CN117529435A - Non-axisymmetric heat shield, nozzle at least partially defined by heat shield, engine comprising nozzle, and vehicle comprising engine - Google Patents

Abstract

A heat shield for protecting the windward side of a vehicle from high enthalpy flow is disclosed. The heat shield includes a central body sidewall and a central body base extending rearward of the central body sidewall. The center body sidewall and the center body base define a non-axisymmetric heat shield outer surface. Also disclosed is a plug nozzle defined at least in part by the heat shield, an engine including a high pressure chamber and the plug nozzle, and a vehicle including the engine.

Description

Non-axisymmetric heat shield, nozzle at least partially defined by heat shield, engine comprising nozzle, and vehicle comprising engine

Cross Reference to Related Applications

The present application claims priority from U.S. provisional patent application No. 63/236,002 filed on 8 month 23 of 2021 and U.S. provisional patent application No. 63/174,323 filed on 4 month 13 of 2021, the contents of which are incorporated herein by reference in their entirety.

Technical Field

The present disclosure relates generally to aerodynamic shapes of vehicles traveling at or above hypersonic speeds, as well as heat shields, nozzles, and engines for such vehicles. The present disclosure more particularly relates to non-axisymmetric heat shields, nozzles at least partially defined by heat shields, engines including nozzles, and vehicles including engines.

Background

Due to the great cost-effective potential, reusability of similar aircraft to rockets has long been the "holy cup" of rocket technology. The ability to recover and reuse the upper stage rocket of a multi-stage rocket system (e.g., the second stage rocket of a two-stage rocket system) remains a significant technical gap that has not been addressed by the industry. The reuse of the upper stages of a multi-stage rocket is challenging due to the harsh reentry environment and performance penalty associated with the increased structural mass required to withstand the reentry environment and guide the vehicle to the precise landing location. The upper stage rockets are typically constructed with minimal structure and complexity, as any mass increase in the second stage is a 1:1 reduction in payload capacity. Thus, reusing the upper stage rocket requires significant additional functionality, but with minimal mass increase.

Rockets and other vehicles traveling at or above hypersonic speeds within the planetary atmosphere (e.g., space reentry vehicles, airplanes, missiles, etc.) require a means to protect themselves from the heating that occurs at such high speeds. Conventional solutions for mitigating such heating include the use of one or more of the following materials: (i) Ablative material that undergoes pyrolysis and generates gases that move downstream in the boundary layer to form a protective film layer; (ii) High temperature materials (e.g., ceramics, carbon-carbon, etc.); (iii) A composite material which insulates the base material and radiates heat therefrom; and (iv) divergent cooling, which involves the use of a thin protective film provided by a gas passing through the semi-porous wall. These conventional solutions for mitigating heating have adverse cost, operational, and quality effects on certain applications, such as reusable vehicles. It is therefore advantageous to minimize the area of the vehicle and the associated mass that must be protected by such a heat shield.

To reduce the operational cost and turnaround time of the reusable space refurbishment vehicle, it is advantageous to control the vehicle to land at a precise location configured to limit damage to the vehicle (e.g., a prepared concrete surface or landing zone) during a landing event.

Achieving a controlled landing requires the ability to maneuver during the return to the atmosphere and counteract track disturbances during flight. Very large jet engines (e.g., bell nozzle engines) traditionally used for upper stage rockets have limitations that prevent them from acting as a propulsion landing system for the upper stage rockets. In particular, large jet engines are typically optimized for efficiency only in vacuum and therefore experience relatively poor performance during atmospheric operation (i.e., during reentry and landing). Furthermore, large jet engines are difficult to protect during reversion because they are very thin and create severe flow separation and side loads in the atmosphere. Adding a secondary propulsion system to the upper stage rocket to achieve a controlled landing is not feasible due to adverse cost and quality effects.

