Aircraft with a reaction control system

Abstract

The invention relates to a vehicle, in particular an aircraft or a space vehicle for a supersonic or hypersonic flight, comprising a fuel tank (3), a main propulsion system (4) driven by the fuel, and a cooling system (7, 8) with a cooling channel (7) for cooling a heat source (1). The fuel of the fuel tank acts as a coolant in the cooling system and absorbs heat while being conveyed through the cooling channel (7). The vehicle further comprises a reaction control system (12) with gas thrusters (2). The reaction control system (12) is connected to the cooling system (7, 8), wherein the reaction control system (12) is driven by the heated, gaseous fuel from the cooling system (7, 8).

Description

[0001] Aircraft with a reaction control system

[0002] Technical Field

[0003] The invention relates to a vehicle , in particular an aircraft or a space vehicle for a supersonic or hypersonic flight , in particular a re-entry vehicle with a propulsion system . It comprises a fuel tank, a main propulsion system, in particular driven by fuel from the fuel tank, and a cooling system with cooling channels for cooling a heat source , in particular a heat shield or the main propulsion system or structural parts of the vehicle ( e . g . leading edges or the airframe ) . The fuel acts as a coolant in the cooling systems and absorbs heat while it is being conveyed through the cooling channels . For this reason, the fuel is preferably cryogenic . The coolant might be moved through small heat exchanger channels by a high-pressure pump . Furthermore , the vehicle comprises a reaction control system with gas thrusters .

[0004] Background Art

[0005] A reaction control system (RCS ) is an aircraft or space vehicle system that uses thrusters to provide attitude control , and optionally manoeuvring . It is capable of providing small amount of thrust in any desired direction or combination of directions . A reaction control system is also capable of providing torque to allow control of rotation . This is vital in aircraft control , and traditionally accomplished with aerodynamic control surfaces like rudders and elevons .

[0006] Reaction control system thrusters for controlling pitch and yaw are usually arranged in nose or tail region of the vehicle , to increase their lever arm . Thrusters for roll can also be located on the wings . On blunt re-entry vehicles , the reaction control system is typically installed on the back. On rocket launchers, along the length of the cylindrical body.

[0007] Disclosure of the Invention

[0008] The problem to be solved by the present invention is to provide a vehicle with a compact and energy efficient reaction control system. This is achieved by integrating components and reducing complexity.

[0009] This problem is solved by a vehicle, in particular an aircraft or a space vehicle for a supersonic or hypersonic flight, according to claim 1. According to this, the vehicle comprises

[0010] - a fuel tank comprising fuel. The vehicle can include one or more fuel tanks, preferably containing liquid hydrogen in a cryogenic state, i.e. with a temperature around 20 K. Optionally, the vehicle includes a pressurization system designed to increase the pressure of the fuel up to at least 10 bar and typically between 30 and 100 bar.

[0011] - a main propulsion system, in particular driven by the fuel of the fuel tank. This engine might be a regular turbojet or a turborocket apparatus, comprising a compressor, a turbine, a combustion chamber and a gas generator system including a preburner. It could also be a rocket engine, a ramjet, or a scramjet. The highest speed engines have the most demanding cooling needs. To keep their metal structures cool, the use of cryogenic fuels like liquid hydrogen or liquid methane is favoured. The lower temperature fuel has more heat sink capacity.

[0012] - a cooling system with a cooling channel for cooling a heat source, in particular a heat shield or the main propulsion system or structural parts of the vehicle (e.g. leading edges or the airframe) . The cooling channel constitutes a heat exchanger. The fuel acts as a coolant and absorbs heat from the heat source while being conveyed through the cooling channel. The reaction control system i s most compact when the hea t source i s cl osest to the reacti on control system, so the l eading edges and nose regi on are preferred as hea t sources . The cooling system heats the fuel , vapori zes it and cools the heat source . After flowing through the cooling system, the hot , gaseous fuel is on a temperature between 300 and 1000 K .

