Hohmann transfer orbit facts for kids

Kids Encyclopedia Facts

In orbital mechanics, a Hohmann transfer orbit moves a spacecraft between orbiting heights. It is the most fuel-efficient method to do so, because the spacecraft is not trying to escape the planet's gravity, using an elliptical orbit for the transfer.

A simulation of a Hohmann transfer orbit

A ship using this would have to apply two velocities, one to enter the elliptical orbit, and one to enter the second orbit.

Calculation
Applications
Images for kids
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Calculation

Assuming the mass of the spacecraft is much lower than that of the orbiting planet, the two velocities, $\Delta v_1$ and $\Delta v_2$ , can be solved for as: ${\displaystyle \Delta v_1 = \sqrt{\frac{M G}{r_1}} \left( \sqrt{\frac{2 r_2}{r_1+r_2}} - 1 \right),}$ ${\displaystyle \Delta v_2 = \sqrt{\frac{M G}{r_2}} \left( 1 - \sqrt{\frac{2 r_1}{r_1+r_2}}\,\,\right), }$ where

$M$ is the mass of the planet,

$G$ is the universal gravitational constant, and

$r_1$ and $r_2$ are the initial and final distances from the center of the planet.

Applications

Satellites can be moved into their proper height using a Hohmann transfer orbit.
A lunar transfer orbit (LTO) is used to reach the moon.
The Interplanetary Transport Network uses more than one body and requires lower velocity changes, and thus less fuel.

Images for kids

An example of a Hohmann transfer orbit between Earth and Mars, as used by the NASA InSight probe. InSight · Earth · Mars
Total energy balance during a Hohmann transfer between two circular orbits with first radius r_p and second radius r_a

Hohmann transfer orbit facts for kids

Contents

Calculation

Applications

Images for kids

See also