One of SpaceX’s most ambitious projects remains on the ground, for now


A stack of 60 SpaceX Starlink satellites floats in orbit above the Earth.Source: SpaceX

To finance its Martian ambitions, SpaceX intends to transform the Earth by covering the planet with ubiquitous Internet coverage broadcast from a tight mesh of thousands of satellites. CEO Elon Musk expects this “Starlink” service to ultimately generate $ 30 billion a year.In space, construction is progressing smoothly. SpaceX has already become the world’s largest satellite operator, managing more than 500 satellites and having cash. It is a fraction of the thousands he intends to launch, but enough for the system to reach the Air Force cockpits and connect Musk to Twitter. The company intends to begin beta testing in North America this summer.

In the field, however, SpaceX still has some work to do. He has yet to disclose equipment to connect a customer’s home to the satellites flying overhead. The company will also need a network of ground stations connecting its satellites to the physical backbone of the Internet. The construction of these nodes is hardly rocket science: indeed, 26 are already planned for the United States. But without a crucial satellite upgrade, these stations will keep the coverage of the network stuck largely on the ground.

“It’s not really a global service at the outset,” said Tim Farrar, president of TMF Associates, a satellite and telecoms research company, “even though satellites are flying everywhere.”

Return global broadband

Efforts to transmit data from the sky are generally classified into two categories: the very close and the very distant. Alphabet, Google’s parent company, deploys Internet balloons about 12 miles above the ground in Kenya, for example, and Facebook has its eye on solar-powered drones. These near-surface approaches are rapid, but each floating antenna has a limited geographic footprint.

In contrast, companies like the Canadian communications firm Telesat have long operated a handful of satellites in high orbit more than 20,000 miles above the surface of the Earth, where each machine can reach a large band of the planet. These systems provide global coverage, but snail-like connections, with round-trip signals taking more than half a second. “It doesn’t seem like a big deal, but a typical web page can have 100 round trips,” said Erwin Hudson, vice president of Telesat. “It adds up. ”

With Starlink, SpaceX joins a mix of companies, including Telesat, all in the running to offer the best of both worlds: “constellations” of satellites close enough to communicate with the ground in a few tens of milliseconds, but far enough to cover the planet in a reasonable number of satellites. However, to complete the service, SpaceX needs two other terrestrial infrastructures.

Starlink’s biggest terrestrial obstacle

Starlink’s main ground obstacle, Musk recognizes, is the antenna that will bring users online – the Internet analog of the TV dish. Starlink’s low-level satellites fly over the sky in about five minutes, and the antennas will have to follow. SpaceX’s design must balance technological sophistication with the affordability of the mass market.

The company plans to use “phased array antennas,” which can direct the machine’s focus electronically rather than spinning it physically. The technique mechanically simplifies the device, but at a high price. Farrar estimates that the gadget could cost more than $ 1,000, although Musk is targeting a price of less than $ 300. In March, the FCC authorized SpaceX to distribute a million antennas, and SpaceX board members recently tested the devices (which would look like “UFOs on a stick”), but the company has failed not yet announced the commercial version.

Any satellite service also needs a network of ground stations to operate the existing fiber optic infrastructure. These are the points where the space network merges with the World Wide Web. “What goes up must go down,” said Hudson.

SpaceX is also preparing these “gateway” stations. The company has registered 26 locations with the FCC, each of which can accommodate eight antennas. Some are owned by SpaceX while others are owned by telecommunications companies, such as Level Three Communications, which are likely to provide high-speed connections. Handles of mushroom-shaped domes – radar-protected weather protection for antennas – have recently appeared on some of the lots.

Why “cross-linking” is the key concept

These gateways are just the beginning. For maximum performance, Starlink will eventually need thousands of gateway antennas (about one per satellite) spread over hundreds of sites around the world, according to Íñigo del Portillo Barrios, a recent MIT graduate who analyzed the structure of the Starlink constellations. and Telesat.

He says Starlink relies heavily on these stations because the current batch of satellites does not have a function originally intended for the machines to communicate with their neighbors via lasers. This “cross-linking” capability would allow Starlink to transmit a signal to any user on any satellite – even those in the air, on remote islands or in conflict zones. But without it, a satellite must be able to directly link a user to a gateway antenna, thereby limiting coverage to around 500 miles from each ground station, Farrar said.

“They’ll have big holes in the middle of the oceans and some deserts,” said Farrar. “They should go to a country’s regulator and say,” Please let us in, let us build the gateways in your country. “”

This is hardly an obstacle to reaching most rural areas (the stations currently planned will cover most of the United States and Mexico). But traditional satellite Internet customers such as the military, who may wish to access central Iraq for example, or airlines and shipping companies looking for connectivity in the Atlantic and Pacific, may prefer to wait for a truly global service.

SpaceX did not respond to a request for comment on its gateway or crosslinking plans, but Hudson said that although Telesat has 50 years of satellite experience and plans to start launching crosslinked satellites by 2022, the choreography of ground operations will always represent one of their major challenges.

“We are building earth stations on all continents, except perhaps in Antarctica,” he said. “You have to send stuff everywhere. You have to build, maintain and improve them. ”

The addition of crosslinking will eventually help SpaceX reduce the influence of geography on Starlink coverage, and the company plans to start experimenting with interconnected satellites this year, said President Gwynne Shotwell.

But the upgrade will not be easy and the second generation network will not be operational in the immediate future. First, SpaceX needs to revise its satellite design to incorporate a more robust power supply, finely tuned lasers and other hardware. Then he will also have to rebuild and revive the entire swarm.

The company may eventually withdraw it, said Farrar, but Starlink will first have to prove its worth with the satellites it has in the sky and the bridge stations it can build on the ground.


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