Spark Torch Igniter

Introduction

Having built my liquid-fueled rocket engine, the X1000F-3, I had always intended to ignite it with a solid cartridge, like Copenhagen Suborbitals and others do. This has the simplicity of being very easy but makes multiple engine restarts slow and cumbersome, having to safe the test stand each time in order to reload another igniter cartridge.
However, since becoming a student, time nor funds are on my side to bring my engine to life anytime soon, so I needed an interim project, henceforth a spark torch igniter.

Aim

  1. Develop an igniter for the X1000F-3 rocket engine.
  2. Gain more experience with coding and electronics design.
  3. Keep myself sane while studying a mechanical engineering degree.

Although this is not the first time I have made such an igniter, I have tried in the past with varying success rates, but it is only now that I have the time and patience to sit down and really nut it out. Plus it makes good study procrastination!.

Design

Having limited tooling and facilities, I decided to take the approach of a 3D printed igniter to make it as easy as possible. Shapeways do a bronze infused stainless steel which is heat resistant to 841°C (1114K) and well within the budget of a student such as myself. The choice of this material does require the igniter to be run fuel rich to keep the combustion temperature down as much as possible.

3D printed mockup in PLA.
Initial CAD of igniter

As this was going to be the first thing that I was going to have printed in metal I opted for an initial print in PLA. This allowed me to check threads, fits, and clearances etc. This proved very beneficial as some slight modifications of the original CAD design were needed. 1/8″ BSP threads were selected for the female fitting attachments and a 1/4-32 model airplane sparkplug for the spark.

The igniter is designed to run on a 75/25 Ethanol/water mix and gaseous oxygen and operate at a chamber pressure of 70psig. The choice of the fuel is the same as the X1000F-3.

Performance Specifications

Being the first iteration of 3D printed igniters, performance was low on the agenda, obtaining a reliable system and igniter were first and foremost.

  • Design total mass flow rate: 0.0099kg/s (0.5% of X1000F-3 mass flow rate)
  • Thrust (Calculated): 9.36N
  • Design chamber temperature: 992K
  • Design ISP: 96.38

Hardware

  • Arduino Uno
  • Arduino screw shield
  • 5V 4-channel relay module
  • x2 HP Solenoid valves
  • x3 1000psi pressure transducers (Aliexpress)
  • Rcexl CDI  electronic ignition box (1/4-32 plug)
  • Rcexl ignition test kit
  • Converted fire extinguisher

Control was initially through the Arduino serial monitor with command prompts, but my brother kindly spent some time in Visual Studio and made a GUI to enable control and have real time plotting. The GUI also produces a csv file with data for the duration of the preprogrammed auto sequence start loop, which can be analysed at a later date.

Igniter GUI produced by my brother for the project.

Testing

Coming soon!!