You'd have to apply a couple hundred newton metres of torque, which would probably require a 50kg gyroscope, (expensive, heavy!) and if you want it to be at all

You'd have to apply a couple hundred newton metres of torque, which would probably require a 50kg gyroscope, (expensive, heavy!) and if you want it to be at all compact you'd have to make the reaction wheel out of tungsten. (even more expensive!)