What happened

After less than a month on the public markets, the Israeli start-up X-ray machine maker Nano-X Imaging (NNOX -1.18%) has more than doubled off its $18 offer price. Shares shot up more than 15% in early trading Tuesday and were still up about 7.7% at 1:50 p.m. EDT.

So what

Nano-X was rising in a market where the rest of the Nasdaq is down more than 2% despite there being no particular news of note. Nor has Nano-X said anything market-moving itself today.

I suspect investors are just still enthused by the rapid rise of this medical technology stock, and its disruptive business model. It is promising to build X-ray machines for $10,000 and then give them away, making money instead by charging for use of the machines.

Cartoon professor with a pointer explains why a stock arrow is rising

Image source: Getty Images.

Now what

In a business where X-ray machines ordinarily cost upward of $2 million, Nano-X's promise to give the machines away is certain to attract interest, even as its pay-per-use business model (the latest example of selling hardware as a service) promises to generate recurring revenue streams far into the future.

In the meantime, Nano-X remains a money-losing start-up with literally no revenue to speak of. It's an extremely speculative stock, albeit one that is rewarding its speculators richly today.