Recent efforts by the applicant to overcome these and other problems have focused on the use of plug-nozzle engines (gas-tipped engines, aerospike nozzle engine). The plug nozzle engine minimizes nozzle efficiency losses due to pressure drag, which allows it to operate at low throttle levels in the atmosphere, while flow separation will occur in large nozzle engines, resulting in unstable thrust oscillations, unstable thrust vectors, and engine or vehicle damage. Referring to FIG. 1, a prior art plug engine 114 includes at least one high pressure chamber 150 (e.g., combustion chamber) and a plug nozzle 112. Referring to fig. 2, the prior art plug nozzle 112 includes at least an initial nozzle portion 152 and a secondary nozzle portion 153, with exhaust initially exiting the high pressure chamber 150 through the initial nozzle portion 152, the secondary nozzle portion 153 being downstream relative to the initial nozzle portion 152. The initial nozzle portion 152 includes at least one throat 154 that extends annularly about an axis 157 of the initial nozzle portion 152. The initial nozzle portion 152 is typically in the form of a convergent-divergent nozzle (convergent-divergent nozzle). The secondary nozzle portion 153 includes a central body 140 (e.g., a tip) defining an inner expansion surface 155 (see fig. 1). The prior art plug engine 114 and its improvements are discussed in more detail in commonly assigned U.S. provisional patent application No. 63/236,002 filed on 8/23, U.S. provisional patent application No. 62/941,386 filed on 11/27, and international patent application No. PCT/US2020/048178, filed on 8/27, 2020, and claiming priority from U.S. provisional patent application No. 62/941,386, which are incorporated herein by reference in their entirety.

In addition to mobility, the vehicle must also have sufficient aerodynamic lift capability to slow down and achieve a controlled landing during re-entry into the atmosphere. Prior art returnable vehicles that achieve accurate landing are typically lifting bodies such as space shuttles. These vehicles achieve large lift-to-drag ratios and powerful maneuver capability, but at the cost of large heat shield area and several actively controlled aerodynamic surfaces on the underside of the winged vehicle. Other prior art returnable vehicles minimize the additional mass of the heat shield by exposing only a relatively small base area of the vehicle to the returnable environment. These returnable vehicles produce lift-drag ratios sufficient to slow down and achieve some degree of controlled landing during the returnable atmosphere, but lack propulsion systems or other motorized flight means, and thus cannot land at precise locations.

One such prior art vehicle is the returnable vehicle 216 of an Apollo spacecraft, which is schematically illustrated in FIGS. 3 and 4. This prior art vehicle 216 is in the form of a capsule that extends along a linear centerline 230 between its forward end 220 and an opposite rearward end 222. The aft end 222 defines a windward side of the vehicle 216 during re-entry into the atmosphere. The prior art vehicle 216 includes a heat shield 240 and an annular sidewall 236, the heat shield 240 defining a heat shield outer surface on the windward side, the annular sidewall 236 being disposed at an angle θ (hereinafter, "sidewall angle θ") of thirty-three degrees (33 °) relative to planes 238, 239 parallel to the centerline 230. The heat shield surface 240 and the vehicle 216 as a whole are at least substantially axisymmetric with respect to the centerline 230. Referring to fig. 3, the prior art vehicle 216 will initially re-enter the atmosphere at a so-called zero angle of attack, wherein the vehicle 216 is oriented such that the centerline 230 is parallel to the direction of travel 260. In the zero angle of attack orientation, the center of gravity 262 and center of pressure 264 of the vehicle 216 are in a plane 266 offset relative to the direction of travel 260.

