Enhanced Superplastic Forming and Diffusion Bonded Structure

Abstract

The name of the present invention is an enhanced superplastic forming and diffusion bonding structure. An outer panel for a hypersonic vehicle is formed of a superplastic metal alloy such as titanium to accommodate the high thermal stresses of hypersonic flight. The outer panel designed to be reusable on such a vehicle includes an outer skin configured for atmospheric exposure and an inner skin configured for attachment to a structural frame member of the vehicle. An intermediate skin is located between a pair of porous cores. Each porous core is sandwiched between the outer skin and the inner skin, one core being located between the outer skin and the intermediate skin and the other being located between the intermediate skin and the inner skin. An air flow channel (AFC) extends through at least one of the porous cores to cool the outer panel. Each porous core is superplastic formed and diffusion bonded to each other and to their respective pair of skins to form an outer panel having a unified structure.

Description

Technical Field

[0001] The present disclosure relates to superplastic forming and diffusion bonding (SPF / DB) sandwich structures for aerospace applications. Background Art

[0002] The thermal loads imposed on the outer surface of high-speed air transportation vehicles pose significant and ongoing demands for improved thermal management strategies.

[0003] It is known that external structures formed of titanium alloys are effective in accommodating high heat flux environments at supersonic speeds. However, for hypersonic speeds, additional thermal compensation mechanisms are sought. Tiles have been used on spacecraft, specifically for managing thermal loads after reentry into the atmosphere from space. Nickel alloys have also been used in some structures. However, the latter have proven to be heavier and more expensive in terms of their respective structural configurations and fuel requirements. Additionally, such previously used thermal protection devices for hypersonic vehicles are not reusable, thus limiting their use in commercial applications.

[0004] Therefore, there is a need for lower-cost structures that can effectively adapt to temperatures at hypersonic speeds. Summary of the Invention

[0005] According to one aspect of the present disclosure, an exterior panel for a vehicle includes an outer skin configured for atmospheric exposure and an inner skin configured for attachment to a structural frame member of the vehicle. An intermediate skin spaced below the outer skin is sandwiched between the outer skin and the inner skin. A pair of multicellular cores impart strength to the exterior panel, and an air flow channel (AFC) extends through at least one of the multicellular cores. One of the multicellular cores is located between the outer skin and the intermediate skin; the other is located between the intermediate skin and the inner skin. Each core is superplastic formed and diffusion bonded to its respective pair of skins.

[0006] According to another aspect of the present disclosure, a vehicle includes at least one exterior panel having an outer skin configured for atmospheric exposure. The exterior panel includes an inner skin configured for attachment to a structural frame member of the vehicle. An intermediate skin located between a pair of multicellular cores is sandwiched between the outer skin and the inner skin. One multicellular core is located between the outer skin and the intermediate skin, and the other is located between the intermediate skin and the inner skin. An air flow channel (AFC) extends through one of the multicellular cores and is thus located below the outer skin. Each multicellular core is superplastic formed and diffusion bonded to its respective pair of skins, and the multicellular cores impart tensile and compressive strength to the exterior panel.

[0007] According to yet another aspect of the present disclosure, a method of manufacturing an exterior panel for a vehicle includes: providing an outer skin of a superplastic material configured for atmospheric exposure and an intermediate skin of a superplastic material, wherein the intermediate skin is spaced below the outer skin. The method further includes providing an inner skin of a superplastic material, wherein the inner skin is spaced below the intermediate skin and is configured to be attached to a structural frame member of the vehicle. The method further includes providing a pair of core plates (comprising a top and a bottom) of a superplastic material to form a porous core between each of the following: a) the outer skin and the intermediate skin, and b) the intermediate skin and the inner skin. The method further includes joining at least one pair of core plates together by an array of intermittent welds oriented in a predetermined stiffener pattern to form at least one air flow channel adjacent to the outer skin, then fusion welding the edges of the two pairs of core plates together, and securing an expansion tube to one edge of each pair of core plates. Finally, the method includes placing the outer skin, the intermediate skin, and the inner skin, and the core plates loaded between the respective skins, into a forming press, supplying an inert gas into the expansion tube to superplastic form and diffusion bond the skins and the core plates to form a porous core integrally bonded to the outer skin, the intermediate skin, and the inner skin.

