Space propulsion method of nanosecond-femtosecond composite light filament
By employing a nanosecond-femtosecond composite filament method, which utilizes femtosecond lasers to form a guiding channel and nanosecond laser energy deposition, the problem of energy attenuation in long-distance laser propulsion is solved, achieving high specific impulse and rapid response propulsion effects.
Patent Information
- Application Number
- CN202511756881.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-27
- Publication Date
- 2026-01-09
AI Technical Summary
Existing laser propulsion technology suffers from severe energy attenuation due to laser beam diffraction, atmospheric attenuation, and turbulence effects during long-distance transmission, making it difficult to achieve high specific impulse and rapid response propulsion effects.
The nanosecond-femtosecond composite optical filament method is adopted, which uses femtosecond laser to form a stable optical filament channel to guide the nanosecond laser. The energy absorption efficiency of the nanosecond laser is improved by pre-ionization and surface modification of the femtosecond laser, and energy loss is reduced in atmospheric and vacuum environments, so as to achieve efficient energy transmission and propulsion.
Achieving high specific impulse, rapid response, and efficient energy transfer under long-distance conditions significantly improves propulsion efficiency, reduces thrust response time to the microsecond level, and achieves a specific impulse of 400-6000s, which is far superior to traditional methods.
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Figure CN121291814A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of laser propulsion technology, specifically to a method for achieving high thrust and high specific impulse space propulsion using nanosecond-femtosecond composite filaments under long-distance conditions. Background Technology
[0002] Laser propulsion, as an advanced propulsion technology, has shown great application potential in aerospace missions such as deep space exploration and orbit maintenance due to its high specific impulse, no fuel consumption, strong controllability, and remote operation capabilities. Pulsed laser ablation propulsion uses laser irradiation on the surface of a target material, causing it to rapidly melt, vaporize, and even ionize, forming a high-speed, reverse-ejected plasma plume that generates thrust. Its specific impulse can exceed 3000s, significantly higher than traditional chemical propulsion (typically below 500s), and it outperforms typical electric propulsion systems in terms of thrust, while allowing for precise control of specific impulse and thrust. Therefore, laser propulsion technology has become a current research hotspot. The authorized patent CN114279272A designs a laser propulsion system that uses a high-energy laser emitter to emit high-energy laser light, providing propulsion energy for a laser-propelled spacecraft, realizing a non-contact propulsion method based on light energy transfer.
[0003] However, existing laser propulsion technologies face significant challenges in achieving long-distance applications. When lasers are transmitted over long distances (tens of kilometers), the laser beam diffracts and diverges, and is affected by atmospheric attenuation and turbulence, resulting in a significant reduction in power density at the target. This necessitates megawatt-level power from the laser to deliver sufficient energy to the laser-propelled aircraft. Traditional focusing techniques struggle to ensure efficient transmission and precise focusing of high-energy laser beams in atmospheric or vacuum environments, further limiting the efficiency of the laser-target interaction.
[0004] Although the interaction between composite lasers (such as nanosecond lasers and millisecond lasers) and the target is believed to enhance plasma reaction and shock wave intensity, thereby increasing specific impulse, and this composite method can achieve extremely high peak power density under short focal length conditions, its power density will drop to one-hundredth or even one-thousandth of the original value under long-distance transmission conditions, which makes it extremely difficult to effectively excite plasma shock waves on the material surface.
[0005] Furthermore, under the action of a single laser (especially nanosecond or continuous lasers), the response time of the propulsion process is usually between tens and hundreds of nanoseconds. However, when the laser transmission distance is extended to kilometers or even tens of kilometers, the material ablation and plasma formation processes are significantly delayed due to energy attenuation and reduced target absorption efficiency. The establishment time of the back-jet plasma can increase to the order of microseconds, resulting in a lag in thrust response and a decrease in efficiency, making it difficult to achieve a fast and controllable propulsion response.
