Enhanced aerodynamic pointy cone nozzles, engines including enhanced aerodynamic pointy cone nozzles, and vehicles including engines

Abstract

An enhanced aerodynamic cone nozzle includes a throat, a central body extending rearward from the throat, an inner expansion surface defined by the central body, an outer expansion surface outside the inner expansion surface, and an expansion cavity defined between the inner and outer expansion surfaces. An engine includes a high-pressure chamber and an enhanced aerodynamic cone nozzle. A vehicle for supersonic flight includes an engine with an enhanced aerodynamic cone nozzle.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 941,386, filed November 27, 2019, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure generally relates to propulsion systems having exhaust nozzles. More specifically, the invention relates to an enhanced aerospike nozzle, an engine including the enhanced aerospike nozzle, and a vehicle including the engine. Background Technology

[0004] The ability to recover and reuse upper stages of multi-stage rocket systems (e.g., the second stage of a two-stage rocket system) remains a significant unresolved technological gap for the industry. Reusable upper stages of multi-stage rockets are challenging due to the harsh reentry environment and the performance losses associated with the increased structural mass required for robust reusability. Upper stages are typically built with minimal structural and complexity because any mass addition to the second stage results in a 1:1 reduction in payload capacity. Therefore, reusable upper stages require substantial additional functionality, but minimal mass addition.

[0005] Traditional upper-stage rockets use very large nozzles to maximize engine efficiency in a vacuum. These large nozzles are typically very thin and difficult to protect during upper-stage reentry. If upper-stage recovery includes a propulsion landing, a separate propulsion system is required because the large nozzles can cause severe flow separation and lateral loads in the atmosphere.

[0006] Plug nozzles, such as pneumatic cone nozzles, are a highly compensated nozzle design that minimizes nozzle efficiency losses due to pressure resistance; in the thrust equation middle This feature also allows the nozzle to operate in the atmosphere at low throttling levels, whereas flow separation would occur in conventional high expansion ratio nozzles, leading to unstable thrust oscillations, unstable thrust vectors, and damage to the engine or vehicle.

[0007] Pneumatic cone nozzles have been studied since before 1960. Analytical design methods (e.g., G. Angelino, Approximate Method for Plug Nozzle Design, AIAA Journal, Vol. 2, No. 10, pp. 1834–1835 (1964)) and modern first-principles design tools (e.g., NASA's Aerospike Design and Performance Tool (ADAPT), 2008) have been developed, and computational fluid dynamics (CFD) predictive analysis has been performed (e.g., M. Onofri et al., Plug Nozzles: Flow Characteristics and Engine Performance Summary, AIAA-2002-0584 (2002)). Pneumatic cone nozzles have also been ground-tested in many high-profile projects. To name just a few, these projects include the 25 klbf thrust aerodynamic cone demonstrator (AFRPL-TR-76-05) developed under the Air Force O2 / H2 Advanced Mobility Propulsion Technology program, the 250 klbf thrust modified J-2 engine (AFRPL-TR-67-280) that forms the basis of Rocketdyne’s initial proposal for the Space Shuttle’s main engine, and the XRS-2200 linear aerodynamic cone nozzle developed as part of the X-33 program.

[0008] Referring to Figures 1-3, a prior art pneumatic cone engine 112 includes at least one high-pressure chamber 136 (e.g., a combustion chamber) and a pneumatic cone nozzle 110. The pneumatic cone nozzle 110 includes at least one initial nozzle portion 160 through which exhaust gas initially exits the high-pressure chamber 136; and a secondary nozzle portion 162 downstream of the initial nozzle portion 160. The initial nozzle portion 160 includes at least one throat 124, one or more surfaces 164, 166 downstream of the throat 124, and an outer rear end 168 defined by the throat 124 and / or at least one of the surfaces 164, 166. The secondary nozzle portion 162 includes a central body 128 (e.g., a pneumatic cone) defining an internal expansion surface 126.

