We Live in Nanjing

It is now 2:22 in the morning. Perhaps people tend to be more sensitive at night. After reading this book with the sound of rain outside the window, I can't help but feel a little melancholy. I will write down my thoughts after reading this book, mainly from an emotional perspective to record my mood at this time. (Contains spoilers) When I saw the setting at the beginning of the novel, I thought of "Your Name" by Makoto Shinkai. However, unlike the three-year connection between the male and female protagonists in "Your Name", the 21 years between 2040 and 2019, a generation of time, made me have some gloomy doubts in my heart from the beginning. Because science fiction is different from fantasy novels, it requires not only an imagination that transcends the reality of scientific physics, but also a rigor that is consistent with the history of scientific development - that is, in the absence of soul memory settings, the ending is ultimately love and separation. Either time has passed and we never met, or maybe the future has been changed and 21 years have passed, and you are no longer the beautiful woman in your memory. The bond that traveled through time was destined to end at the beginning, leaving readers feeling disappointed. The author has profound skills in character construction. The one we can't let go of is the girl who is more or less unable to let go - even if she lives alone in the end of the world, she is still positive and optimistic. She still rides a bicycle, faces the wind and the sun, sings loudly, is a strong and brave girl. As male readers, we tend to put ourselves into the role of the male protagonist. I think most readers will have a sense of powerlessness when reading the book. Why does such a lively and lovely girl have to bear so much alone? She is injured again and again, she cries, feels pain, acts coquettishly, and makes trouble, but again and again she carries responsibilities that she could have refused on her thin shoulders. We can only watch her fall alone, but because of the time gap, we can only grit our teeth and clench our fists feebly. How we wish we could be by her side and help her! Compared with other characters in the book, the male protagonist's attitude towards Pinellia ternata is more complicated. Whether it is Lao Zhao, Lao Wang, Lao Dad or everyone else, their protection and help for Pinellia ternata is more or less based on their own safety and interests. Only the male protagonist knows that if fate had not caused him to meet Banxia, ​​and if he had not conveyed the news that mankind would perish in the future, Banxia might not have suffered all the subsequent events, and could still survive alone in the end of the world - unfortunately there is no if. This feeling is contradictory, and Banxia chose to sacrifice herself to benefit mankind, and to fulfill this fateful encounter, she moved forward firmly and never regretted her choice. But is she still her in another future? For Bai Yang, the girl who talked to him every night and got to know each other from the moment they met, with her and the future she observed has completely disappeared, and is only retained in the memories of Bai Yang and a few people. She is a hero. This experience is ultimately a relief but a difficult one for Bai Yang and the readers. I like this story. I remember Nanjing and the girl in my memory deeply. I look forward to more exciting stories from the author.

Recommended by big eyes, so come and take a look. As soon as I opened it, I was so worried that I couldn't stop. At first, I thought the heroine's parents just passed away, and there were teachers and other people hugging each other for warmth. I later found out that the teacher was also a corpse. Later I found out that there was no one but her. I can't imagine how lonely and desperate a person feels in an empty world. Ban Xia is most worried when she goes to "meet netizens" and look for evidence. The happier and more hopeful you are before preparation, the more desperate you will be in the end. And it was so aggrieved to look for evidence in the rain, get injured and catch a cold, and lose the umbrella left by the teacher. Looking forward to the update, but I can't bear to see a person's loneliness and despair. {"TopicId":"627459049453125632","TopicName":"We live in Nanjing"}

