What happens at the launch pad just before takeoff?

Just before takeoff, a lot happens on the launch pad. The rocket is filled with liquid fuel and checked for leaks. Engineers run tests to make sure all systems are working—computers, engines, and safety devices. The countdown begins, and parts are armed for flight, like computers that control the rocket or covers removed from sensors. Everyone communicates by radio and reports "go for launch" if their systems look good. In the final moments, the rocket’s engines turn on and build up full power. If all is ready, clamps release the rocket, and it blasts off into the sky.​