Patent Application
20140061364
1. Field of the Invention
This invention relates to attitude control systems for a self-propelled interceptor.
2. Description of the Related Art
Interceptors such as self-propelled rockets, missiles or counter-missile missiles may be launched from air, land or sea-based platforms to engage a target. The interceptor may be used offensively against other platforms, fixed emplacements or other targets or defensively to intercept and destroy enemy missiles. The interceptor may use explosive or kinetic energy to defeat the target.
The interceptor is propelled by a rocket motor. Rocket propellant is ignited and burns creating a high-pressure gas. This gas is expelled in a generally axial direction through one or more main nozzles that convert the high-pressure gas into a high-velocity gas.
The interceptor is maneuvered by an attitude control system (ACS). In general, the ACS produces a “moment” offset from the center of gravity (Cg) of the interceptor that interacts with the main axial thrust vector to change the attitude of the interceptor. This moment may provide yaw, pitch and/or roll control. One approach known as “thrust vector control” uses a servo motor to physically reorient the one or more main nozzles to produce the desired moment. Another approach known as “aerodynamic control” uses servo motor to physically deploy one or more aerodynamic control surfaces such as fins. Some interceptors use a combination of thrust vector control at low speed with aerodynamic control at high speed. Another approach is to selectively ignite one or more explosive guidance units (EGUs) placed on the airframe to generate impulse moments to control the attitude. In any of these approaches, a flight control system responds to guidance commands to command the ACS to maneuver the interceptor. Guidance may be provided as a command line-of-sight (CLOS) in which a targeting system tracks the target and the interceptor, calculates the appropriate guidance commands that will result in an intercept and send these commands to the interceptor to execute, a “beamrider” in which an IR sensor mounted aft of the interceptor “rides” an IR beam from the platform to the target, or a Homing Guidance (active, semi-active or passive) in which a sensor mounted forward of the interceptor locks onto the target.
The following is a summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not intended to identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description and the defining claims that are presented later.
The present invention provides an integrated propulsion and attitude control system (ACS) for an interceptor.
This is accomplished by providing the interceptor with a rocket motor having ports both forward and aft of the rocket propellant. Propellant burn forms a common pressure vessel for high-pressure gas to provide both propulsion and attitude control. One or more main nozzles in communication with the aft port convert high-pressure gas into a high-velocity gas that is expelled in a generally axial direction to propel the interceptor. The main nozzle(s) and stabilization fins are fixed, there is no servo control to the main nozzles or fins to affect attitude control. An ACS comprises one or more fixed attitude control nozzles in communication with the forward port to convert high-pressure gas into a high-velocity gas and expel the high-velocity gas in generally radial directions offset from the interceptor Cg to change the attitude of the interceptor. In an embodiment in which the main nozzle(s) are configured to produce a rolling airframe, a single attitude control nozzle provides both pitch and yaw control. In another embodiment, a set of four attitude control nozzles provides pitch, yaw and roll control. The multi-nozzle configurations may share a common throat for converting the high-pressure gas to high-velocity gas. A flight control system responsive to guidance commands, commands one or more valves to control the flow of the high-velocity gas through the one or more attitude control nozzles to maneuver the interceptor.
These and other features and advantages of the invention will be apparent to those skilled in the art from the following detailed description of preferred embodiments, taken together with the accompanying drawings, in which:
a and 3b are perspective and cut-away views of an embodiment of the interceptor revealing the common pressure vessel for integrated propulsion and ACS;
The present invention provides an integrated propulsion and attitude control system (ACS) for an interceptor. Propellant burn forms a common pressure vessel for high-pressure gas. An aft port in the rocket motor directs gas through one or more main nozzles that expel high-velocity gas in a generally axial direction to propel the interceptor. A forward port directs gas through one or more attitude control nozzles that expel high-velocity gas in a generally radial direction to control the attitude of the interceptor. The main nozzle(s) and stabilization fins are fixed, there is no servo control to the main nozzles or fins to affect attitude control.
