Thrust generating device, spacecraft

Abstract

A thrust generating device according to the present invention is for generating thrust in an object by irradiating the object with a laser, the thrust generating device comprising: a laser generating device that generates first laser light of a first wavelength and second laser light of a second wavelength different from the first wavelength; and an irradiation device that irradiates the object with the first laser light and the second laser light at the same time. The second wavelength may be a wavelength for which the object has a higher absorptivity than the first wavelength, and the intensity of the second laser light may be weaker than the intensity of the first laser light. Also, the second laser light may be generated by wavelength conversion of the first laser light.

Description

[Technical Field]

[0001] The present invention relates to a thrust generating device that generates thrust on an object by irradiating the object with a laser to cause ablation, and to a spacecraft having such a thrust generating device. [Background technology]

[0002] In recent years, the increase in debris (space junk) in outer space has become a problem. Debris refers to satellites that are no longer needed or have malfunctioned, or parts of satellites that have been released due to collisions or other reasons. Debris poses a risk of colliding with operational satellites, and even debris measuring just a few centimeters in size can cause catastrophic damage to the satellite. There are also concerns about the Kessler syndrome, a problem in which debris increases explosively as it collides with satellites. To prevent the increase in debris, it is necessary to either incinerate the debris by re-entering the atmosphere or move it to an orbit (graveyard orbit) where it will not collide with other satellites.

[0003] The applicants of the present application have proposed a technology in which debris is irradiated with a laser and the orbit or attitude of the debris is controlled by the thrust generated by the laser irradiation (Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2020 / 152744 [Non-patent literature]

[0005] [Non-Patent Document 1] K. Sugioka, S. Wada, A. Tsunemi, T. Sakai, H. Takai, H. Moriwaki, A. Nakamura, H. Tashiro, K. Toyoda: “Micropatterning of Quartz Substrates by Multi-wavelength Vacuum-Ultraviolet Laser Ablation” Jpn. J. Appl. Phys., 32, 6185-6189 (1993). [Non-Patent Document 2] K. Sugioka, S. Wada, Y. Ohnuma, A. Nakamura, H. Tashiro, K. Toyoda: “Multiwavelength irradiation effect in fused quartz ablation using vacuum-ultraviolet Raman laser” Appl. Surf. Sci., 96-98, 347-351 (1996). [Non-Patent Document 3] J. Zhang, K. Sugioka, S. Wada, H. Tashiro, K. Toyoda, K. Midorikawa: “Precise microfabrication of wide band gap semiconductors (SiC and GaN) by VUV-UV multiwavelength laser ablation” Appl. Surf. Sci., 127-129, 793-799 (1998). [Summary of the Invention] [Problems to be Solved by the Invention]

[0006] In order to facilitate the control of debris, it is desirable to generate a strong thrust. Patent Document 1 proposes attaching a thrust enhancement member to debris and irradiating the thrust enhancement member with a laser to generate a stronger thrust. However, attaching a thrust enhancement member to debris is costly. Also, this method cannot be applied to existing objects.

[0007] Therefore, an object of the present invention is to provide a technique for generating a strong thrust by a simpler method than the conventional method.

Means for Solving the Problems

[0008] One aspect of the present invention is a thrust generating device for irradiating an object with a laser to generate a thrust on the object, the thrust generating device including: a laser device that generates a first laser beam having a first wavelength and a second laser beam having a second wavelength different from the first wavelength; and an irradiation device that simultaneously irradiates the object with the first laser beam and the second laser beam.

[0009] According to this aspect, the surface of the object is excited by one of the first laser beam and the second laser beam, and the absorption rate of the other laser beam is improved, so that ablation more efficient than that in the case of using a single laser beam can be generated, and thus a stronger thrust can be obtained.

[0010] For example, it is preferable that the intensity of the first laser beam is stronger than that of the second laser beam, and the absorption rate of the second laser beam (second wavelength) in the object is higher than that of the first laser beam (first wavelength). By exciting the surface of the object by irradiation with the second laser beam having a low intensity but a high absorption rate, the absorption rate of the first laser beam, which originally has a low absorption rate, becomes high, and thus ablation can be generated more efficiently than in the case of using only the first laser beam.

[0011] The laser device according to this aspect may include a laser light source that generates first laser light, and a wavelength converter that converts a part of the first laser light generated from the laser light source into second laser light. Note that the laser device according to another example may include a first laser light source that generates first laser light and a second laser light source that generates second laser light.

