Facts History Explained How ScramJet Engine Works

Facts History Explained How ScramJet Engine Works
The Advanced Technology Vehicle (ATV), a sounding rocket (research rocket) with a solid booster carrying advanced scramjet engines, was successfully flight-tested from the launch pad of the Sathish Dhawan Space Centre, also known as Sriharikota Range (SHAR), at Sriharikota on Sunday, August 28, 2016

The ATV rocket weighed 3,277 kg during lift-off

With this, India became the fourth country to demonstrate the flight testing of a scramjet engine. This mission is a milestone for ISRO’s future space transportation system.

India is the fourth country to demonstrate the flight testing of Scramjet Engine after the United States, Russia and European Space Agency.

The scramjet engine is used only during the atmospheric phase of the rocket’s flight.

The test-flight is maiden short duration experimental test of ISRO’s scramjet engine with a hypersonic flight at Mach 6 (six times the speed of sound).

Two scramjet engines were “hugging” the rocket on its sides and when the rocket reaches a height of 11 km the scramjet engines would start breathing air.

Because the scramjet uses external air for combustion, it is a more efficient propulsion system for flight within the atmosphere than a rocket, which must carry all of its oxygen. Scramjets are ideally suited for hypersonic flight within the atmosphere.

If you look at the schematics of a Scramjet (or Supersonic Combusting ramjet), air gets sucked in from the front, fuel burns in middle and exhaust gas comes out of the back generating thrust.

Scramjet engines obtain oxygen from the atmosphere by compressing the incoming air before combustion at hypersonic speed. It uses hydrogen as fuel and the oxygen from the atmospheric air as the oxidiser.

Scramjet engines will help bringing down launch cost by reducing the amount of oxidiser to be carried along with the fuel.

Scramjet engines designed by ISRO uses hydrogen as fuel and the oxygen from the atmospheric air as the oxidiser.

ISRO plans to use the scramjet technology for its Avatar program.

ISRO currently uses rocket launch vehicles like the PSLV to deliver satellites into orbit.
PSLVs are expendable, meaning that can only be used once, and are designed to carry both fuel and oxidizer with for launch.
Scramjets use ambient air to burn fuel, thus saving the need to carry an oxidizer thus increasing the payload of a craft.

Air- Breathing rocket systems are the ones which use the atmospheric oxygen from their surroundings and burn it with the stored on- board fuel for producing the forward thrust in contrast to the conventional chemical rocket systems which carry both the oxygen and the fuel on-board. As a result, the Air-Breathing systems become much lighter and more efficient leading to reduced overall costs. As the Air- Breathing systems have the capability to operate only during the atmospheric phase of flight, they always have to be adopted along with the conventional chemical rockets, for meeting the final orbital velocity requirements.

A good example of Air-Breathing engines is the Turbojet engines used in aircrafts; however, they have limitations in operating only up to a maximum of Mach number 3. To travel beyond these Mach number regimes, SCRAMJET propulsion is the only viable option. The development of SCRAMJET system is quite complex and it involves a number of technological challenges, especially the ones related to the mixing of very high speed air (velocity around 1.5 km/s) with fuel, achieving stable ignition and flame holding in addition to ensuring efficient combustion, within the practical length of the combustor.

In the coming years, ISRO is planning to flight test an integrated SCRAMJET propulsion system comprising of air-intake, combustor and nozzle, by using a cost effective two stage RH-560 sounding rocket. Development of such a high technology system will come in a big way towards meeting the futuristic space transportation needs of our country.

ISRO claims that using Avatar for satellite launches will cut down launch costs by half. Since there are no rotating parts in a scramjet, the chances of failure are also measurably reduced.

Year 2005 –
The Thiruvananthapuram-based Vikram Sarabhai Space Centre (VSSC) of the Indian Space Research Organization (ISRO) designed and ground-tested a scramjet in 2005.
A press release stated that stable supersonic combustion was demonstrated in ground testing for nearly seven seconds with an inlet Mach number of six.

