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ing, as is shown for O-ring 61 placed in recess 62, in con- The entire charge 22 is enclosed in a moisture-imper-
nection with igniter cup 32 in FIGURE 2. vious film, which protects it from the 1:1-oisture or other
The cover 13, which may be referred to as the inner airborne impurities which might otherwise enter ilirough
end of the igniter housing 11, since it projects into the the nozzle openings 15 during storage prior to use. The
interior of the rocket housing with which it is used, is 5 film is indicated generally by the numeral 23, and may be
provided with a number of openings 15, which serve as understood to be any of a variety of suitable materials.
nozzles and may project jets of igniting gases in a num- For example the film may be aluminum foil, a sheet of
ber of directions, as desired, when the igniter 10 has been plastic such ;s Mylar plastic, or even paper impregnated
ignited. The outer end of the cup 12, which is normally with some suitable moisture resistant impregnating ma-
exposed outside the rocket housing, is provided with a~y IO terial. Also, the film 23 may be a painted coating applied
suitable squib means 16. The commonest type of sqmb to the igniter charge after its formation, and before or
will be comprised principally of a readily combustible after insertion into the igniter housing 11. It should also
powder packed around an electrical heating element which be understood, that the film 23 may be actually somewhat
is connected by means of leads to a suitable source of thicker than an ordinary film and may actually be com-
igniting power and control switch. However, the inve1:1- 15 prised not only of a waterproofing material but a cushion-
tion is not limited as to squib means, and any fuse sqmb ing lining of such materials as felt, plastic foam, or the
device or the like which meets the engineering require- like.
ments of a particular case may be employed. · The operation of the igniter of FIGURE 1 will be
The interior 17 of the igniter housing 11 is filled with obvious to those skilled in the art of igniters. The igniter
an assortment of three kinds of small pellets forming the 20 housing 11 is constructed of sufficient strength to resist
igniter charge. These pellets may be identified as rapid rupture at the igniter combustion pressures. Conse-
burning pellets 18, which are preferably relatively small, quently, when the squib 16 is fired,_ the central cor~ 20
and are uncoated and unprotected from the fire of squib which is comprised of a concentrat10n of the relatively
16. These pellets serve to insure initial firing of the ig- small and uncoated rapid burning pellets 18, is ignited
niter charge and a few of them may be scattered through 25 as the first stage of ignition.
the entire charge, if desired, to insure continued burning. The pressure of the hot gases produced breaks through
Their only essential location, however, is in the immedi- the light film 23 and jets from the nozzle openin_gs 15 to
ate vicinity of the squib 16. Some must be concentrated begin ignition of propellant. Within a short time, the
in that region in order to assure initial firing, even if there increased pressure and temperature within the igniter
are no rapidly burning pellets 18 in the remainder of the 30 housing 11 advances combustion to the second ignition
interior 17. charge 22, comprised of the coated and relatively slower
Slow burning pellets, which may also be referred to as
sustaining pellets, are preferably, alt~ough !lot neces- burning pellets 19 distributed in an annulus around the
central core 20.
sarily, substantially larger than the rapid burrung pellets. FIGURE 2 illustrates a three-stage embodiment of the
Their essential difference is that they are covered over all 35 igniter of the invention. The three-stage igniter indi-
or a large part of their exterior surface with a thin _coat-
ing of a silicone paint or the like. In the embodiment cated generally by the numeral 30 has its charge enclosed
illustrated the slow burning pellets illustrated at 19, in a housing indicated generally by the numeral 31, com-
have been' entirely covered with a spray coating of sili- prised of a cup 32 and a cap 33, _cup 32 bei!1g thre.ad-
ably received in the end of the housmg 60, seatmg agamst
cone paint, although their interior compositi9n is identi~al 40 the O-ring 61, in the annular recess 62.
to that of the rapid burning pellets 18. It 1s an essential
feature of the invention that the slow burning coated Cup 33 is provided with a plurality of nozzle open-
pellets 19 be distributed around or enclosing the central ings 35 by means of which the igniter 30 projects jets of
concentration 20 of rapid burning pellets 18. igniting gases against the propellant charges 64 and 63
Typical pellet size for most igniters is about ¼ inch in during ignition. Propellant charges 64 and 63 are sup-
diameter by ¼ inch long for the smaller pellets, up to 45 ported within the rocket housing 60 with a substantial
½ inch in diameter and ¼ inch long for the larger pel- region of clear space between them and the igniter 30,
lets, particularly those which are coat~d _and are to serve and between each other. Such support may be made
as the sustained burning stage of the 1gmter. The pellets within the housing 60 by means of support spiders, hous-
may range in weight from only a few grams up to over ing structure or the like, all in the manner well known to
one hundred grams. They should be sufficiently numer- 50 those familiar with the construction of rockets, and not
ous so as to provide a readily distributable structure, illustrated herein since they form no part of the present
usually fifteen to two hundred pellets, and over fifty per- invention. It should only be noted that the spacing illus-
cent of the material should be concentrated in the coated trated in FIGURE 2 is not proportionate to actual dimen-
sustaining pellets. sions; the spacing has actually been reduced very much
Coating of the pellets 19 has been found to have a 55 in order to make illustration convenient.
beneficial effect on the prevention of attrition, in addition An electrical squib means 36 is threadably received in
to the suppression of combu_stion rate which _Pr?d~ces a threaded bore 36a in the center of the outer end of the
the ignition of desirable duratron 3:nd pressure. hmitatro!1· igniter housing cup 32.
However in the particular embodiment described herem The igniter means 36 is used to ignite an igniter ch~rge
in conne~tion with FIGURE 1, close packing of the pellets 60 identified generally by the numeral 37, and comprised
18 and 19 are achieved without much attrition resulting principally of small uncoated pellets 38 and large coated
by random scattering of many chunks of cushioning ma- pellets 39, corresponding approximately to the p_ellets 18
terial 21 which may be referred to as cushion "pellets," and 19 described in connection with the embodiment of
although it is not compressed or pelletized in any sense, FIGURE 1. However, the embodiment of FIGURE 2
but it is very soft. 6 5 employs additional igniter. material and features of con-
The entire igniter charge, which may be referred to struction not found in FIGURE l.
collectively by the numeral 22, may appear at first to be A first-stage ignition charge is in the form of a core
packed as an entirely random assortment of rapid burn- 40 comprised of relatively rapid burning uncoated pel-
ing pellets 18, slow burning coated pe~ets 19, . and let; 38 and housed in a tubular housing 41, which is
cushioning material 21. However, as previously pomted 70 disposed coaxially with the cup 32, and has its lower end
out, it is actually packed as a more or less annular p~ck received in a central recess 42 in the inner wall of the
comprised predominantly or exclusively of slow burmng bottom of the cup 32. Tubular container 41 may be
uncoated pellets 19, so far as igniter material is con~erned, either of metal or of relatively combustion resistant non-
enclosing a core 20 of rapid burning pellets 18 disposed metallic material, such as certain impregnated papers,
imm~diately adjacent to the igniter 16. 75 or certain plastics. It is necessary that the walls of the