Posted on behalf of Brian Smith - McGill University
The Hohmann Transfer Orbit
The transfer orbit is a maneuver that allows a spacecraft to jump from one circular orbit to another. To jump from a lower to a higher orbit it works by accelerating until the craft escapes from the lower orbit, then transfers to a new, elliptical orbit, and when it reaches the new desired altitude, it will use the rocket again to exit the ellipse and drop into a new circular orbit around the destination planet or moon. To shift from a higher to a lower orbit the steps would be reversed.
Note that the Hohmann Transfer requires two burns of the rocket engines, so that fuel consumption may become an issue. However, it can be shown that the Hohmann maneuver is the most economical method of orbital transfer in terms of fuel usage. For most of the journey the spacecraft uses the sun’s gravity to move from one planet to another.