[0008] The features, functions, and advantages disclosed herein can be achieved in the examples presented herein, or can be provided in other variations, the details of which can be better understood with reference to the following description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a perspective view of an example of an exterior panel constructed in accordance with the present disclosure and used as an aerodynamically exposed surface of a hypersonic vehicle.

[0010] Figure 2 is a hypersonic vehicle of a type that can employ Figure 1 the exterior panel shown in perspective view.

[0011] Figure 2A is Figure 2 an enlarged view of an insert portion of

[0012] Figure 3 is Figure 1 a perspective exploded view of the components of the exterior panel of

[0013] Figure 4 A cross-sectional side view of a forming fixture for components included during the fabrication of an exterior panel disclosed at the fabrication facility. Figure 3 of the components included during the fabrication of an exterior panel.

[0014] Figure 5A A schematic perspective view of an upper core panel pair that undergoes expansion during the fabrication of an exterior panel.

[0015] Figure 5B A schematic perspective view of a lower core panel pair that undergoes expansion during the fabrication of an exterior panel.

[0016] Figure 6 A perspective view of an exterior panel incorporating a pair of air flow channels located in an upper porous core, the view showing a pair of porous cores formed by an upper and lower core panel pair that fully expand between an outer, intermediate, and inner skin during fabrication.

[0017] Figure 7 Depicts a forming press for a fixture for accommodating Figure 4 to superplastically form and diffusion bond the exterior panel of the present disclosure.

[0018] Figure 8 Shows the sequence of method steps for fabricating Figure 1 an exemplary exterior panel.

[0019] The reference drawings are not necessarily to scale, and any disclosed examples are shown schematically only. Aspects of the disclosed examples may be combined with or substituted for one another and may be within a variety of systems and environments not shown or described herein. Similarly, the following detailed description is merely exemplary and is not intended to limit the application or use. Detailed Description

[0020] The following detailed description includes devices and methods for carrying out the present disclosure. The actual scope of the present disclosure is defined by the appended claims.

[0021] Figure 1 Shows an example of an exterior panel 10 that can be used as a reusable outer surface for a hypersonic vehicle. The exterior panel 10 includes an outer skin 12, a separator herein referred to as an intermediate skin 13, and an inner skin 14. As shown, an upper porous core 15 and a lower porous core 16 are sandwiched between respective skin pairs. In a high heat flux environment associated with hypersonic speeds, the porous cores 15 and 16 provide tensile and compressive strength to the exterior panel 10. As disclosed herein, all described structures can be formed from superplastic materials such as titanium alloys.

[0022] A pair of integrally formed air flow channels 18, 19 are located within the upper porous core 15, and the air flow channels may be adapted to cool the outer panel 10, and specifically to cool the outer skin 12. For example, the air flow channels 18, 19 may be designed to provide a controlled flow of cooling air through the plurality of outer panels 10 when the hypersonic vehicle descends prior to landing.

[0023] Reference is now also made to Figure 2 , an exemplary passenger hypersonic vehicle 20 includes a structural frame member 21, the structural frame member 21 including a pair of wings designed to support the vehicle 20 during flight. The vehicle 20 includes a fuselage 22, a nose 23, and a thrust nozzle 24 of an engine (not shown) to accommodate flight at speeds of 3 to 5 Mach in the stratosphere (i.e., at altitudes of at least 100,000 feet). Figure 2A The illustrated portion Figure 2 depicts an arrangement of a plurality of outer panels 10 that cover and include at least a portion of the wing 21. In the latter illustrated portion, a dashed line through Figure 2A shows an exemplary orientation of the air flow channels 18 and 19 that are otherwise hidden within the plurality of adjacent and aligned outer panels 10. In this case, the inner skin 14 of the outer panel 10 may be welded or otherwise secured to the structural frame member 21 of the vehicle 20, such as a wing. Additionally, each of the outer panels 10 may be welded to one or more adjacent outer panels 10.

