CAPE CANAVERAL, Fla. (Reuters) – Elon Musk’s SpaceX was due to launch 60 small satellites into low-Earth orbit on Wednesday, part of his rocket company’s plan to sell Internet service beamed from space to fund his grander interplanetary ambitions.

In a call with reporters ahead of the evening launch, the billionaire entrepreneur praised the “fundamental goodness” of his mission to expand internet connectivity globally but cautioned that success was far from guaranteed.

Musk said he expects launch services revenue to top out around $3 billion per year, making Starlink key to generating the cash that privately held SpaceX needs to fund Musk’s larger dream of developing a new craft capable of flying paying customers to the moon and eventually trying to colonize Mars.

“We think this is a key stepping stone on the way towards establishing a self-sustaining city on Mars and a base on the moon,” said Musk, who is also the chief executive officer of automaker Tesla Inc.

A rocket with the first 60 Starlink satellites was due to blast off from the Cape Canaveral Air Force Station in Florida at 10:30 p.m. Each satellite weighs 500 pounds (227 kg), making this the heaviest payload for any SpaceX rocket to date.

At least 12 launches carrying similar payloads are needed to achieve constant internet coverage of most of the world, Musk said. Starlink is only currently authorized for operations in the United States.

Musk faces stiff competition. In February, Airbus SE-backed OneWeb launched its own clutch of satellites, while LeoSat Enterprises and Canada’s Telesat are also working to build data networks.

In each plan, the tiny satellites orbit closer to Earth than traditional communications satellites, a radical shift made possible by leaps in laser technology and computer chips.

Musk has faced other challenges. In November, the entrepreneur, frustrated with the pace at which Starlink satellites were being developed, fired at least seven people on the program’s senior management team at a campus in Redmond, Washington, outside of Seattle, Reuters reported.

Musk said SpaceX has “sufficient capital” to make Starlink operational but would potentially need to raise money if things go wrong with the multibillion-dollar endeavour, which he called “one of the hardest engineering projects I’ve ever seen done.”

Musk said SpaceX would begin approaching customers later this year or next year. As many as 2,000 satellites will be launched per year, he said. But he wavered on the timeline for placing as many as 12,000 satellites into orbit as the company had previously described.