DARPA and the U.S. Air Force are building something that sounds like it belongs in a science fiction novel: a reusable hypersonic strike aircraft that flies above Mach 5, launches from a conventional runway, strikes targets thousands of miles away, and lands back at base to do it again the next day. The programme is called NextRS — Next Generation Responsive Strike. If it works, it will create a capability that no nation has ever possessed: routine, on-demand hypersonic strike from the continental United States against any target on Earth, with turnaround times measured in hours rather than the months required to build and position a carrier strike group.

Beyond the B-21

The B-21 Raider is the world’s most advanced stealth bomber. It is designed to penetrate the most sophisticated air defences on Earth using low observability — flying slowly, quietly, and invisibly. It is a masterpiece of stealth engineering. And it may already be conceptually obsolete.

The problem with stealth is that it is a cat-and-mouse game. As sensor technology improves — quantum radar, passive detection, space-based infrared tracking — the window of guaranteed invisibility narrows. A Mach 5+ aircraft does not need to be invisible. It needs to be faster than the kill chain that detects, tracks, and engages it. At Mach 5, an aircraft covers a mile every second. By the time an air defence system detects, classifies, assigns, and launches against it, the target has moved dozens of miles. The geometry of interception becomes nearly impossible with current technology.

How It Might Work

DARPA has not released detailed specifications, but the broad architecture is understood from patent filings, budget documents, and congressional testimony. NextRS would likely use a combined-cycle propulsion system — turbine engines for takeoff and subsonic flight, transitioning to scramjet propulsion above Mach 3. The scramjet — supersonic combustion ramjet — uses atmospheric oxygen rather than carried oxidiser, making it far more efficient than a rocket. It is the same technology that powered NASA’s X-43 to Mach 9.6 in 2004 and the Air Force’s X-51 Waverider to Mach 5.1 in 2013. The difference is reusability. The X-43 and X-51 were expendable test vehicles. NextRS is designed to land, refuel, and fly again — potentially the same day. That transforms hypersonic strike from a one-shot capability into a persistent one.

The Strategic Calculation

A fleet of NextRS aircraft based in the continental United States could reach any target on Earth within two hours. No forward basing required. No carrier strike groups needed. No overflight permissions. No tanker support for the strike itself. For the Pentagon, this solves the central problem of great-power competition: how to project force against adversaries whose anti-access systems are specifically designed to keep American carriers, bombers, and fighters at arm’s length. You cannot deny access to something that arrives at Mach 5 from 6,000 miles away. The B-21 will be the backbone of American strategic bombing for decades. But NextRS represents the generation after — a world where speed replaces stealth as the primary means of survival, and where the tyranny of distance dissolves at five times the speed of sound.

Sources: 19FortyFive, DARPA, Air & Space Forces Magazine