Abstract:
Modular thermal truss plates carry heat in multiple directions. Framing around an array of flat heat pipes provides mechanical and thermal connections to other truss plates, and a base, such as a satellite, thereby supporting thermally active equipment. Walls sandwich banks of flat heat pipes and may bond to a honey comb, metal core conducting heat between multiple walls. Each bank of flat heat pipes passes heat best in one direction, and may be formed of corrugated copper sheets spaced apart by a metal mesh, such as an expanded metal or screen, also stamped or otherwise formed into a corrugated configuration. Joining methods (e.g., brazing, soldering, etc.) increase stiffness, pressure containment, and strength, by binding the two layers of metal sheet to one another.

Description:
RELATED CASES 
     This application is a continuation of co-pending U.S. patent application Ser. No. 13/468,335, filed May 10, 2012, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/484,888, filed May 11, 2011, both of which are incorporated herein by reference. 
    
    
     RIGHTS OF U.S. GOVERNMENT 
     The invention was made with Government support under Contract FA9453-10-C-0053 awarded by the United States Air Force. The Government has certain rights in the invention. 
     The U.S. Government may have certain license rights in this invention and the right in limited circumstances to require the patent owner to license others on reasonable terms as provided for by the terms of Contract No. FA9453-10-C-0053 awarded by DOD/USAF, and may be subject to ITAR in accordance with said contract. 
    
    
     BACKGROUND 
     1. The Field of the Invention 
     This invention relates to heat transfer and, more particularly, to novel systems and methods for heat transfer through flat heat pipes covering large areas with respect to their length. 
     2. The Background Art 
     Heat transfer is the mechanism by which refrigeration systems maintain a cool region within a hotter region. Heat transfer is also the mechanism by which energy is carried from points of generation such as furnaces and the like to areas to be heated, such as materials, space heating, or the like. Heat transfer is driven by a difference in temperature between a material at a comparatively higher temperature driving energy to a material (e.g., location or object) at a lower temperature to receive that energy. In all cases of heat transfer, the temperature difference between the high temperature region or object and the lower temperature region or object is a driving potential for the transfer of heat, whether linear or non-linear in effect. 
     Typically, heat transfer deals with the resistance to heat transfer through various materials, spaces, and so forth. The study of radiation, conduction, and convection seeks to identify the controlling parameters that govern the relationship between the temperature differences, heat transferred, material properties, distances, areas, and the like. Thus, in general, it is desirable to minimize the thermal resistance in order to maximize heat transfer from a region of higher temperature to a region of lower temperature. Similarly thermal resistance is to be maximized in order to minimize heat transfer. To the extent that thermal resistance is reduced, more heat may be transferred with a comparatively lesser temperature difference. 
     Electrical equipment has always required consideration of heat transfer to remove the heat generated by electrical resistance losses. Likewise, in systems such as satellites, spacecraft, and the like, the importance of maintaining low temperatures in certain equipment, such as sensors creating or recording images, and the like may require unique combinations of temperatures and thermal resistance. 
     Meanwhile, mechanical connections and distances required to remove heat may be substantial. Moreover, structural requirements for mechanical support may be substantial, requiring support against the ‘g-forces’ or acceleration forces of launch and other movements. In fact, heat transfer and mechanical support are often at odds, wherein what is good for one is poor for the other. The result is tradeoffs that poorly serve one or both. 
     Finally, space is not without traffic of particles and various objects, within a broad range of sizes, from dust to satellite to asteroid sizes. These may be either naturally occurring or man-made. Space junk, small meteoric objects, and other projectiles may penetrate a surface of a satellite, permanently disabling mechanical, fluid, electrical, and other systems contained therein. 
     Thus, it would be an advance in the art to develop a more effective heat transfer system, particularly one that would be adaptable to satellite use, having much lower weight than earthbound and previous satellite systems. It would be an advance to provide reduced thermal resistance, permitting temperature differentials less than are presently known in the art of satellite, and even less than those of many earthbound systems. 
     It would be a further advance in the art to create a comparatively strong structural support system, compared to prior art systems of equivalent weight in satellites and earthbound systems. It would be a further advance if such as system would support robust heat transfer, having comparatively better heat flux per degree of temperature differential than prior art satellite systems of comparable weight. 
     It would be a yet further advance to provide redundancy against failure in cases of mechanical damage, such as penetration by space debris or other objects. This could be significantly more valuable than earthbound systems, where such protection is not required at comparable weights to those of satellites. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, in accordance with the invention as embodied and broadly described herein, a method and apparatus are disclosed in one embodiment of the present invention as including modular thermal truss plates that may be configured to carry heat in multiple directions. Meanwhile, a combination of framing around a central lay up of such a plate or panel may provide mechanical or thermal connections to other plates, and to a structure, such as a satellite frame, needing to support thermally active equipment such as electrical equipment. 
     In certain embodiments, walls, formed of skins (either composite layers or metal) sandwiching a flat thermal heat pipe or several flat thermal heat pipes therein may be combined by bonding them to a honey comb, metal core. The core conducts heat between multiple walls. Each of the walls, being a sandwich of an external skin layer on each side of a bed or bank of flat heat pipes capable of passing heat excellently in one direction. 