[0006] To address the issue of transmission loss over long distances, existing technologies have proposed synergistic composite laser approaches. Patent CN119057248A discloses a "long-distance, high-efficiency composite laser destruction method," which uses an ultrafast laser to create a kilometer-scale optical filament channel in the air to reduce energy attenuation, and then uses a continuous laser to continuously irradiate the target material, achieving long-distance destruction. However, the continuous laser used in this approach is a low peak power density, high average energy output mode, while the propulsion specific impulse is roughly positively correlated with the laser power density to the target. This continuous laser has a power in the tens of thousands to tens of millions of watts range, and its peak power density to the target is only 100 W / cm². 2 -10000W / cm 2 When the target surface is irradiated, the thermal effect is the main factor, and the specific impulse generated is less than 100s, which makes it difficult to meet the requirements of high specific impulse propulsion.
[0007] In contrast, this invention uses a high-energy nanosecond pulsed laser instead of a continuous laser in the composite laser structure to achieve instantaneous energy deposition and efficient ablation. Nanosecond lasers possess a high peak power density (102). 8 With a pulse width of -10¹¹ W / cm² and a controllable pulse width (from several nanoseconds to hundreds of nanoseconds), it can induce the melting, vaporization and plasma back-jet process of the target material in a very short time, thereby significantly improving energy utilization and thrust specific impulse.
[0008] Meanwhile, the filamentary channel formed by the femtosecond laser can serve as an energy guiding path for the nanosecond laser filament, effectively reducing long-distance transmission loss. Compared to picosecond lasers, femtosecond lasers have higher peak power and shorter pulse widths, making it easier to exceed the self-focusing critical power in air, rapidly triggering the nonlinear Kerr effect and ionization process to form a stable and continuous filamentary structure. Picosecond lasers, due to their longer pulse widths, significant thermal accumulation effects, and higher filamentation thresholds, are prone to filament instability or energy decay, making it difficult to maintain stable transmission over kilometers or even tens of kilometers. The intensity clamping effect of the femtosecond filament maintains its internal intensity at 10¹³-10¹⁰. 5 Within the W / cm² range, this enables highly stable, self-guided, and low-loss energy transmission in the atmosphere. Based on this, the present invention selects a femtosecond laser instead of a picosecond laser as the spatial filamentation source, which is more suitable for constructing a stable long-distance transmission channel, achieving effective guidance and energy synergy of the nanosecond laser filament.
[0009] The spatial propulsion method for nanosecond-femtosecond laser composite filaments proposed in this invention guides the nanosecond laser filament to achieve long-distance energy deposition by constructing a stable filament transmission channel using a femtosecond laser, achieving a peak power density to the target of up to 10-1. 8 With a specific impulse of -10¹¹ W / cm², it generates a specific impulse of 400-6000 s, which is significantly better than the specific impulse of femtosecond laser combined with continuous laser and other traditional composite laser schemes for space propulsion. Summary of the Invention
[0010] To address the issues of low efficiency and high energy loss in existing laser propulsion technologies under long-distance transmission conditions, this invention proposes a space propulsion method using nanosecond-femtosecond composite optical filaments. This method organically combines the spatial filamentation capabilities of femtosecond and nanosecond lasers with the extremely high peak energy density of femtosecond lasers and the high energy deposition characteristics of nanosecond lasers, constructing a highly efficient composite propulsion system suitable for distances of tens of kilometers.
[0011] Under atmospheric conditions, femtosecond lasers form stable optical filament channels through their spatial filamentation principle, utilizing the intensity clamping effect to maintain the intensity of the femtosecond laser at 10¹³-10¹ during long-distance transmission. 5 With a power density of W / cm², it effectively overcomes the energy attenuation problem of traditional lasers in atmospheric environments caused by scattering, absorption, and turbulence, reducing laser energy attenuation to less than 15%. The guiding effect of the optical filament ensures that the femtosecond laser beam remains collimated and does not diverge during propagation. Furthermore, the pre-ionization and surface modification of the target surface by the femtosecond laser significantly improves the energy absorption efficiency of the subsequent nanosecond laser, thereby reducing the ablation threshold of the target and enhancing the propulsion effect.
