Category Archives: Science

Falcon 9 Re-entry … How it survives

The video below does an excellent job of explaining exactly how the Falcon 9 survives re-entry

The heat of re-entry is due to the compression of the atmosphere ahead of the re-entering vehicle, NOT air friction. Think of a diesel engine that works by highly compressing the air in the cylinder above the ignition temperature of the diesel fuel which is then injected at maximum compression and temperature.

Credit XKCD

Latest SpaceX Mission Notes

I am replaying the video for your convenience

 

Falcon 9 first stage by the numbers 

Speed of sound = 343 m/s

Max speed on ascent = 1685 m/s (Mach 4.9 @ 68 km)

Max altitude (apogee) = 166 km

Max speed on descent = 1407 m/s (Mach 4.1 @ 65km)

Stage separation (2:47) to touchdown (9:24) = 6m 37s

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Go back and rewatch the video while paying close attention to SPEED and ALTITUDE 

The Falcon 9 first stage trajectory is quite interesting …