// PROPULSION SYSTEMS AND ENGINE TECHNOLOGY TERM
Turbo-Ramjet
A turbo-ramjet is a hybrid jet engine that combines a turbojet and a ramjet in a single system. It uses the turbojet for takeoff and acceleration to supersonic speeds, then transitions to the ramjet for more efficient operation at very high, hypersonic speeds.
TECHNICAL DEFINITION
A turbo-ramjet is a type of combined cycle air-breathing propulsion system that integrates a gas turbine (turbojet) with a ramjet duct to achieve efficient operation across a wide flight envelope from subsonic to hypersonic (Mach 5+) speeds. The engine operates as a turbojet at lower Mach numbers and transitions to ramjet mode at high speeds, where the turbine is bypassed or shut down and combustion relies solely on ram-air compression.
BACKGROUND
A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion, but whereas a ramjet decelerates the air to subsonic velocities before combustion using shock cones, a scramjet has no shock cone and slows the airflow using shockwaves produced by its ignition source in place of a shock cone. This allows the scramjet to operate efficiently at extremely high speeds and does not require any moving parts.
READ MORE ON WIKIPEDIASYNONYMS & ALIASES
- air-turbo ramjet (ATR)
- turbine-based combined cycle (TBCC)
- combination engine
- multimode engine
- variable cycle engine
- wrap-around turbo-ramjet
USAGE NOTE
This engine concept is primarily studied for reusable hypersonic vehicles that need to take off from a runway and accelerate to extreme speeds within the atmosphere.
DEVELOPERS
Organizations developing technology related to Turbo-Ramjet.
An aerospace startup developing hypersonic aircraft powered by their proprietary 'Chimera' engine, a turbine-based combined cycle (TBCC) engine that functions as a turbojet at low speeds and a ramjet at high speeds.
A subsidiary of L3Harris Technologies, Aerojet Rocketdyne is a key developer of advanced propulsion, including ramjets, scramjets, and has extensive experience developing critical technologies for Turbine-Based Combined Cycle (TBCC) engines for hypersonic vehicles.
A subsidiary of RTX, Pratt & Whitney designed the historic J58 engine for the SR-71 Blackbird, which functioned as a turbo-ramjet. They continue to research and develop advanced propulsion systems for future hypersonic applications.
A world-leading producer of jet engines, GE Aerospace is actively involved in developing next-generation military propulsion systems, including adaptive cycle engines and technologies applicable to turbine-based combined cycle systems for high-Mach flight.
The advanced development division of Lockheed Martin, known for the SR-71. They are actively designing next-generation hypersonic platforms, like the conceptual SR-72, which are described as using a TBCC propulsion system to bridge the gap between turbojet and ramjet operational speeds.
The primary research and development arm of the U.S. Air Force. AFRL's Aerospace Systems Directorate leads and funds numerous programs to advance hypersonic propulsion, including testing and maturing Turbine-Based Combined Cycle engine concepts.
A British company developing the Synergetic Air-Breathing Rocket Engine (SABRE), an advanced combined-cycle engine that uses a revolutionary precooler to operate from standstill to over Mach 5, sharing principles with turbo-ramjet concepts.
A major defense contractor with deep expertise in hypersonic and advanced weapons systems. They are involved in the development and integration of ramjet and scramjet propulsion systems, a key component of combined-cycle engine technology.