Abstract:
An example space-based power generation panel arrangement includes a first reflective panel and at least one heat pipe configured to communicate thermal energy to the first reflective panel and a second reflective panel. The heat pipe is configured to hinge the first reflective panel to the second reflective panel.

Description:
BACKGROUND 
     This invention relates to moveably securing reflective panel assemblies of a space-based power generation system. 
     As known, many space-based power generation systems utilize reflectors to direct solar energy. One type of power generation system uses reflectors to direct solar energy toward an arrangement of photovoltaic cells, which then produce power. Various types of devices utilize the produced power. 
     Some devices, such as radar and lidar devices, require relatively high levels of power. Space-based power generation systems responsible for powering these devices often incorporate concentrated photovoltaic cells to produce the higher levels of power. Managing thermal energy in the power generation systems that produce the higher levels of power is often difficult, especially in power generation systems having concentration ratios higher than 20 (i.e., 20 times the sun). The structures incorporated for thermal energy management also disadvantageously increase the mass and complexity of these power generation systems. 
     SUMMARY 
     An example space-based power generation panel arrangement includes a first reflective panel and at least one heat pipe configured to communicate thermal energy to the first reflective panel and a second reflective panel. The heat pipe is configured to hinge the first reflective panel to the second reflective panel. 
     An example space power generation assembly includes a plurality of reflective panels and a plate. A plurality of conduits are configured to communicate thermal energy between the plurality of reflective panels and the plate. Some of the plurality of conduits hingeably connect the plurality of reflective panels. 
     An example method of moveably securing reflective panel assemblies includes communicating thermal energy to a plurality of reflective panels using a conduit and hingeably connecting the plurality of reflective panels using the conduit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example reflective and radiating panel assembly. 
         FIG. 2  shows an example space-based power generation system incorporating a multiple of the  FIG. 1  panel and powering an example device. 
         FIG. 3  shows example positions of  FIG. 2  system as the system moves from a stowed position to a deployed position. 
         FIG. 4  shows a top view of the  FIG. 2  system in a deployed position. 
         FIG. 5  shows a section view at line  5 - 5  of  FIG. 4 . 
         FIG. 6  shows a section view at line  6 - 6  of  FIG. 4 . 
         FIG. 7  shows a section view at line  7 - 7  of  FIG. 4 . 
         FIG. 8  shows a bottom view of the cold plate portion of the  FIG. 2  system. 
         FIG. 9  shows a heat pipe of the  FIG. 2  system. 
         FIG. 10  shows a section view at line  10 - 10  of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an example reflective and radiating panel assembly  10  includes a reflective layer  14 , a base portion  18 , and a plurality of heat pipes  22 . The reflective layer  14  is secured adjacent an upper surface  26  of the base portion  18 . The heat pipes  22  are secured adjacent a lower surface  30  of the base portion  18 . A plurality of side surfaces  32  span between the upper surface  26  and the lower surface  30 . The side surfaces  32  are dimensionally smaller than the upper surface  26  and the lower surface  30 . 
     The example reflective layer  14  includes a plurality of concentrating elements  36  that provide the panel assembly  10  with a multifaceted reflecting surface. The concentrating elements  36  project about 0.3-0.5 mm from the surrounding surface of the generally planar reflective layer  14 . The example concentrating elements  36  have a low areal density. 
     In this example, the plurality of the heat pipes  22  are mounted to the lower surface  30  of the base portion  18  of the panel assembly  10 . The heat pipes  22 , a type of conduit, are configured to carry thermal energy to panel assembly  10 . The panel assembly  10  facilitates radiating the thermal energy carried by the fluid within the heat pipes  22  to the space environment. In this example, the panel assembly  10  is referred to as a Radflector™ because of the combination of reflecting and radiating properties. 
     Referring to  FIG. 2 , a space-based power generation system  38  and a second space-based power generation system  46  power a spacecraft bus device  42 . In this example, the power generation systems  38  and  46  are shown in a deployed position in a space environment, which is a position appropriate for generating power. 
     In this example, the power generation systems  38  and  46  include multiple panel assemblies  10 , which form a solar concentration subsystem for the power generation systems  38  and  46 . The power generation systems  38  and  46  also each include multiple reflector sheets  50 . Notably, the reflector sheets  50  lack the heat pipes  22  and the base portion  18  of the panel assemblies  10 . 
     The panel assemblies  10  and reflector sheets  50  are circumferentially arranged about a cold plate  54 . An array of photovoltaic cells  58  is disposed on the cold plate  54 . The reflector sheet  50  and the reflective layer  14  of the panel assemblies  10  direct solar energy to a secondary reflector  62  above the cold plate  54 . The secondary reflector  62  is generally planar, but has a slight hyperbolic reflecting surface that directs the solar energy downward toward the arrangement of photovoltaic cells  58 , which then utilize the solar energy to generate power. The solar energy and power generation results in high levels of thermal energy near the cold plate  54 . The array of photovoltaic cells  58  comprises concentrated photovoltaic cells in this example. 
     The power generation systems  38  and  46  transmit the generated power to the spacecraft bus device  42 . An electric propulsion system  66  propels the on-orbit spacecraft  42  using the generated power from the power generation systems  38  and  46 . 
