SR-71 – J58 Engine Airflow Design

One of the most incredible aircraft (perhaps THE most incredible aircraft) ever created was the SR-71 Blackbird. It’s the stuff of Legend, and the star of some great Internet stories, as seen here and here. But how did this incredible craft solve the issues facing engines that must operate from very low airspeeds up to Mach 3.5? The answer is through some very clever airflow management that altered not only the intake and exhaust shapes, but via a series of doors inside the engine which worked to shape and manage the airflow and sonic energy passing through the engines. Mind you, all of this was done mechanically – there was no computerization in 60s aircraft design, of course. I recently found these schematics, and they are amazing:

Also of interest is the following line drawing which makes it easier to see the offset of the inlet “spikes”, as it’s sometimes hard to accurately see given the SR-71’s black paint:


Want more like this? The ultimate reference on the SR-71 is the Lockheed SR-71 Blackbird Owners’ Workshop Manual, which is filled with technical drawings and everything you need to build your own blackbird (almost).

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