     By placing each of the walls in a bonded relationship sandwiching the thermal core, such that each of the walls has a preferential heat transfer direction orthogonal to the other, heat may be transferred in three dimensions. Heat may transfer in and out of a wall. Heat may pass along the heat pipes of one wall. Heat may pass through the conducting core to the opposite wall. Heat may then be conducted in a preferential direction orthogonal to that of the first wall. 
     By providing multiple flat heat pipes in each wall, and by providing opposite walls having preferential heat transfer directions orthogonal to one another, the apparatus or truss plate may be particularly robust and resistant to single point failures. It may function, although at a limited performance if one of the heat pipes fails or is damaged. In certain embodiments, the truss plate-heat pipes may be connectable to one another to create larger expanses. Thermally conductive framing materials may provide excellent thermal conduction between adjacent truss plates. 
     Each truss plate-heat pipe may be formed of corrugated copper sheet spaced from an opposite piece of corrugated copper sheet by a mesh, such as an expanded metal or screen material that is stamped or otherwise formed into a corrugated screen. Thus, the corrugated screen or mesh spaces apart the corrugated metallic (e.g. copper), or possibly polymeric, corrugated sheets. Meanwhile, appropriate joining methods (e.g., brazing, soldering, etc.) may bond corrugated mesh material to corrugated sheets in order to form a truss panel that has substantially increased stiffness and strength. The mesh binds the two layers of metal sheet to one another to support higher internal pressures. Thus, dimensional stability results, providing for pressure and temperature variations. Meanwhile discreet spaces exist for the traveling of a working fluid liquid phase, such as water or other liquid therealong. In a direction opposite travels a vapor phase of the working fluid through adjacent vapor spaces. 
     Typically, the vapor spaces are comparatively larger, and are located in the center between the trussed pair of adjacent copper or other metal sheets. Meanwhile, the mesh material also serves to support capillary action within the corrugations of the metal sheets. Also, larger spaces provided by the corrugated mesh provide vapor spaces between the metal sheets to pass vapor phase operating fluid in a direction opposite that of the motion of capillary action of the liquid phase of the operating fluid. 
     Some of the benefits of apparatus and methods in accordance with the invention include higher pressures for operation of the flat truss plate-heat pipe. 
     Because the individual walls or panels are compartmentalized, they are less vulnerable to damage or individual failure and may be positioned with clearances therebetween to support hardware connections by fasteners penetrating through the lay up of the thermal strips. 
     Improved manufacturability results from the use of materials that can be readily manufactured for the sheets, the mesh, the closure portions forming the walls between the sheets, and so forth. 
     Testing by modeling has been done for heat transfer rates across a thermal control panel formed of multiple truss plate-heat pipes in a first thermal control panel, bonded to a honey comb core, to another thermal control panel, in order to transfer heat across a sandwich thermal control panel. Heat transfer has been analyzed from one edge of a sandwich thermal control panel through to an opposite edge of the same panel and from within the panel to an adjacent edge. In both cases, temperature differences, and therefore effective thermal conductivity through the truss plates has shown to be very favorable. 
     By forming the truss plate heat pipe in banks, embedding each bank in a thermal control panel, and then bonding those panels together through a lightweight metal core, improved pressure support, frequency response to vibration, temperature limits across the panels, tolerance to failure, static load support, proof pressure, burst pressure, and vacuum support against leakage, have all shown to be very favorable for extremely demanding applications. 
     It has been determined that outgassing within the truss plate heat pipe may be minimized to meet very stringent requirements, in accordance with the invention. Cleaning, design life, mechanical and thermal interfaces, and mass totals appear to be within a reasonable range. The electrical connection and grounding requirements appear to be easily tractable. 
     Edge connection temperature differentials between sandwich thermal control panels adjacent to one another on or within a structure have shown to be well within operational values for many applications in terrestrial and space applications. Moreover the conducting frames in which the truss plates are mounted may also be readily conducting to assure heat transfer to and from the panels. 
     Meanwhile, structural stiffness of the sandwich thermal control panel is substantial Due to the stiff thermal control panels bonded to the control honey comb structure. Clearances at the intersections of the truss plate heat pipes provide locations for penetrations through each panel in order to mount hardware there against. Thus, mechanical support as well as thermal support are provided in a single panel for mounted hardware. 
     Current thermal computer models, using the dimensions and properties of the materials of the panels, demonstrate that temperature differentials across one truss plate may be as little as 4.5 degrees kelvin, and less than 3.5 degrees on a mounting surface given a 56 W heat load. Similarly, the temperature drop between adjacent, interconnected panels has been demonstrated to be less than 2.5 degrees kelvin for the same heat loading. 
     In some embodiments, truss plate heat pipes in accordance with the invention may operate across a range from about −40 degrees Celsius to about 75 degrees Celsius and above with a single working fluid, and a single structural design. Accordingly, the specific thermal conductivity of a truss plate in accordance with the invention appears to be on the order of greater than 1 watt per meter degree kelvin per kilogram per cubic meter, with a specific stiffness on the order of greater than 13 megapascals per kilogram per cubic meter. This compares very favorably to other conventional materials, including aluminum, beryllium, copper, and the like. Thus, the specific thermal conductivity is better than that of pure metals, of comparable specific stiffness. 
