A method for detecting stellar composition based on hypervelocity impacts

Abstract

The present invention belongs to the field of stellar mineral composition detection, and specifically relates to a method for detecting the surface composition of a stellar body by hypervelocity impact, which specifically refers to: throwing a projectile on the surface of a stellar body tens of kilometers away in a catapult manner on an aircraft, and using the large relative speed between the aircraft and the stellar body, the projectile hits the surface of the stellar body at a hypervelocity of kilometers per second and induces high-temperature and high-pressure plasma. The plasma emits strong light and emits discrete atomic spectral lines during the expansion and cooling process. A telescope and a high-sensitivity grating spectrometer are set on the aircraft to collect and analyze the plasma atomic spectral lines to achieve long-distance stellar surface composition detection.

Description

Technical Field

[0001] The present invention relates to the field of stellar mineral composition detection, and in particular to a stellar composition detection method based on hypervelocity impact. Background Art

[0002] In the exploration and resource development and utilization of the moon and Mars, and the exploration of asteroids, comets and giant planets, the detection of stellar composition is an important part. There are currently two main methods for stellar composition detection: sample return detection and online in-situ detection. An example of online in-situ detection is the LIBS (Laser induced breakdown spectrum) detector used on NASA's ChemCam Mars rover. LIBS technology refers to the process of irradiating the surface of an object with a focused high-energy density laser to form a GW / cm 2 The power density is increased, thereby inducing a multi-photon absorption process. The ionized electrons undergo an avalanche effect under the acceleration of the laser electric field. When the electron density in the irradiated area exceeds a certain threshold, the material in the irradiated area will be broken down or dissociated to form a high-temperature and high-pressure plasma. Plasma can emit light, and by analyzing the plasma spectrum with a highly sensitive spectrometer, information about the elements that make up the material can be obtained. The diagram of ChemCam's LIBS detection system is shown below. The main advantage of the LIBS method is that it has a high degree of accuracy in detecting the composition of the material.

[0003] The sampling and return method requires the design of complex spacecraft landing, sample collection, and spacecraft return engineering plans, which is extremely costly and has a long mission cycle. Online in-situ detection requires the complex detection payload to be loaded on the rover, and the landing engineering design of the rover on the surface of the celestial body is required. In addition, the LIBS detection system can only detect a distance of about a few meters around the rover. Obviously, whether it is sampling return or online in-situ detection, the samples that can be obtained are limited to a certain range around the landing point or the rover. The range of action of the rover is usually very limited, which means that if you want to detect the mineral composition at multiple different locations on the surface of a celestial body that are far apart, it is still a resource-intensive task.

[0004] Whether it is sampling return or online in-situ detection, their inconvenience is obvious. Summary of the invention

[0005] Based on the relative speed between the spacecraft and the celestial body being higher than 1 km / s, the present invention proposes a scheme in which a projectile is launched from the spacecraft to impact the surface of the celestial body to excite plasma, and by collecting the plasma, the composition of the shallow surface material of the celestial body can be efficiently detected over a large scale and at multiple points over a long distance.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions.

[0007] The present invention proposes a method for detecting stellar composition based on hypervelocity impact, the method comprising:

[0008] The projectile is launched toward the surface of the target star using the launch device on the aircraft, and the relative motion speed between the aircraft and the target star is used to make the projectile impact the surface of the star at a high speed, thereby generating plasma by impact;

[0009] The impact was monitored using a high-definition telescope on board the spacecraft and the plasma spectrum was collected;

[0010] The atomic spectral lines of the plasma spectrum are analyzed using the spectrometer on the aircraft. By analyzing the intensity of the atomic spectral lines, the content of each component at the impact position of the target star can be obtained.

[0011] As an improvement of the above technical solution, when launching the projectiles, multiple projectiles are launched simultaneously.

[0012] As an improvement of the above technical solution, the mass of the projectile is 2.5 grams to 10,000 grams.

[0013] As an improvement of the above technical solution, the material of the projectile is copper alloy.

[0014] As an improvement of the above technical solution, the relative motion speed between the aircraft and the target star is required to reach more than 1 km / s.

