Patent Publication Number: US-2005120638-A1

Title: Bulkhead assembly

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a bulkhead assembly and in particular a bulkhead assembly used with an inflatable modular structure. The inflatable modular structure can be used as a spaced based platform or a habitat for use on a planet or other extraterrestrial body.  
      2. Description of the Prior Art  
      Bulkheads are used commonly in aircraft, ships, and boats as partitions to separate compartments on such craft. In this application, the bulkheads typically are walls that may or may not have doors or passageways.  
      Bulkheads have also been suggested for use with inflatable modular structures such as those structures identified by U.S. Pat. No. 6,547,189 to Raboin, et al. When used with inflatable modular structures, a bulkhead serves a number of functions besides the traditional task of partitioning areas of a vessel.  
      An inflatable modular structure is a unique approach at providing a cost effective, large volume, habitable working environment for use in space and on extraterrestrial bodies. This approach is distinct due to the characteristic structure of the module.  
      The inflatable structure has a truss arrangement predominately surrounded by an inflatable flexible multi-layered shell. This allows for minimizing the volume of the module at launch and maximizing the volume when deployed.  
      In the pre-deployed configuration, the shell is folded about the truss and secured in such a way that the module can be fitted into the payload section of a conventional launch vehicle. When the payload is launched brought to a desired location, the module is transformed into a deployed configuration.  
      In this configuration, the flexible shell is released and the module is inflated with a gas; usually air. As the volume within the module increases, the shell unfolds and expands. When fully inflated the shell encompasses a volume that is far greater than the comparable volume in a solid hulled craft of the same launch dimensions.  
      The availability of a module that has a deployed internal volume that is not confined to the volume of a hard-shelled vehicle opens the way for a new paradigm impacting numerous areas in the space sciences. For example, to date the design of equipment for use on a space module has been restricted by the size of a craft&#39;s launch payload volume. Furthermore, a great deal of equipment is usually secured in a permanent location within the space vehicle. In some cases, so secured that it cannot be removed once deployed. By virtue of an inflatable modules&#39; larger deployed volume, the module not only reduces this restrictive parameter for equipment design, it allows for movement of the equipment from one location to another within the larger volume in a variety of ways.  
      Another way the prototypical approach to creating a space module is changed is in the area of cost. Presently, most modules rely upon a solid shell. The shell is a specialty item that must be intensely scrutinized as any flaws in the structure could result in a loss of air from the module and a potentially catastrophic failure; especially if a leak occurs behind a secured piece of equipment. To address this scenario a great deal of testing and inspection must be done on the hull. Further, the hull must be composed of a material that can withstand a certain level of debris impact, insure reliability, and yet be light enough for launch. These are factors that drive up the cost of a hard-shelled module.  
      The inflatable module utilizes reliable flexible materials with proven characteristics. Coupled with this advantage, the module has multiple layers of a flexible debris shield. The use of such a shield on a rigid hulled craft would still require the volume in the craft to be reduced to accommodate the shield. While this is a serious impediment to the internal volume of the rigid craft, it is not such a serious impact to the more voluminous flexible shelled vessel.  
      Even though testing and inspection is still important for a flexible module, inspection and testing of the flexible materials is typically less expensive than for a solid shelled craft. Furthermore, since the deployed volume of the flexible craft is larger than the deployed volume of a rigid shelled craft having a comparable launch payload volume, the launch cost per cubic foot of the deployed inflatable module is expected to be far less than for the hard shelled module.  
      The aforementioned advantages of the inflatable module depend from the combination of an inflatable malleable shell and a rigid, or semi-rigid truss. The truss performs the function of a skeletal backbone to the module and is integral in defining the shape of the module and insuring that the module retains a relatively constant longitudinal dimension. This is accomplished through an interaction of a variety of structural members including the longerons and braces in a truss, airlocks, and the use of bulkhead assemblies.  
      A bulkhead in an inflatable module should serve several functions to reduce the need for other structural elements thereby reducing cost and weight. To begin, it would be the element that receives the ends of the longerons and connects to the airlocks. Furthermore, the bulkhead would provide the support for the inflatable shell. Typical elements of an inflatable shell include a inflatable bladder, flexible restraint layer, and a meteoroid/debris shield. Each of these elements requires connection points to assist in keeping the shell in place.  
      The Raboin patent identifies, but does not specifically claim, the use of a bulkhead in an inflatable structure. Rather, a pass through frame is claimed. However, there is no suggestion as to how any longerons are connected to the identified bulkhead or claimed pass through frame. Furthermore, the elements securing the restraint layer and bladder are depicted in the figures as being offset at a substantial distance from the bulkhead. This is not necessarily the optimum positioning as extending these elements away from the frame can weaken the elements as they experience forces along a moment arm. Finally, there is no mention of bulkhead load pads for distributing the forces associated with a launch.  
