Abstract:
The invention discloses methods of mounting heat shields onto a spacecraft. It shows a number of ways to attach heat shield tiles in a way that allows for and accommodates the thermal expansion and contraction of the tiles without overstressing them and without loosing them due to delamination of adhesives. Shown also are various fasteners, which are flexible in several directions and which should preferably be oriented to provide the least resistance to the expected deformations of the tiles.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a NON-PROVISIONAL UTILITY PATENT APPLICATION, and it is claiming the priority and benefits of the following Provisional patent application, which is incorporated herein in its entirety by reference and which will be referred to as Ref1.  
         [0002]     Ref1: Provisional Patent Application Ser. No. 60/520,091, filed Nov. 13, 2003, entitled “Heat Shield”.  
         [0003]     This application contains concepts, which are essentially an extension of the concepts contained in Ref2 through Ref5 listed below. Consequently, this application could be considered a “Continuation” or a “Continuation-In-Part” to any or to all of them. Applicant respectfully requests Examiner to advise on the proper procedure to follow in this regard:  
         [0004]     Ref2: Nonprovisional Utility patent application Ser. No. 09/947,240, filed Sep. 05, 2001, entitled “Interconnection Devices”,  
         [0005]     Ref3: Nonprovisional Utility patent application Ser. No. 10/075,060, filed Feb. 11, 2002, entitled “Interconnections”, and  
         [0006]     Ref4: Nonprovisional Utility patent application Ser. No. 10/765,772, filed Jan. 26, 2004, entitled “Oriented Connectors for Leadless and Leaded Packages”.  
         [0007]     Ref5: Nonprovisional Utility patent application Ser. No. 10/937,647, filed Sep. 08, 2004, entitled “Interconnections”.  
         [0008]     Ref2 teaches about the benefits of having “flex joints predominantly under bending stresses, as opposed to short connections predominantly under shear stresses”.  
         [0009]     In addition, Ref3 through Ref5 all teach about the benefits of “orienting the flex joints to have their low resistance to bending in the direction of radial deflections of the mounted devices”.  
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0010]     Not Applicable  
       REFERENCE TO A MICROFICHE APPENDIX  
       [0011]     Not Applicable  
       GENERAL BACKGROUND OF THE INVENTION  
     FIELD OF THE INVENTION  
       [0012]     The present invention relates generally to means and methods for attaching devices to each other, and attaching plates to other bodies, where the assemblies and/or the assemblies members get exposed to harsh operating or environmental conditions, such as when they get exposed to varying temperatures simultaneously or at varied times and varied temperature levels, and more particularly to cases where the various members of the assemblies have different thermal coefficients of expansion (TCE), what is referred to TCE Mismatch.  
         [0013]     More particularly, the present invention relates to attaching heat shielding and/or heat shield tiles and the like to the body of space vehicles or spacecrafts in general, in a way so as to prevent the premature  
       INTRODUCTION  
       [0014]     Several months ago, NASA suffered a big loss. The space shuttle Columbia had an accident, it disintegrated and the astronauts perished.  
         [0015]     To my knowledge, up to this date, a number of theories or speculations have been presented, but there has not been any conclusive determination as to the exact cause of the accident.  
         [0016]     One of the theories points to the heat shield tiles, stating that one (or more?) tile(s) or “foam” slabs had dislodged, hit the wing or other parts of the space vehicle?, created a hole in the outside skin of the vehicle, raising the temperature, etc. etc.  
         [0017]     The incident started me thinking about some ways to reduce the chances of such catastrophes from re-occurring, and I have applied some of my concepts in my latest patent applications to hopefully provide some options to the NASA people to consider using them.  
         [0018]     By the way, I will offer this invention to NASA, proposing to them to consider using the concepts here for their use, free of charge. But private entities and/or for-profit-businesses would have to license the technology from me, at some appropriate fees, if they want to use the same concepts for their endeavors.  
       PRIOR ART  
       [0019]     A patent search using the keywords “heat shield” and “space vehicle” showed over 50 patents, many of them showing prior art in the general area of the technology. However, only one patent comes somewhat close to the invention in this application, but not close enough to create any infringement, in my opinion. Obviously, I will defer to the opinion of the Examiner to decide on this point. 
        1. U.S. Pat. No. 5,489,074 to Arnold et al, entitled Thermal Protection Device, In Particular For An Aerospace Vehicle.        
 
         [0021]     The other patents in the prior art, listed below, were very helpful to me in learning more about this area of technology. I want to thank the authors/inventors of these patents and I will use some of the information in their patents to explain my invention here. 