Loneliness, courage, the hymn of mankind and the future What do I want to write about On March 22, 2022, I spent three hours reading the latest chapter. I finally began to regret why I didn't study hard and read more books when I went to college. Accumulate more things, but today I can't even write a decent sentence in the review section of such a good book. That's all, do whatever you want. What resonates most emotionally with me in this book is loneliness. Man is a social animal, and man is the sum of social relationships. But when the speed of scientific and technological progress has already affected genes countless times, the most brilliant achievement from modern civilization, the Internet, which claims to have shrunk the earth, really makes me feel lonely. Think back to how your parents described their relationships with college classmates, and then think about yourself. With the development of productivity brought about by the advancement of science and technology. The new generation's social interactions are becoming more and more narrow. People are becoming more and more like isolated islands separated by isolated islands. Just like Pinellia ternata and Poplar 21 years later in the article. The two men leaned against an old piece of radio equipment. Looking at each other crazily. After all, we can't meet each other. The deep-seated loneliness of Pinellia ternata destroyed my defense And the deeper feeling than loneliness is fear If a person is young and strong but stops moving forward. It's not that he doesn't know where the road ahead is, it's that wherever he looks, there are dead ends. For now. The development of human society is once again transforming from an incremental game to a stock game. The improvement of the new generation of productivity represented by controllable nuclear fusion technology is far away (just judging from the news, the current limit of mankind is less than 10 minutes), and the international situation is deteriorating. When I watch the news, I have the illusion that I am watching news from the 1930s. Speaking with a bit of unfounded pessimism, our generation may experience what Einstein said, a return to sticks and stones from the Fourth World War to the Fifth World War. The economy is in recession, the international situation is turbulent, and the epidemic's offensive continues. Each of us is full of pessimism and fear about our future. Amplify fear to an entire civilization. Is there really an antidote to the decadence of civilization today? Can we really become at least a Type II civilization and travel the universe before the sun goes out? Does the persistence of civilization really mean anything in the face of the law of entropy increase? Won't everything eventually turn into dust? But Pinellia is not like this, afraid of loneliness, afraid of swordsmen, and afraid of a future that seems to have no hope. Because of this, we have such empathy with this girl, and even feel a bit of sympathy for her. She stubbornly persisted for that weak and pitiful hope. A young girl who is so strong that she doesn't dare to cry loudly. How similar it is to the enlarged version of us. . . But after fearing and crying? Some things should not be persisted until there is hope. But there is hope only if you persevere. Not all battles are for victory, but to prove that we have fought fearlessly. We briefly defeated the vulgar, dirty and mediocre part of our genes, and in a certain moment turned into shining meteors to guide the direction of human progress. Maybe, everything Bai Yang did in the timeline was in vain, maybe. In the end, the two couldn't even see each other. Perhaps, human civilization is destined to fail, to be extinguished, and to turn into dust. But I don't think it's important I saw the blending of two souls spanning 20 years I saw the pure empathy of two children from their hearts and their good deeds of saving others and saving themselves I saw the determination of a civilization that racks its brains and never gives up, and dares to fight a war that is bound to lose. I saw loneliness. Fear, saw courage, wisdom. I saw love, I saw the stars belonging to civilization in the sky This is enough

Congratulations on being praised by People's Daily👏

The ending is almost meaningless. The future timeline is modified, how people will resist in the future, and the origin of the black moon. These are all not explained in detail. Even if it is not good, there can be a side story about Teacher Banxia's past and add to the worldview setting... This ending, A light "love", for me personally, I am not very satisfied 😐 The ending aside, this is an excellent work. I see the shadow of "The Three-Body Problem" and "The Dragon" in it, and it is indeed worth watching.

I have read some science fiction works, such as Liu's Three-Body Problem, Ball Lightning, etc. Asimov's Galactic Empire. These are physical books to read. How can I put it, science fiction is rare in online literature, and true science fiction is even rarer. Most of them write fantasy under the guise of science fiction. Among the many online science fiction novels I have read, this one is my favorite. Secondly, I really didn't want to be a savior, but it sucked in the later stages. I hope the author can write a complete story.

Today is Ban Xia's birthday, I wish her a happy birthday.

