Jeremy Grantham says investors should wish SpaceX fails because success would supercharge AI robots

Jeremy Grantham has found the one group of people more annoying than SpaceX skeptics: SpaceX optimists. On The Diary of a CEO, the billionaire investor told Steven Bartlett that people should actually hope SpaceX fails, because its success would mean a world stuffed with AI chips, robots, space-based power, and energy demand so large it stops sounding like a business plan and starts sounding like the opening monologue of a disaster movie.

You know, one of the scary things about SpaceX is you should wish that it not work out

This is vintage Jeremy Grantham, which is to say: gloomy, grand, and annoyingly hard to dismiss. Grantham is not some random anti-tech scold yelling at a Falcon 9 from the parking lot. He is the GMO co-founder who has spent decades making a career out of saying, in effect, nice party, shame about the hangover. His specialty is bubbles. His hobbyhorse is climate. His vibe is the man at the wedding quietly calculating divorce probabilities.

Bartlett, to his credit, immediately makes the scene funnier by disclosing that he is an investor in SpaceX. This is the podcast equivalent of telling a cardiologist, mid-rant about bacon, that you own a smokehouse. Grantham does not soften. He says Starlink is a real business. He even says he might have invested if it were just Starlink. But the broader SpaceX valuation, in his telling, is something else entirely: a Musk-sized narrative machine powered by Mars, asteroid mining, and the market’s endless appetite for the next miracle.

I think um it will fail to deliver anything like its promises in the prospectus. Yes, absolutely.

The Tesla miracle is also the warning

The smarter version of Grantham’s argument is not that Elon Musk can’t build astonishing things. Grantham owns that problem right away. He bought a Tesla years ago, says the car still has not been to the garage, and admits the stock went up tenfold while he thought it was overpriced. That is the Musk paradox in one neat little humiliation: the skeptic can be right on valuation and wrong on timing for so long that the scoreboard starts laughing at him.

But Grantham’s read on Tesla is brutal. Musk, he says, did not merely execute. He talked the stock into the sky, sold shares at prices Grantham thought were far above fair value, and used that money to build factories that helped make the dream less ridiculous. Belief became financing. Financing became factories. Factories became more belief. A perpetual motion machine, except with quarterly filings.

He’s so good at BS. I That’s a technical term.

His verdict on SpaceX is that Musk needs the same trick again, but on a larger and more fantastical scale. Grantham calls the pitch around asteroid mining and huge AI-driven demand exactly the kind of story that shows up when markets are peaking. The host counters with the greatest hits: Starship caught by chopsticks, Neuralink demos, Teslas driving themselves for hours. Grantham doesn’t deny the magic. He just refuses to price magic as destiny.

SpaceX is such a fabulous BS story, mining asteroids. Huge, incredible success of AI. It’s the classic description of a market peak.

Mars gets the cold shower

The funniest part of Grantham’s SpaceX skepticism is how quickly Mars loses its romance. Bartlett brings up Musk’s line that if something obeys the laws of physics, it is possible. Grantham basically replies: fine, enjoy your underground cancer bunker with a spinning gravity machine. He says Mars means radiation, damaged hearts, weakened bones, and a sustainability problem humans have not solved in a dome on Earth, never mind on a dead planet that hates you personally.

The fair call is that Grantham overstates when he says going to Mars is “not within the laws of physics really.” Technically, probes and rovers have done the commute. The problem is not physics in the pure sense. It is biology, cost, radiation, closed-loop life support, and the small matter of making a settlement that does not become a very expensive tomb. His phrasing is melodramatic. His skepticism is not.

That is why the SpaceX claim is more interesting than the usual billionaire-doomer routine about artificial intelligence. Grantham is not saying innovation is fake. He is saying the market has bundled real engineering, Musk charisma, AI mania, and planetary escapism into one valuation story. He may be early. Bubble callers usually are. But when a guest tells a SpaceX investor to his face that the company should fail for the good of humanity, that is not portfolio advice. That is a flare.