Space Defense Stocks Surge by 600 Billion Won in a Day: What Happened?

York Space Systems Inc. (YSS), a space-defense satellite manufacturer, closed at $31.24 on the New York Stock Exchange, up 10.62%. With trading volume surging well above its average, the company’s market capitalization swelled to about $3.99 billion (approximately ₩5.4 trillion), adding roughly $470 million (around ₩600 billion) in a single day.

Recently, York Space Systems secured an extension of the PExT satellite-communications demonstration project with NASA and Johns Hopkins APL through 2027. Against a backdrop of rising defense and communications-satellite demand, the stock is now trading at a growth-stock premium. The company also strengthened its production capacity and defense-constellation competitiveness by acquiring solid-propulsion specialist Orbion Space Technology, thereby internalizing electric-propulsion technology.

York Space Systems, a space-defense startup, went public on the NYSE in January 2026, raising $629 million (about ₩850 billion). Since then, it has expanded its role as a key supplier of low-Earth-orbit military satellites to the U.S. Space Development Agency (SDA). Wall Street firms such as JPMorgan are issuing buy recommendations on the “cost-efficient mass-satellite manufacturer” thesis, citing missile-defense demand for LEO satellites and a substantial pipeline of major defense and commercial contracts.