It's quite a hard-core science fiction, with strong logic, but enough humor to make it readable even on the Internet. I particularly like the daily interactions between the three middle-aged people. It is very real and funny. When these people get together, it is like talking about cross talk 🤭. Also, the author's description is full of a cinematic feel. Sometimes I can make up the transitions between scenes and shots based on the author's description. The characterization is also quite good, with Banxia being the best and easily making readers feel distressed. The plot is overall bland, and there are not many suspenseful and exciting elements. Most of the plot is about daily life in two timelines. However, the author is very skilled and still manages to create a sense of crisis about the impending doomsday through ordinary daily life. Overall, a masterpiece of fairy grass quality!

I hope the author can update a chapter next year Only in the 24th year can the characters in the book confirm whether the future has really been changed Even if only one line of text is updated, nothing will happen in the 24th year.

Putting aside whether there is any novelty, the writing is first-rate and the rhythm is very accurate. How can I put it, writing is sometimes very important, even surpassing the novel plot. Of course, it would be better if the update speed could be faster, which makes people anxious~😅

I call the author a birch bark writer who can burn but only a little bit, too short! ! ! ! !

See you later when I go home

I first learned about Tian Rui talking about Fu Da Yao in the interview column of Kantianxia Magazine in Vista. At that time, I ran to watch Dead Fire (although I didn't finish it because it was too hardcore). Personally, I think the biggest difference between this book and Dead Fire is that the setting of this book is more interesting than Dead Fire. The themes of Dead Fire and "The Martian" are both survival on Mars, but the theme of this book is very novel and very attractive. Moreover, the radio and other things introduced in this book can be easily understood by me as a layman (it would be too bad to put the original English paper directly in the dead fire), and I am interested in radio (I am preparing to take the A certificate next month). Finally, I want to say that the plot of "Time Slow Delivery" is so appetizing to me. It makes me want to create a "Time Slow Delivery" so that my future self can travel back and send money to the present me.

After reading it, the final ending of the heroine reminded me of the working warriors in the original Stone Gate, and they were mysteriously similar. I didn't feel much about the element of Jun's name that was the original source of inspiration written in the author's postscript. On the contrary, Stone Gate has a sense of déjà vu, although the endings are very different. Although some authors wrote that the male protagonist's background was blocked halfway through, and the female protagonist was transformed into a tool. As a result, Jun's name as an emotional line is very weak in this work. On the contrary, the main line has been reversing the future based on the concept of "Observer". It is also possible that I have read the work "Cold Ozone" with this setting before Jun Ming. Although it does not span time but only spans space, the description of the male and female protagonists meeting each other many years later also creates a sense of division of time. On how many science fiction works a double-slit observation experiment has supported. The author said in the middle of the game that the setting of the superimposed state in the future is different from the world line concept in Stone Gate. However, after watching the ending, isn't it the same concept as two different world lines? However, the author's hypothesis that information determines materials in this work is actually a bit close to the setting of the Chaos series with the same world view as Stone Gate (game, if anyone is interested, be sure to play the game instead of watching the anime). To sum up, this is a very worth-reading novel. Although the setting is not perfect and self-consistent, and although there are a lot of characters and characters and tools in the middle, it is considered a relatively strong one among online novels. In the early stage, I even felt like I was playing one of the few time-themed galgames with excellent scripts. The early storyboards are really graphic and feel like the most creative part of the book. By the way, when will it be made into a movie?

When I saw the award, I thought it was over. 😭 Results... {"NickName":"TeaOFF","UserId":349086513}

The first book of Reading Dog is fully ordered, too short, too short, too short! I hope the author will be longer, but I don't want the author to write a long novel

My job is to deal with the past and the future, so I will tell you my opinion. If the time capsule buried by the protagonist is dug out, it means that the other party is the current future. It is not the future of a parallel world, nor is it a future that becomes a parallel world. So the disappearance of human beings is inevitable no matter how we operate. Unless it's a cunning operation, after confirming that the villain can be defeated to save the earth, after communicating with the future heroine, under the strategy. Let Nanjing become an empty city and make the heroine think that he is the only one left in the entire Nanjing city and the entire world. Empty the library and turn the effect into the cause. In the finale, the man and woman can still meet each other. This is the perfect ending.