During flight, aerodynamic lift and drag on the vehicle 216 will generate pitching moments about the center of gravity 262, and the vehicle 216 will naturally adopt an orientation in which those moments are balanced, which is referred to as an aerodynamic setpoint. In this orientation shown in fig. 4, the center of gravity 262 and center of pressure 264 of the vehicle 216 will be in a plane 266 parallel to the direction of travel 260. In this orientation, the opposite sides of the vehicle 216 will be at different respective angles relative to the planes 270, 271 parallel to the direction of travel 260And (5) setting. The center of gravity 262 and center of pressure 264 of the prior art vehicle 216 will be selected to achieve a particular non-zero angle of attack during re-entry to the atmosphere. This is because increasing the angle of attack increases the lift-to-drag ratio of the vehicle 216. To achieve a sufficiently high lift-to-drag ratio while also avoiding side wall 236 to follow and travel relative to carrier 216The potentially catastrophic exposure of the high enthalpy stream 268 moving in the opposite direction to direction 260, prior art vehicle 216 must be designed with a relatively steep sidewall angle θ (i.e., sidewall angle θ has a relatively high magnitude).

The magnitude of the sidewall angle θ is inversely proportional to the volume of the vehicle 216, and thus for some applications, designs with steep sidewall angles θ may not be desirable. For example, if the purpose of the vehicle 216 is to transport cargo, a steeper sidewall angle θ means less volume for storing cargo.

Aspects of the present invention are directed to these and other problems.

Disclosure of Invention

According to one aspect of the invention, a heat shield for protecting a windward side of a vehicle from high enthalpy flow includes a central body sidewall and a central body base extending rearward of the central body sidewall. The central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

According to another aspect of the invention, a plug nozzle includes a throat and a center body extending rearward of the throat. The center body includes a center body sidewall defining an expansion surface, and a center body base extending rearward of the center body sidewall. The central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

According to another aspect of the invention, an engine includes a high pressure chamber and a plug nozzle that discharges gas generated by the high pressure chamber. The plug nozzle includes a throat and a central body extending rearward of the throat. The center body includes a center body sidewall defining an expansion surface, and a center body base extending rearward of the center body sidewall. The central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

According to another aspect of the invention, a vehicle includes an engine including a high pressure chamber, and a plug nozzle that discharges gas generated by the high pressure chamber. The plug nozzle includes a throat and a central body extending rearward of the throat. The center body includes a center body sidewall defining an expansion surface, and a center body base extending rearward of the center body sidewall. The central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

According to another aspect of the invention, a reusable upper stage rocket of a multi-stage rocket system includes a reentrant heat shield surface on a base of the upper stage rocket. The reentrant heat shield surface has a non-axisymmetric shape that produces lift at zero angle of attack.

Other aspects of the invention may include one or more of the following features, alone or in combination, in addition to or as an alternative to one or more of the features described above:

-the central body sidewall and the central body base together form a bluff body;

-the central body side wall comprises a rigid wall having a conical shape;

-said central body side wall has a truncated and oblique conical shape;

-the central body base has at least one of a hemispherical shape, a frustoconical shape, a multi-conical shape and an elliptical shape;

-at least one of the central body side wall and the central body base is actively cooled;

-the central body is a truncated annular plug;

-the vehicle is an upper stage rocket;

-the vehicle is a re-atmosphere vehicle;

-the central body is a truncated annular plug and the central body base partially defines the rear end of the vehicle;

-the vehicle comprises a body portion defining a front end of the vehicle and a base portion defining a rear end of the vehicle, and the body portion is at least substantially axisymmetric with respect to a body centerline extending in a direction between the front end of the body portion and the rear end of the body portion;

-the heat shield outer surface is non-axisymmetric with respect to the body centerline;

-the heat shield outer surface is configured such that the net aerodynamic forces acting on the central body during re-atmosphere are at an angle relative to the main body centerline;

-the heat shield outer surface is configured such that net aerodynamic forces acting on the central body generate lift during return to atmosphere at zero angle of attack;

-the engine and the plug nozzle are configured such that the plug nozzle discharges the gas generated by the high pressure chamber in a direction towards the rear end of the vehicle; and

-the central body side wall and the central body base are parts of the heat shield.

These and other aspects of the invention will be apparent from the drawings and detailed description provided hereinafter.