     In certain presently contemplated embodiments, a composite, or metal material at the outermost surface of each wall may be on the order of 30 thousandths of an inch, with copper corrugated to have a total thickness on the order of 66 thousandths. The vapor space typically takes about 100 thousandths. Thus, the total wall thickness is on the order of 232 thousandths. A 0.5 inch thickness of honey comb core is oriented to conduct heat along the lengths of the honey comb cavities between a pair of walls. The honey comb core is bonded by a thin layer of partially cured or B-stage polymer such as a B-stage epoxy positioned between the innermost surface of one wall and the honey comb core. Likewise on the opposite side of the honey comb core a thin layer, on the order of about 5 thousandths thickness, bonds the honey comb core to the opposite wall. 
     As a means to maintain the structural and thermal performance of each thermal truss heat pipe, the corrugations on the outside thereof (e.g., the face thereof that contacts the composite skin on the respective wall) may be filled with a suitable polymer. It has been found that a polymeric material may be smeared in and screeded off to fill the furrows or grooves in the outside surface of the corrugated metal sheet. 
     In one embodiment, 110 copper is used in 3.35 inch widths and corrugated to sandwich within two such sheets a quantity of copper mesh. The overall thickness of the thermal strip formed of the copper spaced apart by copper mesh is typically on the order of 0.170 inch total thickness. These chambers or thermal strips may be formed in lengths suitable for extending across a particular truss plate. In one configuration, 20.8 inch lengths are suitable for the longer modules. A 12.5 inch length is suitable for those near the edges, which must provide clearance for openings handling cables and other lines that must pass through the panel. 
     The sandwich thermal control panels each include two walls, each wall having two skins. Between each pair of skins being a truss plate heat pipe, or rather several truss plate heat pipes laid out side by side. Each of those truss plate heat pipes, since it is corrugated, relies on an end wall or end rail fitted to the corrugated shape and brazed to seal the end of the truss plate heat pipe. 
     Likewise, side walls or side rails fit into the outermost or near by corrugation of each metal sheet in order to be brazed or otherwise bonded to seal the side edges or lateral edges of each of the thermal strips. An aperture in the end wall or end rail receives a tube that may be brazed thereinto in order to act as a vacuum port for evacuating and filling each of the truss plate heat pipes after fabrication. 
     In order to provide improved dimensional stability, truss plate heat pipe modules are provided along with spacer material on the outer skin. This provides spacing in the region between adjacent truss plate heat pipes, and in regions of the panel extending outside of the truss plate heat pipes, such as at the corners of the lay up that will form each wall of the thermal control panel. 
     The skins may be formed of a prepreg fabric, such as a 140 GSM plain weave carbon fabric. One suitable material is the M55J material from Toray. This has a strength over 580 KSI and a modulus of elasticity of about 78 MSI. The skins may also be metallic. Framing for the truss plate may be made using aluminum extrusions or castings such as may be fabricated from 6061 aluminum or other thermally conductive metallic material. These may be formed to mate with the lay up of two walls bonded to a core. The intimate contact for thermal and mechanical purposes provides a structurally sound and thermally effective sandwich thermal control panel. 
     In certain embodiments, the truss plate may be provided with fasteners formed through the lay up, thus penetrating both walls and the intermediate core. Typically, the spacing there between is on the order of 10 cm in order to accommodate the width of each thermal strip. Meanwhile, in the orthogonal direction, the spacing may be about 5 cm or other suitable dimension. Accordingly, fasteners, such as bonded rivets, bolts, screws, or the like may be used to connect devices to the thermal control panel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects and features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
         FIG. 1  is a perspective exploded view of one embodiment of a sandwich thermal control panel in accordance with the invention; 
         FIG. 2  is the perspective view of the assembled apparatus of  FIG. 1 ; 
         FIG. 3  is a top plan view thereof, the thermal control panel being in a horizontal orientation; 
         FIG. 4  is an end elevation schematic view of the lay up portion of the truss plate heat pipe, combined into the sandwich thermal control panel of  FIG. 3 ; 
         FIG. 5  is a schematic view of the end cross sectional view of a thermal control panel lay up of  FIG. 4 ; 
         FIG. 6  is an end elevation view of the truss plate heat pipe, corrugated to form the outer layers of each truss plate heat pipe, and showing the wall rails interconnected therebetween; 
         FIG. 7  is an end elevation view of a truss plate heat pipe of  FIG. 6 , having the corrugated mesh installed between the layers of the corrugated metal; 
         FIG. 8  is a cutaway, perspective view of one embodiment of the corrugated metal sheets, partially cut away to show one embodiment of a metallic mesh spacing apart the metal sheets; 
         FIG. 9  is an exploded view of a truss plate heat pipe showing the principal components that are brazed together to form a sealed truss plate heat pipe; 
         FIG. 10  is a perspective view of a portion of the assembly that forms a truss plate heat pipe; 
         FIG. 11  is a perspective view of the end wall and side wall of the assembly of  FIG. 10 ; 
         FIG. 12  is a perspective view of the end and side walls of  FIG. 11  assembled together; 