[0009] Referring to Figure 2, a typical prior art pneumatic cone nozzle 110 includes an initial nozzle portion 160 in the form of a convergent-divergent nozzle. In such prior art embodiments, a throat 124 defines a transition between an upstream convergent section having opposing convergent surfaces 170, 172 and a downstream divergent section having opposing divergent surfaces 164, 166. The divergent surfaces 164, 166 define an initial nozzle cavity 125 therebetween. The inner divergent surface 164 abuts (e.g., is at least substantially flush) with an inner expansion surface 126 defined by a central body 128 of the secondary nozzle portion 162. The outer rear end 168 of the initial nozzle portion 160 is defined by the rear end of a wall defining the outer divergent surface 166. In some cases, at least a portion of the outer divergent surface 166 is defined by a cowling, shield, and / or other component of a vehicle on which the pneumatic cone engine 112 is mounted. In prior art embodiments similar to those shown in Figure 2, the initial nozzle portion 160 is sometimes referred to as the “main nozzle.”

[0010] Referring to FIG3, in other embodiments of the prior art pneumatic conical nozzle 110, the exterior of the throat 124 defines the outer rear end 168 of the initial nozzle portion 160. That is, the diverging section of the initial nozzle portion 160 is not included in the outer diverging surface 166 included in the prior art pneumatic conical nozzle as shown in FIG2.

[0011] In some embodiments of the prior art pneumatic cone engine 112, including those shown in Figures 1-3, the engine 112 has a so-called "multi-plug group" configuration. In these configurations, the engine 112 includes a plurality of discrete high-pressure chambers 136 spaced apart from each other and a plurality of discrete initial nozzle portions 160 spaced apart from each other. Each initial nozzle portion 160 is disposed relative to a corresponding high-pressure chamber 136 and is configured to discharge gas exiting the corresponding high-pressure chamber 136. Each pair of high-pressure chambers 136 and initial nozzle portions 160 is referred to in the art as a "thrust can". The initial nozzle portion 160 of each thrust can includes a discrete throat 124 that extends annularly around an axis 174 of the initial nozzle portion 160. In such prior art embodiments, the converging surfaces 170, 172 of the throat 124 form a continuous surface extending annularly around the axis 174, and the diverging surfaces 164, 166 of the throat 124 form a continuous surface extending annularly around the axis 174. In some cases, the converging surfaces 170, 172 and / or the diverging surfaces 164, 166 are axisymmetric with respect to the axis 174. In an annular aerodynamic cone configuration, such as the configuration shown in Figure 1, the thrust canisters are circumferentially spaced around the centerline 116 of the vehicle on which the engine 112 is mounted. In a linear aerodynamic cone configuration, the thrust canisters are linearly spaced along a plane parallel to the centerline 116 of the vehicle.

[0012] In other embodiments of the prior art pneumatic cone engine 112, the engine 112 includes a single high-pressure chamber 136 and a single initial nozzle portion 160 having a single throat 124. In such prior art embodiments, the converging surfaces 170, 172 of the throat 124 are discrete surfaces relative to each other, and the diverging surfaces 164, 166 of the throat 124 are discrete surfaces relative to each other. In an annular pneumatic cone configuration, the high-pressure chamber 136 and the throat 124 each extend annularly around the centerline 116 of a vehicle on which the engine 112 is mounted. In a linear pneumatic cone configuration, the high-pressure chamber 136 and the throat 124 each extend linearly in a respective plane parallel to the centerline 116 of the vehicle.

[0013] As shown in Figure 2, during vacuum operation of a typical prior art pneumatic cone engine 112, the exhaust gas... Leaving the initial nozzle cavity 125, it expands across the Mach wave and... It was ejected into the vacuum. and The angle between them is determined by the Prandtl-Meyer expansion angle.

[0014]

[0015] in It is the Prandtl-Meyer function:

[0016] .

