The surface of the pad pushes the rocket up while gravity tries to pull it down. Rocket engines work by action and reaction and push rockets forward solely by expelling their exhaust in the opposite direction at tremendous speed, and can, therefore, work in the vacuum of space. As the rocket engines are ignited, the thrust from the rocket unbalances the forces, and the rocket travels upward. Actually, rockets work more efficiently in space than in an atmosphere. Multistage rockets are proficient of attaining escape velocity from Earth and hence can achieve unlimited maximum altitude.