Even though the tires could last for approximately 15 full-stop landings SR-71 Blackbird tires were changed after 10 takeoffs.
During its career, the SR-71 Blackbird gathered intelligence in some of the world’s most hostile environments. The SR-71 was conceived to operate at extreme velocities, altitudes and temperatures: actually, it was the first aircraft constructed with titanium, as the friction caused by air molecules passing over its surface at Mach 2.6 would melt a conventional aluminum frame.
Its engineering was so cutting edge that even the tools to build the SR-71 needed to be designed from scratch.
There are so many interesting facts about the legendary Blackbird.
For instance, the tires of the SR-71 were silver.
Why were SR-71 tires silver?
According to the sign accompanying the SR-71 tire on display at the Kansas Cosmosphere and Space Center, Hutchinson, KS, SR-71 tires [like that featured in the photos of this article] 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 costs $2,300 and would last for approximately 15 full-stop landings.
Even though the tires could last for approximately 15 full-stop landings they were changed after 10 takeoffs, as Colonel Ken Collins, former A-12 and SR-71 pilot, explains;
‘The tires were changed after 10 “takeoffs”. The wear & tear was during takeoff. The extreme pressure was at that point of rotation. That the reason we took off with half fuel load and air-air refueled shortly after takeoff, that reduced the tire stress. The temperature in the cockpit at the front windshield got up to 650 degrees F. Early in the experimental flight testing we wore silver suits. At cruise if you touched the side canopy glass it would melt the silver coating on you glove. The coating on the suit was not “silver” metal. The cockpit and the pressure suits were air conditioned. The cockpit got hotter as you burned the fuel. You were ready to get new fuel as it would cool it down.’
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.
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.
Hill Aerospace Museum has one of the SR-71 tires on display.
In the following video, Scott Willey, 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.
Be sure to check out Linda Sheffield Miller (Col Richard (Butch) Sheffield’s daughter, Col. Sheffield was an SR-71 Reconnaissance Systems Officer) Facebook Pages Habubrats and Born into the Wilde Blue Yonder for awesome Blackbird’s photos and stories.
Photo credit: U.S. Air Force and The Unwanted Blog