Two days before US president Joe Biden and Chinese leader Xi Jingping held a frosty confab in Bali, a secret, autonomous spacecraft descended from its orbit hundreds of miles above the planet to land at Cape Canaveral. Its timing, however coincidental, served to underscore how the greatest tensions between China and the US may not be on land or sea. “I absolutely believe there need not be a new Cold War,” Biden told reporters after his meeting with Xi on Monday, Nov. 14. But there’s clearly a nascent Cold War-style arms race taking place in space, with nations testing and...