Another day, another ambitious goal for one of Elon Musk's companies.

SpaceX has for years teased the idea of creating an internet network using a constellation of satellites. That project has mostly existed in secret, though, with details generally being pieced together through company job listings and FCC filings.

Now SpaceX is offering some details about its plans. During a hearing Wednesday before the Senate's Committee on Commerce, Science, and Transportation, a company exec laid out a projected timeline for getting things off the ground and into orbit.

Patricia Cooper, SpaceX's vice president of satellite government affairs, said the company wants to launch its first prototype later this year, according to CNBC. It would then send up a second prototype in early 2018, and begin its launch campaign in earnest in 2019. By 2024, it wants to have the full constellation of satellites--a whopping 4,425 of them--in orbit.

By comparison, there are approximately 1,419 functioning satellites in total currently circling the earth.

Musk has said that he envisions the internet network serving businesses and everyday consumers, with the majority of the world's long-distance traffic using the network. He estimated that about 10 percent of local internet traffic would use its services as well.

More than four billion people--over half the world's population--lack internet access. Laying ethernet cables in sparsely populated areas is generally not a lucrative venture, so some companies are trying different ways to bring people online.

In February, Google said that it had a breakthrough in Project Loon, its venture to beam internet via hot air balloons. The company said that the development, which entails using artificial intelligence to keep the balloons stationary, will speed up the timeline with which it can turn the project into a profitable business--though when that might happen is still unclear.

Last summer, Google purchased Webpass, a wireless internet company, to help its Google Fiber project deliver internet with far fewer cables needed. But in October, the project's chief stepped aside, and Google halted its expansion indefinitely.

Facebook has engaged in its own plans to beam the internet to rural areas. It has conducted several test runs with Aquila, its massive internet-beaming drone that has a wingspan wider than that of a 737. In December, though, the drone suffered damage when it crash landed in the Arizona desert.

Google and Facebook both have incentives to get more people online, even if it's for free, since that will allow more people to use their platforms. SpaceX seems more focused on paying customers, whether they're businesses or everyday consumers.

A January Wall Street Journal report examining leaked SpaceX documents revealed that the company expects its internet business to earn more than its rocket launches by 2020. It projects that the business will have 40 million subscribers and earn $30 billion in revenue by 2025. In total, SpaceX pulled in $945 million in revenue in 2015.

SpaceX's reusable rockets have significantly decreased the cost of flights to space. In March, it became the first company to launch a previously used rocket into space, sending up a communications satellite aboard its Falcon 9. On Wednesday, Cooper, the SpaceX exec, said the company plans to launch its internet satellites those reusable rockets, which will save on costs for the company.