[0013] - a reaction control system comprising gas thrusters . Preferably, the thrusters control attitude by modulating pitch, yaw and roll or a subset of them . The thrusters are typically arranged in nose and tail region of the vehicle . A reaction control system complements or replaces traditional aerodynamic controllers . For hypersonic planes flying above 10 km, a reaction control system allows si ze reduction compared to a traditional aerodynamic control system . Aerodynamic drag is reduced when the traditional aerodynamic controllers are smaller or only are deployed at small angles . For rocket launchers reaching space , the reaction control system and a rocket engine thrust vectoring are commonly the principal aerodynamic control methods . Typically, thrusters are standard metal expansion noz zles . Cold gas pressuri zed thrusters and combustion thrusters both exist . The latter are more common on large vehicles like high-speed aircraft and re-entry vehicles .

[0014] In particular, the thrusters operate with pressures between 10 and 30 bar to provide a good thrust- per-noz zle-si ze . The reaction control system consumable fluids are contained in pressuri zed vessels and routed to the thrusters with a dedicated feed system . The reaction control system gas thruster noz zles and valves often have electrical heaters to function reliably in the cold of high-altitude atmosphere or space . Depending on the fluid used, particulate filters are needed to avoid clogging the reaction control system .

[0015] The vehicle is characteri zed in that the reaction control system is connected to the cooling system, wherein the reaction control system is driven by the heated, gaseous fuel from the cooling system .

[0016] Feeding the reaction control system using hot coolant from the cooling system reduces the vehicle weight , part count and complexity of the vehicle . Fuel can be used both for cooling heat sources and for operating the reaction control system . Thus , the cooling system has a dual purpose , cooling heat sources and heating fuel for the reaction control system .

[0017] Replacing the reaction control system propellant feed system with a connection to the cooling system is practical , because the cooling system is already present on the vehicle . The reaction control system gives another purpose for heated coolant . It avoids wasting coolant in scenarios where main engines are disabled but structural cooling is required, for example during hypersonic glide of the vehicle or during an atmospheric reentry of capsules . The feed system and the fluid ( the fuel ) are likewise present already . Reducing the number of systems and fluids has the advantage of reducing vehicle complexity and weight .

[0018] In particular, a vehicle with the described reaction control system can be operated on altitudes between 10 and 100 km and at velocities until Mach 20 .

[0019] Advantageously, the heated, gaseous fuel ej ected through the gas thrusters is not combusted . Inj ectors , a complicated design, and high-temperature operation are avoided . No carbon emissions or particulates are emitted when hydrogen is used, which is also the most thermodynamically ef ficient fuel and coolant .

[0020] Preferably, the reaction control system comprises a run-through tank . A run-through tank is characteri zed by a run-through, in particular a permanent run- through, of fuel independent of the amount of fuel required by the reaction control system .

[0021] In particular, the run-through tank has a maximum cross-sectional area in fluid direction at least two times larger, at least three times larger, at least five times larger, at least ten times larger, as the maximum cross-sectional area of the feed channel via which hot , gaseous fuel is conveyed from the cooling system to the run-through tank . This definition illustrates the larger volume of the tank compared to the feed channel . The purpose of the area increase is to reduce the flow velocity and increase the static pressure , allowing hot gas coolant to be branched of f to feed the RCS thrusters . The tank serves as a buf fer for coolant pressure and mass rate fluctuations .

[0022] The run-through tank allows feeding the reaction control system with hot coolant without accumulating unspent coolant , and without losing gas pressure or temperature or availability, which could compromise the reaction control system functioning .

[0023] Advantageously, the reaction control system comprises

[0024] - a feed channel via which hot , gaseous fuel is conveyed from the cooling system to the run-through tank,

[0025] - an excess channel via which excess fuel not used by the reaction control system is conveyed out of the run-through tank, and

[0026] - a thruster channel connecting the run- through tank with the gas thrusters .

[0027] In particular, excess fuel is j ettisoned, conveyed to an engine or conveyed to another cooling system of the vehicle .

