Hohmann transfer orbit
An orbital maneuver using two burns to transfer between orbits.
The Hohmann transfer orbit is an orbital maneuver used to transfer a spacecraft between two orbits of different altitudes around a central body. It is accomplished by placing the craft into an elliptical transfer orbit that is tangential to both the initial and target orbits, using two impulsive engine burns. The maneuver often uses the lowest possible amount of impulse to accomplish the transfer, but requires a relatively longer travel time than higher-impulse transfers.
- named_after
- Walter Hohmann
- field
- Astronautics
- known_for
- Hohmann transfer orbit
- publication
- Die Erreichbarkeit der Himmelskörper (The Attainability of Celestial Bodies)
Lore & Background
When used for traveling between celestial bodies, a Hohmann transfer orbit requires that the starting and destination points be at particular locations in their orbits relative to each other, which opens a launch window.
Reader's Guide
The Hohmann transfer orbit is a foundational concept in astronautics, enabling efficient transfers between circular, coplanar orbits around a central body. Its significance lies in its fuel efficiency, using the lowest possible impulse for such transfers, though it requires longer travel times. For missions like Earth to Mars, launch windows occur every 26 months with a travel time of about 9 months. The maneuver's reversibility allows it to be used for both raising and lowering orbits, with burns labeled periapsis and apoapsis burns. While highly efficient, low-energy transfers that account for real engine thrust limitations and gravity wells can be even more fuel efficient in some cases.
Did You Know?
- The Hohmann transfer orbit uses two impulsive engine burns: the first establishes the transfer orbit, and the second adjusts the orbit to match the target.
- For an Earth-Mars journey, the Hohmann transfer orbit requires a travel time of about 9 months.
- A Hohmann transfer orbit can be used to bring an asteroid orbiting the Sun into contact with Earth.
Frequently Asked Questions
What does the Hohmann transfer orbit actually do?
It moves a spacecraft from one circular orbit to another of a different altitude using exactly two impulsive engine burns. The craft rides an elliptical path that is tangent to both the starting and destination orbits.
How does the Hohmann transfer orbit sequence end?
The maneuver concludes with a second burn at the far end of the elliptical transfer path, circularizing the craft into the target orbit. At that point the spacecraft is fully committed to the new altitude and the transfer is complete.
Why is the Hohmann transfer orbit considered important in celestial mechanics?
It achieves the inter-orbit transfer with the lowest total impulse of any two-burn strategy, making it the most fuel-efficient standard option available. That efficiency is why it remains the default planning tool for mission designers.
What is the main drawback of using a Hohmann transfer orbit?
Because it trades impulse for time, the transfer lasts roughly half an orbital period of the ellipse, which can be considerably longer than a direct higher-thrust trajectory. Missions with tight timelines may therefore prefer a more energetic, multi-burn alternative.
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