Drawings

Fig. 1 schematically illustrates a prior art plug engine and nozzle.

Fig. 2 schematically illustrates a portion of the prior art plug engine and nozzle of fig. 1.

Fig. 3 schematically illustrates a prior art vehicle (i.e., a returnable vehicle for an apollo spacecraft) with an axisymmetric heat shield in a zero angle of attack orientation.

Fig. 4 schematically illustrates the prior art vehicle of fig. 3 in a non-zero angle of attack orientation.

Figure 5 is an elevation view of a two-stage rocket system including an upper stage rocket with the present non-axisymmetric heat shield.

Fig. 6 is an exploded elevation view of the two-stage rocket system of fig. 5.

Fig. 7 is a perspective view of the upper stage rocket of fig. 5.

FIG. 8 is an elevation view of the upper stage rocket of FIG. 5 in a zero angle of attack orientation.

FIG. 9 is an elevation view of the upper stage rocket of FIG. 5 in a non-zero angle of attack orientation.

Fig. 10 is an elevation view of the trailing end of the upper stage rocket of fig. 5.

Fig. 11 is a plan view of the trailing end of the upper stage rocket of fig. 5.

Detailed Description

Referring to fig. 6-9, the present disclosure describes a non-axisymmetric heat shield 10, a nozzle 12 defined by at least a portion of the heat shield 10, an engine 14 including the nozzle 12, and a vehicle 16 including the engine 14.

The vehicle 16 is a rocket (e.g., a multi-stage rocket, a single-stage orbital (SSTO) rocket, an upper-stage rocket, a booster rocket, etc.), a missile, a spacecraft, an aircraft, or another vehicle designed for traveling (e.g., flying) up to at least supersonic (e.g., supersonic, hypersonic, reentry speed, etc.) in an atmospheric, sub-orbital, extraterrestrial, and/or outer space environment. Referring to FIG. 5, in the illustrated embodiment, the vehicle 16 is a reusable second stage rocket of the two-stage rocket system 18. Referring to fig. 6 and 7, the vehicle 16 extends between a front end 20 and an opposite rear end 22. The vehicle 16 includes a payload housing 24 proximate the front end 20 and an engine 14 proximate the rear end 22. The rear end 22 defines, for example, a windward side of the vehicle 16 during re-entry into the atmosphere.

Referring to fig. 8 and 9, the vehicle 16 includes a body portion 26 defining the front end 20 of the vehicle 16 and a base portion 28 defining the rear end 22 of the vehicle 16. The body portion 26 is shaped such that its outer surface is at least substantially axisymmetric with respect to a body centerline 30 (e.g., a linear centerline perpendicular to a tangent of a forward-most point of the body portion 26) extending in a direction between a forward end of the body portion 26 (i.e., the forward end 20 of the vehicle 16) and a rearward end of the body portion 26. The base portion 28 includes a heat shield 10 defining a heat shield outer surface, for example on the windward side of the vehicle 16 during re-entry into the atmosphere. The heat shield 10 is configured such that the heat shield outer surface is non-axisymmetric with respect to the body centerline 30 and is non-axisymmetric with respect to a heat shield centerline 32 (e.g., a linear centerline perpendicular to a tangent of a rearmost point of the heat shield 10) extending in a direction between a front end of the heat shield 10 and a rear end of the heat shield 10 (e.g., the rear end 22 of the vehicle 16). Accordingly, the body portion 26 of the vehicle 16 and the heat shield 10 are configured such that the heat shield centerline 32 is offset by an angle β relative to the body centerline 30. The angle β is typically in the range of 1 ° to 10 °. In the illustrated embodiment, the angle β is 4 °. In other embodiments, the angle β is, for example, about 1 °, 2 °,3 °, 5 °, 6 °, 7 °,8 °, 9 °, or 10 °. In some embodiments, including the illustrated embodiments, at least a portion of the outer surface of the heat shield is at least substantially axisymmetric with respect to the heat shield centerline 32, as will be discussed in more detail below.

