An air-breathing vehicle for long-term flight in the upper atmosphere

Abstract

The present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere, relating to the technical field of upper-atmosphere aircraft, comprising: an aircraft body, the aircraft body having an air-breathing electric propulsion system, the aircraft body having a cylindrical outer contour, an air inlet duct provided at the center of the aircraft body, the air inlet duct comprising a tapered conical inlet duct, an inwardly concave tapered compression duct, a cylindrical ionization acceleration duct, and a gradually diverging conical outlet duct arranged in sequence from front to back; a solar cell wing, the solar cell wing being arranged on the outside of the aircraft body, the solar cell wing being a forward-swept trapezoidal wing, and capable of supplying power to the air-breathing electric propulsion system; and solving the problem in the prior art of how to achieve a thrust and drag balance in aerodynamic shape design of an aircraft for long-term flight in the upper atmosphere, which has technical defects.

Description

Technical Field

[0001] The present invention belongs to the technical field of upper atmosphere aircraft, and more particularly, relates to an air-breathing aircraft for long-term flight in the upper atmosphere. Background Art

[0002] Upper-atmospheric spacecraft are aircraft that fly for extended periods at altitudes between 100km and 300km. Compared to low-orbit satellites, upper-atmospheric spacecraft offer advantages such as higher spatial resolution for ground-based observation or reconnaissance, lower launch costs, shorter communication delays, and reduced communication losses. Furthermore, the flight environment for upper-atmospheric spacecraft is safer because the thin atmosphere blocks some cosmic rays, resulting in lower cosmic ray intensity. Furthermore, the thin atmospheric drag causes space debris in this area to automatically decay and crash, reducing the risk of collision with space debris. Given the current shortage of high, medium, and low-orbit resources, developing and utilizing the upper-atmospheric airspace will undoubtedly improve the utilization of orbital space. Furthermore, if the propulsion system fails, upper-atmospheric spacecraft will automatically crash, preventing the creation of new space debris.

[0003] However, the upper atmosphere, the region between near-space and outer space, has an extremely low atmospheric density, making it nearly impossible for aircraft to utilize aerodynamic forces for maneuvering. Spacecraft, however, are hindered by atmospheric drag, preventing them from maintaining orbital altitude and performing orbital maneuvers. This is because the fuel consumption required to overcome atmospheric drag, maintain orbital altitude, and perform orbital maneuvers is prohibitive. Consequently, no mature aircraft currently possess the capability to conduct long-term flight in the upper atmosphere, and this airspace remains largely unexplored. A key challenge in the research of upper-atmosphere aircraft lies in their aerodynamic design, particularly how to achieve a balance between thrust and drag under limited solar energy supply. Currently, no significant technological breakthroughs have been achieved, yet this is precisely the core technology for achieving long-term flight in the upper atmosphere. Summary of the Invention

[0004] The purpose of the present invention is to address the deficiencies in the prior art and provide an air-breathing aircraft for long-term flight in the upper atmosphere, thereby solving the technical defects in the aerodynamic design of the prior art regarding how to achieve a balance between thrust and drag for aircraft for long-term flight in the upper atmosphere.

[0005] To achieve the above object, the present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere, comprising:

[0006] An aircraft body, the aircraft body having an air-breathing electric propulsion system, the aircraft body having a cylindrical outer contour, an air inlet duct disposed at the center of the aircraft body, the air inlet duct comprising, arranged in sequence from front to back, a tapered inlet duct, an inwardly concave tapered compression duct, a cylindrical ionization acceleration duct, and a gradually diverging tapered outlet duct;

[0007] A solar cell wing is arranged on the outside of the aircraft body, the solar cell wing is a forward-swept trapezoidal wing, and the solar cell wing can provide power for the air-breathing electric propulsion system.

[0008] Optionally, a front end radius of the tapered inlet duct is equal to an outer contour radius of the aircraft body.

[0009] Optionally, the taper angle of the tapered inlet duct differs from the sweep angle of the forward-swept trapezoidal wing by -10° to 10°.

