Elon Musk Dominates Space Launch. Rivals Are Calling Foul.

Elon Musk aggressively elbowed his way into the space launch business over the past two decades, combining engineering genius and an entrepreneurial drive with a demand that the U.S. government stop favoring the big, slow-moving contractors that had long dominated the industry.

Today, it is Mr. Musk who is dominant. His company, SpaceX, is the primary provider of launch services to NASA and to the Pentagon. His rockets carry far more commercial satellites into orbit than anyone else’s, including those for his own Starlink communications network. He has set new standards for reaching space cheaply and reliably.

But in one striking way, the former outsider has come to resemble the entrenched contractors he once fought to topple: He is increasingly using his vast power and influence to try to keep emerging rivals at bay, his competitors say, even as his success is prompting qualms within the government about such heavy reliance on a mercurial billionaire.

The new generation of space entrepreneurs trying to emulate Mr. Musk is sufficiently concerned about what they see as his anticompetitive tactics that some of them are now willing to take him on publicly.

Tim Ellis started Relativity Space after being inspired by Mr. Musk’s pursuit of a rocket that could carry humans to Mars. Then he heard from other industry executives that individuals with ties to SpaceX were trying to block his efforts to raise money for his own Mars project.

Jim Cantrell worked with Mr. Musk at the founding of SpaceX in 2002. When he started to build his own launch company, Phantom Space, two potential customers told his sales team they could not sign deals because SpaceX inserts provisions in its contracts to discourage customers from using rivals.