      What is needed is a bulkhead that receives one of the ends of a longeron, secures the flexible restraint layer and bladder in place without a large offset, and allows for the attachment of an airlock. Furthermore, the bulkhead, when situated within a launch payload and facing the booster, should have bulkhead load pads for the dispersing the load experienced during the launch of the module into space.  
     SUMMARY OF THE INVENTION  
      This invention is directed to a bulkhead assembly for use with an inflatable module. The inflatable module has at least two longerons, an inflatable bladder having an opening on opposing ends, and a flexible restraint layer having an opening on opposing ends and a plurality of attachment loops on each end. The bulkhead has a plate with an inner surface, a number of longitudinal restraint fittings, a first bladder flange, a second bladder flange, a number of flange seals, and at least two longeron sleeves.  
      Each longeron sleeve is fixedly secured to the inner surface of the plate and each sleeve is adapted to fixedly receive a longeron. One end of the inflatable bladder is secured between the first and second bladder flanges. The second bladder flange is secured to the inner surface of the plate and the flange seals are secured between the inner surface of the plate and the second bladder flange.  
      The longitudinal restraint fittings are secured to the plate and each fitting receives a loop from one end of the flexible restraint layer. Thus, the bulkhead assembly provides a structure that secures the ends of the inflatable bladder, flexible restraint layer, and longerons.  
      As dictated by the circumstances of a particular situation, the bulkhead can have an access opening and a number of bulkhead load pads. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional view of a bulkhead assembly;  
       FIG. 2  is an isometric view of the top of a longitudinal restraint fitting;  
       FIG. 3  is an isometric view of a truss with opposing distal ends;  
       FIG. 4  is a cross-sectional view of an inflatable module; and  
       FIG. 5  is a cross-sectional view of an inflatable module with longerons partial isometric view of a cover on two longerons. 
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
      The present invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings.  FIG. 1  is a cross-sectional view a bulkhead assembly  100 . Displayed are the elements of the bulkhead assembly  100 , including the plate  102 , tow of the plurality of longitudinal restraint fittings  104 , the first bladder flange  106 , the second bladder flange  108 , the flange seals  110 , and two of the longeron sleeves  112 . Also present are the access opening  114  and the bulkhead load pads  116 . The bulkhead load pads  116  are used for transferring force from the launch vehicle through the bulkhead plate  102  to the longerons  118  during launch. Thus, in the preferred embodiment, the load pads  116  are on the bulkhead assembly that is adjacent to the propulsion section of a launch vehicle. Also shown is an outer surface  117  for securing a structure to the plate  102  and an inner surface  119 .  
      The longeron sleeves  112  are secured to the inner surface  119  of the plate  102  by any number of conventional means. In the preferred embodiment, this is accomplished by using a number of bolts  120  extending through a plate  122 , which is part of the longeron sleeve  112 , and into the bulkhead plate  102 . Each sleeve receives a longeron  118 . Again, the longerons  118  are fixedly secured in place by conventional means. In the preferred embodiment, a series of bolts  124  extend through the sleeve  112  and into the longeron  118 . However securing means can also include welding, pressure fittings, adhesives, nuts and bolts, or a combination of any of the aforementioned means.  
      A bladder  124  is secured between the first bladder flange  106  and the second bladder flange  108 . The bladder serves to retain the atmosphere of a deployed space module. The bladder as openings on opposing ends  125 . In the preferred embodiment, a sealing material is placed on the bladder  124  around the edges of the opposing ends  125  to assist in creating a seal between the bladder flanges  106 ,  108  and the bladder  124 . A number of flange seals  110  are positioned between the second bladder flange  108  and the plate  102 . The bladder flanges  106 ,  018 , bladder  124  and flange seals  110  are fixedly secured to the plate  102  as a unit by know means. In the preferred embodiment, the means includes utilizing a number of screws  126  extend from the first bladder flange  106  through to the plate  102 . As indicated in the figure, the bladder flanges  106 ,  108  abut the bladder  124  along a length of the bladder  124 . In this way, the bladder is secured in place without requiring that the flanges  106 ,  108  extend far above the plate  102 . Thus, the flanges  106 ,  108  are not extensively offset and do not react to torque as significantly as would a longer element.  
      A restraint layer  127  comprised of a number of straps  128  is used to provide support for the inflated bladder  124 . The restraint layer  127  has opposing ends  129  where there are a number of loops  130 . When the bladder  124  is inflated, force is transferred from the bladder  124  to the restraint layer straps  126 . In this way, the straps not only restrain the dimensions of the inflated bladder, but also act to reduce the stress on the bladder.  
