While this latest test doesn’t make nuclear-powered rocket engines viable just yet, it’s an important step on the journey.

This is a similar reaction to photosynthesis in plants, which produces glucose instead of rocket fuel. In this case, the astronauts created the hydrocarbon ethylene, which can be used as rocket fuel.

Investors are rocking for Rocket Lab (RKLB-0.99%). Shares of the U.S.-New Zealand maker of small rockets and even smaller satellites rocketed 30% higher in a single day earlier this week after ...