Imagine throwing any Object straight up. The Earth’s gravity would gradually slow it down and make it fall back to Earth. But if the object was thrown upward fast enough, gravity would not be able to stop it escaping into space. The minimum speed needed for this to happen is called Escape Velocity is 25,000 miles per hour. Space Rockets must accelerate to a minimum of 17,000 miles per hour to stay in orbit around Earth. They must travel faster to escape from Earth.