[0017] If engine 112 operates in a complete vacuum, then The Prandtl-Meyer function is close to its theoretical maximum.

[0018]

[0019] Furthermore, for a typical internal module expansion ratio, the net rotation angle θ can be greater than 90°. The exhaust gas deflects outside the outer rear end 168 of the initial nozzle chamber 125, resulting in a performance loss for the prior art pneumatic cone engine 112 when operating in a vacuum. To improve performance in a vacuum, it is necessary to increase the area ratio of the engine 112. This would require positioning the throat 124 at a large diameter relative to the centerline 115. However, at such a large diameter, the dimensions associated with the throat 124 become very small and difficult to manufacture.

[0020] A high-performance nozzle that can operate in both vacuum and atmosphere and is easily protected during reentry is needed to enable the efficient recovery and reuse of the upper stage rocket.

[0021] The various aspects of the present invention address these and other problems. Summary of the Invention

[0022] According to one aspect of the invention, an enhanced pneumatic cone nozzle includes a throat, a central body extending rearward from the throat, an inner expansion surface defined by the central body, an outer expansion surface outside the inner expansion surface, and an expansion cavity defined between the inner expansion surface and the outer expansion surface.

[0023] According to another aspect of the invention, an engine includes a high-pressure chamber and an enhanced pneumatic cone nozzle for discharging gas generated by the high-pressure chamber. The enhanced pneumatic cone nozzle includes a throat, a central body extending rearward from the throat, an inner expansion surface defined by the central body, an outer expansion surface outside the inner expansion surface, and an expansion cavity defined between the inner expansion surface and the outer expansion surface.

[0024] According to another aspect of the invention, a vehicle includes an engine having a high-pressure chamber and an enhanced pneumatic cone nozzle for discharging gas generated in the high-pressure chamber. The enhanced pneumatic cone nozzle includes a throat, a central body extending rearward from the throat, an inner expansion surface defined by the central body, an outer expansion surface outside the inner expansion surface, and an expansion cavity defined between the inner and outer expansion surfaces.

[0025] According to another aspect of the invention, the reusable upper stage rocket of the multi-stage rocket system includes an engine configured for space propulsion and atmospheric landing propulsion.

[0026] In addition to or as a substitute for one or more of the features described above, other aspects of the invention may include one or more of the following features, individually or in combination:

[0027] - The size of the central body decreases continuously in the rearward direction;

[0028] - The inner expansion surface and the outer expansion surface are configured such that the expansion cavity has a width that increases continuously in the rearward direction;

[0029] - The outer expansion surface and the inner expansion surface extend backward as far as possible;

[0030] - The outer expansion surface extends further back than the inner expansion surface;

[0031] - The inner expansion surface extends further backward than the outer expansion surface;

[0032] - The expansion chamber extends circumferentially around the central body and is concentrically aligned with the central body around the centerline of the nozzle;

[0033] - The enhanced pneumatic cone nozzle is a linear pneumatic cone nozzle;

[0034] - The throat is included in the initial nozzle portion of the enhanced pneumatic cone nozzle, and the external expansion surface extends in the rearward direction from the outer rear end of the initial nozzle portion;

[0035] - The launch vehicle is the upper-stage rocket;

[0036] - The central body is a truncated annular aerodynamic cone with a central body base that partially defines the rear end of the vehicle;

[0037] - The engine is recessed into the base surface of the vehicle;

[0038] - The outer expansion surface is integrally connected to the vehicle, and the enhanced pneumatic cone nozzle includes a seal that allows the center body to be mounted via a universal joint while allowing the outer expansion surface to remain fixed relative to the vehicle; and

[0039] - The seals allow the engine to be mounted relative to the vehicle using a universal joint.

[0040] These and other aspects of the invention will become apparent from the accompanying drawings and detailed description provided below. Attached Figure Description

[0041] Figure 1 schematically illustrates a prior art pneumatic cone engine.