[0012] In vacuum or near-vacuum environments, femtosecond lasers, lacking dielectric molecules, cannot form traditional filament structures as they do in atmosphere. However, thanks to their high coherence, low divergence angle, and high peak power, femtosecond lasers can still achieve collimated long-distance energy transmission under vacuum conditions. In a vacuum, the transmission loss of femtosecond and nanosecond lasers mainly originates from diffraction effects; due to the lack of dielectric absorption and scattering, energy loss is relatively small. By selecting a laser with an appropriate aperture, beam divergence caused by diffraction can be effectively reduced, ensuring low-loss energy transmission in the vacuum section and thus guaranteeing high transmission efficiency during long-distance transmission.
[0013] By simultaneously considering the laser transmission characteristics in both atmospheric and vacuum environments, this invention provides a long-distance laser transmission method between the ground and an aircraft. In an atmospheric environment, femtosecond and nanosecond lasers effectively overcome scattering, absorption, and turbulence effects through spatial filamentation, ensuring stable energy transmission. In a near-vacuum environment, femtosecond and nanosecond lasers, through appropriate laser aperture selection, mitigate beam divergence caused by diffraction effects, achieving low-loss energy transmission. This method effectively combines the transmission characteristics of both media, ensuring that the laser maintains high-efficiency energy transfer and propulsion effects throughout the long-distance transmission from the ground to the aircraft.
[0014] This invention not only overcomes the problems of power density attenuation and response delay in long-distance transmission of traditional lasers, but also achieves more efficient propulsion performance through the spatiotemporal coordination mechanism of femtosecond and nanosecond lasers. Specifically, the femtosecond laser filament is responsible for "energy conduction and induction," forming a pre-ionization layer (plasma number density 10¹²-10¹²) on the target surface through its non-thermal ionization effect and short-pulse high peak power. 4 The dual-filament layer (cm⁻³) and roughening modification layer (surface roughness Ra=0.1-10μm) significantly improve the absorption efficiency of the target material for subsequent nanosecond lasers. The nanosecond laser filament is responsible for "energy deposition and propulsion." In the plasma channel generated by the femtosecond laser, efficient energy deposition occurs. Within microseconds, the surface material of the target material, under the combined action of the two filaments, undergoes rapid ionization, high-temperature expansion, and directional acceleration within 1-100ns, transforming into a plasma plume. The plume is directionally ejected at a speed of 1-10km / s, with the ejection momentum more than twice that of single-laser propulsion, reaching 1×10⁻⁻⁻⁶. 4 -1×10⁻² N·s / pulse, ultimately providing continuous and stable thrust for the spacecraft, achieving high specific impulse propulsion.
[0015] Compared with existing continuous or single-pulse propulsion technologies, the nanosecond-femtosecond filament propulsion system of this invention realizes a new space propulsion scheme with long distance, high response, high specific impulse, and precise control, which has obvious innovation and engineering application potential.
[0016] This invention provides a space propulsion method for a nanosecond-femtosecond composite optical filament, comprising the following steps:
[0017] Step 1: The femtosecond laser outputs high-energy femtosecond laser light, which is then spatially focused or collimated and transmitted to form a stable self-focusing filament channel of 0.1-20km in the atmosphere. The energy attenuation problem of the laser in the atmosphere is overcome by the light intensity clamping effect. The guiding effect of the filament ensures that the femtosecond laser beam remains collimated during propagation. At the same time, the pre-ionization and surface modification of the target surface by the femtosecond laser significantly improves the energy absorption efficiency of the subsequent nanosecond laser.
[0018] Step 2: After the femtosecond laser is applied, a high-energy nanosecond laser with a pulse width of nanosecond is output through a delay by the control module. After the direction is adjusted by the optical lens group, the nanosecond laser filament and the femtosecond laser filament are coaxially transmitted or transmitted at a certain angle. The two filaments are spaced 1-100ns apart and act on the same point of action of the target material in sequence.