Still referring to fig. 8 and 9, the body portion 26 of the vehicle 16 includes a nose 34 and a sidewall 36 extending rearward of the nose 34. In the illustrated embodiment, the nose 34 includes a rigid wall having a rounded conical shape, and the side wall 36 includes a rigid wall having a frustoconical shape. The side walls 36 at least partially define the payload housing 24, with payloads (e.g., cargo, munitions, etc.) stored in the payload housing 24 during transport by the vehicle 16. The side wall 36 further surrounds one or more interior components of the vehicle 16, such as one or more components of the engine 14 and/or one or more components of a system for actively cooling the heat shield 10 (e.g., a tank, pump, turbine, etc.). The side walls 36 are disposed at an angle θ (hereinafter, "side wall angle θ") with respect to planes 38, 39 parallel to the body centerline 30. In the illustrated embodiment, the vehicle 16 is designed to have a relatively shallow sidewall angle θ (i.e., sidewall angle θ has a low high magnitude (low magnitude)) as compared to the prior art vehicle 216 of fig. 3 and 4. The sidewall angle θ is in the range of 0 ° to 90 °. In some embodiments, the sidewall angle θ is in the range of 5 ° to 15 °. In the illustrated embodiment, for example, the sidewall angle θ is 7 °. The magnitude of the sidewall angle θ is inversely proportional to the volume of the vehicle 16, and thus the shallow sidewall angle θ advantageously allows the vehicle 16, and in particular the payload housing 24, to have a volume that is greater than the volume of the prior art vehicle 216.

Referring to fig. 8-10, the base portion 28 of the vehicle 16 includes one or more components defining the heat shield 10 and its outer surface (i.e., heat shield outer surface). In the illustrated embodiment, the base portion 28 includes a central body 40 and a propeller mount 42, each defining portions of the heat shield 10 and the heat shield exterior surface. The central body 40 is in the form of a truncated annular plug. The center body 40 includes a center body sidewall 44 and a center body base 46 that together form a bluff body. The central body sidewall 44 comprises a rigid wall having a truncated and beveled conical shape. The central body base 46 includes a rigid wall having a hemispherical shape. In other embodiments, the central body base 46 additionally or alternatively includes one or more rigid walls having a frustoconical shape, a multi-conical shape (e.g., a double cone, a triple cone, etc.), an elliptical shape, and/or another blunt shape. Referring to fig. 10 and 11, the propeller mount 42 includes a rigid wall extending annularly about the body centerline 30 and is positioned proximate the rear end of the body portion 26 of the vehicle 16. The propeller mount 42 includes circumferentially spaced openings extending therethrough in a direction parallel to the body centerline 30. Each opening in the propeller mount 42 is configured to receive a "thrust cylinder" 48 of the engine 14, as will be described in greater detail below.

The heat shield outer surface defined by the respective outer surfaces of the center body sidewall 44, center body base 46, and propeller mount 42 is non-axisymmetric with respect to the main body centerline 30. In some embodiments, at least a portion of the outer surface of the heat shield is at least substantially axisymmetric with respect to the heat shield centerline 32. In the illustrated embodiment, for example, the outer surface defined by the center body base 46 has a hemispherical shape and is axisymmetric with respect to the heat shield centerline 32.

In some embodiments, one or more components of heat shield 10 (including center body sidewall 44, center body base 46, and/or propeller mount 42) are actively cooled using an insulation system disclosed in commonly assigned U.S. provisional patent application No. 62/942,886 filed on 3 of 12 in 2019 and international patent application No. PCT/US2020/48226 filed on 27 of 8 in 2020 and claiming priority from U.S. provisional patent application No. 62/942,886, which are incorporated herein by reference in their entirety. In some embodiments, at least a portion of the side wall 36 of the body portion 26 of the vehicle 16 is actively cooled in the same or similar manner.

