Space · Orbits
Hohmann transfer calculator.
Pick a body and two circular orbits to get both burns, the total delta-v and the coast time.
Inputs
Transfer
Enter two orbits.
How a Hohmann transfer is worked out
A Hohmann transfer moves a spacecraft between two circular, coplanar orbits with two engine burns along an ellipse that touches both orbits. With μ = GM of the central body, the first burn is Δv1 = √(μ/r1) × (√(2r2/(r1+r2)) − 1), the second is Δv2 = √(μ/r2) × (1 − √(2r1/(r1+r2))), and the coast takes half the ellipse’s period, t = π √((r1+r2)3/(8μ)). Radii are measured from the centre of the body. GM values are the JPL DE440 figures.
Worked example. From a 300 km orbit (r = 6,678 km) to geostationary (r = 42,164 km) around Earth: Δv1 = 2.43 km/s, Δv2 = 1.47 km/s, total 3.89 km/s, coast 5.3 hours. The Wikipedia article works the same case and gets 2.42, 1.46 and 3.88 km/s; the small gap is rounding in their inputs.
Sun-centred examples give only the heliocentric burns. They ignore the pull of the departure and arrival planets, so a real Mars mission needs more than the 2.9 and 2.7 km/s shown.
Frequently asked questions
What is a Hohmann transfer orbit?
A two-burn path along an ellipse that links two circular orbits in the same plane. It is generally the most economical two-burn transfer, which is why it is the standard first estimate for moving between orbits.
How much delta-v does it take to go from low Earth orbit to geostationary orbit?
About 3.9 km/s from a 300 km orbit, split into roughly 2.4 km/s at the first burn and 1.5 km/s at the second. The Wikipedia worked example gives 3.88 km/s.
How long does a Hohmann transfer to Mars take?
About 259 days (roughly 9 months) with Earth and Mars treated as circular orbits at 149.6 and 228.0 million km from the Sun (NASA fact sheet distances). Wikipedia also gives about 9 months and notes launch windows come roughly every 26 months.
Why do real missions use more delta-v than this?
The tool assumes instant burns, perfectly circular orbits in one plane and a single central body. Real missions also climb out of a planet’s gravity well, change orbital planes and capture into orbit at the other end.
What happens if the target orbit is lower?
The transfer works the same way in reverse. Both burns are retrograde and the delta-v is the same size as going up between the same two orbits.
Sources
Checked
- NASA JPL SSD: Astrodynamic Parameters (GM values, DE440)
- Wikipedia: Hohmann transfer orbit
- NASA NSSDCA: Planetary Fact Sheet (metric)
Runs entirely in your browser. Nothing you type is sent or stored.
Scope
Education only. Instant burns, circular coplanar orbits and one central body. Not a mission-planning tool.