[0028] In a preferred embodiment , the reaction control system comprises a bypass channel , bypassing the run-through tank, such that fuel conveyed through the bypass channel does neither flow through the run-through tank nor through the gas thrusters . This avoids that all coolant has to flow through the run-through tank, which reduces pressure fluctuations inside the run-through tank . In particular, the bypass channel comprises a valve for partially or completely opening or closing the bypass channel .

[0029] The reaction control system might comprise a measurement unit for measuring the pressure inside the run-through tank, and wherein the valve is controlled such that pressure fluctuations inside the run-through tank are reduced . An almost constant pressure is required for a precise attitude control of the vehicle by the reaction control system .

[0030] Advantageously, the run-through tank is adapted to change its volume in order to equali ze pressure of the fuel inside the run-through tank . It might be a compensation bellow tank, which automatically adj usts its volume to equali ze pressure while filling and emptying the tank .

[0031] In particular, the run-through tank is constantly refilled with hot , gaseous fuel from the cooling system, while the cooling system is in operation . As already said, no unspent coolant is accumulated inside the tank and cooling of the gaseous full inside the tank is avoided .

[0032] In a preferred embodiment , the reaction control system comprises a first tank and a second tank, wherein both the first and the second tank comprise an inlet valve and an outlet valve , such that both tanks can be filled and emptied separately from each other . The tanks empty and fill alternatingly . Both tanks are connected with the cooling system via a feed channel for conveying hot , gaseous fuel from the cooling system to the tanks , and are connected with the gas thrusters via thruster channels . The inlet and outlet valves are controlled such that the first tank is filled as the second tank is emptied, and the second tank is filled as the first tank is emptied . Emptying means that hot , gaseous fuel is conveyed to the gas thrusters . Alternatively, the reaction control system comprises a tank, in particular exactly one tank, connected with the cooling system via a feed channel , and connected with the gas thrusters via a thruster channel . The thruster channel comprises a pressure reduction unit . The pressure reduction unit buys time to refill the tank before its pressure becomes insuf ficient to drive the reaction control system . It limits the maximum thrust production . This reali zation relies most on active control .

[0033] In particular, the vehicle comprises an emergency bypass channel bypassing the cooling system for conveying fuel from the fuel tank to the reaction control system . In scenarios like broken structural cooling system or broken run-through tank, the coolant is fed directly to the reaction control system and maintains the operation of it . In case fuel is fed to the reaction control system via the emergency bypass , fuel is not heated by the cooling system . The ef ficiency of the reaction control system is reduced, i . e . the thrust speci fic impulse is reduced, but the pressure is not reduced . The pressure is at least as high as usual . Thus , enough thrust is produced but less ef ficiently . In particular, the thrusters control system is adaptable to higher density flows , or electrical heaters are installed to preheat the coolant for reaction control system operation .

[0034] Advantageously, the cooling channels are arranged at leading edges or in a nose region of the vehicle for absorbing heat .

[0035] In particular, the fuel is hydrogen providing superior thermal properties for cooling and a high speci fic impulse for propulsion, e . g . 400 to 500 s at 500 to 1 ' 000 Kelvin .

[0036] Other advantageous embodiments are listed in the dependent claims as well as in the description below .

[0037] Brief Description of the Drawings The invention will be better understood and obj ects other than those set forth above will become apparent from the following detailed description thereof . Such description makes reference to the annexed drawings , wherein :

[0038] Fig . 1 shows a 3D view of a high-speed aircraft comprising a cooling system and a reaction control system;

[0039] Fig . 2 shows a schematic drawing illustrating the cooling system and the reaction control system according to a first embodiment of the invention;

[0040] Fig . 3 shows a schematic drawing illustrating the cooling system and the reaction control system according to a second embodiment of the invention;

[0041] Fig . 4 shows a schematic drawing illustrating the cooling system and the reaction control system according to a third embodiment of the invention, and

[0042] Fig . 5a and 5b a compensation bellow tank acting as a run-through tank .

[0043] Modes for Carrying Out the Invention

[0044] The accompanying drawings show simpli fied representations of devices or parts thereof , as involved in embodiments . Technical features depicted in the drawings are not necessarily to scale . Similar or functionally similar elements in the figures have been allocated the same numeral references , unless otherwise indicated .

