How to Build a Rocket in 3 Easy Steps

A powerful Saturn V rocket launches the Apollo 11 mission toward space in 1969. Credit: NASA
So you’ve caught the latest news about Elon Musk or Jeff Bezos, or you’ve dug through the history books and discovered why Robert Goddard and Wernher von Braun were such legends, and you’ve decided you want a piece of the rocket-building action to call your own. Well, read on.

By Paul Sutter |

I should note that the following text is just a poor astrophysicist’s approach to building rockets, and obviously leaves out a lot of…well, let’s just call them „critically important details.“ Rockets are some of the most complex creations ever achieved by humanity, and it takes just a tiny bit more description to really flesh them out —my scientist hat goes off to the brave engineers who go to the trouble of actually designing and building them.

That said, rockets rely on some surprisingly simple physical principles that can be broadly applied to a variety of rocket-y situations. While the following concepts won’t exactly give you a fully fledged orbital booster engine, they will give you some idea of why we make rockets the way we do. [The History of Rockets: From Early Cultures to NASA’s Technology]

When moving on the surface of the Earth or through the air, we rely on conservation of momentum to propel us forward. When we push against the ground or flap wings against the air, the ground or air pushes back on us. Since Earth is somewhat larger than us, conservation of momentum means that we get to move a lot while the bulk of our planet barely budges.

But outer space is a different story. In that cold vacuum, there’s nothing to push against. Feet, wings, propellers and jets are useless. But, that doesn’t mean that conservation of momentum suddenly stops existing. Instead, to make forward progress we essentially have to carry our own momentum with us.

It’s the same principle that holds if you’re on an icy lake or in a rolling office chair. If you take a part of the mass that you carried with you from the beginning (a shoe, a snowball, throwing stars, whatever) and toss it away from you, you’ll move in the opposite direction. That little thing you tossed away will be smaller than you, so you won’t exactly move a lot, but you went somewhere.

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