Radioisotope micro-thruster based on directional radiation

Abstract

The invention discloses a radioactive isotope micro-thruster based on directional radiation. The thruster comprises a radioactive isotope source, a particle orientation system, a radiation shielding shell and a power management system, the radioactive isotope source decays to generate charged particles, the particle orientation system restrains the particle emission direction in the dominant direction, the radiation shielding shell shields harmful radiation, and the power management system supplies power to the orientation system. During working, the power management system is activated and supplies power, the particle orientation system establishes a constraint field, particles generated by isotope source decay are directionally jetted under the action of the constraint field, and the thruster obtains reverse continuous micro-cattle magnitude thrust according to momentum conservation. The invention solves the problems of difficult thrust control, working medium demand, short service life and the like of the traditional propulsion technology, is suitable for tasks of deep space exploration, satellite drag-free control and the like, and has the advantages of stable thrust, long service life, no working medium and high reliability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aerospace propulsion, and in particular to a radioactive isotope microthruster based on directional radiation. BACKGROUND

[0002] With the continuous expansion of space exploration tasks to high precision, long period, complex environment, such as gravitational wave detection (typical as LISA project), deep space micro celestial body accurate detection and ultra-high precision earth observation, etc. Frontier tasks, the performance of the spacecraft propulsion system is put forward strict and multiple requirements: first, the thrust output needs to be stably controlled in the micro-newton (μN) or even nanonewton (nN) level to adapt to the high-precision operation requirements such as attitude fine adjustment and drag-free control; second, the working life needs to cover several years to several decades to meet the energy and thrust continuous supply requirements of long-period tasks such as deep space exploration; third, the vibration and noise need to be reduced to a very low level to avoid interfering with the normal work of precision loads (such as gravitational wave detectors and high-resolution imaging equipment).

[0003] However, the current mainstream propulsion technology is difficult to meet the above core requirements at the same time. On the one hand, although the traditional chemical propulsion system can provide a larger thrust, the thrust level is far beyond the micro-newton / nanonewton range, and the thrust regulation precision is low, which cannot adapt to the high-precision control scene; on the other hand, although the conventional electric propulsion system such as ion thruster has higher specific impulse advantage, its operation depends on the carrying and consumption of working medium, which not only limits the task life, but also needs to be matched with a complex power processing unit to maintain ion acceleration and beam control, and the particle plume is easy to pollute the spacecraft surface and the surrounding precision components, affecting the task reliability.

[0004] In the exploration of new propulsion technology, the decay characteristics of radioactive isotopes show unique potential: during the decay process of radioactive isotopes, charged particles such as alpha particles and beta particles are ejected at a very high speed, and each particle carries momentum. According to the principle of conservation of momentum, if these randomly emitted particles can be directionally constrained to a single direction, they can be converted into continuous micro-thrust; otherwise, the momentum of particles in each direction cancels out, and the net thrust is zero. In the prior art, although a scheme of realizing particle half-space emission through an "absorber" has appeared (i.e. by blocking particles in one direction through an absorber and allowing particles to escape in the other direction), the theoretical maximum efficiency of this scheme is only 50%, and a large amount of particle energy is lost by the absorber, which cannot realize high-efficiency thrust output. Therefore, it is an urgent need in the current aerospace propulsion field to develop a new type of propulsion technology that can break through the bottleneck of existing technology, realize high-efficiency directional radiation of particles, and thus produce better thrust performance. SUMMARY

[0005] The present application uses a specific particle orientation system (such as a metamaterial structure or an asymmetric electromagnetic field) to constrain the emission direction of charged particles (such as alpha or beta particles) generated in the radioactive isotope decay process in a dominant direction, thereby generating a sustained, stable micro-newton level thrust using the recoil effect of the particles. The present application solves the deficiencies of traditional chemical propulsion and electric propulsion in extremely small thrust, long life, high reliability missions, and is particularly suitable for space exploration, satellite drag-free control, and high-precision attitude maintenance.

