 " The Arsenal of Freedom " is the 21st episode of the American science fiction television series Star Trek : The Next Generation , originally aired on April 11 , 1988 , in broadcast syndication . The teleplay was written by Richard Manning and Hans Beimler , based on a story by Beimler . The episode was directed by Les Landau . Set in the 24th century , the series follows the adventures of the crew of the starship Enterprise-D . In this episode, the Enterprise crew discovers an advanced alien race, the El-Aurian , who have built a massive space station that is capable of destroying entire solar systems