        1. U.S. Pat. No. 3,920,339 to Fletcher et al. entitled “Strain Arrestor Plate For Fused Silica Tile”,     2. U.S. Pat. No. 4,124,732 to Leger entitled “Thermal Insulation Attaching Means”,     3. U.S. Pat. No. 4,151,800 to Dotts et al. entitled “Thermal Insulation Protection Means”,     4. U.S. Pat. No. 4,338,368 to Dotts et al. entitled “Attachment System For Silica Tiles”,     5. U.S. Pat. No. 4,439,968 to Dunn entitled “Pre-Stressed Thermal Protection Systems”.     6. U.S. Pat. No. 4,358,480 to Ecord et al. entitled “Method of Repairing Surface Damage To Porous Refractory Substrates”,     7. U.S. Pat. No. 4,706,912 to Perry entitled “Structural External Insulation For Hypersonic Missiles”,        
 
         [0029]     From these patents, I learned that, at different times, some parts of the spacecrafts can reach low temperatures as low as −270° F., and as high in excess of 2,300° F., or can reach up to 3,000° F. Some parts reach only 2,800° F., while other parts reach only 1,200° F., or even to 700° F. only. All these various temps are depending on the location of the part on the body of the spacecraft. So ideally, the heat shield protection has to be “tailored” to suit the specific location on the spacecraft. For this reason, I have provided the options of having either one single layer of shielding, or multiple layers of shielding, depending on the need.  
         [0030]     Also, the shape or contour of the spacecraft varies along its outside surface, and I have provided solutions for that too.  
       DEFINITIONS  
       [0031]     I will use the words “shuttle” or “vehicle” or “spacecraft”, to represent/designate any space vehicle of this kind, where high amount of heat is generated during reentry from space into the earth atmosphere, or the like, i.e. any body in general that needs to have a heat shield, and where some layer(s) of heat insulation material(s) are required to be mounted on the outside of the vehicle body or the like, to act as a heat shield and to protect the insides of the vehicle from such a high level of heat and/or temp.  
         [0032]     Tile will stand for any individual section or segment of the heat shield material, used mainly to prevent large amount of heat to transfer from the outside of the space vehicle, inwards towards the vehicle body and its contents. The definition includes also any “foam” or “foam slab” or the like.  
         [0033]     Joint will stand for any combination, where a tile is attached on to the vehicle body, the joint being considered the combination of the tile, the section or area of the vehicle body corresponding to the area of the tile and to the means of holding the tile to that area of the vehicle body, such as glue or adhesive etc. My understanding is that the tiles are simply “glued” on to the vehicle body.  
         [0034]     Adhesive, and/or glue will stand for any method used presently to attach the heat shield tiles to the body of the space vehicle.  
         [0035]     TCE will stand for “Temperature Coefficient of Expansion” 
         [0036]     TR will stand for “Tie-Rod” 
         [0037]     Each TR has two ends and I will designate them as follows. The lower end of any TR, i.e. the end near the vehicle body, will be called the “Vehicle End” or “VE”. The other end of any TR, i.e. the end near the tile, will be called the “Tile End” or “TE”. See also “Definitions”.  
         [0038]     VE will stand for “Vehicle End” of a Tie-Rod, i.e. the end of the tie rod that is closest to the body of the vehicle.  
         [0039]     TE will stand for “Tile End” of a Tie-Rod, i.e. the end of the tie rod that is closest to the heat shield tile.  
         [0040]     wrt will stand for “with respect to” 
         [0041]     L is the original length of a body under consideration,  
         [0042]     Δt is the temperature change (increase or decrease) of the body,  
         [0043]     k is the TCE of the material of the body,  
         [0044]     ΔL is the change (increase or decrease) in the length L of the body, due to the given temp change.  
         [0045]     Temp will stand for temperature.  
         [0046]     Anchor TR is the TR that would be considered to be holding the tile in place wrt to the rest of the members in the arrangement. Usually, it would be preferred to place the anchor TR close to the geometric center of the tile, which could also be considered the thermal center of the tile. However, in certain situation, it would be better to place the anchor TR at a strategic corner or edge of the tile.  
       THE PROBLEM  
       [0047]     I think that one of the problems with most conventional methods of attaching/joining such tiles to the body of the shuttle is the effect of the temperature difference between one component of the “joint” and the other components. An example of such a joint, is when a tile is glued to the body or to a support member using some kind of an adhesive. Add to this problem, the effect of any mismatch in the Temperature Coefficient of Expansion (TCE) that could exist between the components of such a joint. The fact that some adhesives that are used loose their elasticity at a specific low temperature does not help the problem either.  
         [0048]     Let me explain.  
         [0049]     Please see  FIG. 1 .  
         [0050]     Let us consider a tile, which is “glued” to the shuttle/vehicle body, as shown in  FIG. 1 .  
         [0051]     Let&#39;s say that at Room Temperature (RT) or rather at Ambient Temperature (AT), the tile length is T1 and the length of the vehicle body portion or section that corresponds to this tile length is B1. The tile is attached to the body by some means, such as an adhesive or glue or the like. The body is also at RT or AT.  
         [0052]     At RT/AT, both parts have the same length, i.e. T1=B1.  
         [0053]     The tile has the proper shape to match the shape of the body at this location, whether straight or curved, and the “adhesive” is holding the tile to the body.  
         [0054]     Now, let&#39;s look at what happens when the vehicle is going through re-entry. The temperature of the tile rises to a very high level. But the tile is supposed to protect the body underneath it by preventing the heat from penetrating through. Hence, the body temperature underneath the tile is much lower.  
         [0055]     Let&#39;s assume that the temperature difference between the tile and the body of the vehicle is 1,000° C., although it is understood that the temp difference can be much higher.  