[0042] Figure 2 schematically shows a portion of the prior art aerodynamic cone engine of Figure 1.

[0043] Figure 3 schematically shows a portion of another prior art pneumatic cone engine.

[0044] Figure 4 It is a perspective view of a vehicle including an engine with an enhanced pneumatic cone nozzle.

[0045] Figure 5 During vacuum operation (to the left of the centerline) and atmospheric operation (to the right of the centerline) Figure 4 A schematic cross-sectional view of a portion of the vehicle.

[0046] Figure 6 yes Figure 4 A cross-sectional perspective view of the rear of the vehicle.

[0047] Figure 7 schematically shown Figure 4 It is part of an enhanced aerodynamic cone engine.

[0048] Figure 8 This schematically illustrates a portion of another enhanced aerodynamic cone engine. Detailed Implementation

[0049] refer to Figure 4 and Figure 5 This disclosure describes an enhanced pneumatic cone nozzle 10, an engine 12 including the enhanced pneumatic cone nozzle 10, and a vehicle 14 including the engine 12.

[0050] refer to Figure 4-6 The launch vehicle 14 is a rocket (e.g., a multi-stage rocket, a single-stage-to-orbit (SSTO) rocket, an upper-stage rocket, a booster rocket, etc.), a missile, a spacecraft, an aircraft, or another launch vehicle designed to travel (e.g., fly) at speeds up to at least supersonic speeds (e.g., supersonic, hypersonic, reentry speed, etc.) in atmospheric, suborbital, orbital, and / or outer space environments. In the illustrated embodiment, the launch vehicle 14 is a second-stage rocket of a two-stage rocket (not shown). The launch vehicle 14 (hereinafter referred to as "second-stage rocket 14") extends along a centerline 16 between its front end 18 and its opposite rear end 20. The second-stage rocket 14 includes a payload 22 facing the front end 18 and an engine 12 facing the rear end 20.

[0051] refer to Figure 7 and Figure 8 The enhanced pneumatic cone nozzle 10 includes at least one initial nozzle portion 60 through which exhaust initially exits at least one high-pressure chamber 36, and a secondary nozzle portion 62 downstream of the initial nozzle portion 60.

[0052] The initial nozzle portion 60 includes at least one throat 24, one or more surfaces 64, 66 extending downstream of the throat 24, and an outer rear end 68 defined by the throat 24 and / or at least one of the surfaces 64, 66. The secondary nozzle portion 62 includes a central body 28 (e.g., a pneumatic cone) defining an inner expansion surface 26. The secondary nozzle portion 62 also includes an outer expansion surface 30 outside the inner expansion surface 26 and an expansion cavity 32 defined between the inner expansion surface 26 and the outer expansion surface 30.

[0053] refer to Figure 7In some embodiments, the initial nozzle portion 60 of the nozzle 10 is in the form of a convergent-divergent nozzle and / or a main nozzle. In such embodiments, the throat 24 defines a transition between an upstream convergent section having opposing convergent surfaces 70, 72 and a downstream divergent section having opposing divergent surfaces 64, 66. The divergent surfaces 64, 66 define an initial nozzle cavity 25 therebetween. The inner divergent surface 64 abuts (e.g., is at least substantially flush) with the inner expansion surface 126 defined by the central body 128 of the secondary nozzle portion 62. The outer expansion surface 30 is connected (e.g., directly connected, indirectly connected via a seal, etc.) and extends in a rearward direction from the outer rear end 68 of the initial nozzle portion 60, which is defined by the rear end of the outer divergent surface 66. The inflection point is defined as the intersection of the outer divergent surface 66 of the initial nozzle portion 60 and the outer expansion surface 30 of the secondary nozzle portion 62.

