Spark strip

An etched copper spark strip

A spark strip is used to provide multiple sparks to ignite the fuel/air mix in a combustion launcher. It is differs from multiple spark gaps in that a spark strip is mounted using two or even one (temp link) hole. This is done primarily to ensure the integrity of the launcher, as drilling multiple holes weakens the chamber. Spark strips can also be used in coaxial launchers, where chamber space is more cramped.

A spark strip consists of several conductive objects in a row with a short gap in between, effectively forming a line of spark gaps. As with other spark gaps, the combined width of the gaps must be small enough for the ignition source to overcome.

There are several ways to achieve this:

scratched conductive film

By scratching thin lines across a conductive film (metallic paints, CDs) it is possible to get very large numbers of sparks out of a meager scource. A more sophisticated method consists of etching a spark strip pattern in a printed circuit board.

wire method

Small pieces of wire, BBs, nuts or other metallic objects are attached to the chamber wall. (either directly or indirectly).

veroboard

Veroboard is a ready-made circuit board with multiple copper strips or dots, a piece cut perpendicular to the copper strips will function as a spark strip.