         [0056]     My understanding is that the tiles are made of a ceramic material, which has an average TCE of approximately 6 ppm/° C. This means that if the tile&#39;s temperature rises by 1° C., then the length of that tile would increase by 6 units of length for every 1 million unit of length of its original length.  
         [0057]     In other words, if the tile&#39;s original length is 1 foot, and its temp rises by 1 degree C, then the tile&#39;s length would increase by [(1/1,000,000)×6] of one foot, or by [(1/1,000,000)×6×12] of one inch. This equals 0.072 of one thousandth of an inch for this 1° C. temp rise.  
         [0058]     Now if the tile&#39;s temp rises by 1,000° C., then the tile length would increase by [0.072×1,000] of an inch, or approx. 0.072 inch.  
         [0059]     If the tile were twice as long, i.e. 2 feet long, then the increase in its length would be twice as much, i.e. approx. 0.144 inch.  
         [0060]     If the temp rise were twice as high, i.e. 2,000° C., then the increase in length would again be twice as much, i.e. 0.288 of an inch, i.e. over one quarter of an inch.  
         [0061]     The physical relation is represented by the following equation: 
 
Δ L=L×Δt×k  
 
 Where: 
        L is the original length of the body,     Δt is the temperature change (increase or decrease) of the body,     k is the TCE of the material of the body,     ΔL is the change (increase or decrease) in that length L of the body, due to the given temp change or thermal dimensional change or deformation.        
 
         [0066]     Note that if the tiles were made of some other material, then the k value would be different, and could possibly be larger yet than that of ceramic. Hence, the thermal dimensional change or deformation ΔL would be larger than the ones shown above.  
         [0067]     The purpose of all this analysis is to show that the expansion of the tiles is fairly large for those high temp rises.  
         [0068]     If the tile is attached to a substrate that remains at room temperature, because the tile is doing a good job insulating the substrate, then the difference in length between the tile and the substrate will be equal to the numbers shown above. But if, say, the substrate&#39;s temperature rises is about one half of the temp difference between the tile and the substrate, and if the TCE of the substrate is identical to the TCE of the tile, then the length difference would be one half of the numbers shown above.  
         [0069]     However, if the TCE of the substrate is different than that of the tile, then we need to repeat the above calculations to find the changes in the substrate itself, and then determine the different in the lengths of the tile and the substrate.  
         [0070]     Now, if we consider that the “adhesion” is the only means that is holding the tiles to the substrate, which is the body of the shuttle, then we can expect that, under these harsh temp conditions, the adhesive could break down, especially at the edges of the tiles, where the expansion is largest. Eventually, the tile could separate from the adhesive and/or the body of the shuttle. The result is that the tile would delaminate, especially at the edges of the tile. The delamination could propagate towards the center of the tile, and the end result could be that the tile could become loose and could fall off, if the rest of the adhesive is not strong enough to hold the tile down in place. This is more apt to occur, especially after some time or some repeated heating and cooling, such as after several “re-entries”.  
         [0071]     Of course if the adhesive degrade when its temp gets below its glass transition, then the problem become much worse yet.  
       RECOMMENDATIONS/PROPOSED SOLUTIONS  
       [0072]     I would like to address two issues and propose them in the following solutions: 
        1. The method of attaching the heat shield tiles to the body of the vehicles. Solution: Use a flex joint between the tile and the body.     2. Arrangement of the heat shield around the vehicle body. Solution: Use multi-levels of tiles.        
 
       BRIEF DESCRIPTION OF THE INVENTION  
       [0075]     The main objective and the basic concept of the present invention is to provide an easy way for absorbing the differences between the dimensions of the tiles and the dimensions of the spacecraft&#39;s body, while still keeping hold of the tile, during the various temperature changes that they undergo during the operation of the spacecraft. The purpose is that the tile would have room to deform and yet not get loose and/or fall off.  
         [0076]     This can be accomplished by attaching the tile to the body using means, which I will refer to as Tie Rods (TRs) or Flex Joints, in such a way that these means would accommodate the expected deformations of the tile wrt to the body, while still maintaining the tiles attached to the body.  
         [0077]     One way to accomplish this objective is to make the TRs such that they can “flex” in the expected direction(s) of the deformation, yet they should still have the proper strength to hold on to the tile. The tie rod can be shaped so that it can flex in one or more of the directions of the expected deformation(s).  
         [0078]     Case 1: For example, if the tile is expected to grow in its length only, i.e. to deform in one direction only, then the TR holding the tile to the body could be made to flex and to allow the tile to deform or move in that direction. We would refer to such a TR as a one-direction flex joint. Such a TR can be like a simple cantilever beam, as shown by numerals  31  and  41  in  FIG. 2 , but with a more slender stem. The TR would act as a cantilever and its beam would deflect, i.e. “bend” and its tip would move in a direction normal to its long beam axis, in the direction of the applied deformation. We could also refer to such a deformation direction as a “Radial” deformation, and the TR as a Radial Deformation TR or simply a Radial TR.  
