When it comes to the word “core”, people who don’t know it may turn pale. But they don’t know that, if used properly, nuclear energy can be reasonably used in many places. For example, in the field of aerospace, in the 1970s, there were isotope batteries (i.e. nuclear batteries) on Mars probes. After 40 years of development, nuclear battery technology has become more and more mature. However, compared with the lithium batteries that can be seen everywhere in daily life, the development of nuclear batteries is not as fast as expected, at least in mobile phones, computers and other electronic devices, they have not been found. However, from the perspective of safety and performance, nuclear batteries have great hope to be commercialized in the future and even enter our daily life. Presumably, it will also slowly change the world like the innovative technologies of autonomous driving and VR. < p > < p > on January 3, 2019, chang’e-4, which has been in space for nearly a month, landed successfully and began to explore the back of the moon. Like its predecessor, chang’e-3, chang’e-4 has built-in nuclear batteries as part of its energy supply. Nuclear batteries are nothing new in the field of aerospace. As early as 1961, nuclear energy has been used in space. Voyager-1, an unmanned outer solar system space probe launched by the United States in 1977, is still drifting in the universe until now. In the past 43 years, the only power to support its normal operation is the three nuclear batteries inside. < / P > < p > here we want to briefly explain the operation principle of nuclear cells. Nuclear cells mainly rely on the decay of radioactive elements to generate heat, and then use thermoelectric materials to convert heat into electricity. In the nuclear batteries of spacecraft, the radioactive element basically refers to plutonium-238. < p > < p > the curiosity Mars probe launched by the United States in 2011 also uses nuclear power. It is reported that curiosity Mars rover uses plutonium-238 decay heat for thermoelectric conversion, with a design life of more than 40-50 years. However, during China’s recently launched “tianwen-1” mission, there was no nuclear battery in the Mars probe. Why is this? The energy conversion efficiency is one of the most important factors. The energy conversion efficiency of plutonium-238 nuclear battery is less than 10%, which is not high. If we want to carry out long-term exploration, we must increase the weight of the battery or carry more plutonium-238, which will increase the cost and the load of Mars probe. The estimated detection time of tianwen-1 mission is only three months, and there is not much experimental equipment to carry. Only solar energy is needed to meet the demand. In addition, plutonium-238 is a high-level radioactive material, and a small particle of dust inhaled by the human body may cause fatal cancer. Considering that China is the first time to launch a Mars probe independently, any problems in the launch will cause great safety risks (similar events have occurred in the United States before, leading to the release of plutonium 238 into the atmosphere.) < p > < p > chang’e-4 is also equipped with solar cells as the main power, and nuclear cells play a special role in it. The moon alternates day and night every half a month, and the temperature difference is as high as 300 ℃. At this time, the nuclear battery plays a role of “keeping warm”. It uses the heat energy emitted by itself to maintain the communication with the ground. When the day comes, the solar cell drives the detector to work. < p > < p > the requirement of nuclear battery in aerospace field is to provide enough energy, so there are not too many restrictions on volume and radioactivity. When nuclear cells are used for commercial purposes, these two points must be taken into account. Different from the principle of generating thermal energy into electricity, beta voltaic batteries mainly use the beta decay of isotopes (such as tritium, or hydrogen isotopes). It is worth noting that the penetration depth of beta decay is very shallow, ordinary paper can block it, and there is no radiation damage. In fact, there are some civil products using tritium for power generation. For example, we often use safety exit signs in cinemas or indoor fire passages, and the interior is illuminated by tritium. If you search for “tritium” in some treasure now, the results are all luminous tritium tubes, and the price ranges from tens to hundreds of yuan, which has no practical value. < / P > < p > but it’s not totally useless. Similarly, a tritium battery appeared in 2012 in a certain treasure. It is said that it has been continuously electrified for 20 years without charging. The price of a small battery has reached nearly 7000 yuan, which can be said to be a sky high price. The battery, called nanotritium, is not a fake product, but the first commercially available tritium battery from the U.S. company City labs. In the 1970s, Mr. olsen-147, the director of the battery, has been designing a nuclear pacemaker based on the research of the battery. However, the problem with Pm-147 is that although it