The United States and China are locked in a contest to be the first country to send humans to the lunar surface in half a century. But there's a developing twist: an emerging competition between American companies to build the landing vehicle that could win this new moon race for the US.

Not one to sit out a feud, SpaceX CEO Elon Musk didn't take lightly to interim NASA head Sean Duffy saying the firm is behind schedule.

Elon Musk is taking aim at the head of NASA amid news that the U.S. space agency may consider companies other than SpaceX to build lunar landers.