[0045] Fig . 1 shows an aircraft which might be a drone or a high-speed plane , such as a supersonic or hypersonic plane . As usual , the aircraft includes an aircraft structure . The internal load bearing structure is a structural assembly typically made from frames , stringers , spars , ribs and panels , which are usually machined or formed from sheet metal .

[0046] An aircraft entering from outer space into and through the gases of an atmosphere or an aircraft flying in the atmosphere on hypersonic velocity experiences high atmospheric drag, which puts mechanical stress on the aircraft , and aerodynamic heating . Such vehicles intended for atmospheric entry or hypersonic flight require a thermal protection system which protects the vehicle structure from damage created by high temperature that can reach thousands of Kelvins .

[0047] The present aircraft comprises a cooling system with heat shields 1 made from temperature-resistant metal alloys that incorporate a coolant circulating through them . Heat shields are arranged at least at the nose and at the leading edges of the wings . The cooling system will be described below .

[0048] The aircraft shown in Fig . 1 comprises a reaction control system . It is an aircraft system that uses gas thrusters 2 to provide attitude control . It is capable of providing small amount of thrust in any desired direction or combination of directions .

[0049] Fig . 2 shows a schematic drawing illustrating the cooling system and the reaction control system according to a first embodiment of the invention . The aircraft comprises a hydrogen tank 3 which stores liquid hydrogen in a cryogenic state , i . e . with a temperature around 20 K and a pressure between 1 and 2 bar . Liquid hydrogen is a common liquid fuel for driving a main propulsion system 4 , as shown in Fig . 1 . The hydrogen tank takes up much space and weight in the vehicle .

[0050] A pressuri zation system 5 pumps the liquid hydrogen out of tank 3 and compresses it to a pressure between 10 and 100 bar . The temperature stays in the range between 20 and 50 k . The liquid hydrogen is further conveyed to a heat exchanger 6 through a cooling channel 7 . A separate coolant circulates in a separate circuit 8 , absorbs heat from the heat shields 1 and trans fers the heat to the fuel flowing through the cooling channel 7 via the heat exchanger 6 . The heat shield 1 is cooled . Heat exchanger 6 , cooling channel 7 and separate circuit 8 are part of the cooling system .

[0051] The fuel circulating in cooling channel 7 absorbs the heat , vapori zes and leaves the heat exchanger 6 with a temperature between 300 and 1 ' 000 K .

[0052] The hot , gaseous fuel is further conveyed to a run-through tank 9 via feed channel 10 . The run-through tank 9 is capable of temporarily storing hot , gaseous fuel . It has a much larger cross-sectional area than the feed channel 10 . The run-through 9 tank has typical diameters between 2 and 10 times the diameter of the feed channel 10 . The run-through tank is insulated or cooled .

[0053] The run-through tank 9 is further connected to the gas thrusters 2 via a thruster channel 11 . Gas thrusters 2 are standard metal expansion noz zles and the hot , gaseous hydrogen is not combusted . The run-through tank 9 and the gas thrusters 2 are part of the reaction control system 12 . Valves 13 are arranged between the run-through tank 9 and the gas thrusters 2 for controlling thrust output per noz zle .

[0054] Additionally, the run-through tank 9 is connected to an excess channel 14 . Excess fuel not used by the reaction control system is conveyed out of the run- through tank 9 . Excess fuel is j ettisoned, conveyed to an engine or conveyed to another cooling system of the aircraft .

[0055] A bypass channel 15 is arranged parallel to the run-through tank 9 . Excess fuel can be conveyed directly from the feed channel 10 to the excess channel 14 without flowing through the run-through tank 9 . A valve 16 is provided to open and close the bypass channel 15 .

[0056] The run-through tank 9 acts as a plenum to equali ze pressure . The run-through tank 9 is constantly refilled with hot , gaseous and pressuri zed hydrogen . The hydrogen never cools . The run-through tank 9 comprises a measurement unit 17 for measuring the pressure inside the run-through tank 9 . Valve 16 is controlled such that pressure fluctuations inside the run-through tank 9 are reduced .