[0012] The laser light source is not particularly limited. For example, a solid laser or a fiber laser oscillating in the 1-μm band can be adopted. The wavelength converter may convert the wavelength (first wavelength) of the first laser light to a shorter wavelength or a longer wavelength. For example, the wavelength converter may include a nonlinear optical crystal that generates a harmonic of the first laser light to generate second laser light having a second wavelength shorter than the first wavelength. Here, the second laser light may be any harmonic (second harmonic, third harmonic, fourth harmonic, etc.) of the first laser light. Also, the wavelength converter may include an optical parametric oscillator to generate second laser light having a second wavelength longer than the first wavelength. Note that since the intensity of the second laser light does not need to be high, the wavelength conversion efficiency in the wavelength converter may be low. Therefore, there is also an advantage that the device can be simply configured without requiring high precision in adjusting the wavelength converter. Although it does not exclude the case where the wavelength conversion efficiency is high, the wavelength conversion efficiency may be 10% or less (1 / 10 or less), and further may be 0.1% (1 / 1000) or less. Such a device is easy to manufacture and is suitable for use in, for example, outer space.

[0013] Another aspect of the present invention is a spacecraft that irradiates an object with a laser in outer space to change the orbit or attitude of the object, and includes the above-described thrust generating device, wherein the irradiation device irradiates the object so that the laser generated from the laser generating device converges on the object.

Advantages of the Invention

[0014] According to the present invention, it is possible to generate a powerful thrust by a simpler method than in the prior art.

Brief Description of the Drawings

[0015]

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Mode for Carrying Out the Invention

[0016] (Embodiment) <Overview> The thrust generator according to the present embodiment is a device that generates thrust on an object by irradiating the object with a laser to generate ablation. In the present embodiment, the thrust generator is mounted on a spacecraft (artificial satellite) and is used to control the orbit or attitude of an object existing in space. By controlling the orbit or attitude of the object, for example, unnecessary objects can be removed.

[0017] The object in the present embodiment includes artifacts existing in space debris (space junk, space debris), and objects other than artifacts (for example, meteorites, etc.). Debris includes an artificial satellite that has become uncontrollable, an artificial satellite that has become unnecessary due to the end of operation, and a part of an artificial satellite released by a collision or the like. In the present embodiment, an example in which debris is the object will be described.

[0018] Orbit or attitude control refers to changing the orbit or attitude of an object (debris) existing in space. Changing the orbit means, for example, increasing or decreasing the altitude of the debris. By doing so, the debris can be made to re-enter the atmosphere and be incinerated and removed, or moved to an orbit (graveyard orbit) where it will not collide with other satellites, or the artificial satellite can be temporarily moved to avoid collisions between the debris and other objects. Changing the attitude means, for example, suppressing the rotation of the debris. This reduces the risk of collision during physical access.

[0019] In this embodiment, an example using an artificial satellite as a spacecraft will be described, but it is not limited to unmanned spacecraft, and a manned spacecraft may also be used as the spacecraft. Also, a device (sub-satellite) mounted on an artificial satellite (parent satellite) etc. may be regarded as a spacecraft. Further, the application of the thrust generating device and the type of object are not limited to those exemplified above, and for example, it may be used for any object in a ground environment.

[0020] <Debris Removal Method> FIG. 1 is a diagram showing an example of debris removal according to this embodiment. In FIG. 1, the Earth 11, the atmosphere 12 covering the Earth 11, and the orbit 13 which is an orbit around the Earth are shown. Also, the spacecraft 100 is an artificial satellite that irradiates the object with a laser. The debris 200 is an object moving in the orbit 13 at a speed v, and is, for example, an artificial satellite etc. that has become unnecessary due to the end of the operation period etc. The spacecraft 100 irradiates the debris 200 with a laser, thereby generating a velocity change Δv in the debris 200. The debris 200, due to the reaction force, for example, decreases in altitude and re-enters the atmosphere to be incinerated and removed. Note that the debris removal method is not limited to the above, and for example, the altitude of the debris 200 may be increased (or decreased) and it may be moved to an orbit (graveyard orbit) where there are no other artificial satellites.

[0021] Figure 2 is a diagram showing the thrust generated by laser irradiation. Laser 21 is the laser irradiated by spacecraft 100. When laser 21 irradiates debris 200, the material on the surface of debris 200 evaporates, becomes plasma, and ejects (plasma ablation). At this time, debris 200 receives the reaction force of the force (arrow 22) generated when the material ejects as thrust, resulting in a velocity change Δv (arrow 23).

