dinsdag 27 september 2016

Successful GALCIT 61-C ignition using standard electrical matches

We recently experimented with standard electrical matches to ignite GALCIT 61-C propellant samples in combination with an off-the-shelf 433Mhz wireless pyrotechnic ignition system.

This work is part of our effort to obtain a reliable, cheap and easy method for igniting GALCIT propellant for both small and large scale GALCIT solid propellant rocket motors.

We learned from the experiments that these igniters work very well when used correctly.

The correct way to use these igniters with GALCIT 61-C is to make sure they are embedded in GALCIT 61-C in such a way that they have a layer of at least 1 cm of GALCIT 61-C propellant extending from the tip of the igniters.

This is the wrong way:

Wrong way to embed the igniter in the GALCIT propellant with only a few millimeters of GALCIT at the tip of the igniter

When this igniter is used, a small hole is blown through the GALCIT and the hot flames are just heating up air.

Here's the brief video of the failed ignition:

 Here a closeup of the GALCIT sample that failed to ignite:

Burned through rather than ignited GALCIT sample

This is the corrected way to embed the igniter in GALCIT:

Correct way to embed the igniter in the GALCIT propellant with around 2 cm of GALCIT located at the tip of the igniter

The reason that this works a lot better is that the 2-3 cm long hot flame of the igniter is propelled forward to the tip of the igniter and not (or barely) to the sides. Any GALCIT that is placed will not ignite, although it can still be useful to have it there for practical purposes such as ensuring the igniter adheres properly to the GALCIT.

Below is a picture of the receiver of the standard RF pyrotechnic igniter that we used. We later added an extension cord to ensure it would not get too hot from being close to the burning propellant.

Receiver of the 433Mhz RF pyrotechnic igniter 

In the end, we were able to attain 100% reliable ignition of GALCIT 61-C in 3 out of the 3 tests where we had properly installed the igniter in the propellant.

We were also successful in achieving contact ignition, where a small burning chunk of propellant ignites a larger one that is in contact with it rather than being embedded in it.

Below is a close-up of the contact ignition set-up. The igniter, embedded in a small chunk of GALCIT, is placed underneath the big GALCIT sample:

Contact ignition setup

Contact ignition has the benefit that the igniters do not necessarily need to be embedded in the main propellant grain. Instead, they can be embedded into a small chunk of propellant that is in contact with the main propellant grain, which might reduce the complexity of casting propellant and installing igniters into large scale motors.

Finally, below is a video of one of our successful ignitions:

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