NASA aimed for a Saturday launch of its new moon rocket, after fixing fuel leaks and working around a bad engine sensor that foiled the first try.

The inaugural flight of the 322-foot rocket—the most powerful ever built by NASA—was delayed late in the countdown Monday. The Kennedy Space Center clocks started ticking again as managers expressed confidence in their plan and forecasters gave favorable weather odds.

Atop the rocket is a crew capsule with three test dummies that will fly around the moon and back over the course of six weeks—NASA's first such attempt since the Apollo program 50 years ago.

Many around the world will watch eagerly this Saturday as NASA launches Artemis I, the agency's first Moon exploration mission since the 1970s.

The spectacle involves the most powerful rocket in the world: the Space Launch System (SLS). Standing at nearly 100 meters tall and weighing more than 2,600 tons, the SLS produces a massive 8.8 million pounds of thrust—(more than 31 times the thrust of a Boeing 747 jet).

But it's not just amazing engineering that's behind rocket science and space exploration. Hidden within, there's clever chemistry that powers these fantastic feats and sustains our fragile life in space.

The fuel and the spark

To launch a rocket into space, we need a chemical reaction known as combustion. This is where fuels are combined with oxygen, producing energy as a result. In turn, that energy provides the push (or thrust) needed to propel mammoth machines like the SLS into Earth's upper atmosphere and beyond.

Much like cars on the road and jets in the sky, rockets have engines where combustion takes place. SLS has two engine systems: four core stage RS-25 engines (upgraded space shuttle engines) and two solid rocket boosters.