guest blogger john hare
One of the things that I take exception to is people saying there is only one way to do something. From some people I get irritated, from others I enjoy finding some way of proving them wrong. This one actually was a joke at the expense of the Masten team before I realized they were a team. Between sessions at a conference one of the guys said something to the effect that the only reliable ignition system was electrical, or that there were only two total ignition methods, I think. So I spun this one out as a joke after at least 10-15 seconds of design and planning work. My sense of humor becomes more strange than normal when I’m running minus on sleep at a conference.
An hour or so later, I realized that it was actually possible to use something like this, and lost a bit more sleep trying to figure it out. This is just the simplest way to draw the concept, by no means the only way.
A small subchamber has a rotating flap that seals to the edges. When gaseous propellants are introduced into the subchamber, they drive the flap which is also a flint holder. The arc that the flint travels is a serrated steel edge roughly opposite to a cigarette lighter. The sparks from the flint and steel ignite the propellants in the subchamber and they in turn ignite the main chamber propellants. The main chamber ignition pushes the flint holder flap back into the subchamber and holds it there unless main chamber pressure drops below that of the subchamber. If the main chamber drops below that of the subchamber, the spring pushes the flap far enough to release the pressure switch releasing propellants into the subchamber to be ignited. Position of the flint holder flap can be used for the safety interlocks of the main propellant.
The possible use for this would be on a system that required multiple starts, and that for some reason didn’t want to depend on hypergolics or an electrical ignition system. Attitude control just might be one such use. Send the propellants and let the flint ignite them instead of a separate electrical system.