DARPA's New Gambit Missile Could Drive China Crazy

The Defense Advanced Research Projects Agency (DARPA) reveals its new weapon, the “Gambit” hypersonic missile.

The birth of the Gambit missile

Last year, the  Defense Advanced Research Projects Agency (DARPA)  unveiled its new war project: the Gambit hypersonic missile in a surprise tactical maneuver. This classified program seeks to revolutionize modern warfare through advanced propulsion technology.

Aiming to dominate the skies and seas, Gambit explores an innovative method of propulsion. This system could radically change weapons development and the speed and efficiency of aircraft and warships.

The rotary detonation engine (RDE) is the heart of this innovation. This technology promises to be lighter and more powerful than current jet engines, significantly improving range and fuel efficiency.

The revolution of RDE engines

Although the Gambit is the protagonist, it is not the only one to use RDE technology. However, these advances have flown under the media radar, except for Steve Trimble, Defense Editor of Aviation Week & Space Technology, who enlightens us about its strategic importance.

RDE engines, although not a common topic of conversation, are emerging as a decisive factor in the current hypersonic arms race. The United States sees them as a tool to counteract its adversaries’ tactical and strategic advantages.

These engines, which have been the subject of speculation for decades, promise to cross the line between theory and warfare practice very soon.

Impact of RDE on Modern Warfare

In theory, ROEs could revolutionize missile design, offering superior range and speed. This could result in more compact but equally lethal weapons.

In military aviation, RDEs could provide fighters with range and speed advantages, minimizing the need for intensive maintenance. These engines could replace current afterburners, drastically reducing fuel consumption.

These engines really shine in the propulsion of future non-nuclear warships, improving energy efficiency and range while positively impacting the Navy’s budget.

The RDE: a history of innovation

The idea of ​​RDE engines dates back to the 1950s. Arthur Nicholls of the  University of Michigan pioneered the development of a functional RDE design.

RDEs are an evolution of pulse detonation engines (PDE) and pulsejets. Although they sound complex, their operation is essential to understand their potential on the battlefield.

Pulsejets mix air and fuel in a chamber, detonating them in rapid pulses. PDE and RDE take advantage of detonation, a much more explosive and efficient process, unlike deflagration used in other engines.

Supersonic detonation: key to RDE

Detonation in RDE engines is a supersonic process, much more explosive than the subsonic deflagration common in jet engines. In a pulse detonation engine, the air-fuel mixture detonates, creating a pressure wave that compresses and heats the remaining fuel, resulting in a controlled and efficient explosion.

Energy efficiency is a critical aspect of RDE motors. These engines produce more thrust with less fuel, allowing for lighter loads and longer ranges. The speed of these detonations far exceeds that of the deflagration, reaching up to 2,000 meters per second.

In 2008, the Air Force Research Laboratory achieved a milestone by creating the first manned aircraft powered by pulsed detonation, using a Long-EZ model from Scaled Composites. With Pete Siebold as a pilot, the plane exceeded 120 miles per hour, demonstrating the potential of PDE engines in aviation.

Revolution in fuel efficiency

Fred Schauer of the AFRL Propulsion Directorate highlighted the superiority of PDE engines over conventional ones in terms of fuel efficiency, with an estimated savings between 5 and 20 percent. These advances could lead to speeds exceeding Mach 4 in aircraft, especially if combined with technologies such as scramjets.

The concept of rotary detonation engines (RDE) takes PDE technology to a new level. Instead of expelling the detonation wave, it circulates in a channel inside the engine, generating continuous thrust and increasing efficiency.

As Trimble points out, ROEs generate a pressure surge during detonation, unlike jet engines, which lose pressure. This superior efficiency translates into a significant jump in specific impulse and potentially an increase in the range of supersonic aircraft.

The materialization of RDE engines

In 2020, the University of Central Florida, in collaboration with the Air Force Research Laboratory’s Rotary Detonation Rocket Engine Program, created the first operational RDE. This engine demonstrated that the RDE theory was feasible, generating 200 pounds of thrust in laboratory tests.

Companies like  Pratt and Whitney have begun to follow suit in developing RDE engines. On July 18, 2022,  DARPA  announced a “Proposer Day” for its  Gambit missile program, seeking to partner with companies to develop this technology.

Gambit: a weapon for the future

DARPA‘s  Gambit program aims to develop an RDE propulsion system to make low-cost, long-range supersonic weapons. It will focus on air-to-ground applications in anti-access/area denial (A2AD) environments.

The development of Gambit will be divided into two 18-month phases, with the completion of preliminary designs and full-scale testing. This program could have significant implications in regions such as the Pacific, where US forces face strategic challenges, especially with growing Chinese military influence.