📘 Definition
Max-Q (maximum dynamic pressure) is the moment during ascent when the product of air density and vehicle velocity squared reaches its peak. Early in flight the rocket is slow but the atmosphere is dense; high up it's fast but the air is thin. The maximum occurs in between — typically 60–80 seconds after liftoff at 11–14 km altitude, with pressures around 30–40 kPa. Falcon 9 throttles its Merlin engines down to 80% thrust approaching max-Q to reduce structural loading, then throttles back up once through the peak. The payload fairing must withstand max-Q aerodynamic and acoustic loads.
60–80 seconds after launch
Timing
11–14 km
Altitude
30–40 kPa typical
Pressure
Throttle down to 80%
Falcon 9 Response