[0024] Figure 3 depicts the above-described components of the outer panel 10, which include an outer skin 12, an intermediate skin 13, and an inner skin 14, as well as an upper top core plate 25 and a bottom core plate 26 and a lower top core plate 30 and a bottom core plate 32, which are located between their respective pairs of skins 12, 13, 14. Figure 3 shows a manufacturing stage, which will of course be prior to the formation of the complete outer panel 10 ([[]] Figure 1 ) that includes the upper porous core 15 and the lower porous core 16. Accordingly, it should be understood that the porous cores 15 and 16 of the outer panel 10 are physically constituted by the described upper and lower pairs of top core plates and bottom core plates 25, 26 and 30, 32 ([[]] Figure 3 ), and all of the core plates are composed of a superplastic material such as a titanium alloy.

[0025] During the process of superplastic forming and diffusion bonding (SPF / DB) of the core panels to the skins 12, 13, 14 in the described forming press, the formation of the porous cores 15 and 16 occurs to ensure the permanent integration of the cores 15 and 16 with the outer skin 12, the intermediate skin 13, and the inner skin 14. For this purpose, as shown, the top and bottom core panels 25, 26 and 30, 32 of the upper and lower groups are fusion welded together along their intermittent welds in the first and second orthogonal orientations 34, 36 (lower part) or the first and second orthogonal orientations 38, 39 (upper part). The intermittent welds are essentially spot welds that form small ventilation holes during the SPF / DB manufacturing process to balance air pressure. The first and second orientations 34, 36 of the top and bottom core panels 30 and 32 in the lower part are orthogonally oriented with respect to each other in a predetermined pattern such that applying air pressure between those core panels will form a plurality of spaced-apart porous cores defined by uniformly arranged individual small holes, as further detailed below. On the other hand, the first, second, and third spaced-apart arrays 27, 28, 29 of the intermittent welds 38, 39 of the top and bottom core panels 26 and 26 in the upper part are strategically spaced apart by a predetermined distance to form open weld pattern layouts 18' and 19', which are designed to be air flow channels 18 and 19 in the finished (i.e., manufactured) outer panel 10( Figure 1 ).

[0026] Titanium is a material that has both superplasticity and is suitable for diffusion bonding. Thus, the term "SPF / DB" as used herein refers to a manufacturing process in which, under the application of heat and pressure, solid-state bonding of metal surfaces occurs over a period of time sufficient to form an atomic blend at the joint interface of the parts being joined. Thus, the SPF / DB process involves a diffusion process during superplastic expansion but is not sufficient to physically melt the joined surfaces. In contrast, fusion bonding or fusion welding as used herein refers to the metallurgical bonding of metal surfaces by applying sufficient heat to physically melt the material at its joint interface (i.e., reach a liquid or plastic state when joined together).

[0027] Now referring to Figure 4 , the fixture 40 can be used during the manufacture of the outer panel 10 Figure 3The above-described components. The fixing device 40 is defined by an upper frame member 42 and a lower frame member 44 for supporting the respective outer skin 12, middle skin 13, and inner skin 14. Upper and lower spacers 46, 48 are used as support brackets to ensure a predetermined desired spacing between the respective core plates 25, 26 and 30, 32 and the respective outer skin 12, middle skin 13, and inner skin 14 in which the core plates are placed and held. Subsequently, the skins and core plates are transformed into the outer panel 10 including the porous cores 15 and 16 during a high-pressure, high-temperature SPF / DB manufacturing process. Although the use of upper and lower spacers 46, 48 is shown in the disclosed fixing device 40, manufacturing without such support brackets is also feasible.

