PROPULSION SYSTEM FOR A VEHICLE USING HEAT ENERGY ABSORBED IN AN ACTIVE COOLING SYSTEM

Abstract

A vehicle for supersonic or hypersonic flight comprises a thermal rocket engine (1b) with a nozzle (2) and an active cooling system (8). The active cooling system cools a heat shield (6, 7). A working fluid absorbs heat inside the active cooling system and the heated working fluid expands through the nozzle to create thrust. Such a vehicle is suitable to fly a multi-skip trajectory, a boost-glide trajectory, a trajectory with a cruise phase or a re-entry into an atmosphere, for example.

Claims

1. A vehicle for a supersonic or hypersonic flight, comprising: at least one thermal rocket engine with at least one nozzle, an active cooling system having cooling channels for cooling a heat shield, wherein the thermal rocket engine and the active cooling system comprise: a working fluid absorbing heat in the active cooling system, the heated working fluid expanding through the at least one nozzle to create thrust.

2. The vehicle according to claim 1, wherein the active cooling system is the main, in particular the only, thermal source for the working fluid of the thermal rocket engine.

3. The vehicle according to claim 1, wherein the working fluid absorbs heat while flowing through the cooling channels, in particular absorbing heat from vehicle elements with different designed maximum temperatures, or a coolant absorbs heat while flowing through the cooling channels and the absorbed heat is transferred from the coolant to the working fluid via a heat exchanger.

4. The vehicle according to claim 1, wherein the heat shield is adapted to protect the vehicle during a supersonic or hypersonic flight, in particular to protect leading edges in particular a nose or a front of wings, in particular wherein the heat shield is made of metal, in particular of an austenitic nickel-chromium-based superalloy.

5. The vehicle according to claim 1, wherein the thermal rocket engine is usable for the main propulsion of the vehicle.

6. The vehicle according to claim 1, wherein the thermal rocket engine is usable for de-accelerating the vehicle, in particular wherein at least one of the at least one nozzle is arranged at a front of the vehicle.

7. The vehicle according to claim 1, comprising a reaction control system with at least one nozzle, wherein the heated working fluid expands through the at least one nozzle of the reaction control system.

8. The vehicle according to claim 1, wherein the active cooling system is adapted to heat the working fluid by ?T of at least 500 Kelvin, in particular at least 800 Kelvin, in particular at least 1000 Kelvin, in particular at least 1200 Kelvin.

9. The vehicle according to claim 1, wherein the working fluid is hydrogen.

10. The vehicle according to claim 1, comprising a thermal energy accumulator, in particular a tank, for storing working fluid heated by the active cooling system.

11. The vehicle according to claim 10, wherein the thermal energy accumulator comprises an inert mass or phase-change material.

12. The vehicle according to claim 1, comprising a heat exchanger for vaporizing cold, stored working fluid before introducing the working fluid into the active cooling system.

13. The vehicle according to claim 1, comprising a chemical rocket engine.

14. The vehicle according to claim 13, wherein the chemical rocket engine is operable simultaneously with the thermal rocket engine.

15. The vehicle according to claim 13, wherein the thermal rocket engine and the chemical rocket engine share the at least one nozzle.

16. The vehicle according to claim 13, wherein the thermal rocket engine and the chemical rocket engine share compressors.

17. The vehicle according to claim 1, wherein the vehicle is a spaceplane.

18. The vehicle according to claim 1, suitable to fly a multi-skip trajectory or a boost-glide trajectory or a trajectory with a cruise phase or a re-entry trajectory.

19. A method for operating a vehicle wherein the vehicle comprises: at least one thermal rocket engine with at least one nozzle, an active cooling system having cooling channels for cooling a heat shield, wherein the method comprises the following steps: working fluid flows through the active cooling system, in particular through the cooling channels, and the working fluid absorbs heat, the heated working fluid expands through the at least one nozzle to create thrust.

20. The method according to claim 19, wherein the working fluid is not further heated before expanding through the nozzle.

21. The method according to claim 19, wherein the method comprises a flight phase with a supersonic or hypersonic speed, while the vehicle is propelled, in particular mainly propelled, by the at least one thermal rocket engine.

22. The method according to claim 19, wherein the method is applied during one or several skips of a multi-skip flight or during a boost-glide flight, or during a cruise phase or during an atmospheric re-entry.

