There are no easy ways to reach Robinson Crusoe Island. Small twin-engine planes fly from Santiago's Tobalaba airfield, operated by ATA and Aerocardal, taking about two and a half hours. Flights run only when the weather and load are right and cancellations are common — give yourself plenty of buffer days at either end.
The airstrip is on the dry south-west tip of the island. From there a launch crosses the open sea to San Juan Bautista in about ninety minutes, weather permitting. There is also an occasional supply ship from Valparaiso for the truly patient, which takes around 36 hours.
You will want to book everything well in advance: the island is small and seats are limited.