Do you want WiFi or starry sky? Musk's "Star Chain" plan caused controversy
Journalist / Peng Danni
Issued in 2020.5.18 total issue 947 "China News Weekly"
On April 27, astronomy enthusiasts noticed that a series of satellites glowing due to reflected sunlight rose from the northwest at 8:37 that night and crossed the Beijing night sky; on the evening of May 1, these satellites passed through Xiamen , 40 satellites visible to the naked eye lined up ... Starting in 2019, SpaceX of the United States sent several batches of "Starlink" satellites into space through a rocket launch carrying 60 satellites. Since then, astronomers have discovered that these satellites travel across the world like a train.
This is another masterpiece of "Silicon Valley Iron Man" Elon Musk. The founder of Tesla Motors has frequently shaken people's cognition. His vision of future lifestyle involves many fields such as transportation, energy, payment, and brain-computer interface, but aerospace is undoubtedly the most ambitious layout among them.
SpaceX, a commercial aerospace company founded by Musk in 2002, successfully launched rockets in six years. It took less than 16 years to create the world's most active carrying capacity and recoverable rockets. In the future, he plans to build giant rockets that can send humans to Mars-but before that, he wants to use rockets to do another thing: network and communication signals covering the whole world.
Satellite communications: network coverage without dead ends
On February 22, 2018, at Vandenberg Air Force Base in California, SpaceX successfully launched a "Falcon 9" rocket and put two small experimental communication satellites into orbit-this is Musk's ambitious Global Internet satellite deployment plan-"Star Chain" project started.
Each Starlink satellite weighs 227 kg and is about the size of a car. It consists of a plate-shaped satellite body and a foldable solar panel. Each satellite is equipped with 4 phased array antennas for network services. The advantage of low-orbit satellite communications is fast. On the one hand, the signal propagation speed of the star chain is close to the speed of light of 300,000 kilometers per second in the vacuum, and the propagation speed of the optical signal in the optical fiber is 200,000 kilometers per second. They are connected piece by piece, but directly point-to-point, so this communication method is more efficient even when considering round-trip air-ground.
In May 2019, the first 60 satellites launched by Starchain entered a 550-kilometer low-Earth orbit, followed by the second and third launches in November 2019 and January 2020, respectively ... On April 22, 2020, the "Falcon 9" rocket was launched from the Kennedy Space Center base in Florida, sending the seventh batch of 60 satellites into space. So far, including the aforementioned two experimental satellites, the Starchain project has launched 422 satellites.
According to the latest timetable given by Musk, he decided to launch satellite Internet measurement when 420 satellites were completed-currently, they are using these satellites in North America and Canada to conduct some private network tests and larger public tests. It will start in November 2020. According to SpaceX's plan last year, in 2020, the Starlink satellite will be launched at least 9 times, and may reach up to 24 times, that is, almost every two weeks.
According to a document submitted by SpaceX to the Federal Communications Commission (FCC), "StarChain" plans to deploy 12,000 satellites by 2027, located in three layers in low-Earth orbit-7,500, 1,584, and 2,825 satellites They are located on the orbits of 340 kilometers, 550 kilometers and 1150 kilometers from the ground, respectively. In October 2019, SpaceX submitted a frequency application for a new batch of satellites, planning to add another 30,000 satellites to operate between 328 and 580 kilometers, bringing the total number of satellites to 42,000.
Musk promised a tempting goal: the Starchain project will provide complete global coverage through a large number of low-orbit satellites. By then, no matter whether it is in the inaccessible mountains and rivers or the vast sea, it can receive high throughput and low Delayed internet communication network signal. In terms of network speed, StarChain provides broadband services of at least 1Gbps / sec-this speed is more than 30 times that of current home broadband, and ultra-high-speed broadband networks of up to 23Gbps / sec. At that time, consumers only need to buy SpaceX terminal equipment, spending tens of dollars a month to enjoy this network.
Young aerospace scholar Mao Xin is currently engaged in post-doctoral research in the fields of low-orbit satellite precision orbit determination and satellite navigation systems. He told "China News Weekly" that now urban residents can enjoy convenient and fast network services with very little money, so this type of communication satellite will not impact the existing fiber optic network and 4G / 5G and other basic communication networks, but make up Places that cannot be covered by traditional communication methods, such as cargo ships in the ocean, passenger planes in the sky, special stations such as the North and South Arctic Research Station.
