From FreeSpace Wiki
ship-vanish Makes the named ship vanish (no log and vanish) Single Player Only! Warning: This will cause ship exit not to be logged, so 'has-departed', etc. will not work 1: List of ship names to vanish
- This is what Volition used to make Kappa wing disappear in Mystery of the Trinity. As the SEXP description says, ships that vanish do not count as ships that depart, so has-departed-delay will not work. It can be circumvented by using a SEXP tree like this: (is-event-true-delay "Event that uses ship-vanish").
- It's also possible to ignore the usage SEXP and use a well-planned departure cue with no warp effect, and this would work most of the times, thanks to its compatibility with has-departed-delay. Ship-vanish is highly recommended, however, if a ship intended to jump out normally should vanish because of a certain event. In that case a departure cue with no warp effect won't do the trick—that's where ship-vanish comes in.