Ameer Randolph
The SR-71 Blackbird, developed in the 1960s, is a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft. It was designed to be longer and heavier than its predecessor, the Lockheed A-12, to carry more fuel and a crew of two in tandem cockpits. The SR-71 used a specialized type of jet fuel called JP-7, which was three times more expensive than standard aviation fuel and had to be handled carefully due to its extreme temperature cycles during flight. With a thirst for 36,000-44,000 pounds (16,000-20,000 kg) of fuel per hour of flight, the SR-71 had a range of just 2,000 nautical miles when fully fueled, requiring multiple air refuelings during its missions.
| Characteristics | Values |
|---|---|
| Fuel Type | Turbine Fuel Low Volatility JP-7, also known as Jet Propellant 7 or MIL-T 38219 |
| Fuel Consumption | 36,000-44,000 pounds (16,000-20,000 kg) per hour of flight |
| Fuel Tank Capacity | 80,000 pounds or 12,000 gallons |
| Range | 2,000 nautical miles |
| Refueling | Multiple air refuelings from KC-135Q tankers during flight |
| Fuel System | Not fully sealed, no fuel-sealing system |
| Fuel Cost | Three times the cost of fuel used by airliners of the era |
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What You'll Learn
- The SR-71 used a specialised fuel called MIL-T 38219, or Jet Propellant 7 (JP-7)
- JP-7 was developed in 1955 by Clarence Brown CB Eichman
- The fuel was designed to be flash-resistant and highly thermally stable
- The SR-71 leaked JP-7 fuel on the ground prior to takeoff
- The SR-71 used approximately 36,000–44,000 pounds of fuel per hour of flight
The SR-71 used a specialised fuel called MIL-T 38219, or Jet Propellant 7 (JP-7)
The SR-71 Blackbird, developed in the 1960s, is a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft. It was designed to be faster than any missile that might be launched at it and was the fastest plane on the planet. It was also the second operational aircraft designed to be hard to spot on radar.
JP-7 is unusual in that it is not a conventional distillate fuel but is created from special blending stocks. It has a very low (<3%) concentration of highly volatile components like benzene or toluene, and almost no sulfur, oxygen, and nitrogen impurities. This gives it a low vapour pressure and high thermal oxidation stability. The fuel must operate across a wide range of temperatures, from near freezing at high altitudes to the high temperatures of the airframe and engine parts that are being cooled by it during high-speed flight. Its volatility must be low enough to make it flash-resistant at these high temperatures.
To ensure combustion, triethylborane (TEB) was injected into the engine to initiate burning and allow afterburner operation in flight. JP-7 also contains fluorocarbons to increase its lubricant properties, an oxidising agent to make it burn more efficiently, and a caesium-containing compound known as A-50, which helps to disguise the radar and infrared signatures of the aircraft.
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JP-7 was developed in 1955 by Clarence Brown CB Eichman
The SR-71 Blackbird, developed in the 1960s, is a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft. It was developed by the American aerospace company Lockheed Corporation and was the fastest plane on the planet. It was developed in secret in the late 1950s to cruise near the edge of space and outfly any missile that was launched at it. The SR-71 used approximately 36,000–44,000 pounds (16,000–20,000 kg) of fuel per hour of flight.
The SR-71 didn't use standard aviation fuel but a special military specification fuel called MIL-T 38219, or Jet Propellant 7. Shell Oil was tasked with inventing a compound blend to meet the military's requirements, and the result was three times as expensive as the type of fuel used by airliners of the era. The SR-71's fuel, JP-7, was developed in 1955 by master chemist Clarence Brown CB Eichman at Pratt and Whitney. It was initially developed for use in the CIA's Lockheed A-12 reconnaissance aircraft, and subsequently for aircraft with similar high-speed performance, including the Lockheed SR-71 Blackbird.
JP-7 is a specialized type of jet fuel with a high flash point and high thermal stability. It was designed to be used as a heat sink for the severe high-temperature environment in the aircraft. During high-speed flight, the fuel acts as a heat sink for the aircraft and engine accessories, preventing them from overheating. This requires a fuel with high thermal stability, such as JP-7, which has a very low (<3%) concentration of highly volatile components and almost no sulfur, oxygen, and nitrogen impurities. It has a low vapour pressure and high thermal oxidation stability, allowing it to operate across a wide range of temperatures.
The development of JP-7 fuel was crucial to the success of the SR-71 Blackbird. Its unique properties enabled the aircraft to achieve its remarkable speed and altitude while maintaining stability and efficiency. The collaboration between Clarence Brown CB Eichman and the CIA resulted in a fuel that met the specific demands of this advanced aircraft, contributing to its legendary performance and capabilities.
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The fuel was designed to be flash-resistant and highly thermally stable
The SR-71 Blackbird, a supersonic reconnaissance aircraft, used a special fuel called JP-7, which was designed to be flash-resistant and highly thermally stable. This was because the aircraft operated at extremely high speeds and altitudes, with a design speed of Mach 3.2 and an altitude of 85,000 ft or 26,000 m. At these speeds, very high skin temperatures occurred due to aerodynamic heating, and a new jet fuel with a high flash point was required to prevent the aircraft from combusting.
