Bulletproof Airplanes

[Photon Guy]

With airplanes they have to be both light and strong. That being the case, is it possible to make an airplane that's bulletproof? Can they make an airplane that's strong enough that bullets can't penetrate the fuselage? 

[MigL]

Yes.
 A .22 pistol round from 50 yards away will not damage the aluminum alloy or composite fibre/resin skin panels.
But a 20 mm round from a GE/GD M61 will go through composite, aluminum, interior upholstery, people, and come out the other side.

And the 30 mm GE GAT-8/a, firing depleted Uranium rounds, will penetrate tank armor, and probably blow off part of the plane's fuselage.

All depends on the kinetic energy of the bullet you're trying to stop.

[toucana]

5 hours ago, Photon Guy said:

With airplanes they have to be both light and strong. That being the case, is it possible to make an airplane that's bulletproof? Can they make an airplane that's strong enough that bullets can't penetrate the fuselage? 

Short answer - No, it isn’t possible or practical to make airplanes that are completely bullet-proof. But dating back to the days of WW2  several methods were used by the allied forces to try and mitigate the damage done to their warplanes by enemy fire.

One was the installation of self-sealing fuel tanks in bombers and fighters to prevent a large loss of fuel, and avert the risk of high octane fuel fires when a gas tank was hit.

https://en.wikipedia.org/wiki/Self-sealing_fuel_tank

These self-sealing tanks made use of a double skin of rubber, one layer of which was vulcanized rubber  (hardened with sulphur), and the other was natural rubber. When the tank was perforated by a bullet, leaking fuel would come into contact with the untreated layer which would swell and seal the leak. These  tanks could allegedly withstand .50 rounds.

Another interesting approach was that of Austrian mathematician Abraham Wald who escaped to the USA and worked for the Statistical Research Group (SRG) in New York during WW2.

https://medium.com/@penguinpress/an-excerpt-from-how-not-to-be-wrong-by-jordan-ellenberg-664e708cfc3d

Abraham Wald was asked to analyse the pattern of bullet holes found in heavily damaged US bombers returning from combat sorties over Europe, and to recommend where to place additional armour plating to protect the planes better without adding too much weight to them.

Wald made the highly counterintuitive suggestion that the extra armour plating should be added to those areas of the planes that *didn’t* have bullet holes in them ! He did so because he realised that his SRG only got to study those planes which had actually made it back to base because they *hadn’t* been hit in any vital area of their fuselage  - e.g. the engines.

This is a good example of recognising and avoiding ‘Survivorship Bias’ in engineering analysis.

https://en.wikipedia.org/wiki/Survivorship_bias

[swansont]

As MigL implies, the clarification needed is “bulletproof against what?” and then one needs to know how thick of a material you’d need. You could calculate the mass of the plane from its size, and see if you could generate enough lift. 

But toucana’s post strongly suggests “no” for anything but small-arms fire

[toucana]

A third way of making warplanes ‘bullet-proof’ during WW2 was to make them fly so fast that enemy interceptors simply couldn’t catch up with them for long enough to shoot them down.

This was done by the allies with a unique plane called the de Havilland DH.98 Mosquito which first flew in 1941, and was said to be the fastest operational aircraft in the world at that time

https://en.wikipedia.org/wiki/De_Havilland_Mosquito

The Mosquito had an airframe made almost entirely of wood, and was designed as an unarmed fast bomber, pathfinder, and photo-reconnaissance aircraft.

From 1942 onwards, Mosquitoes were also used by BOAC as fast transports to carry small high-value cargo from neutral countries through enemy controlled airspace. In particular this meant ferrying consignments of high-grade industrial ball-bearings from Stockholm in Sweden to RAF Leuchars in the UK. Sweden was a neutral country during WW2, but the Germans controlled Norway and Denmark and western Europe, which meant the Luftwaffe could simply shoot down any conventional allied cargo craft over the sea.

The RAF Mosquitoes used by BOAC for their blockade running flights to Sweden were stripped of their guns and cameras to reduce weight, and they flew so fast that not even the Luftwaffe Focke-Wulf FW 190 interceptors could catch them.

They not only brought back cargoes of ball-bearings that were vital for making aero-engines and instrumentation, they also brought back VIP refugees such as the Danish nuclear physicist Nils Bohr who escaped the Gestapo by fleeing to neutral Sweden, and was flown back to Britain in the bomb-bay of a Mosquito in 1943.