[0019] Step 3: The nanosecond laser filament is directly transmitted or transmitted along the plasma channel formed by the femtosecond laser filament to reduce energy loss. Furthermore, the pretreatment of the target material by the femtosecond laser also improves the energy coupling efficiency of the nanosecond laser. The high-energy nanosecond laser filament with extremely high peak energy works together with the femtosecond laser filament. Within a time of nanoseconds to hundreds of nanoseconds, the dual filaments transform the target surface through three stages: rapid ionization, high-temperature expansion, and directional acceleration, into a rapidly ejected plasma plume, thereby achieving high specific impulse propulsion for spacecraft.
[0020] Furthermore, the nanosecond laser has a pulse width of 1ns-500ns, a wavelength of 800nm-2000nm or 9.3μm-10.6μm, a diameter of 0.5-8cm, a repetition frequency of 1Hz-500kHz, a corresponding single pulse energy of 100J-1mJ, and a target power density of 10⁻⁶ under direct transmission. 8 -10 9 W / cm², which produces a specific impulse range of N1=100-1500s.
[0021] Furthermore, the femtosecond laser has a pulse width of 10 fs-1000 fs, a wavelength of 700 nm-2666 nm, a diameter of 0.5-8 cm, a repetition frequency of 10 Hz-1 MHz, and a corresponding single pulse energy of 10 J-10 μJ. The femtosecond laser is maintained at 10 μJ through the guidance of a filament. 13 -10 15 A power density of W / cm² produces a specific impulse range of N² = 50-800s.
[0022] Furthermore, the target power density of the nanosecond laser filament transmitted along the femtosecond laser filament is 10. 8 -10 11 W / cm², the specific impulse range generated by the combined action of W / cm² and femtosecond laser filament is N3 = 400-6000s ≥ 2 (N1 + N2).
[0023] Furthermore, the space propulsion method of the nanosecond-femtosecond composite optical filament reduces energy loss caused by scattering, absorption and turbulence effects during transmission between atmospheric media through the principle of space filamentation, and achieves long-range laser energy transmission within a range of 0.1-20km with a loss of less than 15%.
[0024] Furthermore, the pre-ionization and surface modification effects of the femtosecond laser on the target surface, through non-thermal ionization effects, excite local plasma and roughen the surface, thereby enhancing the interaction efficiency between the nanosecond laser and the target by 30%-100%.
[0025] Furthermore, the intensity of the femtosecond laser spatial filamentation clamping beam is 10. 13 -10 15 W / cm2 The plasma channel density it produces is 10. 15 -10 17 cm -3 .
[0026] Furthermore, the optical lens assembly includes a reflector, a collimating lens, a beam splitter, a polarizer, and a waveplate, etc., to achieve coaxial or angle-adjustable transmission of femtosecond lasers and nanosecond lasers.
[0027] Furthermore, the nanosecond laser filament and the femtosecond laser filament are transmitted coaxially. The transmission direction is adjusted by the beam splitter, polarizer, and waveplate in the optical mirror group. The two laser beams are collimated and output through the same collimating lens so that their beam axes coincide to achieve coaxial transmission. The nanosecond laser filament and the femtosecond laser filament are transmitted at a certain angle. The transmission direction of the nanosecond laser filament is deflected by the reflector in the optical mirror group so that the axes of the nanosecond laser filament and the femtosecond laser filament intersect at the point of action on the target surface. The angle θ ranges from 0° to 25°.
[0028] Furthermore, the target material is poly(glycidyl azide) (GAP), gold, titanium, aluminum, or copper. Overall, compared with the prior art, the technical solution conceived by this invention has the following main technical advantages:
[0029] 1. Existing long-distance laser propulsion methods mainly rely on single lasers or simple composite methods, resulting in severe energy attenuation after transmission and difficulty in maintaining high power density. The nanosecond-femtosecond filamentary space propulsion method proposed in this invention utilizes the power clamping effect of femtosecond laser spatial filamentation to achieve efficient laser transmission over tens of kilometers, solving the problem of low propulsion efficiency of single lasers or simple composite lasers over long distances. With the assistance of femtosecond laser spatial filamentation, the energy absorption efficiency of the nanosecond laser filament is significantly improved, thereby generating a stronger reflected plasma plume, significantly enhancing the thrust and specific impulse of the propulsion.