Referring to FIG. 10, engine 14 includes a nozzle 12 and at least one high pressure chamber 50 (e.g., combustion chamber).

The high pressure chamber 50 generates gas that is exhausted through the nozzle 12. High pressure chamber 50 is in the form of an annular ring, a segmented ring, a separate thrust chamber, or any other configuration that provides supersonic flow to nozzle 12.

The nozzle 12 is a plug nozzle having at least one primary nozzle portion 52 and a secondary nozzle portion, the exhaust initially exiting the at least one high pressure chamber 50 through the primary nozzle portion 52, the secondary nozzle portion 53 being downstream relative to the primary nozzle portion 52. The initial nozzle portion 52 includes at least one throat 54 and is typically in the form of a convergent-divergent nozzle.

Still referring to fig. 10, the nozzle 12 is defined by at least a portion of the heat shield 10. In the illustrated embodiment, the secondary nozzle portion of the nozzle 12 is defined by a central body 40. The central body sidewall 44 serves as an expansion surface for the nozzle 12 in addition to its function as part of the heat shield 10. The central body sidewall 44 is non-axisymmetric with respect to the heat shield centerline 32 and, thus, the nozzle 12 is non-axisymmetric with respect to the heat shield centerline 32. As shown in fig. 10, the initial nozzle portion 52 and the center body base 46 are spaced apart on opposite sides of the vehicle 16 by respective first and second distances d ₁ 、d ₂ . Due to the non-axisymmetric shape of the nozzle 12, the first and second distances d ₁ 、d ₂ Different from each other. This is in contrast to the prior art plug nozzle 112 shown in fig. 1, in which the initial nozzle portion 52 and the center body base 46 are spaced apart the same distance d on opposite sides of the vehicle 16 in the prior art plug nozzle 112 ₁ 。

The engine 14 and the nozzle 12 may be configured in a variety of different ways. In the illustrated embodiment, the engine 14 has a so-called "plug cluster" configuration. That is, the engine 14 includes a plurality of discrete high pressure chambers 50 spaced apart relative to one another and a plurality of discrete initial nozzle portions 52 spaced apart relative to one another. Each initial nozzle portion 52 is disposed relative to the corresponding high pressure chamber 50 and is configured to discharge gas exiting the respective high pressure chamber 50. Each pair of high pressure chamber 50 and initial nozzle portion 52 is referred to in the art as a "thrust barrel 48". The initial nozzle portion 52 of each thrust barrel 48 includes a discrete throat 54. Referring to fig. 11, the thrust cylinders 48 are circumferentially spaced relative to the body centerline 30. In other embodiments, the engine 14 may include a single high pressure chamber 50 extending annularly about the body centerline 30, and a single initial nozzle portion 52 having a single throat 54 extending annularly about the body centerline 30.

Referring to fig. 10, in the illustrated embodiment, each thrust barrel 48 is configured such that the throat 54 extends annularly about the axis 57 of the initial nozzle portion 52, and such that the axis 57 is parallel to the body centerline 30. This is in contrast to the prior art plug nozzle 112 of fig. 1 and 2, for example, in the prior art plug nozzle 112, the axis 157 is angled (i.e., not parallel) with respect to the centerline 116 of the vehicle on which the nozzle 112 is disposed. In other embodiments of the present engine 14 and nozzle 12, each thrust barrel 48 is configured such that the axis 57 of the initial nozzle portion 52 is angled relative to the body centerline 30.

During operation, the vehicle 16 moves through the environment (e.g., atmosphere, space) at a free stream Mach number that may approach Mach thirty (30). During operation under vacuum conditions, the exhaust wakes from each thrust barrel 48 of the engine 14 combine to form an aerodynamic spike that captures positive pressure along the central body base 46 of the heat shield 10. This creates additional thrust and increases the overall efficiency of the engine 14 and the vehicle 16. Referring to fig. 10, during atmospheric flight, a bow shock 56 is formed upstream of the vehicle 16, and the temperature on the vehicle side of the bow shock 56 may reach thousands of degrees kelvin. The bow shock 56 creates significant drag to reduce the speed of the vehicle 16 and also creates significant aerodynamic heating 58 on the heat shield 10, requiring cooling and/or other thermal protection to achieve reusability, such as the active cooling systems described above.

Referring again to fig. 8, the vehicle 16 may initially re-enter the atmosphere at a so-called zero angle of attack (i.e., α=0°), with the vehicle 16 oriented such that the body centerline 30 is parallel to the direction of travel 60. In this orientation, the heat shield centerline 32 is offset from the direction of travel 60 by an angle δ equal to the angle β by which the heat shield centerline 32 is offset from the body centerline 30. In the zero angle of attack orientation, the center of gravity 62 and the center of pressure 64 of the vehicle 16 are in a plane 66 that is offset relative to the direction of travel 60. The fact that the central body base 46 of the heat shield 10 is axisymmetric about the heat shield centerline 32 offset at an angle β relative to the main body centerline 30 advantageously induces a net lift on the vehicle 16 relative to the direction of travel 60, even at zero angle of attack.

During operation of the vehicle 16 at zero angle of attack (fig. 8), aerodynamic lift and drag on the vehicle 16 will generate pitching moments about the center of gravity 62, and the vehicle 16 will naturally adopt an orientation (i.e., aerodynamic setpoint) in which those moments are balanced. This orientation, shown in fig. 9, increases the angle α between the center body base 46 and the high enthalpy flow 68 moving in a direction opposite the travel direction 60 relative to the vehicle 16. Thus, the non-zero angle of attack orientation (FIG. 9) produces additional lift than the zero angle of attack orientation (FIG. 8). At a non-zero angle of attack (fig. 9), the center of gravity 62 and the plane 66 of the center of pressure 64 will be parallel with respect to the direction of travel 60, and opposite sides of the vehicle 16 will be at different respective angles with respect to the planes 70, 71 parallel with the direction of travel 60The heat shield centerline 32 is offset from the direction of travel 60 by an angle δ equal to the sum of: (i) The angle α between the center body base 46 and the high enthalpy flow 68; and (ii) an angle β at which the heat shield centerline 32 is offset relative to the body centerline 30. The angle of attack alpha should not exceed the sidewall angle theta. Thus, in the illustrated embodiment, the vehicle 16 should not fly at an angle of attack α exceeding 7 °. Maintaining the angle of attack α below this threshold prevents the high enthalpy stream 68 from striking the sides of the vehicle 16The wall 36, thereby eliminating the need for additional insulation (and the accompanying additional mass) on those surfaces of the side wall 36. The center of gravity 62 and center of pressure 64 of the vehicle 16 may be selected to achieve a particular non-zero angle of attack during re-entry to the atmosphere.

The non-axisymmetric nature of the heat shield 10 (e.g., the tilt angle β of the central body base 46 relative to the main body centerline 30) allows the vehicle 16 to achieve a higher lift-to-drag ratio within certain angle of attack limits. That is, the vehicle 16 may achieve a certain target lift-to-drag ratio with a lower range of angles of attack α. This allows for a shallower sidewall angle θ while still preventing hypersonic flow 68 from striking sidewall 36 of vehicle 16. This in turn allows the increased volume to be used for other system purposes (e.g., propellants, payloads, etc.).

To minimize the additional mass of the heat shield 10 and aerodynamic controls, the vehicle 16 exposes only the relatively small heat shield 10 of the vehicle 16 to the high enthalpy flow 68 while also producing sufficient lift-to-drag ratio to achieve accurate maneuver and landing. By adjusting the angle β of the center body base 46 relative to the body centerline 30 and the position of the center of gravity 62, the design of the vehicle 16 can be adjusted to produce different amounts of lift while maintaining the same adjusted angle of attack α. This increases the freedom of design space that is not available with conventional axisymmetric vehicle shapes. The combined surface of heat shield 10 and nozzle 12 is advantageous because it results in lower mass loss for heat shield 10 in the reusable upper level applications.

While several embodiments have been disclosed, it will be apparent to those of ordinary skill in the art that aspects of the invention include more embodiments. Accordingly, aspects of the invention are not limited except as by the appended claims and their equivalents. It will also be apparent to those of ordinary skill in the art that variations and modifications can be made without departing from the true scope of the 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 (20)

1. A heat shield for protecting a windward side of a vehicle from high enthalpy flow, comprising:

a central body sidewall; and

a center body base extending rearward of the center body sidewall;

wherein the central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

2. The heat shield of claim 1, wherein the central body sidewall and the central body base together form a bluff body.

3. The heat shield of claim 1, wherein the central body sidewall comprises a rigid wall having a conical shape.

4. The heat shield of claim 1, wherein the central body sidewall has a truncated and beveled conical shape.

5. The heat shield of claim 1, wherein the central body base has at least one of a hemispherical shape, a frustoconical shape, a multi-conical shape, and an elliptical shape.

6. The heat shield of claim 1, wherein at least one of the central body sidewall and the central body base is actively cooled.

7. A plug nozzle, comprising:

a throat; and

a central body extending rearward of the throat, the central body comprising:

a central body sidewall defining an expansion surface; and

a center body base extending rearward of the center body sidewall;

wherein the central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

8. The plug nozzle of claim 7, wherein the center body is a truncated annular plug.

9. An engine, comprising:

a high pressure chamber;

a plug nozzle that discharges gas generated by the high pressure chamber, the plug nozzle comprising:

a throat; and

a central body extending rearward of the throat, the central body comprising:

a central body sidewall defining an expansion surface; and

a center body base extending rearward of the center body sidewall;

wherein the central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

10. A vehicle, comprising:

an engine including a high pressure chamber; and

a plug nozzle that discharges gas generated by the high pressure chamber, the plug nozzle comprising:

a throat; and

a central body extending rearward of the throat, the central body comprising:

a central body sidewall defining an expansion surface; and

a center body base extending rearward of the center body sidewall;

wherein the central body sidewall and the central body base define a non-axisymmetric heat shield outer surface.

11. The vehicle of claim 10, wherein the vehicle is an upper stage rocket.

12. The vehicle of claim 10, wherein the vehicle is a re-atmosphere vehicle.

13. The vehicle of claim 10, wherein the central body is a truncated annular plug and the central body base partially defines a rear end of the vehicle.

14. The vehicle of claim 10, wherein the vehicle comprises a body portion defining a front end of the vehicle and a base portion defining a rear end of the vehicle; and

wherein the body portion is at least substantially axisymmetric with respect to a body centerline extending in a direction between a front end of the body portion and a rear end of the body portion.

15. The vehicle of claim 14, wherein the heat shield outer surface is non-axisymmetric with respect to the body centerline.

16. The vehicle of claim 14, wherein the heat shield outer surface is configured such that net aerodynamic forces acting on the center body during re-entry into the atmosphere are at an angle relative to the main body centerline.

17. The vehicle of claim 10, wherein the heat shield outer surface is configured such that a net aerodynamic force acting on the center body during re-entry to the atmosphere at zero angle of attack generates lift.

18. The vehicle of claim 10, wherein the engine and the plug nozzle are configured such that the plug nozzle discharges gas generated by the high pressure chamber in a direction toward the rear end of the vehicle.

19. The vehicle of claim 10, further comprising a heat shield for protecting the rear end of the vehicle from high enthalpy flow;

wherein the central body sidewall and the central body base are components of the heat shield.

20. A reusable upper stage rocket of a multistage rocket system, the upper stage rocket comprising a reentrant heat shield surface having a non-axisymmetric shape on a vehicle base, the reentrant heat shield surface generating lift at zero angle of attack.