Hohmann Transfer Calculator

A Hohmann transfer is an orbital maneuver that moves a spacecraft between two circular orbits using the minimum amount of propellant. It consists of two engine burns: one to enter an elliptical transfer orbit and a second to circularize at the destination orbit. The technique was first described by Walter Hohmann in 1925.

Delta-v is the change in velocity a spacecraft needs to perform a maneuver. It is the key measure of how much propellant a rocket must carry, since more delta-v means more fuel is burned. For a Hohmann transfer, the total ΔV is the sum of the two burns needed to leave the initial orbit and enter the final orbit.

The first burn (ΔV₁) accelerates the spacecraft from its initial circular orbit velocity into the transfer ellipse. The second burn (ΔV₂) circularizes the orbit at the target radius. Both are derived from the vis-viva equation using the gravitational parameter (μ) and the radii of the two orbits.

This calculator uses kilometers (km) for orbit radii. Remember that the radius is measured from the center of the central body, not from its surface. For a 400 km altitude orbit above Earth (radius ≈ 6,371 km), you would enter 6,771 km as the orbit radius.

Yes — simply select Mars or Moon from the central body dropdown. Each body has its own gravitational parameter (μ). You can also select 'Custom μ' and enter any value to calculate transfers around other planets, moons, or fictional bodies.

The Hohmann transfer is the most efficient two-burn transfer between two coplanar circular orbits. However, for very large orbit ratio differences (roughly greater than 11.94), a bi-elliptic transfer becomes more efficient. Plane changes and inclination corrections add additional delta-v not captured in this calculator.

The transfer ellipse is an elliptical orbit whose periapsis is at the initial orbit radius and whose apoapsis is at the final orbit radius. Its semi-major axis is simply (r₁ + r₂) / 2. This value determines the shape of the transfer trajectory and the time it takes to complete.

The transfer time equals half the orbital period of the transfer ellipse. It is computed as π × √(a³ / μ), where a is the semi-major axis of the transfer orbit and μ is the gravitational parameter of the central body. This gives the time from the first burn to the second burn in seconds, which the calculator converts to hours.