Starlink : Une constellation révolutionnaire ?

4408 is the number of these satellites that should make up SpaceX’s Starlink constellation at the end of 2022. They may seem like nothing these satellites but they could well be at the origin of a small revolution in the telecommunications field. And the company will not stop there since it plans to launch a new constellation of 30,000 satellites in phase 2 of the project, to the chagrin of astronomers. This mega constellation will aim, among other things, to connect the most remote places on the planet by broadband. But let’s take a step back. It was in January 2015 that Elon Musk announced SpaceX’s intention to enter the telecommunications market by developing a mega constellation of low orbit satellites.

01:12 - This announcement comes very shortly after one from OneWeb which is working on a similar project. A large part of the planet does not have high-speed internet access, and the company that manages to offer this kind of service first would thus secure a large share of the pie. A cake that could also help finance the dreams of some space entrepreneurs for decades to come. This year alone, the FCC, the United States Communications Commission, plans to fund nearly $ 16 billion for the provider that will be able to provide a decent connection to the most remote places of the country by the end of 2020. But despite this very promising market, still few companies plan to launch out there, so much a sufficiently powerful constellation , requires considerable investments. And I’ll try to explain why.

01:58 - To try to understand how the constellation works, we will take the GPS constellation as an example. The network is made up of around thirty satellites, almost 150 times less than Starlink, which emit a signal but do not wait for a return from the ground. Indeed, it is then up to your phone to do the trigonometric calculations between the different satellites to determine your position. The satellites of the network are placed at an altitude of 20,000 km in order to optimize the coverage So that at any time, whatever your position on the planet You always have at least 4 satellites visible in the sky. Why not do the same with Starlink? Because the internet works on a system of requests that we send to a server and then return a response to us.

02:37 - The proximity between the satellite and the receiver is therefore crucial. A radio signal traveling At the altitude of the GPS satellites, i.e. 20,000km, it takes approximately 130ms for the signal While in low orbit, it is of the order of 2 or 3ms . one of the reasons why the constellation’s satellites are in low orbit. But that is only part of the problem. Orbital mechanics implies that the closer a satellite is to Earth, the higher its speed. Indeed, at an altitude of 550km, the satellites move at 7.5km / s In other words, when the orbit is favorable, the satellite appears on one side of the horizon and disappears on the other side. in less than 5min. In this case, the only way to get a stable connection is to dot the sky with hundreds of satellites to make sure we always have one above us. And this is exactly what is planned with Starlink The last request to modify the constellation to the FCC dates from April 17, 2020. It gives us a good idea of ​​the form that phase 1 of the constellation will take with its 4408 satellites Distributed as follows: Looking at the constellation, we quickly realize that a network optimized for North America is also able to cover a large part of the planet.

04:20 - While the network is initially intended for the US market, it is indeed a question of extending it internationally once it has been tested in the national territory . All this will however be submitted to the local frequency regulator. SpaceX has already started to take certain steps, such as in Australia, Canada, the Netherlands, Great Britain and even in France where companies affiliated with SpaceX have appeared. Camouflaged under the name TIBRO LTD or TIBRO CORPS, they applied to become a telecommunications operator in each of these countries. An article on this subject written by Eric Bottlaender and yours truly is available in the description.

04:59 - But SpaceX will not stop at this constellation, it is indeed planned a phase 2, composed of 30,000 satellites which will be distributed between 328 and 614 km of altitude. As much to say to you that it will be a happy mess up there! 30,000 satellites is an astronomical volume since today there are slightly less than 2,000 satellites in low orbit. We can therefore predict that this kind of constellation could cause a good number of problems, in particular the risk of collision. The latest example, in 2009 two satellites collided, Iridium-33 and Kosmos-2251. The two satellites collided at 42,000 km / h and the incident generated some 600 debris which today must be monitored constantly to avoid new incidents.

05:40 - I do not dwell on the subject any further, because I will soon be making a video on Kessler syndrome, a consequence of this kind of incident which can make certain eye sockets unusable. And with Starlink, we are not immune to this kind of scenario. For the Starlink case, we can try to make a very rough estimate of the costs of phase 1. We will start with the satellites SpaceX had announced to be able to produce them for a unit cost of less than $ 550,000 in their factory in Seattle. For the 4408 satellites that will give us something like $ 2.4 Billion.

06:14 - Question launcher, SpaceX is carrying out its launches on its usual Falcon 9 while waiting for the Starship to be operational. Until now, SpaceX has been content to use the first reused stages to launch its satellites, which will keep costs as low as possible. We obviously do not know the cost of these launches internally, SpaceX would have no interest in disclosing the cost of these launches to us, it would be giving arguments to the sales representatives of their future customers to pull the prices down. However, some studies believe that a launch with a reused stage would cost SpaceX between $ 40 million and $ 50 million, so this is the figure we will take while keeping in perspective that this calculation is only for very good reasons. indicative. The Falcon 9 fairing is capable of holding up to 60 satellites, so we will need 74 launches to put the entire phase 1 into orbit. 2.4 billion for the production of satellites and 3.7 billion for launches.