[0057] Fig . 5a and 5b show a speci fic design of a run-through tank 9 . It is a compensation bellow tank capable of changing its volume to equali ze pressure during filling and emptying . Fig . 5a shows the compensation bellow tank in a compressed state and Fig . 5b shows the compensation bellow tank with an extended volume .

[0058] The connection between the cooling system and the reaction control system allows to maintain a stable hydrogen feed . The reaction control system 12 can be operated in intermittent mode , continuous mode or pulsed mode .

[0059] The aircraft further comprises an emergency bypass channel 18 . In scenarios like broken structural cooling system or broken run-through tank 9 , the coolant is fed directly to the reaction control system 12 and maintains the operation of it . In such emergency cases , valve 19 is opened and hydrogen is directly conveyed from the pressuri zation system 5 to the gas thrusters 2 via the emergency bypass channel 18 .

[0060] Fig . 3 shows an alternative reaction control system . It comprises a simple tank 20 without a permanent run-through . Hydrogen is filled into tank 20 and the filling is controlled by valve 21 . I f the tank 20 is full , valve 22 of the excess channel 23 is opened and the hydrogen is j ettisoned or conveyed to another part of the aircraft via excess channel 23 . Hydrogen stays inside tank 20 until hydrogen is pushed out through the gas thrusters . Thus , hydrogen is allowed to cool in tank 20 , which reduces ef ficiency in the reaction control system .

[0061] A pressure reducer 24 is arranged downstream from tank 20 . It buys time to refill tank 20 before its pressure becomes insuf ficient to drive the reaction control system .

[0062] Fig . 4 shows a further alternative reaction control system . It comprises a first tank 30 and a second tank 31 . Both tanks 30 and 31 are filled and emptied by controlling inlet valves 32 and outlet valves 33 by a control device 34 . One tank is filled as another tank is emptied .

[0063] Heat source / heat shield Gas thrusters

[0064] Hydrogen tank

[0065] Main propulsion system Pressuri zation system Heat exchanger

[0066] Cooling channel Separate circuit Run-through tank Feed channel

[0067] Thruster channel

[0068] Reaction control system Valve

[0069] Excess channel

[0070] Bypass channel

[0071] Valve

[0072] Measurement unit

[0073] Emergency bypass channel Valve

[0074] Tank

[0075] Valve

[0076] Valve

[0077] Excess channel

[0078] Pressure reduction unit

[0079] First tank

[0080] Second tank

[0081] Inlet Valve Outlet valve

[0082] Control device

Claims

Claims1. Vehicle, in particular an aircraft or a space vehicle for a supersonic or hypersonic flight, comprising- a fuel tank (3) comprising fuel,- a main propulsion system (4) , in particular driven by the fuel,- a cooling system (7, 8) with a cooling channel (7) for cooling a heat source (1) , in particular a heat shield, the main propulsion system or structural parts of the vehicle, wherein the fuel acts as a coolant and absorbs heat while being conveyed through the cooling channel ( 7 ) ,- a reaction control system (12) comprising gas thrusters (2) , characterized in that the reaction control system (12) is connected to the cooling system (7, 8) , wherein the reaction control system (12) is driven by the heated, gaseous fuel from the cooling system (7, 8) .

2. Vehicle according to claim 1, wherein the heated, gaseous fuel ejected through the gas thrusters (2) is not combusted.

3. Vehicle according to any one of the preceding claims, wherein the reaction control system (12) comprises a run-through tank (9) .

4. Vehicle according to claim 3, wherein the run-through tank (9) has a maximum cross-sectional area in fluid direction at least two times larger, at least three times larger, at least five time larger, at least ten time larger, as the maximum cross-sectional area of a feed channel (10) via which hot, gaseous fuel is conveyed from the cooling system (7, 8) to the run-through tank(9) .