[0054] refer to Figure 8 In other embodiments, the initial nozzle portion 60 is configured such that the outer portion 68 of the throat 24 defines the outer rear end 68 of the initial nozzle portion 60. That is, the initial nozzle portion 60 is not included in the... Figure 7 The nozzle shown includes an outer diverging surface 66. The outer expansion surface 30 is connected (e.g., directly connected, indirectly connected via a seal, etc.) and extends in the rearward direction from the outer rear end 68 of the initial nozzle portion 60.

[0055] Return to reference Figure 5 and Figure 6 The central body 28 defining the inner expansion surface 26 of the enhanced aerodynamic cone nozzle 10 is an aerodynamic cone (e.g., annular aerodynamic cone, linear aerodynamic cone) or another type of plug nozzle. The profile of the inner expansion surface 26 will depend on the specific application and can be selected and / or optimized using the method of Angelino (1964) and / or other methods known in the art. In the illustrated embodiment, the central body 28 is a truncated annular aerodynamic cone having a central body base 34 that partially defines the rear end 20 of the second-stage rocket 14. The radius r1 of the front portion of the central body 28 is greater than the radius r2 of the rear portion of the central body 28. The dimensions (e.g., radius) of the central body 28 decrease continuously in the rearward direction.

[0056] The inner expansion surface 26 and outer expansion surface 30 of the secondary nozzle portion 62 of the enhanced pneumatic conical nozzle 10 are configured such that the expansion cavity 32 defined therebetween has a width (e.g., dimension in a direction perpendicular to the centerline 16) that increases (e.g., increases continuously) in the rearward direction. The profile of the outer expansion surface 30 will depend on the specific application and can be selected and / or optimized using the method of Angelino (1964) and / or other methods known in the art. That is, known methods for selecting and / or optimizing the profile of the inner expansion surface 26 can be applied when selecting and / or optimizing the profile of the outer expansion surface 30. In some embodiments including the illustrated embodiment, the outer expansion surface 30 extends rearward as far as the inner expansion surface 26. In other embodiments not shown in the figures, the outer expansion surface 30 extends rearward further than the inner expansion surface 26, or the inner expansion surface 26 extends rearward further than the outer expansion surface 30. In the illustrated embodiment, the expansion cavity 32 extends circumferentially around the central body 28 and is concentrically aligned with the central body 28 surrounding the centerline 16 of the second-stage rocket 14.

[0057] Engine 12 includes a high-pressure chamber 36 (e.g., a combustion chamber) and an enhanced aerodynamic cone nozzle 10. The high-pressure chamber 36 generates gas that is discharged through the enhanced aerodynamic cone nozzle 10.

[0058] The high-pressure chamber 36 may be in the form of an annular ring, a segmented ring, a separate thrust chamber, or any other configuration in which the inwardly expanding surface 26 and the outwardly expanding surface 30 provide supersonic flow.

[0059] refer to Figure 7 and Figure 8 In the illustrated embodiment, engine 12 includes a single high-pressure chamber 36 and a single initial nozzle portion 60 having a single throat 24. The nozzle 10 is in the form of an annular aerodynamic cone. Thus, the high-pressure chamber 36 and the throat 24 each extend annularly around the centerline 16 of the second-stage rocket 14 (see...). Figure 4-6 The converging surfaces 70 and 72 of the throat 24 are discrete surfaces relative to each other. Figure 8 In one embodiment, the divergent surfaces 64 and 66 of the throat 24 are also discrete surfaces relative to each other.