         FIG. 13  is a perspective view of the assembled truss plate heat pipe of  FIGS. 6-12 ; 
       FIGS.  14 A, 14 B are a perspective views of alternative embodiments of an array of truss plate heat pipes assembled together; 
       FIGS.  15 A, 15 B are a top plan views of the arrays of truss plate heat pipes of FIGS.  14 A, 14 B, respectively; 
       FIGS.  16 A, 16 B are an end elevation views corresponding to FIGS.  14 A, 14 B, respectively; 
         FIG. 17  is a perspective view of a portion of a truss plate heat pipe showing the position of the screeded polymer filling in the corrugations, and the bonding layers to secure the strip later to the outer skins and spacer core; 
         FIG. 18  is a perspective view of one corner of a sandwich thermal control panel in accordance with the invention, illustrating the framing, rails forming the framing, and the lay up as seen near one of the service apertures therethrough; 
         FIG. 19  is an end elevation view of the angled edge rail of a sandwich thermal control panel in a position to be connected to a corresponding rail of an adjacent sandwich thermal control panel shown are two thermal control panels spaced with honey comb attached to the metal frame; 
         FIG. 20  is a top plan view of a sandwich thermal control panel in accordance with the invention illustrating the modeled isothermal lines of heat transfer in transferring heat from one side or edge across the truss plate to the opposite edge, wherein top and bottom walls are made of arrays of truss plate heat pipes oriented orthogonal to one another and connected by aluminum honey comb bonded thereto and therebetween; 
         FIG. 21  is a top plan view of the isothermal lines for a different heat transfer orientation test modeled for the sandwich thermal control panel for heat added at one edge and extracted from an adjacent edge; 
         FIG. 22  is an end elevation view of corrugated mesh truss structure of the flat heat pipe such as that illustrated in  FIGS. 8-9 ; 
         FIG. 23  is a perspective view thereof, wherein the rear end of the truss structure mesh is tilted upward to show more of its linear extent; and 
         FIG. 24  is a top plan view of the truss structure mesh of  FIGS. 22-23  in one embodiment thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     It will be readily understood that the components of the present invention, as generally described and illustrated in the drawings herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented in the drawings, is not intended to limit the scope of the invention, but is merely representative of various embodiments of the invention. The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. 
     The basis of the invention is the truss plate heat pipe,  10 . This unit provides the primary means for spreading heat. The internal mesh truss structure rails, and end fittings,  9 ,  10 ,  11 ,  12  combine to make the structurally and thermally capable truss plate heat pipe. In one presently contemplated embodiment, an apparatus  10  may include rails  11  such as a top rail  12   a , bottom rail  12   b , a joining rail  14  and an opposite joining rail  16 . In general, these may all be referred to as rails  11 , or may be referred to individually in their specific roles as rails  12   a ,  12   b ,  14 ,  16 . 
     Referring to  FIG. 1 , while referring generally to  FIGS. 1-24 , an apparatus and method in accordance with the invention may include a survivable, modular, combined thermal truss plate  10 , also referred to as an apparatus  10 . 
     In one currently contemplated embodiment, a thermal control panel  17  or apparatus  17  formed to be survivable, modular, and combined thermal and mechanical in nature and function, may rely on a small core  5 . Typically, in one presently contemplated embodiment, the core  5  is formed of a honey comb shaped material formed by bonding sheets of aluminum to one another and then drawing them apart to form the honey comb structure. 
     Typically, a layer of bonding material, such as a B-staged epoxy material, thermoplastic, thermoset plastic, or the like may be spread on one side of a skin  17 . The core  5  may then be bonded to the skin  17 . Opposite the first thermal control panel  19 ,  20  a second wall may be bonded likewise to the core  18 . Together, the two skins and their intervening small core  5  form a lay up  5 . The lay up is the internal portion of the truss plate  10 . 
     The external portion, or the edge portion, of the sandwich thermal control panel  2  is a frame  24 . The frame  24  is formed of the various rails  11 , and specifically a top rail  12   a , bottom rail  12   b , edge rail  14 , and another edge rail  16  opposite the first edge rail. These rails  11  are fastened together and to the lay up  22  to form a frame  24  around the lay up  22 . The rails  11  may be attached by fasteners to one another to form the frame  24 . Thus, the frame  24  with its contained lay up  22  provides thermal heat transfer properties and mechanical stiffness and strength properties suitable for the combined functions of thermal management and mechanical support. For example, strength, distortion, displacement, vibration frequency response, and the like may all be controlled by the combination of the truss plate heat pipe lay up  22  and frame  24  forming the sandwich thermal control panel  10 . 
     Each sandwich thermal control panel  10  may be provided with apertures  26  for passing wires, cables, material transport lines, tubes, and so forth through the truss plate  10 . Thus, devices operating exterior or on either side face of the sandwich thermal control panel  10  may exchange data, electric power, fluids, or the like with other devices or components on the opposite side of the sandwich thermal control panel  10 . Thus, the apertures  26  may be referred to as access apertures  26  for lines and other service members to pass through. 