         [0079]     Actually, this kind of tie rod can also flex in a second direction, which would be perpendicular to the Radial direction but still within a plane parallel to the tile and to the body. This would be referred to the Tangential direction. These two directions could be considered two orthogonal directions substantially within the plane of the tile. Such a tie rod can not flex in the third orthogonal direction, which is the Normal direction, which is perpendicular to the first two, because such a TR is not supposed to change its length. All it can do is to bend sideways, in a direction perpendicular to its long axis.  
         [0080]     We could also use a guide, like a picture frame, to contain the edges of the tile, in which case the tile edges would be able to slide within the guides, i.e. the spaces under the edges of the picture frame, to accommodate the deformations of the tile. Again, here the frame would allow the deformation in the Radial as well as the Tangential directions, but not in the Normal direction.  
         [0081]     Case 2: This is when we expect that the tile would deform in the Normal direction as well. This would happen mostly when the shape of the tile and/or the body of the spacecraft have some curvature and the tile is shaped to approximately match the shape of the body. In this case, the tile may “bulge” outwardly or inwardly wrt the body, i.e. away from the body or closer to it. In such a case, we would use a TR that can accommodate such a deformation, of course while still holding the tile strongly enough so that we would not loose the tile. Such a TR could have an “L” shape for example, so that the vertical leg of the “L” would flex in the first two directions as explained above, while the horizontal leg of the “L” would flex in the Normal direction. A still better shape would be the “double L”, as shown by numeral  161  in  FIG. 6  and numeral  177  in  FIG. 7A , and numeral  181  in  FIG. 7B , and the TR in  FIG. 9A . Such a TR would perform as well as the single “L” TR, except that it could have both ends in substantially the same direction. This would be preferred in the case where the tile is substantially parallel to the body and the TR is substantially perpendicular to both.  
         [0082]     The TRs shown in  FIGS. 3, 4  and  9 B would provide an even larger range of flexibility, in all three directions, because the effective length of the “flexing beam” is longer for the same total height of the TR.  
         [0083]     In certain cases, all the TRs can be of the flex type and the tile would be “floating” on all the flex joints, balanced by their combined applied forces. In most cases, however, it would be more advisable to “fix” at least one point of the tile. Consequently, we would use one TR to act as the “anchor”. This TR would not move and would hold the tile “fixed” at that point. In such a case, all the other TRs should be of the flex type, to allow for the expected deformations wrt the anchor. Numerals  31  and  41  in  FIG. 2  are supposed to be “fixed” TRs or “anchors”. They are shown to have a wider base, to indicate that they are sturdy and stable and that they would not flex.  
         [0084]     A second concept of the present invention is the “orientation” of the flex joints. From Ref3 through Ref5, we have learned the value of “orienting” the interconnections between members exposed to harsh environments and to thermal cycling. Basically, it is desirable that the TRs or flex joints would present the least resistance against the deformation. This would induce the least amount of stresses in the tile and the body, and would preserve the long operating life of the elements involved. The tiles seem to be the most fragile elements in our case here, and we want to induce the least amount of stresses in them. The TRs need to be strong enough to hold down the tiles attached to the body, but yet need to be flexible enough in the direction of the deformation(s). One way to achieve this objective is to make the cross section of the TR wide and thin, i.e. with a generally elongated cross-section. In such a case, the flat face of the cross-section should be facing the direction of the deformation, i.e. should be “oriented” to face the “anchor”, if there is one, or to face the “thermal center” of the tile, if no anchor is being used. Examples of such TRs are shown in  FIGS. 4, 7B ,  9 A and  9 B. Each of these TRs would be oriented, to have its wide face facing the anchor or the thermal center of the tile in question. No figures of Oriented tiles are provided in this specification, but examples of such oriented interconnections can be seen in Ref3 through Ref5.  
         [0085]     A third concept of the present invention is to provide the shielding in more than one layer, creating an additional resistance to heat transfer. In a way, this would be similar to house windows with double or triple glazing. The multi-layers shielding would be used at the locations, where the outside temp, or the temp differential between the Outside and the inside, would be very high; and the single layer would be used at the locations with lower outside temp or temp differential.  
       DETAILED DESCRIPTION OF THE INVENTION 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0086]      FIG. 1  shows the changes in dimensions of different bodies when their temperature changes. These dimensional changes can be more or less, depending on the Thermal Coefficient of Expansion of the materials of the bodies.  
         [0087]      FIG. 2  shows the nose of a space vehicle, with some heat shield tiles attached to it using Tie Rods, according to this invention.  
         [0088]      FIG. 3  shows one Tie Rod according to this invention. It is shaped to have a loop between its two ends. The purpose of the loop is to provide a large flexibility, i.e. capability to deflect, while still maintaining a good retention force to hold the tile to the body of the space vehicle. If we wanted the same flexibility out of a straight Tie Rod, its height would have been much larger. In other words, the total height of the Tie Rod is shorter than if it were straight, i.e. without the loop, and if we would wanted to have the same deflection under the same forces. The cross-section of this rod is generally round.  
         [0089]      FIG. 4  shows another Tie Rod, with a loop, like the one in  FIG. 3 , but the cross section of this tie rod, between its two ends, is rectangular or elongated in general. The advantage of such a cross-section is to obtain even more flexibility with the same retention force. The added flexibility is in the direction perpendicular to the flat face of the rod.  
