A Deep Dive Into Rocket Engine Design

If you've been paying attention to what SpaceX has been doing recently, you'll know that they are testing both a new rocket and a new rocket engine. That engine, named the Raptor, is more than twice as powerful as the Merlin engine used in their Falcon 9 booster, and burns liquid methane instead of kerosene. That's notable for several reasons, which are explained in detail in this long article from the Everyday Astronaut. 

Fair warning: the article is moderately technical and gets into the nerdy details of rocket engine design. If you're a visual learner, there are lots of pictures, charts, and diagrams. For space nerds like me, it's absolutely fascinating. 

Here’s where we get into specifically why SpaceX sees Methane as an important, or even a necessary part of their companies future.

SpaceX’s ultimate goals are to develop a system capable of taking humans out to Mars and back over and over. The Mars atmosphere is CO2 rich, combine that with water mining from the surface and subsurface water on Mars through electrolysis and the sabatier process, the Martian atmosphere can be made into Methane fuel! So you don’t have to take all the fuel you need to get home with you. You can make it right there using Mars’ resources.

This is called in-situ resource utilization or ISRU. Now you might be thinking, well if there’s water, can’t you just make Hydrogen on the surface of Mars for your fuel? Well, yes, but one of the biggest problems with Hydrogen and long duration missions is the boiling point of Hydrogen. It takes serious considerations to maintain Hydrogen in a liquid state necessary to be a useful fuel.

So for SpaceX, methane makes a lot of sense! It’s fairly dense meaning the rockets size remains reasonable, it’s fairly efficient, it burns clean and makes for a highly reusable engine, it burns relatively cool helping expand the lifespan of an engine, which again is good for reusability, it’s cheap and easy to produce and can be easily produced on the surface of Mars

If you'd prefer a video, there's a video version of the article on their YouTube channel. I highly recommend subscribing to it; they produce some of the best space-related videos I've seen.