[0006] The present application provides a radioactive isotope micro-thruster based on directional radiation, comprising: A radioactive isotope micro-thruster based on directional radiation, comprising: A radioactive isotope source configured to generate charged particles through decay; A particle orientation system configured as a metamaterial orientation device or an asymmetric electric field orientation device to constrain the emission direction of the charged particles; A radiation shielding shell surrounding the periphery of the radioactive isotope source and particle orientation system; and A power management system configured to power the particle orientation system.

[0007] In an embodiment of the present application, a thruster mounting base is further included for fixing the thruster on a spacecraft.

[0008] In an embodiment of the present application, when the particle orientation system is a metamaterial orientation device, it comprises: A substrate configured to carry the radioactive isotope source; A metamaterial structure with a lattice constant matching the de Broglie wavelength of a specific energy charged particle; and A particle orientation emission channel configured to be set in a specific channel of the metamaterial structure to allow the charged particles to propagate and escape in this direction.

[0009] In an embodiment of the present application, a thin film radioactive isotope source is attached to the substrate, with a thickness of 1-5 μm to maximize the probability of the charged particles escaping in a single direction.

[0010] In an embodiment of the present application, the substrate is configured to dissipate the heat generated by decay and block the penetration of charged particles in the direction of the substrate.

[0011] In an embodiment of the present application, when the particle orientation system is an asymmetric electric field orientation device, it comprises: A set of asymmetrically arranged electrodes configured to generate a static or dynamic asymmetric electric field, causing the charged particles generated in the radioactive isotope source to be preferentially accelerated and directed to a predetermined exit channel under the action of the electric field force. The electrode comprises: a repelling electrode located on one side of the radioisotope source for repelling homopolar particles; and an accelerating ground electrode located on the other side of the radioisotope source, with a circular nozzle in the center for attracting the charged particles and providing a concentrated jet channel for the charged particles through the circular nozzle while accelerating the charged particles.

[0012] In an embodiment of the present application, the radioisotope source is an alpha radiation source, including polonium-210, plutonium-238 or americium-241; or the radioisotope source is a beta radiation source, including strontium-90 or krypton-85.

[0013] In an embodiment of the present application, the radiation shielding shell is made of lead or tungsten.

[0014] The present application also provides a method for generating thrust by the thruster as described above, characterized in that it comprises: providing operating voltage for the particle directing system by the power management system; continuously decaying by the radioisotope source to generate charged particles; establishing a directed confinement field around the radioisotope source by the particle directing system, so that the momentum of the charged particles is directed to a specific direction under the action of the directed confinement field; and obtaining recoil momentum opposite to the specific direction by the thruster body to generate continuous thrust.

[0015] The present application also provides a spacecraft with the radioisotope micro-thruster as described above.

[0016] The present application has the following beneficial effects: (1) The thrust size is directly determined by the decay rate of the isotope, which is very stable and almost noiseless, as the decay rate is determined by physical laws.

[0017] (2) The service life depends on the half-life of the isotope, which can be up to several decades (such as the half-life of Pu-238 is 87.7 years).

[0018] (3) The thrust comes from nuclear decay itself, without carrying and consuming traditional working medium.

[0019] (4) Since the particle jet speed is close to the speed of light (especially for beta particles), the theoretical specific impulse is extremely high.

[0020] (5) By changing the electric field strength of the directing system, the thrust can be fine-tuned within a certain range.

[0021] (6) The structure is simple, the reliability is high, there is no moving part, and the system is solid and durable. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A schematic diagram of the overall structure of a radioactive isotope micro-thruster based on directional radiation is shown in one embodiment of the present invention; Figure 2 A schematic diagram of a metamaterial directional device structure according to an embodiment of the present invention is shown; and Figure 3 A schematic diagram of an asymmetric electric field directional device structure is shown in one embodiment of the present invention. Detailed Implementation

[0023] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details.

[0024] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0025] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0026] Furthermore, the numbering of the steps in the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps may be executed in different orders.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 1 A schematic diagram of the overall structure of a radioactive isotope micro-thruster based on directional radiation is shown in one embodiment of the present invention.

[0029] Figure 2 A schematic diagram of a metamaterial directional device structure is shown in one embodiment of the present invention.