[0060] In other embodiments, the engine 12 has a so-called "multi-plug group" configuration similar to, for example, the prior art embodiments shown in Figures 1 and 2. In such embodiments, the engine 12 includes a plurality of discrete high-pressure chambers 36 spaced apart from each other, and a plurality of discrete initial nozzle portions 60 spaced apart from each other. Each initial nozzle portion 60 is disposed relative to a corresponding high-pressure chamber 36 and is configured to exhaust gas leaving the corresponding high-pressure chamber 36. Each high-pressure chamber 36 and initial nozzle portion 60 pair forms a so-called "thrust canister". The initial nozzle portion 60 of each thrust canister may include a discrete throat 24 extending annularly around the axis of the corresponding initial nozzle portion 60. The converging surfaces 70, 72 of the throat 24 form a continuous surface extending annularly around the axis of the corresponding initial nozzle portion 60. In some cases, the converging surfaces 70, 72 and / or the diverging surfaces 64, 66 are axisymmetric with respect to the axis 74. In an annular aerodynamic cone configuration, the thrust canisters are circumferentially spaced around the centerline 16 of the second-stage rocket 14. In the linear aerodynamic cone configuration, the thrust tanks are linearly spaced along a plane parallel to the centerline 16 of the second-stage rocket 14.

[0061] In some embodiments, the engine 12 is recessed into the base surface 38 of the second-stage rocket 14 to protect parts of the engine 12 from high-load environments, such as during reentry into the atmosphere.

[0062] refer to Figure 7 and Figure 8 The enhanced pneumatic cone nozzle 10, which is absent in existing pneumatic cone nozzles, captures the exhaust flow on its outer expansion surface 30 and deflects it in the axial direction, thereby generating additional thrust. This significantly increases the expansion area 40 of the nozzle 10 during vacuum operation (and thus the expansion ratio) without compromising the radial position 42 of the throat (see [link to relevant documentation]). Figure 5 This improves the performance of engine 12 without sacrificing the length of engine 12 or the diameter of high-pressure chamber 36. Traditionally, the expansion area 40 will be a function of the radial position 42 of the throat, and a further increase in the expansion area 40 will require an increase in the radial position 42 of the throat, resulting in a very small size of the throat 24 used to fix the thrust.

[0063] refer to Figure 5 and Figure 6In the illustrated embodiment, the outer expansion surface 30 is integrally connected to the second-stage rocket 14 via beams 39 and 41, which extend radially between the enhanced aerodynamic cone nozzle 10 and the sidewall 43 of the second-stage rocket 14. Beams 39 and 41 also support a thrust output structure 78, on which the engine 10 is mounted via a universal joint 80 and a plurality of struts 82. The nozzle 10 includes a seal 44 (e.g., a hot gas seal formed of a metal bellows) that allows the center body 28 to be mounted via the universal joint while allowing the outer expansion surface 30 to remain fixed relative to the second-stage rocket 14. The seal 44 extends between the front end of the outer expansion surface 30 and the outer rear end 68 of the initial nozzle portion 60. In other embodiments not shown in the figures, the seal 44 is positioned in another location (e.g., where the rear end of the outer expansion surface 30 is adjacent to the base surface 38 of the second-stage rocket 14) to allow the entire enhanced aerodynamic cone nozzle 10 (including the outer expansion surface) to be mounted with a universal joint relative to the sidewall 43 of the second-stage rocket 14.

[0064] During vacuum operation (see) Figure 5 (To the left of centerline 16), high-pressure gas exits high-pressure chamber 36 and expands along inner expansion surface 26 and outer expansion surface 30 to efficiently generate axial thrust. Low pressure in the region downstream of the central body base 34 allows for closed-wake operation of nozzle 10. Recompression wave 46 emanates from closed-wake region 48. The vacuum inner jet boundary 50 continues to expand beyond the edge of outer expansion surface 30. During atmospheric (e.g., sea level) operation (see...) Figure 5 (To the right of centerline 14), the hot gas leaves the high-pressure chamber 36 and expands along the inner expansion surface 26, but does not interact with the outer expansion surface 30. The gas jet boundaries 52 and 54 are determined by the pressure in the local atmosphere 56 and the pressure in the open wake 58 downstream of the base 34 of the central body.

