WASHINGTON — SpaceX shared details about its largely secretive Starlink constellation program March 15, providing updated targets for commercial service, details about satellite design and the thought process behind why the company’s upper target is 12,000 satellites — about six times the number functioning in orbit for the rest of the world combined.

SpaceX’s first launch with a large number of Starlink satellites was pushed back 24 hours, with a new launch window opening at 10:30 p.m. Eastern May 16. The Falcon 9 mission will carry 60 Starlink satellites.

Though the spacecraft lack intersatellite links and other features expected in later iterations, SpaceX CEO Elon Musk said the satellites mark the start of deployment for a constellation designed to deliver internet access to unreached and underserved parts of the world.

Musk, in a call with reporters, said SpaceX views 1,000 satellites as the point when Starlink becomes economically solid.

“For the system to be economically viable, it’s really on the order of 1,000 satellites,” he said. “If we are putting a lot more satellites than that in orbit, that’s a very good thing — it means there is a lot of demand for the system.”

SpaceX asked for and received U.S. market access for a constellation numbering almost 12,000 satellites. Until recently, regulatory filings with the U.S. Federal Communications Commission have been the main way information about SpaceX’s constellation was made publicly available.

Musk said reaching 12,000 satellites would indicate a “very successful outcome” for Starlink.

SpaceX President and COO Gwynne Shotwell said May 7 that the company plans three to seven Starlink launches this year.

Musk said subsequent Starlink launches would each carry roughly 60 satellites. Going forward, Musk said SpaceX could launch 1,000 to 2,000 satellites a year using its Falcon family of rockets.

“It’s a heck of a lot of launches. We will hopefully have Starship active by the time we are anywhere near 12,000 satellites,” he said, referring to the next-generation fully reusable launch system SpaceX is developing.

There are roughly 2,100 operational satellites in orbit today from all the world’s satellite operators, according to a report from Bryce Space and Technology issued May 8.

Musk said Starlink will have continual coverage of limited geographies at around 400 satellites, or seven launches including tomorrow’s mission. Mark Juncosa, SpaceX’s vice president of vehicle engineering, said 12 Starlink launches would ensure coverage of the United States. After 24 launches, Starlink would cover most of the world’s population, and 30 launches would be sufficient to cover the planet, Juncosa said.

With every launch, SpaceX will add about a terabit of “useful connectivity,” Musk said, and two-and-a-half to three terabits overall.

Satellite operators sometimes draw a distinction between usable capacity and aggregate capacity when discussing low-Earth-orbit constellations, since the constellations are generally designed for global coverage, but are unlikely to have customers in every location where beams are active.

SpaceX’s projection for Starlink puts its usable capacity higher than any single geostationary communications satellite in orbit today, and would significantly outpace any other publicly known low-Earth-orbit constellation under development. Telesat, which is planning a constellation of 300 satellites, estimates it will provide 8 terabits of “useful capacity.” The satellites in OneWeb’s first-generation constellation of 600 operational satellites and 50 spares are designed to carry 10 gigabits per second each, meaning the system should presumably offer 6 terabits per second of aggregate capacity (OneWeb did not respond to a May 14 request to confirm that number).

Updated Starlink designs

SpaceX launched two prototype Starlink satellites in February 2018. These new satellites will be significantly different, Musk said.

Musk said Starlink’s newest 60 satellites carry phased array antennas and ion propulsion units that run on krypton instead of the typical xenon gas. SpaceX chose krypton because it is less expensive than xenon, Musk said.

SpaceX’s first-generation satellites won’t have intersatellite links, but will be able to use ground stations as relays to “ground bounce” signals around the world, he said. Later generations would include intersatellite links and other upgrades, he said, though he didn’t give a timeframe for when those would be introduced.

Musk said SpaceX would like to keep Starlink satellites in orbit for four to five years before deorbiting and replacing them with newer, more capable models.

Antennas and customers

Musk said Starlink user terminals will also use phased array, electronically steered antennas — a technology widely considered essential for the success of low-Earth-orbit broadband constellations.

In contrast to traditional dish antennas, electronically steered systems can track two or more satellites simultaneously, meaning no loss in connection when satellites rise and set over the horizon.

Musk said Starlink terminals, leveraging work by SpaceX’s “chip team,” can switch between satellites in under a thousandth of a second, and will support a system where the overall latency is under 20 milliseconds.

Musk described the terminals as similar in size to a small or medium pizza. While Musk mainly talked about Starlink as a system to bridge the digital divide by connecting unreached peoples, Musk said the antennas could also serve the more lucrative markets of aviation and maritime that most satellite operators are pursuing. The antennas could also be used to connect cars, he said.

Musk didn’t say how much the antennas would cost, however, or when they would be available. Most electronically steered antennas are too expensive for consumers and businesses to utilize.

Musk said SpaceX has not tried to win customers for Starlink yet, believing it would be better to have a firm grasp on its constellation deployment schedule first. SpaceX will likely start selling connectivity later this year or early next year if all goes well, he said.

Musk said SpaceX is interested in signing telcos as customers, as well as governments that want to connect hard to reach parts of their countries.

SpaceX plans to use Starlink to generate more funding in support of its goal of establishing a colony on Mars, Musk said. Starlink revenue would also help fund a base on the moon, he said.