Check out our walkthrough through the hangar in Lego City: Undercover:
The hangar level I
You will walk into the control room. Walk over to the left and use the astronaut crate. You will build a teleporting device that you need to use. This will teleport you to the upper floor - destroy the telescope and the device next to it. Use the bricks to build another astronaut crate.
After you use it, you will get bricks for building color swapper gun. Change the paint in the gun and return down. The button that you have to paint is by the stairs on the left.
Now, you will have to push over the battery (the big, green element) up to the wall. The path is damaged, however. You can obtain the bricks by pulling them out of the wall, using the rope and hook. Then, you will receive dynamite that you will use to blow up the silver block below.
Ride the lift up. You now have to place three blue objects into the generator by the wall. You will notice one of them straight away, on the left - pull it out with the rope and hook and place it in the device. The second one is in the red locker on the left. The third one is next to the locker, under one of the pieces of furniture, you will find a cue that will lead you to the white drawer, where the third element is. This will make the teleporting device appear- use it and ride the transporter over to the green switch. Using it will cause a panic among the personnel. Use the chain that appeared in the center of the room and climb up to the second level.
The hangar level II
First, press the terminal button and this will make a sequence appear. You will have to repeat that sequence on the floor arrays. You will receive the color swapper gun. Fire silver paint at the array up above, on the right. It will start to reflect the beam and make the ladder appear.
Climb up. Color the golden array along your path and destroy the crate on the right. Destroy the crate before you reach the rocket, thanks to which you will receive an astronaut crate. Build another array and color it to guide the first beam from the rocket.
The second beam: destroy the crate to the right of the rocket. You will find the swapper gun there. Fire the changed color into the button above the door, on the right. Also, destroy the crates by the path. Here, you will build two arrays that, after they are colored silver, will reflect the beam into the rocket.
The lift on the right has been activated. Ride it up to the next level. Walk over to the wall across, force the door open, open the safe and use the card there on the terminal. Now, jump down to assemble the rover. Then, drive it across the door on the right.
The last activity here is avoiding the enemy vehicles for several tens of seconds, while on the rover. This should be no problem but, if it is, drive up to the hangar and park in a narrow space (e.g. behind a scaffolding/pillar).