There were Falcon series launch vehicles from SpaceX before, and China’s Long March 11 rocket recently. These rockets made on the earth all run to the sea to launch. Is it because the land is not big enough, or is there any magic in the sea? On September 15, the Long March 11 launch vehicle was successfully launched. According to CCTV news reports, the launch of the “Jilin No. 1” high score 03-1 satellites was successfully launched into the scheduled orbit by using the “one arrow and nine satellites” mode. < p > < p > the satellites launched this time consist of three video imaging mode satellites including the “central video” satellite and six push broom imaging mode satellites. After the failure of the last launch, bilibilibili video satellite has finally been successfully launched. The satellite is mainly used to obtain high-resolution visible light push broom images and video images, and will provide remote sensing services for China’s land and resources census, urban planning, disaster monitoring, etc. < / P > < p > in addition to the satellite array, the launch site is worthy of attention. The launch site was not located in the four conventional launch centers (Jiuquan, Taiyuan, Xichang, Wenchang), but was launched in the Yellow Sea. Coincidentally, SpaceX CEO Elon Musk, who is on the other side of the ocean to eventually push the rocket to commercial use, also said in August that “the ocean space port is the future of starships and their launch vehicles.”. < / P > < p > one of the advantages of the sea over land is that it can be closer to the equatorial region at low latitudes, which means that the earth’s rotation speed can be used to improve the rocket’s carrying capacity. < / P > < p > due to different latitudes, the linear velocity (sectional velocity) of various parts of the earth’s surface will change, and it is inversely proportional to latitude. This can be understood that under the condition of constant angular velocity, people at all latitudes have the same time to rotate with the earth, so the longer the circumference of low latitude areas, the faster people “run”. This “running speed” can be understood as linear speed. The linear velocity on the surface can be regarded as the initial velocity possessed by the rocket. The larger the initial velocity, the less propellant fuel is needed for the rocket to reach the target speed, so the launch capacity of the rocket can be improved. < / P > < p > on the other hand, offshore launch platforms are easier to move on a large scale. Because of the existence of the high sea, in theory, any country’s rocket launch can be carried out close to the equator, so the sea scene becomes one of the breakthroughs to enhance the upper limit of rocket launching capacity. < / P > < p > in addition, sea launch is conducive to special orbital missions. For example, in order to meet more complex commercial uses, small inclination satellites have been paid more and more attention. According to Jin Xin, deputy commander-in-chief of the Long March 11 launch vehicle, the launch of the rocket near the equator can avoid the energy consumption caused by the change of satellite orbit inclination, and can improve the rocket’s carrying capacity and service life at the same time. < p > < p > after the rocket takes off, the booster will fall out of fuel. Worse still, if the rocket fails to launch, it will fall back to the ground. Therefore, the safety of landing area is an important factor in rocket launching mission. As a result, launch bases are often located in sparsely populated areas. Taking the four launch centers in China as an example, Jiuquan and Taiyuan launch centers are located at the edge of Gobi desert and desert respectively. Xichang and Wenchang launch bases are located in the hinterland of Daliang Mountain, and the latter is close to the sea. The four places are all low population density areas. < / P > < p > the sea surface is no different from a no man’s land for rocket launching, and the control of landing area position can be more tolerant in mission design. Some of the world’s major launch bases, such as the Western space and missile test center in the United States and the Plesetsk base in Russia, are all set up in coastal locations, and the launching direction is facing the sea area. All of them are for the consideration of third-party security. < p > < p > if the rocket launch is put into commercial use on a large scale, it will even become a vehicle in the future. Then the huge noise during launch is also one of the factors to be considered. Musk’s idea of using SpaceX is to launch 1000 missions a year. In an interview earlier, he said that in the future, starships may be launched mainly from the sea, mainly because of frequent take-off and too much noise. < / P > < p > in the process of space launch around the world, a set of “weather launch commit criteria” needs to be strictly observed. There are strict requirements for avoiding cumulus, thunderstorm and other weather conditions. Earlier this year, the SpaceX manned space launch was initially delayed due to weather. However, compared with land, the local natural environment at sea is more changeable and more difficult to predict. The probability of thunderstorm on the sea is high, and it has the characteristics of high salt fog. The former will interfere with electronic equipment, while the latter will corrode the exposed equipment surface. In addition, the high concentration of mold on the sea will cause the mildew of organic materials and short circuit of electrical components. < / P > < p > in the mission history of the US space shuttle, nearly half of the delayed launches are related to weather factors. “Unpredictable weather” is the biggest variable of sea launch. The selection of launch vehicle equipment and launch scheme need to be adjusted according to the marine environment. At the same time, because the water surface is different from that of the land, the launch platform needs to achieve long-term course keeping, dynamic bearing transfer and other moving base aiming technology research and experimental verification. In order to ensure the safety of personnel, all of these need remote control, and unmanned launch is needed on the platform. This is also the technical difficulty of marine rocket launch in the face of harsh natural environment factors. 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By ibmwl