Bezos’s aerospace firm, Blue Origin, turned up the temperature on Monday, by filing a protest against NASA’s choice of Musk’s SpaceX for a mission to the Moon. Earlier this month, NASA awarded SpaceX a $2.9 billion contract to build a lunar lander. Blue Origin and defense contractor Duentics had also submitted proposals for the project. NASA had been expected to choose two of the three firms, to ensure they had a backup and a healthy dose of competition. But the space agency said it plumped for a sole awardee due to budgetary constraints. [Read: 3 new technologies ecommerce brands can use to connect better with customers] The explanation hasn’t satisfied Blue Origin. The company has now filed a 50-page protest with the federal Government Accountability Office (GAO) over the decision. The firm argues that it wasn’t given a chance to revise its bid after the funding requirements changed, the New York Times reports. The protest further claims that NASA had misjudged aspects of Blue Origin’s proposals, while downplaying the risks in SpaceX’s design. In a statement, Blue Origin said NASA had “moved the goalposts at the last minute.” Inevitably, Elon Musk responded to the complaint by tweeting a penis joke.

— Elon Musk (@elonmusk) April 26, 2021 The two richest people in the world have been battling over the cosmos since a 2004 dinner meeting. At the time, the duo were only getting warmed up for their space race.

It was one of their few in-person interactions. The conversation they had perfectly captures the different approaches they’ve taken to space exploration. Here’s the story ? pic.twitter.com/g8hAsEj3d4 — Trung Phan ?? (@TrungTPhan) March 1, 2021 Musk recounted their meeting to author Christian Davenport for his book, “The Space Barons.” He recalled warning Bezos that SpaceX had already tested some of the Blue Origin’s ideas: The two tycoons have been trading barbs and competing for contracts ever since.

— Jeff Bezos (@JeffBezos) December 22, 2015 With no rapprochement in sight, it might be time to settle their 15-year feud the old-fashioned way: with a fight. In zero-gravity. May the best astronaut win.