Trip to the Stars

Trip to the Stars is a side quest in the Fallout 4 add-on Nuka-World.

Detailed walkthrough
Gather 5 spacesuit costumes from the Vault-Tec: Among the Stars area of the Galactic Zone and bring them to Dara Hubbell. 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. For this Dara will reward them with the Hub's Alien Blaster.

Once cleared, collect the power distributor and some Fusion cores from the junkyard and go to the spaceship ride. Adding three cores, as Dara suggests, will result in a good end to the quest. However, adding the fourth core will result in the death of the Hubologists. Once at least 3 cores and the distributor are placed, the Hubologists will enter the spacecraft. Follow them inside and activate the ride to finish the quest.

If one chooses to not kill them, Dara gives them 100 ammo for the alien blaster and all of the Hubologists relocate to the large barn northeast of the spaceship.

5-7 fusion cores can be found in the area: If one inserts 4 fusion cores instead of 3, Dara and the rest of the Hubologists will explode on the spaceship ride. Either way, the quest will be completed.
 * In the subway car with a lantern hanging by the door. The car is at the bottom of the ramp from the spaceship. The core is on a shelf to the right as one enters.
 * Inside a large tea cup on a ledge above the aforementioned subway car, south of the spaceship.
 * In the nearby barn, there is a generator with a core.
 * In the same barn, the orange gondola car hanging in the air has a core sitting on its floor. one can simply hop into it from the above walkway which led to the power distributor.
 * In a mounted bear's mouth, in a tunnel below the central pile with some crickets, ants and landmines.
 * Possibly two fusion cores from a sentry bot patrolling the area just outside the spaceship.