[0022] <Configuration> Figure 3 is a diagram showing the configuration of the laser irradiation system according to this embodiment. The laser irradiation system includes spacecraft 100, monitoring device 110, etc.

[0023] ≪Spacecraft 100≫ Spacecraft 100 is an artificial satellite having a laser irradiation function. Spacecraft 100 has an acquisition unit 101, a detection unit 102, a control unit 103, a propulsion unit 104, a communication unit 105, a laser irradiation device 109, etc. Laser irradiation device 109 has a laser generation device 106, a focus unit 107, and a steering unit 108. Laser irradiation device 109 irradiates debris 200 with the laser output by laser generation device 106 via focus unit 107 and steering unit 108, and generates thrust on debris 200 due to the occurrence of ablation. Laser irradiation device 109 corresponds to a thrust generation device.

[0024] Acquisition unit 101 is a functional unit that acquires an image using an imaging unit (not shown). In addition, acquisition unit 101 acquires the reflected light of the search laser output from laser generation device 106 described later. Acquisition unit 101 can also be regarded as various sensors.

[0025] Detection unit 102 is a functional unit that acquires detection information of debris 200 based on the image or reflected light acquired by acquisition unit 101. The detection information includes the distance between spacecraft 100 and debris 200, the position, size, shape, captured image, rotation state (attitude) of debris 200, etc. For example, detection unit 102 acquires the distance between spacecraft 100 and debris 200 using Lidar (Light Detection and Ranging).

[0026] The control unit 103 (irradiation control means) controls the focus unit 107 so that the laser emitted from the laser generator 106 converges on the debris 200 based on the distance between the spacecraft 100 and the debris 200. For example, when the focus unit 107 is an optical system, the focal length of the optical system is adjusted. The control unit 103 is a functional unit that determines the irradiation position of the laser on the debris 200 and the output value of the laser based on the detection information acquired by the detection unit 102. For example, the control unit 103 determines the irradiation position of the laser based on the position and attitude of the debris 200 detected by the detection unit 102 and the area suitable for laser irradiation. The area suitable for laser irradiation is an area excluding locations where danger may occur by performing laser irradiation (for example, fuel tanks, etc.). In addition, the control unit 103 may determine the position and timing of laser irradiation in consideration of a safe area on the ground, etc. The safe area is an area for dropping fragments that remain without burning out when the debris 200 re-enters the atmosphere. For example, the safe area is a sea area tens to hundreds of nautical miles or more away from the routes of ships and aircraft and land. The control unit 103 may acquire information on the area suitable for laser irradiation and the safe area from the monitoring device 110 described later via the communication unit 105.

[0027] The propulsion unit 104 is a functional unit that controls the attitude or orbit of the spacecraft 100 using a thrust generator (actuator) such as a thruster or a wheel to adjust the attitude required for laser irradiation. The attitude control method is not particularly limited, and existing methods such as the three-axis stabilization method, the bias momentum method, and the zero momentum method can be adopted.

[0028] The communication unit 105 is a functional unit for communicating with the ground monitoring device 110. Through the communication unit 105, the spacecraft 100 acquires information such as the approximate position (coarse orbit position) of the debris 200, the area suitable for the above laser irradiation, and the safe area.

[0029] The laser generating device 106 is a device that outputs a laser. In this embodiment, the laser generating device 106 simultaneously irradiates a plurality of different laser lights to more efficiently generate ablation on the object. A more detailed description of the laser generating device 106 and ablation will be given later.

[0030] The focusing unit 107 is a member for converging the laser emitted by the laser generating device 106. By passing through the focusing unit 107, the spacecraft 100 can emit a laser to the debris 200 even from a remote location. In this embodiment, the focusing unit 107 uses a general telescope, but is not limited to a telescope as long as it is a member for converging the laser. Also, in this embodiment, as a remote location, a position about 20 m to 1000 m away from the debris 200 is assumed, but the distance between the spacecraft 100 and the debris 200 is not particularly limited.

[0031] The steering unit 108 is a member for changing the irradiation direction of the laser output by the focusing unit 107. For example, a movable mirror can be used as the steering unit 108. By using the steering unit 108, the spacecraft 100 can easily direct the irradiation direction of the laser towards the debris 200 even from a remote location. Also, even when the spacecraft 100 and the debris 200 are not on the same orbit, the irradiation direction of the laser can be easily directed towards the debris 200 from a remote location, thus reducing the risk of the spacecraft 100 colliding with the debris 200.