I didn't catch up on "Dead Fire" in time, so I didn't want to read it because it was spoiled. The writing style and writing style of this book are very suitable for me. If there are no accidents, I will finish it.

This book is really hard science fiction. It contains a lot of professional knowledge and nouns. New readers should study hard 🙂

Nice and short I hope you won't stop updating

[Minor spoilers] This article tries not to deviate from reality while unfolding the story of Bai Yang and Pinellia ternata across time and space. What is most refreshing to me is the concept of slow time. The author's rigorous argumentation is far beyond the level of online writing. But the final ending of Banxia is still disappointing. Has the timeline been changed? The author did not explicitly state that the disconnection will bring an end to Nanjing where Banxia is located. Personally, I think this open ending is not as good as a real ending. However, the author has hinted at the identity of Teacher Forsythia by using Morse crypto coins, which means that the future has been determined, cannot be changed, and cannot be changed. This is fate. I came to look at this work because I saw a picture on website b that seemed to have no meaning at the time. That picture was the actual location of Poplar and Pinellia in the book. To be honest, it's quite surprising that all real addresses can be used. This book was written with the hope that it could be remade, looking forward to the future of animation. Finally, I would like to thank the author for bringing such a story. In any case, Banxia and Baiyang already live in the same Nanjing. Although the future is destined to be desperate, at least there is still the present, right? Overall Rating 9 (9.5-0.5 (Like knives?))/10 73 2025.11.9 In Nanchang (accidentally saw China Southern Airlines)

：        ，，， But if it is because of this, then how was it discovered that humans had no plans to conduct observations in the original world line? In my understanding, if you want to jump the world line, the difficulty can be large or small, and the difference in the jump will also be large or small. For example, if you didn't eat breakfast today, it would have basically no impact on the world. The butterfly flapping its wings is too small. But if you can kill Einstein, then the destiny of mankind will inevitably be changed, and the world line will jump significantly. But only if you know he is Einstein. I hope someone can answer this. Here are some feelings: This book is well written, combining urban, apocalyptic science fiction, and technology (radio) very well. Although the ending is heart-wrenching, I hope Banxia can really embrace them. This kind of book with time travel always gives people a great shock. When human beings face the end of the world, you can feel that although there are not many people fighting, in fact, there are humans standing behind you not only who are with you in space, but also who are standing with you in time. They are farmers who once plowed the fields, businessmen who found a small fortune, emperors and generals, talented men and beauties, great physicists... They are the accumulation of human civilization for thousands of years. This is the people's view of history. History is created by the people. In this book, Einstein and Kepler are great, but Bai Yang and Pinellia ternata are also great. All those who strive for the future of mankind are great. In the apocalyptic atmosphere, this book also has a relaxed and humorous atmosphere, such as the interaction between Xiao Baiyang and his classmates, Pinellia ternata and Bai Yang, the addition of Forsythia, and the fight between the members of the original Nanjing Command (the one about reversing the future is too long). It is these down-to-earth atmospheres that make us feel familiar and ordinary. They are just ordinary people, struggling high school seniors, middle-aged people starting a family (starting a career?), An ordinary little girl, and a high-spirited young girl... The plot tension is formed between the crisis-ridden apocalypse and the warm dialogue, making this book full of romance. The setting of this book is also very interesting for science fiction. No matter what happens, human beings are always on the road of "seeking knowledge" and walking on the road of "practice". The setting of the swordsman is quite interesting, and it feels like watching "Mysterious Resurrection". This process of cracking rules and exploring the unknown is particularly attractive. Human beings will always be on the road of seeking knowledge! Regarding the adaptation, I hope that this book can be adapted into an animation, which will definitely attract many people. The last little question is how the author managed to make the real place names appear in the book. Can you pass this review (⊙o⊙) ——Written in the school library on December 14, 2025