         [0090]      FIG. 5  shows another nose of a space vehicle, like the one in  FIG. 2 , but with some differences and more details. It shows on the right hand side one arrangement and on the left hand side another arrangement, just to show the different methods and options of attaching the tile to the body.  
         [0091]      FIG. 6  shows more details and options of the attachment methods and it also shows one optional way of shaping the gap between adjacent tiles.  
         [0092]      FIG. 7  shows two different “double L” or “gooseneck” tie rods. In  FIG. 7A  the cross-section is uniform, e.g. round, while in  FIG. 7B  the cross-section is flattened.  
         [0093]      FIG. 8  shows another nose cone, but with two layers of heat shield tiles.  
         [0094]      FIG. 9  shows two tie rods, each of them having two fasteners at each end. Obviously, one tie rod is a “gooseneck” and the other is a “loop” type. The advantage-of having two fasteners at each end, beside the increase in reliability, is to be able to properly “orient” the tie rod in the desirable orientation. In addition,  
         [0095]      FIG. 10  shows a “zoom-out” view of a nose cone, showing some details of a three-layer heat shield.  
         [0096]      FIG. 11  shows a “zoom-in” view of the nose cone of  FIG. 10   
         [0097]      FIG. 12  shows a more enlarged view of the same, showing additional details of the components.  
         [0098]      FIG. 13  shows another nose cone, with another arrangement of heat shielding. It can be seen here that the front tip has three layers of shielding, and behind that is a section with only two layers and behind that a third section with only one layer of shielding. Notice also how the body of the spacecraft is shaped in a staggered way to accommodate the various layers, while still maintaining a smooth streamlined outermost surface contour.  
         [0099]      FIG. 14  shows a similar nose cone as in  FIG. 13 , but it continues the layers and sections to show that there is another last layer, where the tiles are attached directly to the body, say using an adhesive instead of the flex joints.  
         [0100]      FIG. 15  shows a number of optional features of the tie rods, such as incorporating a “coupling” or having threads of opposite directions at the two ends of the tie rod.  
         [0101]      FIG. 16  shows an optional method of shaping the edges of adjacent tiles, and of filling the gap between them.  
         [0102]      FIG. 17  shows a “summary” or “overview” of some of he features of this invention  
         [0103]      FIG. 18  shows a “picture frame” embodiment, where the tile is retained to the body of the spacecraft by the frame guides. An optional “anchor” could also be used.  
     
    
     PREFERRED EMBODIMENTS  
       [0104]      FIG. 2  shows one embodiment of the inventions and the general scheme of the proposed solutions.  
         [0105]     It shows a part of the vehicle body  11 , e.g. the nose, but it could be any other part of the vehicle, e.g. the wing etc. It shows also a number of individual tiles  21 ,  23 ,  25 ,  27 ,  29 , etc. in a row  13 , surrounding the vehicle body. The tiles are attached to the vehicle body  11  by various “tie-rods” (TRs)  31  through  55 . We can see that there are at least two kinds of TRs.  
         [0106]     The TR  31 ,  41  and  51 , at the center of each tile, could be straight and could be stubby and thick. These would be considered the “anchor” members or “Anchor TRs”. Most of the anchor TRs would be located at the geometric center of each individual tile, like with tiles  21 ,  23  and  25 . In certain cases, the anchor members could be located at one end or corner of the tile, as will be seen later. The anchor TR can be stiff and rigid and could be wider at their bases.  
         [0107]     The other TRs are mostly curvilinear. The purpose of their special shapes is to provide some flexibility between the tiles and the vehicle body. When the tiles get hot and expand, and their dimensions change compared to their original RT/AT dimensions and compared to the dimensions of the vehicle body, then the flexible TRs allow the tiles to move, but without separating from the body. I will call these TRs the “Flex Tie-Rods” or the “Flex TRs”.  
         [0108]     Depending on the shape and especially on the curvature of the individual tile, the thermal expansion or contraction could be either in one direction or in two directions. The one direction usually would be in a direction “parallel” to the body of the tile. The two-directional movement can be analyzed in two components, one component being “parallel” to the body of the tile, while the second component would be “normal” or “perpendicular” to the general direction of the body of the tile. For simplicity, we will call these two directions, at any specific point along the body of the tile, as being the normal and the parallel directions to the body of the tile at that point.  
         [0109]     I will digress here and talk about the thermal deformation of bodies when they undergo temp changes.  
         [0110]     Actually, all bodies, including the vehicle body, expand and contract “radially”, when they are heated or cooled, as if they were part of sphere. Their thermal dimensional changes radiate from the center of that sphere.  
         [0111]     If the body is shaped like a long slender rod, then we observe that its thermal deformation is as if it is only in one direction, i.e. its longitudinal direction.  
         [0112]     If the body is shaped like a flat slab, like a disc or a square, then we say that its thermal deformation is in 2-directions, say its x- and y-directions.  
         [0113]     If the body is a solid sphere, then its thermal deformation is considered to be radially, which in reality is in 3 dimensions.  