[0032] In this embodiment, the laser generating device 106, the focusing unit 107, and the steering unit 108 collectively correspond to a "thrust generating device" for generating thrust on the object. Also, the focusing unit 107 and the steering unit 108 correspond to an "irradiation device" for irradiating the object with the laser light output from the laser generating device 106.

[0033] FIG. 4 is a diagram showing an example of the configuration of the focus unit 107 and the steering unit 108 according to the present embodiment. The laser output from the laser generator 106 gradually converges through the focus unit 107. Then, the laser is reflected by the steering unit 108, and the irradiation direction is changed.

[0034] Note that the method of directing the laser toward the target is not limited to the above. For example, without using the steering unit 108, the direction in which the laser is emitted may be changed by controlling the attitude of the spacecraft 100 itself. Also, by changing the direction of the focus unit 107, the direction in which the laser is emitted may be changed. In the present embodiment, an example is shown in which the focus unit 107 and the steering unit 108 are provided as part of the spacecraft 100, but they may be provided separately from the spacecraft 100.

[0035] ≪Monitoring device 110≫ The monitoring device 110 is a device that detects the approximate position of the debris 200 and transmits the information on the detected debris 200 to the spacecraft 100. Also, the monitoring device 110 may transmit information such as the area suitable for the above laser irradiation and the safe area to the spacecraft 100.

[0036] ≪Debris 200≫ In the present embodiment, the debris 200 may include small objects such as parts (e.g., screws) of artificial satellites released by collisions or the like from large objects such as artificial satellites that have become uncontrollable or artificial satellites that have become unnecessary due to the end of operation. Note that the target of the debris 200 is not limited to the above and includes objects existing in space (e.g., meteorites). Also, the size of the debris 200 is not particularly limited. Generally, among objects existing in space, those with a size of 10 cm or more can be detected from the ground, but the spacecraft 100 according to the present embodiment can detect objects with a size of 10 cm or less in order to detect the debris 200 in space.

[0037] <Explanation of the details of the laser device and ablation enhancement> FIG. 5A is a block diagram showing one specific example of the laser generating apparatus 106. The laser generating apparatus 106 includes a laser light source 601, a wavelength converter 602, and a wavelength converter 603. The laser light source 601 is, for example, a fiber laser or a solid-state laser using a Nd:YAG crystal that oscillates a laser beam with a wavelength of 1064 nm. In order to oscillate a laser beam in the 1-μm band, a Yb:YAG crystal may be used instead of Nd:YAG to oscillate a laser beam with a wavelength of 1030 nm. In this embodiment, a CW (continuous wave) laser is oscillated, but a pulsed laser may also be oscillated. The wavelength converter 602 has a non-linear optical crystal for converting a part of the laser beam generated from the laser light source 601 into the second harmonic. The non-linear optical crystal converts two photons of the fundamental wave into one photon with a frequency twice as high (wavelength half as long). Similarly, the wavelength converter 603 has a non-linear optical crystal for converting the second harmonic output from the wavelength converter into the fourth harmonic. The non-linear optical crystal converts two photons of the second harmonic into one photon with a frequency twice as high (wavelength half as long). Therefore, the fundamental wave (1064 nm), the second harmonic (532 nm), and the fourth harmonic (266 nm) are output from the laser generating apparatus 106.

[0038] Here, Non-Patent Documents 1 to 3 report that ablation can be enhanced by simultaneously irradiating an object with lasers having different wavelengths as described above. Briefly explaining the principle, when an object is simultaneously irradiated with a laser beam having a low absorption rate and a laser beam having a high absorption rate, the surface of the object is excited by the absorption of the laser beam having a high absorption rate, and ablation is more strongly generated even by the laser beam that originally has a low absorption rate.

[0039] FIG. 6 is a graph showing the wavelength-dependent characteristics of the absorption rate for each material. Here, it is assumed that the material of the object is aluminum, which is commonly used as a material for artificial satellites. Laser light in the 1-μm band can be easily generated by Nd:YAG or Yb:YAG, but the absorption rate in aluminum is low and the ablation intensity is weak. However, since the fourth harmonic (266 nm) has a high absorption rate, at least by irradiating the aluminum object with the fundamental wave and the fourth harmonic simultaneously, the surface is excited by the absorption of the fourth harmonic, making the fundamental wave more easily absorbed and ablation more likely to occur.