The use of a common pressure vessel enables an integrated propulsion and ACS that can be compact, lightweight and inexpensive. The elimination of a second energy source to power the ACS, and specifically servo motors for mechanical control, streamlines the ACS and reduces the overall size, weight and cost of the combined propulsion and ACS. These attributes are generally desirable and are in particularly necessary for interceptors configured as counter-missile missiles in which the interceptor must be quite small and inexpensive.
Without loss of generality, the integrated propulsion and ACS will be described for an embodiment of a counter-missile missile launched from an airborne platform such as a jet fighter, helicopter or unmanned aerial vehicle (UAV). For context and clarity, an embodiment of a weapons system that employs the interceptor and the engagement CONOPS for using the interceptor to engage a MANPADS launched missile and the MANPADS operator are presented.
Referring now to
In a typical engagement scenario, missile-warning sensor 28 detects a threat launch of rocket 24, which activates DIRCM system 30 to track the incoming rocket with a laser beam 34. The helicopter's defense system selects the counter-threat missile system 14 to engage the threat and launch interceptor 20. In this embodiment, interceptor 20 has an aft facing IR sensor that rides laser beam 34 to engage and defeat rocket 24. Alternately, the interceptor may have a forward facing IR seeker to acquire, track and perform end game maneuvers. Or the interceptor may be configured for command line-of-sight (CLOS) guidance. A UAV in the theater of operations may detect the launch of rocket 24 from MANPADS 26 and direct DIRCM system 30 to illuminate the MANPADS 26 with a laser beam 36. Counter-threat missile system 14 launches a second interceptor 20 that rides laser beam 36 to engage and defeat the MANPADS launcher 26 and operator 32.
In an alternate scenario, the helicopter surveillance system detects the MANPADS launcher and operator as a potential threat and activates the DIRCM system 30 to acquire and track the MANPADS launcher 30. Counter-threat missile system 14 fires a pair of interceptors 20 in quick succession. Operator 30 fires the MANPADS rocket 24. Missile warning sensor 28 detects the MANPADS launch. The DIRCM system acquires the rocket 24 and directs the first interceptor 20 to engage and defeat the rocket. The second interceptor 20 holds its original course. After the rocket is defeated, the DIRCM system reacquires the MANPADS launcher and operator and the second interceptor 20 resumes beam rider guidance to engage and defeat the MANPADS launcher and operator.
Referring now to
Valves 58a, 58b, 58c and 58d are commanded in pairs to control the flow of high-velocity gas through the nozzles to maneuver the interceptor in yaw, pitch and roll. The beam rider IR sensor 60, electronics for the guidance system 62 that produces guidance commands and the flight control system 64 that is responsive to those commands to command the ACS 46, and more particularly valves 58a-58d, to maneuver the interceptor, and a battery 66 to power the electronics, valves and other systems on the interceptor are placed at the aft end of the interceptor. Four fixed fins 68 provide aerodynamic stabilization for the interceptor. The main nozzle(s) 52 and stabilization fins 68 as well as the attitude control nozzles 56a-5d are positionally fixed, there is no servo control to change the orientation of the main nozzles or fins to affect attitude control.
The use of a common pressure vessel to provide energy to both propel and maneuver the interceptor combined with the elimination of all servo control for ACS allows for an ACS and overall interceptor that is small, lightweight and inexpensive. In an embodiment, the interceptor is less than approximate 6.8 kilograms (15 pounds), 61 cm (15 inches) in length and 8 cm (3 inches) in diameter. These weights and dimensions are merely exemplary for a counter-missile missile but illustrate the ability to provide full 3-axis attitude control in a small interceptor. The ACS does consume energy provided by the rocket motor that is not available for propulsion. In a typical counter-missile missile the ACS will consume less than 10% of the energy produced from propellant burn.