         [0114]     If the body is a hollow shell, then it will behave as if it is solid and part of a solid sphere.  
         [0115]     If we look at a specific point of this body and try to determine the direction of its thermal deformation, we will see that it follows the direction of the deformation of a sphere. We can then say that the deformation is radially, emanating from an imaginary center of an imaginary sphere that encompasses the shape of that shell.  
         [0116]     For this reason, if we look at the cross-section of tile  21  in  FIG. 2 , we would find that the anchor TR  31  is holding it fixed at the TE  32 . Then the ends  21 A and  21 B of the tile  21  will look as if they will move in the directions  21 Ax and  21 Ay at the end  21 A and in the directions  21 Bx and  21 By at the end  21 B.  
         [0117]     For this reason, the TR  35  should be able to flex in both directions  21 Ax and  21 Ay, while the TR  39  should be able to flex in both directions  21 Bx and  21 By.  
         [0118]     On the other hand, in the case of tile  25 , things are different. The cross-section of tile  25  looks more as if it is almost a straight line. Most of its thermal deformation would be along its longitudinal direction. In this case, the TE of the Flex TRs  53  or  55  would move mostly in that direction.  
         [0119]     Now back to our specification here.  
         [0120]     Because of the above, most of the other TRs, i.e. the Flex TRs, not the anchor TRs, are curvilinear. They are shaped to accommodate the thermal movements of the tiles, both the direction and the magnitude of those movements. If the thermal movement is expected to be only in the parallel direction to the general shape of the tile, then the Flex TR could still be a straight rod, and it would flex as a simple cantilever. However, if the thermal movement is expected to be a two component movement, i.e. both in a parallel and in a normal direction to the general shape of the tile, then the Flex TR should have some curvature to it, to allow for these two components. Such a shape could be like a “gooseneck” or as a “loop”, as described further down below.  
         [0121]     To recap:  
         [0122]     The Anchor TRs give their respective tiles their “location” wrt the vehicle body, while the Flex TRs allow the extremities of the tiles to move depending on their temp changes and their thermal expansion and contraction according to those temp changes. The Anchor TRs could be placed close to the geometric center of each tile, although in certain cases, they can be placed elsewhere, as will be seen later down below.  
         [0123]     Notice the direction of the ends of the TRs in this  FIG. 2 . The Vehicle Ends of the TRs are angled/pointed/directed “normal” to the vehicle body at their respective spots. The Tile Ends of the TRs have different orientations. The Tile Ends are oriented in a way to facilitate the insertion of the TRs in the individual tiles, or conversely, to facilitate the mounting of the individual tiles on top of the TRs. All the TE of the TRs that go into a specific tile, are oriented to be parallel to each other and preferably normal to the general shape of that specific individual tile. This would allow the tile to be mounted on these TRs, without the need to twist or bend any of the TRs.  
         [0124]     For example, the TEs of TRs  31 ,  33 ,  35 ,  37  and  39  are all vertical and parallel to each other. This will make it possible to mount tile  21  on these TRs. On the other hand, the TEs of TRs  41 ,  43  and  45  are still parallel to each other, but they all are a different angle than that of the TRs for tile  21 . The angle here is such that it is roughly perpendicular to the general shape of this specific tile  23 . Again, the purpose of this specific angle is to makes it convenient to mount tile  23  on these TRs.  
         [0125]      FIGS. 3 &amp; 4  show simplified shapes of the Flex TRs. The 2 ends in these 2 figures would have threads to accept washers and nuts, to hold on to the vehicle body and to the tiles. The mid-sections would have a gooseneck or a loop, as shown, so as to easily allow some relative movement or deflection between the one end of the TR and the other.  
         [0126]     The dimensions of the cross-section and the size/diameter of the loop would be designed to allow enough relative movement or deflection, but still be strong enough to hold the tiles in place, i.e. attached to the body of the spacecraft, considering all the external forces acting on the tiles throughout their entire operating life.  
         [0127]      FIG. 5  shows some other details.  
         [0128]     PS: Notice that here in  FIG. 5 , as well as in the other figures, I am showing a number of various alternatives, just to show the various possible options. It does not mean that all of them should be used on one vehicle. The end designer can choose/select the shape(s) that best fits/suits his particular situation and ignore the other variations.  
         [0129]     The tile  121  is similar to tile  21  in  FIG. 2 , but with some differences. First it shows the TRs with different shapes. Instead of having a full “loop”, they have a jog, sometimes called “gooseneck” or an “L” shape or a “double L” shape. The Anchor TR  131  is still straight and rigid like Anchor TR  31  in  FIG. 2 .  
         [0130]     PS: Here I am not showing any anchor, but we should preferably have some other means of “fixating” the tile in position. Not shown in this figure.  
         [0131]     There is a difference between the Right Hand Side (RHS) and the Left Hand Side (LHS) of the figure. The 2 TRs  137  and  139  on the RHS have their VEs sloping at different angles, basically normal to the vehicle body at their respective locations. The TEs of these 2 TRs are oriented vertically, parallel to the Anchor TR, to facilitate the mounting of the tile. In contrast, the 2 other TRs  133  and  135  at the LHS of the figure have their VEs in a vertical direction, parallel to the direction of the TEs of these TRs, again to facilitate the mounting of the tile.  