[0040] Here, the intensity of the fourth harmonic does not need to be very strong. It may be 10% or less, 1% or less, or 0.1% or less with respect to the fundamental wave. Therefore, high conversion efficiency is not required for the wavelength converters 602 and 603. To achieve high wavelength conversion efficiency, it is necessary to strictly control the angle and temperature of the nonlinear optical crystal in the wavelength converters 602 and 603, which increases the cost of the device. However, in this embodiment, even with low wavelength conversion efficiency, the effect can be obtained, so there is an advantage that the device can be easily fabricated and realized at low cost.

[0041] In this embodiment, the second harmonic may be removed and only the fundamental wave and the fourth harmonic may be irradiated, but since the second harmonic also contributes to ablation, the second harmonic may also be irradiated simultaneously. Furthermore, since the configuration for removing the second harmonic becomes unnecessary, the device configuration becomes simple.

[0042] Here, since aluminum is the object, the fourth harmonic is used. However, a suitable harmonic may be used according to the material of the object. For example, if the object is copper, the absorption rate becomes high at a wavelength of 600 nm or less. Therefore, if the fundamental wave (1064 nm) and the second harmonic (532 nm) are irradiated simultaneously, the effect of enhancing ablation can be obtained. When using the fundamental wave and the second harmonic, the laser generator 106 may include a laser light source 601 and a wavelength converter 602 as shown in FIG. 5B. In addition, since metals generally have a high absorption rate at around 300 nm or less, strong ablation can be generated for general metals by using the fourth harmonic (266 nm), the fifth harmonic (213 nm), or even higher harmonics with a 1-μm band laser oscillator.

[0043] The object is not limited to a metal material and may be any material. Examples of the material include glass, polymer, and CFRP (carbon fiber reinforced polymer composite material). Depending on the material, there may be cases where absorption occurs at a wavelength longer than 1 μm. When targeting such a material, as shown in FIG. 5C, the laser generator 106 may convert the wavelength of a part of the laser light output from the laser light source 601 by an optical parametric oscillator (OPO).

[0044] In the above description, the laser generating device 106 generates laser light of multiple wavelengths using one light source and a wavelength converter. However, the laser generating device 106 may have multiple light sources. For example, as shown in FIG. 7, the laser generating device 106 may have an Nd:YAG laser light source 901 and a semiconductor laser light source 902, and two laser lights may be combined and irradiated by mirrors 903 and 904. Semiconductor lasers are small in size, and even if the number of light sources is increased, there is no disadvantage in the device configuration. In addition, since semiconductor lasers can oscillate laser light with wavelengths in a wide range from visible light to infrared, a semiconductor laser of an appropriate material may be adopted according to the material of the object. For example, when the object is aluminum, since there is absorption in the 800 nm band, if an infrared semiconductor laser is adopted as the semiconductor laser light source 902, strong ablation can be generated with respect to aluminum.

[0045] In the above description, the laser irradiation device (thrust generating device) 109 is mounted on a spacecraft, and the use of irradiating debris 200 in space with a laser to change the position and attitude of the debris 200 by the thrust due to ablation was described. However, the laser irradiation device (thrust generating device) is not limited to use in space and may be used on the ground or in the atmosphere.

[0046] (Demonstration data) A verification experiment was conducted to show that ablation is actually enhanced by irradiating an object with lasers of different wavelengths simultaneously. Here, copper is used as the object. As shown in FIG. 6, copper has a high absorption rate at wavelengths of 600 nm or less. Therefore, in the verification experiment, using the laser generating device having the configuration shown in FIG. 5B, laser light of 1064 nm and 532 nm was simultaneously irradiated onto the object, and the generated force moment was measured. Also, as a comparative experiment, the force moments generated when the laser light of 1064 nm and the laser light of 532 nm were individually irradiated onto the object, and when these lasers were irradiated onto different locations of the object were measured. In all of these experiments, the average pulse energies of the laser lights of 1064 nm and 532 nm were set to 188 mJ and 89 mJ, respectively.

[0047] The experimental results were obtained as follows. The reproducibility of the average thrust under the same conditions is estimated to be 0.01. [Table 1]

[0048] As can be seen from these results, the momentum obtained by irradiating the same location with two-wavelength laser light is 4.99 μNs, which is greater than the sum of the momenta obtained by irradiating each wavelength of laser light. On the other hand, the momentum obtained by irradiating two different locations with two-wavelength laser light is 4.73 μNs, which is approximately equal to the sum of the momenta obtained by irradiating each wavelength of laser light. When irradiating the same location, the obtained thrust increases by 0.26 μNs (5.6%) compared to the case of irradiating different locations, and this increase is recognized as the superior synergistic effect of this method.