      Each strap ends in a loop  130 . Each loop  130  extends about a roller  132  that is secured by a pin  134  to a longitudinal restraint fitting  104 . The restraint fitting  104  is secured to the plate  102  by known means. In the preferred embodiment, a number of bolts  136  extend through the fitting  104  and into the plate  102 . By having a loop  130  fit around a roller  132  that is secured to the plate  102 , this is a means for securing the loop  130  to the bulkhead assembly. In the preferred embodiment, each fitting is secured to the plate, then a roller is placed within each loop, then the roller is secured in place to the fitting with the pin.  
      As indicated by the figure, the restraint layer  127  fits over the bladder  124 . In this way, the restraint layer  127  is said to substantially encompass the bladder  124 . Also, as shown in the figure, longitudinal restraint fitting  104  does not extend very far above the plate  102 . This assists in preventing torque as could be experienced by an extended moment arm from the plate. Furthermore, the fittings  104  are generally in a position adjacent to the flanges  106 ,  108 .  
      The bulkhead assembly  100  provides the base for the ends of the bladder and the restraint layer as well as a structure to secure the ends of the longerons.  FIG. 1  shows a single bulkhead assembly. It is anticipated that a module will have such an assembly at opposing ends of a structure.  
      Turning now to  FIG. 2 , the longitudinal restraint fitting  104  is substantially “U” shaped. There are opposing posts  105  that support the pin  134  that in turn supports the roller  132 . Also shown are holes  135  where botls can be inserted to secure the fitting  104  to the plate  102 .  
       FIG. 3  shows how a bulkhead assembly  100  is disposed on the ends of a truss  138  comprised of a number of longerons  118  and support beams  140 . An access opening  114  is also shown that leads into a distal end assembly  142 . This assembly  142  can take the form of an airlock or storage area.  
      Opposite to the end  142  is another distal assembly  144 . This assembly  144  can also be an airlock or storage area. Note that the end  144  is of a different shape than the distal end  142 . This is to allow for a launch structure that would interface with the bulkhead load pads  116  to facilitate transferring forces experienced during launch to the longerons  118 . An example of a launching structure  119  is shown attached to the pads.  
      Both ends  142 ,  144  are secured to the outer surface  117  of the bulkhead assembly. Both distal ends  142 ,  144  are secured to the bulkhead assembly  100  by conventional means. In the preferred embodiment, the ends  142 ,  144  are welded to the plate  102 .  
      Turning now to  FIG. 4 , a cross-section of an inflatable modular structure  146  is shown. There are opposing distal ends  142 , that can be airlocks, fixedly connected to the bulkhead assemblies  100 . The longerons  118  are secured to the longeron sleeves  112  and the sleeves  112  in turn are secured to the plate  102 . The bladder  124  is secured to the assembly  100  and is substantially covered by the restraint layer  127 . It is important to note that while the figure displays an inflated module, the restraint layer  127  also substantially encompasses the bladder  124  when the module is not inflated. At the furthest layer, a debris shield  148  covers the restraint layer  127 .  
      Addressing  FIG. 5 , two bulkheads are assembled into the module  146 . There is a first bulkhead assembly  150  at the fore end of the longerons  152  and a second bulkhead assembly  154  at the aft end of the longerons  156 . Both assemblies  150 ,  154  have access opening  114 . This is the preferred embodiment. However, it is not necessary that both assemblies have an access opening. Thus, in an alternative embodiment, the first bulkhead assembly  150  would not have an access opening.  
      The fore ends of the longerons  152  are received in the longeron sleeves  112  of the first bulkhead assembly. The aft ends of the longerons  156  are secured in the same manner to the longeron sleeves  112  of the second bulkhead assembly  154 . The fore and aft ends are secured in the same manner as described supra for attaching a longeron to a longeron sleeve as described in reference to  FIG. 1 . Returning to  FIG. 5 , the bladder is attached to the bulkheads in the same manner as described in reference to  FIG. 1 , supra. Again referring to  FIG. 5 , the restraint layer is attached to the bulkheads as in same manner as described in reference to  FIG. 1 .  
      There has thus been described a novel bulkhead assembly for use with an inflatable modular structure. It is important to note that many configurations can be constructed from the ideas presented. The foregoing disclosure and description of the invention is illustrative and explanatory thereof and thus, nothing in the specification should be imported to limit the scope of the claims. Also, the scope of the invention is not intended to be limited to those embodiments described and includes equivalents thereto. It would be recognized by one skilled in the art the following claims would encompass a number of embodiments of the invention disclosed and claimed herein.