[0015] As an improvement of the above technical solution, the celestial body is an asteroid, a planet or a satellite.

[0016] As an improvement of the above technical solution, the spectrometer on the aircraft is an ICCD grating spectrometer.

[0017] As an improvement of the above technical solution, the method further includes:

[0018] Before the impact, a high-definition telescope and spectrometer were used to record and analyze the background space spectrum;

[0019] By comparing the spectra before and after the impact, the background spatial spectrum is removed from the plasma spectrum after the impact to obtain the atomic spectrum lines of the plasma spectrum.

[0020] As an improvement of the above technical solution, the background space spectrum comes from the interference of space background light from sunlight and the sunlight reflected by the star. A high-speed flying aircraft carries a projectile and flies toward the star at a high relative speed, throwing one or several projectiles at the star dozens of kilometers away. The projectile is made of copper alloy and other materials, with no restrictions on shape and a mass between 2.5-10000 grams. The projectile hits the surface of the star at a speed greater than 1 km / s, and the impact induces the plasmaization of the superficial components of the star, accompanied by strong light. During the relaxation of the plasma, atoms transition from the excited state to the ground state, emitting atomic spectral lines. The impact event is monitored by a high-definition telescope carried on the aircraft, and the plasma emission spectral lines are collected. The plasma spectral lines are analyzed on-site using an ICCD (Intensified charge-coupled device) high-resolution grating spectrometer carried on the aircraft. By comparing the spectral signals before and after the impact, the interference of space background light from sunlight and the sunlight reflected by the star is eliminated, and the atomic spectral lines in the plasma spectrum are obtained, thereby obtaining the information of the superficial components of the star.

[0021] Compared with the prior art, the advantages of the present invention are:

[0022] 1. The present invention makes full use of the relative speed of up to 1 km / s between the spacecraft and the celestial body, and realizes high-precision testing of the material composition of the shallow surface of the celestial body by launching projectiles to form plasma. This breaks through the limitation that the traditional high-precision measurement of the material composition of celestial bodies can only be limited to a few meters within the area where the spacecraft arrives, and achieves a breakthrough in the high-precision measurement of the material composition of celestial bodies within a hundred kilometers of the spacecraft flyby area, which will greatly promote the development of celestial body detection;

[0023] 2. The spacecraft can launch multiple projectiles to the surface of the celestial body, impacting different positions far apart; the optical signals of these different impact positions are collected and analyzed by the spacecraft's telescope system and ICCD grating spectrometer, so that multi-target online measurement of the celestial body can be achieved;

[0024] 3. The kinetic energy of the projectile's impact on the celestial body mainly comes from the relative speed between the detector and the celestial body, which is as high as 1 km / s. No additional projectile acceleration device is required, and the cost is relatively low;

[0025] 4. Different from the laser-induced plasma in the LIBS scheme, this scheme uses the ultra-high-speed impact of alloy projectiles on the solid surface to induce plasma. This scheme is aimed at the luminescence analysis of plasma formed by the impact on the surface of a solid planet (such as an asteroid); therefore, the present invention has the advantages of high precision and high measurement speed of LIBS technology, while solving the problem that the laser of LIBS is easy to diverge and difficult to bunch during long-distance transmission, and can also achieve a one-time impact on multiple points; and, since the plasma luminescence has extremely high brightness, the optical signal can be collected and analyzed tens of kilometers away. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the spectrum detection scheme for hypervelocity impact stars and plasmas;

[0027] FIG. 2( a ) is a laser-induced plasma luminescence image, and FIG. 2( b ) is an impact-induced plasma luminescence image.

