# Change a Spacecraft's attitude from 3 - axis stabilised to spin stabilised?

I am essentially trying to "spin up" a s/c, so it spins about 1 axis at a known spin - rate. I then need to figure out how much time it will take to do that, and how much force required (which I imagine is a function of time). Am I correct in assuming the torque needed is M = Iw, where I is the moment of inertia of that axis, and w is the spin rate? From there, I am not sure how to calculate the time. Any help would be massively appreciated.

Best, Harvey