Assuming that they are pulling the space shuttle straight up, and that this is done on the surface of the earth, where gravity is equal to 9.8 m/s^2. So taking the average pull force of a person to be 110 kg, then:
110 kg/person * 9.8 m/s^2 = 1078 kg*m/s^2, or 1078 N/person (Newtons).
1 Newton is about 0.225 lb. So, 1078 N/person * 0.225 lb/N = 242.34 lb/person.
So if the space shuttle weighs 4,500,000 lb, then it would take 4,500,000 lb / (242.34 lb/person) = 18,569 people.
Answer:
18,569 people