Igniter and gas generator for rocket motor

A rocket motor equipped with a movable nozzle is provided with pneumatic pressure system for the operation of the mechanism for moving the nozzle with a gas for the pneumatic supplied from a gas generating propellant separate from the main propellant but located within the motor itself.

BACKGROUND OF THE INVENTION AND DISCUSSION OF THE PRIOR ART 
Rocket motors are often equipped with outlet nozzles which are movable so 
that their longitudinal axes can be directed angularly with respect to the 
longitudinal axis of the motor so that the thrust exerted by the passage 
of combustion gases from the motor can be directed for the purpose of 
steering the vehicle to which the motor is attached. The nozzle is mounted 
on a swivel or ball joint at the nozzle throat so that it can be moved 
universally by the application of forces upon it created by mechanical or 
hydraulic means under the influence of a control system. Such an 
arrangement is shown in U.S. Pat. No. 3,049,877 to Arthur Sherman, 
particularly in FIG. 2 thereof, wherein hydraulic struts are externally 
connected mechanically to the nozzle of the motor and cause it to be moved 
universally (within its mechanical limits) as pressurized hydraulic fluid 
is valved to the struts through a controlled spool valve. 
Another U.S. Pat. No. 3,912,172 to Thomas Bolner utilizes the internal 
structure of the nozzle's ball joint, at the juncture of the nozzle to the 
rocket motor's combustion chamber, to provide an internal means for moving 
the nozzle, and, it is this latter arrangement for which the present 
invention provides a pneumatic pressurized gas source instead of a 
hydraulic liquid system. 
The present invention is concerned with the provision of a simple, compact, 
lightweight, reliable and positive source and supply system for a 
pressurized gas wherein a gas generant is burned in the system and is 
supplied to the actuating means. In addition, the pneumatic gas generating 
system is combined into a single structural unit with the ignition system 
of the rocket motor and is within the rocket motor thus producing a saving 
in weight and space requirements, both of which are important 
considerations in flight hardware such as rocket motors. 
The provision of a pneumatic system in the present invention is 
advantageous over the previously used liquid hydraulic system in that the 
gas cannot freeze, congeal or change significantly with high altitude or 
space conditions as could be the case with some fluids. Also, if a leak 
should occur, the gas will pass harmlessly out of the system whereas 
hydraulic liquids might leak onto other components and cause corrosion, 
possible corrosion, create a fire hazard or cause electrical short 
circuits. 
OBJECTS OF THE INVENTION 
It is, therefore, an object of the invention to provide an improved system 
for the operation of a vectorable nozzle of a steerable rocket motor 
wherein the operating fluid is pneumatic. 
It is also an object of the present invention to provide a system of the 
foregoing type wherein the operating fluid is a combustion gas. 
It is also an object of the present invention to provide a system of the 
foregoing type wherein the operating fluid is a combustion gas supplied by 
a gas generant. 
It is also an object of the present invention to provide a system of the 
foregoing type wherein the gas generant is located within the rocket 
motor. 
It is also an object of the present invention to provide a system of the 
foregoing type wherein the gas generator is located in a common housing 
with the rocket motor's igniter and both are located within the rocket 
motor. 
Other objects and advantages of the present invention will become apparent 
from the descriptions of the device and of its operation which follow.

