Project Fireball

Due to the rapid process of iteration, this page may sometimes be unfinished. Updates on the progress I make may be delayed, and school may get in the way of updating this website.

This is Project Fireball, a home-built rocket engine designed to be cheap and easily manufacturable. The goal of building Fireball is to learn as much as I can about rocket engines, basic fluid systems, and new forms of manufacturing. This engine will take on an unusual approach by using a resin printed injector and a 3D printed nozzle. It might seem silly to make these two components out of plastic given that they experience some of the highest temperatures in a rocket engine. However, they're also the hardest to manufacture. It will be interesting to see how the 3D printed parts hold up. Fireball's goal is to survive a 3 second burn; perfect for an engine this size.

Section View of Fireball

Iteration 1

Goals

The goal of this first iteration is to prove that a 3D printed injector and nozzle can survive a short duration burn.
It will be designed to be as cheap as possible to encourage quick iteration.
I want to see shock diamonds!!!! Shock diamonds indicate supersonic flow and non-negligible thrust.

First iteration test stand for Fireball

Test Stand Design

This system is designed to be as simple as possible to minimize failure points. It has a single input which is operated by a valve. Compressed air is connected to the input which pressurizes the tank. Using the brass tee, it also provides compressed air as the oxidizer to the engine. When the valve is closed, the tank is not pressurized, and there is no flow of oxygen to the engine. Once the valve is open, the tank is pressurized allowing fuel and oxidizer to flow into the engine at high pressure.

The tank itself is made out of 3" SCH 40 PVC pipe. With this this tank, a maximum pressure of 260 PSI is achievable, however the first pressure tests and hot fires will be conducted at 150 PSI for safety. The bottom cap is bonded permanently while the top cap uses a threaded cap to easily allow the tank to be filled and inspected.

The engine will be mounted horizontally to allow for easy ignition. A sparkler or fuse can be slotted into the throat of the nozzle to ignite the engine easily, and burn any unwanted fuel in the chamber to avoid hard starts.

Testing Procedures

Tank Pressure Testing

Before any hot fires can be conducted, the tank has to be safely tested beyond operating pressure. A lot of the danger with pressure testing can be avoided by using water to fill the tank. Since it is incompressible, a tank failure would not result in an explosion as it would using compressed air.

Cold Flow Testing

Once the tank can reliably operate at high pressures, a cold flow test can be conducted. This test flows high-pressure water through the engine instead of fuel to safely evaluate the fluid system. Leaks can be identified, pressures can be verified, and the flow through the injector can be inspected. Since alcohol has very similar properties to water, this test is very useful.

Wet Dress Rehearsal

Very similar to cold flow testing, a wet dress rehearsal will follow through all of the steps of a hot fire, without actually firing the engine. These tests are carried out to verify that testing procedures occur safely and smoothly. Most companies in the industry conduct wet dress rehearsal tests with fuel and oxidizer. However, I will just use water since it is similar enough to alcohol and is much safer.

Hot Fire!

Once I am comfortable with the steps to conducting a safe engine hot fire, it's time to make some flames! The tank will be filled with roughly a liter of 99% isopropyl alcohol, and the air compressor will pressurize the system to 150 PSI. A magnesium sparkler will be placed in the engine, and the valve will be opened! I will have lots of cameras rolling to capture the moment, including a highspeed camera to help identify any issues that may occur. For these initial tests, no thrust measurements will be taken; I want to build a reliable system that I am comfortable with before making the system more complex by adding sensors and electronics.

Updates!

January 2023

As of January 15, 2023:

The tank was tested up to 125 PSI several times allowing me to move forward with testing
The injector was printed, and a cold flow test was run on the injector.
- - Unfortunately, there was resin left inside the injector orifices during the curing process which resulted in the injector not producing the correct flow
The injector was redesigned to fix the printing issue, and 2/3 of the material was removed to make 3D printing cheaper. The new design should be easier to print, and uses only 1/3 of the resin from the previous design.

Old injector (left) vs new injector (right)

As of January 11, 2023:

The tank has been fully assembled and tested up to 30 PSI. A high pressure test will be conducted tomorrow (1/12). Pictures will be posted by the end of the week.

As for the engine, the injector has to be resin printed. This can hopefully be done by 1/13. Once the injector is printed, the engine can be assembled in roughly 5 minutes.

If the pressure test goes well, and the injector can be printed by 1/13, a cold flow test could happen as soon as 1/14. I'm looking forward testing the system soon!

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