     One of the functions of a sandwich thermal control panel  10  is to support devices structurally. Accordingly, an array of holes  28  may penetrate through an individual wall  20 , or even through the entire lay up  22 . Fasteners such as screws, bolts, rivets, bonded rivets, or the like may penetrate through the mounting apertures  28 , or simple apertures  28 , in order to fasten any device or component to the lay up  22 . Thus, the sandwich thermal control panel  10  performs as a structural mounting substrate for devices connected at the apertures  28 . 
     The thermal control panels  20  contain other components performing two-phase fluid heat and mass transport processes. Accordingly, the interiors must be evacuated through tubes  30 . Typically, the tubes  30  are metallic and brazed to metallic internal components of the lay up  22 , and specifically inside the walls  20 . The tubes may extend out through the frame  24  in order to provide access for evacuation. After evacuation, followed by refilling with a two-phase working fluid, the tubes  30  may be crimped and cut off in a single cold-welding, crimping process. 
     Meanwhile, each of the rails  11  may be provided with an outer flange  32  on each side thereof. The flanges  32  are positioned to capture the thermal control panels  20  therebetween. Likewise, a spacer  34 , which may also operate as a flange  32 , is sized to fit between adjacent thermal control panels  20  of a single sandwich thermal control panel  10 . Thus, the distance between each flange  32  and adjacent spacer  24  is sized to receive and bond therein a thermal control panel  20  of the lay up  22 . 
     In certain embodiments, it may be structurally advantageous to form gussets  36  at certain locations on each rail  11 . Gussets  26  provide structural strength and improved section modulus in order to support fastening of the frame  24  to an underlying structure, such as a satellite, a frame, an electrical box, or the like, as well as serving to connect various rails  11  to one another in adjacent sandwich thermal control panel  10 . For example, in the illustrated embodiments, gussets  36  may be formed between orthogonal, plate-like ears  39  or attachment extensions  39  of each rail  11 . 
     The apertures  38  formed in a particular rail  11 , such as the rails  12 ,  14 ,  16  may receive fasteners to mount the sandwich thermal control panel to another device or to another sandwich thermal control panel  10 . These apertures  38  may result in fasteners secured therein applying forces to the rails  11 . Resisting those forces requires increased section modulus, depending on the values of those forces, and thus the gussets  36  may maintain the “ear portions”  39  in fixed and rigid relation with respect to one another. 
     Referring to  FIGS. 1-3 , one may contemplate the thermal and modular character of a sandwich thermal control panel  10 . In one manner of speaking, the sandwich thermal control panel  10  is formed as a sandwich structure having two thermal control panels  20  spaced apart by a honey comb core  18 , thus improving the section modulus thereof against bending moments. On the other hand, the sandwich thermal control panel  10  also has additional structure inside each thermal control panel  20 . That is, each thermal control panel  20  has a truss plate heat pipe for transferring heat. Polymers are not the best heat transfer media. Metals are typically superior to most polymers. However, combined convection processes and conduction processes together here can improve even polymers over conductivity of heat through solid metals such as aluminum and copper, which have comparatively higher thermal conductivities than many other structural metals. 
     Referring to  FIGS. 4-5 , while continuing to refer generally to  FIGS. 1-24 , a truss plate heat pipe  40  operates as a heat pipe. Typically, a heat pipe operates with a wick transporting a liquid phase of a working fluid in one direction. Meanwhile, a channel transfers vapor phase quantities of the working fluid back through to the opposite extremities of the heat pipe. 
     In the instant embodiment, each truss plate heat pipe  40  may include a spacer core  42  assembled on or in each wall  20 . The spacer  42  operates something as a template and spacer to space apart the outer skins  44 . 
     The sheets  44  are corrugated, and may typically be formed of an excellent thermal conductor such as copper. Meanwhile, the outer skin  46  of the wall  20  is a composite material. Thus, between two outer skins  46 , is a truss plate heat pipe  40 . A skin  46  serves as a structural strength component on each side of the truss plate heat pipes  40  formed of copper sheets  44  or other sheets  44  of some other metal, polymer, or the like. 
     A skin  46  formed of suitable material may be laid down and a spacer  42  may be placed thereon. The spacer  42  has portions in which its own material, typically a polymer or honey comb, is placed, and other places, locations, or regions where there is a partial or total evacuation or lack of material. In these evacuated or empty portions, are placed the strips  40  formed of pairs of sheets  44 . 
     Between pairs of sheets  44 , a vapor space  48  or simply a space  48  provides a region for passage of the vapor phase of a working fluid captured within the strip  40  formed by adjacent pairs of sheets  44 . 
     One may note that the upper thermal control panel  20  contains a truss plate heat pipe  40 . Likewise, below, the edges of the truss plate heat pipes  40  are not shown, but simple terminate schematically at the spacer  42 . However, the edges of adjacent sheets  44  in a particular strip  40  are indeed bonded together as will be described hereinafter. However, the orientation of the bottom set or bank of strips  40  is orthogonal to the orientation of the bank of truss plate heat pipes  40  on the opposite side of the inner core  18 . Thus, heat transfer may occur much more readily along the length of a truss plate heat pipe  40  than crossways across the width thereof. The spacers  42  create effective thermal resistances or thermal gaps between adjacent strips  40 . 
