1. Fight stormtroopers and look for a lift going down. At the bottom of the elevator is a locked door with two automated turrets. Destroy the turrets and open the door with a nearby control panel. Fight enemies on the other side of the door. There are two side rooms with goodies. One of them needs a security key from a nearby officer to open.
2. Behind a door is a lift going down to a long room with holodisplays and two openings sealed by force fields. At the other end of the room is a locked door. On either side is a short corridor, each ending in a locked door. Both of these corridors have a ceiling grate you can shoot, revealing ventialtion ducts that you can get into. One of the ducts leads to a small room with items. The other duct also leads to a small goodie room, but has a branch of duct that leads you to a grate in the ceiling of a sealed room. Drop down and open the door using a panel. The center of the room has a console you can use to take control of an r5 droid.
3. Assume the role of a crafty r5 droid as he goes through the door and discovers he's back in the room with the blue forcefields. The openings are just his size! Go through either of them and discover a room with guards and a panel you can use to unlock the door. You can now disengage from the droid and access the room, which also has a big elevator going down. On the other side of the forcefield you didn't take as the droid, the layout is essentially the same. It doesn't matter which of the doors you open, because they both have an elevator to take you down.
4. Either elevator goes down to a separate area which you can eventually get on a tram. Go through an unlocked door to a huge central pit, with the tram control room overlooking it. The control room doors are locked. An island in the center of the pit has a window in the floor, cleverly hidden by pipes. Drop through the window and enter an access tunnel. Follow the tunnel to an elevator which takes you up to the control room.
5. Use any or all of the panels in the control room to summon trams. You can unlock the doors to the central pit from this side, so you can easily exit the area and get onboard a tram. All trams take you to unloading areas which converge on the central communications room. The door to the comm room is locked, but easily access with a key found on a nearby officer.
6. Take either door from the comm room and arrive at the room with the 3 color-coded booths. Take the elevator down to the room of color-coded cubes. Jump around and find the panels you need for the frequency code shown in your mission status screen. Return to the central room with the 3 color-coded booths and use each panel. Go back to the comm room and you can now use the panel to send the message. After the cinematic, you can exit the level through the door by the blue-colored booth in the center room.
DOOM_DETENTION (Level 19)
1. Follow the corridor to the observation bay. Fight. Kill. Dance. An officer has a key for the elevator, which leads to a optional gunnery area where you can wear the mantle of a space turret. The corridor on the other side of the observation bay leads to the first hangar.
2. The doors to the second hangar are locked. You must enter the glass-windowed control room to open the lift in the floor. There's another panel that opens the hangar to space. There's a second control room that looks into the second hangar, which you can open to space and flush the enemies out. You also need to open the elevator in the floor of the second hanger here. Go back to the first hangar and take the elevator down.
3. Follow the corridor to a huge maintenance bay. Ride the elevator up to the walkway so you can reach a control booth. Use the control panel until the center of the three doors is open. Go around and take the elevator back down, go through the middle door, and follow the corridor. At the end is the lift which takes you up to the second hangar.
4. Exit the unlocked door and enter the third hangar. You can probably use the third hangar control room to flush the enemies out into space before you enter. Leave through the door on the other side and follow the corridor around to a room with a locked door and pipes overhead.
5. Jump onto the pipes and find a grate in the wall. Destroy the grate and go through the opening and you're now above the ceiling in the flight deck. Destroy grates or floor sections to drop down into the room and vanquish your enemies. Take the elevator down to room overlooking a smaller bay open to space.
6. Take either the left or right hallway around to the hangar bay with the imperial shuttle. The door on the left leads to the detention area. Use mind trick on the officer in the control to get the 4 security doors open. Rescue Jan and she will help you get past the security doors so the two of you can leave. She unlocks the way to the next level.
DOOM_SHIELDS (Level 20)
1. Go through the door and enter a huge round room. Follow the walkway around to the very last door. Follow the corridor beyond and take a right at the intersection. Go up some steps and enter a control room overlooking the central tower. Use the panel to extend the pipe to the tower.
2. Return to the central tower room and use the pipe to cross the chasm. Enter the tower and get the security key from the officer on the catwalk.
3. Exit the central tower room through the door directly opposite the door leading inside the tower. Take the first door on your right. Unlock the glass booth with the key, and use the panel to drain the fuel from the tower and open the four hatches.
4. Go back to the interior of the central tower and find the pipe which leads out. Follow the pipe until you find the hatch above you and open it with force push. Jump up and leave the room.
5. Leave this tall room through the other door and ride the elevator up until you come to the second level catwalk. Force jump up to the third level. An unlocked door leads to a small room with a window overlooking a droid bay. Smash through the window and drop down to the floor below.
6. To the right is a hallway leading to an elevator. Beyond the elevator is a small room with an unlocked door. The door leads to the shield generator room.
7. Defeat Galak and soon after the gravity is knocked out. Leave the room and coast to the elevator shaft, avoiding flamejet hazards. The elevator no longer works and the bottom of the shaft is electrified. Float down the shaft to the the lower floor and return to the droid bay.
8. Float up to the window where you previously broke the glass. Time it so you can pass through without getting killed.
9. Leave through the door and float down to the bottom of the really tall room with the two catwalks. Go through the open door and take a right.
10. Avoid hazards and follow the corridor to the next intersection. Take a left and return to the central tower room. Take the door opposite the entrance to the tower and follow the corridor to the exit.