[0028] Reference numerals

[0029] 11. Aircraft 12. Projectile delivery device 13. Projectile

[0030] 14. Projectile flight path 15. Star surface 16. Plasma

[0031] 17. Plasma beams 18. Telescopes 19. Optical fibers

[0032] 20.ICCD grating spectrometer DETAILED DESCRIPTION

[0033] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0034] Example

[0035] The present invention proposes to throw a projectile of a certain mass onto the surface of a target star (such as the moon, Mars, Venus, asteroids, etc.) on a spacecraft, and use the relative speed difference between the spacecraft and the star to achieve a hypervelocity impact of the projectile on the surface of the star. The huge energy of the impact is used to form a high-temperature and high-pressure plasma near the impact position. The plasma components are electrons and ions of the elements on the surface of the star. The plasma then expands outward at supersonic speed and cools. In this process, the excited ions and atoms in the plasma transition from high-energy states to low-energy states, thereby radiating atomic spectral lines. The different elemental components on the surface are reflected on the spectral lines as characteristic emission spectra at discrete special wavelength positions, and the relative intensity of the atomic spectral lines has a linear relationship with the content of the surface elements. Figure 2 (b) shows the impact plasma luminescence pulse simulated by a ground-based micro-debris accelerator device, which is similar to the plasma luminescence pulse obtained by laser irradiation in the LIBS scheme (shown in Figure 2 (a)) in terms of luminescence intensity, luminescence time, and attenuation mode. The optical signal in the plasma is collected by a telescope on the spacecraft, and the atomic spectral lines of the plasma spectrum are analyzed using the ICCD grating spectrometer on the spacecraft. By analyzing the intensity of the atomic spectral lines, the element content at the impact position can be quantitatively analyzed.

[0036] In order to generate impact plasma, the impact speed must be above 1 km / s. Usually, the speed of an asteroid can reach several km / s to tens of km / s. For example, the speed of 7335 (1989JA) asteroid reaches 21 km / s. Aircraft. Since the aircraft is not subject to air resistance in space, it can also reach high speed. For example, the Japanese Hayabusa aircraft, which is propelled by an ion engine, reaches a speed of 27 km / s. When the aircraft flies straight toward the planet from the oblique side or the positive direction, the relative speed between the two can easily reach more than 1 km / s. At this time, there is no need to set up an additional high-energy projectile launch device on the aircraft. It is only necessary to make the projectile hit the surface of the planet by simply detaching or throwing it at a low speed along the flight trajectory to ensure that the impact speed reaches more than 1 km / s, thereby forming an impact plasma.

[0037] For impacts against asteroids, due to the small size of asteroids (diameters range from a few hundred meters to a few kilometers), after a projectile is launched from a spacecraft dozens of kilometers away, the projectile may not accurately hit the asteroid. The present invention proposes that multiple projectiles can be launched at the same time to form a barrage to hit the asteroid, ensuring a high probability of impact.

[0038] Since there is no air resistance in space, there is no special requirement for the shape of the impact projectile used in the present invention, which can be spherical, bullet-shaped, or any irregular shape. The material of the projectile needs to be selected based on a preliminary estimate of the composition of the impacted surface, and elements that are not contained in the planetary composition should be selected to manufacture the projectile. The plasma spectrum after the impact contains both information about the composition of the planetary surface and information about the elements of the projectile material. By using two projectiles made of different elements to perform two impacts, the interference of the projectile elements can be eliminated by comparing the plasma spectrum components of the two impacts.

[0039] The aircraft payload associated with the present invention mainly includes two independent systems: a projectile launching device and a plasma optical signal detection system.

[0040] Usually, the relative speed between the aircraft and the detected star in space can reach above 1 km / s, so there is no need to set up an additional projectile acceleration device on the aircraft, and only an ordinary projectile ejection device (such as the device used by bombers to drop bombs) is needed. Figure 1 As shown, when the aircraft 11 moves toward the surface of the celestial body 15 at a relative speed of more than 1 km / s, the projectile 13 is delivered to the surface of the celestial body 15 in a catapult manner. Since the gas in space is rarefied, the projectile suffers very little kinetic energy loss during the space flight and has a trajectory 14 that is well approximated to a straight line, which can easily ensure that the projectile accurately hits the predetermined position of the celestial body 15.

[0041] The impact process is monitored by telescope 18. When a strong luminous signal other than the background is detected near the predetermined impact point, the impact is confirmed to be successful. The optical signal 17 emitted by the plasma 16 formed by the impact is collected by telescope 18, and the optical signal is introduced into optical fiber 19 after beam focusing. Optical fiber 19 is connected to spectrometer 21. Spectrometer 21 performs spectral analysis on optical signal 17, identifies discrete atomic spectral lines, analyzes the element content ratio at the impact point through the relative intensity of the atomic spectral lines, and infers the compound of its main component.

