This episode is a backdoor pilot for the prequel series that got canceled. Showrunner Jason Rothenberg had stated that if the series got picked up, the prequel series would have been called "The 100: Second Dawn".
This episode has neither a cold open nor a recap, instead starting straight into the title sequence. The same happened in "Pilot". Later this will also be true of the series finale The Last War (2020).
Like in Stargate (1994) and Stargate SG-1 (1997) television franchise, seven symbols are needed to dial out for interplanetary travel.