re: Star Wars Episode 8: The Last Jedi Discussion Thread ***SPOILERS***

The original movie taught us two things:

1) You have to make calculations before jumping into hyperspace because hitting something in the way is bad. They already knew what would happen.

2) Ships can pilot themselves and jump into and out of hyperspace on their own. When the Millenium Falcon arrives at the Death Star and they can't find anybody on board, the officer theorizes to Vader that they abandoned ship and it just continued on its preprogrammed course. You don't even need a droid to remain behind to sacrifice itself.