[0028] Now referring to Figure 5A , a perspective cross-sectional view of the upper top core plate and bottom core plate 25, 26 depicts the inflation of the later core plates during the manufacture of the outer panel 10 after the expansion tube 50 has been fixed to one edge of the upper top core plate and bottom core plate 25, 26 by fusion welding. Then all edges of the later core plates are fusion welded together, and an inert gas G1 is supplied to the expansion tube 50 under high pressure. Now referring to Figure 6 , it can be understood that the pressure of the gas G1 applied through the expansion tube 50 on the first, second, and third spaced arrays 27, 28, 29 having the intermittent weld orientations 38, 39 as shown effectively produces a protruding portion 47 ( Figure 5A ) of the bottom core plate 26, and a corresponding protruding portion 49 ( Figure 5A ) of the upper core plate 25, ultimately transforming the core plates 25, 26 into a fully formed pore structure 47' ( Figure 6 ) to define the upper porous core 15 ( Figure 6 ).

[0029] Now also referring to Figure 5B , a perspective cross-section of the lower top core plate and bottom core plate 30, 32 depicts their inflation during a simultaneous manufacturing step after a second expansion tube 51 has been fixed to one edge of the top core plate and bottom core plate 30, 32 by fusion welding. Then all edges of the chips 30, 32 are fusion welded together, and an inert gas G2 is supplied to the expansion tube 51 under high pressure. Again referring to Figure 6 , the pressure of the gas G2 on the first and second orientations 34, 36 of the intermittent welds produces a protruding portion 52 ( Figure 5B ) of the bottom core plate 32, and a corresponding protruding portion 54 ( Figure 5B ) of the upper core plate 30, ultimately transforming the later top core plate and bottom core plate into a fully formed small pore structure 52' ( Figure 6 ) to define the lower porous core 16 ( Figure 6 ).

[0030] It is worth noting that all Figure 6 The visible outlines or demarcation lines between the various components, namely the outer skin 12, the intermediate skin 13 and the inner skin 14, and their respective upper and lower support cores 15, 16, shown schematically in FIG. 1 are only used to describe how the components are assembled together prior to the SPF / DB manufacturing process. In fact, after such manufacturing of the outer panel 10, any cross-section taken will not show visible outlines, because the components will then be integrally joined together into a unified structure.

[0031] Continue to refer to Figure 6 It will be appreciated that the final shape of the individual apertures 47', 52' of the cores 15, 16 of the superplastic formed and diffusion bonded outer panels 10 is constrained by the above-described intermittent welds having the first and second orientations 34, 36 and the first, second and third arrays 27, 28, 29, respectively, and the outer skin 12, the intermediate skin 13 and the inner skin 14. In the disclosed example, the final shape of the airflow passage is also controlled by the above-described predetermined weld pattern.

[0032] Now also refer to Figure 7 The superplastic forming press 60 includes a lower member, such as a containment box 62, and an upper member, such as a containment box cover 64 configured to be fixed to the containment box 62. It should be understood that the prefabricated outer panel 10 ( Figure 3 ) of the above components Figure 4 The fixture 40 in is inserted into a superplastic forming press 60 to manufacture each finished outer panel 10 by the SPF / DB process. For this purpose, an inert gas G, such as argon, can be used to pressure-form the outer panel 10; such a gas is introduced into the upper and lower core plate groups described at pressures G1 and G2, respectively. The pressures of the latter can be equal, especially if such a structure consists of a homogeneous superplastic formable material, such as the titanium alloy described. In addition to argon, other inert gases may also be suitable for the above-mentioned components.

[0033] Continue to refer to Figure 7 Before pressurizing the superplastic forming press 60, the atmosphere is first purged from the superplastic forming press 60 using a non-corrosive gas (e.g., argon) because the atmosphere can be corrosive at SPF / DB manufacturing temperatures approaching 1700°F. For this purpose, purge pipes and vacuum pipes such as vacuum pipe 56, purge pipe 58, upper purge pipe 66, and purge port 68 are schematically shown as exemplary structures for accommodating pre-manufacturing purges. After each instance of SPF / DB manufacturing of the exterior panel 10 is completed, the completed exterior panel 10 (e.g., Figure 1 ) is removed from the superplastic forming press and trimmed. Figure 1Shows the completed and fully trimmed outer panel 10, i.e., removed from the superplastic forming press 60 and the fixture 40, and the expansion tubes 50 removed.

