Elon Musk, the electric car pioneer and space tycoon, makes some optimistic predictions about his plans for the future that don't always pan out, but when they do come to fruition, they really can astound. Take Starlink, for example.

Eight years ago, Starlink -- SpaceX's globe-spanning satellite broadband internet project -- was just a gleam in Musk's eye. It was bright enough to attract a $1 billion investment from Alphabet and Fidelity, but no one knew at the time if providing affordable, high-speed internet access from space was even technologically feasible.

Two years ago, SpaceX proved the concept could work, and attracted its first 10,000 customers to try out a beta version of Starlink. And by May 2023, Starlink had already grown 150 times in size, reaching 1.5 million subscribers.

Impressive, but Starlink was working off an admittedly small user base at the time. The bigger question this year was whether Starlink could continue to grow quickly as the law of large numbers started kicking in. Turns out, it can.

Time lapse photo shows the famous SpaceX rocket launch and landing "X."

Image source: SpaceX.

10,000, 1.5 million, 2 million

As SpaceX confirmed in a message via X (formerly Twitter) last weekend, Starlink has just hit a new milestone on its growth path, surpassing 2 million active customers for its internet service.

With users on all seven continents today, the service is gaining quite a following. One fan, for example, recently posted the following graphic showing the approximate locations of Starlink's nearly 4,800 internet satellites in orbit currently, and it's simply mesmerizing to watch.

If you can tear yourself away from that video, I want to draw your attention to some facts and figures of more immediate import to investors wondering when SpaceX will fulfill Musk's promise for an initial public offering (IPO) for Starlink once its revenue has become "smooth and predictable."

SpaceX by the numbers

Let's start with some math. At last report, SpaceX was charging $110 per month for most Starlink users. Multiply that yearly amount by 2 million subscribers, and it implies that SpaceX is probably raking in something on the order of $2.6 billion annually.

Granted, businesses, the government, the military, and certain kinds of consumers pay more (while certain users in foreign countries and low-demand locations pay less), but ordinary consumers vastly outnumber those exceptions. Still, to account for the exceptions, let's round up and say Starlink might be generating $3 billion annually at present.

On the one hand, that sounds like a lot. On the other hand, it's a lot less money than SpaceX had hoped Starlink would be bringing in by this time, back when it was first penciling in estimates for the service in 2015.

Here's the thing, though: Starlink might be a bit behind schedule at present, but it's growing quickly. And it might be growing sufficiently quickly, smoothly, and predictably at this point that SpaceX would consider an IPO for it.

Growth times three

How fast is Starlink growing? It hit 1.5 million users in May, and four months later, it just hit 2 million. That means Starlink added 500,000 users in four months. And if you calculate that run-rate over a 12-month span, this implies the service might be growing at the rate of 1.5 million users per year.

And if Starlink does that -- adding 1.5 million customers in a year to the 1.5 million customers it had in May -- that would imply an annual growth rate of 100%. Which is really impressive, especially if this growth continues "smoothly and predictably," as Musk wishes.

Consider: If 1.5 million customers become 3 million customers in one year, then they might become 6 million customers in two years, 12 million in three years, and 24 million by the year 2027.

I won't extrapolate beyond that, but I will point out that if Starlink can bring in $3 billion in revenue with 2 million customers, then with 24 million customers, it should easily be able to manage $36 billion in 2027 revenue -- which just happens to be SpaceX's original projection for its revenue in 2025.

So it might take SpaceX a couple of years longer to reach this goal than Musk originally expected. But the way things are going, he does appear to be on a "smooth and predictable" path to hit that target eventually.

And if I'm right about that, then we're getting really close to the time we might see SpaceX announce the Starlink IPO.