[0030] like Figure 1 and Figure 2 As shown, in this embodiment, the particle orientation system 200 is a metamaterial orientation device 210, and the thruster structure includes: The radioactive isotope source 100, as a "charged particle source head" of the thruster, generates energy-stable alpha particles or beta particles through nuclear decay, provides momentum carriers that can be constrained by "energy band regulation" for the metamaterial directional system, and is the basis for forming a directional particle beam and generating thrust.

[0031] In the embodiment, the radioactive isotope source 100 needs to be prepared in an extremely thin film form, and the thickness needs to be controlled in the micron level (such as 1-5 μm). This form can maximize the reduction of particle emission loss in the direction of the substrate, so that the particles preferentially move to the side of the metamaterial.

[0032] In the embodiment, alpha radioactive sources such as plutonium-238, polonium-210, and americium-241 are preferentially selected. The alpha particles generated by the decay of the alpha radioactive sources have concentrated energy (such as 5.5 MeV alpha particles generated by plutonium-238), large mass, and stable momentum, and are more easily matched with the lattice constant and energy band structure of the metamaterial to achieve efficient orientation.

[0033] If a beta radioactive source (such as strontium-90) is selected, the lattice parameters of the metamaterial need to be adjusted to match the de Broglie wavelength of the beta particles (high-energy electrons) to ensure the directional effect.

[0034] The metamaterial directional device 210, through the periodic physical structure designed artificially, uses the "energy band regulation" principle to prohibit the particles generated by the radioactive isotope source from propagating in most directions, and only allows the particles to escape along a preset single or few "guided mode" channels, thereby achieving efficient directional emission of the particles and being a key module for generating net thrust. It mainly includes: The substrate 211. The thin film needs to be closely attached to a high-thermal-conductivity and radiation-resistant substrate 211, such as a silicon carbide or tungsten alloy substrate. The substrate 211 provides support for the isotope thin film and can also timely conduct the heat generated by the decay to avoid high temperature affecting the stability of the metamaterial structure 212. Meanwhile, the substrate blocks the particles from penetrating in the direction of the substrate, and forces the particles to emit only to the side of the metamaterial.

[0035] The metamaterial structure 212 adopts a photonic crystal or plasmonic metamaterial structure, which is a periodically arrayed (such as a nanoscale columnar array or a hole array) structure. The lattice constant of the array needs to be accurately matched with the de Broglie wavelength of the target particles (such as 5.5 MeV alpha particles). A single-direction guided mode channel, such as a linear channel along the thrust direction of the thruster, is preset in the metamaterial structure 212. The channel width is adapted to the particle diameter, and the defect structure (such as local lattice parameter fine-tuning) of the array is adjusted to strengthen the "guiding effect" of the channel on the particles, thereby ensuring the efficient escape of the particles along the channel.

[0036] Taking a plutonium-238 alpha source as an example, a 5.5 MeV alpha particle is generated by the decay of a plutonium-238 thin film, and the particle initially moves randomly in all directions. When the particle attempts to propagate in a non-guided mode direction, the periodic lattice structure of the metamaterial forms a "band gap" in that direction, i.e. the energy state of that direction is prohibited, and the particle cannot obtain the energy required for propagation, and the movement is blocked. Only when the particle moves along the preset guided mode channel direction, the energy band structure of the metamaterial allows the particle to propagate (the guided mode state is activated), and the particle moves unhindered in the channel, and finally escapes from the specific outlet of the metamaterial to form a highly directional alpha particle beam.

[0037] The metamaterial directional device 210 does not need additional electrical energy to drive the directional function, and only needs to be powered by a matching monitoring sensor, greatly reducing the power consumption of the thruster, and adapting to the limited energy supply of the spacecraft in orbit.

[0038] The power management system 300 does not directly power the metamaterial directional device 210 in this embodiment (the metamaterial works passively), mainly provides stable electrical energy for the state monitoring system of the thruster, and at the same time guarantees the safety and reliability of the overall circuit, which is a monitoring energy guarantee module of the thruster.

