Hypersonic Weapon Startup Castelion Has First Prototype Missile Test

WASHINGTON—Castelion, a startup trying to build a hypersonic weapon for the Pentagon, tested its system for the first time, it told Reuters on Monday, as a growing group of small hypersonic arms makers challenge large defense contractors with less expensive, rapidly produced products. The United States and China are engaged in an arms race to develop the most lethal hypersonic weapons, which travel in the upper atmosphere at more than five times the speed of sound and are designed to evade traditional defenses. “This test flight, the first of many planned for this year, demonstrates our rapid development approach and is a major milestone for the company. We now have a low-cost hypersonic test platform ready to launch on demand,” Bryon Hargis, Castelion’s CEO and co-founder, told Reuters in a statement....