Interstellar Movie - Conservation of Angular Momentum

[robbertypob]

OK, so I'm right in the middle of watching Interstellar and I've just seen the part where they have docked with the 'mothership' and they fire up their engines to get it to rotate. This is so they can generate a centrifugal force to simulate gravity.

My question is - first the ship was not rotating and they took action to make it rotate. How could this possibly be? Angular momentum started at 0 and was increased without any apparent external torque being applied.

Please could somebody help me out?

 

[A.T.]

How could this possibly be? Angular momentum started at 0 and was increased without any apparent external torque being applied.

Do you understand how rockets increase their linear momentum, without violating momentum conservation? Angular momentum is analogous.

 

[olgerm]

Whole system(rocket + gases, which came out of engines) angular momentum was conserved. Gases, which came out of engines got opposite angular momentum.

Just like linear momentum is conserved when rocket accelerates - gases ,which come out of engine get opposite linear momentum,so whole system linear momentum is conserved.

My question is - first the ship was not rotating and they took action to make it rotate.

Only the ship is not closed system. Closed system is ship +Gases ,which come out of engines.

 

[QuantumPion]

Even without rockets you can control a craft's rotation using gyroscopes/flywheels.