My favorite goal in Kerbal Space Program is not the more common “return from a high gravity planet” or “orbit all the planets in the solar system in one trip” but instead “use every method including atmospheric air breaking, parachutes, and gravity assists, and mining resources /lunar/martian refueling to land a single stage rocket on mars and return”
Most fun thing to plan build and execute in the whole game IMHO
Bonus points if you bring and execute all types of science experiment available. This, and mining to refuel makes SSTO much harder.
*If you find this too easy then an upgrade is to do the same mission, but bring and deploy a permanent base to laythe (fictional moon of Jupiter with oceans). (bonus points if the base is mobile/submersible)