[0039] The radiation shielding shell 400, as a radiation safety barrier, fully shields harmful radiation (such as unoriented alpha particles and secondary rays) generated by the decay of the radioactive isotope source (thin film form), protects other precise components (such as attitude sensors and data processing units) of the spacecraft, and at the same time avoids radiation interference with the lattice structure stability of the metamaterial. The radiation shielding shell 400 is made of high-density heavy metals such as lead and tungsten, and efficiently blocks the penetration of alpha particles relying on its high-density characteristics. The combination of the radioactive isotope source 100 and the particle directional system 200 is completely wrapped in a shell shape, and the inner side of the shell needs to be closely attached to the metamaterial structure to reduce the gap to avoid radiation leakage after scattering in the gap. At the same time, the shell needs to reserve a hole for the sensor line to pass through, and the hole needs to be equipped with a lead sealing plug to ensure that there is no radiation leakage.

[0040] The thruster mounting base 500, as a rigid connection interface between the thruster and the spacecraft, realizes the stable fixation of the thruster, ensures that the directional particle beam recoil thrust generated by the metamaterial directional device can be efficiently and losslessly transmitted to the spacecraft, and at the same time avoids displacement of the thruster during launch or in-orbit operation, which affects the particle directional accuracy.

[0041] Figure 3 An asymmetric electric field directional device structure schematic diagram in an embodiment of the present application is shown.

[0042] In another embodiment of the present application, the particle directional system 200 is an asymmetric electric field directional device 220, as shown in Figure 3 The asymmetric electric field directional device 220 includes: The suppression electrode 221 is located on one side of the radioisotope source 100 and is made of a high-voltage-resistant metal material such as 316L stainless steel, and is designed in a circular or square plate shape and needs to be kept at a fixed distance (such as 5-10 mm) from the source body. A high negative potential is applied in the working example, which is -50 kV, for repelling particles of the same polarity, such as positively charged alpha particles, which are repelled by the negative electrode.

[0043] The acceleration electrode 222 is located on the other side of the source body and is made of the same material as the suppression electrode 221, and a circular nozzle is provided in the center, the diameter of the nozzle is designed according to the particle beam intensity, such as 1-3 mm, and the working potential is kept at ground potential. Its role is to attract charged particles and provide a concentrated jet channel for the particles through the nozzle, while forming an acceleration effect on the particles.

[0044] Compared with the previous embodiment, in this embodiment, the radioisotope source 100 is in a block or point shape, rather than a thin film shape in the metamaterial director. This shape does not need to be attached to the substrate and can be directly placed in the center of the cavity of the asymmetric electric field director, which can maximize the use of the omnidirectional coverage characteristics of the electric field. No matter which direction the particle is initially emitted, it can be captured and directed to the preset direction by the asymmetric electric field, avoiding the limitation of the particle emission direction by the thin film shape and improving the particle utilization rate.

[0045] In this embodiment, the power management system 300 provides stable and adjustable high-voltage power for the asymmetric electric field director, and also powers the radiation monitoring and particle beam intensity monitoring sensors, which is the energy control center that ensures the stability of the electric field and the controllability of the thrust.

[0046] Based on the above embodiments, the overall working process of the radioisotope micro-thruster based on directional radiation is as follows: First, activate the power management system of the thruster, provide appropriate working power according to the type of particle directing system (metamaterial director or asymmetric electric field director), if it is an asymmetric electric field director, it needs to provide high voltage for the electrode; if it is a metamaterial director, although it does not need to power the directing structure, it needs to provide stable low voltage for the matching monitoring sensor (such as the particle beam intensity sensor) to ensure that the system status can be monitored.

[0047] Based on the particle directing system, a stable directional confinement field is established around the radioisotope source. The metamaterial director forms a band gap and a guide mode channel through its periodic lattice structure to construct a physical confinement field. The asymmetric electric field director forms a highly asymmetric electric field confinement field through the potential difference between the electrodes, laying the foundation for particle direction.

[0048] The radioisotope source continuously undergoes nuclear decay under the protection of the radiation shielding shell, stably generating alpha particles or beta particles. The momentum carried by these charged particles is the core material carrier for subsequent thrust generation.