This 'high & fast' strategy was subsequently used by the Lockheed U2 and Lockheed SR-71 Blackbird spy-planes flown by the USA in the 1950s and 1960s respectively.

[atom_cosmic10]

I found this article from the MIT news, wonder If they could use this new material.

 

Here's the link of the article: https://news.mit.edu/2022/polymer-lightweight-material-2d-0202

This is a paragraph with more information on the topic:

The researchers found that the new material’s elastic modulus — a measure of how much force it takes to deform a material — is between four and six times greater than that of bulletproof glass. They also found that its yield strength, or how much force it takes to break the material, is twice that of steel, even though the material has only about one-sixth the density of steel.

[dimreepr]

1 hour ago, atom_cosmic10 said:

I found this article from the MIT news, wonder If they could use this new material.

 

Here's the link of the article: https://news.mit.edu/2022/polymer-lightweight-material-2d-0202

This is a paragraph with more information on the topic:

The researchers found that the new material’s elastic modulus — a measure of how much force it takes to deform a material — is between four and six times greater than that of bulletproof glass. They also found that its yield strength, or how much force it takes to break the material, is twice that of steel, even though the material has only about one-sixth the density of steel.

It's not just about penetration, the plane has to absorb the energy without a catastrophic change of moment...

[swansont]

5 hours ago, dimreepr said:

It's not just about penetration, the plane has to absorb the energy without a catastrophic change of moment...

Please show a calculation showing when this becomes a problem.

[dimreepr]

22 hours ago, swansont said:

Please show a calculation showing when this becomes a problem.

I take your point, I did a thumbnail calculation and it seems it would take a very big impact on a very small plain plane.

Edited September 13 by dimreepr

[swansont]

9 minutes ago, dimreepr said:

I take your point, I did a thumbnail calculation and it seems it would take a very big impact on a very small plain plane.

Just the fact that planes can shoot bullets without much problem should tell you that this isn’t an issue.

[dimreepr]

Just now, swansont said:

Just the fact that planes can shoot bullets without much problem should tell you that this isn’t an issue.

Indeed, that's why I said "I take your point" and why I edited my typo.

I have no idea what inspired me to post that in the first place, just a thought out of place here, sorry.

[Sensei]

Quote

Bulletproof Airplanes

What for? How often does an airplane get hit by some kind of bullet (missile?), so it has to have this kind of protection.. ?

Security for what type of aircraft? Civilian? Wartime ones?

Air fighters have catapult to rescue pilot. A pilot's life is precious. His training takes years and costs millions.

Nowadays, modern airplane-destroying missiles do not hit the body of the aircraft directly; instead, they explode close enough to the aircraft and create a cloud of shrapnel designed to cut thousands of small holes. One hole is enough to cause dehermetization and require the pilot to catapult out. shrapnel from the cloud can easily hit underslung missiles and underslung auxiliary fuel tanks and cause them to explode. A direct hit is not required.

Active protection is used to protect important aircraft - if incoming missile is detected, it throws out a cloud of shrapnel to fool the missile and hit them rather than the aircraft.

Modern turbojet engines suck in huge amounts of air to burn fuel. If any junk (shrapnel? debris?) gets into such an engine, it causes damage and the aircraft is no longer airworthy. In the case of a single-engine aircraft, it ends up catapulting the pilot.

Edited September 13 by Sensei

[John Cuthber]

On 9/12/2024 at 11:41 AM, toucana said:

A third way of making warplanes ‘bullet-proof’ during WW2 was to make them fly so fast

Interestingly the same thing would make them more vulnerable to a bullet that was simply hanging on a string.
That's how barrage balloons worked.

[LuckyR]

The A-10 is/was essentially functionally bulletproof. It first flew in 1972.

[John Cuthber]

12 hours ago, LuckyR said:

The A-10 is/was essentially functionally bulletproof. It first flew in 1972.

Just needs a bigger bullet.
https://en.wikipedia.org/wiki/Kinetic_bombardment

[LuckyR]

On 9/16/2024 at 3:16 AM, John Cuthber said:

Just needs a bigger bullet.
https://en.wikipedia.org/wiki/Kinetic_bombardment

Big bullets exist, but you've got to be able to hit the (moving) target first. Good luck with that. 

