The Galaxa Space Car can only hold one Sim at a time.
Community lot invasion is only possible with an upgrade.
Many of these are played when a certain amount of progress to The Constellations has been made.
Sleeping/resting and visiting planets increases progress towards The Constellations.
Raising your Relationship can be done by talking to them, giving them gifts and going on dates.I think I understand why purists wished to do away with spaceship mode, but for the occasional jaunt I think it was a good idea.As an educational tool it gave a good sense of relationships hard to obtain any other way (e.g., the location of the Milky Way with respect to the Magellanic clouds, Andromeda, etc.Of course, there's a downside to these many, many space sims flying out to your PC and/or Play Station 4 in the near future (although most are in alpha or beta release and are playable now): There are too many of them.Most have trading, fighting and exploring as their raison d'etre, and "procedural generation" features prominently.