The SR-71's fuel, JP-7, is a specialized type of jet fuel developed by master chemist Clarence Brown CB Eichman in 1955 for the Central Intelligence Agency (CIA). It was first used in the CIA's Lockheed A-12 reconnaissance aircraft and was subsequently adopted for the Lockheed SR-71 Blackbird. JP-7 is composed mainly of hydrocarbons, including alkanes, cycloalkanes, alkylbenzenes, indanes/tetralins, and naphthalenes. Fluorocarbons are added to increase lubrication, and an oxidizing agent improves burn efficiency.
The fuel also contains a cesium-containing compound known as A-50, which helps to reduce the radar and infrared signatures of the exhaust plume, enhancing the aircraft's stealth capabilities. JP-7 has a very low volatility and is resistant to ignition, requiring the injection of triethylborane (TEB) to initiate combustion and enable afterburner operation. This characteristic contributed to the aircraft's safety, ensuring that the fuel would not easily ignite, even at extremely high temperatures.
The SR-71's fuel system was not sealed because no flexible and durable seals could withstand the temperature and shrinking-expansion cycles. As a result, the aircraft leaked fuel on the ground before takeoff. However, once the aircraft reached operating temperatures, the leaking stopped. The SR-71's titanium fuselage panels were also loosely fitted to the frame to allow for heat expansion.
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The SR-71 leaked JP-7 fuel on the ground prior to takeoff
The SR-71, also known as the Blackbird, was a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft developed by the American aerospace company Lockheed Corporation. It was developed in the 1960s as a black project by Lockheed's Skunk Works division. The SR-71 was designed to be longer and heavier than its predecessor, the Lockheed A-12, to carry more fuel and a crew of two in tandem cockpits.
The SR-71 used a special military specification fuel called MIL-T 38219, or Jet Propellant 7 (JP-7). This fuel was designed by Shell Oil to meet the aircraft's unique requirements and was three times more expensive than the fuel used by contemporary airliners. The SR-71's titanium fuselage panels were loosely fitted to the aircraft's frame to allow for heat expansion during flight, and as a result, the plane did not have a traditional fuel-sealing system.
Due to the lack of a fuel-sealing system and the extreme temperature cycles experienced during flight, the SR-71 leaked JP-7 fuel on the ground prior to takeoff. This was a known issue and a necessary design quality to prevent over-expansion of the aircraft's skin during flight. The fuel tanks were built into the aircraft's frame, and when the aircraft was cold, the metal contracted, causing fuel to leak out. This leakage annoyed ground crews and often left pools of fuel on the runway.
To address this issue, the SR-71 was typically refueled right after takeoff, as the leakage would stop once the aircraft warmed up to operating temperatures. Despite the leakage, the SR-71 remained the world's fastest and highest-flying operational aircraft throughout its nearly 24-year career, showcasing the success of its innovative design and engineering.
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The SR-71 used approximately 36,000–44,000 pounds of fuel per hour of flight
The SR-71 Blackbird was a retired long-range, high-altitude, Mach 3+ strategic reconnaissance aircraft developed and manufactured by the American aerospace company Lockheed Corporation. It was revealed to the public in July 1964 and entered service in the United States Air Force (USAF) in January 1966. The aircraft was designed to cruise near the edge of space and outfly any missile that was launched at it. It could enter hostile airspace, capture images, and exit before an enemy could react.
The SR-71 used a specialized type of jet fuel known as Turbine Fuel Low Volatility JP-7 or Jet Propellant 7 (JP-7). This fuel was developed by master chemist Clarence Brown CB Eichman in 1955 for the CIA's Lockheed A-12 aircraft and was subsequently used in other high-speed aircraft, including the Lockheed SR-71. JP-7 was designed to have high thermal stability, allowing it to operate across a wide range of temperatures, from freezing at high altitudes to the high temperatures of the airframe and engine parts at high speeds. Its low volatility and resistance to ignition required the use of triethylborane (TEB) for combustion initiation and afterburner operation.
Due to its advanced performance and high-speed capabilities, the SR-71 consumed a significant amount of fuel. It used approximately 36,000–44,000 pounds (16,000–20,000 kg) of fuel per hour of flight. This high fuel consumption resulted in a limited range of just 2,000 nautical miles, requiring multiple air refuelings during each flight. The specialized nature of the JP-7 fuel also contributed to the high fuel costs of the SR-71, as it was three times more expensive than the fuel used by contemporary airliners.
The SR-71's fuel system was notable for its lack of a conventional fuel-sealing mechanism. The titanium fuselage panels were loosely fitted to accommodate heat expansion, and the fuel system did not have seals durable enough to withstand the extreme temperature cycles. As a result, the aircraft often leaked fuel on the ground before takeoff, which stopped once the aircraft reached operating temperatures. This unique characteristic of the SR-71 added operational complexity and further emphasized the critical role of the specialized fuel in enabling the aircraft's extraordinary performance.
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Frequently asked questions
The SR-71 Blackbird used approximately 36,000–44,000 pounds (16,000–20,000 kg) of fuel per hour of flight.
The SR-71 Blackbird uses a specialised type of jet fuel called MIL-T 38219 or Jet Propellant 7 (JP-7).
Even fully fuelled, the SR-71 has a range of just 2,000 nautical miles.
JP-7 is a specialised fuel with high thermal stability, allowing it to operate across a wide range of temperatures. It was developed for the SR-71's Pratt & Whitney J58 engine.
The SR-71's fuel system is not sealed because no seals are flexible and durable enough to deal with the extreme temperature cycles during flight.
