Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-09-08
2003-04-29
Aftergut, Jeff H. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S169000, C156S187000, C156S192000, C060S253000, C060S255000, C523S138000
Reexamination Certificate
active
06554936
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to materials and methods used to insulate structures from high temperatures and pressures generated during the combustion of fuels. The present invention is particularly suitable for insulating structures, including, but not limited to, dome structures, nozzle structures, and igniter structures of rocket motors, such as solid propellant rocket motors used in the aerospace industry.
2. State of the Art
Solid propellant rocket motors have a center bore and/or cavity in the aft end of the motor in which combustion products of the solid propellant flow and are directed through the throat of a nozzle. Combustion occurs on the surface of the propellant and the resulting combustion products, upon passing through the throat, expand and are expelled from the exit cone of the nozzle located at the aft-most end of the motor. Combustion products are accelerated from subsonic velocities at high pressure within the rocket motor to supersonic velocities at near ambient pressure as the combustion products pass through the exit cone of the nozzle. The very high velocities at which the combustion products have been accelerated and directed by way of the rocket motor provide the thrust needed to propel the craft, or spacecraft, to which the rocket motor or motors are mounted.
Open-ended solid propellant rocket motors typically have a much larger cavity in the aft end of the motor, referred to as the aft dome. The open-ended design is used to facilitate and ease the retraction of mold tooling used in forming the internal geometry of the propellant grain within the rocket motor. With open-ended rocket motors, combustion products can impinge directly on the aft dome at velocities exceeding 300 feet per second (91 m/s) before exiting the nozzle.
Because of the high temperatures and pressures at which propellant fuels burn, typically of the magnitude of 5000° F. (2760° C.) and 1500 PSI (10,341 KPa), it is necessary to provide the internal surface of such rocket motor domes, as well as other components and portions of the motor, with a thermally insulating material that can withstand the impingement of high-velocity gases and oxidized, or partially burned particles of fuel. The structure of the aft dome is typically made of aluminum, an alloy steel, or a fiber-resin composite and would quickly rupture if directly exposed to the high-velocity, high-temperature combustion gases and oxidized particulates. The insulating material also serves to contain and protect the immediately surrounding area of the motor from the large amount of heat generated by the rapid combustion of propellant fuels. Thus, the insulating material must not only be capable of withstanding the impact of high-velocity gases and particulates, which are very erosive to insulating materials, but must also be able to withstand being subjected to high temperatures and high pressures upon the firing of the rocket motor.
Rocket motors have a nozzle exit cone, which directs the burning gas out of the motor and away from the craft. Such exit cones can be a fixed-type cone, which is typically immovably mounted to the aft or rearward portion of the dome. Alternatively, and frequently, the exit cone can be a variable-angle or vectorable-type cone which is pivotably mounted to the aft portion of the dome so that the exit cone can be moved angularly within a selected range to vector, or steer the craft in which the motor is installed, thus providing more directional control of the vehicle. Typically, the exit cone of a vectorable-type nozzle can be vectored within a range of 0 degrees to 10 degrees. The exit cone, whether a fixed-type or a vectorable-type, is typically attached directly to the aft portion of the dome and is often canted at a preselected angle from the centerline, or longitudinal axis, of the motor. This is particularly true when the motor is configured as a strap-on booster rocket to provide increased launch capacity for a primary or core space vehicle. A cant angle of up to 10 degrees from the centerline, or longitudinal axis, of the motor is frequently used. However, other cant angles can be used as necessary. The cant is often necessary in crafts having multiple booster rockets, and is required to direct the exiting flame away from the centerline of the craft to prevent overheating or scorching of the craft itself or of adjacently mounted motors.
Thus, the dome of an open-ended rocket motor as well as the insulation contained within the interior of the dome must be configured so as to allow the exit cone of the motor to be canted at a preselected angle and/or vectorable within a preselected range of angles. The cant and/or sustained vector at a given angle gives rise to increased char in the aft dome as gases are turned to exit through the nozzle throat. The effect of the nozzle cant also results in higher manufacturing costs due to more complex machining, additional labor, and material scrap.
The art in the past utilized domes, typically made of a preselected metal alloy, in which two to three preformed rings of tape-wrapped carbon phenolic insulation were bonded into position in a consecutive fashion within the dome to form a thermally insulating barrier therein. Tape-wrapped carbon phenolic insulation has been used in the past to minimize inert weight due to increased thickness and because of its ability to withstand the mechanical and thermal erosion attributable to direct impingement of combustion products on the open-ended aft dome. Each of these rings were usually manufactured separately because of the complex geometry of sequentially increasing diameters in order to be fitted within the dome at a proper station. The hollow done like ewise increases in diameter as viewed from the aft position, or nozzle end, of the motor, and moving forward or away from the exit cone toward the dome where propellant fuel is undergoing combustion.
In order to better understand and appreciate the present invention, reference is made to exemplary prior art insulators installed in the domes of open-ended solid propellant rocket motors shown in
FIGS. 1 and 2
.
FIG. 1
depicts an open-ended aft dome and nozzle of a motor having a fixed-type exit cone, whereas
FIG. 2
depicts the open-ended dome and nozzle of a motor having a vectorable-type exit cone.
More particularly, motor
2
depicted in
FIG. 1
is provided with a dome shell
10
which generally encases an open dome region
4
and a nozzle throat region
6
, and an exit cone shell
22
which generally encases an exit cone region
8
. Dome shell
10
is typically a shell made of a pre-selected metal alloy and includes a flange portion
26
for allowing the dome shell
10
to be sealed and secured to the motor chamber case (not shown). Exit cone shell
22
is also typically made of a metal alloy and exit cone insulative liner
24
is typically made of a tape-wrapped carbon fiber/phenolic composite material. The cant, or angle, at which the dome shell
10
must be configured in order to allow exit cone shell
22
to extend away from the horizontal longitudinal centerline of the motor is designated as angle &agr;. As mentioned previously, angle &agr; can range from 0 to about 10 degrees, but &agr; can be any suitable angle.
As can be seen in
FIG. 1
, nozzle throat region
6
is defined by an integral throat entry (ITE)
18
which is typically formed of a three-directional or four-directional tape-wrapped carbon-carbon composite material and is externally supported by a nozzle throat insulator
20
typically formed of a unidirectional tape-wrapped carbon fiber/phenolic material.
It can further be seen in
FIG. 1
that open dome region
4
is defined by aft dome insulator
14
which lines the more aft portion of dome shell
10
back to the integral throat entry
18
. Forward dome insulator
16
abuts with aft dome insulator
14
at joint interface
15
and insulatively lines dome shell
10
from joint interface
15
forward to flange portion
26
. Located behind dome insulators
14
and
16
and t
Metcalf Gary S.
White William E.
Aftergut Jeff H.
Alliant Techsystems Inc.
TraskBritt
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