5. Vehicle according to claim 3 or 4, wherein the reaction control system (9) comprises- a feed channel (10) via which hot, gaseous fuel is conveyed from the cooling system (7, 8) to the run-through tank (9) ,- an excess channel (14) via which excess fuel not used by the reaction control system (12) is conveyed out of the run-through tank (9) , and- a thruster channel (11) connecting the run- through tank (9) with the gas thrusters (2) .

6. Vehicle according to claim 5, where excess fuel is jettisoned, conveyed to an engine or conveyed to another cooling system.

7. Vehicle according any one of the claims 3 to 6, wherein the reaction control system (12) comprises a bypass channel (15) , bypassing the run-through tank (9) , such that fuel conveyed through the bypass channel(15) does neither flow through the run-through tank (8) nor through the gas thrusters (2) .

8. Vehicle according to claim 7, wherein the bypass channel (15) comprises a valve (16) for opening and closing the bypass channel (15) .

9. Vehicle according to any one of the claims 3 to 8, wherein the reaction control system (12) comprises a measurement unit (17) for measuring the pressure inside the run-through tank (9) , and wherein the valve(16) is controlled such that pressure fluctuations inside the run-through tank (9) are reduced.

10. Vehicle according to any one of the claims 3 to 9, wherein the run-through tank (9) isadapted to change its volume to equalize pressure of the fuel inside the run-through tank (9) .

11. Vehicle according to claim 10, wherein the run-through tank (9) is a compensation bellow tank.

12. Vehicle according to any one of the claim 3 to 11, wherein the aircraft is adapted such that the run-through tank (9) is constantly refilled with hot, gaseous fuel from the cooling system (7, 8) , while the cooling system (7, 8) is in operation.

13. Vehicle according to claim 1 or 2, wherein the reaction control system (12) comprises a first tank (30) and a second tank (31) , wherein both the first (31) and the second (32) tank comprise an inlet valve (32) and an outlet valve (32) , such that both tanks (31, 32) can be filled and emptied separately from each other, wherein both tanks (31, 32)- are connected with the cooling system (7, 8) via a feed channel (10) for conveying hot, gaseous fuel from the cooling system (7, 8) to the tanks (31, 32) ,- are connected with the gas thrusters (2) via thruster channels (11) .

14. Vehicle according to claim 13, wherein the first (30) and the second (31) tank have a maximum cross-sectional area in fluid direction at least two times larger, at least three times larger, at least five time larger, at least ten time larger, as the maximum cross-sectional area of the feed channel (10) .

15. Vehicle according to claim 13 or 14, wherein a control device (34) is adapted to control the inlet (32) and outlet (33) valves such that- the first tank (30) is filled as the second tank (31) is emptied, and- the second tank (31) is filled as the first tank (30) is emptied, wherein the tanks (30, 31) are emptied for conveying hot, gaseous fuel to the gas thrusters (2) .

16. Vehicle according to claim 1 or 2, wherein the reaction control system (12) comprises a tank (20) , in particular exactly one tank, with the following features: the tank- is connected with the cooling system (7, 8) via a feed channel (10) ,- is connected with the gas thrusters (2) via a thruster channel (11) ,- has a maximum cross-sectional area in fluid direction at least two times larger, at least three times larger, at least five time larger, at least ten time larger, as the maximum cross-sectional area of the feed channel (10) , and wherein the thruster channel (11) comprises a pressure reduction unit (24) .

17. Vehicle according to any one of the preceding claims, wherein the aircraft comprises an emergency bypass channel (18) bypassing the cooling system (7, 8) for conveying fuel from the fuel tank (3) to the reaction control system (7, 8) .

18. Vehicle according to any one of the preceding claims, comprising a pressurization system (5) designed to increase the pressure of the fuel up to at least 10 bar before entering the cooling system (7, 8) .

19. Vehicle according to any one of the preceding claims, wherein the cooling channel (7) is arranged at leading edges or in a nose region of the aircraft for absorbing heat.

20. Vehicle according to any one of the preceding claims, wherein the fuel is hydrogen.

21. Vehicle according to any one of the pre- ceding claims, wherein the gas thrusters (2) are expansion nozzle integrated in the vehicle surface, in particular arranged in nose or tail region.

Images