[0034] It can be noted that during hypersonic flight, the steady-state operating temperature of the outer skin 12 of the outer panel 10 made of titanium alloy can be as high as 1100 to 1200°F. The thickness of the outer skin 12 can range from five thousandths of an inch up to about sixty thousandths of an inch. Additionally, the air flow channels can be directed (not shown) to operate only during the descent of the vehicle 20 for cooling. The thickness of the core plates 25, 26 and 30, 32 can be in the range of 1 mm or forty thousandths of an inch, and the thickness of the intermediate skin 13 and the inner skin 14 can be comparable to or slightly less than the thickness of the outer skin 12. During the SPF / DB manufacturing process, the pressure of gases G1 and G2 can be between 200 - 500 psi.

[0035] Now referring to Figure 8 , a method of manufacturing an exemplary outer panel 10 ( Figure 2 ) for a vehicle 20 ( Figure 1 ) includes step 150 of providing an outer skin 12 of superplastic material (such as titanium alloy) configured for atmospheric exposure. The method further provides: step 152 of providing an intermediate skin 13 of superplastic material spaced below the outer skin 12; and step 154 of providing an inner skin 14 of superplastic material that attaches the vehicle 20 to a structural frame member (wing 21). The method next includes step 156 of providing upper and lower top and bottom core plate pairs 25, 26 and 30, 32 of superplastic material as well, each pair for forming one of two porous cores 15, 16 between the outer skin 12 and the intermediate skin 13, and between the intermediate skin 13 and the inner skin 14. Next, according to step 158, the respective core plate pairs 25, 26 and 30, 32 are joined together via intermittent welds having a predetermined welding pattern ( Figure 3 ).

[0036] According to step 160, next, each of the expansion tubes 50 and 51 is fixed to one edge of the respective core plates 25, 26 and 30, 32, and in step 162, fusion welding is applied to all edges of the respective core plate pairs. In step 164, the outer skin 12, the intermediate skin 13 and the inner skin 14 are placed in the fixture 40 together with the respective core plates 25, 26 and 30, 32, which is then placed in the forming press 60. In step 166, the superplastic forming press 60 is purged, and inert gases G1 and G2 are supplied to each of the respective expansion tubes 50, 51 to superplastically pressurize all the skins and core plates to form the porous cores 15, 16 integrally bonded to the outer skin 12, the intermediate skin 13 and the inner skin 14.

[0037] As described above, during the SPF / DB process, the pressure may reach 200 - 500 psi during the superplastic forming of the above-described outer panel 10.

[0038] Although only some examples and method steps are described herein, the present disclosure may allow still other variations and modifications that are neither described nor implied. For example, although not described above, the outer panel 10 may have other porous core configurations, resulting in a significantly lighter, simpler, and less expensive structure. For example, in some contemplated examples, the porous core may be formed of only a single core plate layer. Additionally, an inert gas other than argon may be used in the SPF / DB process to fabricate the outer panel 10. Moreover, it is contemplated that a superplastic formable material composition other than a titanium material may be employed to fabricate the disclosed outer panel 10, to a certain extent such that the high strength and tensile properties of this composition can remain intact in an environment exceeding 1200 degrees Fahrenheit. Finally, as can be understood by those skilled in the art, some other feasible methods not described herein may be contemplated to fabricate the outer panel 10.