DETAILED DESCRIPTION OF THE INVENTION 
In a preferred embodiment of the invention, and with reference particularly 
to FIG. 1 of the drawings, a rocket motor 10 is shown having an outer 
casing 11 closed at its head end (not shown) and containing a solid 
propellant 12. The casing 11 has an assembly located at its after end 
(right hand end in FIG. 1) to receive and retain an exhaust nozzle 13 by 
means of a sliding ball joint connection comprising a central annular 
throat 14 having a substantially spherically-shaped outer retaining 
surface 14a and a mating spherically surfaced outer member or shell 15 
partially covering surface 14a as shown. Shell 15 extends inwardly toward 
motor casing 11 (to the left in FIG. 1) and is connected to casing 11 
about its inner periphery by means of retaining ring 16 which fits in 
corresponding grooves 17 and 18 in casing 11 and shell 15, respectively, 
and prevents separation of the two members. An O-ring seal 19 is provided 
between casing 11 and shell 15 to prevent leakage of combustion bases from 
the motor at this joint. 
An outer shell member 20 is attached to member 15 in the manner shown in 
FIG. 1 and is arranged to provide a gap or chamber 21 therebetween which 
is annular in shape in one dimension and curved in its other dimension so 
as to conform to the semi-spherical shape of member 15. An additional 
shell or member 22 is fixedly attached to the outer end of nozzle 13 and 
extends into gap 21 about one-half of its length with nozzle 13 in a 
straight ahead attitude. Shell 22 is formed into a spherical shape on each 
of its sides to match the spherical surfaces of members 15 and 20 where 
they are adjacent the gap 21 and is slidable in gap 21. A clearance space 
23, vented to atmospheric conditions or to space conditions by means of 
vent holes 22a is provided between the right hand end of shell 15 and 
nozzle 14 to permit movement of nozzle 13. Seals 24 and 25 are included in 
grooves on the inside surface of member 15 to prevent hot gases from the 
rocket motor's combustion chamber from passing between surface 15a of 
nozzle 13 and member 15 and to act as a smooth surface upon which the 
nozzle 13 can be moved relatively easily. 
As mentioned previously in this specification, a gap 21 is provided and 
this gap contains four seals 26 which are closed elongated loop seals set 
in the gap and spaced 90 degrees apart about the circumference of nozzle 
13. Such an arrangement of loop seals 26 is known in the art and is 
described in the patent to Thomas Bolner (U.S. Pat. No. 3,912,172) 
mentioned earlier in this specification. 
An annular or toroidal ring assembly 29 is located within the rocket motor 
at its after end as shown where it encircles the nozzle 13 and its annular 
frontal piece 30 in the manner shown in FIG. 1. As will be seen, the 
location of the ring assembly 29 is out of the main flow of combustion 
gases to some extent and does not interfere with the normal flow into and 
through throat 14 of the nozzle 13. 
The ring assembly 29 is comprised of members 29a, 29b, 29c, 29d and 29e. 
Annulus 29a serves as a protection from the rocket blast and is made of 
silica-filled rubber. It is open at its right hand side in FIG. 1 to 
accomodate annular metal ring 29e which is also open on its right hand 
side in FIG. 1 and is provided with external threads which mate with 
matching threads on member 15 to form an enclosure upon assembly. Before 
assembly, however, an inhibiting and insulating barrier member 29c is 
inserted in ring 29e with its right hand side in FIG. 1 open to receive 
igniter-generator retainer or "doughnut" 29b which is placed therein in 
the manner shown with member 29c between ring 29d and retainer 29b. 
Retainer 29b is made of a hard plastic material and contains arcuate, 
alternate segments of gas generator propellant and igniter propellant as 
discussed below. The entire assembly 29 is then screwed in place on member 
15 as shown in FIG. 1. 
Also, member 29c includes divider walls 29d as integral parts which also 
serve as inhibiting and insulating barriers. As will be seen in FIG. 2, 
nozzle outlets 31 are fitted between these walls 29d with the nozzle 
outlets 31 open to the combustion chamber of the motor adjacent the solid 
propellant as shown in FIG. 3. Also with reference to FIG. 2, the curved 
retainers 29b are closed at their ends to form complete enclosures except 
as described later in connection with the igniter system. 
Within each of retainers 29b is a combustible charge of propellant 
material. Two of these charges, 32 and 33, are of a gas generating 
composition and the other two, 34 and 35, are of a composition suitable to 
burn hot enough to cause ignition of the motor's main propellant. Such 
materials are well known in the art for ignition purposes and for 
supplying the gas for gas operated devices. The charges 32 and 33, which 
can also be referred to as gas generator segments, are completely 
contained in a gastight manner in a retainer 29b but have outlets such as 
shown at fittings 27 and 28 which lead through suitable pipes or conduit 
passages to a suitable gas pressure control and distribution system as 
shown in FIG. 1 from which the gas is distributed to, or bled from, the 
loop seals 25 to operate the movable nozzle 13. 
The igniter segments 34 and 35, on the other hand, are each in 
communication with the nozzle outlets 31 at each of their respective ends. 
OPERATION OF THE INVENTION 
In order to set the rocket motor 10 in operation, the igniter segments 34 
and 35 are ignited by means of a conventional electrical ignition system 
(not shown). As these burn, the hot gases and flame produced by their 
combustion exit through nozzles 31 and impinge upon the rocket motor's 
solid propellant 12 and it becomes ignited and produces large quantities 
of combustion gases which then pass out of the rocket motor 10 through 
nozzle 14 and produce thrust directed along the central axis of the 
symmetrical nozzle 14. 
The thrust produced can, however, be directed in directions other than 
axial of the motor by moving to vector the nozzle in a rotary manner about 
its ball joint, thus producing a steering effect for the motor 10. As 
mentioned previously in this specification, this is accomplished in the 
present invention by the application of pneumatic pressure generated by 
the combustion of the gas generator compound contained in generator 
segments 32 and 33. These gas generators are also ignited by the same 
conventional electrical means at the same time as ignition of the igniter 
segments 34 and 35 takes place. As they burn, the gas generated by their 
combustion is carried through outlets 27 and 28 to the conventional gas 
pressure control and distribution system and thence to the interior of 
loop seals 26 to move the nozzle in accordance with the program 
established by the control system. The loop seal 26 area opposite the 
pressurized loop seal is bled of pressurized gas by the control system to 
reduce its resistance to movement of the nozzle 13. 
When the pressure in the main chamber rises to a level of approximately one 
half of the igniter-generator, the motor pressure influences the 
igniter-generator pressure and changes the igniter-generator flow to the 
motor from supersonic to subsonic. 
When the igniter grains burn out and only the generator grain remains 
active, the pressure ratio (igniter-generator/motor) falls at this point 
to nearly unity; i.e., the igniter-generator pressure is only slightly 
higher than the motor. The generator grains however continue to produce 
warm gas for actuation. The generator grains also provide excess gas (more 
than required for the nozzle actuation) which is vented into the motor 
chamber to isolate, by preventing back flow, the actuation system from the 
relatively "dirty" exhaust products of the motor propellant, which, if 
used directly, would contaminate and overheat the warm gas pressure 
controlled distribution system. 
While there have been shown and described and pointed out the fundamental 
novel features of the invention as applied to a preferred embodiment, it 
will be understood that various omissions and substitutions and changes in 
the form and details of the device illustrated and in its operation may be 
made by those skilled in the art, without departing from the spirit of the 
invention. It is the intention, therefore to be limited only as indicated 
by the scope of the following claims.