[0010] Optionally, the cross-sectional profile of the inwardly concave tapered compression pipe is arc-shaped, and the front end radius of the inwardly concave tapered compression pipe is equal to the rear end radius of the tapered conical inlet pipe.

[0011] Optionally, the radius of the cylindrical ionization acceleration pipe is 25% to 75% of the radius of the rear end of the tapered inlet pipe.

[0012] Optionally, the radius of the front end of the gradually diverging conical outlet pipe is equal to the radius of the cylindrical ionization acceleration pipe.

[0013] Optionally, the front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body.

[0014] Optionally, the rear end of the root of the forward-swept trapezoidal wing extends out of the rear end of the aircraft body.

[0015] Optionally, a pair of solar cell wings are symmetrically arranged on the outside of the aircraft body.

[0016] Optionally, the forward-swept trapezoidal wing is a flat plate structure, and the thickness of the forward-swept trapezoidal wing is 20 mm to 40 mm.

[0017] The present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere, and its beneficial effects are as follows: the aircraft body of the air-breathing aircraft for long-term flight in the upper atmosphere is provided with an air-breathing electric propulsion system. Based on the aerodynamic characteristics of the upper atmosphere, and considering that the thin atmosphere in the upper atmosphere will generate resistance, which makes it difficult for the aircraft to fly for a long time, the air-breathing electric propulsion system is used to generate thrust to overcome the resistance generated by the thin atmosphere. At the same time, solar cell wings are arranged on the outside of the aircraft body, and the electric energy of the air-breathing electric propulsion system is provided by the solar cell wings to meet the energy supply demand; the aircraft body can carry a payload, and the air inlet of the air-breathing electric propulsion system is located at the center of the aircraft body, which is used for passage. Hole structure, gas enters the air inlet through a tapered conical inlet pipe, is compressed in an inwardly concave tapered compression pipe, then is ionized and accelerated in a cylindrical ionization acceleration pipe, and finally is discharged through a gradually expanding tapered outlet pipe to generate thrust; the solar cell wing adopts a forward-swept trapezoidal wing. The existence of the forward sweep angle and the increase of the cone angle with the tapered conical inlet pipe increase the effective inlet size of the air inlet, which is conducive to the high-speed and low-density upper atmosphere entering the air inlet, thereby improving the gas collection performance of the air inlet; after the air inlet collects and compresses the low-density upper atmosphere, the air-breathing electric propulsion system ionizes and accelerates it through the electrical energy provided by the solar cell wing to generate thrust, overcome the atmospheric resistance encountered by the aircraft, and thus achieve long-term flight.

[0018] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0020] Figure 1 A schematic diagram of the three-dimensional structure of an air-breathing aircraft for long-term flight in the upper atmosphere according to a first embodiment of the present invention is shown.

[0021] Figure 2 A schematic diagram of a central longitudinal section of an air-breathing aircraft for long-term flight in the upper atmosphere according to a first embodiment of the present invention is shown.

[0022] Figure 3 A schematic cross-sectional diagram of an aircraft body and an air inlet of an air-breathing aircraft for long-term flight in the upper atmosphere according to a first embodiment of the present invention is shown.

[0023] Figure 4 A schematic diagram of a central longitudinal section of an air-breathing aircraft for long-term flight in the upper atmosphere according to a second embodiment of the present invention is shown.

[0024] Figure 5 A schematic diagram of a central longitudinal section of an air-breathing aircraft for long-term flight in the upper atmosphere according to a third embodiment of the present invention is shown.

