To transport the nuclear containers, you have to activate the gravity field generator of the satellite by clicking on it. Once it is activated, you do not need to stay with your finger over the satellite. When you remove your finger from the Display, the gravity field generator is deactivated again, but don't forget the nuclear war head. It is also active while the gravity field generator is on. Do not steer the container into an active satellite, or the nuclear warhead will explode.