An anonymous reader writes "The Diplomat's Zachary Keck wonders why the U.S. government is doubling down on missile defense systems even as hypersonic missiles threaten to render them obsolete. Keck notes that hypersonic missiles pose two distinct challenges to current missile defense systems. First, they travel far faster than the missiles the defense systems are designed to intercept. Second, they travel at lower altitudes and possess greater maneuverability than the missiles the current systems have been built to destroy. Nonetheless, the U.S. was planning on spending $2 billion a year on missile defense through 2017, and now the Pentagon is asking for an additional $4.5 billion over the next five years."