SpaceX has deployed nearly 600 satellite chains in the United States, which has five limitations

 SpaceX has deployed nearly 600 satellite chains in the United States, which has five limitations

The essence of star chain project

The essence of the star chain program is actually low orbit communication constellation, and its concept has been put forward for many years. Motorola proposed the concept of establishing wireless communication network by near earth orbit satellite in 1990s, and proposed iridium satellite plan. Originally, it was built by 77 satellites (actually 66 satellites), which cost more than $5billion. It can provide telephone communication services worldwide. However, since 2G network on the ground was gradually developed and mature, the number of users increased day by day, compared with that of The total number of users of iridium star program just exceeded 50000, far less than the more than 600000 users required for the balance of profit and loss, and was seriously in short of money. It was finally declared bankrupt in August 1999, and later taken over by the U.S. Department of defense.

A group of 60 star chain satellites

In terms of the principle and function of satellites, the satellite link project and the iridium satellite project are not very different. The differences between the two are: first, iridium provides users with narrow-band services such as voice communication, while star chain provides users with such broadband services as Internet connection services; second, the number of satellites in the star chain program is more, the cost of mass production is lower, and the Falcon 9 rocket is repeated The launch cost is lower.

The situation of star chain project

It is precisely because of the nature of the star link project itself as a LEO communication constellation that it will have many application limitations, as follows:

One is that portable phones cannot be directly connected. As star link satellite works in Ka, Ku and V bands, which is not the same frequency band as WiFi on daily mobile phones, so star chain can not realize direct connection of mobile phones, so special receiving terminals are needed, and cannot be integrated into current portable mobile phones, which is a huge limitation in daily use. Musk said earlier that the ground personnel can successfully enjoy the star link WiFi function after using the dedicated router of star chain.

Second, it cant be used indoors. Because satellite communication signals can not penetrate buildings such as reinforced concrete, and even rain can cut off signals when it rains, satellite phones cant receive satellite signals normally indoors, which is another huge limitation in daily use. Signals must be introduced into the room through external special satellite antennas with the size of about 0.48 meters, which are installed on the roof or outside the house, and need to be aligned Wide sky

Third, the communication delay is still not low enough. Since the satellite chain satellite is a low earth orbit satellite with an orbit altitude of 340km-1300km, it is closer to the ground, and the signal transmission delay can reach 15ms-20ms, which is equivalent to the level of wired internet. Although the 250ms delay of geosynchronous satellite with orbit altitude of 6000km is less than an order of magnitude, it is still far higher than the 1ms delay of ground-based 5g wireless communication. For unmanned driving, the delay is more important Harsh application scenarios cannot be applied, and can complement 5g network to realize interconnection and global coverage.

SpaceX launched the star chain satellite using the Falcon 9 rocket

Fourth, the number of high-speed communication users is limited. The design bandwidth of a single satellite of star chain is 17-20gbps. After all 42000 satellites are deployed, the total bandwidth will be 840000 Gbps. If calculated according to the 5g entry standard, 1Gbps, it can only be used by 840000 users at the same time. If it is reduced to 100Mbps of 4G standard, it can be used by 840000 users at the same time. This means that it can only be provided to some or high-end users around the world, but not all of them Popular communication network within the sphere.

Fifth, the financing pressure and profit challenge are enormous. From the cost perspective, the total number of launch of the star chain program is huge. The cost of a satellite is about $1 million, and the cost of 42000 satellite lights is $42billion. According to the ideal situation, the Falcon 9 rocket is reused 10 times, the single launch cost is $10 million, and the 700 launch costs about $7 billion. In addition, the deployed maintenance, and regular expansion of network and replacement of satellite are also included Star, which conservatively estimates that the development, deployment and maintenance of the whole star chain plan will cost more than $1000-200billion. It is a question whether SpaceX can finance enough funds to support such high-cost investment. In the case of such huge cost, how to make profit becomes a problem. As shown above, star chain has various application restrictions, which is destined to be unable to become a daily communication network for the general public around the world. The main user group is still the U.S. military with a few users with special communication needs. The first lesson is in front of us. Oneweb has become the most powerful competitor of mask at the beginning of its establishment, and it also realizes the wireless communication between the world and the earth through satellite networking. However, after launching 74 satellites and spending more than 3 billion dollars since its inception, there is still no profit on the book. In addition, the outbreak has affected new financing hopelessly. In March, it has declared bankruptcy. 650 satellites originally planned were launched The shooting plan was also stranded.

There is a long way to go. Although the star chain project is in progress, we have to see that there are still many limitations and challenges in the development process of the star chain project. China should also face up to the advantages and limitations of the Leo Internet satellite constellation program, speed up the deployment of LEO communication constellation to meet the needs of Chinas development, and catch up with powerful countries in the new round of information network technology competition.

(function(){( window.slotbydup=window .slotbydup||[]).push({id:u5811557,container:ssp_ 5811557, async:true }Source: Cui Yuwei, editor in charge of global network_ NBJS11349