Among the top ten breakthrough technologies in 2020 recently released by the US MIT Technology Review, large satellite networks occupy one of the seats. Major players in this field include technology companies such as SpaceX, OneWeb, Amazon and Telesat. The journal believes that the impact of large-scale satellite networks in 2020 will be highlighted this year. At the same time, astronomers and experts concerned with space traffic control may become more and more worried and complaining about the negative effects of these huge satellite networks.
Committed to "not bankruptcy"
In early 2015, two space entrepreneurs announced their entry into the satellite Internet business in the same week: one was Elon Musk, and the other was Richard Branson, chairman of the British Virgin Group. It was OneWeb, which later became a rival of Starchain.
The MIT Science and Technology Review believes that, unlike in the past, which was motivated by showing national strength and prestige, pragmatism is now driving the development of space. According to estimates by the US Department of Commerce, the value of the space market has reached US $ 325 billion, and may exceed US $ 1.5 trillion in 20 years. Many other services such as communications infrastructure, space tourism, space mining, etc. marked by the "Star Chain" project have potentially huge profits.
On the satellite industry track, an important application scenario is communication. The biggest problem with traditional satellite signals is delay. This is because most communication satellites are in "geostationary orbits" 35,786 kilometers from the earth's equator. This distance is enough to cause a delay of more than half a second.
"High-orbit satellites are too far away from the earth, so the signal is very weak when they reach the ground. When high-bandwidth data such as the Internet or watching video, a ground antenna of at least 3 meters is required to receive the signal." Jonathan Mac, astrophysicist at Harvard University Doyle told China News Weekly.
Mao Xinyuan explained that there are still many barriers to high-orbit satellites, especially geostationary orbit communications satellites. On the one hand, these satellites weigh a few tons, have high technical content and are very expensive, so there is a high technical threshold. On the other hand, these orbits are the most valuable orbits for human spaceflight. The number of satellites deployed will be strictly limited and distributed. Dense satellites can also interfere with the signal.
Under such circumstances, the low-orbit satellite Internet with a large number of satellites and high signal strength has become a hot topic in the aerospace field in recent years. Mao Xinyuan said that satellite Internet has high commercial value. In addition to being used for communication, it can also participate in navigation and positioning. By assisting high-orbit satellites such as the Beidou system to improve positioning accuracy, it can also be used in manned spaceflight and Play a role in scientific projects such as exploration, meteorological research and remote sensing. But because a low-Earth orbit satellite can only be responsible for a small part of the Earth's communications, many satellites are needed to achieve global coverage.
As early as the 1990s, some companies began to get involved in space Internet projects. The former communications giant Motorola of the United States proposed the "Iridium Project" in 1987, and had launched 66 satellites.
Mao Xinyuan said that in the 1990s, a rocket was launched for about 30 million US dollars, but the number of satellites launched was only a few, which is completely different from the current practice of carrying 60 satellites at a time. Under such high costs, in order to maintain operations, Iridium charges are much higher than expected, and the number of users drops sharply, and finally the project goes bankrupt. During the same period, the Teledesic project supported by Bill Gates also filed for bankruptcy protection in 2002 after soaring costs and the exhaustion of investor funds, when Teledesic launched only one satellite.
Now, the cost of satellite Internet projects is declining steadily with technological improvements such as mass production and recyclable rockets. Mao Xinyuan settled an account. According to SpaceX's previously mentioned manufacturing cost of 1 million US dollars per satellite, with mass production, a satellite costs 500,000 to 1 million US dollars; the most expensive cost comes from launch, but because SpaceX uses its own manufactured rocket, and can be recovered Therefore, the total cost of launching 60 satellites at a time is about 30 million US dollars, plus the launch site, supporting facilities, etc., he believes that their average cost of launching a satellite is currently between 1.5 million and 2 million US dollars.
But until now, this is still a cruel business field. At the end of March of this year, OneWeb filed for bankruptcy due to the breakdown of $ 2 billion in funding negotiations with Softbank. At the time, there were 74 orbiting satellites in the project.
