Solid Fuel Ducted Ramjet Missiles of India (SFDR)


This article defines the Solid Fuel Ducted Ramjet system and describes its development, mechanism, uses, and importance to India.


Solid Fuel Ducted Ramjet is a missile propulsion system based on the Ramjet Engine principle. It utilizes solid fuelled air-breathing Ramjet, which makes it light in weight and carries more fuel. This propulsion system can carry larger payloads as it does not require oxidizers. It takes oxygen from the atmosphere itself while in the air.

The Solid Fuel Ducted Ramjet is a long-range missile with an operational range of approximately 350km, and its maximum speed is Mach 4.5. It can also fly up to the altitude of 20 km.


The evolution and development of the ramjet engine as the propulsion system for missiles flying at supersonic speeds can be seen since World War 2 by the U.S. Navy.

It is a form of the air-breathing jet engine which uses the vehicle’s forward motion to compress the incoming air for combustion without rotating the compressor. The injected fuel in the combustion chamber is mixed with the hot compressed air and thus ignites. It works the most efficiently at the Supersonic speed and is not very efficient at the hypersonic speed.


 Since it improves the ramjet engines, it is known as the Scramjet i.e. supersonic Combustion Ramjet. Like Ramjet, the Scramjet engine also requires an assisted take-off to accelerate it to the speed it can produce thrust. It works the most efficiently at supersonic speeds between Mach 3 and Mach 6.

The exit flow from the inlet of a scramjet engine is supersonic, unlike the ramjet engine with subsonic exit flow from the inlet.


The word mach is named after the 19th-century scientist Ernst Mach who contributed to the field of the speed of sound. One mach is equal to 1195 km/hr in the air. If any object is said to be flying at the speed of mach 1, it means that it is flying at the speed of sound.

The speed less than Mach 1, typically around 0.8 Mach, is called subsonic. Transonic speed ranges between 0.8 to 1.2 Mach. Supersonic speed, meanwhile, has a range of between Mach 2 and 5. On the other hand, the hypersonic speed range of speed is more than Mach 5.


The Solid Fuel Ducted Ramjet Missiles in India are built by the Defence Research and Development Organization of India (DRDO) in collaboration with the Research Centre Imarat (RCI) in Hyderabad. The development of this missile propulsion system began in 2013 with the five-year deadline to begin actual demonstrations.


The Defence and Research and Development Organization of India was formed in 1958 from the amalgamation of the Technical Development Establishment (TDE) of the Indian Army and the Directorate of Technical Development and Production (DTDP) with the Defence Science Organization (DSO). It is the research and development wing of the Ministry of Defence, Government of India. It covers various disciplines like aeronautics, armaments, electronics, combat vehicles, engineering systems, instruments, missiles, etc.

The vision of the DRDO is to empower the nation with state-of-the-art indigenous Defence technologies and systems.

 Some of the major developments by DRDO in the defense sector are the Prithvi series of missiles; light-combat aircraft, Tejas; multi-barrel rocket launcher, Pinaka; air defense system, Akash; a wide range of radars and electronic warfare system.


There are two variants of the SFDR which are being developed in India. These are Surface-to-air missiles and Air-to-Air missiles. At present, India is mainly concerned with developing Air-to-Air missile systems.

Air-to-Air versions

The Air-to-Air missiles are used to destroy the other aircraft. They use rocket motors which can use either solid fuel or sometimes liquid fuel. Air-to-Air missiles are further divided into two groups. These are short-range and Medium or Long-range. 

Short-range air-to-air missiles (SRAAMs) are those that can work within the visual range of up to 30km. They are known as “dogfight” missiles. 

Both Medium and Long range missiles (MRAAMs and LRAAMs) fall under the category of beyond visual range missiles (BVRAAMs).

Some of India’s Air-to-Air missiles are:

  • Astra – It is a long-range radar-guided missile. It was designed by the DRDO and was manufactured by Bharat Dynamics Limited. Different variants of Astra are Astra Mk. 1, Astra Mk. 2, Astra Mk. 3, IR, VL-SRSAM.
  • K-100 missile – It uses internal navigation and active radar homing. It was built in collaboration with Russia.

Surface-to-Air versions

As the name suggests, this version of missiles is launched from the ground to destroy the aircraft. They are also known as the ground-to-air missiles (GTAMs) or surface-to-air guided weapons (SAWG)

Some of India’s Surface-to-Air missiles are:

  • Akash – A medium-range surface-to-air missile developed by the DRDO and produced by Bharat Dynamics Limited.
  • Trishul – A short-range low-level surface-to-air missile.


The first testing of the SFDR took place on May 30, 2018, and it demonstrated a nozzle-free booster for the first time in India. 

  • According to the report of the Economic Times, it failed to activate the second ramjet engine stage while it was tested.
  • SFDR’s second testing took place on February 08, 2019, and at this stage, its Ramjet engine was tested.
  • The Solid Fuel Ducted Ramjet Missile was final testing was done at Chandipur, Odisha on March 05, 2021. 


For India to possess the SFDR technology is a great achievement as only a few developed nations in the world have it at present.

The current situation suggests that India is at risk of external attacks from her hostile neighbors like China and Pakistan. It becomes crucial for India to solidify its defense system in such situations. 

It makes the country’s defense system stronger as the use of air-to-air missiles using the SFDR can hit the target more effectively with supersonic speed and high maneuverability.

The successful demonstration of the Solid Fueled Ducted Ramjet technology will further enable the DRDO to develop more indigenous long-range air-to-air missiles.

It will build more opportunities for the projects as Aatmanirbhar and Make-In-India.