Before revision: In rocket launches For a launch of a rocket from the ground into space , dynamic pressure is: zero at lift-off, when the air density ρ is high but the vehicle's speed v = 0 zero outside the atmosphere, where the speed v is high, but the air density ρ = 0 always non-negative, given the quantities involved During the launch, the rocket speed increases but the air density decreases as the rocket rises.
After revision: In space vehicle launches For a launch of a vehicle from the ground into space , dynamic pressure is: zero at lift-off, when the air density ρ is high but the vehicle's speed v = 0 zero outside the atmosphere, where the speed v is high, but the air density ρ = 0 always non-negative, given the quantities involved During the launch, the vehicle speed increases but the air density decreases as the rocket rises.