This invention relates generally to igniters of the type having an igniter charge within a housing of sufficient strength to resist rupture during ignition combustion, and also having one or more nozzles for discharging igniting gases from said housing; such igniters are generally used for igniting bodies of solid propellant supported within rocket housings.
More particularly, this invention is concerned with an igniter of the type described in which the duration and pressure of the jets of igniting gas are controlled, at least in part, by an ignition charge comprised of an initial stage of rapid burning igniter material enclosed in or surrounded by a main ignition charge made up at least in major part of ignition pellets enveloped in slow burning or combustion resistant material.
In the preferred species of the invention, the main igniter charge is annular in shape and surrounds a core of initial igniter charge, into which a squib means discharges, with or without the aid of confining or directing barrier walls.
In rockets or missiles in which solid propellant is used, the propellant is ordinarily supported in a chamber inside a housing or case with free space around the propellant material. The means of support may be a spider or the like, but the present invention is not concerned with the nature of the propellant or of its support, or general structure, but only with the need for igniting it by means of hot igniting gases.
It is important for suitable ignition that the igniting gases be projected at or on the solid propellant in a desired manner for a suitable igniting time of a few milliseconds. It is desirable for reliable ignition, without failure and without irregular and improper burning of the propellant, that the igniting gases are supplied in a very roughly constant fashion for the brief but perceptible igniting period. Of course, the pressure of the gases will change substantially during the igniting period, but it is desirable to avoid very high peak pressures which then trail off to much lower pressures early in the ignition period.
One excellent solution for the problem has been to provide a strong igniter housing for the igniter charge, with a plurality of nozzle openings directed toward the propellant, and adapted to project a number of jets of hot the exposed surfaces of the solid propellant. Such an igniter housing may be in the form of an ignition charge container mounted in the end of the rocket housing, and provided with an electrically controlled squib igniting means in its outer end, external to said rocket housing.
The present invention uses such a housing but only as one co-acting part of a combination, the principal novel parts of which are the combustible igniter materials themselves, which are shaped into charges providing sustained and controlled ignition burning.