[0030] 2. Traditional laser propulsion technology typically generates thermal effects on the material surface, resulting in some energy waste. This invention, however, significantly improves the energy absorption rate of the target material for subsequent nanosecond lasers through pre-ionization and surface modification of the femtosecond laser. The femtosecond laser not only alters the physicochemical properties of the target surface, making its absorption of nanosecond lasers more efficient, but also greatly enhances the energy coupling efficiency. This modification effect significantly improves the specific impulse of the propulsion system, maintaining high propulsion efficiency and specific impulse even at long distances, thereby enhancing the overall performance of the propulsion system.
[0031] 3. The combined use of femtosecond and nanosecond laser filaments can achieve melting, vaporization, and even ionization of target materials in an extremely short time, thereby enabling space propulsion. Under the same laser parameters, traditional laser propulsion methods typically require milliseconds or seconds to generate effective propulsion on the target surface, while nanosecond-femtosecond composite lasers can shorten the interaction time to the microsecond level, thus achieving efficient target propulsion in a shorter time, suitable for space missions requiring rapid response.
[0032] 4. This invention is applicable to a variety of target materials and propellants, including various solid or liquid polymers or metal materials, and can enhance the target material absorption rate by preparing special microstructures on the target material surface, thereby improving the specific impulse; in addition, this invention can achieve precise control of thrust, specific impulse and propulsion direction by adjusting laser parameters and transmission angle. Attached Figure Description
[0033] Figure 1 The system diagram of nanosecond-femtosecond laser coaxial transmission in the spatial propulsion method of the nanosecond-femtosecond composite filament provided by the present invention.
[0034] Figure 2 The system diagram of the nanosecond-femtosecond laser propulsion at an angle θ for the spatial propulsion method of the nanosecond-femtosecond composite filament provided by the present invention.
[0035] Figure 3 This is a schematic diagram illustrating the principle of the laser propulsion method of the present invention, showing the process of spatial propulsion effect generated by the interaction between the laser and the target material.
[0036] Explanation of reference numerals in the attached figures:
[0037] 1-Controller; 2-Femtosecond laser; 3-Nanosecond laser; 4-Optical mirror group; 5-Nanosecond-femtosecond laser filament; 6-Femtosecond laser filament axis; 7-Nanosecond laser filament axis; 8-Target material; 9-Plasma plume; 10-Femtosecond laser filament; 11-Nanosecond laser filament; 12-Target material energy absorption region; 13-Nanosecond-femtosecond composite laser; 14-Thrust; 15-Acceleration sensor. Detailed Implementation
[0038] To make the technical problems, solutions, and advantages of this invention clearer, a detailed description will be provided below with reference to the accompanying drawings and specific embodiments. It should be noted that these descriptions of the embodiments are intended to aid in understanding the invention but do not constitute a limitation thereof.
[0039] Examples provided by the present invention Figure 1The diagram illustrates a space propulsion method using a nanosecond-femtosecond composite optical filament. This method comprises a controller 1, a femtosecond laser 2, a nanosecond laser 3, an optical mirror group 4, and a target material 8. The femtosecond laser 2 emits a high-energy femtosecond laser beam that irradiates the surface of the target material 8, forming a femtosecond laser filament 10 to assist in long-distance energy transmission. Simultaneously, the nanosecond laser 3 emits a high-energy nanosecond laser beam to form a nanosecond laser filament 11, which is reflected by the optical mirror group 4 and coaxially transmitted with the femtosecond laser filament 10. The plasma channel generated by the femtosecond laser filament 10 enhances the interaction between the nanosecond laser filament 11 and the target material 8, generating a high-speed, back-jet plasma plume 9 for efficient propulsion.
