First steps with the ignition system
There is a pyromaniac buried in each little boy... and in grown men, too!
Yesterday night at the Electrolab was dedicated to testing a fairly simple ignition system, consisting of a Sparkfun Spark Gap Igniter to set off combustion, and a blend of steel wool and cotton to burn.
As the first engine we plan to test will be using paraffin as fuel and nitrous oxyde as oxidizer, we need to design a system which will bring the combustion chamber to at least 350°C (to get the nitrous oxyde to separate into O2 + N2) and for the paraffin to sublimate, as it is in its gazeous form that it burns. So the current plan is to stuff the pre-combustion chamber and a part of the port which will cross the whole length of the fuel grain with this blend of steel wool and cotton.
Steel wool ignites very fast, while cotton will burn a bit longer, so this could be a viable option to use.
As always, the onlookers in the lab were bustling with alternative ideas to generate ignition, from using a blend of salpetre and sulfur (both can be easily purchased in pharmacies, and together form a nice solid explosive) to using only cotton wet with wood alcohol. Both are worth keeping in mind if the current solution does not yield satisfying results.
Several tests were performed tonight, and here are the videos of the most significant tests. The difference between each test was mainly the way the steel wool and the cotton were put together.
1st test: The cotton is too tightly packed to ignite.
2nd test: The cotton is a bit less packed and ignites.
3rd test: Both the cotton and steel wool have been spread adequately, combustion is far more significant.
In the last test, the steel wool and cotton were put together in several layers, very well spaced and aired. This will probably be the way forward - the next step is to test this with actual paraffin to ignite, and nitrous oxyde released on it, at a very small scale.
Again in praise of the Electrolab (and of fablabs in general): I am a total neophyte in dealing with ignition, but the tests were performed under the supervision of 3 onlookers, two of whom had chemistry experience, and a fire extinguisher was accessible within arm length. This way, it does feel safe to tinker with DIY rockets!