     Referring to  FIG. 5 , while continuing to refer to  FIGS. 4-5 , and  FIGS. 1-24  generally, a single thermal control panel  20  is shown schematically with the stack up of outer skins  46  and inner truss plate heat pipes  40 , formed of exterior sheets  44  enclosing a vapor space  48 . 
     Referring to  FIGS. 6-8 , while continuing to refer to  FIGS. 1-24 , the sheets  44  are spaced apart by a mesh  50 , such as expanded metal, screen, or the like. The mesh  50  is formed to also present a corrugated aspect creating the vapor spaces  48  therein. Meanwhile, the mesh  50  spaces apart the corrugated sheets  44  in order to provide additional truss-like strength at reduced weight. 
     The mesh  50  at the locations where it contacts the sheets  44 , at their internal extremities of their corrugations, also defines the liquid space  52  or the spaces  52  carrying liquid. Thus, the vapor spaces  48  carry vapor in one direction, from a comparatively hotter region where the vapor is formed, back to the opposite end or elsewhere of each strip  40 , where the comparatively cooler temperatures condense the vapors in the vapor space  48  to liquid. The liquids, then move by capillary action through the spaces  52 , returning to be vaporized again at the comparatively hotter end of the truss plate heat pipe  40 . 
     As a practical matter, the sheets  44  may be brazed together by placing walls  54  or rails  54  captured within the last, or near the last corrugation within each sheet  44 . The rails  54  or walls  54  are sized to fit within the corrugation dimensions where they may be bonded by brazing or the like. It has been found that a silver and copper eutectic operates as a suitable brazing material, drawing into the small spaced between the mesh  50  and sheets  44  when melted. 
     Likewise, the ends of the truss plate heat pipes  40  need to be sealed. Each truss plate heat pipe receives an end wall  56  or rail  56  fabricated to match the shape of the corrugated sheets  44 . Thus, the end walls  56  are fitted in between the sheets  44 , within the internal corrugations or cavities of each of the sheets  44 , where these rails  56  also may be brazed. 
     Referring to  FIG. 9 , the rails  54  may be provided with a portion  55  or handle  55 . The handle portion  55  may simply be a continuation of the rail  54 , bent at an angle in order to provide a cranking or leverage advantage in order to manipulate each rail  54  into position. 
     By grasping the handle portion  55 , a technician may place each rail  54  within the corrugation where it must fit, and also rotate it or manipulate it in order to engage the rail  54  with the corrugation of the sheet  44  opposite. Thus, for example, one may place the rail  54  in the outermost corrugation of the bottom sheet  44   b , and then manipulate the handle  55  fit the rail  54  into the outermost corrugation corresponding thereto in the upper sheet  44   a.    
     Referring to  FIGS. 10-12 , while continuing to refer generally to  FIGS. 6-9  and  FIGS. 1-24 , the details are illustrated for the assembly of the sheets  44  with the rails  54 ,  56 . For example, the rail  54 , once properly located, and engaged with the rail  56  may be clipped off flush with the end of the sheets  44 . For example, in  FIGS. 11-12 , the end rail  56  is shown, first separated, and then engaged with the rail  54 . The assembled rails  54 ,  56  can slide along with respect to the sheets  44 . Thus, the sheet  44   a  may be moved along the rail  54  in order to provide access by the end rail  56  to the engagement with the side rail  54 . 
     For example, each of the end rails  56  may be provided with lands  60  and grooves  62  matching the corresponding corrugation grooves  61  and lands  63  of the sheets  44 . Thus, the corrugations of the sheets  44  fit within the grooves  62 . Meanwhile, the lands  60  fit within corrugations in the sheets  44 . A key  64  is a portion of the end rail  56  shaped to fit within a key way  66  in the side rails  54 . Thus, the key  64  fits in the key way  56 , fixing the end rail  56  with respect to the side rail  54 . 
     Once the entire strip  40  has been assembled with both sheets  44   a ,  44   b , the side rails  54  and the end rails  56 , the constituents may all be bonded together with a suitable brazing material and technique. However, an aperture  68  provides for receiving a tube  30 . The aperture  58  is sized to receive a tube extending thereinto. The tube  30  may be brazed into the aperture  58  just as the corrugated sheet  44  is brazed to the rail  54  or sidewall  54 , and the end rail  56  or end wall  56 . Upon completion of brazing, and cooling of the strip  40 , a vacuum may be drawn on a tube  30  in order to test the seal, and assure that the brazing has been complete and is leak tight. 
     Referring to  FIG. 13 , the assembled truss plate heat pipe  40  is illustrated with the sheets bonded together with their respective side walls  54  and end walls  56 , and with the tube  30  brazed into the aperture  58  of the end wall  56 . The assembly of the strip  40  illustrated in  FIG. 13  contains all of the components illustrated in  FIGS. 6-12  except for the handles  55  of the side rails  54 . Those handles  55  have been clipped off before brazing, or afterward, but before use or installation. 