The author's writing style is good, but his understanding of knowledge outside his own major, especially physics, is limited. The description of time is not interesting except for the slow delivery. A cross-universe civilization that can see the past, present, and future cannot disappear just because it stops observing. Everything left must leave traces, and the open ending is just a beautiful fantasy. Moreover, the author likes to embarrass Fat Hu, which reflects the author's essence: it is natural. To the author, the digestive enzymes are the same. It can be said that except for the annoying automatic magic modification, this book is basically good!

The author's writing is really good. I made a picture with PS on a whim after reading it for the second time today. It's very rough, just for fun

Let me update the progress of Ban Xia Ge, we should be able to meet during the May Day holiday. Powered by love, I spent hundreds of dollars on illustrations, my heart is bleeding.

Some amateur radio slang that may be useful 1: CQCQCQ (means you want to talk, a broad call) 2: Insert (also means you want to talk) 3: Please speak (you, or multiple parties agree to talk) 4:59+ (means the signal is strong) 8:73 (Sending good wishes, often used for goodbye, etc.) 9:57 (indicating good signal) 10: Cannot afford the meter (indicating a certain difficulty in copying) 11: Full meter (the signal is in the best condition) 12: Restoration (referring to the other party's voice, no echo or unclear situation) 13: Coverage (Generally refers to the phenomenon that the car station covers the hand station more) 14: Eyeball (meaning to meet) 15: Copying (meaning you have received the other party's signal) 16: Noise (meaning the other party's speech is unclear, the signal transmission is unstable or there is equipment communication sound) 17: Listening (meaning to only listen but not talk) 18: Equipment (Referring to the station, or handheld station and a complete set of communication equipment) 19: Point (the position of you or the other party) 20: Lane 2, Lane 3 (Refers to several channels of fixed frequencies in the fleet, such as 420.100 Is 1 channel, 420.150 Is 2 channels) 21: Miaozi (car-mounted or handheld small antenna) 22: Bangzi (stick) (medium and large fixed antenna) 23:88 (more intimate kiss goodbye) 24: Listen (only listen and don't talk)

First of all, a common sense science. The threshold for radio is very low. You don't need to learn the principles to become a HAM. You only need to memorize the question bank and take the exam held by the local non-committee to obtain the operation certificate. Then take the radio station you bought to inspect the machine and apply for a license. After that, you can legally communicate. Elementary school students can use the school's group station to play shortwave. This is the first time I have seen a novel with amateur radio as the main theme. It is really good. Now fewer and fewer people play it. I am born in the 1990s. When I was a child, radios were still used at home and in school. After the popularity of smart phones, you can plug in a headset into your mobile phone and use it as a radio. But now radio has basically disappeared in daily life, and mobile phones have also lost their radio function and changed it to Internet radio. There are more frequencies that can be listened to, but they are gone when the Internet is disconnected. Listening to the radio has gradually become a niche, let alone amateur radio. At least most people born after 2000 still know what radio is, but not many know what radio is. Mobile phones are indeed convenient, but when there is a sudden disaster or entering a weak signal area, only radio can set up a communication network. The most impressive thing was the amateur radio rescue in the 2008 Wenchuan earthquake. Because there were many earthquakes in Sichuan, an emergency communication network was established before the earthquake. After the earthquake, a command and dispatch system was quickly set up. However, the signal was interrupted. Hanwang to Mianzhu relied entirely on amateur radio as communication guarantee, and Beichuan to Tangjiashan only relied on an amateur relay as a communication bridge. There was no other way to establish contact with the outside world except radio. HAM directly shouldered the communication task. At that time, some rescue forces focused on disaster relief supplies but neglected communications. In some areas, HAMs were required to carry radios on their backs to accompany the troops as they moved forward to provide communications support. A 7.1-Magnitude earthquake in Yushu, Qinghai, a huge mudslide in Zhouqu, Gansu, a 7.0-Magnitude earthquake in Ya'an... Amateur radios are always present before sudden natural disasters. Not long ago, heavy rains in Zhengzhou caused widespread power and communication outages. The Zhengzhou Radio Administration Bureau temporarily coordinated four radio frequencies for emergency use, and advocated the active use of amateur radio to assist the city's emergency rescue departments and social rescue organizations in emergency rescue and disaster relief. Amateur radio A certificate can use the UV segment, mainly hand-held radios and mobile radios. Hand-held radios only cost 200 to 300 yuan to get started. Quansheng tg-uv2, Baofeng 5r, etc. Are classic radio stations, and second-hand radios are cheaper. However, more and more people are playing digital nowadays, and there are fewer people on analog frequencies. B certificate can play shortwave, you can use direct voice or CW (Morse code tick tock). Shortwave stations are slightly more expensive, there are various types, and antennas need to be set up - usually on the roof. If it is not convenient to set up antennas on high floors, using a fishing rod antenna sticking out of the window will work. For outdoor communications, there are those kind of rod antennas, which are very portable. Relevant policies, regulations, question banks, etc. Can be queried on the CRAC (Amateur Radio Branch of China Radio Association) website, registration and examination information can be viewed on the local RRC website or WeChat official account, and you can join the local Amateur Radio QQ group for communication and understanding. The use of radio stations should be legal to set up station communications. This is BG2DFO, you are welcome to join.

