Space Stocks Got Crushed on SpaceX's Big Day. Is the Sell-Off a Warning or a Buying Opportunity?

Several publicly traded space stocks fell sharply on the same day SpaceX surged in its market debut.

One theory is that investors sold existing space names to free up cash for SpaceX shares.

The strongest businesses in the group look very different from the most speculative ones.

It was a strange day to own a space stock. While SpaceX jumped about 19% in its first session as a public company, several of the smaller, already-public names in the sector went sharply in the other direction. As of this writing, shares of Rocket Lab (NASDAQ: RKLB) , AST SpaceMobile (NASDAQ: ASTS) , and Intuitive Machines (NASDAQ: LUNR) were all down meaningfully, even as the company they're so often compared to was being celebrated.

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One widely floated explanation is rotation. With retail demand for SpaceX shares running hot, the theory goes that some investors sold their existing space holdings to free up cash for an allocation in the debut. If that's the main driver, the drop says little about these businesses and a lot about a one-day scramble for shares.

But the move may also reflect something more durable: investors taking a harder look at how these companies stack up against a far larger, better-funded rival. Here's a closer look at the three names and whether the drop changes anything.

Rocket Lab fell more than 10% on Friday -- a notable drop but the mildest of the three -- and one that came on a day the company actually had good news. Rocket Lab said it will join the Nasdaq-100 index later this month -- a milestone that typically brings fresh demand from index funds.