23. The method according to claim 21, wherein the vehicle is propelled by the at least one thermal rocket engine only from a beginning of an initial entry or later.

24. The method according to claim 19, wherein the vehicle comprises a chemical rocket engine, wherein the at least one thermal rocket engine and the chemical rocket engine are working simultaneously.

25. The method according to claim 24, wherein not the at least one thermal rocket engine but the chemical rocket engine is operating during launch of the vehicle to its suborbital trajectory.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The invention will be better understood and objects other than those set forth above will become apparent from the following detailed description thereof. Such description makes reference to the annexed drawings, wherein:

[0051] FIG. 1 shows a vehicle according to the invention;

[0052] FIG. 2 shows a possible multi-skip-flight trajectory of the vehicle of FIG. 1;

[0053] FIG. 3 shows a possible trajectory of the vehicle of FIG. 1 with a cruise phase;

[0054] FIG. 4 shows a possible flight trajectory of the vehicle of FIG. 1 with one single skip; and

[0055] FIG. 5 shows a possible flight trajectory with an atmospheric re-entry.

MODES FOR CARRYING OUT THE INVENTION

[0056] FIG. 1 shows a schematic drawing of a vehicle according to the invention. The vehicle comprises a rocket engine 1 with a main nozzle 2. The main nozzle 2 is arranged at the back of the vehicle and creates substantial thrust for propelling the vehicle in the main flight direction 3. The vehicle can transport a payload P.

[0057] The vehicle further comprises hydrogen tanks 4 which store liquid hydrogen in a cryogenic state, i.e. with a temperature around 20 K. Liquid hydrogen is a common liquid fuel for rocket engines. These hydrogen tanks take up much space and weight in the vehicle. Oxygen tanks are arranged in the centre part of the vehicle. Hydrogen is mixed with the oxidizer oxygen and burned in a chemical rocket engine 1a, which is part of the rocket engine 1.

[0058] The vehicle shown in FIG. 1 comprises heat shields arranged at leading edges. Leading edges of this vehicle are the nose and the front of the wings.

[0059] First leading edges 6 are arranged at the nose and second leading edges 7 are arranged at the front of the wings. The wings comprise aerodynamic control surfaces like flaps. The heat shields are cooled by an active cooling system 8 comprising multiple cooling channels while the vehicle flights through the gases of an atmosphere. The atmosphere drags and heats the vehicle.

[0060] Furthermore, the rocket engine 1 comprises a thermal rocket engine 1b. A thermal rocket engine is understood to be an engine which does not burn the fuel. The thermal rocket engine works as follows:

[0061] Liquid hydrogen pumps out of the hydrogen tanks 4 with an electrical pump or turbopump and vaporizes inside the heat exchangers 9. The gaseous hydrogen is under high pressure due to its vaporization. It can further be compressed by the compressors 10 and further flows into the cooling channels of the active cooling system 8. Inside the active cooling system 8 the gaseous hydrogen absorbs heat by convective heat transfer. The heat shield is cooled and the gaseous hydrogen is heated up. Hydrogen flows out of the cooling channels with a temperature of around 1000? C. and can be stored in a hot hydrogen tank 11. The storage of hydrogen is possible but not necessary. Also thermal energy accumulator could be used to store some of the energy during active cooling, and release this energy to the working fluid (heat hydrogen for example) when active cooling is not operating. Heated, gaseous hydrogen can directly flow through a compressor 12 into the thermal rocket engine 1b which is part of the rocket engine 1. The thermal rocket engine 1b does not burn the hydrogen, but the hydrogen only expands through the nozzle 1 due to its heat absorbed inside the cooling channels. With other words, the active cooling system is the only thermal source for the working fluid which is used as a reaction mass in the thermal rocket engine.

[0062] Hydrogen has good cooling capabilities and can provide around 18.6 MJ/kg liquid hydrogen for a 1000? C. hot surface. Around 1000 kg of liquid hydrogen is needed to dissipate 20000 MJ of energy, which should be enough for the vehicle mass around 5000 kg re-entering atmosphere one or several times.