     Referring to  FIG. 3 , the power generation system  38  is launched into space in a stowed position  70 . In this example, the panel assemblies  10  and the reflector sheets  50  are folded when the power generation system  38  is in the stowed position  70 . The panel assemblies  10  and the reflector sheets  50  unfold as the power generation system  38  moves to a deployed position  74 . 
     Referring to  FIG. 4 , an area of the power generation system  38  bounded by a dashed line  78  includes the panel assembles  10 , the reflector sheets  50  are outside area bounded by the dashed line. As shown, the heat pipes  22  extend radially from the cold plate  54 , to radially inner panel assemblies  10   a , and then to radially outer panel assemblies  10   b.    
     In the deployed position  74 , the concentrating elements  36  of the panel assemblies  10  and the concentrating elements  36  of the reflector sheets  50  are arranged in concentric rings, which facilitate reflecting solar energy toward the secondary reflector  62 . The panel assemblies  10  and the reflector sheets  50  together provide a Fresnel reflector. 
     As can be appreciated from the Figures, the reflective layer  14  of the panel assemblies  10  are aligned in the same plane when the power generation system  38  is in the deployed position  74 . The plane established by the reflective layer  14  of the panel assemblies  10  is aligned with the secondary reflector  62  in this example. In this example, an upper surface of the reflector sheet  50  is about 1.7 m by 1.7 m, which is about the same size as the reflective layer  14  of the panel assemblies  10 . The example reflector sheets  50  include a reflective portion comprising an aluminized Kapton® polyimide film. 
     Referring to  FIG. 5  with continuing reference to  FIGS. 3-4 , a plurality of mechanical hinges  82  secure the reflector sheets  50  relative to the panel assemblies  10 . The mechanical hinges  82  enable pivoting movements of the reflector sheets  50  relative to the panel assembly  10 , which facilitates moving the power generation system  38  from the stowed position  70  to the deployed position  74 . 
     Referring to  FIG. 6 , the panel assembly  10   a  is hingeably connected to the panel assembly  10   b  through the heat pipes  22 . In this example, the heat pipes  22  include a flexible hose portion  86  that facilitates hingeably moving of the panel assemblies  10   a  and  10   b  relative to each other. In this example, the flexible hose portion  86  permits single-degree-of-freedom motion of the panel assembly  10   a  relative to the panel assembly  10   b . The example flexible hose portion  86  thus allows the panel assembly  10   a  to fold over on the panel assembly  10   b  while limiting sideways movement of the panel assemblies  10   a  and  10   b  relative to each other. Because the heat pipes  22  enable movement between the panel assemblies  10   a  and  10   b , no additional hinges structures are needed between the panel assemblies  10   a  and  10   b.    
     The reflective layer  14  of the panel assemblies  10  is about 0.076 mm thick aluminized Kapton® polyimide film, for example, and the base portion  18  is a graphite-epoxy panel that is about 0.254 mm thick. 
     Referring to  FIGS. 7-9 , the panel assembly  10   a  is hingeably connected to the cold plate  54  through the heat pipes  22 . In the deployed position shown, the panel assembly  10  is aligned within the same plane as the cold plate  54 . In a stowed position, the panel assembly  10  is stored approximately at a 90° angle relative to the cold plate in a position aligned with line  94 . 
     A person having ordinary skill in this art, and having the benefit of this disclosure, would understand how to move the panel assemblies  10  and the reflector sheets  50  from the stowed position  70  to the deployed position  74  utilizing the mechanical hinges  82  and the flexible hose portion  86  of the heat pipes  22 . Motors (not shown) are used in one example to move the panel assemblies  10  and the reflector sheets  50 , as well as the secondary reflector  62 , from the stowed position  70  to the deployed position  74 . 
     The example heat pipes  22  are thermally coupled with the cold plate  54  to facilitate thermal energy transfer between the cold plate  54 , the heat pipes  22 , and the panel assemblies  10 . A thermal spread  98  separates the heat pipes  22  thermally coupled within the cold plate  54  from other groups of the heat pipes  22  that are in a different radial position relative to the cold plate  54 . The heat pipes  22  form part of the thermal energy rejection subsystem of the power generation systems  38  and  46  ( FIG. 2 ). 
     In this example, the diameter of the heat pipes  22  are about 13.7 mm, and the wall thickness is about 0.0254 cm. The heat pipes  22  include a portion embedded within the cold plate  54  that is about 0.25 m-0.85 m long. The flexible hose portion  86  of the heat pipes  22  is about 0.2 m long, and the portions of the heat pipes  22  secured to the panel assemblies  10  is about 1.7 m long. 
     Referring to  FIG. 10 , twelve of the heat pipes  22  are thermally coupled to each of the panel assemblies  10 . 
     Features of the disclosed examples include utilizing a common support structure, motors, and hinging features to deploy a solar concentration subsystem and a thermal energy rejection subsystem. Another feature is an optical configuration that utilizes low area density Fresnel optical elements combined with a secondary concentrator to concentrate solar flux on a photovoltaic array. Yet another feature includes a multifaceted primary reflecting surface and a hyperbolic secondary reflecting surface that together provide a highly compact, defocused image providing increased tolerance for pointing and tracking errors. Yet another feature includes a power generation system that produces 130 W/kg of power, that can be scaled from 20-80 kWe. 
     Although a preferred embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.