We've been staring at the stars for as long as there have been human beings on this planet, but it wasn't until the 1960s when we finally managed to get there. What does it take to bring thousands of pounds of a rocket, plus its payload, into orbit? Let's take a closer look at how rockets work and what it takes to launch one successfully.
If you drop something — regardless of its size — it will drop to the ground at 5.8 meters per second squared. Air resistance may make something appear to fall more slowly, but everything on the planet falls at the same speed. That's why, in a vacuum, a bowling ball and a feather hit the ground at the same time. This is due to the gravity that our planet generates, which makes getting something off the surface and into orbit that much harder.
To reach escape velocity, which is the speed necessary to overcome the Earth's gravitational pull, a rocket needs to generate 7.2 million pounds of thrust. How can a missile generate the thrust required to make it into orbit, even a low Earth orbit like where the International Space Station hangs out?
When you launch a firework into the sky, you get a basic idea of what it takes to launch a rocket into space. All you need is fuel, oxidizer and a nozzle to direct the exhaust from the reaction. Seems pretty simple, right?
It is — if you understand rocket science. The equation to determine rocket thrust looks something like this: F = m dot * Ve + (pe - p0) * Ae
Pretty crazy, right? As the fuel and oxidizer burn, the exhaust they generate gets choked off in the neck of the nozzle, giving it only one place to go. The mass flow rate — shown here as the m dot — depends on the size of the throat of the nozzle. On Earth, you need oxygen to catalyze a reaction. That's how fireworks function — there's no oxidizer inside the firework, so it relies on oxygen from the environment around it. In space, you need to bring your own oxidizer — in this case, usually compressed air and liquid oxygen. The rocket uses an air compressor to ensure the fuel and air mix at the right rate for optimum launch conditions.
Once the engine ignites, Newton's laws of motion come into play. The second law states that when a force acts on something, it accelerates. The rocket engine firing downward makes the rocket it is attached to move upward. This is Newton's third law — action and reaction.
Our planet is constantly spinning on its axis. That's why we have night and day — the Earth rotates, and different halves of it are exposed to sunlight. At the same time, it's orbiting around the sun. Both these movements make our planet capable of supporting life, but they also make launching a rocket more difficult.
Have you ever heard the term "launch window?" This refers to the optimum time for launching a rocket for a specific mission. Since the Earth is constantly turning and moving through space, missing a launch window due to weather or mechanical failure could set a mission back months or even years while waiting for another opportunity.
Once we know where we want to go, we have to figure out the best time to launch based on the Earth's location in its orbit. If we wanted to go to Mars, for example, we'd need to launch roughly four months before our two planets will be closest together in their respective orbits. That way, we don't have to worry about missing the opportunity to land on the Red Planet, or have to wait another Martian year — 687 Earth days — for our next chance.
If you're interested in trying out some of these principles on your own, you don't need a degree in rocket science or access to liquid oxygen to try them out. Here's an easy way to make your own rocket at home from scratch with things you can find at the dollar store. There's even a recipe for homemade rocket fuel. You may already have some of the supplies in your kitchen.
If you build a rocket, let us know how it turns out. We'd love to see your attempts at creating a homemade rocket.
Megan Ray Nichols is a science writer by day & an amateur astronomer by night (at least when the weather cooperates). Megan is the editor of Schooled By Science, a blog dedicated to making science understandable to those without a science degree. She also regularly contributes to Smart Data Collective, Real Clear Science, and Industry Today. Subscribe to Schooled By Science for the latest news.