[0063] Gaseous hydrogen heated up to 1000? C. and used as a reaction mass in the rocket engine provides a specific impulse in the vacuum of around 610 sec, which is significantly higher than for any known chemical rockets. The propulsion system can use the same working fluid for cooling the heat shield and for propelling the vehicle. This decreases the needed initial velocity of the vehicle and reduces the required mass for propellant components. If the active cooling system cools the heat shield around 1000? C., the heat shield can be made from low-cost, high-temperature resistant steel alloys, such as Inconel.

[0064] The heated hydrogen does not have to be stored in the hot hydrogen tank 11 if propulsion is required at the same time as the atmosphere drags and heats the vehicle. Such an application is required during a suborbital skip-glide flight, which will be further illustrated in FIG. 2.

[0065] Heated hydrogen cannot only be used to create trust for propelling the vehicle in the main flight direction 3. Heated hydrogen can also be used as reaction mass in nozzles 13 arranged at the front in order to deaccelerate the vehicle or as a reaction mass for a reaction control system illustrated by the nozzles 14.

[0066] As already mentioned, the rocket engine does not only comprise a thermal rocket engine. It also comprises a chemical rocket engine. A chemical rocket engine is especially required during an initial phase of the space flight, if hydrogen cannot be heated up to a sufficient high temperature or if more thrust is required as can be provided by the heated hydrogen. Gaseous hydrogen, heated or unheated, is mixed with oxygen stored in tanks 5 and the mixture is burned inside a combustion chamber of the chemical rocket engine.

[0067] The rocket engine can work either as a thermal rocket engine or as a chemical rocket engine. But on the other hand, the rocket engine can simultaneously work as a thermal rocket engine and a chemical rocket engine. In the latter case, a part of hydrogen is heated up by the cooling system and flows through the nozzle without being burned. In the same time, another part of hydrogen is mixed with oxygen and burned inside the combustion chamber.

[0068] Both the thermal rocket engine and the chemical rocket engine can share compressors and nozzles.

[0069] FIG. 2 shows a possible flight trajectory of the vehicle of FIG. 1. It shows a spaceflight of a suborbital transportation to any destination on Earth. It is a trajectory of a multi-skip flight.

[0070] On take-off 21, a rocket booster (not shown in FIG. 1) propels the vehicle from a specially designed hyperport to its trajectory. The booster is separated from the rocket at trajectory point 22 and lands vertically back at the hyperport, where the ground team can prepare it for the next flight. Such boosters are well known and can be operated by liquid hydrogen and liquid oxygen.

[0071] After booster separation, i.e. after the flight phase indicated by a in FIG. 2, the vehicle is propelled by the chemical rocket engine. This flight phase is indicated by b in FIG. 2 and ends with reaching the apogee. Then, the flight is followed by a multi-skip trajectory. This is a trajectory that extends the range of the suborbital vehicle by using aerodynamic lift in the atmosphere. It can significantly extend the range over the ballistic trajectory depending on the number of entries.

[0072] From the beginning of the first entry, i.e. starting with phase c1, the vehicle is mainly propelled by the thermal rocket engine. Depending on the trajectory, the propulsion might be supported by the chemical rocket engine. The vehicle flies two loops c1 and c2 and then the flight ends with a landing phase d.

[0073] Thus, the present vehicle has two different delta-V sources. First, the chemical rocket engine propels the vehicle and the vehicle ends up with a total delta-V at first entry that can achieve 4000-5000 m/sec. Secondly, the thermal rocket engine creates another delta-V of 2000-3000 m/sec to sustain velocity decreased by atmospheric drag, or even increase the velocity.

[0074] FIG. 3 shows an alternative trajectory. It is the trajectory of a steady-flight or cruise in the atmosphere. The flight-phases a and b are identical to the trajectory shown in FIG. 2. After apogee, the vehicle flies on a constant altitude or varying altitude within the atmosphere and is propelled separately or simultaneously by the thermal rocket engine and by the chemical rocket engine.

[0075] FIG. 4 shows another alternative flight trajectory. It is the trajectory of a boost-glide flight comprising only one single skip. After booster separation at point 22, the vehicle is propelled primarily by the chemical rocket engine. The vehicle follows a ballistic trajectory.

[0076] FIG. 5 shows the flight trajectory of a vehicle entering the atmosphere from the space. The flight phase is called re-entry.