Why the US is struggling to keep pace in the hypersonic weapons race As China and Russia move ahead, a defense expert breaks down the technical hurdles and testing constraints slowing U.S. hypersonic development. NEW You can now listen to Fox News articles! The U.S. has spent years racing to develop hypersonic weapons to compete with China and Russia, but delays, shifting programs and limited testing capacity are raising concerns that Washington remains in a catch-up phase in a technology that