[0025] Description of reference numerals:

[0026] 1. Aircraft body; 2. Air inlet; 3. Solar cell wing; 4. Gradual conical inlet duct; 5. Inward concave gradual compression duct; 6. Cylindrical ionization acceleration duct; 7. Gradual divergent conical outlet duct. DETAILED DESCRIPTION

[0027] The preferred embodiments of the present invention will be described in more detail below. Although the preferred embodiments of the present invention are described below, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0028] Example 1

[0029] like Figures 1 to 3 As shown, the present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere, comprising:

[0030] The aircraft body 1 has an air-breathing electric propulsion system. The outer contour of the aircraft body 1 is cylindrical. An air inlet 2 is provided at the center of the aircraft body 1. The air inlet 2 includes, from front to back, a tapered inlet duct 4, an inwardly concave tapered compression duct 5, a cylindrical ionization acceleration duct 6, and a gradually diverging tapered outlet duct 7.

[0031] The solar cell wing 3 is arranged on the outside of the aircraft body 1. The solar cell wing 3 is a forward-swept trapezoidal wing. The solar cell wing 3 can provide power for the air-breathing electric propulsion system.

[0032] Specifically, in order to solve the problem of technical defects in the aerodynamic shape design of aircraft for long-term flight in the upper atmosphere in the prior art, the present invention provides an air-breathing aircraft for long-term flight in the upper atmosphere. The aircraft body has an air-breathing electric propulsion system. Based on the aerodynamic characteristics of the upper atmosphere, and considering that the thin atmosphere in the upper atmosphere will produce resistance, which makes it difficult for the aircraft to fly for a long time, the air-breathing electric propulsion system is used to generate thrust to overcome the resistance produced by the thin atmosphere. At the same time, solar cell wings are provided on the outside of the aircraft body. The electric energy of the air-breathing electric propulsion system is provided by the solar cell wings to meet the energy supply demand. The aircraft body can carry a payload, and the air inlet of the air-breathing electric propulsion system is located at The center of the aircraft body is a through-hole structure. The gas enters the air inlet through a tapered inlet pipe, is compressed in an inward-concave tapered compression pipe, and then is ionized and accelerated in a cylindrical ionization acceleration pipe. Finally, it is discharged through a gradually expanding tapered outlet pipe to generate thrust. The solar cell wing adopts a forward-swept trapezoidal wing. The existence of the forward sweep angle and the increase in the cone angle with the tapered tapered inlet pipe increase the effective inlet size of the air inlet, which is conducive to the high-speed and low-density upper atmosphere entering the air inlet, thereby improving the gas collection performance of the air inlet. After the air inlet collects and compresses the low-density upper atmosphere, the air-breathing electric propulsion system ionizes and accelerates it through the electrical energy provided by the solar cell wing to generate thrust, overcome the atmospheric resistance encountered by the aircraft, and thus achieve long-term flight.

[0033] In this embodiment, the solar cell wing 3 is a right-angled trapezoid with a forward sweep angle.

[0034] Aiming at the demand for long-term flight in the upper atmosphere, the present invention proposes an air-breathing aircraft for long-term flight in the upper atmosphere from the perspective of integrated aerodynamic and propulsion design. The outer contour of the aircraft body 1 is cylindrical, and the length and diameter of the aircraft body 1 can be determined according to engineering needs.

[0035] In this embodiment, the air-breathing vehicle for long-term flight in the upper atmosphere is suitable for an upper atmospheric altitude range of 100 km to 300 km, and a flight speed in the suborbital speed range, i.e., about 7760 m / s.

[0036] Optionally, the front end radius of the tapered inlet duct 4 is equal to the outer contour radius of the aircraft body 1 .

[0037] Specifically, the front end of the tapered conical inlet pipe 4 gradually tapers from the outermost periphery of the aircraft body 1, so that the front end radius of the tapered conical inlet pipe 4 can reach a maximum value, that is, equal to the radius of the aircraft body 1, which can not only maximize the size of the gas inlet, but also better ensure the strength and rigidity of the front end of the aircraft body 1 compared to the cylindrical inlet pipe.

[0038] The length of the tapered inlet duct 4 can be determined according to the size of the aircraft.

[0039] In this embodiment, the diameter D of the aircraft body 1 of the air-breathing aircraft for long-term flight in the upper atmosphere is 1.5 m, so the front end radius R of the tapered inlet duct 4 is b is 0.75m, the root chord length a of the solar cell wing 3 is 2m, and the length of the tapered inlet pipe 4 is L i and rear end radius R i 0.2 m and 0.55 m respectively.