[0065] Therefore, the engine 12 with the enhanced aerodynamic cone nozzle 10 offers numerous advantages over prior art nozzles, and does so with a significantly shorter shape factor than other prior art nozzles. The nozzle expansion area ratio is approximately doubled, improving nozzle vacuum efficiency and increasing engine specific impulse by 10 seconds or more, providing space performance comparable to industry-leading upper-stage engines. The recess of the nozzle 10 into the second-stage rocket 14 improves ground clearance and reduces localized heating effects. The remainder of the vehicle base 20 can be actively cooled using the thermal insulation system disclosed in commonly assigned U.S. Provisional Patent Application No. 62 / 942,886, filed December 3, 2019, the contents of which are incorporated herein by reference in their entirety. Thus, the vehicle base 20 can provide a robust barrier protecting the second-stage rocket 14 from surface ejecta generated during landing on an unprepared planetary surface. These features enable the second-stage rocket 14 to perform a base-first atmospheric reentry orbit with low-throttle final descent combustion and a soft vertical landing using a single propulsion engine. Compared to other proposed "nose-first" or "fuselage-first" (also known as Belly flop) strategies, this offers several key advantages: (i) it eliminates the need for multiple engines dedicated to space and atmospheric operations, reducing mass and number of parts while improving overall system performance; (ii) it eliminates the need for challenging in-atmosphere reorientation maneuvers required for nose-first reentry vehicles with vertical landing curves; (iii) it keeps the primary load path axially aligned throughout all phases of flight, allowing for more efficient structural solutions; (iv) the shared vertical orientation during ascent and reentry simplifies cryogenic fluid management challenges by minimizing sloshing and associated evaporation; and (v) it minimizes the overall thermal load managed by the vehicle during reentry by minimizing the heat shield surface area while maintaining a low ballistic coefficient.

[0066] Although several embodiments have been disclosed, it will be apparent to those skilled in the art that various aspects of the invention include numerous other embodiments. Therefore, the invention is not limited to any aspect other than those claimed in accordance with the appended claims and their equivalents. It will also be apparent to those skilled in the art that variations and modifications can be made without departing from the true scope of this disclosure. For example, in some cases, one or more features disclosed in connection with one embodiment may be used alone or in combination with one or more features of one or more other embodiments.

Claims

1. An enhanced pneumatic cone nozzle for an atmospheric reentry vehicle, comprising: The initial nozzle section includes a convergent section, a divergent section downstream of the convergent section, and a throat defining the transition between the convergent section and the divergent section. In the secondary nozzle section downstream of the initial nozzle section, the secondary nozzle section includes: A central body extending from the posterior part of the throat; The internally expanded surface defined by the central body; The outer expansion surface outside the inner expansion surface, the outer expansion surface extending downstream from the divergence section of the initial nozzle portion; and An expansion cavity defined between the inner expansion surface and the outer expansion surface; and The inflection point is defined as the point where the divergence region of the initial nozzle portion intersects with the outer expansion surface of the secondary nozzle portion.

2. The enhanced pneumatic cone nozzle according to claim 1, wherein, The size of the central body decreases continuously in the rearward direction.

3. The enhanced pneumatic cone nozzle according to claim 1, wherein, The inner expansion surface and the outer expansion surface are configured such that the expansion cavity has a width that increases continuously in the rearward direction.

4. The enhanced pneumatic cone nozzle according to claim 1, wherein, The outer expansion surface extends as far back as the inner expansion surface.

5. The enhanced pneumatic cone nozzle according to claim 1, wherein, The outer expansion surface extends further back than the inner expansion surface.

6. The enhanced pneumatic cone nozzle according to claim 1, wherein, The inner expansion surface extends further back than the outer expansion surface.

7. The enhanced pneumatic cone nozzle according to claim 1, wherein, The expansion cavity extends circumferentially around the central body and is concentrically aligned with the central body around the centerline of the enhanced pneumatic cone nozzle.

8. The enhanced pneumatic cone nozzle according to claim 1, wherein, The enhanced pneumatic cone nozzle is a linear pneumatic cone nozzle.

