Conventional Prompt Global Strike and Long-Range Ballistic Missiles: Background and Issues [Updated July 16, 2021] [open pdf - 1MB]
From the Introduction: "Members of Congress and Pentagon officials have placed a growing emphasis on U.S. programs to develop hypersonic weapons as a part of an effort to acquire the capability for the United States to launch prompt attacks against targets around the world. Hypersonic weapons, like all long-range ballistic missiles, can travel faster than Mach 5, or about 1 mile to 5 miles per second. The interest in these weapons is driven by both the perceived mission need for conventional prompt strike systems and concerns about falling behind Russia and China in the development of these technologies. The United States is pursuing two key technologies for this purpose: boost-glide systems that place a hypersonic glide vehicle (HGV) atop a ballistic missile booster or shorter-range rocket systems, and hypersonic cruise missiles that would use scramjet technologies."
CRS Report for Congress, R41464
Congressional Research Service: https://crsreports.congress.gov/