Question

Which of the following increases the thrust of a rocket engine?

• A. Decreasing exit area
• B. Increasing ambient pressure
• C. Increasing exhaust velocity or mass flow rate
• D. Using heavier rocket structure

Hint:

Rocket thrust increases when \[ \boxed{ \dot{m}\uparrow \quad\text{or}\quad V_e\uparrow. } \] Higher exhaust velocity produces greater momentum thrust.

Answer 1

The Correct Option is C

Step 1: Recall the rocket thrust equation. Rocket thrust is given by \[ \boxed{ F=\dot{m}V_e+\left(P_e-P_a\right)A_e, } \] where
• \(\dot{m}\) = propellant mass flow rate,
• \(V_e\) = exhaust velocity,
• \(P_e\) = nozzle exit pressure,
• \(P_a\) = ambient pressure,
• \(A_e\) = nozzle exit area.

Step 2: Identify the factors affecting thrust. From the thrust equation, \[ F\propto\dot{m}V_e. \] Therefore, increasing either the exhaust velocity or the propellant mass flow rate increases the thrust. Hence, \[ \boxed{\text{Increasing exhaust velocity or mass flow rate}} \] is the correct answer. Thus, \[ \boxed{(C)} \] is the correct answer.