     The truss plate heat pipe  40  is itself a truss. That is, the mesh  50  has been brazed to the sheets  44 . The sheets  44  have a certain number of their corrugations spanned by the mesh  50 . In one embodiment, the period of the corrugations in the sheets  44  is half that of the corrugations in the mesh  50 . Thus, about half the corrugations internal to the truss plate heat pipe  40  are bridged by the mesh  50 . Others may remain completely unobstructed and open. Since the mesh  50  is a mesh, the corrugations are not completely closed, but rather the liquid space  52  or the corrugation  52  is simply bridged periodically by the mesh  50 . 
     The mesh  50  also extends between the sheets  44 . Thus, in bending, the sheets  44  may be thought of as tensile or compression members at the outermost extremities of the strip  40 , while the mesh  50  spaces these sheets  44  apart from one another, thus creating a truss. Moreover, the sheets  44 , being brazed to the mesh  50  are typically connected at every periodicity of contact with the mesh  50 . 
     Thus, the center portion of each strip  40  is not at liberty to separate between the sheets  44 . Rather, the sheets are maintained together at their distance apart throughout the strip  40 . Pressure tests show that the brazed mesh  50  bonded to the adjacent or facing sheets  44  provides a substantial strength against internal pressures. Pressures of 6.5 atmospheres and more have been tested, without failure of the truss plate heat pipe  40 . The mesh  50  forms a lattice work or truss lattice between the sheets  44 . 
     Referring to  FIGS. 14-19 , while continuing to refer generally to  FIGS. 1-24 , individual truss plate heat pipes  40  may be arranged in an array  70 . An array  70  may include several, typically five, strips  40  each lying parallel to all others in the array  70 . In other embodiments, an array  70  may include sub arrays  70  of parallel batteries  74  or banks  74  of strips  40  orthogonal to other batteries  76  or banks  76  of thermal truss plate heat pipes  40 . Even with an array  70  within a single wall  20  having orthogonal batteries  74 ,  76  of strips  40 , clearances  72  between the adjacent strips  40  still provide locations for the mounting apertures  28  to pass through the wall  20 , the arrays  70 , and the entire lay up  22  as discussed above. 
     Nevertheless, it has been found that weight-sensitive applications may suffer in meeting their maximum weight limitations if the array  70  includes two orthogonal batteries  74 ,  76  of thermal truss plate heat pipes  40 . Thus, in one presently contemplated embodiment, the single battery  74  is mounted within a single thermal control panel  20 . Meanwhile, an opposite wall  20  in the same lay up  22  includes the second battery  76  as its array  70 . 
     It has been determined that the thermal conductivity of an aluminum honey comb core  18  has sufficiently distributed contact, and sufficient cross sectional area, that even a thickness of half an inch between thermal control panels  20  straddling a core  18  provides sufficient heat transfer rates to meet the functional benefits provided by a sandwich thermal control panel  10  in accordance with the invention. 
     For example, heat transferred into any edge of a truss plate  10  will be transferred into a rail  11 . For example, heat may be transferred from one joining rail  14  into the lay up  22 . Of course, the lay up  22  includes two walls  20 , each having a preferential heat transfer direction orthogonal to the other. Most of the heat will transfer most rapidly into the end of the batteries  74 ,  76  or array  70  that is in contact with the rail  11  where heat is being transferred into the lay up  22 . Of course, a certain amount of heat will also transfer into the opposite battery  76 , 74  and be transferred along the extent of the rail  11  where the heat is being added. 
     Meanwhile, heat may also be transferred directly through the skin  46  on the overall surface of a sandwich thermal control panel  10 . For example, the surface of a lay up  22  may have a device, such as powered electrical equipment connected thereto. Accordingly, the skin  46  passes heat through its thickness and directly into the sheet  44  of a truss plate heat pipe  40 . 
     However, in transferring heat between and about sandwich thermal control panels  10 , heat transferred in at, for example, a rail  11 , such as a joining rail  14 , will transfer easily into the ends of the thermal modules  40  or thermal truss plate heat pipes  40  that abut the rail  14 . They will thus be able to transfer heat along their entire length, passing heat throughout their thermal control panel  20  on that side of the entire sandwich thermal control panel  10 . Throughout the lay up  22 , meanwhile, those portions of one wall  20  that are comparatively hotter then the portions of an adjacent thermal control panel  20  on the opposite side of the core  18  will then transfer heat therebetween. Accordingly, heat travels comparatively rapidly along each of the truss plate heat pipes  40 , but still sufficiently, once distributed, through the core  18  and into the strips  40  of an opposite wall  20  within the same lay up  22 . 
     In the foregoing manner, thermal objectives may be met, in any dimension. Notwithstanding the increased distance through the core  18 , the increased resistance of the skins  46 , and so forth, the honey comb  18  presents a substantial and distributed heat transfer area. The working fluid within each of the thermal truss plate heat pipes  40  can pass quickly through the liquid spaces  52  and vapor spaces  48  thereof. Thus, distribution throughout the full area of one wall of a particular lay up  22 . One wall  20  thereof may then provide substantially increased area for heat transfer through the core  18  to the opposite wall. 
