project… so, ymmv.
Yes. But when the goal is kinetic penetration of modern armour, they don't use artillery shells. Instead -
https://en.wikipedia.org/wiki/Armour-piercing_fin-stabilized...
- which bear no resemblance to a failed turbine disk. And have about twice the muzzle velocity, which makes huge difference in penetrating a modern armour systems. Ditto their far greater density, vs. nickel alloy.
OTOH, your "A couple thousand kg of armour could likely contain..." seems too charitable. High-bypass jet engines are big. Beyond that, I'm more optimistic about mitigating shocks and such.
A critical parameter here - https://en.wikipedia.org/wiki/A380#A380F The freight variant was to have a 6,400 mile range carrying 150t of payload. So we could squander 25t per engine on disk containment and shock mitigation, and still have a 50t payload. Or a 3-digit passenger headcount.
Bottom line, there is no real-world difference between your "nearly useless" and my "disastrously uneconomical". Neither one will be designed, let alone built.
For the A10, I'd say military priorities would always block full disk containment - because every pound used for that is a pound they don't have for more weapons or munitions or range or armour or fuel or runway length or electronics or whatever. And over most of the 360 which disk fragments could exit a warhog's engines, there's nothing critical which they could hit.
Good counterpoints all, I think. I’m impressed that we could write off 50t and still have an airplane. That seemed so preposterous that I did not consider it, honestly. Turns out big stuff is big.
Now we can go to the running of the bulls with our respective napkin backs, and see who attracts the bull!
100t actually - 25t per engine, of which there are four. And the plane could still carry 50 tonnes of cargo/people.
That’s wacky, for lack of a better word. It’s like a whole flying apartment building.
Thanks, but I think I'll be running with the chickens. ;)
That sounds interesting. Not necessarily better. Who was it that said quantity has a quality all its own?
Yes but on the warthog the discs are very far away from the pilot. Or pretty much anything else that matters. The fuselage can take a lot of a beating.
https://en.wikipedia.org/wiki/File:A10Thunderbolt2_990422-F-...
A failed disk from engine #1 is just a few feet from engine #2.
That's a good point. Somehow I didn't think of that.