Constraint

“Starship will be crushingly cost-effective for Earth orbit or moon missions as soon as it’s operational & rapid reuse is happening. Mars is a lot harder, because Earth & Mars only align every 26 months, so ship reuse is limited to ~dozen times over 25 to 30 year life of ship.” - Elon Musk https://twitter.com/GailAlfarATX/status/1677896020322025477