Taking Off
One question surrounding the development and launch of rockets concerns how we get things into space. When beginning to conceptualize the physics behind rockets, consider Newton’s Third Law of Motion: “For every action, there is an equal and opposite reaction.” In other words, from the books sitting on your desk to the rockets taking off at Kennedy Space Center, both situations exhibit an action-reaction pair that guides our understanding of interactions between forces on objects.
Source: NASA/JPL-Caltech (https://spaceplace.nasa.gov/launching-into-space/en/)
Like with any problem in physics, it is vital to understand all of the forces present on an object and the interaction between these forces at different times. Propellants are burned at an enormous rate to counteract the force of gravity from the Earth. We can consider the propellant burned as thrust and the force of gravity as the total weight in the system.
Source: NASA/JPL-Caltech (https://spaceplace.nasa.gov/launching-into-space/en/)
After liftoff of the rocket from the launch pad, one might want to calculate how fast the rocket needs to go to leave the Earth’s atmosphere – this is the escape velocity. According to NASA’s Jet Propulsion Laboratory at the California Institute of Technology, multiple stages, and additional thrust, “...boosts the speed to roughly 25,000 mph and frees the spacecraft to escape from Earth orbit.”
Other physics fundamentals to consider with your calculations include Newton’s Second Law when determining the total acceleration of the rocket during liftoff. As we begin to understand how rockets leave our planet’s atmosphere, the process by which we land back on Earth adds additional complexity to this system.