Follow them inside and activate the ride to finish the quest. Once at least 3 cores and the distributor are placed, the Hubologists will enter the spacecraft. However, adding the fourth core will result in the death of the Hubologists.
Adding three cores, as Dara suggests, will result in a good end to the quest. Once cleared, collect the power distributor and some Fusion cores from the junkyard and go to the spaceship ride. For this Dara will reward them with the Hub's Alien Blaster. Follow the Hubologists to the Nuka-World junkyard to clear it from robots (either alone or with their help) or tell them the player character has cleared it already. Gather 5 spacesuit costumes from the Vault-Tec: Among the Stars area of the Galactic Zone and bring them to Dara Hubbell.