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The Hunt for the Best Igniter

The Hunt for the Best Igniter

So, rockets burn fuel. That much makes sense. And that combustion of cold liquid creates a lot of hot, pressurized gas that makes the rocket go upwards. Got it. But how does that begin?

You can’t light a kitchen stove without the internal igniter sparking. In the forest, you can’t start a campfire without flint and steel. (Or lighter fluid and a barbecue lighter.) But inside a rocket engine… things are a little more complicated. Castle Point Rocketry has been upending shelves worth of books (all online, don’t worry) searching for the question on the forefront of our minds: “How do we start our engines?” And we’ve narrowed it down to three major contestants.

“The Cotton Ball”

  1. Soak a cotton ball (or other highly-porous material) in something really flammable.
  2. Stick said drenched cotton ball on the end of a metal stick.
  3. Set rocket over stick, with cotton ball inside combustion chamber.
  4. Light cotton ball on fire.
  5. Release the fuel and LOX.
Proof of concept: It’s been done before.

Potential drawbacks include the sudden onslaught of liquid, though flammable, extinguishing the burning cotton ball.

“The Salt Crystal”

  1. Finish researching oxidizing rock salts. Some salts, when heated, spontaneously burst into flames and release copious amounts of oxygen — which helps fuel more decomposition.
  2. Acquire a small-ish amount of the chosen salt.
  3. Carefully pack the salt into a small container on the end of a large stick.
  4. Gently place the rocket over the stick, with salt container inside the engine.
  5. Warm the container and wait for sparks, then release the fuel and LOX.
A snippet of molten oxidizing salt shooting flames.. (1:55 – 2:10.)

Potential drawbacks include the risk of salt decomposing before the igniter set-up is prepared.


Now imagine, if you will, an engine inside an engine.

  1. Source a suitable solid rocket motor, given its thrust/time curve.
  2. Semi-permanently affix the motor to the bottom face of the injector.
  3. Ignite the solid rocket motor.
  4. Release the fuel and LOX.

Solid rocket motors produce a very well-regulated flame over a set period of time. Additionally, this set-up allows both flames (from the starter and the combustion) to travel in the same direction. By doing so, we can reduce the chance of the starter blowing out!