Patent Application
20050284085
1. Field of the Invention
This invention relates to a multi-purpose laminate beam for use in a space environment to support a human habitat module or other space structure. The multi-purpose laminate beam functions to provide structural support for the module and storage of pressurized gases such as oxygen and nitrogen.
2. Description of the Prior Art
Structural supports are well known in the building trade and have been used in a number of earth bound applications. This has carried over to the use of structural beams in the construction of space related crafts. In a space environment, the beam can take a number of forms. One such form is that of a longeron.
A longeron is a framing member that runs fore and aft on a structure such as a space based human habitat module. In application, there are usually a number of longerons that are at the structural core of modular space habitats.
Another application of the beam is as a cross member attached to longerons, or as structural support to other elements of the habitat. The use of beams in such situations deals with the forces on a structure.
In space applications such as a modular human habitat, the module experiences significant stresses from a number of sources. For example, load stresses from the module being launched into space. Also, internal forces due to the pressurization in the case of an inflatable modular habitat. Further, externally applied loads such as those experienced during docking maneuvers or linear attachment of other modules.
The aforementioned loads identify the need for a rigid structure. A framework of rigid beams can accomplish this task. In the case of a modular habitat, a structural member is part of the framework that provides a substantially rigid foundation. This can be, for example, part of the metallic structural core, or a translation tube, in the case of an inflatable module.
While the use of beams is critical to the construction of a module in space, there is an overriding consideration that severely restricts widespread application of beams in that environment; the weight associated with structural beams.
The cost to place a structure in space is extremely high. This cost rises in relation to the increase in the mass of the structure launched. Since metallic beams provide structural support, they tend to be heavy and this weight increases the cost associated with a launch of the beams, and the overall space module, into space.
An alternative to using of metal beams is to utilize composite materials. The terms related to composite and laminate materials used herein are given their ordinary and customary definitions as known in the field.
It is important at this point to define a few terms used in the field of composites. A lamina is a single ply or layer, which can be comprised of, for example, carbon fibers and epoxy. A composite is a combination of at least two materials that, on a macroscale, have differing properties. The composite is essentially nonhomogenous such that the constituents do not merge completely into each other and the constituents can be physically identified. Since the lamina has two elements in this case, that are not merged completely, it would also qualify as a composite material. A plurality of lamina is referred to as laminae and, when multiple lamina are combined, they form a laminate. Again, the laminate would also qualify as a composite material as it has at least two constituents and the lamina constituents would be the carbon fibers and epoxy.
These terms, and other composite related terms, are to be interpreted in accordance with the definitions of terms in MIL-HDBK-17-1E as of Jan. 23, 1997, Chapter 1, Section 1.7 “Definitions” and those definitions are controlling over other sources such as Webster's Dictionary.
While recent advances have been made in the use of composites comprised of non-metal materials that are lighter in weight and still provide structural support, they too have drawbacks. For example, it is not uncommon for non-metal composites to be very expensive. Another drawback is that many non-metal composites may work well in one structural application and not in another. Further, some non-metal composites are not as easy to work with as traditional structural materials such as aluminum. For example, it is easier to drill holes in aluminum as opposed to many composites, which tend to splinter and fracture.
Thus, metal beams have certain advantages, as do composite beams comprised of, for example, a number of lamina containing carbon fiber filler in an epoxy matrix where the filler in each lamina may be oriented in directions that are different from other lamina. The present invention proposes combining metal and non-metal materials, such as carbon fiber fillers in an epoxy matrix, to overcome a number of the aforementioned drawbacks. This results in laminae formed into a laminate beam that has desirable characteristics of metal and non-metal constituents and at the same time is lighter than a solid metal beam and would be more versatile than the individual components.
The thickness of the metal in a composite beam is a variable that can give rise to a number of uses based upon various characteristics of the metal. In one application, the metal can be sufficiently thick to lend structural support to the laminate. In another application, the metal may be too thin to lend structural support, but still be useful in providing a non-porous barrier to prevent the escape of an enclosed gas.
A laminated beam would be comprised of a metal core, which can be a hollow metal type tube, externally covered by a number of lamina thus forming an outer laminate. Since a cross section of the metal and lamina would yield distinct layers on a macro-scale, the laminated tube could also be classified as a composite material.
In this way, the laminated, or composite, beam could exhibit the preferable characteristics of a non-metallic composite material and that of a metal beam while being lighter than an equivalent all metal beam.