[0042] Taking a 25g copper alloy projectile as an example, if it hits the measured star at a speed of 10km / s, then a 1kg launch capacity can launch 40 projectiles. These projectiles are fired at the star from dozens of kilometers away, and sequentially hit different positions of the star in a scattered manner. Then the detection system on the aircraft can sequentially obtain dozens of light signals. Spectral analysis of these light signals can obtain composition information at dozens of different positions.

[0043] Technical problems solved by this application:

[0044] 1. How to achieve plasma formation of stellar surface components at a long distance.

[0045] As mentioned above, the key to plasmatizing the impacted position by impact is that the relative impact speed must reach more than 1 km / s. This speed can be achieved by utilizing the ultra-high relative speed formed by the high-speed flight of the aircraft itself and the high-speed movement speed of the celestial body itself. During the flight of the projectile, the projectile is not affected by air resistance, but only by a certain degree of influence of the gravity of the celestial body. For an asteroid impact, the projectile is approximately in uniform linear motion during flight. The movement of the celestial body itself also flies at a certain speed along a certain trajectory. Therefore, a simple calculation can ensure that the projectile and the celestial body collide. Since the mass of each projectile is only about a few grams, multiple projectiles can be thrown at the same time to form a projectile array, thereby further increasing the probability of a successful impact.

[0046] 2. How to collect and identify plasma spectrum signals tens of kilometers away.

[0047] The plasma spectrum formed after the projectile hits the planetary surface is collected and analyzed on-site by a light-collecting high-definition telescope and a high-resolution spectrometer carried by a spacecraft dozens of kilometers away. After the high-definition telescope captures the light signal generated by the impact, it focuses the captured light and then introduces it into a high-resolution grating spectrometer through an optical fiber for spectral line analysis. In the process of light capture, the interference faced is mainly the background spectrum, whose main sources are sunlight and sunlight reflected by the impacted celestial body. Before the impact, the background space spectrum is recorded and analyzed using a high-definition telescope and a high-resolution grating spectrometer. After the impact occurs, due to the high impact energy, the intensity of the plasma luminescence is very high. At this time, the light-collecting high-definition telescope on the spacecraft dozens of kilometers away will observe a strong flash at the impact site. It is calculated that the intensity of the flash can reach more than dozens of times the background spectrum. In the subsequent delay time of about a few microseconds, the plasma is in the de-excitation relaxation stage, and its atoms and ions transition from high-energy states back to low-energy states, which can form atomic spectral lines. The atomic spectral line components include those from the projectile components and the planetary surface, and are characterized by strong peaks at certain specific frequencies, which are easily distinguished from the continuous background spectrum in space. By comparing the spectral lines recorded by the high-resolution grating spectrometer before and after the impact, the composition of the plasma spectral line can be identified.

[0048] Assuming the projectile size is 10mm 3 , with a mass of about 2.5g. When the impact speed reaches 10km / s, the impact kinetic energy is about 1.25*10 5 J. Assuming that the plasma luminescence diffuses in a spherical surface, it can be calculated that the theoretical detection distance of the plasma luminescence formed under this high-energy impact can reach 24.7km. If the mass of the projectile is increased to 25g, the theoretical detection distance can reach 78km. At this time, it is possible to use the telescope light collection system and grating spectrometer system on the aircraft to detect the plasma spectrum formed by the impact on the surface of the star from tens of kilometers away.

