It has been definitely established that a rocket can function in a vacuum as well as in an atmosphere. Thank you. Sir Isaac Newtown, 17 Century.
The exhaust gases and the rocket push against each other, causing a separation, even in a vacuum. Third Law of Thermodynamics -equal and opposite reaction.
The crepuscular rays in your cloud image support a concave Earth with inner cosmos, not a flat Earth.
Are the exhaust gases zipping out, or are the gases stationary and the rocket zipping away, or is both in equal and opposite directions? (Hint: yes it is both.)