         [0132]     In addition, I am showing in this  FIG. 5 , more details of the threads and nuts etc. I am also showing the machining or the “facing” of the vehicle body and the tile, so as to accommodate the nuts, washers, etc.  
         [0133]     Furthermore, TR  133  shows a “boss  141  at the TE, as well as TR  15  has a boss  143  at its TE.  
         [0134]     PS: The figure shows a number of different alternatives for the TRs. It is simply to show the various possible options available. It does not mean that we should use all of them. We can select the shape and/or variations that suit the individual situation under consideration.  
         [0135]      FIG. 6  shows even more close-up details of how a TR could be mounted and attached to the vehicle body and to the tile. It shows the boss, the countersinking in the top surface of the tile. It also shows the joint  151  that can be used between any 2 tiles, to reduce the chances of having hot gases leak inwards.  
         [0136]     In addition, the figure shows that the space at the joint  151  between the tiles could be “filled” with some compressible material or compound material or the like, to further reduce any chance for the gases to leak inwards, and to smoothen and even out the surface at the outside of the tiles.  
         [0137]     Similarly, the countersinking space  153  at the VE of the TR can be filled in a similar way and for similar purposes.  
         [0138]      FIG. 7A  shows a TR  177  like TR  135  in  FIG. 5  and TR  161  in  FIG. 6 , highlighting the details of the thread  171  and the washers, with the nut  173  at the bottom and the boss  175  at the top.  
         [0139]      FIG. 7B  shows another TR  181 . This one has a wider cross-section along the gooseneck  183 , to give it more strength if required, and yet still remaining flexible enough to accommodate the effect of the thermal expansion and contraction of the tiles.  
         [0140]      FIG. 8  shows a 2-layer shield  201 . The vehicle body  11  is surrounded by a number of tiles located along one layer  211 , and then by a second group of tiles located along a second layer  221 .  
       BENEFITS  
       [0141]     There are a number of benefits of using such a multi-layer arrangement.  
         [0142]     First, reduced temp differential or gradient between the layers and also between the layer and the vehicle body. Consequently, less dimensional differences between the tiles and the layers.  
         [0143]     Secondly, it also provides an additional layer of insulation between the vehicle body and the outermost layer of tiles.  
         [0144]     Thirdly, the double seals, or even the triple seals as seen later in  FIGS. 10 through 14  and  FIG. 17 , in each subsequent layer, improve the sealing of any gases, thus better protecting against hot gases leaking to the inside of the vehicle.  
         [0145]     A fourth benefit depends on whether the space between the layers is filled or not. If the space is filled, say with a foam of some sort, it can act as a yet another layer of insulation and of sealing. But there could be some better heat “conduction” between the individual shield layers. On the other hand, if the space is left empty or filled with air or simply vacuum, then the heat transfer mechanism would be only through radiation, in which case, we would expect a smaller amount of heat to be transferred from one shield layer to the next, or to the vehicle body itself But again, if the space is filled, then the filling could possibly provide additional mechanical support and integrity to the tiles, thus possibly providing a badly needed feature.  
         [0146]     Of course, the disadvantage of such an arrangement is the extra weight and cost. This has to be evaluated on its own merit.  
       NOTES ABOUT THE ABOVE FIGS  
       [0147]     1. The various figures show a lot of different alternative designs. It simply illustrates the various options available to be used. Hopefully, one or more of these options could be used in future space missions, keeping the tiles attached to the vehicle, so as not to have more accidents.  
         [0148]     2. The spaces between the various layers of shielding tiles can either be left empty, or can be filled with an appropriate medium.  
         [0149]     3. If left empty, then the heat transfer mechanism would be “RADIATION”, which is usually the mechanism that transfers the least amount of heat. The inside surfaces could also be painted with low emissivity coatings, such as probably white or bright glazing, e.g. mirror finish or the like.  
         [0150]     4. If the spaces are filled, then there will be some heat transfer through “CONDUCTION”. There will be more heat transfer than with “Radiation”, but the transfer in this case will depend on the coefficient of conductivity of the filler material. However, an advantage of filling is to improve the “sealing”, so as to better prevent any hot gases from penetrating through to the inside compartments, and to provide a better mechanical integrity to the tiles.  
         [0151]     5. The tiles could be made such that they would have some “reinforcement” in them. For example, if they are made of a composite material, then they could have layer(s) of metal mesh inside or at one or both surfaces, to give them more strength and integrity. This would help retain the tiles in place by the tie rods and their washers and nuts, etc. In other words, the tiles could look like a multi-layer composite (like plywood), where one layer would be the insulating material, the second layer the wire mesh or reinforcement and the third layer another insulating material layer, etc.  
         [0152]      FIG. 9  shows two TRs with wide cross-section.  FIG. 9 -A shows a “gooseneck” or a “double L”, while  FIG. 9 -B shows a “loop”. In both cases, the TRs have two (2) threaded rods at each end. This would enhance the reliability of the assembly, due to “REDUNDANCY”. In case on threaded rod breaks, then there is still another one to hold the tile in place. Also, having such a “pair” of attachment means at the end of the Tie Rod, would ensure that it will keep its “orientation”, as explained below.  
