Introduction: 3D Printed Rocket Engine (CGT)

A Cold Gas Thruster is an important part in space crafts. It a small rocket engine, usually mono-propellant, that is used to steer the space craft or a satellite. As a hobbyist in rocketry or additive manufacturing, making a CGT yourself can be very exciting; nevertheless it's a rocket engine!

Building a mono-propellant engine will give you enough playground to move onto bi-propellant engines. The goal of this experiment is to make the engine as simple, affordable and easy to manufacture.

There are quite a few parts involved and I've mentioned them in their respective sections. Make sure you read the entire article as some important points are mentioned at the end.

Watch the engine fired here:

I've also built an aerospike nozzle:

Step 1: Mounting the Engine and Plumbing.

These are the parts you need for the feed system.

1) A small section of durable plastic pipe with dimensions: 6mm OD and 1mm wall thickness.

2) Two connectors: 1/4 BSP threads on one side and push fit (6mm) on the other.

3) Nipple connector: for attaching the assembly to the oxygen gas hose.

4) A custom connector for connecting the nipple connector and 1/4 BSP.

5) 1/4th inch solenoid valve (12V)

Screw on the engine on the connector without the nipple connector. Push the pipes into the other sides of the connectors and push the empty ends into the solenoid valve. mount the assembly on the mount provided. The arrangement should look similar to the on in the image.

Step 2: Connections for Electronics

You will need the following electronic components.

1) Arduino Uno (or any other suitable model)

2) Transistor IRF520

3) Diode IN4007

4) Resistors 330 Ohm, 2.2 kOhm

5) Jumper Cables

6) 12V adapter

Follow the diagram shown and make the connections. The shown is from the data sheet of the solenoid valve. A 12V solenoid valve will hold just fine. You can go a step ahead and purchase the one with brass attachments. Upload the provided code to control the solenoid. Feel free to play around with the time delay.

Step 3: Final Assembly and Check

The final assembly should look like this. Make sure that your electronics are at a certain distance from the engine; to avoid any damage. The power supply should be stable and safe as the solenoid can draw a lot of current. The electronic connections made is a safety circuit for the solenoid. You can hold the engine assembly in a bench vice. Plug the oxygen hose into the nipple connector.

Double check that everything is in place properly. Run the code for operating the solenoid valve before connecting the oxygen supply. Make sure it is working properly.

The engine is designed for 120 psi chamber pressure. However, in the tests I conducted, it held fine up to 155 psi. Please start with 120 psi only. Once satisfied and proper safety is taken, you can experiment by increasing the pressure. Once fired, you will not be able to see the oxygen coming out of the engine. You can add a few drops of water in the nozzle and with the right conditions, you can see the gaseous products streaming out! With courtesy of Copenhagen Suborbitals, I found out that the engine works best with compressed air and few drops of water.

Step 4: Files and NOTE

Please remember that this project is for education purposes. Although a small engine, it is a rocket engine and you are dealing with high pressures. SAFETY is important. If you are an amateur, make sure you take help and are supervised.

This project is made public in a motive for 'space for everyone' and to encourage people to move towards liquid propellant rocket engines. Now, this is just a ground test of the engine. But if you have the proper infrastructure, you can build a small mono-propellant liquid fueled rocket. I personally advise to enjoy the ground test of the engine, instead of building a rocket out of this.

Let me know if any files are not working or if any further help is needed.