[Mordred]

Easy enough however there is another method to down a plane have enough shrapnel to chew up the jet intakes. It's a common technique to knock down missiles.

[John Cuthber]

15 hours ago, LuckyR said:

but you've got to be able to hit the (moving) target first. Good luck with that. 

Most anti-aircraft weapons are based on a lot of luck.
The ratio of bullets fired to bullets that hit is pretty big.
 

[StringJunky]

1 hour ago, John Cuthber said:

Most anti-aircraft weapons are based on a lot of luck.
The ratio of bullets fired to bullets that hit is pretty big.
 

I wonder what the hit rate is of autonomous guns in that situation.

[toucana]

2 hours ago, StringJunky said:

I wonder what the hit rate is of autonomous guns in that situation.

My father was an anti-aircraft gunner during WW2 who worked with both 3.7” HAA guns, and the fin-stabilised ‘Z-Rocket’ systems.

In general AA fire wasn’t particularly accurate. At the start of the war, Air Ministry estimates were that 6,000  shells were fired for every enemy aircraft brought down. This improved during the war to a ratio of about 1,830 shells per aircraft with the help of better fire-control, new searchlights with radar detection, and the introduction of shells with radio proximity fuzes .

https://www.reddit.com/r/AskHistorians/comments/5c9lyr/in_ww2_how_often_did_aa_guns_actually_hit_their/

The real point of AA fire in WW2 was to force enemy bombers to fly higher than they really wanted to, and avoid flying straight-line approaches on their bombing runs. If an enemy plane was flying at 200mph at  20,000 feet, it could take nearly 20 seconds for a shell to reach that height, in which time the plane would have flown another mile. AA crews had predictor machines that could help the gun-layers calculate how far ahead of the target to aim; and the longer the enemy flew in a straight line, the easier it became for the predictor. Hence the necessity for enemy pilots to fly jinking runs which made the job of their bomb aimer much harder.

[StringJunky]

26 minutes ago, toucana said:

My father was an anti-aircraft gunner during WW2 who worked with both 3.7” HAA guns, and the fin-stabilised ‘Z-Rocket’ systems.

In general AA fire wasn’t particularly accurate. At the start of the war, Air Ministry estimates were that 6,000  shells were fired for every enemy aircraft brought down. This improved during the war to a ratio of about 1,830 shells per aircraft with the help of better fire-control, new searchlights with radar detection, and the introduction of shells with radio proximity fuzes .

https://www.reddit.com/r/AskHistorians/comments/5c9lyr/in_ww2_how_often_did_aa_guns_actually_hit_their/

The real point of AA fire in WW2 was to force enemy bombers to fly higher than they really wanted to, and avoid flying straight-line approaches on their bombing runs. If an enemy plane was flying at 200mph at  20,000 feet, it could take nearly 20 seconds for a shell to reach that height, in which time the plane would have flown another mile. AA crews had predictor machines that could help the gun-layers calculate how far ahead of the target to aim; and the longer the enemy flew in a straight line, the easier it became for the predictor. Hence the necessity for enemy pilots to fly jinking runs which made the job of their bomb aimer much harder.

I was thinking with modern computerized systems doing the calcs the error rate is probably cut down a fair bit now.

[dimreepr]

10 minutes ago, StringJunky said:

I was thinking with modern computerized systems doing the calcs the error rate is probably cut down a fair bit now.

This strikes me as the predator, prey evolution... 

"Look on my works ye mighty, and despair"...

[Mordred]

1 hour ago, StringJunky said:

I was thinking with modern computerized systems doing the calcs the error rate is probably cut down a fair bit now.

Yeah missiles as opposed to bullets. 

 

[zapatos]

The Phalanx CWIS is a computerized system shooting bullets.

Quote

The Phalanx CIWS (SEE-wiz) is an automated gun-based close-in weapon system to defend military watercraft automatically against incoming threats such as aircraft, missiles, and small boats. 

https://en.wikipedia.org/wiki/Phalanx_CIWS

[LuckyR]

6 hours ago, John Cuthber said:

Most anti-aircraft weapons are based on a lot of luck.
The ratio of bullets fired to bullets that hit is pretty big.
 

Exactly, but more importantly, the targets of the A 10 don't generally warrant AA batteries let alone expensive, high tech autonomous systems.