Some new readers think the update is very slow. To clarify, old readers also think the update is very slow 🙂

Electric propulsion has the characteristics of high specific impulse, long life and highly autonomous cruise. The detector uses electric propulsion to perform orbital maneuvering tasks during the cruise phase, which will significantly reduce the propellant weight and increase the load-to-weight ratio. In October 1998, the US "Deep Space 1" (DS-1) spacecraft was successfully launched; in May 2003, the Japanese "Hayabusa" probe was successfully launched; in September 2007, the US "Dawn" probe was successfully launched; at the end of 2014, the Japanese "Hayabusa-2" probe was successfully launched. The above detectors are all equipped with electric propulsion systems and use them for main propulsion. The system performance is excellent. This article investigates the electric propulsion system solutions for foreign detectors. In response to the mission requirements of this slow delivery operation, based on the existing electric thruster technology, 5 electric propulsion system solutions are proposed, and multi-dimensional comparisons are made to design and key technologies for the optimal solution. 1 Introduction to foreign detector electric propulsion systems 1.1 The American "Deep Space 1" ion electric propulsion system [1-3] In October 1998, the American "Deep Space 1" spacecraft was launched. Its goal was to conduct close detection of the 1992KD asteroid and to detect comets 107PBorreiiy and 19PWilson-Harrington. The main mission of the ion electric propulsion system is to complete the main propulsion of the spacecraft during the cruise phase, and at the same time undertake the pitch and yaw control tasks during part of the period. The ion electric propulsion system increases the total speed of the spacecraft to 4.5 Km/s, and the cumulative working time of the ion thruster exceeds 16 246 h. The system block diagram is shown in Figure 1. Figure 1 Block diagram of DS-1 ion electric propulsion systemFig. 1 Ion electric propulsion system of SD-1 DS-1 ion electric propulsion system consists of a 30 cm ion thruster, a power processing unit (PPU), a xenon feeding subsystem (XFS) and a digital control & interface unit (Digital Control & Interface Units, DCIU). The ion thruster works with the support of xenon delivered by XFS and voltage and current conditions provided by PPU. XFS and PPU work under the control of DCIU. At the same time, DCIU receives and executes instructions from the satellite computer and transmits telemetry data of the ion electric propulsion system to the satellite data system. In order to match the output power of the solar panel under different solar distance conditions, the working power range of the ion thruster is designed to be 525-2300 W. It is Kaufuman type with a diameter of 30 cm. The design thrust range is 19-92 mN. The corresponding specific impulse range is 1950-3100 s. The design life of the full power 2.3 KW operating point is 8000 h. The gate component is a double gate structure made of molybdenum material, and the accelerating voltage is 1280 V. 1.2 Japan's Hayabusa ion electric propulsion system [4-5] In May 2003, Japan's Hayabusa probe was launched. Its mission is to detect the near-Earth asteroid 25143 Itokawa and obtain samples for return. The detector weight is 510 kg. The main task of the ion electric propulsion system is main propulsion during the cruise phase. In addition, in some phases, it also undertakes tasks such as orbit eccentricity correction, attitude control, and position maneuver maintenance. At the end of 2014, Japan's Hayabusa2 probe was launched to conduct rock sampling and return detection of the near-Earth asteroid 1999 JU3, which required a total velocity increment of about 2.2 Km/s generated by the ion electric propulsion system. The "Hayabusa" ion electric propulsion system