Engineering Marvel: The SR-71 Blackbird

Sep 6, 2024

Notes on SR-71 Blackbird Lecture

Overview

  • The SR-71 Blackbird is an engineering marvel, designed for high-altitude, high-speed flight.
  • Capable of flying 26 kilometers above the surface, pilots could see the Earth's curvature and space.
  • Designed to mitigate aerodynamic friction heat, required new materials and designs.

Engine and Propulsion

  • Unique engines designed for speeds up to Mach 3.2.
  • The Pratt & Whitney J58 turbojet engine provided only 17.6% thrust for Mach 3.2.
  • Transition from turbojet to ramjet mid-flight for high-speed efficiency.
    • Uses ram pressure to operate; slows supersonic airflow before combustion.

Inlet Spike Mechanism

  • Inlet spike moves to adjust airflow and shockwave position.
  • Moves backward from Mach 1.6 to keep shockwave at ideal position.
  • Contains perforations for airflow management.

Airflow and Cooling

  • Bypass system around engine for cooling and efficiency.
  • Airflow management through shock traps and suck-in doors.
  • Crucial to maintain shockwave position to avoid un-starts.

Fuel and Range

  • Total wet wing fuel tank system used for weight savings.
  • High fuel capacity, making 59% of plane's weight.
  • Required aerial refueling for extended missions (e.g., 11.2-hour mission in 1987).

Material and Thermal Management

  • Titanium primary material for its heat resistance up to 600°C.
  • Black paint to radiate heat away according to Kirchhoff's Rule of Radiation.

Technological Limitations

  • Top speed limited by heat, despite potential to reach Mach 5.
  • JP-7 fuel used for stability and as a coolant.
  • Triethyl borane used for ignition.

Successor and Future Developments

  • SR-72 in development with high-performance composites and 3D-printed titanium.
  • Expected to reach Mach 6 as an autonomous drone.

Additional Resources

  • Mention of a documentary on CuriosityStream about the build process of the A380.
  • Promotion of educational content on Nebula.

  • Key Takeaway: The SR-71 is a testament to advanced engineering, balancing speed, altitude, and material capabilities, influencing future aerospace developments.