PARIS — Fleet operator SES placed a seven-satellite order with Boeing Satellite Systems International to build a second generation of O3b satellites that will have more than triple the capacity of ViaSat’s future ViaSat-3 constellation.

The new constellation, called O3b mPower, consists of an initial seven high-throughput satellites in medium-Earth orbit, delivering capacity through 30,000 spot beams for broadband internet services.

O3b mPower is expected to launch in 2021, building substantially on top of the 20 Thales-built first-generation O3b satellites for which the remaining eight are scheduled to launch four at a time in 2018 and 2019 on Arianespace Soyuz rockets.

Signaling intent to have at least some of the O3b mPower satellites launched before ViaSat-3, Steve Collar, CEO of SES Networks, said the new constellation “will be the first multi-terabit system” in orbit.

“We’ll be able to deliver anywhere from hundreds of megabits to 10 gigabits to any ship at sea, which sounds like a tremendous amount, but as we develop over the course of the next five to 10 years, that is the need that is going to be there,” he said at a press conference here on the sidelines of Euroconsult’s World Satellite Business Week conference here.

O3b mPower will have the ability to aim capacity at customers specifically, and avoid putting beams down in areas where none are present, he said. Software-defined routing will direct traffic between SES Network’s geostationary and medium-Earth orbit fleets, he said.

SES Networks’ investment in O3b mPower further showcases the confidence of SES overall in nongeostationary satellites. Karim Michael Sabbagh, SES’s president and chief executive, said the seven satellite system will, in addition to bringing substantial new capacity, eliminate the need for replacements of two legacy geostationary satellites.

“This is only the start of the journey,” he added. “There will be further optimization of our geostationary fleet going further as we grow that particular system for data centric applications.”

SES expects the constellation will allow the company to reach a larger customer base using a new terminal. Executives declined to say which industry partners are designing such terminals, however.

The seven mPower satellites will cover 400 million kilometers. Collar said the goal will be for the system to eventually reach any point on Earth.

“We designed O3b mPower as a system, not as a bunch of satellites, and not as limited to the first seven satellites that we launch,” he said. “So O3b mPower will be and is conceived as being a fully global system.”

Collar reiterated the claim O3b Networks was making even before becoming the central force behind SES Networks — that its medium-Earth-orbit constellation is readily scalable and can increase in size with little difficulty when justified. The O3b mPower system took about two years to design, he said, and culminated in a Boeing contract because of Boeing’s willingness to cooperatively design the constellation. Collar said Boeing gave what he would consider “unique access” visibility into their capabilities, which persuaded SES Networks to place the contract.

Paul Rusnock, Boeing Satellite Systems International’s chairman and CEO, said the O3b mPower constellation will use a new satellite platform based on Boeing’s 702 line of scalable buses. A bigger change than that, he said, is the implementation of a new “highly integrated electronics phased-array payload system.”

“It’s quite a departure from our standard product,” he said. “It’s very light, it’s very powerful in how it can produce capability and get the resources where they need to go … When you open up the spacecraft, you are seeing bus components in there but very little payload. It’s all in this one piece.”

Boeing and SES executives declined to say the mass of an individual O3b mPower satellite. The first generation from Thales Alenia Space had a mass of 700 kilograms each.

Executives also declined to say which rockets would launch the satellites. Like the first generation, they are designed to launch up to four at a time, though Collar said SES Networks could use a rocket other than Soyuz to accomplish that goal.

Rusnock said Boeing is not expecting any dispute with ViaSat over the phased-array antenna technology being used for SES because the phased array is entirely new.

ViaSat sued manufacturer Space Systems Loral in 2012 over ViaSat-1 technology it said was later used in competitor Hughes Network Systems’ Jupiter-1 spacecraft. ViaSat has since guarded its technology more carefully from all manufacturers it works with. For ViaSat-3, Boeing is mainly tasked with providing the satellite bus while ViaSat creates the payloads independently.

“This is not patented from ViaSat,” Rusnock said of the phased-array system. “This is something we did on our own, building independent from ViaSat. We respect their need to maintain their intellectual property.”

ViaSat has ordered two out of three ViaSat-3 satellites, each of which advertise a terabit of capacity. The company has yet to order the third ViaSat-3 for the Asia-Pacific. The first two are expected to launch in 2020 to 2021.