[Spaceships] Voyage Time Calculation with Different Drives

[schmeelke]

Unless you need high precision (e.g., a chase) or have high-acceleration propulsion, you can simplify the calculation by averaging the orbital periods of the two planets and halving the result. This assumes instantaneous velocity changes, circular orbits, and no propulsion during transit, but it's something that can be calculated easily in a few seconds with a table of orbital periods and a pocket calculator. (Minimum Energy Transfer Orbits [PDF] via NASA)