[0039] Clause 1. An outer panel of a vehicle, the outer panel comprising:

[0040] An outer skin configured for exposure to the atmosphere;

[0041] An intermediate skin spaced below the outer skin;

[0042] An inner skin spaced below the intermediate skin and configured for attachment to a structural frame member of the vehicle;

[0043] A first superplastic formed porous core sandwiched between the outer skin and the intermediate skin, and a second superplastic formed porous core sandwiched between the intermediate skin and the inner skin;

[0044] Wherein the porous cores are superplastic formed and diffusion bonded to the outer skin and the intermediate skin, and the intermediate skin and the inner skin respectively, and wherein at least one of the porous cores includes an air flow channel.

[0045] Clause 2. The outer panel according to Clause 1, wherein the outer skin, the intermediate skin, and the inner skin are formed of a superplastic material.

[0046] Clause 3. The outer panel according to Clause 1 or 2, wherein the air flow channels are integrally formed within the outer panel.

[0047] Clause 4. The outer panel according to any one of Clauses 1 - 3, wherein the porous cores impart tensile and compressive strength to the outer panel.

[0048] Clause 5. The external panel according to any one of Clauses 1-4, wherein there are at least two air flow channels under the external skin.

[0049] Clause 6. The external panel according to any one of Clauses 1-5, wherein the air flow channels are configured to cool the external panel.

[0050] Clause 7. The external panel according to any one of Clauses 1-6, wherein the air flow channels are formed by three arrays of intermittent welds on a pair of core plates, and each array is spaced apart from each other.

[0051] Clause 8. A vehicle having at least one external panel, the at least one external panel comprising:

[0052] An external skin configured for exposure to the atmosphere;

[0053] An intermediate skin spaced below the external skin;

[0054] An internal skin spaced below the intermediate skin and configured to be attached to a structural frame member of the vehicle;

[0055] A first superplastic formed porous core sandwiched between the external skin and the intermediate skin, and a second superplastic formed porous core sandwiched between the intermediate skin and the internal skin;

[0056] The intermediate skin and the porous core are configured to provide tensile and compressive strength to the external panel;

[0057] Wherein the porous cores are superplastic formed and diffusion bonded to the external skin and the intermediate skin respectively, and the intermediate skin and the internal skin, and one of the porous cores includes air flow channels; and wherein the air flow channels are located under the external skin and cool it.

[0058] Clause 9. The vehicle according to Clause 8, wherein the vehicle is a hypersonic vehicle having a plurality of external panels, and wherein each external panel is fusion welded to at least one other external panel.

[0059] Clause 10. The vehicle according to Clause 9, wherein each air flow channel within each of the plurality of external panels is integrally formed.

[0060] Clause 11. The vehicle according to any one of Clauses 8-10, wherein the air flow channels are configured to cool the external panel.

[0061] Clause 12. The vehicle according to any one of Clauses 8-11, wherein the air flow channels are formed by three arrays of intermittent welds on a pair of core plates, and each array is spaced apart from each other.

[0062] Clause 13. A method of manufacturing an exterior panel for a vehicle, the method comprising:

[0063] Providing an outer skin of a superplastic material configured for atmospheric exposure;

[0064] Providing an intermediate skin of a superplastic material spaced below the outer skin;

[0065] Providing an inner skin of a superplastic material attached to a structural frame member of the vehicle;

[0066] Providing a first pair and a second pair of core plates of a superplastic material to form a porous core between each of the outer skin and the intermediate skin, and the intermediate skin and the inner skin;

[0067] Combining one of the pairs of core plates with intermittent welds oriented in a predetermined stiffener pattern, the intermittent welds being sufficient to form at least one air flow channel adjacent to the outer skin;

[0068] Providing and securing an expansion tube on one edge of each of the pairs of core plates, and fusion welding all edges of each pair of core plates; and

[0069] Placing the outer skin, the intermediate skin, and the inner skin, and their respective core plates, into a forming press, supplying an inert gas into the expansion tubes to superplastically form and diffusion bond the outer skin, the intermediate skin, and the inner skin with the core plates to form a porous core integrally bonded to the outer skin, the intermediate skin, and the inner skin.

[0070] Clause 14. The method according to clause 13, wherein the air flow channel is integrally formed within the exterior panel.

