Nulka is a type of active missile decoy developed in 2009 by a collaborative project by the Royal Australian Navy and the United States Navy. The Nulka is designed to mimic a vessel's radar signature and "seduce" an incoming missile and lure it away from its home vessel. The missile hovers in mid-air in order to fool the incoming missile into mistaking it for a slow-moving ship. The word "Nulka" is of Australian Aboriginal origin and means "be quick". The Nulka missile defense system is employed on certain warships of the Royal Australian Navy, Royal Canadian Navy, United States Coast Guard and United States Navy. In the U.S. Navy the Nulka system are installed on Nimitz-class aircraft carriers, the new Gerald R. Ford-class super-carriers which will be taking the place of the old Nimitz-class carriers and Arleigh Burke-class guided missile destroyers. They are also installed on the Australian Navy's Hobart-class air warfare destroyers and the Canadian Navy's Halifax-class guided missile frigates.
The episode's title, "Nostos", is Greek for "homecoming". In Greek literature it is used as a literary theme for a great hero returning home via the sea. The story usually involves the hero being shipwrecked or otherwise lost and having to endure some type of hardship that tests their morals and resolve and explores the hero's struggle with holding onto who they are and not loosing themselves to temptation and revenge. The best known literary example of this type of story is Homer's "The Odyssey", which is about the Greek sailor/solider Odysseus and his crew getting lost at sea for seven years while returning home from fighting in the Trojan Wars.
The song heard during the last three minutes of the episode is "Shiver My Timbers" by Tom Waits.
The pronunciation of Hydra, as "hiddra", is as it is in Greek.
The UH-1 Iroquois (Huey) depicted in this season is a US Army variant, as it has only a single engine. The standards for US Navy aviation (including the US Marines) sets a requirement for dual engine aircraft as a redundancy for engine failures. As such, the Navy/Marine Corps variants of the UH-1 are dual engine aircraft. However, that is not necessarily a goof in this season, as there was dialogue at the beginning of the season that they were essentially scavenging whatever aircraft they could, and it stands to reason that in an apocalyptic world, such issues would be easily overlooked in the search for survival.