S1: 15% of power t = 20 s
S2: 20% of power t = 15 s
S2: 30% of power t = 10 s
S3: 35% of power t = 5 s
S3: 40% of power t =5 s
S3: 45% of power t = 5 s
S4: 50% of power t = 5 s