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The Crazy High Tech Reason for the SR-71s Wheels Are Silver

The Crazy High Tech Reason for the SR-71s Wheels Are Silver

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Heat was not just a problem on the ground. The SR-71 needed to deflect a large amount of heat as it flew at an average speed of Mach 3, or roughly 2000 mph!

Why are SR-71 tires silver? SR-71 tires, like the one displayed here, were infused with powdered aluminum. The addition of aluminum to the rubber gave a much higher flash point to the tire, helping it withstand the high heat caused by friction with the ground upon landing at extreme speeds. The tires were also filled with nitrogen. By inflating the tires with nitrogen, instead of air, a fire would be less likely to start due to the absence of oxygen. The tire pressure on the SR-71 was 415 psi (compared to the 32-35 psi in your automobile tires!).Each tire cost $2,300 and would last for approximately 15 full-stop landings.

Heat was not just a problem on the ground. The SR-71 needed to deflect a large amount of heat as it flew at an average speed of Mach 3, or roughly 2000 mph! At this extreme speed, the metal skin of the SR-71 would heat up to 400 degrees Fahrenheit.

In the following video, Scott Wiley, docent at the National Air and Space Museum’s Steven F. Udvar-Hazy Center in Chantilly, VA, reveals how the SR-71’s tires keep from melting.

Over 90 percent of the aircraft’s frame was made of titanium to withstand the intense heat. In addition, the SR-71 was painted with a highly sophisticated and specially formulated black paint to radiate excess heat.

The special paint also provided protection against detection by disturbing incoming radar energy, rendering the aircraft less detectable by enemy forces. An interesting side effect was the resulting changing of the speeding aircraft to a lovely blue.

Hill Aerospace Museum has one of the SR-71 tires on display.

 

This article by Dario Leone originally appeared on The Aviation Geek Club in 2019.

Image: Wikimedia.