Variable Heat Rejection Device

Abstract

A heat rejection system that employs temperature sensitive shape memory materials to control the heat rejection capacity of a vehicle to maintain a safe vehicle temperature. The technology provides for a wide range of heat rejection rates by actuation of the orientation or position of a heat rejection panel which impacts effective properties of the heat rejection system in response to temperature. When employed as a radiator for crewed spacecraft thermal control this permits the use of higher freezing point, non-toxic thermal working fluids in single-loop thermal control systems for crewed vehicles in space and other extraterrestrial environments.

1 . A thermal energy radiator system, relating to a variable heat rejection, that controls the heat rejection capacity at least in part through articulation or shape change of a thermal energy radiator comprising:
 a) at least one thermal energy radiator structured and arranged to radiate thermal energy generated by at least one thermal energy source of at least one spacecraft into an external environment;   b) at least one thermal energy transport system structured and arranged to collect heat from at least one thermal energy source and transport said collected heat to said thermal energy radiator;   c) wherein said thermal energy transport system may transport heat through any typical means of heat transport including, but not limited to, thermal fluid flow and thermal conduction;   d) wherein said thermal energy radiator contains a facesheet structure which articulates or changes shape in response to the temperature of said thermal energy radiator, thermal energy transport system, or thermal environment;   e) wherein said thermal energy radiator articulation or shape change behavior comprises: at least one shape which has a high heat rejection capacity; and at least one shape which has a low heat rejection capacity, wherein the shape taken by the thermal energy radiator depends on temperature;   f) wherein said thermal energy radiator articulation or shape change behavior further comprises the selective obscuring and exposing, in whole or part, of thermal energy radiator surfaces to affect effective view factor; and   g) wherein said thermal energy radiator articulation or shape change behavior further comprises the selective obscuring and exposing, in whole or part, of high and low emissivity surfaces to affect effective emissivity.   
     
     
         2 . The thermal energy radiator according to  claim 1  wherein said thermal energy radiator articulation or shape change behavior further comprises:
 a) a shape or configuration that causes a reduced heat rejection in response to temperatures below at least one transition temperature; 
 b) a shape or configuration that causes an increased heat rejection in response to temperatures above at least one transition temperature; 
 c) wherein said articulation or shape change occurs due to temperature sensitive shape memory inherent to the material of at least one component of said thermal energy radiator; 
 d) wherein said articulation or shape change can occur without active control or the addition of any power other than the thermal power provided by the energy transport system or the thermal environment; 
 e) wherein said articulation or shape change to decrease heat rejection may occur multiple times, or continuously, as many times as temperature cycles from above to below the transition temperature of the change while in service; and 
 f) wherein said articulation or shape change to increase heat rejection may occur multiple times, or continuously, as many times as temperature cycles from below to above the transition temperature of the change while in service. 
 
     
     
         3 . The heat rejection system according to  claim 1  wherein said thermal energy radiator articulation or shape change behavior further comprises:
 a) the selective obscuring of thermal energy radiator surfaces when in a shape or configuration corresponding to reduced heat rejection; 
 b) the selective exposing of thermal energy radiator surfaces when in a shape of configuration corresponding to increased heat rejection; 
 c) wherein said thermal energy radiator surfaces may be obscured or exposed in whole or in part; 
 d) wherein the effective view factor or area of thermal energy heat rejection to the sink temperature is lower when in a shape or configuration corresponding to reduced heat rejection; and 
 e) wherein the effective view factor or area of thermal energy heat rejection to the sink temperature is higher when in a shape or configuration corresponding to increased heat rejection. 
 
     
     
         4 . The thermal energy radiator according to  claim 1  wherein said thermal energy radiator articulation or shape change behavior further comprises:
 a) the selective obscuring of thermal energy radiator surfaces having a high emissivity and exposing of surfaces having a low emissivity when in a shape or configuration corresponding to reduced heat rejection; 
 b) the selective exposing of thermal energy radiator surfaces having a high emissivity and obscuring of surfaces having a low emissivity when in a shape or configuration corresponding to increased heat rejection; 
 c) wherein said surfaces may be coated, covered, or otherwise treated to achieve the desired emissivity; 
 d) wherein said surfaces may be obscured or exposed in whole or in part; 
 e) wherein the effective emissivity of thermal energy heat rejection to the sink temperature is lower when in a shape or configuration corresponding to reduced heat rejection; and 
 f) wherein the effective emissivity of thermal energy heat rejection to the sink temperature is higher when in a shape of configuration corresponding to increased heat rejection. 
 
     
     
         5 . The thermal energy radiator according to  claim 1  wherein said thermal energy radiator comprises:
 a) at least one shape memory structure which exhibits two- or more shape memory states; 
 b) at least one shape memory structure which in a cold memory state has a shape roughly enabling the low heat rejection shape of the thermal energy radiator; 
 c) at least one shape memory structure which in a hot memory state has a shape roughly enabling the high heat rejection shape of the thermal energy radiator; 
 d) wherein the shape memory structure provides a force which acts upon the radiator structure at low temperature to cause the low heat rejection shape; and 
 e) wherein the shape memory structure provides a force which acts upon the radiator structure at high temperature to cause the high heat rejection shape. 
 
     
     
         6 . The thermal energy radiator according to  claim 1  wherein said thermal energy radiator forms a shape which comprises:
 a) a rough approximation of at least one flat shape with high heat rejection surface facing a cold heat sink above at least one transition temperature; and 
 b) a closed or partially closed flat shape with high heat rejection surface not facing a cold heat sink below at least one transition temperature. 
 
     
     
         7 . The thermal energy radiator according to  claim 2  wherein said thermal energy radiator may be actively controlled as needed by heating the shape memory material component of said thermal energy radiator. 
     
     
         8 . A heat rejection system wherein an array comprises at least one articulating or shape changing thermal energy radiator according to  claim 1  such that:
 a) each member of the array may be arranged in series in the energy transport system; 
 b) each member of the array may be arranged in parallel in the energy transport system; 
 c) wherein said array is composed of any combination of the above arrangements; and 
 d) wherein each thermal energy radiator of said array responds to temperature local to its place in the array. 
 
     
     
         9 . The heat rejection system according to  claim 8  wherein a fluid loop consisting of at least one thermal fluid which is capable of transporting heat transports heat from at least one source to each array member of said heat rejection system according to its place in said array of thermal energy radiators. 
     
     
         10 . The heat rejection system according to  claim 8  wherein a thermal radiation shield is located to cover gaps present in the cold shape at each end of a series arrangement of at least one thermal energy radiator such that the view of the thermal energy radiator's active surface to the external environment is blocked.