Let's introduce a little background before discussing it in detail. Outernet website mentioned that they intend to learn from the design of CubeSat, an open source satellite whose square is 10cm, so as to quickly develop usable satellites. Because of the grass-roots nature of the project, I think they will also put the satellite in the lowest near-earth orbit-the lowest metastable orbit is 160km, and it can't be lower or the satellite will crash soon. In addition, it is easy to misunderstand. Several friends pointed out that the main purpose of Outernet is to receive one-way information broadcast with existing WiFi devices, rather than surfing the Internet.
Applying IDEO's theory, without these three elements, any innovative project can't be successful:
Technical feasibility (technical feasibility)
Economic sustainability (financial feasibility)
Meet the market demand (market demand)
After careful analysis, if Outernet project wants to succeed, it will have to overcome too many difficulties in these three aspects.
First of all, talk about the technical feasibility.
Lost connection: Because of the long transmission distance, the mobile phone can't receive the satellite signal at all. This was mentioned by @ 京京京京京, but it is not clear how he got it. I assume here that in an ideal situation, there is no air to absorb electromagnetic waves, and there is a way to magically fold a giant parabolic antenna with a diameter of 1 m (24dBi gain) on this satellite. Then, the signal emitted by a WiFi satellite transmitter with full power of 100 MW(20 DBM) will reach the ground after a long journey of 160km. Because the antenna gain of mobile phones and notebooks is pitifully small, the signal intensity that the mobile phone WiFi chip can see is only about-100dBm-in this case, the mobile phone can't receive data correctly at all (most mobile phones need at least -80dBm to barely work)-and all these calculations are made under ideal conditions, taking into account factors such as air loss, non-shortest propagation path, building tree occlusion, multipath effect and so on.
Satellite power consumption: the power supply of the satellite is not enough to increase the transmission power to make up for the link loss. Obviously, due to the grassroots nature and volume limitation of the project, it is impossible for the satellite to carry advanced power sources such as nuclear fuel cells, and it can only work by solar panels. At present, the most successful panel in space can only generate 300W/sqm power, which is equivalent to the area of cube satellite. Assuming that one side is facing the sun all the time, it can only generate 3W of electricity-this poor electricity is barely enough for the controller, memory and WiFi circuit. Moreover, it is not feasible to simply increase the power of the electric plate. To take a step back, even if the satellite magically folds out 1 square meter of solar panels (almost turned into transformers! ) and can effectively generate 300W of power. Ideally, we can only ensure that the open-air mobile phones on the earth barely work. This has not taken into account the efficiency of WiFi power amplifier, the satellite needs complex attitude control circuit, and the satellite will enter the earth's shadow and other factors. The most terrible thing is that in space, so much heat generated by satellite work cannot be easily eliminated, and the satellite will soon overheat and die!
Coverage: Satellite coverage is too small, the number is too small, and the speed is too fast. A parabolic antenna with a diameter of 1m on the above satellite can only cover a circular area with a diameter of about 20km (about 7 degrees) on the earth's surface. Even if it covers the area of1100 in China's 9.6 million square kilometers, it needs 76 satellites! I wonder how Outernet claims that 150 satellites cover the whole world. This is not the whole problem. The speed of this low-earth orbit satellite is about 7.8km/s (the first cosmic speed), which means that the mobile phone can only receive the data of one satellite for 3 seconds, so it needs to be dropped or switched to the next satellite. I find it hard to believe that the broadcast data of the next satellite can be seamlessly connected with the last satellite.
Data distribution: technical difficulties have not been overcome. Outernet mentioned that using WiFi multicast to send data requires the mobile phone to register on the satellite, and two-way communication must be established between the mobile phone and the satellite-the satellite can't hear the uplink because the power of the mobile phone is much lower. Even if a giant antenna with a diameter of 100 m is installed on the satellite, the weak signal sent by the mobile phone is drowned by other co-frequency interference. What's more, due to the long distance between the satellite and the mobile phone, the two-way communication will have the problem of ACK timeout. The current WiFi can only communicate at a distance of about 15km without modifying the protocol.
