Science question of the day: Why was the SR-71 Blackbird painted black?

James Snover

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When the SR-71 was was under development they had a weight problem. Even using Titanium everywhere they could, even leaving out every last possible thing that contributed nothing but added weight, they were pushing the weight limit to the very edge.

Kelly Johnson, lead engineer of Project Oxcart, got so desperate he offered his engineers, mechanics, and assembly line folks, up to a hundred dollars for every pound they could cut from the design.

In the midst of this, Johnson's right-hand man, Ben Rich, made a suggestion: paint it black. That might not sound like much, but on an aircraft that size, with the type of paint they used, it was going to add 1,100 pounds of weight. When Johnson was tearing his hair out trying to save pounds, his top guy was talking about adding 1,100 pounds in one fell swoop! Just to paint it black.

Why?
 

Smooth

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Cuz er'body knows:


black-women-over-45-blackdontcrack-31007454.png
 

GNBRETT

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Heat radiation to reduce thermal stress on the plane. Cooling benefits outweighed the disadvantage of increased weight from the paint therefore it was able to go faster.
 

Double"O"

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Black is the ideal color for a proper recon acft because it doesn't reflect light and distort the image or mess with the lenses
 

13COBRA

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Wikipedia says that it's actually a dark blue color.

Wikipedia said:
The SR-71 was designed for flight at over Mach 3 with a flight crew of two in tandem cockpits, with the pilot in the forward cockpit and the reconnaissance systems officer operating the surveillance systems and equipment from the rear cockpit, and directing navigation on the mission flight path.[22][23] The SR-71 was designed to minimize its radar cross-section, an early attempt at stealth design.[24] Finished aircraft were painted a dark blue, almost black, to increase the emission of internal heat and to act as camouflage against the night sky.

Lockheed SR-71 Blackbird - Wikipedia
 

Silverstrike

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Definitely, airframe cooling was the primary benefit...there is also some speculation the paint may have reduced the radar cross section as well.


Yes this was a little bonus when they did this on the black paint. I talked to quite a few ex Soviet SAM system operators everything from the SA-2 to the SA-10 (1971-89) and the Blackbird was one of the hardest targets to keep a constant lock on, as it would do a fade in and out, that was until you got to about 50 NM to it then if the radar was powerful enough it could maintain a lockon.

The worst position to achieve a lock on was dead astern because of the zig zag trailing edge radar deflectors the plane had back there. The only systems the Soviets had that could give a SR-71 fits was the SA-10, SA-12, and the MiG 31 with AA-9 Amos long range active guided missiles.
 

03Sssnake

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Yes this was a little bonus when they did this on the black paint. I talked to quite a few ex Soviet SAM system operators everything from the SA-2 to the SA-10 (1971-89) and the Blackbird was one of the hardest targets to keep a constant lock on, as it would do a fade in and out, that was until you got to about 50 NM to it then if the radar was powerful enough it could maintain a lockon.

The worst position to achieve a lock on was dead astern because of the zig zag trailing edge radar deflectors the plane had back there. The only systems the Soviets had that could give a SR-71 fits was the SA-10, SA-12, and the MiG 31 with AA-9 Amos long range active guided missiles.

The Mig 31 could only briefly maintain mach 3 on those intercepts...However they got their timing down and that along with the AA-9 scared us enough to start keeping our distance and eventually end the flights into Soviet airspace.
 

Gringo185

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Actually, lighter colors have better coverage than darker colors. Black would be the worst in that respect.

Interesting. My limited experience with painting is that it’s easier to cover light colors with dark than dark with light.
 

Sinister04L

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Interesting. My limited experience with painting is that it’s easier to cover light colors with dark than dark with light.

It has to do with the base used. Light colors use a white or light base which has more titanium dioxide in it which makes it more opaque. Darker colors have a more clear base that has little to no titanium dioxide.
 

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