[0049] This method is based on the applicant's team's research on the impact effect of space debris for many years. It makes full use of the relative speed between the spacecraft and the celestial body in interstellar exploration, which can reach more than 1 km / s. It proposes a new method for detecting the material composition of the celestial body, which can achieve high-precision remote measurement of the material composition of the shallow surface of the celestial body on a large scale. This method actively launches a certain size of projectile on the spacecraft to impact the measured celestial body, and uses the relative speed between the spacecraft and the celestial body greater than 1 km / s to make the projectile hit the celestial body at high speed, stimulate the ionization of the surface material of the celestial body on the ns time scale, and form a plasma cluster similar to the plasma detected by LIBS but with a larger spatial size and higher brightness. The ICCD spectrometer on the spacecraft can collect and analyze the impact luminescence at a distance of tens of kilometers or even hundreds of kilometers, so as to realize the detection of the material composition of the shallow surface of the celestial body. When a hypervelocity impact occurs, the shock wave propagates into the material, accompanied by huge pressure (greater than 100Gpa) and energy transfer. This causes the local temperature of the material near the impact site to rise rapidly (more than 10000K), resulting in the vaporization of the material and the formation of high-temperature and high-pressure plasma. The key parameter that affects the peak value of the shock wave pressure and the peak value of the local temperature after the impact is the impact speed. When the impact speed is lower than 5km / s, the impact products are mainly broken solid particles; when the impact speed exceeds 25km / s, the impact objects are basically completely vaporized; and in the impact between 5km / s and 25km / s, the products are a complex mixture of solid particles and liquid, gas, and plasma. When the impact speed is above 1km / s, the conditions for the formation of impact plasma can be met and light can be emitted.

[0050] The applicant proposes a method of using a spacecraft to throw projectiles at the surface of a celestial body to form a hypervelocity impact, so that the shallow surface components of the celestial body in the impact area are excited to form plasma, and the plasma spectrum can be collected and detected at a distance of tens or even hundreds of kilometers, so that when orbiting the moon, Mars and other planets, the celestial body can achieve a global and efficient "general measurement" of its shallow surface material components at multiple points. When flying over comets, asteroids and giant planets, multi-point high-precision telemetry of celestial body components is carried out to avoid the unfavorable factors of high technical difficulty and high risk brought by direct landing on the celestial body. In addition, this method can design the appropriate number and quality of projectiles according to the specific detection target, realize multi-target and multi-point detection during flyby detection, and has higher detection efficiency. It has great advantages for the detection of asteroids with high detection technology difficulty and long time period. Furthermore, this detection method can be combined with sampling and return detection. When detecting the asteroid belt, the material composition of multiple asteroids is firstly telemetered based on this method, and better target asteroids are selected for sampling and return based on the analysis and processing of telemetry data, which greatly improves the efficiency of asteroid detection.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A method for detecting stellar composition based on hypervelocity impact, the method comprising: The projectile is launched toward the surface of the target star using the launch device on the aircraft, and the relative motion speed between the aircraft and the target star is used to make the projectile impact the surface of the star at a high speed, thereby generating plasma by impact; The impact was monitored using a high-definition telescope on board the spacecraft and the plasma spectrum was collected; The atomic spectrum of the plasma spectrum is analyzed by the spectrometer on the aircraft. By analyzing the intensity of the atomic spectrum, the content of each component at the impact position of the target star can be obtained; The relative motion speed between the aircraft and the target star is required to reach more than 1 km / s.

2. The method for detecting stellar composition based on hypervelocity impact according to claim 1, characterized in that: When the projectiles are launched, a plurality of projectiles are launched simultaneously.

3. The method for detecting stellar composition based on hypervelocity impact according to claim 1, characterized in that: The mass of the projectile is 2.5 g to 10000 g.

4. The method for detecting stellar composition based on hypervelocity impact according to claim 1, characterized in that: The material of the projectile is copper alloy.

5. The method for detecting stellar composition based on hypervelocity impact according to claim 1, characterized in that: The celestial body is an asteroid, a planet or a satellite.

6. The method for detecting stellar composition based on hypervelocity impact according to claim 1, characterized in that: The spectrometer on the aircraft is an ICCD grating spectrometer.

7. The method for detecting stellar composition based on hypervelocity impact according to claim 1, characterized in that: The method further comprises: Before the impact, a high-definition telescope and spectrometer were used to record and analyze the background space spectrum; By comparing the spectra before and after the impact, the background spatial spectrum is removed from the plasma spectrum after the impact to obtain the atomic spectrum lines of the plasma spectrum.

8. The method for detecting stellar composition based on hypervelocity impact according to claim 7, characterized in that: The background spatial spectrum comes from the interference of sunlight and the spatial background light reflected by stars.

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