Conventional Prompt Global Strike and Long-Range Ballistic Missiles: Background and Issues [Updated December 16, 2020] [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 attacks against targets around the world in under an hour. Hypersonic weapons, like all long-range ballistic missiles, can travel faster than Mach 5, or about 1 mile to 5 miles per second. This interest 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 glider atop a ballistic missile booster or shorter-range rocket systems, and hypersonic cruise missiles that would use scramjet technologies. [...] This report provides an overview of the rationale for the PGS [prompt global strike]/prompt strike mission and the possible deployment of conventional warheads on long-range ballistic missiles or boost-glide systems in support of this mission. It then reviews the Air Force and Navy efforts to develop these systems. It summarizes congressional reaction to these proposals, and provides a more detailed account of the issues raised by these concepts and programs."
CRS Report for Congress, R41464
Congressional Research Service: https://crsreports.congress.gov/