Forum:Mothership Zeta Problem

ok i just finished the Spacewalk.and i got into that room and turned on the portal to bring up all your friends. Sally opened thr first door that leads into the room where the floor is glass and you can see earth. Now the only other door in there is locked and requires a key. What key? i found out is the door that leads to the Weapons Lab and Biological Testing labs. This is only like the third time ive started the whole game over, but i have no idea. Am i just stupid?