Secondly, let's look at the sustainability of the economy. (Because official website said that they can get a tax refund, I assume that they are non-governmental organizations for public welfare rather than commercial operations).
Satellite cost: Even if a cheap satellite like CubeSat is launched to the lowest LEO, the comprehensive cost of each satellite is 65,000 US dollars, which is equivalent to the price of a BMW, so the cost of 150 satellites is nearly 60 million RMB. This does not include any expenses for operation, research and development, publicity and financing. I wonder whether they can raise so much money. Maybe many people will donate to them with their eyes closed, but at least I won't donate until they convince me technically.
Satellite life: Although the launch cost of satellites in near-Earth orbit is low, their life span is short. Because the air density in low-earth orbit is much higher than that in outer space, the satellite will gradually slow down and fall back to the earth under the action of air resistance. In this environment, the corrosion of free oxygen atoms leads to short satellite life. For example, most of CubeSat mentioned above have a service life of less than 2 years, which means that 30 million RMB is invested every year to maintain satellites that have fallen or failed! Even assuming that the service life of the satellite can reach 6 years, the most optimistic estimate is that the annual maintenance cost will be100000, and raising funds is no small problem. In fact, small open source satellites, such as CubeSat, are more suitable for short-term scientific research than long-term commercial or non-commercial operation.
Donation method: At present, it seems that donations go directly into the founder's account without third-party supervision. I don't know how long this untrustworthy donation model can be repeated, and how long will it take them to support the first satellite launch with a donation of 10?
Finally, even if the above technical and financial difficulties are solved, what kind of people will use services like Outernet?
Areas with communication infrastructure: They have a variety of means to obtain information, they can easily access the Internet, and even sensitive information can be obtained by climbing over the wall. I can't think of enough reasons for them to spend a lot of time getting information from Outernet, a service with unstable connection and narrow information content, which could have been obtained by more convenient means. For example, the information that Outernet can provide is listed in the screenshot of @Norman Karma, which can basically be obtained without climbing the wall. It can be said that all your friends who can go to Zhihu are not the audience of Outernet.
Areas without communication infrastructure: if you are a high-end crowd in field investigation and exploration, except for a few reckless travelers, you must be able to afford satellite phones as a means of communication; If they are isolated aborigines in some areas, who will send them mobile phones or computers and teach them to surf the Internet? Dear friend, I guess the girl below may be an important customer of Outernet. You must be willing to give her a mobile phone in person and teach her how to get to the Internet cafe.
Looking back, the enthusiasm of the founders of Outernet is commendable, but there are too many negative examples in front of them. In fact, there have been countless similar ideas before, but this time it was changed to WiFi, which reduced the demand for terminals. Martyrs club:
Teledesic, 288 LEO satellite, supported by Microsoft venture capital, launched an experimental satellite and went bankrupt in 2002.
Tianqiao, 32 geosynchronous satellites and Alcatel disappeared completely in 2002.
Celestri, 63 satellites in low Earth orbit, Motorola, was abandoned in 1998.
In contrast, Google Loon, which is suspended at an altitude of tens of kilometers, is at least technically more mature and can provide two-way Internet services, although its business model is unclear.
Conclusion: This is really an ambitious project. Whether the result is successful or not, it will be a positive contribution to the freedom of human access to information. The detours of success and failure will also give many lessons to future generations. However, it seems very pessimistic at present. Judging from the official forum, the founders simply don't understand or pretend not to understand the difficulties they encounter.
In fact, Zhihu, which has great dreams, also has many problems, but I still want to remind the owners that no matter how great their innovative ideas are, please look back at similar projects in history. There is a saying that has been said ten thousand times. Please repeat the following words with me-of course, this time I hope I am wrong about Outernet.