sugas182

Mr. Szczepanik. Thank you, all of you, for your service and for enriching the lives of us aviation buffs with stories of the Sled.

As the man in the back seat, how did it feel when the aircraft had an unstart?

Also, were crews assigned to just one aircraft for their career, and if so, which tail number did you fly on?

Okay so the SR-71 had a variable inlet of sorts for its engine. A movable nose cone and doors around the front of the engine nacelle. here's a picture of it from a model I made

Engines generally cannot handle air coming into them at supersonic speeds, so the air needs to be slowed down. So the faster the air, the quicker it needs to be slowed down. And this is where the shape of the intake is absolutely critical. If it's off by a little bit, you'll get a standing wave, or shock wave.

Back to the SR-71. The movable inlet cones served this purpose; to slow the air properly for the engine to use it. Thing is, they had to be manually moved and timed correctly. An unstart was basically the standing shockwave that was caused by the cone not being moved forward correctly. It was more common than you think on the blackbird- very scary, but not really fatal, given the experience of the pilots.

I'm sure Mr. Russell could give it in better terms but that's how I understand it.

Source: Aero grad student and I love the SR-71.

Fun fact: above mach 2, the air was diverted around the main turbojet engine and directly mixed with the fuel and ignited because of its speed and temperature. A ramjet of sorts, I think but don't quote me on that.

EDIT: Very funny guys.