Rocket Thrust Calculator

What Is Rocket Thrust?

Rocket thrust is the net force produced by expelling mass at high velocity. Newton's third law governs the momentum contribution, while pressure differences at the nozzle exit add an additional term.

Rocket Thrust Formula

$$F = v_e \frac{dm}{dt} + A_e (P_e - P_{\text{amb}})$$

$v_e$ is effective exhaust velocity, $\dot{m}$ is mass flow rate, $A_e$ is nozzle exit area, $P_e$ is exit pressure, and $P_{\text{amb}}$ is ambient pressure. Mass flow rate can also be found from expelled mass and burn time: $\dot{m} = \Delta m / \Delta t$.

Example: Merlin 1D Engine

With $v_e = 3000$ m/s, $\dot{m} = 273.6$ kg/s, $A_e = 1.23$ m², $P_e = 84{,}424$ Pa, and sea-level ambient pressure of 101,325 Pa, total thrust is about 800 kN.

Frequently Asked Questions

What is effective exhaust velocity?

Effective exhaust velocity (v_e) is the speed at which propellant leaves the nozzle when ambient and exit pressures are equal. It relates to specific impulse: v_e = I_sp × g.

Why does thrust increase at altitude?

Ambient pressure drops with altitude, so the pressure term A_e(P_e − P_amb) becomes less negative, increasing net thrust.

How do I find mass flow rate?

Divide expelled mass by burn time: ṁ = Δm/Δt. For example, 44,320 kg over 162 s gives about 273.6 kg/s.

What units should I use?

Use SI units: m/s for velocity, kg/s for mass flow, m² for area, and Pa for pressure. Thrust is in newtons (N).

Can this formula apply to jet engines?

Yes. The thrust equation applies to any jet or rocket engine that expels mass to produce propulsion.

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Rocket Thrust Calculator

What Is Rocket Thrust?

Rocket Thrust Formula

Example: Merlin 1D Engine

Frequently Asked Questions

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