Why SpaceX is Making Starlink

This episode of Real Engineering is brought to you by Brilliant, a problem-solving website that teaches you how to think like an engineer. On May 24, SpaceX launched a Falcon 9 rocket packed with 60 satellites into space. This marked the beginning of their ambitious new project called “Starlink”, which aims to provide high-quality broadband Internet to the most isolated parts of the planet, while also providing low-latency connectivity to already well-connected cities. SpaceX aims to make its broadband as accessible as possible, saying anyone will be able to connect to its network if they buy the pizza-box-sized antenna SpaceX is developing. This launch of 60 satellites was just the first of many.

Spacex plans to launch 12,000 satellites over the next decade, dramatically increasing the total number of spacecraft around Earth's orbit. This will cost SpaceX billions of dollars, so they must have a good reason for doing it. Let's see how this network will work and how it will compete with existing Internet providers. In 2015, Elon announced that SpaceX had begun work on a satellite communications network and stated that there is significant unmet demand for low-cost global broadband capabilities. Around that time, SpaceX opened a new facility in Redmond, Washington, to develop and manufacture these new communications satellites. The initial plan was to put two prototype satellites into orbit by 2016 and have the initial set of satellites operational by 2020.

But the company had difficulty developing a receiver that could be easily installed by the user at low cost, which delayed the program. and initial satellite prototypes were not launched until 2018. After a successful launch of the two prototypes, Tintin-A and B, which allowed SpaceX to test and refine its satellite design, SpaceX was largely silent about what was next for the Starlink project. , until November 2018, when SpaceX received FCC approval to launch 7,500 satellites into orbit, in addition to the 4,400 that were already approved. On May 24, the first batch of production satellites were launched into orbit, and people around the world quickly began to spot the train of satellites moving across the night sky.

This launch is a sign of things to come, while this initial group of satellites is not fully functional, they will be used to test things like ground communications systems and krypton thrusters that will be used to autonomously avoid debris and remove from orbit the planet. spacecraft once it has reached the end of its life cycle. Let's look at these features first. We've explored how ion thrusters work in the past, which you can look at for more details, but they essentially use electrical potential to shoot ions out of the spacecraft to provide propulsion. Xenon is ideally used because it has a high atomic mass that allows it to provide more thrust per atom, while being inert and has a high storage density that lends itself to long-term storage on a spacecraft.

However, SpaceX opted for krypton, as xenon's rarity makes it a much more expensive propellant. This ion thruster will initially be used to lift the Starlink satellites from their 440 km launch orbits to their final orbital height of 550 km. They will also be used in conjunction with the onboard control boost gyroscopes located here and the US government's Space Debris Collision Prediction System to allow satellites to adjust their orbits to avoid collisions, which we've also talked about in more detail in a previous article. video. When the satellites have reached the end of their useful life, they will be able to use the same attitude controls and thrusters to deorbit.

Space X has included all the necessary hardware to minimize the risk of space debris. In their request for approval from the Federal Communications Commission, they claim that 95% of the satellite will burn up upon re-entry. With just the internal structure of the ion thruster and silicon carbide components, there is a chance of survival. These silicon carbide components are likely to survive as they are essential materials for laser operation and therefore have an extremely high melting point of 2,750°C. Which brings us to our communication capabilities, the primary function of the satellite. Spacex has been silent on many of the details of the satellite, but thanks to that FCC filing we know that the satellites will contain 5 1.5 kilogram silicon carbide components, indicating that each satellite will contain 5 individual lasers.

These lasers, like our fiber optic cables here on Earth, will use pulses of light to transmit information between satellites. However, transmitting with light in space offers a huge advantage over transmitting with light here on Earth. The speed of light is not constant in all materials; in fact, light travels 47% slower in glass than in a vacuum. This gives Starlink a huge advantage that will likely be its main source of income. Provides the potential for lower latency information over long distances; In simpler terms, let's imagine this as a race between data packets. A user from London wants to know the new adjusted price of a share on the NASDAQ of the New York Stock Exchange.

If this information were to be used a typical route, say through the AC-2 cable, which has a round trip of about 12,800 kilometers to be made through our glass fiber optic cable. In a vacuum, light travels at a speed of 299,792,458 meters per second. The speed of travel in glass depends on the refractive index and the refractive index depends on the wavelength, but we will take the reduction to be 1.47 times slower than the speed of light in a vacuum. This means that the data packet will take approximately 0.063 seconds to make the round trip and therefore has a latency of 0.063 seconds, or 62.7 milliseconds.

With additional steps adding to this latency, such as converting light signals to electrical signals at each end of the optical cable, traffic queues, and transfer to our final computing terminal, this total time amounts to about 76 milliseconds. Calculating Starlink latency is much more difficult since we don't have real-world measurements to base it on, but we can make some educated guesses with the help of Mark Handley, professor of communications at University College London. The first source of latency for Starlink will be during the uplink and downlink process, where we need to transfer our information to and from Earth.

