The hitchhiker's guide to Musk's SpaceX memo

• Elon Musk's merger memo is filled with high-level space and science jargon — and a Musk-favorite phrase.
• "Sentient sun," "Kardashev II-level," and "electromagnetic mass driver." What do they even mean?
• Here's your cheat sheet for Musk's space-age lingo.

Elon Musk has never been shy about his inner nerd — just look at his SpaceX merger memo.

Over the years, the billionaire has peppered his company communications with sci-fi culture Easter eggs, physics nerd jargon, and enough dad-joke flair to make comedian Nate Bargatze blush.

So it was no surprise that Musk's latest internal memo — announcing that SpaceX would merge with xAI — leaned into the kind of words and phrases that might cause you to scratch your head.

It reads less like a conventional corporate M&A announcement and more like a sci-fi manifesto, invoking "sentient suns," orbital data centers, and humanity's destiny among the stars.

Forget "The Hitchhiker's Guide to the Galaxy," here is your hitchhiker's guide to Musk's memo.

'Sentient sun'

The memo opens with a sci-fi banger, the kind of premise you'd find in a Hollywood script: Musk says his new vision for the combined company is to build a "sentient sun."

The phrase is meant to convey scale. Musk is imagining an AI system so large, energy-hungry, and centralized that it metaphorically resembles a star. Except instead of radiating light and heat, this "sun" would beam computer-generated intelligence back to Earth.

It's a piece of sci-fi shorthand for extremely powerful, solar-fed AI.

'Kardashev II-level civilization'

This is where the memo goes full-on science nerd: "Launching a constellation of a million satellites that operate as orbital data centers is a first step towards becoming a Kardashev II-level civilization," Musk wrote.

Musk is referencing the Kardashev scale, a '60s framework created by Soviet astronomer Nikolai Kardashev that ranks civilizations by the amount of energy they can harness. A Type I civilization can use all the energy available on its home planet. A Type II civilization can capture the full power output of its star.

Humanity today is generally thought to sit somewhere below Type I.

'Orbital data centers'

Here, Musk is proposing to move massive computing infrastructure — the power-hungry data centers popping up in rural America to fuel modern AI — off Earth and into orbit. In other words, data centers in space.

In space, he argues, those systems could rely on near-constant solar energy. As Musk put it elsewhere in the memo: "It's always sunny in space."

'In-space propellant transfer'

SpaceX essentially wants to build a floating gas station. Here, Musk describes a dedicated tanker-to-ship bot expected to roll out in 2026, per SpaceNews.

Right now, rockets carry all of their fuel right from takeoff. This system would allow the company's spacecraft to optimize for other storage cabins.

'Electromagnetic mass driver'

Musk is essentially a giant railgun designed to launch cargo into space using electricity instead of rocket fuel. It's reminiscent of an instrument in the 1937 science fiction novel "Zero to Eighty."

SpaceX is imagining building one on Earth's Moon, where lower gravity and the lack of an atmosphere would make it easier to fling materials into space.

'Ad Astra!'

Musk ends the memo with a linguistic flourish.

By signing the letter with "Ad Astra" — Latin for "to the stars" — Musk is referencing his service of expansion beyond Earth.

It isn't the first time Musk has used the phrase. In 2014, he launched a Montessori-style school for children from 3 to 9 with the same name. The school's curriculum focused on STEM learning and problem-solving, according to its mission statement.