[0049] The charged particles generated by the decay move randomly in all directions, and after entering the directional confinement field, the momentum is oriented by the action of the confinement field: the super material orienter blocks the particles in the non-guided mode direction by the band gap, and only allows the particles to move along the guided mode channel; the asymmetric electric field orienter drives the particles to converge to the preset nozzle direction by the electric field force, and finally makes the particle momentum uniformly direct to a single dominant direction.

[0050] According to the law of conservation of momentum, when the oriented particle beam is ejected along the dominant direction, it will generate a reverse recoil momentum to the thruster body, which is converted into a continuous and stable micro-newton level thrust, and is transmitted to the spacecraft through the thruster mounting base, meeting the spacecraft attitude maintenance, drag-free control and other mission requirements.

[0051] Although the embodiments of the present application are described above, it should be understood that they are presented only as examples, not as limitations. It is obvious to those skilled in the relevant art that various combinations, modifications and changes can be made without departing from the spirit and scope of the present application. Therefore, the width and scope of the present application disclosed herein should not be limited by the above disclosed exemplary embodiments, but should only be defined according to the appended claims and their equivalent replacements.

Claims

1. A radioactive isotope micro-thruster based on directional radiation, characterized in that, include: A radioactive isotope source configured to produce charged particles through decay; A particle orientation system, configured as a metamaterial or asymmetric electric field orientation system, to constrain the emission direction of the charged particles; A radiation shielding shell surrounds the radioactive isotope source and the particle orientation system. as well as A power management system configured to supply power to the particle orientation system.

2. The radioactive isotope micro-thruster according to claim 1, characterized in that, It also includes a thruster mounting base for securing the thruster to the spacecraft.

3. The radioactive isotope micro-thruster according to claim 1, characterized in that, When the particle orientation system is a metamaterial orientation device, it includes: A substrate configured to support a source of radioactive isotopes; Metamaterial structures whose lattice constant matches the de Broglie wavelength of charged particles at specific energies; and A particle-directed emission channel is configured to be placed in a specific channel within a metamaterial structure to allow charged particles to propagate and escape along this direction.

4. The radioactive isotope micro-thruster according to claim 3, characterized in that, A thin-film radioactive isotope source with a thickness of 1-5 μm is attached to the substrate to maximize the probability of charged particles escaping in one direction.

5. The radioactive isotope micro-thruster according to claim 3, characterized in that, The substrate is configured to dissipate the heat generated by decay and to block charged particles from penetrating toward the substrate.

6. The radioactive isotope micro-thruster according to claim 1, characterized in that, When the particle orientation system is an asymmetric electric field orientation device, it includes: A set of asymmetrically arranged electrodes is configured to generate a static or dynamic asymmetric electric field, which causes charged particles generated in the radioactive isotope source to be preferentially accelerated and directed toward a predetermined exit channel under the action of the electric field force. The electrode includes: A suppression electrode, located on one side of the radioactive isotope source, is used to repel particles of the same polarity; and The accelerating grounding electrode is located on the other side of the radioactive isotope source. A circular nozzle is opened in the center of the electrode to attract charged particles and provide a concentrated jet channel for the charged particles through the circular nozzle, thereby accelerating the charged particles.

7. The radioactive isotope micro-thruster according to claim 1, characterized in that, The radioactive isotope source is an alpha radioactive source, including polonium-210, plutonium-238, or americium-241; or The radioactive isotope source is a β-radioactive source, including strontium-90 or krypton-85.

8. The radioactive isotope micro-thruster according to claim 1, characterized in that, The radiation shielding shell is made of lead or tungsten.

9. A method for generating thrust using a thruster according to any one of claims 1-8, characterized in that, include: The power management system provides the operating voltage for the particle orientation system; The continuous decay of a radioactive isotope source produces charged particles. The particle orientation system establishes a directional constraint field around the radioactive isotope source, causing the momentum of the charged particles to be guided in a specific direction under the influence of the directional constraint field; and The thruster body obtains a counter-force in the opposite direction to the specified direction to generate continuous thrust.

10. A spacecraft having a radioisotope microthruster according to any one of claims 1 to 8.

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