Thermal protection coating on naval US aircraft bombs

[EOD]

After the 1967 USS Forrestal incident in the Vietnam theatre the US developed thermal protection coatings for aircraft bombs.
Also protective sleeves for nose and base fuzes were developed.

1967 USS Forrestal fire

I understand the mterials used have a high thermal resistance, a high insulation grade and likely are also deflecting heat.
While asbestos comes to mind first I wonder if this material is or ever was used and what other materials are contained.
Do development reports exist somewhere? Right now I did not succeed in finding anything propper on it.

Anybody who knows more or has a report on these coatings and sleeves?

Here an exemplary image of a MK82 with thermal protection coating on the bomb body and a sleeve on the nose fuze.

Image source: internet.

[LarryF264]

Alex, this is only conjecture on my part, but the coating appears that it might be an ablative fire retardant coating that burns sacrificially to slow the temperature rise in the bomb’s explosive. Similar coatings have been used on spacecraft for reentry.

Here is an example of a patent for such a coating: https://patents.justia.com/patent/4462831

[EOD]

Larry, thanks, I am not enough of a chemical expert in order to fully understand the idea of an incinerable protective coating.
But your remark makes the subject even more interesting!

Let us see if people with more knowledge or documentation on the subject will help us out.

[enfield56]

Alex, might it be an intumescent coating that increases in volume when subject to heat, forming an insulating layer … the word “endothermic” springs to mind … it’s used a lot architecturaly to protect structural steelwork, that would weaken dangerously if heated … but without the weight and expense of boxing the steel in or encasing it in concrete.

… just a thought.

Pete

[enfield56]

Have a peek here;

Something

W16172_Chaffois.pdf (1.7 MB)

… and this from the US Index of Specifications and Standards;

[EOD]

Peter, great doc! Thank you for sharing.
I thought of that “volume increasing foam” too and as we see the French are working with it but I wonder if it is the coatinig we see on the US bombs.
I assume back in the late 1960s the “volume increasing foam” was not yet invented. And I am almost sure that compositions in the US have changed since the first use of these.

[APFSDS]

This is all incredibly fascinting.

All these years, I always thought that these bombs I saw on the news, TV documentaries and in photos were showing a fresh coat of paint over pitted metal. LOL.

I knew that may of our modern bombs are using old WW2 era bodies repurposed with modern high tech tail assemblies that turned them kinda smart, so I always thought that were so old, and exposed to the sea for so long that the metal was pitted. SO Cool now knowing that this pitted texture I was seeing is really some kind of purposely applied coating with a special purpose. REALLY COOL!

Thanks Everyone! I feel like a lightbulb just went off in my mellon! “AH HA MOMENT!”

[EOD]

Jason, the body shape of the MK82 (and series) is very distinctive and did not exist in WW2.

I guess a pitting ob about .5" would raise serious doubts about usability on any kind of ordnance. :-)
Also bombs with 70+ years old fillers would be a bad thing to use. Many of them would not function when wanted and that also includes the “too early”.

[APFSDS]

I think the ones I so often see on the news and other sources were called, JDAMS? I was told that they were WW2 dumb bombs, that were refitted with high tech tail assembles for current use? Every time I see them load them in videos, the body assemblies look really rough and pitted. Do you think those were coated?

Jason

[EOD]

Jason, nah, never trust TV too much when they are talking about ordnance.
Some things are correct but many are not.
Also many people are not really clear in their wording, even when they know what the technical facts are.

My guess on what you saw is basically that they said “dumb bombs like in WW2” and these then fitted with guidance kits. Plus about 100 more possible explanations on things being communicated incorrectly.

Thing is that when the first guidance kits came up it was well into the Vietnam war days and by then the WW2 stuff was still used but the back then high-tech kits simply were made for the more modern bomb designs. I am excluding the few half-experimental WW2 radio guided designs (clumsy, complicated and not all that usefull).
I did not review it all now but the “oldest” bomb body the kits were made for (initially?) was the 750lbs MK117 (laser guided) and then subsequently all the MK82 / 83 / 84 alley plus some later specialized types.
Here a nice report (just checked some lines but it looked good so far):
https://www.google.de/url?sa=t&rct=j&q=&esrc=s&source=web&cd=14&cad=rja&uact=8&ved=2ahUKEwj13cvjiNnnAhVyQUEAHUwdB8YQFjANegQIBBAB&url=https%3A%2F%2Fwww.rand.org%2Fcontent%2Fdam%2Frand%2Fpubs%2Freports%2F2006%2FR1312-1.pdf&usg=AOvVaw3C8AOly08Pvuh-Zdro6cCe

I know we have some aircraft armorers here who served in Vietnam/SEA and later. Hopefully they will see the thread and chime in.

[APFSDS]

Some pics of various bombs from US aircraft on Aircraft Carriers that seem kinda pitted, but probably just coated?

Jason

[EOD]

Jason, coated ones can show oxidation too - like normal un-coated ones do (from storage in the open and in salty air at sea) but the brown rust is no pitting! Two very different things.

[APFSDS]

Thanks so much, Alex!

Jason

[bacarnal]

From experience, the coating is a rubbery substance, though I don’t know what the composition is. I do know that earlier coatings were internal and composed of a tar like material. The MK82 that had this was found on a range sweep in the 90’s. The bomb had impacted hard and cracked the casing. The desert heat had cause the “tar” to exude. Not knowing if it was HE or not, we put a charge on it. When the charge went off, the bomb went high order. We were later told about the “tar” being a thermal barrier.

[EOD]

Bruce, thanks, great to have you here.

[bacarnal]

Thanks, EOD. I’m a longtime member, just haven’t posted in a while. Cheers, Bruce.

[EOD]

Bruce, I know, and missed you here.

[bacarnal]

Thank you for that. Cheers, Bruce.

[USSubs]

If you two are done hugging it out…

We used to refer to the bombs as “alligator skin”. While we would see the M904 fuzes with thermal covers fairly often the tail fuzes were much more rarely encountered, at least by Army guys. I’ve got a poor picture of my M904 fuze with thermal cover, cropped from an out of focus shelf-shot. Best on short notice. Far right in the picture.

[bacarnal]

Awww, next time I see ya, Jeff, I’ll give you a hug;-).