A couple of friends and I went to the Steven F. Udvar-Hazy Center, part of the National Air & Space Museum near Dulles Airport, a few weeks ago. The museum is home to over 160 aircraft, almost as many spacecraft and missiles, and several thousand smaller aviation-related artifacts. What is perhaps most exciting object on display, though, is the one that greets visitors as they first enter the museum -- the SR-71 Blackbird.
The Blackbird was developed by Lockheed Martin's division for secretive projects called Skunk Works. It was designed to replace another stealth aircraft developed by Lockheed Martin's Skunk Works -- the U-2 . The U-2 was created as a high-altitude reconnaissance aircraft (a spy plane) but it was not capable of flying supersonically, or faster than the speed of sound, making it vulnerable to anti-aircraft weapons. The Blackbird can fly above 82,000 ft. (15 and a half miles) and up to speeds of Mach 3.2, or around 2,400 mph.
Developing a high-flying, supersonic airplane came with one giant problem: Heat. As a supersonic airplane flies faster and faster, the friction from air ramming it results in a lot of heat building up around the airplane. To keep it flying functionally, the designers had to find clever ways to keep the Blackbird cool.
When the airplane was traveling supersonically, the fuel was also used as part of a heat sink. A heat sink is a device that uses a fluid to wick away heat from a solid object. The Blackbird's manual states that without that heat sinking capability, parts of the airplane and its engines would overheat at high Mach speeds.
GlobalSecurity.org, the Federal Aviation Administration could track the Blackbird from several hundred miles away by detecting the airplane's exhaust.
The Blackbird had another quirky heat-thwarting feature: It leaked fuel. According to Lockheed Martin, 93 percent of the airplane is made of titanium alloy. Titanium expands as it is heated. To keep the airplane from crunching up like a soda can when it was flying at high speeds, the designers left gaps between its body panels. Consequently, fuel, stored in the airplane's body, leaked out onto the runway before take off. Once airborne and warmed up by friction, the titanium would expand, the gaps would seal and the Blackbird would be refueled before leaving on its mission.
Skunk Works improved upon the Blackbird when it created the F-117 Nighthawk, their first truly stealth airplane. They also collaborated with Boeing to develop the more conventional-looking F-22 Raptor stealth fighter. And who knows what else is up Skunk Works' sleeve these days. Regardless of what it is, I doubt it could ever have the unique personality of its early predecessor - the SR-71 Blackbird.