belongs to beta decay, it will release gamma rays with strong radiation during the decay process, so betacel needs to make a lot of space inside the battery to shield radiation. Finally, because the “cost performance” is not as good as lithium batteries, it gradually withdrew from the stage of history. Peter cabauy, CEO of city labs, said earlier in an interview that beta volt battery technology is on the rise again because semiconductor materials have made great progress. “Early semiconductor materials were not enough to convert electrons from beta decay to usable current.” < / P > < p > based on the progress of semiconductor material technology, some enterprises around the world are also determined to commercialize nuclear batteries, and these “playing with nuclear” companies are gradually emerging. < / P > < p > as the most likely commercialized nuclear battery technology, various countries in the world are carrying out research on beta voltaic battery. Because the technical threshold is relatively high and there are relatively few enterprises, the city labs mentioned above is regarded as the “ancestor” in the tritium battery research industry. Widetronix, another tritium battery company, has announced the manufacturing principle of the battery, which consists of a metal foil impregnated with tritium and a semiconductor silicon carbide sheet. The silicon carbide sheet can convert 30% of the particles that hit the foil into an electric current. When widetronix stacks them into a package one centimeter square and two tenths of a centimeter high, it’s a tritium battery. < p > < p > the company from Shanghai is also engaged in the research and development of nuclear cells, which is also based on the principle of bombarding thin-film materials with β – electron flow released from tritium gas. However, the photoelectric effect between electrons and ultraviolet light is generated by purple energy, which converts light energy into electric energy. < / P > < p > “this method can greatly increase power and is used in some common products.” The company said in an interview with ID: geekpark. As for the company’s use of which materials, Zidian energy did not disclose. < p > < p > if the nuclear battery is put into civilian level, the beta volt battery has obvious advantages and disadvantages. The half-life of tritium is 12.5 years, so the product life can be maintained for a long time without charging. On the issue of battery safety that people are most concerned about, beta volt battery has a wider temperature range than lithium battery, which is the biggest advantage of nuclear battery. < / P > < p > both city labs and widetronix claim that after testing at Lockheed Martin, a well-known defense contractor, the battery has undergone a thermal cycle from – 50 ° C to 150 ° C without degradation. However, compared with the lithium battery and other chemical batteries, the disadvantage of beta volt battery is that the output power is low, which is also the problem that purple power wants to solve. The power produced by widetronix is 1 MW (μ w), which is 0.000001 W. An ordinary smartphone (at 3.7V, 2000mAh) also uses hundreds of milliwatts (MW). < p > < p > purple power is trying to make a rechargeable battery based on tritium gas, and has entered the stage of small batch trial and verification. According to Geek Park, Zidian has started to set up factories and production lines, and the power bank products are expected to enter mass production next year. “The product performance can reach 12V1A, completely consistent with the current power bank.” Zidian Energy said. < / P > < p > if the power bank products can be successfully mass produced, it will be a big breakthrough for the nuclear battery industry. Because of the characteristics of the beta volt battery, it can be used in very limited scenarios. According to the official website of city labs, the beta volt battery is the perfect choice for long-term, low-power, and highly demanding devices with continuous power supply. Therefore, defense electronics, sensors, aerospace, medical equipment and other scenarios are the current beta volt battery in the field of capture and application. < / P > < p > it is not difficult to foresee that the direction of technology development is to be civil, and the most daily things will change as a result. It is this technology that can have the most profound impact. In the same way, the relatively limited application fields correspond to a small number of scenarios, and some companies are carrying out relevant research on mobile phones, UAVs, new energy vehicles and other more general-purpose industries. < / P > < p > imagine that if the mobile phone manufacturers abandon the advertisement of “charging for 5 minutes for X hours”, and confidently say that the mobile phone will not be recharged for 10 years; if the batteries inside the electric vehicles can maintain high performance, and there is no need to charge or replace them for nearly 10 years, the subversion of these industries which have existed for many years will be immeasurable. SpaceX beat blue origin and Northrop Grumman to win a $316 million air force contract