3 ms·

Didn't SR-71's also leak fuel when on the ground?

• masklinn 6y ago
  Yes but that's a separate concern. The engines were not efficient at slow speed / ground levels even ignoring the "leaks until it gets hot enough to seal the pipes" issue, the blackbird was designed to hit peak efficiency above Mach 3 (generally speaking all jets are designed to hit peak efficiency at their cruising speed, and the blackbird was designed for a cruising altitude of mach 3.2).
• imtringued 6y ago
  That's only because they decided to not use tanks inside the wings. The wings themselves contained the fuel. You can certainly build a non leaking SR-71 if a higher weight is acceptable.
  • masklinn 6y ago
    > That's only because they decided to not use tanks inside the wings. It's not only that. It's because they didn't have alloys which would handle the thermal constraints without significant expansion, so they had to design for that expansion. And in the same way rail tracks handle expansion by leaving gaps, that's what they did. Furthermore, due to limited room and systems able to handle the temperature gradients, the fuel acted not just as fuel but also coolant, heat sink and even hydraulic fluid for some propulsion components (e.g. the afterburner nozzles and inlet guide vanes used JP7 as hydraulic fluid).