"Guess how many low-orbit satellite internets haven't gone bankrupt? Zero." At a meeting in March this year, Musk joked that SpaceX is currently working on "non-bankruptcy" in light of the lessons learned from those bankrupt projects.
Gwen Shortwell, president and chief operating officer of SpaceX, revealed in an interview in 2018 that the total cost of the Starchain project was approximately $ 10 billion. According to Morgan Stanley, a well-known investment company, an additional 30,000 satellites may cost SpaceX $ 60 billion.
How to raise this fund is a difficult problem. According to the US Wall Street Journal reported in March this year, the FCC allocated $ 16 billion in funds to improve Internet services in rural areas within the next 10 years. SpaceX hopes to apply for the funds. However, bidders believe that giving the funds to SpaceX is a gamble. A former FCC official said: We do not allow people to speculate with public funds.
Starchain is "obtrusive"
In May 2019, when the first 60 satellites planned by StarChain were launched, a discussion of business ethics triggered: a company unilaterally changed the appearance of the sky, as well as the actual light pollution and space debris. influences.
According to the latest data from the United Nations Satellite Registration website, there are currently about 2,000 artificial satellites still in orbit. Even if Star Chain is in accordance with the previous plan of 12,000 satellites, it will increase this number by 6 times. In similar projects, "Star Chain" is not the only participant. So many satellites are competing for the natural starry sky, which has caused a lot of criticism in the astronomy community.
A frequently cited example is a large integrated sky survey telescope worth $ 466 million, 8 meters wide and equipped with a 3.2 billion pixel camera, originally intended to quickly scan the sky in the 1920s. However, with the formation of the Starlink Satellite Group, many of the images taken with this telescope were "contaminated" by it, and the photos taken by long-term exposure may contain dozens of satellite movement trajectory stripes. The large survey telescope simulated the impact of the future 42,000 star-chain satellites on observations and found that 30% of the images would contain at least one satellite trajectory.
SpaceX has also given some solutions to this. On January 6 this year, SpaceX launched a "dark star" to test the effect of reducing the brightness by blackening the surface of the satellite, but the measure still does not meet the requirements of a professional observatory. SpaceX engineers also proposed the idea that each satellite could be equipped with a parasol to prevent reflection of sunlight, but it has not yet been verified. In a file submitted to the FCC in April, SpaceX revealed that it is working on new methods to reduce the brightness of the satellite and will test it in the coming months. In addition, the company will provide satellite tracking data so that astronomers can better Coordinate observation activities.
Astronomer Ronald Dremer of the Astronomical Observatory in Turin, Italy, pointed out in an email to China News Weekly that if the satellites are invisible enough to be caught by the naked eye, it will be a huge Improvement, because it can make satellite image data easier to handle, and protect the desire of the earth to look up at the sweeping night sky. However, the parties have not yet reached an agreement on how to resolve this issue at the practical and political levels.
Space junk is another concern. SpaceX said that each Starlink satellite will be able to track debris in orbit and automatically avoid collisions, and will automatically leave orbit after reaching its lifespan and be burned to the atmosphere. However, Gou Lijun, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, and others recently wrote that if these satellites are damaged in orbit or fail to spread out, they will still pose serious problems. In the first batch of star chains launched in May 2019, three satellites lost contact and could not be actively controlled, thus forming space junk.
In June 2019, the International Astronomical Union (IAU) issued a statement expressing its concern that such projects may disrupt the natural sky and interfere with the frequency of radio astronomy. In the statement, the association described this space frontier as "new , And basically unregulated. "
Many interviewed experts believe that since no one thought that the number of satellite launches will grow so fast, regulation has not kept up with this nascent field. Ronald Dremel bluntly said that in terms of the visible impact on the sky, the supervision of such projects is completely absent. He believes that the reason why SpaceX is moving so fast is partly because of the use of the current regulatory vacuum to maximize the opportunity before the rules appear.
Another question is, do communications satellite projects need to be so large? OneWeb founder Greg Weller believes that the only reason to launch more satellites than actually needed is to show off. "The number of satellites makes a company. From a public and fund-raising perspective, more is better."
"China News Weekly" No.17, 2020
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