Soon, America's older warbirds could see their claws sharpened significantly, as it was announced in October that Raytheon Missiles and Defense had been selected to build and demonstrate a ramjet-rotation detonation engine (ram-RDE)-powered, high-speed missile intended to be launched by fourth-generation fighters under a Defense Advanced Research Projects Agency (DARPA) funded program.

The agency awarded the Phase 2 contract for the Gambit program to the aerospace giant to develop the rotating detonation engine. This type of engine is seen as being more compact, while providing a higher efficiency propulsion source than conventional missile propulsion and offers the potential for lower costs.

The Gambit program is now solely focused on developing Rotating Detonation Engines (RDEs) as a new class of propulsion to enable standoff strikes of time-critical targets from fourth-generation fighters at a campaign scale.

According to DARPA, "Current propulsion technologies (e.g. conventional rockets, ramjets, and gas-turbine engines) have limitations in maximum range, speed, and/or affordability that hinders their ability to meet the Gambit program objectives. RDEs are more compact than conventional ramjets, which allows them to carry more fuel. Additionally, RDEs are less complex than gas turbine engines. The combination of these two factors enable RDEs to affordably meet the Gambit program objectives."

Gambit: Phases 1 and 2

The program aims to develop and demonstrate RDE technology in a full-scale freejet test. Phase 1's focus has been on the preliminary design of the freejet test article and substantiating the design with combustor and inlet testing.

Phase 2 of the Gambit program will next focus on the detailed design, fabrication, and testing of the freejet test article. Gambit could lay the foundation for future potential prototype weapon development, DARPA further suggested.

Gambit has been seen as the first-of-its-kind engine development program that could support future weapons systems for multiple military services. According to Raytheon, the compact nature of the engine and its efficient combustion provide a boost in range and speed relative to current long-range weapons, allowing the ability to quickly respond to advanced threats.

"This is a revolutionary propulsion system," said Colin Whelan, president of Advanced Technology at Raytheon. "We're leveraging existing digital design tools and experience from across the entire RTX business to rapidly prototype this next-generation strike weapon and mature the technology."

Under the terms of the DARPA contract, RTX will rely heavily on the iterative development of performance models, which will be anchored by real-world data from incremental system tests. This proven method accelerates learning to provide more certain flight test outcomes, saving both time and cost. Future optional phases of the Gambit program will shift to building hardware to conduct a flight weight free-jet test.

With this contract, RTX became the first company to apply rotating detonation engine technology into an actual test system.

Advantages of the RDE

An RDE engine could have several advantages – including the fact that it is hard to disable, and easy to mass produce yet doesn't require exotic metals and ceramics. Moreover, RDEs are lightweight and compact. They can also be configured with ramjets, gas turbines, and rockets for a wide range of possible applications.

According to a report from NewAtlas.com, in an RDE, a combustible mixture of fuel and air is introduced into a gap between two coaxial cylinders, with the gap sealed at one end and the other end forming into a nozzle. When that mixture is ignited, it burns in a very special way, and the combustion takes the form of a supersonic wave that travels around inside the gap.

"As more fuel and air is introduced at the top, the wave continues going around in the gap, producing more and more heat and pressure, and is forced down until it exits through the nozzle, creating thrust," David Szondy wrote for NewAtlas.

A Specific Role for the RDE – Blockading China?

As previously reported, RDE technology could eventually also lead to smaller weapons that offer the same range and speed as today's missiles. That could increase the capabilities of fourth-generation aircraft, but it would further allow stealth aircraft like the F-35 to carry more munitions inside their internal weapons bays.

Alex Hollings noted, that the reference to Gambit's use in an "anti-access/area denial (A2AD) environment" could pertain to anywhere American forces are squaring off against a near-peer adversary. Yet there is one such environment that has been the focus of multiple U.S. military efforts in recent years: the 1,000-mile-plus area denial bubble extending from Chinese shores, thanks to a growing array of anti-ship weapon systems.

RDE could help increase the range of U.S. missiles so that warships don't have to sail into harm's way.

Moreover, the technology could in the longer term find its way into the fuselage of an aircraft as the primary means of propulsion – and perhaps even be employed similarly on warships. RDE is thus more than just about the engines on missiles; it would be the future propulsion system for the U.S. military.

Author Experience and Expertise

Peter Suciu is a Michigan-based writer. He has contributed to more than four dozen magazines, newspapers, and websites with over 3,200 published pieces over a twenty-year career in journalism. He regularly writes about military hardware, firearms history, cybersecurity, politics, and international affairs. Peter is also a Contributing Writer for Forbes and Clearance Jobs. You can follow him on Twitter: @PeterSuciu.