woensdag 6 juli 2016

Nichrome and black powder electrical pyrotechnic igniter with GALCIT solid rocket propellant

We've made progress on the pyrotechnic igniter. It now uses nichrome wire because it has a high resistance, so it gets very hot when electricity is forced through it.

We wind the nichrome in a spiral so that it is longer, again for more electrical resistance, and place it on a paper rectangle of around 5x10cm.

Nichrome wire spiral

The nichrome wire has a diameter of 0.2mm and when stretched out is about 150mm long. With a resistance of 34 Ohm per meter, that is around 0.51 Ohm resistance in that piece of 150mm nichrome wire. 

Then we pour some black powder over the coil and roll it up into a cylinder, reinforced with some paper tape.

Black powder in paper with nichrome wire spiral inside

As a test we ignited a bit of leftover GALCIT in a heat resistant 2l lab beaker.

Heat resistant, yes, but as it turns out it was not GALCIT heat resistant. 

Our final setup looks like this, placed on a burn pile:

Pyrotechnic igniter installed in a lab beaker 

To get the nichrome to glow red hot, we used a powerful 18V battery from a Makita drill to supply the current through an old UTP cable. But a 4.5A 6V battery should also do the trick.

The ignition went smoothly and the burn was quite spectacular. The jet of fire that was spewed into the air indicated that we were already developing some thrust, which is remarkable with such a huge throat (in this case, beaker) area.

Here's the video: