Actively-cooled heat shield system and vehicle including the same

Abstract

To provide means for rockets and other vehicles that travel at or above hypersonic speeds (e.g., space re-entry vehicles, aircraft, missiles, etc.) to protect themselves from the heating that occurs at such high speeds.SOLUTION: An actively-cooled heat shield system includes a heat shield, a tank, a pump, a heat exchanger, and a turbine. The heat shield defines a windward side of a vehicle. The tank stores a coolant. The pump receives the coolant from the tank and outputs a pressurized coolant. The heat exchanger is integrally connected with the heat shield. The heat exchanger receives the pressurized coolant from the pump, transfers heat from the heat shield to the pressurized coolant to generate a heated fluid, and outputs the heated fluid. An inlet receives the heated fluid output from the heat exchanger. The shaft is coupled to the pump and includes turbine blades. The shaft rotates and powers the pump when the heated fluid received from the heat exchanger acts on the turbine blades.SELECTED DRAWING: Figure 2

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to 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. [Technical field]

[0002] The present disclosure relates generally to cooling systems for vehicles exposed to high levels of heating, and more specifically to actively cooled heat shield systems for use in rockets and other vehicles traveling at or above hypersonic speeds, such as space re-entry vehicles, aircraft, and missiles. [Background technology]

[0003] Aircraft reusability for rockets has long been the "holy grail" of rocket research due to the enormous cost-benefit potential. The ability to recover and reuse the upper stage of a multi-stage rocket system (e.g., the second stage of a two-stage rocket system) remains a significant technology gap yet to be addressed by the industry. Reusing the upper stage of a multi-stage rocket is challenging due to the harsh re-entry environment and the performance penalties associated with the increased structural mass required for robust reuse. Upper stages are typically built with minimal structure and complexity, since adding mass to the second stage results in a 1:1 reduction in payload capacity. Thus, reusing an upper stage requires minimal mass loading as well as significant additional functionality.

[0004] Rockets and other vehicles traveling at or above hypersonic speeds (e.g., space re-entry vehicles, aircraft, missiles, etc.) require means to protect themselves from the heating that occurs at such high speeds. Conventional solutions to mitigate such heating include the use of one or more of the following: (i) ablative materials, which undergo thermal decomposition to produce gases that travel downstream through the boundary layer to form a protective membrane layer; (ii) high temperature materials (e.g., ceramics, carbon-carbon, etc.); (iii) composite materials, which insulate the base material and radiate heat therefrom; and (iv) transpiration cooling, which involves the use of a thin protective film provided by gas passing through a semi-porous wall. Summary of the Invention [Problem to be solved by the invention]

[0005] Existing thermal management solutions have cost, operational, and / or mass impacts that may not be conveniently compatible with certain applications, such as reusable vehicles. For example, ablative materials and brittle ceramics are incompatible with highly reusable systems. Transpiration cooling of heat shields is costly and difficult to control. What is needed is a cooling system that is highly robust, highly controllable, and well suited for long-term reusability.

[0006] Aspects of the present invention are directed to these and other problems. [Means for solving the problem]

[0007] According to one aspect of the invention, an actively cooled thermal shield system includes a thermal shield, a tank, a pump, a heat exchanger, and a turbine. The thermal shield defines a windward side of the vehicle. The tank is mounted to the vehicle and configured to store a coolant. The pump is mounted to the vehicle and configured to receive the coolant from the tank and output the pressurized coolant. The heat exchanger is mounted to the vehicle and integrally connected to the thermal shield. The heat exchanger is configured to receive the pressurized coolant from the pump, transfer heat from the thermal shield to the pressurized coolant to generate a heated fluid, and output the heated fluid. The turbine is mounted to the vehicle and includes an inlet, a shaft, and an outlet. The inlet is configured to receive the heated fluid output from the heat exchanger. The shaft is coupled to the pump and includes turbine blades mounted thereon. The shaft is configured to rotate when heated fluid received from the heat exchanger acts on the turbine blades, thereby providing power to the pump. The outlet is configured to output the heated fluid.

[0008] According to another aspect of the invention, the vehicle includes an actively cooled thermal shield system. The thermal shield system includes a thermal shield, a tank, a pump, a heat exchanger, and a turbine. The thermal shield defines a windward side of the vehicle. The tank is mounted to the vehicle and configured to store a coolant. The pump is mounted to the vehicle and configured to receive the coolant from the tank and output the pressurized coolant. The heat exchanger is mounted to the vehicle and integrally connected to the thermal shield. The heat exchanger is configured to receive the pressurized coolant from the pump, transfer heat from the thermal shield to the pressurized coolant to generate a heated fluid, and output the heated fluid. The turbine is mounted to the vehicle and includes an inlet, a shaft, and an outlet. The inlet is configured to receive the heated fluid output from the heat exchanger. The shaft is coupled to the pump and includes turbine blades mounted thereon. The shaft is configured to rotate when heated fluid received from the heat exchanger acts on the turbine blades, thereby providing power to the pump. The outlet is configured to output the heated fluid.

[0009] In accordance with another aspect of the invention, a reusable upper stage of a multi-stage rocket system includes an actively cooled heat shield system that converts heat from a high Mach number flow environment into energy to drive a liquid coolant pump.

[0010] According to another aspect of the invention, a method for actively cooling an upwind side of an upper stage of a multi-stage rocket system during atmospheric re-entry includes the steps of commencing operation of a pump mounted on the upper stage to commence output of pressurized coolant from the pump; flowing the pressurized coolant output by the pump through a heat exchanger integrally connected to a heat shield defining at least a portion of the upwind side of the upper stage; transferring heat from the heat shield to the pressurized coolant to produce a heated fluid; inputting the heated fluid into a turbine mounted on the upper stage, the turbine including a shaft coupled to the pump and turbine blades attached to the shaft; and exposing the turbine blades to the heated fluid to drive the shaft, thereby continuing to drive the pump.

[0011] In addition to, or as an alternative to, one or more of the features discussed above, further aspects of the invention can include one or more of the following features, either individually or in combination. At least the heat exchanger, turbine, and pump are configured such that when operation of the pump is commenced, the amount of energy provided by the heat exchanger to the turbine is sufficient to continue operation of the pump alone. The heat shield system is configured such that, once operation is initiated, the amount of energy transferred by the heat exchanger to the coolant is at least sufficient to sustain operation. The heat shield, tank, pump, heat exchanger, and turbine are configured such that the amount of energy transferred to the coolant by the heat exchanger is at least sufficient to sustain operation of the heat shield system. The heat shield, tank, pump, heat exchanger, and turbine are configured such that the amount of energy transferred to the coolant by the heat exchanger is at least sufficient to provide the turbine with the amount of power required to drive the pump. The coolant is at least one of an active coolant, a liquid coolant, and a cryogenic coolant. The heating fluid is at least one of a gas and a supercritical fluid. The thermal shield system further includes a primary heating fluid conduit configured to transport the heating fluid from the heat exchanger to an inlet of the turbine, and a bypass conduit configured to bypass excess energy in the heating fluid from at least a portion of the primary heating fluid conduit for power use by the auxiliary system. The pressure of the coolant in the tank alone provides enough energy to start the turbine and pump turning, resulting in an increase in pressure and power available to the turbine. The heat exchanger and heat shield are configured such that a flow of coolant through the heat exchanger maintains an acceptable temperature on the heat shield during re-entry of the vehicle into the planet's atmosphere. The heat shield is configured to be exposed to a high Mach number flow environment during normal operation. The vehicle is the upper stage of a multi-stage rocket system. An upper stage includes a thruster disposed at its aft end, the aft end defining an upwind side of the upper stage during operation of the heat shield system. The heat shield system and the propulsion engine share a multi-purpose component, the multi-purpose component being at least one of a heat shield, a tank, a pump, a heat exchanger, and a turbine. The heat shield system pump is the propulsion engine fuel pump. The vehicle further includes an exhaust conduit, and at least a portion of the heated fluid output from the turbine exits the upper stage rocket through the exhaust conduit. The transmitting and inputting steps of the method provide an amount of energy to the turbine that is alone sufficient to continue to drive the pump.

[0012] These and other aspects of the present invention will become evident in light of the drawings and detailed description provided below. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a vehicle including the present heat shield system.

[0014] [Diagram 2] FIG. 2 is a schematic cross-sectional view of the aft end portion of the vehicle of FIG. 1 showing components of a heat shield system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 1 and 2, the present disclosure describes an actively cooled heat shield system 10 and a vehicle 12 including same. The heat shield system 10 converts heat from a high Mach number flow environment 14 into energy to drive a liquid coolant pump 16 (see FIG. 2).

[0016] With reference to FIG. 1 , vehicle 12 may be 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 other vehicle designed for travel (e.g., flight) up to at least supersonic speeds (e.g., supersonic, hypersonic, re-entry speeds, etc.) in atmospheric, suborbital, orbital, extraterrestrial, and / or interplanetary environments.

[0017] In the illustrated embodiment, the vehicle 12 is a second stage of a two-stage rocket system (not shown). The vehicle 12 (hereinafter, "second stage 12") extends along a centerline 24 between a forward end 26 and an opposite aft end 28. The second stage 12 includes a payload 30 toward the forward end 26 and an engine 32 toward the aft end 28. The aft end 28 defines the windward side 22 of the second stage 12. In the illustrated embodiment, the engine 32 is an augmented aerospike nozzle engine as disclosed in U.S. Provisional Patent Application No. 62 / 941,383, filed November 27, 2019, by the same inventors, the contents of which are incorporated herein by reference in their entirety in any international patent application claiming priority to U.S. Provisional Patent Application No. 62 / 941,383. In other embodiments, the engine 32 is a bell nozzle engine or another type of rocket engine, or the vehicle may not include an engine at all.

[0018] 2, during use, second stage rocket 12 travels through an environment 14 (e.g., atmosphere, space) at a freestream Mach number 18, which can reach Mach 30 for a space re-entry vehicle. A bow shock 20 forms upstream of second stage rocket 12, and temperatures on the vehicle side of bow shock 20 can reach thousands of Kelvin. Because the upwind side 22 of second stage rocket 12 is exposed to such high temperatures, it requires cooling and / or other thermal protection for reuse.

[0019] The actively cooled heat shield system 10 includes a heat shield 34 , a tank 36 , a pump 16 , a heat exchanger 38 , and a turbine 40 .

[0020] Heat shield 34 defines the exterior surface of windward side 22 of second stage rocket 12 .

[0021] A tank 36 is carried by second stage rocket 12 and stores a coolant (eg, active coolant, liquid coolant, cryogenic coolant, etc.).

[0022] The pump 16 is carried on the second stage rocket 12 and receives coolant from a tank 36. The pump 16 outputs pressurized coolant (e.g., coolant having a pressure of several hundred psi or more), i.e., the pressure of the coolant after it passes through the pump 16 is greater than when the coolant is stored in the tank 36. The coolant is transferred from the tank 36 to the pump 16 via a coolant conduit 42 (e.g., a duct, a tube, etc.).

[0023] The heat exchanger 38 is carried by the second stage rocket 12 and is integrally connected to the heat shield 34. The heat exchanger 38 receives pressurized coolant from the pump 16, transfers heat from the heat shield 34 to the pressurized coolant to generate a heated fluid (e.g., gas, supercritical fluid, etc.), and outputs the heated fluid. The pressurized coolant is transported from the pump 16 to the heat exchanger 38 via a pressurized coolant conduit 44 (e.g., a duct, a tube, etc.).

[0024] The turbine 40 is mounted on the second stage rocket 12 and includes an inlet 46, a shaft 48, and an outlet 50. The inlet 46 receives the heated fluid output from the heat exchanger 38 via a primary heated fluid conduit 52 (e.g., a duct, a tube, etc.). In some embodiments, the heated fluid has excess energy that is bypassed around the turbine 40 via a bypass conduit 54 (e.g., a duct, a tube, etc.) and used to pressurize or power an auxiliary system 56 (e.g., a tank, a gas thruster, a transpiration cooling system, an auxiliary power unit (APU), etc.). The shaft 48 of the turbine 40 is coupled (e.g., directly coupled, indirectly coupled via a coupler, etc.) to the pump 16 and includes turbine blades (not shown) mounted thereon. When the heated fluid received from the heat exchanger 38 acts on the turbine blades (not shown), the shaft 48 rotates, thereby providing power to the pump 16. The outlet 50 of the turbine 40 outputs the heated fluid. In some embodiments, the second stage rocket 12 includes an exhaust conduit 58 through which the heated fluid exits the second stage rocket 12 (e.g., to provide thrust). Additionally or alternatively, the heated fluid output from the outlet 50 of the turbine 40 may be used to pressurize or power auxiliary systems (e.g., tanks, gas thrusters, transpiration cooling systems, APUs, etc.). The heated fluid output from the outlet 50 of the turbine 40 will have a lower pressure and energy than the pressure and energy of the heated fluid that is diverted to the auxiliary systems 56 through the bypass conduit 54. In some embodiments, the heat shield system 10 further includes bearings, gears, and / or seals (not shown) that facilitate coupling of the turbine 40 and the pump 16 via the shaft 48.

[0025] During operation of the heat shield system 10, pressurized coolant enters a heat exchanger 38 (e.g., a channel or other conduit formed in the heat shield 34) and is cooled at a rate (i.e., heat flux) typical of a hypersonic re-entry vehicle, e.g., between 0.01 and 10 BTU / in 2s。 Heat exchanger 38 serves the dual purpose of cooling the windward side 22 of the second stage 12 and adding energy to the coolant used to drive the turbine 40, which in turn powers the pump 16. The pressure of the coolant decreases while the total enthalpy increases along the heat exchanger 38 until the coolant exits the heat exchanger 38 as a heated fluid. The primary flow of heated fluid enters the turbine 40 where energy is extracted. The heated fluid exiting the turbine 40 may be discharged from the second stage 12 to the external environment 14 or used for another purpose (e.g., recooled by on-board systems and passed back through the heat exchanger 38 in a closed loop cycle).

[0026] In some embodiments, the pressure of the coolant in the tank 36 alone provides enough energy to initiate rotation of the turbine 40 and pump 16, resulting in an increase in pressure and power available to the turbine 40. In other embodiments, the pressure of the coolant in the tank 36 does not provide enough energy to initiate rotation of the turbine 40 and pump 16. In some such embodiments, the heat shield system 10 further includes an external starter source, such as a motor connected to the turbine shaft 48 or high pressure gas directed to the turbine 40.

[0027] In some embodiments, at least one component (e.g., tank 36, pump 16, turbine 40, etc.) is an existing component of engine 32. For example, in some embodiments, engine 32 includes at least a pump and a turbine that push coolant through a heat exchanger of the engine. In such embodiments, the fuel pump and turbine of engine 32 serve a dual purpose by functioning as pump 16 and turbine 40, respectively, of heat shield system 10, and the heat exchanger of engine 32 forms at least a portion of heat exchanger 38 of heat shield system 10.

[0028] In some embodiments, the heat shield system 10 additionally or alternatively further includes at least one component that is passively cooled (eg, using a high temperature material, etc.).

[0029] Once operation of the heat shield system 10 is initiated, the thermal energy added to the coolant is sufficient to sustain operation. Specifically, the energy added to the coolant is sufficient to provide the turbine 40 with the power required to drive the pump 16 after taking into account all losses in the system 10, including inefficiencies of the pump 16 and turbine 40, pressure losses in the heat exchanger 38, and other losses from friction and other mechanisms.

[0030] The coolant flowing through the heat exchanger 38 integrated into the windward side 22 of the second stage 12 is sufficient to maintain acceptable temperatures in the heat shield 34 and other walls of the second stage 12 while the second stage 12 passes through a hostile thermal environment (e.g., while the second stage 12 re-enters the atmosphere). The heat shield system 10 thus enables the second stage 12 to execute a base-first re-entry trajectory. This provides several important advantages over other proposed nose-first or body-first (also known as belly flop) strategies: (i) it eliminates the need for challenging atmospheric re-orientation maneuvers required for nose-first or body-first (also known as belly flop) re-entry vehicles with vertical landing profiles; (ii) it maintains the primary load path axially during all phases of flight, allowing for more efficient structural solutions; and (iii) the generally vertical orientation during ascent and re-entry simplifies the cryogenic fluid management challenges by minimizing slosh and associated boil-off. (iv) Minimize heat shield surface area while maintaining a low ballistic coefficient, thus minimizing the overall thermal load managed by the vehicle during re-entry.

[0031] Although several embodiments have been disclosed, it should be apparent to one skilled in the art that aspects of the present invention include many more embodiments. Thus, aspects of the present invention should not be limited except in light of the appended claims and their equivalents. It should also be apparent to one skilled in the art that changes and modifications can be made without departing from the true scope of the present disclosure. For example, in some cases, one or more features disclosed in connection with one embodiment can be used alone or in combination with one or more features of one or more other embodiments.

