To Ignite the Rocket Engine in Charlie Montegue’s Game in Updaam in Deathloop you need to put a battery in all 5 slots inside of the rocket.

All the lights will turn green once you have inserted all the required batteries, you can find batteries all over the place such as on the floor near the moving wooden cutouts that are scattered throughout the building.

Then, go up to one of the locked security doors at the back of the base complex level and use the hackamajig to hack the antenna above the door to open up.

Walk up to 2-Bit and select the ignite rocket engine option.