consists of (as shown in Figure 2) 4 μ10 microwave discharge ion thrusters, 4 microwave power amplifiers, 3 power processing units (Ion Power Processing Unit, IPPU), a propellant supply subsystem, a thrust vector pointing mechanism and an ion thruster control unit. The dry weight of the system is 59 kg, the xenon carrying capacity is 66 kg, the cumulative working time of the four ion thrusters is about 40,000 hours, and the cumulative working time of the most used thruster reaches 15,000 hours. Four ion thrusters are installed in an array on the same thrust pointing mechanism. Three IPPUs switch power to the four thrusters through relays. Up to three thrusters can work at a time. Fig. 2 Installation of thruster on the spacecraft 1.3 American "Dawn" ion electric propulsion system [6] In September 2007, the American "Dawn" probe was launched. Its scientific goals are to understand the conditions and processes when the solar system began to form, and to measure the mass and shape of Vesta and Ceres. As the main propulsion system of "Dawn", the ion propulsion system provides the speed increment after launch to meet the mission requirements of various stages such as orbit transfer and capture. The "Dawn" flight system structure is shown in Figure 3, and the functional module of the ion propulsion system is shown in Figure 4. Figure 3 "Dawn" flight systemFig. 3 Dawn spacecraft Fig. 4 Function module diagram of "Dawn" ion propulsion systemFig. 4 Funciton module of Dawn Ion propulsion system The initial dry weight of "Dawn" is 1 215 kg, and the ion propulsion provides a speed increment ΔV of nearly 11 km/s. The xenon tank is loaded with 450 kg of xenon propellant. The operating time of the "Dawn" ion propulsion system exceeds 55,000 hours (6 years), which is three times the longest powered flight of other spacecrafts. The ion propulsion system can provide speed increments of more than 10 km/s. During the mission cycle, the cumulative operating time of the xenon ion propulsion system is nearly 6 years. In addition, high reliability requires the ion propulsion system of Dawn to have a single-point failure redundant safety design. 1.4 ESA Mars Sampling Plan Orbital Return Vehicle Ion Electric Propulsion System ESA and NASA plan to carry out a Mars sample return mission around 2030. The orbital return vehicle responsible for Europe is scheduled to be launched in 2027. Its scientific goal is to return Mars samples to provide support for the search for signs of life, geological composition and evolution, climate change, and interaction between the atmosphere and the ground. As the main propulsion of the main body of the orbit-return vehicle, the ion propulsion system provides Mars orbit maintenance, Mars sample capture and fire-to-ground transfer speed increments to meet the mission requirements of various stages such as orbit transfer and capture. The block diagram of the ion propulsion system of the orbit-return vehicle is shown in Figure 5. The ion electric propulsion part uses four RIT-2X ion thrusters. The working strategy is to ignite three units at a time. The four units take turns to serve as cold backup to balance the remaining life. The four units can also work at the same time to increase thrust and reduce losses. Fig. 5 Funciton module of ERO Ion propulsion system 1.5 Summary By analyzing the composition of the electric propulsion system of foreign detectors, the following conclusions can be drawn: 1) The detector uses an ion electric propulsion system not only for attitude control, etc., But also for main propulsion. 2) In the design of electric propulsion systems, redundant design is very important. For example, the "Dawn" propulsion system has redundant backup functions in the configuration of key system components such as PPU, DCIU, and ion thrusters [6]. 