Just leave the game running in any of the front-end menus, and the game will eventually crash with an OutOfMemoryError.
It happens regardless of whether Starsector is maximised or minimised.
On my machine, with default heap space, it takes about 30 minutes of idling before encountering the crash.
1571863 [Thread-5] ERROR com.fs.starfarer.combat.O0OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO - java.lang.OutOfMemoryError: Java heap space
java.lang.OutOfMemoryError: Java heap space
at com.fs.starfarer.combat.o0OO.super.<init>(Unknown Source)
at com.fs.starfarer.combat.o0OO.B.o00000(Unknown Source)
at com.fs.starfarer.combat.CombatEngine.advance(Unknown Source)
at com.fs.starfarer.title.OoOO.o00000(Unknown Source)
at com.fs.starfarer.B.ØÓÒ000(Unknown Source)
at com.fs.oOOO.A.Ò00000(Unknown Source)
at com.fs.starfarer.combat.O0OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO.o00000(Unknown Source)
at com.fs.starfarer.StarfarerLauncher$2.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)