         [0153]     The second point that the figures highlight is the fact that the wide faces of these tie-rods are oriented in such a way, that their wide faces are directed towards the “ANCHOR” point of the respective tile. If the Anchor is located at the geometric/thermal center of the tile, then the wide faces of these Tie Rods would face toward that center/anchor. If on the other hand, the anchor is located elsewhere, e.g. at a “fixed” corner of the tile, then these wide-faced tie rods would be oriented such that their wide faces would be oriented to that corner/fixed anchor.  
         [0154]     The reason is to reduce the resistance of the TR against bending, thus making the TR as flexible as possible, in the expected direction of bending, i.e. along the lines of thermal expansion and/or contraction.  
         [0155]      FIG. 10  is a general overview of a cross-section in a space vehicle body. It shows some heat shields etc. The next figures will “zoom-in” closer and show more details.  
         [0156]      FIG. 11  shows a close-up of the nose of the vehicle, with some details of TRs, etc.  
         [0157]      FIG. 12  shows the same things, but in a more close-up view. It shows the three (3) shields or shielding layers and the three (3) spaces between them and the vehicle body. It shows also the Tie-Rods. Note that all the TRs here are “LOOP” TRs. It is not necessary to have them of this “loop” kind. Some could be a simpler “gooseneck”. Also you will need “Anchors” TRs, which are not shown here.  
         [0158]     Also notice again that in this figure, the threaded ends of every tie rod attaching a specific tile are positioned in a similar direction, i.e. they are parallel to each other. To repeat, the purpose is to facilitate the mounting and dismounting of the individual tiles on top of the tie rods. If the tie rods are mounted perpendicular to the surface or contour of the space vehicle, which may have a certain curvature at that location, then the ends of the tie rods would be pointing in different directions and this would make it difficult to “slide” a tile over those ends. But if all the ends of all the TRs engaging a specific tile point in the same direction, then it would be easy to slide that tile over them, or inversely, it would be easy for the tie rod ends to slide into the hole of that individual tile.  
         [0159]      FIG. 13  shows the LSH half of a nose of a space vehicle. It shows that all the way at the tip, there are three (3) layers of shielding, while we have only two (2) layers of shielding at an area behind the nose, and then further behind that, we have an area with only one (1) layer of shielding.  
         [0160]     We notice also that the body of the vehicle is shaped in a “stepped” fashion inwardly, to accommodate these different layers, so as ultimately we would have a rather smooth continuous “aerodynamic” surface at the outermost layer of shielding, i.e. on the outside surface of the vehicle. This would minimize the resistance to motion through air, etc.  
         [0161]     We notice also that many of the tiles have one anchor at one end and flex TRs at the other tie-down locations. We notice also that the tiles along the long side, which have rather simple elongated shapes, have TR that have “gooseneck” shape. On the other hand, the tiles that are at the tip of the nose, where the tiles are more curved, we provided them with TRs that have a “full loop” shape.  
         [0162]      FIG. 14  shows an arrangement very similar to the one shown in  FIG. 13 , except for one big difference. Here I am showing a fourth (4 th ) area, further back along the body, away from the nose, where the tiles could be mounted directly to the body, without Tie-Rods. I am assuming that about that area along the length of the vehicle body, the temperatures are so much lower, that we could get away with such an arrangement, without the fear of delaminating any tiles or loosing them. The NASA people would know better, if this (dumb) assumption is correct or not.  
         [0163]      FIG. 15  shows a few arrangements, where the Tie-Rods have special features.  
         [0164]     First,  FIG. 15 -A and  15 -B show a TR with a “coupling”, so that one part of the TR can be mounted to the body separately, and the other part can be mounted to the tile separately. Then when the tile is ready to be attached to the body, the “coupling” would be used to complete the process.  
         [0165]     Second,  FIG. 15 -C shows the TR ends have threads of opposite directions. This would allow placing the tile in position first, and then placing the Tie-Rod between the body and the tile and by rotating the Tie Rod, we can tie down or assemble the tile to the body. A lock nut or some other means can then be used to prevent the TR from moving out of position and from unscrewing.  
         [0166]      FIG. 16  shows a joint between any two tiles, where a seal filling is located. The figure shows that the joint surfaces can have some serration, or any similar appropriate indentations, in order to better hold the filling in place, and consequently to have a better seal.  
         [0167]     Note that all the nuts that are to be used in this process should preferably be of the kind that would not shake loose during the life/operation of the vehicle. They could have something like an elastomeric lock ring or the like.  
         [0168]     Note also the washers should preferably be of the “LOCK-WASHER” type.  
         [0169]      FIG. 17  shows a recap and comparison of several old views, i.e. from previous figures, but it also shows a new version of the multilayer shielding at the nose of the spacecraft.  
         [0170]      FIG. 18  shows a “picture frame” that can provide room for thermal deformation in the same plane of the tile, i.e. in the x- and the y-directions. An anchor could be provided say approximately near the center of the tile.