9. The enhanced pneumatic cone nozzle according to claim 1, wherein, The throat is included in the initial nozzle portion of the enhanced pneumatic cone nozzle; and The external expansion surface extends rearward from the outer rear end of the initial nozzle portion.

10. An engine for an atmospheric reentry vehicle, comprising: High-pressure chamber; An enhanced pneumatic conical nozzle, which discharges the gas generated by the high-pressure chamber, the enhanced pneumatic conical nozzle comprising: The initial nozzle section includes a convergent section, a divergent section downstream of the convergent section, and a throat defining the transition between the convergent section and the divergent section. In the secondary nozzle section downstream of the initial nozzle section, the secondary nozzle section includes: A central body extending from the posterior part of the throat; The internally expanded surface defined by the central body; The outer expansion surface outside the inner expansion surface, the outer expansion surface extending downstream from the divergence section of the initial nozzle portion; and An expansion cavity defined between the inner expansion surface and the outer expansion surface; and The inflection point is defined as the point where the divergence region of the initial nozzle portion intersects with the outer expansion surface of the secondary nozzle portion.

11. The engine according to claim 10, wherein, The size of the central body decreases continuously in the rearward direction.

12. The engine according to claim 10, wherein, The inner expansion surface and the outer expansion surface are configured such that the expansion cavity has a width that increases continuously in the rearward direction.

13. The engine according to claim 10, wherein, The outer expansion surface extends as far back as the inner expansion surface.

14. The engine according to claim 10, wherein, The outer expansion surface extends further back than the inner expansion surface.

15. The engine according to claim 10, wherein, The inner expansion surface extends further back than the outer expansion surface.

16. The engine according to claim 10, wherein, The expansion cavity extends circumferentially around the central body and is concentrically aligned with the central body around the centerline of the enhanced pneumatic cone nozzle.

17. The engine according to claim 10, wherein, The enhanced pneumatic cone nozzle is a linear pneumatic cone nozzle.

18. The engine according to claim 10, wherein, The throat is included in the initial nozzle portion of the enhanced pneumatic cone nozzle; and The external expansion surface extends rearward from the outer rear end of the initial nozzle portion.

19. A vehicle comprising: An engine comprising a high-pressure chamber and an enhanced pneumatic cone nozzle for discharging gases generated in the high-pressure chamber, the enhanced pneumatic cone nozzle comprising: The initial nozzle section includes a convergent section, a divergent section downstream of the convergent section, and a throat defining the transition between the convergent section and the divergent section. In the secondary nozzle section downstream of the initial nozzle section, the secondary nozzle section includes: A central body extending from the posterior part of the throat; The internally expanded surface defined by the central body; The outer expansion surface outside the inner expansion surface, the outer expansion surface extending downstream from the divergence section of the initial nozzle portion; and An expansion cavity defined between the inner expansion surface and the outer expansion surface; and The inflection point is defined as the point where the divergence region of the initial nozzle portion intersects with the outer expansion surface of the secondary nozzle portion.

20. The vehicle according to claim 19, wherein, The launch vehicle is an upper-stage rocket.

21. The vehicle according to claim 19, wherein, The central body is a truncated annular pneumatic cone with a central body base, the central body base partially defining the rear end of the vehicle.

22. The vehicle according to claim 19, wherein, The engine is recessed into the base surface of the vehicle.

23. The vehicle according to claim 19, wherein, The external expansion surface is integrally connected to the vehicle, and the enhanced pneumatic cone nozzle includes a seal that allows the center body to be mounted with a universal joint while allowing the external expansion surface to remain fixed relative to the vehicle.

24. The vehicle according to claim 19, further comprising a seal that allows the engine to be mounted relative to the vehicle via a universal joint.

25. The vehicle according to claim 19, wherein, The engine is configured for space propulsion and atmospheric landing propulsion.

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