We know that this will be done with phased array antennas, which are radio antennas that can control the direction of their transmission without moving parts; instead, they use destructive and constructive interference to control the direction of the radio wave. Each satellite has a cone beam with a viewing range of 81 degrees. With an orbit of 550 kilometers, each satellite can cover a circular area with a radius of 500 kilometers. In the orbit originally planned by SpaceX, this coverage had a radius of 1,060 kilometers. Lowering a satellite's altitude decreases the area it can cover, but it also decreases latency. This is particularly notable in the case of typical communications satellites operating in geostationary orbit at an altitude of about 36,000 kilometers.

The time it takes for data to travel to the satellite and return at the speed of light is around 240 milliseconds, 369% slower than our undersea cable. However, since Starlink intends to operate at a much lower altitude, the theoretical uplink and downlink latency could be as low as 3.6 ms. That's why SpaceX needs so many satellites in its constellation to provide global coverage. Each individual Starlink satellite has a four-phase antenna located here, here, here and here. This directional beam was an essential part of SpaceX's FCC approval application, as thousands of satellites transmitting undirected radio waves would cause significant amounts of interference with other communication methods.

Once a Starlink satellite receives that data, it can begin transmitting that information between satellites using lasers. Every time we jump off the satellites there will be a small delay as the laser light is converted to an electrical signal and vice versa, but it's too minuscule to consider. Things get complicated here with the use of lasers, as we need to precisely point the receiver of neighboring satellites to transmit that data. Let's take a look at SpaceX's proposed constellation to see how it will work. Space This will look like this. Communication between neighboring satellites in the same orbital plane is relatively simple, since these satellites will remain in relatively stable positions relative to each other.

This gives us a strong line of communication across a single orbital plane, but in many cases a single orbital plane will not connect two locations, so we must also be able to transfer information between these planes. This requires precise tracking, as satellites traveling in neighboring orbital planes travel incredibly fast and appear and disappear from view. This means that the Starlink satellite will need to switch to a new satellite in the network. This can take time, the best figure I could find is about a minute for the European Space Agency's Satellite Data Relay System, which is a geostationary Internet constellation currently in operation designed to serve European imaging and satellite satellites. other applications where time is critical.

How to serve emergency forces in remote areas, such as those fighting forest fires. Starlink may be faster, but it will not be instantaneous and therefore has 5 optical communication systems on board to maintain a stable connection with 4 satellites at all times. If we now use this system, transmitting from New York to London and vice versa, with the shortest possible path, using the speed of light in a vacuum as the transfer speed, we can achieve a latency as low as 43 milliseconds. Even if we took the shortest possible path with fiber optics, which does not exist, it would take about 55 milliseconds, a 28% decrease in speed.

The current actual return travel time for an average citizen is about 76 milliseconds, as we saw above. A 77% decrease in speed. This is big business for the two financial markets that operate in these cities, since millions of dollars move in fractions of a second; Having lower latency would provide a huge advantage in capitalizing on price swings. In fact, it would not be the first time that a communications company has made a massive investment to specifically serve these groups. The Hibernian Express cable is a privately owned optical cable that is currently the lowest latency connection between the NY4 data center in Secaucus, New Jersey and the LD4 data center in Slough, England, at just 59.95 milliseconds, a 39.4% slower than our best time with Starlink. .

The previous best time was for the AC-1 cable with 65 milliseconds. At a cost of $300 million, this 5 millisecond speed increase was justified only to connect to the other side of the Atlantic. Imagine how much these time-sensitive industries will be willing to pay for a 17 millisecond speed increase. It becomes even more valuable when you realize that this time differential increases as the transmission distance increases. New York to London is a relatively short distance. The improvements would be even more pronounced for a London to Singapore transmission, as for every additional kilometer we travel, the potential gains in speed increase rapidly.

But SpaceX not only plans to offer this super-fast Internet to some customers, it mainly advertises this system as a way to connect every human being on this planet to the Internet, and they should have enough bandwidth to serve these people. Although the Internet has been one of the fastest growing technologies in human history, at the end of 2019 more than half of the world's population will remain offline (4 billion). Users will connect to the internet using a Starlink terminal which will cost around $200 each, this will still be well outside the purchasing power of many third world citizens but it is a start and much cheaper than similar receivers currently available like the Kymeta version at a price of $30,000.

Elon Musk says they will be flat enough to fit on the roof of a car and other vehicles like boats and planes. This will allow Starlink to compete with traditional Internet providers. Moving the US from 4G wireless to 5G wireless is estimated to cost around $150 billion in fiber optic cabling alonefor the next 7 years; SpaceX plans to complete its entire Stralink project for just $10 billion. Each Starlink satellite costs around $300,000, which is already a huge cut in the cost of communications satellites. SpaceX is also saving launch costs by launching its own Falcon 9 rocket, something no other satellite manufacturer has.

If all goes as planned, Starlink is estimated to generate between $30 billion and $50 billion in revenue each year from premium memberships on the stock exchange, demolishing its current annual revenue of around $3 billion. . And this is a vital part of Elon Musk's long-term goals. The money generated by Starlink will mean that SpaceX will have much more funding than NASA. Which could finance the research and development of new rockets and the technology necessary to monetize lunar and Martian colonies. For now, the project simply connects the world further and potentially opens up pathways. Widely available internet will help solve this problem, and platforms like Brilliant have taken great steps to remedy this through their high-quality interactive math and science learning.

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