[0040] Optionally, the taper angle of the tapered inlet duct 4 differs from the sweep angle of the forward-swept trapezoidal wing by -10° to 10°.

[0041] Specifically, the cone angle of the tapered inlet pipe 4 is matched with the forward sweep angle of the forward swept trapezoidal wing, and the difference between the two is small, forming a relatively smooth angle transition, which can increase the effective inlet size of the air inlet 2, and is conducive to the high-speed and low-density upper atmosphere entering the air inlet 2, thereby improving the gas collection performance of the air inlet 2.

[0042] Optionally, the cross-sectional profile of the inwardly concave tapered compression pipe 5 is arc-shaped, and the front end radius of the inwardly concave tapered compression pipe 5 is equal to the rear end radius of the tapered conical inlet pipe 4 .

[0043] Specifically, the arc-shaped pipe cross-sectional profile can improve the compression performance and collection performance of the air inlet duct 2 , and the front end of the concave tapered compression pipe 5 is connected to the rear end of the tapered inlet pipe 4 in a broken line shape.

[0044] The length of the concave tapered compression duct 5 can be determined according to the flight altitude and the size of the aircraft.

[0045] In this embodiment, the flight altitude of the air-breathing aircraft for long-term flight in the upper atmosphere is 180 km, and the length L of the concave tapered compression pipe 5 is c and rear end radius R e 0.88 m and 0.32 m respectively.

[0046] Optionally, the radius of the cylindrical ionization acceleration pipe 6 is 25% to 75% of the radius of the rear end of the tapered inlet pipe 4 .

[0047] Specifically, the cylindrical ionization acceleration duct 6 adopts a larger radius, which can eliminate the large-scale backflow of the concave tapered compression duct 5, which is conducive to the gas entering the cylindrical ionization acceleration duct 6 through the concave tapered compression duct 5, thereby improving the gas collection performance of the inlet duct 2.

[0048] The length of the cylindrical ionization acceleration tube 6 can be determined according to the size of the aircraft.

[0049] In this embodiment, the length L of the cylindrical ionization acceleration tube 6 is e is 0.5 m.

[0050] Optionally, the radius of the front end of the gradually diverging conical outlet pipe 7 is equal to the radius of the cylindrical ionization acceleration pipe 6 .

[0051] Specifically, the length of the gradually diverging tapered outlet pipe 7 can be determined according to the size of the aircraft.

[0052] In this embodiment, the length L of the gradually expanding conical outlet pipe 7 is o and rear end radius R o 0.1 m and 0.36 m respectively.

[0053] Optionally, the front end of the root of the swept-forward trapezoidal wing is flush with the front end of the aircraft body 1 .

[0054] Specifically, while the cone angle of the tapered conical inlet duct 4 is coordinated with the forward sweep angle of the forward-swept trapezoidal wing, the front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body 1, so that the leading edge of the forward-swept trapezoidal wing and the tapered conical inlet duct 4 form a relatively smooth transition connection, which is conducive to improving the performance of collecting the atmosphere.

[0055] Optionally, the rear end of the root of the swept-forward trapezoidal wing extends out of the rear end of the aircraft body 1 .

[0056] Specifically, the chord-wise length of the root of the forward-swept trapezoidal wing is greater than the length of the aircraft body 1, and the rear end of the root of the forward-swept trapezoidal wing extends backward to the outside of the rear end of the aircraft body 1, so that the center of mass of the entire aircraft is located behind the center of pressure, thereby improving the pitch and yaw static stability of the aircraft.

[0057] In this embodiment, the length L of the aircraft body 1 is 1.683 m.

[0058] Optionally, a pair of solar cell wings 3 are symmetrically arranged on the outside of the aircraft body 1 .

