The Achilles 1 – Liquid Rocket Engine Passion Project Build


*Note: This article will continue to be updated as I progress through the engine build*

During the summer, I completed taking all my EdX classes and reading all the rocket science books that really interested me. I wanted to use this knowledge in a real-life application, like a passion project. I was watching some YouTube videos when I came across a video of a college student testing a small rocket engine they made. I thought that was amazing and that was something I wanted to do. And here we are…


Note: Obviously this isn’t a formal research project, so the format won’t be exactly right, but I would like to somewhat follow the format of a research paper.

  • Rocket Propulsion Elements by George P. Sutton & Oscar Biblarz (Textbook)
  • Fundamentals of Rocket Propulsion by DP Mishra (Textbook)
  • How to design, build and test small liquid-fuel rocket engines by RocketLab (Book)
  • Preliminary design of a small-scale liquid-propellant rocket engine testing platform by Erik Andersson (Master Thesis)
  • Everyday Astronaut (Youtube)

Part 1: Theoretical Design

The first part of this project is the theoretical design of the rocket engine. This part will involve the design equations used to get the engine parameters, the designing of the actual rocket engine, and the 3d modelling of the entire engine.

Starting Design Choices

Some of the design choices I made were using a 95% ethanol mixture as the fuel and gaseous oxygen as the oxidizer. I was debating between gasoline and ethanol for the fuel as they were the most readily available to me, but I learned gasoline is more dangerous so I choice ethanol. For the basic design, I used the Rocket Lab Book’s basic design as inspiration (I’ll go over details of the design later). Originally, I wanted to make an engine with about 330 Newtons of thrust and a combustion chamber pressure of 300 psi. After looking some valves to withstand that pressure, I realized that was too expensive and too dangerous. So, I redesigned the engine for a chamber pressure of 50 psi and a thrust of about 78 Newtons.

Design Equations

From the sources in the literature section, it was pretty easy to find the design equations for the different parameters of the engine. I did one set of equations by hand and another using Rocket Propulsion Analysis. They pretty much matched up. So, using these I found:

  • Oxidizer Flow Rate
  • Fuel Flow Rate
  • Pressure throughout the entire system
  • Chamber Wall & Cooling Wall Thickness
  • Cooling Gap Thickness
  • Oxidizer Injector Hole Area

Rocket Engine Design

With the parameters and an engine design inspiration in mind, I drew some rough sketches of what I wanted the engine to look like.

Part 2: Building The Engine (The Hard Part)

Now here is where this gets hard. I have to take the theoretical design and build it correctly, so it doesn’t blow up in my face. This part will include the shopping for parts, machining the separate pieces, and putting together the final product.

Update (4/11): Hey everyone, sorry for the lack of updates. The project has progressed pretty far, but I haven’t found time to update the post. Updates coming soon. I’m waiting for some parts from McMaster Carr to arrive and will hopefully test in May after AP Tests.

1 thought on “The Achilles 1 – Liquid Rocket Engine Passion Project Build”

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