The Pentagon awards the Leidos company the contract to develop a new hypersonic aircraft within the framework of the secret Mayhem program.

Hypersonic technology continues to advance as fast as its name suggests, in an arms race powerfully reminiscent of the Cold War. As China and Russia successfully test their respective missiles capable of flying at more than five times the speed of sound (that is, more than 6,000 km/h), the US Air Force has just awarded the first contract for its plan to develop a reusable unmanned hypersonic combat aircraft.

As it shores up its new network of satellites designed to counter Chinese and Russian hypersonic threats and conducts tests of the ARRW, the first hypersonic missile successfully launched from an aircraft, the Pentagon wants to take the next step. And that is the objective of Project Mayhem (Project Chaos in Spanish), a secret program with which the US intends to overtake rival powers with an autonomous aircraft that is significantly cheaper and more versatile than hypersonic missiles.

To do this, the Pentagon has entrusted the manufacturer Leidos to develop an experimental design capable of demonstrating its ability to transport different types of payloads and carry out all kinds of intelligence, surveillance, and reconnaissance missions. Everything seemed to indicate that the chosen one would finally be the Lockheed Martin SR-72 which, in addition to its cameo in the latest Top Gun movie, still has to face some technological challenges.

However, the contract signed by the Pentagon with Leidos seems to dismiss this option and bet on a single scramjet engine to reach speeds above 6,000 km/h. In any case, there may be more than one project developing in parallel within Mayhem and the SR-72 can still put up a lot of trouble.

mayhem takes shape

The Air Force Research Laboratory (AFRL) has been commissioned to close a “single award, indefinite delivery/indefinite quantity” agreement, with a maximum limit of 313 million euros for the formally called Hypersonic Attack and ISR Project multimission.

“This program focuses on the delivery of a multi-mission capable hypersonic system with a standardized payload interface, providing significant technological advancement and future capability,” the Pentagon contracting journal reports. “Work will take place at Wright-Patterson Air Force Base, Ohio, and other potential test locations to be determined, and is expected to be completed by October 15, 2028.”

As confirmed by Leidos in a press release, a system requirements review (SSR) will be carried out first, followed by a conceptual design review (CoDR) using digital engineering. But what is more important is confirmation of the type of engine that will propel the aircraft: “The Mayhem system will use a scramjet engine to generate thrust, propelling the vehicle over long distances at speeds in excess of Mach 5.”

Ryan Leo, Mayhem Program Director, uses the same statement to boast of the “team assembled by Leidos, who combine exceptional experience with innovation. We are working with the best solution providers in the country in hypersonic vehicle technologies and propulsion. We are proud to contribute to this important national security mission.

The image shared by the company, which is nothing more than an illustration prior to the final design, shows an unmanned hypersonic aerial vehicle with a single engine. The fuselage is long and with the characteristic curved lines of hypersonic projectiles, as well as a delta wing configuration with a vertical tail.

Regardless of how it evolves in the next six years, what it has to meet is the goal set by the Pentagon in 2021: “transport payloads with a mass five times greater and a range twice greater than current technological capacity systems” . Those loadouts are described as “area effect” and “large unit” weapons for strike missions, and some sort of “sensitive” device to accomplish their ISR (initial intelligence, surveillance and reconnaissance) missions.

A very special engine

The Pentagon wants the result of Project Mayhem to be able to take off with its own means – lacking a mother platform – and to be reusable – discarding the rocket system. The only alternative that seemed possible was to use a kind of hybrid engine between that of a traditional aircraft for the first stages of the flight and a scramjet that starts working when it has reached a certain speed.

“This type of engine could revolutionize air travel and defense,” said Chris Combs, a specialist in hypersonic and aerospace engineering at the University of Texas at San Antonio. The scheme would use a conventional jet engine to take off and accelerate to around 3 times the speed of sound before transitioning to a scramjet capable of propelling the aircraft past 5 times the speed of sound. A challenge of aerospace engineering that moves in a very complex field and for which there is no known solution.

The compression system of a traditional jet turbine—like that of any aircraft today—impedes airflow by design. It can be seen with the naked eye in the large fan that the aircraft engines have in front. But on the other hand, a scramjet needs unobstructed airflow to function. A powertrain that satisfies both needs would have to merge both contradictory designs.

This type of engine, technically known as multi-cycle, is becoming a very important area of technological research. The manufacturer Rolls-Royce is working on it for use in a space launch craft and DARPA is doing the same with the AFRE Program (Advanced Full Range Engine, in Spanish), as indicated by Air Force Technology. It is not yet clear how Leidos will solve these problems if it goes with a single scramjet engine, information that will continue to come as development progresses.

Another of the challenges that those in charge of Project Mayhem will have to face is heat, since the entire aircraft must be prepared to withstand high temperatures due to friction. “Going at more than 5 times the speed of sound generates extreme levels of heat, driving the need for innovative materials, sensors, and electronics to withstand such speeds throughout their journey,” Dave Berganini said at the time. Vice President of Hypersonic and Attack Systems at Lockheed Martin.

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