[0059] The chord-wise length of the root of the solar cell wing 3 and the chord-wise length and span-wise length at the wingtip position can be determined according to the flight altitude and the size of the aircraft.

[0060] In this embodiment, two solar cell wings 3 are provided, which are symmetrically arranged on both sides of the aircraft body 1; the chord length b of the solar cell wings 3 at the wingtip position is 4m, and the span w is 4m.

[0061] Optionally, the forward-swept trapezoidal wing is a flat plate structure, and the thickness of the forward-swept trapezoidal wing is 20 mm to 40 mm.

[0062] Specifically, in order to reduce aerodynamic resistance, while ensuring structural strength, the thickness of the solar cell wing 3 is as small as possible, and can be 20 mm to 40 mm.

[0063] The air-breathing aircraft for long-term flight in the upper atmosphere needs to meet the following two conditions for long-term flight in the upper atmosphere:

[0064] 1) From the perspective of force balance, the thrust generated by the propulsion system can overcome aerodynamic drag, that is, the balance between thrust and drag (thrust-drag balance) is achieved;

[0065] 2) From the perspective of energy balance, the electrical energy provided by the solar cell wing 3 is sufficient to supply the propulsion system, that is, the thrust-to-power ratio (thrust-to-power ratio) of the propulsion system is within the normal range.

[0066] To evaluate the feasibility of the air-breathing aircraft for long-term flight in the upper atmosphere in this embodiment, the atmospheric environment at an altitude of 180 km was used as an example to simulate the internal and external flows of the air-breathing aircraft for long-term flight in the upper atmosphere using the direct simulation Monte Carlo (DSMC) method to obtain the gas pressure distribution, gas mass flow rate, and aerodynamic drag. The gas-solid interaction model was a Maxwell model with an adaptation coefficient of 0.5. The volume fraction of nitrogen molecules in the incoming flow was 0.4829, the volume fraction of oxygen atoms was 0.4820, and the volume fraction of oxygen molecules was 0.0351. The specific incoming flow parameters were as follows: velocity u ∞ is 7760m / s, angle of attack α is 0°, temperature T ∞ is 790.07K, density ρ ∞ 5.198*10 -10 kg / m 3 .

[0067] The average gas pressure in the cylindrical ionization acceleration pipe 6 of the air-breathing electric propulsion system given by DSMC simulation is 0.0232 Pa, and the gas mass flow rate through the pipe is m fr = 2.07 × 10 -6 kg / s. The total drag experienced by the air-breathing aircraft for long-term flight in the upper atmosphere, including the drag of the aircraft body 1, the flow resistance in the inlet duct 2, and the drag of the solar cell wing 3, is F = 80.51 mN. The average pressure of the gas in the cylindrical ionization acceleration duct 6 is much higher than the pressure threshold of 0.005 Pa for gas ionization, ensuring a high gas ionization efficiency. In order to estimate the thrust, it is assumed that the ionization efficiency or working fluid utilization rate is η = 72.27%, neutral gas is ionized and accelerated to v out = 40 km / s exhaust. Thus, the thrust generated by the air-breathing electric propulsion system T for:

[0068] .

[0069] Substituting the ionization efficiency, mass flow rate, and exhaust velocity, the thrust can be obtained as: T = 80.51 mN.

[0070] Therefore, the thrust generated by the air-breathing electric propulsion system is exactly equal to the total resistance experienced by the aircraft, achieving thrust-drag balance.

[0071] Next, we will evaluate whether the thrust-to-power ratio of the air-breathing electric propulsion system is within the normal range. In this embodiment, the area of ​​the solar cell wing 3 is 24 m 2 The energy density of the battery wing is 150 W / m 2 , so the spacecraft receives 3.6kW of solar power, and the thrust-to-power ratio of the air-breathing electric propulsion system is 22.36 mN / kW. Currently, the thrust-to-power ratio of air-breathing electric propulsion systems can reach 30mN / kW, so the thrust-to-power ratio of this scheme is within the normal range.