[0071] Clause 15. The method according to clause 13 or 14, wherein all components are formed of a titanium alloy.

[0072] Clause 16. The method according to any one of clauses 13 - 15, wherein the porous core imparts tensile and compressive strength to the exterior panel.

[0073] Clause 17. The method according to any one of clauses 13 - 16, wherein there are at least two air flow channels in one of the porous cores.

[0074] Clause 18. The method according to any one of clauses 13 - 17, wherein the air flow channels are formed by three arrays of intermittent welds on a pair of core plates, each array being spaced apart from each other.

[0075] Clause 19. The method according to clause 18, wherein during the manufacture of the exterior panel, each of the three arrays of intermittent welds secures the pair of core plates together.

[0076] Clause 20. The method according to any one of Clauses 13 - 19, wherein the air flow passage is configured to cool the outer skin.

Claims

1. An outer panel (10) of a vehicle (20), the outer panel comprising: An outer skin (12) configured for exposure to the atmosphere; An intermediate skin (13) spaced below the outer skin; An inner skin (14) spaced below the intermediate skin and configured to be attached to a structural frame member (21) of the vehicle (20); A first porous core (15) sandwiched between the outer skin (12) and the intermediate skin (13), the first porous core comprising a pair of superplastic material core plates joined together by intermittent welds, the intermittent welds joining the first pair of core plates together to form a first spaced array, a second spaced array, and a third spaced array of the intermittent welds; And a second porous core (16) sandwiched between the intermediate skin (13) and the inner skin (14), the second porous core comprising a pair of superplastic material core plates joined together by intermittent welds; and Wherein the first porous core (15) is superplastically formed and diffusion bonded to the outer skin and the intermediate skin (12, 13), and the second porous core (16) is superplastically formed and diffusion bonded to the intermediate skin and the inner skin (13, 14), and wherein the superplastically formed first porous core comprises a first air flow channel (18) and a second air flow channel (19), the first air flow channel (18) being formed between the first spaced array and the second spaced array below the outer skin, and the second air flow channel (19) being formed between the second spaced array and the third spaced array below the outer skin.

2. The outer panel (10) according to claim 1, wherein the outer skin, the intermediate skin, and the inner skin (12, 13, 14) are formed of a superplastic material.

3. The outer panel (10) according to claim 1, wherein the first air flow channel (18) and the second air flow channel (19) are integrally formed within the outer panel (10).

4. The outer panel (10) according to claim 1, wherein the first porous core (15) and the second porous core (16) impart tensile and compressive strength to the outer panel (10).

5. The outer panel (10) according to claim 1, wherein the first air flow channel (18) and the second air flow channel (19) are configured to provide a controlled cooling air flow through a plurality of the outer panels.

6. The outer panel (10) according to claim 1, wherein the first air flow channel (18, 19) and the second air flow channel (19) are configured to cool the outer panel (10).

7. The outer panel (10) according to any one of claims 1-6, wherein the outer panel has only two air flow channels.

8. A vehicle (20) having at least one outer panel (10), the at least one outer panel comprising: An outer skin (12) configured for exposure to the atmosphere; An intermediate skin (13) spaced below the outer skin (12); An inner skin (14), which is spaced below the intermediate skin (13) and configured to be attached to a structural frame member (21) of the vehicle (20); A first pair of core plates forming a first porous core (15) by superplastic forming, the first porous core (15) by superplastic forming being sandwiched between the outer skin (12) and the intermediate skin (13), and a second pair of core plates forming a second porous core (16) by superplastic forming, the second porous core (16) by superplastic forming being sandwiched between the intermediate skin (13) and the inner skin (14), wherein the first pair of core plates are superplastic materials joined together by intermittent welds, the intermittent welds joining the first pair of core plates together to form a first spaced array, a second spaced array, and a third spaced array of the intermittent welds, and the second pair of core plates are superplastic materials joined together by intermittent welds; The intermediate skin (13), the first porous core (15), and the second porous core (16) are configured to provide tensile and compressive strength to the outer panel (10); Wherein the first porous core (15) and the second porous core (16) are superplastic formed and diffusion bonded to the outer skin and the intermediate skin (12, 13), and the intermediate skin and the inner skin (13, 14), respectively, wherein the first porous core (15) by superplastic forming includes a first air flow channel (18) formed between the first spaced array and the second spaced array and a second air flow channel (19) formed between the second spaced array and the third spaced array; and wherein the first air flow channel (18) and the second air flow channel (19) are located below the outer skin (12), adjacent thereto and cooling it.

