Space Nerds in Space is a free/open source team game where players take on the roles of Navigation, Weapons, Engineering, Communications, Damage Control and work their controls to safely land a spaceship on a variety of planets, each with their own challenge -- and once your team is practiced, you can use a multi-team server to compete against other teams, NPCs, and even engage in multi-team, player-to-player combat.
The game is inspired by the Artemis simulator, which, in turn, is part of a lineage dominated by Spaceteam, a co-op spaceship game that has spawned a whole ecosystem of fun and ambitious variants (up to and including the Millennium Falcon ride at Disneyland's Star Wars-themed Galaxy's Edge).
It's clearly an ambitious and well-thought-through game, and the free/open nature of the code has created a constellation of add-ons, scripts and improvements that let you go very deep.
S P A C E N E R D S I N S P A C E [Steve Cameron/Github]