[0072] Based on the above evaluation of the average gas pressure, thrust-drag balance and thrust-to-power ratio of the air-breathing electric propulsion system, the following conclusions are drawn: the air-breathing aircraft used for long-term flight in the upper atmosphere in this embodiment achieves thrust-drag balance under the condition of limited energy supply, that is, the thrust generated by the electric energy supplied by the air-breathing electric propulsion system through the solar cell wing 3 can just overcome the aerodynamic resistance of the entire aircraft, thereby realizing long-term flight of the aircraft in the upper atmosphere, and further promoting the development and utilization of this airspace in the upper atmosphere.

[0073] Example 2 and Example 3

[0074] like Figure 4 and Figure 5 The figures show the dimensions of the solar cell wing 3 in the second and third embodiments respectively, when the dimensions of the aircraft body 1 are the same as those in the first embodiment. In the second embodiment, the root chord length a of the solar cell wing 3 is 2m, the chord length b at the wingtip is 4m, and the span w is 3m. In the third embodiment, the root chord length a of the solar cell wing 3 is 2.5m, the chord length b at the wingtip is 4.5m, and the span w is 4m. The area of ​​the solar cell wing 3 in the second embodiment is 18m 2 The energy density of the battery wing is 150 W / m 2, so the solar power obtained by the aircraft is 2.7kW, the thrust-to-power ratio of the air-breathing electric propulsion system is 26.74 mN / kW, the ionization efficiency is 64.87%, and the total drag on the aircraft is 72.21mN. The area of ​​the solar cell wing 3 in Example 3 is 28 m 2 The energy density of the battery wing is 150 W / m 2 , so the aircraft receives 4.2kW ​​of solar power, the thrust-to-power ratio of the air-breathing electric propulsion system is 20 mN / kW, the ionization efficiency is 75.39%, and the total drag on the aircraft is 83.99mN. By comparison, if the air-breathing electric propulsion system has a low ionization efficiency, a smaller solar wing 3 can be used, resulting in higher thrust-to-power. If the propulsion system has a high ionization efficiency, a larger solar wing 3 can be used, resulting in lower thrust-to-power.

[0075] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. An air-breathing aircraft for long-term flight in the upper atmosphere, characterized in that include: An aircraft body, the aircraft body having an air-breathing electric propulsion system, the aircraft body having a cylindrical outer contour, an air inlet duct disposed at the center of the aircraft body, the air inlet duct comprising, arranged in sequence from front to back, a tapered inlet duct, an inwardly concave tapered compression duct, a cylindrical ionization acceleration duct, and a gradually diverging tapered outlet duct; a solar cell wing, the solar cell wing being arranged on the outside of the aircraft body, the solar cell wing being a forward-swept trapezoidal wing, and the solar cell wing being capable of supplying power to the air-breathing electric propulsion system; The front end radius of the tapered inlet duct is equal to the outer contour radius of the aircraft body; The front end of the root of the forward-swept trapezoidal wing is flush with the front end of the aircraft body, and the taper angle of the tapered inlet duct differs from the forward sweep angle of the forward-swept trapezoidal wing by -10° to 10°; The radius of the cylindrical ionization acceleration pipe is 25% to 75% of the radius of the rear end of the tapered inlet pipe; The rear end of the root of the forward-swept trapezoidal wing extends out of the rear end of the aircraft body.

2. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that: The cross-sectional profile of the inwardly concave tapered compression pipe is in the shape of an arc, and the front end radius of the inwardly concave tapered compression pipe is equal to the rear end radius of the tapered conical inlet pipe.

3. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that: The radius of the front end of the gradually diverging conical outlet pipe is equal to the radius of the cylindrical ionization acceleration pipe.

4. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that: A pair of solar cell wings are symmetrically arranged on the outside of the aircraft body.

5. The air-breathing aircraft for long-term flight in the upper atmosphere according to claim 1, characterized in that: The forward-swept trapezoidal wing is a flat plate structure, and the thickness of the forward-swept trapezoidal wing is 20 mm to 40 mm.

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