9. The vehicle (20) according to claim 8, wherein the vehicle is a hypersonic vehicle having a plurality of outer panels (10), and wherein each outer panel (10) is fusion welded to at least one other outer panel (10).

10. The vehicle (20) according to claim 9, wherein each of the first air flow channel (18) and the second air flow channel (19) within each of the plurality of outer panels (10) is integrally formed.

11. The vehicle (20) according to claim 8, wherein the first air flow channel (18) and the second air flow channel (19) are configured to cool the outer panel (10).

12. The vehicle (20) according to any one of claims 8-11, wherein the first air flow channel (18) and the second air flow channel (19) are configured to provide a controlled cooling air flow through the plurality of outer panels.

13. A method of manufacturing an outer panel (10) for a vehicle (20), the method comprising: Providing an outer skin (12) of a superplastic material configured for atmospheric exposure; Providing an intermediate skin (13) of a superplastic material spaced below the outer skin (12); Provide an inner skin (14) of superplastic material attached to a structural frame member (21) of the vehicle (20); Provide a first pair and a second pair of superplastic material core plates (25, 26) (30, 32) to form a first porous core (15) and a second porous core (16) between each of the outer skin (12) and the intermediate skin, and the intermediate skin and the inner skin (14); Combine one of the first pair and the second pair of superplastic material core plates with a first spaced array, a second spaced array, and a third spaced array of intermittent welds oriented in a predetermined stiffener pattern, the intermittent welds being sufficient to form a first air flow channel (18) formed between the first spaced array and the second spaced array and a second air flow channel (19) formed between the second spaced array and the third spaced array, the first air flow channel (18) and the second air flow channel (19) being adjacent to and located below the outer skin (12); Provide and fix an expansion tube (50), (51) to one edge of each of the first pair and the second pair of superplastic material core plates (25, 26) (30, 32), and fusion weld all edges of each pair of core plates (25, 26) (30, 32); and Place the outer skin (12), the intermediate skin (13), and the inner skin (14) and their respective core plates (25, 26) (30, 32) into a forming press (60), supply an inert gas into the expansion tubes (50, 51) to superplastic form and diffusion bond the outer skin, intermediate skin, and inner skin (12, 13, 14) to the core plates (25, 26) (30, 32) to form the first porous core (15) and the second porous core (16) integrally bonded to the outer skin, intermediate skin, and inner skin (12, 13, 14).

14. The method according to claim 13, wherein the first air flow channels (18, 19) and the second air flow channel (19) are integrally formed within the outer panel (10).

15. The method according to claim 13, wherein all components (12, 13, 14, 15, 16) are formed of a titanium alloy.

16. The method according to claim 13, wherein the first porous core (15) and the second porous core (16) impart tensile and compressive strength to the outer panel (10).

17. The method according to claim 13, wherein only two air flow channels (18, 19) are provided in one of the first porous core (15) and the second porous core (16).

18. The method according to claim 13, wherein the first air flow channel (18) and the second air flow channel (19) are configured to provide a controlled cooling air flow through a plurality of the outer panels.

19. The method according to claim 18, wherein during manufacture of the outer panel (10), each of the three arrays (27, 28, 29) of intermittent welds (38, 39) secures the pair of core plates (25, 26) together.

20. The method according to any one of claims 13 - 19, wherein the first air flow channel (18) and the second air flow channel (19) are configured to cool the outer skin (12).

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