[0040] Specific examples:
[0041] Example 1: A femtosecond laser with an output wavelength of 800 nm, a pulse width of 200 fs, a single pulse energy of 5 mJ, a repetition rate of 5 kHz, and an output power of 25 W, is focused by a telescope system to form a stable self-focusing filament with a diameter of 1 cm and a length of 3 km in the atmosphere. A nanosecond laser with an output wavelength of 1064 nm, a pulse width of 20 ns, a single pulse energy of 10 mJ, a repetition rate of 5 kHz, and an output power of 50 W, is collimated by a collimating lens and its direction is adjusted by a group of reflecting mirrors. It is coaxially transmitted with the femtosecond laser filament, with a spot diameter of 3 cm. The delay control module is set to lag the femtosecond laser output by 10 ns. The target material is a 3 mm thick gold plate, placed 3 km away from the laser system. The nanosecond and femtosecond laser filaments are coaxially transmitted 3 km to the target surface, with a peak power density of approximately 1.24 × 10⁻⁶. 9 W / cm², with stable thrust and a specific impulse of about 1500s, and an impulse coupling coefficient of 65 N / MW.
[0042] Example 2: A femtosecond laser with an output wavelength of 515 nm, a pulse width of 100 fs, a single pulse energy of 10 mJ, a repetition rate of 5 kHz, and an output power of 50 W, is collimated by a telescope system in Burst mode (25 sub-pulses) to form a 20 km long plasma filament channel. A nanosecond laser system with an output wavelength of 1064 nm, a pulse width of 50 ns, a single pulse energy of 25 mJ, a repetition rate of 5 kHz, and an output power of 125 W is coaxially transmitted with the femtosecond filament after adjustment by an optical mirror group containing polarizers and waveplates. The delay control module is set to lag the femtosecond laser output by 50 ns. The propellant is a viscous liquid GAP with an energy density of 42 MJ / kg, placed in a propellant tank at a distance of 20 km. Under the action of the nanosecond laser alone, due to significant energy loss, the power density to the target is only 1.06 × 10⁻⁶. 8 W / cm², generating a specific impulse of 350s and an impulse coupling coefficient of 12N / MW; while in the nanosecond-femtosecond synergistic effect, the plasma channel formed by the femtosecond laser filament significantly reduces energy loss, achieving a peak power density of 3.11×10⁻⁶ at the target. 9W / cm², its specific impulse is increased to 4200s, and the impulse coupling coefficient reaches 73 N / MW.
[0043] Example 3: A femtosecond laser with an output wavelength of 1030 nm, a pulse width of 500 fs, a single pulse energy of 2 mJ, a repetition rate of 25 kHz, and an output power of 50 W, is focused to form a 10 km long optical filament channel. A nanosecond laser (CO2 laser) with an output wavelength of 10.6 μm, a pulse width of 100 ns, a single pulse energy of 4 mJ, a repetition rate of 25 kHz, and an output power of 100 W is used. Its transmission angle is adjusted via a rotatable mirror, and it is transmitted to the same point of action on the target surface at a 15° angle to the femtosecond filament. A delay control module is set to lag the nanosecond laser output by 60 ns. The target material is a 6 mm thick industrial pure titanium plate, placed at a distance of 10 km. Under the action of the femtosecond laser alone, the peak power density of the laser reaching the target reaches 3.18 × 10¹. 4 The average power density to the target is approximately 270 W / cm², with a specific impulse of only 150 s and an impulse coupling coefficient of 8 N / MW. However, in the nanosecond-femtosecond synergistic effect, the nanosecond laser propagates along the femtosecond filament channel, reducing the total loss and achieving a peak power density to the target of 2.32 × 10¹. 0 With W / cm², the two optical filaments are precisely aligned on the target surface, and the titanium target is uniformly ablated to form a directional reverse-jet plasma plume, increasing the specific impulse to 2800s and the impulse coupling coefficient to 61 N / MW.
