# what happens to air in spacecraft when it accellerates

Imagine a fixed volume (fv) of air @ 1 atm stp, inside a container, in outer space, with a rocket motor on its butt. Assume the walls of the container are a perfect insulator.

What happens to the air when the motor ignites, generating 10 g of thrust, hurtling our poor excuse of a spacecraft into the depths of space.

i am imagining that at 0 g, the pressure in the fv is constant and uniform. when the motor lights off, the 10 g thrust would cause the air to compress in the direction the wall of the container nearest the motor. the pressure at the wall nearest the motor would go up, and so would its temperature while at the opposite wall the pressure would drop and so would its temperature.

Would this make-believe system, under constant accelleration, equilibrate to a constant pressure or would a pressure gradient form in the axis of acceleration. And how long would the system take equilibrate -- too fast for human perception or the pilots would notice the effects of acceleration on the atmosphere.

• There is always a gradient under acceleration. Next time you have a helium balloon in your car observe its behavior when you accelerate and decelerate. Commented Mar 6, 2017 at 5:40
• Why don't you solve this problem with constant temperature first, so you don't have to worry about convection currents? In any event, the temperature would soon become uniform. Commented Mar 6, 2017 at 12:15
• The situation is identical to that of fluid under gravity, with gravitational acceleration set equal to $-\mathbf{a}$, where $\mathbf{a}$ is the acceleration of the container.
– Deep
Commented Mar 7, 2017 at 5:10