2011 Issue

58 A key to this balance of power includes our ability to see their weapons. The SR-71 was a critical solution. At its speed (Mach 3.0+) and altitude (80,000+ ft), it was impervious to enemy fire. The SR-71 remains the fastest manned air-breathing vehicle ever to fly on this planet. The SR-71 tops the chart at around 3.2 Mach or around 2200 miles per hour. Anything faster has to be a space vehicle or an unmanned hypersonic. And those are still in the experimental stages. Speed means heat. And at SR-71 speeds, normal jet fuel would self-ignite, dooming any aircraft that attempted that speed. Special fuel was created. It was called JP-7 . Various unverified (but reasonable enough to make the point) sources on the Internet provide some estimated engineering challenges: The forward cockpit canopy on the inside could be as hot as 250 degrees F. The crew during emergency ejection could experience 450 degrees F. The leading edge of the wing might experience 800 degrees F. To put this in perspective, a typical jet engine exhaust nozzle experiences 1500 degrees F. The SR-71 wiring was rated to 900 degrees F. The typical jet fuel of the time, JP-4 (a mixture of kerosene and gasoline), would auto-ignite at 450 degrees F. It is estimated that JP-7 would not auto-ignite even at 1000 degrees F. A story to illustrate: A KC-135Q sustained a ground accident when ground equipment impacted a fully fueled aircraft at the nose wheel. This started a hydraulic fire which began to consume the nose of the aircraft. This weakened the forward structure and caused the forward body tank to rupture, releasing the JP-7 onto the fire – extinguishing the blaze. The KC-135Q had the ability to segregate its fuel from the SR- 71’s JP-7. We could burn the JP-7, but we could not start our engines with it. To light the SR-71 engines, triethylborane (TEB) is injected. TEB explodes on contact with air. For a photo of an SR-71 engine start see www. saunalahti.fi/fta/sr71b2. We sometimes needed to carry a barrel of TEB in the back of the KC-135Q. Unloading after one of our missions, an accident occurred. An airman died when the explosion took off the top of his head. No sealant could be devised to withstand the temperatures so this meant that the SR-71 leaked constantly until it reached cruising speeds and the plates of titanium expanded enough to seal the fuel in. Unless the SR-71 “hit a tanker” immediately after take-off, the only option was an immediate return to the airfield. Once the Blackbird was “topped off” and accelerated, the titanium skin would expand and seal any leaks. Refueling in flight is inherently dangerous. Two aircraft in close vertical proximity want to impact each other. With radio-silent, high priority SR-71 missions the danger increases. I once refueled in a traffic pattern in a thunderstorm, passing all our fuel to the disabled SR-71. We landed on fumes and the SR-71 was able to finally deploy its landing gear and also land safely. Since the missions were so critical to national security, we would fly our tankers in formation to guarantee an adequate off-load of fuel. The KC-135Q pilots were the only tanker pilots at the time flying our unique “nearly abreast” formation. We stayed safe and successfully performed themission time after time by being very, very good at what we did. Unfortunately, I still lost some friends to aircraft accidents. The SR-71 was in service from 1964 to 1999. In 1944, in an ar- ticle about the “kitchen of the future”, Associated Press writer, Dorothy Roe, captured the spirit of this first post-war year with a little poem called “After the War.” (poem and advertisement from www.paleofuture.com ) After the war . . . We’ll just a press a button for food or for drink, For washing the dishes or cleaning the sink. We’ll ride in a rocket instead of a car. And life will be streamlined . . . After the war. Well, in 1980, we did not have our own private jet packs nor could we ride in a rocket instead of a car. But life was streamlined and we did rule the skies of the entire world with the SR-71 … after the war. Mr. Vono is a retired USAF colonel and a technical manager for a major defense contractor. He has a B.S. in Astronautical Engineering from the USAF Academy, an M.S. in Systems Management from the University of Southern California, and an M.S. in Mechanical Engineering from USU. Figure 2: SR-71 Speed Graph Vono