The aircraft was actively cooled[1], so I suppose they could always force a bit more cooling if needed. My guess is on engines - and not necessarily thermal lim

The aircraft was actively cooled[1], so I suppose they could always force a bit more cooling if needed. My guess is on engines - and not necessarily thermal limitation, probably rather inlet speed. Funnily enough, having read the Sled Driver[2], I don't remember any clear explainer whether the engine or the airframe was thermally limited. Perhaps it was there and I forgot by now? [edit] Wikipedia to the rescue, "Maximum flight speed was limited by the temperature of the air entering the engine compressor, which was not certified for temperatures above 800 °F (430 °C)." [3] The inlet air was necessarily heated as side effect of being slowed down to subsonic speeds, necessitated by the nature of the turbine engine. -- [1] by circulating the JP-7 fuel through critical sections, before sending it off to the engines [2] https://www.goodreads.com/book/show/1349004.Sled_Driver https://www.goodreads.com/book/show/1349004.Sled_Driver [3] https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#cite_ref-64 https://en.wikipedia.org/wiki/Lockheed_SR-71_Blackbird#cite_...