While the use of a composite material utilizing metal and non-metal constituents solves a number of structural problems for a space craft, there are still other issues that remain. For one, there is a limited space within a craft to store critical materials such as compressed gases like nitrogen and oxygen. A laminated beam can be of use in this area.
While composite pressurized gas tanks are well known in the art as evidenced by U.S. Pat. No. 5,822,838 to Seal et al and U.S. Pat. No. 6,401,963 to Seal et al, they are directed to containing the gas and not performing a structural function as, for example, a longeron. In the present invention the laminated beam performs a structural function and the hollow volume can be compartmentalized to contain a compressed gas, or pressure vessel.
In another embodiment, the hollow beam could enclose a compressed gas container. Not only does this make use of a space that otherwise might not be utilized it also provides an extra level of safety. Should the compressed gas container suffer a catastrophic failure, the laminated beam would absorb and could potentially redirect a certain amount of the force transferred by the escaping gas. While the beam may be damaged by such an event, a multiplicity of beams would make it unlikely that any such damage would be structurally catastrophic for a module. Further, the extra shielding provided by the beam could reduce the amount, and velocity of, debris produced by an exploding container.
Accordingly, the present invention is directed to a lighter and more versatile structural beam that can be used to store compressed gases or compressed gas containers.
The multi-purpose laminate beam has an elongated tubular like metallic layer having a generally circular cross section, an external surface, and a length. There is at least one lamina over wrapping, and reinforcing, the external surface of the elongated tubular like metallic layer and extending substantially the length of the elongated tubular like metallic layer. There is also at least one pressure vessel having at least one valve and the pressure vessel and valve are disposed within the elongated tubular like metallic layer. The multi-purpose laminate beam is adapted for use in the construction of an inflatable modular structure.
In an alternate embodiment, opposing dividers are fixedly attached within the elongated tubular like metallic layer and attached to the metallic layer so as to provide a cavity for containing gases. A valve for accessing the cavity is on one divider.
The present invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings.
A beam formed using a single lamina over wrapping an elongated tubular like metallic layer is referred to as a laminate beam. Strictly speaking, in this case, there are not laminae involved and thus not a laminate in the technical sense, however the choice of using the term “multi-purpose laminate beam” is intended to encompass single and multiple bonded lamina cases for simplicity.
Turning to
While
The elongated tubular like metallic layer 12 can be thin and even so thin as to be a liner and have virtually no structural properties apart from the lamina. For example, the metallic layer could serve primarily to as a relatively non-porous barrier to prevent gas leakage.
In the preferred embodiment, the metallic layer 12 is made of aluminum. Metals which may be utilized to form the metallic layer are preferably selected from the group consisting of steel, aluminum, stainless steel, titanium and various combinations and alloys thereof.
The laminate 14 of
The number of lamina used, orientation of the fibers, and thickness of the metallic layer are chosen to meet the requirements of a given set of operational conditions. Where metallic strength is not a prime factor, the laminate itself would be designed to accommodate large axial loads and pressure. In the case where weight is a factor along with a variety of forces being applied from different directions, a metallic inner layer might be desirable to buttress the laminate. The choice of laminates, number of layers, orientation of fibers, and type as well as thickness of metal for an inner layer, are all variables that can be designated by known processes and those skilled in the art.
Turning now to
The container 3 of
Drilling is not a preferred method of making a hole in a composite structure. The structural characteristics of many composites are damaged by the drilling operation. For this reason, the access port 32 is formed during the process of adding lamina to develop the laminate 14. This can be accomplished by a number of well know techniques in the field.
In the preferred embodiment, the container 30 is inserted into a pre-formed multi-purpose laminate beam 10 and held in place with end caps 37 that are fixedly attached to the metal layer 12. The container 30 may be a composite structure or metal. To facilitate a tight fit within the beam, spacers or buffers may be placed between the container 30 and the metal layer 12.
In an alternate embodiment, the metal layer 12 and laminate 14 are formed around the container 30. In this manner, the container 30 is permanently attached to the beam 10.
Referring now to
In the preferred embodiment, the metallic layer 12 and the dividers 38 would be aluminum and the bond would be a weld. In alternate embodiments, the materials would be chosen from metals or metal alloys that could be welded together. The shape of the dividers 38 are dome-like to facilitate an even distribution of the forces resulting from the pressurized gas.
Referring now to
There has thus been described a novel multi-purpose laminate beam. It is important to note that many configurations can be constructed from the ideas presented. Thus, nothing in the specification should be construed to limit the scope of the claims.