[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A spatial propulsion method for nanosecond-femtosecond composite optical filaments, used to solve the problem of low efficiency in long-distance laser propulsion, characterized in that, include: Step 1: The femtosecond laser outputs high-energy femtosecond laser light, which is then spatially focused or collimated and transmitted to form a stable self-focusing filament channel of 0.1-20km in the atmosphere. The energy attenuation problem of the laser in the atmosphere is overcome by the light intensity clamping effect. The guiding effect of the filament ensures that the femtosecond laser beam remains collimated during propagation. At the same time, the pre-ionization and surface modification of the target surface by the femtosecond laser significantly improves the energy absorption efficiency of the subsequent nanosecond laser. Step 2: After the femtosecond laser is applied, a high-energy nanosecond laser is output after a delay by the control module. After the direction is adjusted by the optical lens group, the nanosecond laser filament and the femtosecond laser filament are transmitted coaxially or at a certain angle. The two filaments are spaced 1-100ns apart and act precisely on the same point of action of the target material one after the other. Step 3: The nanosecond laser filament is directly transmitted or transmitted along the plasma channel formed by the femtosecond laser filament to reduce energy loss. Furthermore, the pretreatment of the target material by the femtosecond laser also improves the energy coupling efficiency of the nanosecond laser. The high-energy nanosecond laser filament with extremely high peak energy works together with the femtosecond laser filament. Within a time of nanoseconds to hundreds of nanoseconds, the dual filaments transform the target surface through three stages: rapid ionization, high-temperature expansion, and directional acceleration, into a rapidly ejected plasma plume, thereby achieving high specific impulse propulsion for spacecraft.
2. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The nanosecond laser has a pulse width of 1 ns-500 ns, a wavelength of 800nm-2000nm or 9.3μm-10.6μm, a diameter of 0.5-8cm, a repetition frequency of 1Hz-500kHz, a single pulse energy of 100J-1mJ, and a target power density of 10⁻⁶ under direct transmission. 8 -10 9 W / cm², which produces a specific impulse range of N1=100-1500s.
3. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The femtosecond laser has a pulse width of 10 fs-1000 fs, a wavelength of 700 nm-2666 nm, a diameter of 0.5-8 cm, a repetition frequency of 10 Hz-1 MHz, and a single pulse energy of 10 J-10 μJ. The femtosecond laser is maintained at 10 fs by a guiding filament. 13 -10 15 A power density of W / cm² produces a specific impulse range of N² = 50-800s.
4. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The target power density transmitted along the femtosecond laser filament by the nanosecond laser filament is 10. 8 -10 11 W / cm², the specific impulse range generated by the combined action of W / cm² and femtosecond laser filament is N3 = 400-6000s ≥ 2 (N1 + N2).
5. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The space propulsion method of the nanosecond-femtosecond optical filament reduces energy loss caused by scattering, absorption and turbulence effects during transmission between atmospheric media through the principle of space filamentation, and achieves long-range laser energy transmission within a range of 0.1-20km with a loss of less than 15%.
6. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The pre-ionization and surface modification effects of the femtosecond laser on the target surface, through non-thermal ionization, excite local plasma and roughen the surface, thereby enhancing the interaction efficiency between the nanosecond laser and the target by 30%-100%.
7. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The intensity of the femtosecond laser spatial filament clamping beam is 10. 13 -10 15 W / cm 2 The plasma channel density it produces is 10. 15 -10 17 cm -3 .
8. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The optical lens assembly includes a reflector, a collimating lens, a beam splitter, a polarizer, and a waveplate, etc., and is used to achieve coaxial or angle-adjustable transmission of femtosecond lasers and nanosecond lasers.
9. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The nanosecond laser filament and the femtosecond laser filament are transmitted coaxially. The transmission direction is adjusted by the beam splitter, polarizer and waveplate in the optical mirror group. The output is collimated by the same collimating lens so that the beam axes of the two laser beams coincide to achieve coaxial transmission. The nanosecond laser filament and the femtosecond laser filament are transmitted at a certain angle. The transmission direction of the nanosecond laser filament is deflected by the reflector in the optical mirror group so that the axes of the nanosecond laser filament and the femtosecond laser filament intersect at the point of action on the target surface. The angle θ is in the range of 0°<θ≤25°.
10. The space propulsion method for nanosecond-femtosecond composite optical filaments according to claim 1, characterized in that, The target material is poly(glycidyl azido) ether (GAP), gold, titanium, aluminum, or copper.