Rocket exhaust plume signature tailoring

#The present invention relates to fuel-propelled vehicles and, more particularly, to internal methods and arrangements for tailoring rocket exhaust plume signatures of fuel-propelled vehicles.

#Fuel-propelled vehicles, such as rockets and missiles utilize rocket motors to propel the vehicle through air and space. The rocket motors general fall into three types, which are solid propellant motors, liquid propellant motors and hybrid propellant motors. Solid propellant motors utilize a solid fuel element or grain that is placed in a large solid combustion chamber. The solid fuel element or grain is usually bonded to the combustion chamber walls and burns away during flight. The liquid propellant motors employ liquid fuel tanks coupled to a fixed combustion chamber through one or more fuel lines. A hybrid propellant motor generally uses a fluid reactant (e.g., an oxidizer) to burn a solid fuel element or a fluid fuel element with a solid reactant, which are ignited in a combustion chamber.

#Typically, the combustion chamber is connected to a nozzle assembly regardless of the type of rocket motor being employed. The purpose of the nozzle is to provide thrust to the vehicle by accelerating the mass of the propellants (fuel and oxidizer). The nozzle can be a supersonic nozzle with a subsonic portion and a supersonic portion. The subsonic portion is connected to the combustion chamber, while the supersonic portion opens to the outside environment. The propellant is ignited in the combustion chamber producing gases moving at subsonic speeds. The gas is then accelerated to supersonic speed by the subsonic portion of the nozzle which decreases in diameter as the gas passes through the nozzle. The gas then reaches supersonic speed and enters the supersonic portion of the nozzle which increases in diameter as the gas passes through the nozzle and exits into the environment.

#FIG. 1 illustrates a partial cross-sectional view of a rocket system in accordance with an aspect of the present invention.

#FIG. 2 illustrates a partial cross-sectional perspective view of a rocket engine in accordance with an aspect of the present invention.

#FIG. 3 illustrates an example configuration of a cross-sectional view of a nozzle wall having generally trapezoidal shaped plugs in a nozzle liner in accordance with an aspect of the present invention.

#The present invention relates to internal methods and arrangements for tailoring rocket exhaust plume signatures of fuel-propelled vehicles. The fuel-propelled vehicle can be a self-propelled vehicle, such as a rocket or missile. Alternatively, the fuel-propelled vehicle can be a manned vehicle (e.g., spacecraft, aircraft, rocket powered automobiles). The tailoring of the rocket exhaust plume signature is accomplished by providing and locating at least one structure having materials and/or additives that modify the radiant intensity pattern or exhaust plume signature of the rocket exhaust plume upon the ablation or melting of the material and/or additive into the rocket exhaust plume.

#The materials and/or additives can be manufactured or incorporated into preexisting ablative materials that reside within a rocket nozzle and/or beyond a rocket nozzle throat location, such that the material ablates into the rocket exhaust plume during afterburning. The materials or additives can be provided into a nozzle ablative liner, such that the materials or additives ablate along with the liner, thus modifying the exhaust plume signature. Alternatively, the materials or additives can be coated or incorporated into jet vanes residing outside the nozzle exhaust exit. A material structure such as a ring can be fabricated and located inside the nozzle beyond the nozzle throat location, or located outside the nozzle exhaust exit. It is to be appreciated that other structures located within or near the exhaust plume during afterburning can be employed alone or in combination to carry out the present invention.

#The material or additives can be selected to provide a desired plume signature by providing the ablating structure with specific ablation rates. The ablation rates can be defined as the amount of plume signature modifying material that ablates into the plume over time to vary the effect of the plume signature modifying material on the radiant intensity of the plume over time. Plume signature profiles can be defined by selecting material configurations that define ablation gradients according to ablation rates. Therefore, plume signature profiles can be provided by varying any of material types, material compositions, material densities, material geometries and material ablation rates.