     Thus, heat may be transferred from a rail  14  across the lay up  22  to an adjacent or opposite rail  16 . That is, heat may be transferred from a top rail  12   a  to a lower rail  12   b , or vice versa. Moreover, heat may be transferred from a side rail  14 ,  16  to one of the top rail  12   a  or bottom rail  12   b  in similar manner. Moreover, heat may be transferred from a rail  11  of one sandwich thermal control panel, through the frame  24  of that truss plate  10  to the connected frame  24  of an adjacent truss plate  10 , and then transfer through the second sandwich thermal control panel  10 . 
     Referring to  FIG. 17 , each truss plate heat pipe  40  may be filled in its outer grooves  61  with a filler  78  to eliminate the air gap and improve thermal conductivity. Also a sheet  79  for bonding the sheet  44  or strip  40  to the skin  46  may be provided. A similar sheet  79  of bonding material such as a partially cured epoxy, a thermo plastic, or other polymer may bond each truss plate heat pipe  40  to the honey comb core  18 . Shrinkage of the filler  78  is typically sufficient to provide relief into which the sheet  79  may follow during pressure and cure. The core  18  has airspace. The truss plate heat pipes  40  are in intimate contact with the core  18  and skin  46 , on opposite sides thereof, as the material of the sheet  79  deforms under heat and pressure to move away from the locations of that contact. The resulting effective thermal conductivity through each wall  20  and each plate  10  is unexpectedly excellent in part due to this intimate contact. 
     Referring to  FIG. 18 , the apertures  38  are shown in various rails  11 , 12 , 16 . Likewise, the relief formed in each respective rail  12   b ,  16  is illustrated to show the fit and contact. Contact may be improved by adding bonding materials to fill any gaps, using thermal greases, epoxy, or any other suitable contact mechanism between the flanges  32  and the skins  20  of the lay up  22 . 
     In some embodiments, the rail  16  may be formed to have angles that are orthogonal or non-orthogonal between the adjacent faces thereof. For design reasons, that angle may be something other than 90 degrees or a right angle. Meanwhile, the rail  12  may serve as a mounting rail, having one portion extending parallel to the flange  32 , and supporting apertures  38  for fastening that ear  39  to some structural substrate, such as a satellite frame, aircraft frame, electronic rack, electronic housing, or the like. 
     In the illustrated embodiment, the non-orthogonal position of the ear  39  of the rail  16  with respect to the flange  32  thereof may provide for turning corners. Similarly, corners may be turned abruptly, even orthogonally if the ear  39  is exactly parallel to the flange  32  of the rail  16 . This may permit access to fasteners through the apertures  38  to fasten into a corresponding side rail  14  of an adjacent frame  24  in an adjacent sandwich thermal control panel  10 . 
     Referring to  FIG. 16 , the embodiment of  FIG. 10  is shown, wherein the ear portion  39  of the rail  16  is angled at something other than parallel to the respective flange  32 . Likewise visible is the insertion of the spacer  34 . The spacer operates as an internal flange opposite the outer flange  32  to capture the wall  20  at the skins  46  thereof. This will secure the lay up  22  into the rails  11  framing  24  the sandwich thermal control panel  10 . 
     Referring to  FIGS. 20-21 , computer modeling of the thermal response of the truss plate  10  is illustrated. In the example of  FIG. 20 , heat is being transferred across between the opposite rails  14 ,  16 . Accordingly, the isothermal lines  80  from  80   a  to  80   n  illustrate the initial high gradients near the edges, and the general thermal stability as heat is transferred between walls  20  near the central portion thereof. 
     The illustration of  FIG. 21  shows typical isothermal lines when heat is transferred from a top or bottom rail  12  to one of its adjacent side rails  14 , 16 . In this embodiment, a more general and less steep gradient exists in the central portion of the truss plate  10 . One reason for the reduced gradient is that heat must be transferred throughout all of the truss plate heat pipes embedded in the truss plate  10 . Heat distributes on one wall  20 , or in one wall  20 , in order to effectively transfer through as much available surface area as possible to arrive through the core  18 . The same process occurs in reverse at the opposite wall  20 , where the heat may then transport in an orthogonal direction to that preferred by the original wall  20 . 
     Referring to  FIGS. 22-24 , the mesh  50  may include peaks  84  and valleys  86 . The peaks  84  may be trapezoidal, triangular, or rectangular as illustrated here. It has been found that the rectangular orientation of the peaks  84  and valleys  86  seems to work better, resulting in less capillary action in the regions of vapor transport. By the rectangular configuration of the peaks  84  and valleys  86 , the dynamics of the vapor flows improve substantially, while the liquid flows are still adequate. 
       FIG. 23  illustrates the end view of the mesh of  FIG. 22  tilted with the back somewhat moved upward in order to show the shape of the mesh. Again, multiple peaks  84  of the mesh  50  can be seen. Similarly,  FIG. 24  shows a top plan view with the various angled mesh resulting from an expanded metal stamped into a corrugated format. Here, rows of peaks  84  are show with rows of the bottoms  86  or valleys  86 . 
     The present invention may be embodied in other specific forms without departing from its fundamental functions or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. All changes which come within the meaning and range of equivalency of the illustrative embodiments are to be embraced within their scope.