3) During cruising flight, the electric propulsion system generally uses continuous propulsion and works for hundreds or even thousands of hours at a time. 2 Mission requirements The main task of the electric propulsion system is to provide the necessary thrust for the transfer section of the "Meteor" probe from the Earth to Mars and to provide the necessary braking force for the Mars return and Earth rendezvous. According to the planning and orbit design optimization of this slow delivery mission, the mission requirements of the electric propulsion system include the following points: 1) Speed ​​incremental requirement: 12km/s. 2) Multi-point working mode: In order to match the output power of the solar panel under different solar distance conditions, the power of the electric propulsion system must be able to be adjusted at multiple points within the range of 0.5~5 KW. 3) Continuous and pulse working modes: According to the task analysis, in addition to the pulse working mode of scheduled power on and off, the electric propulsion system also needs to have the ability to work continuously for a long time. 4) Vector adjustment: The thruster needs to be equipped with a vector adjustment device to meet the needs of vector adjustment during the mission. 3 Electric propulsion system scheme design Based on the development status of domestic electric propulsion, there are mainly ion propulsion, Hall propulsion and arc propulsion to choose from. Five electric propulsion products that have existing domestic technology foundations include 5 kW ion, 5 kW Hall, 1.6 KW ion, 1.5 KW Hall and 2 kW arc can be considered. Considering that the specific impulse of the arc thruster is only 600 s, compared with Hall and ions, the specific impulse is too low, so ions and Hall are mainly used for comparison. The main indicator parameters and current situation are shown in Table 1. Table 1 Main parameters of the thruster With the initial dry weight of the mission as 1 200 kg and the speed increment ΔV requirement of 12 km/s as input parameters, there are five main design options for the electric propulsion system: Option 1: Configure two 5 kW ion thrusters with a specific impulse of 2 580~3 900 s and a thrust of 20~180 mN. Option 2: Configure three 5 kW ion thrusters with a specific impulse of 2 580~3 900 s and a thrust of 20~180 mN. Option 3: Configure two 5 kW Hall thrusters, with a specific impulse of 2 300~2 400 s and a thrust of 134~237 mN. Option 4: Configure four 1.6 KW ion thrusters with a specific impulse of 3 000~3 500 s and a thrust of 40~60 mN. Option 5: Configure four 1.5 KW ion thrusters with a specific impulse of 1 800 s and a thrust of 80 mN. The comparison results of the above five solutions are summarized in Table 2. Table 2 Comprehensive comparison of different schemes Through the comparative analysis in Table 2, the ion electric propulsion system requires the least propellant due to its high specific impulse, and consumes more than 100 kg less propellant than the Hall of the same power; in addition, the 5 kW LIPS300 ion electric propulsion system has a propellant consumption of 1.6 The kW LIPS200 ion electric propulsion has more advantages in terms of propellant consumption, cumulative working life, and system dry weight. At present, the design life of the LIPS300 ion thruster has reached 21,000 hours, and the life test is in progress. It has completed more than 1,800 hours and is expected to complete the life verification before 2021. Therefore, the system configuration with two LIPS300s can realize a complete cold backup design of the thruster, which can ensure the long-life reliability of the system. And the same propulsion scheme as the asteroid exploration mission is used, and existing electrical experimental samples can be directly used for assembly. In summary, the electric propulsion scheme is a 5 kW electric propulsion system based on two LIPS-300 ion thrusters.

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