07:04 - There are a lot of elements that are not taken into account in the calculation, but overall it gives us an idea of ​​the extent of the investments necessary before even having a functional product. It is not for nothing that OneWeb has experienced some difficulties recently The financial aspect is not the only barrier to overcome to achieve a functional and efficient constellation. Signal management, for example, is one of the technical challenges to be met, because as we have seen previously, latency and throughput are key elements in this technological revolution From a hardware point of view, to connect to the constellation it will necessarily go through an antenna. Antennas that will be made available for $ 499 in addition to the $ 99 subscription for Americans at least. Terminals such as telephones do not in fact have the capacity to pick up the ku, ka bands which will be used to transmit the signal between the ground and the orbit.

07:52 - When you try to view a page on your phone; The telephone will have to connect to the antenna which will send a request towards the satellite satellite which will bring it down to the ground station which is itself connected to the server. The information will do the reverse and display the page on your terminal. In principle it seems rather simple, in practice you need to have a lot of ground stations to be able to relay information. This is a problem that could arise in the event that information should travel from one side of the ocean to the other. Indeed, if there are no islands on which to set up a station, using the network from ships during crossings could prove to be complicated.

08:27 - SpaceX, aware of the problem, is working on this problem, since they plan to equip all future satellites with lasers, to allow them to communicate with each other and free themselves from the need for a ground station over long distances. And what can we expect in terms of throughput? Well the first tests which have filtered through the beta, show a download rate of between 35 and 65 Mbps and between 5 and 18 Mbps in upload. It roughly corresponds to VDSL. The ping varies between 30 and 100 milliseconds, we are a little limited for gaming, but it’s still more than correct. However, it will be necessary to keep in perspective that these figures will depend a lot on the load of the network, if you are in the middle of the countryside with no one within 10 km , it will go much faster than in a densely populated metropolis. The satellite is indeed not unlimited in terms of capacity.

09:14 - We can clearly see on this representation of phase 2 that it is a problem that is taken into account by SpaceX for the future of the network. The white trails are actually satellites that are placed in the same orbit. Some of these orbits And which pass over the main population foci of the planet Some of these orbits will contain more than 7000 satellites and that could make it possible to reduce the load of the network or to distribute it more efficiently. Its shape is quite atypical since it is flat in the launch position and does not look like anything known. One might have expected a CubeSat format satellite to keep costs down, but SpaceX decided that this shape was more suited to the falcon 9 fairing.

That way the company 09:53 - can maximize the number of satellites per launch using the full capacity of the launcher fairing. SpaceX internally produces its satellites; a rather unusual process in the sector where we usually have a company that manufactures the satellite, one that launches it and one that operates it. This total vertical integration allows - if the process is mastered - sacred savings since there will be no intermediaries to take a margin. According to the latest information, they are able to release up to 6 satellites per day in its factories. In terms of dimensions, we are on a satellite measuring 2m80 by 1m40 and which weighs 260kg.

When the single solar panel is deployed it 10:30 - reaches a wingspan of 10m. The satellite is equipped with 4 antennas which transmit and receive on the Ku, Ka frequencies as well as another intended for the V band. The small peculiarity of this last frequency is that it is very absorbed by the atmosphere. It can be assumed that this band will be used to communicate between the satellites while the KU and KA will be used in uplink and downlink with the ground. At an altitude of 550km, thanks to its antennas, the satellite will be able to cover a circle with a radius of 900km.

11:01 - It will also be equipped with a Hall effect propulsion system using Krypton as a reaction mass. If they do not use Xenon as is the case with the usual Ion thrusters, it is to reduce the cost of operating the satellite. Xenon costs up to 10 times more than Krypton. As the other would say , no small savings! This propulsion will be used by the satellite to ascend its orbit once it is deployed and possibly reposition itself if necessary. Currently the satellites are dropped at an altitude of 400km and must climb to their operational orbit by their own means. The satellite is also equipped with a Star tracker which allows it to position itself precisely in space.

It is also equipped with gyroscopes, which allow it 11:48 - to orient itself precisely. And finally, SpaceX installed an autonomous collision avoidance system supposed to prevent Kessler syndrome which, as I explained a little earlier, would render certain orbits unusable in the event of debris. This system is based on the United States Department of Defense catalog which tracks debris larger than 5cm in low orbit. System which aims to avoid collisions by performing avoidance maneuvers upstream. This mega-constellation promises to be a real technological feat as the technical challenges are numerous.

And SpaceX is on track to realize 12:25 - its project thanks to innovative means and a cost rationalization strategy. But despite its proven potential, Starlink raises several thorny questions such as the increased risk of collisions and light pollution. The satellites are indeed visible in the sky under certain conditions and given the outcry that it is currently causing when there are less than 1000 satellites in orbit, I let you imagine what it will look like when there is. 30,000. And it is in the next episode that we will look at this subject of light pollution. Before I leave you, I want to thank Nico for his invaluable help on the visuals for this episode. With that, I’ll leave you. See you soon on Void .