Hohmann Transfer Orbit
The most energy efficient way between planets or other bodies in fixed orbits (e.g. lagrange points); an elliptic orbit tangent to both orbits (start and finish).

For example, in Solsys the Earth (or Cis-Lunar)-Mars Hohmann Orbit takes only about 260 (terran) days one way. Hohman transfer orbits are not suitable for cyclers, as one has to spend time on (or around) each planet, before the planets are in the right alignment again (which might be even ten thousand years).
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Development Notes
Text by Martin Andreas Cieslik
Initially published on 01 September 2003.