Referring now to
The pair of fixed main nozzles 52 receive high-pressure gas from common pressure vessel 74 through all port 50, convert the high-pressure gas to a high-velocity gas and expel the gas in a generally axial direction (along longitudinal axis 76) to propel the interceptor. For the mid-body design, the main nozzles must be canted to expel the high-velocity gas outside the airframe. In general, the nozzles are canted to remove any non-axial thrust. However, the nozzles may be canted to produce a moment with respect to the axial thrust vector that produces roll to create a rolling airframe. For an aft-body design, a single main nozzle may be oriented along the longitudinal axis. To induce roll, the main nozzle may be formed with helical flutes.
Each main nozzle 52 has an associated throat 78 that converts the high-pressure gas to high-velocity gas 80 and an output port 82 that expels the high-velocity gas in a generally axial direction 84. In this embodiment, each main nozzle 52 has its own throat 78 to convert the high-pressure gas to high-velocity gas inside the nozzle. In an alternate embodiment, the main nozzles could share a common throat.
The four fixed attitude control nozzles 56a, 56b, 56c and 56d receive high-pressure gas from common pressure vessel 74 through forward port 54, convert the high-pressure gas to a high-velocity gas 86, and expel high-velocity gas 86 in generally radial directions 88a, 98b, 88c and 88d (approximately normal to longitudinal axis 76) to control the attitude of the interceptor in pitch, yaw and roll. The nozzles may be canted forward a couple of degrees e.g. 1-3 degrees to compensate for the velocity of the airstream so that the resulting force vectors more closely approximate a true radial direction orthogonal to the longitudinal axis. The expulsion of high-velocity gas 86 through any one or more of the nozzles produces a moment with respect to the main thrust vector along longitudinal axis 76. This moment may cause the interceptor to yaw, pitch or roll.
Each attitude control nozzle 56a, 56b, 56c and 56d has an associated throat 90 that converts the high-pressure gas to high-velocity gas 86 and an output port 92a, 92b, 92c and 92d that expels the high-velocity gas in the generally radial directions 88a, 98b, 88c and 88d. In this embodiment, the attitude control nozzles share a common throat 90. A manifold 94 provides the common throat 90 to meter and direct flow of the high-velocity gas 86 to the four output ports 92a, 92b, 92c and 92d via the four valves 58a, 58b, 58c and 58d. In an embodiment, the common throat 90 is a Mach 1 choke port. The use of a common throat, as opposed to individual throats within each nozzle, provides a uniform metered flow rate for each nozzle.
Referring now to
Referring now to
The creation of the common pressure vessel to provide a single source of high-pressure gas to both propel the interceptor and provide attitude control is critical to providing an ACS and full-up interceptor that is small, lightweight and inexpensive with required maneuverability performance. However, the use of the common pressure vessel to source two different systems complicates the motor design process. The propellant grain design has to support the boost-sustain thrust profile requirement to maintain control via the main and attitude control nozzles all the way to the target. If both throats are sized correctly, an appropriate portion of the gas will flow to the rear and the rest to the front. The rocket motor and both throats must be designed and the nozzles controlled to main the common high-pressure vessel and flame front without causing overpressure when the attitude control thrust is not required. For a rocket motor that burns radially inside-to-out, propellant burn forms a common combustion chamber for both propulsion and attitude control. When attitude control thrust is not being used, the high-pressure is vented through the main nozzle. For a rocket motor that burns axially from both end, propellant burn forms a combustion chamber aft for propulsion and a combustion chamber forward for attitude control. If the valves for attitude control are normally closed, the forward combustion chamber may overpressure and cause the motor to fail. Operating the ACS with the valves in a normally open position vents the high-pressure gas and maintains conditions for efficient and safe motor operation.
While several illustrative embodiments of the invention have been shown and described, numerous variations and alternate embodiments will occur to those skilled in the art. Such variations and alternate embodiments are contemplated, and can be made without departing from the spirit and scope of the invention as defined in the appended claims.
