Free Gravity Assist Speed Calculator

Estimate the maximum speed change from a gravity assist: dv_max = 2 * v_planet * sin(theta/2), where theta is the bending angle.

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Max Speed Change

18,483.77 m/s

Speed Change (km/s)18.4838 km/s

Max Speed Change vs Planet Orbital Velocity

View formula & how it works →

Gravity Assist (Slingshot) Effect

A spacecraft flying past a planet can gain or lose speed by exchanging momentum with the planet.

Maximum Speed Change

dv = 2 * v_planet * sin(theta/2)

  • *v_planet* = planet's orbital velocity around the Sun
  • *theta* = total bending angle of the flyby trajectory

    • The theoretical maximum (theta = 180 degrees) gives dv = 2 * v_planet.

    Example Calculation

    Jupiter flyby: v_planet = 13 070 m/s, bending angle = 90 degrees.

    1. 01dv = 2 * v_planet * sin(theta/2)
    2. 02dv = 2 * 13070 * sin(45 deg)
    3. 03dv = 26140 * 0.7071
    4. 04dv = 18 483 m/s = 18.48 km/s

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