Dissolvable thrust vector control vane

Details Dissolvable thrust vector control vane Dissolvable thrust vector control vane

2001-03-13

2003-04-15

Barefoot, Galen L. (Department: 3644)

Aeronautics and astronautics

Missile stabilization or trajectory control

C244S003250, C244S003220, C244S052000, C060S230000, C239S265150

Reexamination Certificate

active

06548794

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a missile control system, and more particularly, to a thrust vector control vane and system mounted in the aft portion of a missile and used for steering the missile during launch, as well as a method of making and a method of using such a control vane.
BACKGROUND OF THE INVENTION
Aircraft and offensive missiles, including some cruise missiles, for example, often fly at low altitudes to avoid detection by enemy radar. In such situations the target, such as a ship, may have only a few seconds to both identify the threat posed by the incoming aircraft or missile and take countermeasures, such as firing a defensive missile. Thus, it is desirable to have a defensive missile locate and disable the offensive missile very quickly.
Land or ship borne defensive missiles generally are launched from a canister in a substantially vertical orientation. Missiles generally have steering control systems which include external aerodynamic control surfaces for guiding the missile. Before its aerodynamic control surfaces or fins are able to affect any significant maneuvers, the missile must achieve a certain minimum velocity, referred to herein as the aerodynamic control velocity, to cause enough air to flow over the aerodynamic control surfaces and provide aerodynamic control. For a ballistic launch trajectory, the missile reaches an altitude of thousands of feet before the aerodynamic control surfaces can cause the missile to pitch over and begin seeking the incoming missile threat. As a result a ballistic launch trajectory is inefficient, time consuming, and limits the missile sensor line-of-sight capabilities for optimum target detection and tracking.
A number of systems have been developed in an attempt to maneuver the missile prior to reaching an aerodynamic control velocity and to decrease reaction time after sensing an incoming threat. However, most current devices, although generally acceptable for some uses, have been found to be inadequate for many applications. Detachable jet tab systems, for example, formed of auxiliary propulsion units mounted to missile fins conflict with folding control surfaces. Folding control surfaces generally are necessary for any missile to be loaded into a launch canister having stringent volume constraints. Detachable jet tab systems require increases in the launch canister cross-sectional area for additional volume taken up by the jet tabs external to the missile fuselage.
Existing systems generally also can be classified as either nondetachable or ejectable, the latter often incorporating redundant control electronics. Nondetachable systems limit mission range and performance with rocket thrust degradation throughout the missile trajectory. Detachable, self-actuation mechanisms are substantially heavier and inherently more complicated than nondetachable systems. The increased complexity leads to reduced reliability, and the added weight requires more rocket propellant for missile launch and flight to the target. An actively detachable system generally uses a pyrotechnic actuated ejection mechanism and disengageable power coupling drive that introduces weight, complexity, and multiple operational failure risks. Furthermore, the act of ejecting the control system can knock the missile off its intended trajectory.
To overcome the deficiencies of prior systems, systems have been developed that place a mechanism in the exhaust plume of the rocket engine for control purposes, providing control immediately upon launch. Generally, the purpose is to pitch the missile over (rotate the missile about an axis transverse to the longitudinal axis and previous direction of flight during launch) and to avoid rolling. Rolling generally interferes with operation of the missile guidance system and is a problem that is minimized at low velocities by placing the control surfaces within the exhaust plume.
So-called “erodible” control surfaces have been developed that are placed in the path of rocket engine exhaust and break apart after a period of time. However, these often break apart in larger pieces than generally is acceptable. It would be desirable to avoid ejecting large pieces of material from the missile during launch and flight.
SUMMARY OF THE INVENTION
The present invention provides a thrust vector control jet vane, a jet vane control system and a missile incorporating such jet vanes, as well as a method of making such jet vanes. The jet vanes form aerodynamic surfaces for generating vehicle maneuvering forces by diverting the propellant plume at missile launch. As an aerodynamic control velocity is achieved and the aerodynamic control surfaces external to the vehicle airframe assume command authority, the jet vanes dissolve into granular particulates in the propellant plume. Therefore, rocket motor propulsion efficiency or specific impulse is not degraded beyond that required to perform launch maneuvers, reaction time is decreased, and the missile exhibits improved kinetic performance during the aerodynamic control phase of the powered flight to the target.
Dissolvable jet control vanes provide numerous advantages in the design, construction and/or performance of a missile. For example, dissolvable control vanes eliminate or minimize the often tortuous practice of determining the least desirable inefficiency to the overall missile system. The control vanes gracefully disintegrate in a timely basis, providing a disposable control vane for maneuvering the missile for pitch, yaw and roll control immediately upon launch. Rocket motor propulsion efficiency or specific impulse is not degraded beyond that required to perform the launch maneuvers, hence the missile exhibits improved kinetic performance during the powered flight phase to the target. Interception of highly mobile targets at an extended range is further enhanced by dissolvably jettisoning the control vanes after pitch-over. Ease of thrust vane control operation without the activation of pyrotechnic-actuated ejection mechanisms and greater reliability resulting from system simplification are additional advantages that also lead to cost and risk reduction.
Dissolvable control vanes are possible through the utilization of multiple advanced composite materials designed to perform different individual functions on a time limited basis, yet integrated or colaminated together to achieve a combined, pre-programmed structural capability by taking advantage of their known high temperature performance characteristics and environmental limitations. As a result, failure of the composite control vanes produced in accordance with the present invention can be precisely controlled in a manner unforeseen in prior “erodible” material designs. The composite dissolvable jet vanes also provide an inexpensive, disposable thrust vector control methodology for retrofitting high performance missiles for low speed surface launch applications with thrust vector control requirements.
The dissolvable jet vane provides a lightweight, reliable means of removing steering jet vanes from the exhaust stream of a solid rocket motor nozzle. The dissolvable jet vane materials withstand the pressure and thermal loads associated with missile steering during the first few seconds of rocket boost until the missile obtains sufficient speed to use conventional external aerodynamic control surfaces for steering control. Once control passes to the external fin, the jet vanes rapidly and uniformly dissolve in the exhaust stream.
According to one aspect of the invention, a dissolvable thrust vector control vane includes a frame and a thermal protection layer on at least a portion of the frame. In accordance with one embodiment of the invention, the dissolvable control vane further includes an erosion-resistant material on at least a forward edge of the frame. The erosion-resistant material forms an insert that is mounted to the forward edge of the frame; the insert includes a carbon-carbon structure and a surface coating on the structure selected from a group including a ceramic, a carbide, and a meta

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