Claims

1. A vehicle, a heat shield defining an upwind side of said vehicle while traveling in an atmospheric re-entry trajectory; a tank configured to store a coolant; a pump configured to receive the coolant from the tank and output pressurized coolant; a heat exchanger configured to receive the pressurized coolant from the pump, transfer heat from the heat shield to the pressurized coolant to generate a heated fluid, and output the heated fluid; a turbine receiving the heated fluid output from the heat exchanger, extracting energy from the heated fluid, and using the extracted energy to power the pump.

2. 10. The vehicle of claim 1, wherein the vehicle is an upper stage rocket of a multi-stage rocket system.

3. 10. The vehicle of claim 1, wherein the heat exchanger and the heat shield are configured such that the flow of coolant through the heat exchanger maintains an acceptable temperature on the heat shield while the vehicle is traveling in an atmospheric re-entry trajectory.

4. 2. The vehicle of claim 1, wherein at least the heat exchanger, the turbine, and the pump are configured such that when operation of the pump begins, the amount of energy extracted from the heated fluid by the turbine is sufficient to continue operation of the pump alone.

5. the heat shield, the tank, the pump, the heat exchanger, and the turbine are components of a heat shield system; The vehicle of claim 1 , wherein the heat shield system is configured such that, upon initiation of operation, the amount of energy transferred by the heat exchanger to the coolant is at least sufficient to sustain operation.

6. the heat shield, the tank, the pump, the heat exchanger, and the turbine are components of a heat shield system; 2. The vehicle of claim 1, wherein the heat shield, the tank, the pump, the heat exchanger, and the turbine are configured such that an amount of energy transferred to the coolant by the heat exchanger is at least sufficient to sustain operation of the heat shield system.

7. 2. The vehicle of claim 1, wherein the heat shield, the tank, the pump, the heat exchanger, and the turbine are configured such that an amount of energy transferred to the coolant by the heat exchanger is at least sufficient to provide the turbine with an amount of power necessary to drive the pump.

8. 10. The vehicle of claim 1, wherein the pressure of the coolant in the tank alone provides enough energy to initiate rotation of the turbine and the pump, resulting in an increase in pressure and power available to the turbine.

9. the turbine is coupled to the pump and comprises a shaft having turbine blades mounted thereon; The vehicle of claim 1 , wherein the shaft is configured to rotate when the heated fluid received from the heat exchanger acts on the turbine blades, thereby providing power to the pump.

10. The vehicle of claim 9 , wherein the turbine comprises an outlet configured to output the heated fluid.

11. The vehicle of claim 10 further comprising an exhaust conduit through which at least a portion of the heated fluid output from the turbine exits the vehicle.

12. The vehicle of claim 1 further comprising a propulsion engine at the rear end of the vehicle.

13. The vehicle of claim 12 , wherein the heat shield is a heat shield for the propulsion engine.

14. 13. The vehicle of claim 12, wherein the tank is a fuel tank.

15. 13. The vehicle of claim 12, wherein the pump is a fuel pump for the propulsion engine.

16. 13. The vehicle of claim 12, wherein the heat exchanger is a heat exchanger of the propulsion engine.

17. 13. The vehicle of claim 12, wherein the turbine is the turbine of the propulsion engine.

18. a primary heating fluid conduit configured to transport the heating fluid from the heat exchanger to an inlet of the turbine; 10. The vehicle of claim 1, further comprising: a bypass conduit configured to bypass excess energy in the heating fluid from at least a portion of the primary heating fluid conduit for power use by an auxiliary system.

19. 20. The vehicle of claim 18, wherein the auxiliary system is a tank.

20. 20. The vehicle of claim 18, wherein the auxiliary system is a gas thruster.

21. 20. The vehicle of claim 18, wherein the auxiliary system is a transpiration cooling system.

22. 20. The vehicle of claim 18, wherein the auxiliary system is an auxiliary power unit.

23. The vehicle of claim 1 , wherein the coolant is an active coolant.

24. The vehicle of claim 1 , wherein the coolant is a liquid coolant.

25. The vehicle of claim 1 , wherein the coolant is a cryogenic coolant.

26. The vehicle of claim 1 , wherein the heating fluid is a gas.

27. The vehicle of claim 1 , wherein the heating fluid is a supercritical fluid.

28. the vehicle having a front end and a rear end opposite the front end; The vehicle of claim 1 , wherein the heat shield is disposed at the rear end.

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