[0049] (Others) The configurations of the above-described embodiments and modifications can be appropriately combined and used within the scope not departing from the technical idea of the present invention. Further, the present invention may be implemented by appropriately changing it within the scope not departing from its technical idea. [Description of Reference Numerals]

[0050] 100: Spacecraft 101: Acquisition Unit 102: Detection Unit 103: Control Unit 104: Propulsion Unit 105: Communication Unit 106: Laser Generator 107: Focusing Unit 108: Steering Unit 109: Laser Irradiation Device 110: Monitoring Device 200: Debris

Claims

**Claim 1** A thrust generating device mounted on a spacecraft for irradiating an object existing in space with a laser to generate thrust on the object, comprising: a laser generating device that outputs laser light; an irradiation device that irradiates the object with the laser light output from the laser generating device; and the laser generating device includes: a laser light source that generates first laser light in the 1-μm band; a nonlinear optical crystal that converts the wavelength of a part of the light of the first laser light in the 1-μm band generated from the laser light source to 1 / 2, and outputs laser light including the first laser light in the 1-μm band and second laser light having a wavelength of 1 / 2 of the first laser light; the irradiation device irradiates the object with the laser light including the first laser light and the second laser light output from the nonlinear optical crystal; a thrust generating device. **Claim 2** The thrust generating device according to claim 1, wherein the wavelength conversion efficiency in the nonlinear optical crystal is 10% or less. **Claim 3** The thrust generating device according to claim 1, wherein the wavelength conversion efficiency in the nonlinear optical crystal is 0.1% or less. **Claim 4** A thrust generating device mounted on a spacecraft for irradiating an object existing in space with a laser to generate thrust on the object, comprising: a laser generating device that outputs laser light; an irradiation device that irradiates the object with the laser light output from the laser generating device; and the laser generating device includes: a laser light source that generates first laser light in the 1-μm band; a nonlinear optical crystal that converts the wavelength of a part of the light of the first laser light in the 1-μm band generated from the laser light source to 1 / 2, and outputs laser light including the first laser light in the 1-μm band and second laser light having a wavelength of 1 / 2 of the first laser light; a second nonlinear optical crystal that converts the wavelength of a part of the light of the laser light output from the nonlinear optical crystal to 1 / 2, and outputs laser light including the first laser light in the 1-μm band, the second laser light having a wavelength of 1 / 2 of the first laser light, and third laser light having a wavelength of 1 / 4 of the first laser light; the irradiation device irradiates the object with the laser light including the first laser light, the second laser light, and the third laser light output from the second nonlinear optical crystal; a thrust generating device. **Claim 5** The thrust generating device according to claim 4, wherein the wavelength conversion efficiencies in the nonlinear optical crystal and the second nonlinear optical crystal are 10% or less. **Claim 6** The thrust generating device according to claim 4, wherein the wavelength conversion efficiencies in the nonlinear optical crystal and the second nonlinear optical crystal are 0.1% or less. ​ ​

6. The wavelength conversion efficiency in the non-linear optical crystal and the second non-linear optical crystal is 0.1% or less. The thrust generating device according to claim 4.

7. A thrust generating device mounted on a spacecraft for irradiating an object existing in outer space with a laser to generate thrust on the object, comprising: A laser generating device that outputs laser light; An irradiation device that irradiates the object with the laser light output from the laser generating device; Comprising: The laser generating device includes: A laser light source that generates first laser light in the 1 μm band; An optical parametric oscillator that converts the wavelength of a part of the first laser light in the 1 μm band generated from the laser light source and outputs laser light including the first laser light in the 1 μm band and second laser light having a longer wavelength than the first laser light; The irradiation device irradiates the object with the laser light including the first laser light and the second laser light output from the optical parametric oscillator. Thrust generating device.

8. The laser light source is a solid-state laser or a fiber laser oscillating in the 1 μm band. The thrust generating device according to any one of claims 1 to 7.

9. The laser light source is a Nd:YAG laser light source, and the wavelength of the first laser light is 1064 nm. The thrust generating device according to any one of claims 1 to 8.

10. The wavelength of the second laser light has a higher absorption rate in the object than the wavelength of the first laser light. The thrust generating device according to any one of claims 1 to 9.

11. A spacecraft in outer space that irradiates an object with a laser to change the orbit or attitude of the object, comprising: The thrust generating device according to any one of claims 1 to 10; The irradiation device irradiates the laser light so that the laser light output from the laser generating device converges on the object. Spacecraft.

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