Year 2010-
In 2010, a flight test of Advanced Technology Vehicle (ATV-D01) with a passive scramjet engine combustor module was conducted. It was a suborbital ballistic trajectory based experiment using a two-stage RH-560 sounding rocket.

The HSTDV is a technology demonstrator under development by the DRDO. It has been ground-tested at hypersonic speeds for 20 seconds.

It will take many years before a commercial rocket powered by a scramjet engine takes to the sky as there are several challenges to be overcome. One challenge will be to test the engine at higher Mach speeds and prolong the period of combustion. Since the scramjet comes into play only when the rocket goes beyond Mach 5, an engine that initially works at subsonic speed (as a ramjet) and later as a scramjet has to be developed. But as in the case of the successful test flight of a reusable vehicle, the first experimental flight using a scramjet engine is a technological demonstration of ISRO’s capability and will go a long way in redefining its position as one of the leading space agencies in the world.


China - Year 2014-15
In August 2015, it was reported that a Chinese researcher had been awarded for the successful development and test flight of a new scramjet engine, the first of its kind in China. This would make China the second country in the world, after the United States, to have successfully test flown a scramjet. A new near-hypersonic drone, with a variable-cycle turbo-ramjet engine, has also been flown. It is reportedly the fastest air-breathing recoverable vehicle in the world

It was later revealed that the first flight of a Waverider-like scramjet-powered vehicle occurred in 2011, with flight tests completed by 2014.


Russia –
The first working scramjet in the world "GLL Holod" flew on 28 November 1991, reaching a speed of Mach 5.8.
However, the collapse of the Soviet Union stopped the funding of the project.

On November 17, 1992, Russian scientists with some additional French support successfully launched a scramjet engine named "Holod" in Kazakhstan6.

 From 1994 to 1998 NASA worked with the Russian Central Institute of Aviation Motors (CIAM) to test a dual-mode scramjet engine and transfer technology and experience to the West. Four tests took place, reaching Mach numbers of 5.5, 5.35, 5.8, and 6.5. The final test took place aboard a modified SA-5 surface-to-air missile launched from the Sary Shagan test range in the Republic of Kazakhstan on 12 February 1998.

Brazil
The 14-X is a Brazilian hypersonic aircraft, named in tribute to the 14-bis of Alberto Santos-Dumont. This aircraft is equipped with a scramjet engine, which is integrated into the fuselage and has no moving parts. The operating principle is that, during flight, the air is compressed by the geometry and speed of the vehicle and directed to the engine at the bottom of the aircraft. Hydrogen is used as the fuel. The vehicle will utilize the “Waverider” concept.


USA -
In the 1950s and 1960s a variety of experimental scramjet engines were built and ground tested in US and the UK. In 1964, two physicists - Dr. Frederick S. Billig and Dr. Gordon L. Dugger - submitted a patent application for a supersonic combustion ramjet. In 1981 tests were made in Australia under the guidance of Professor Ray Stalker. First successful flight test of Scramjet was performed by Russia in 1991.


Scram -
From 1962–1978, the Johns Hopkins Applied Physics Laboratory (APL) undertook a classified program (declassified in 1993) to develop a family of missiles called SCRAM8 (Supersonic Combustion RAmjet Missile)

On July 30, 2002, the University of Queensland's HyShot team conducted the first ever successful test flight of a scramjet.

On Saturday, March 25, 2006 researchers at the University of Queensland conducted another successful test flight of a HyShot Scramjet at the Woomera Test Range in South Australia. The Hyshot III with its £1,200,000 engine made an apparently successful flight (and planned crash landing) reaching in the order of 7.6 Mach.

NASA's Hyper-X program is the successor to the National Aerospace Plane (NASP) program which was cancelled in November 1994. This program involves flight testing through the construction of the X-43 vehicles. NASA first successfully flew its X-43A scramjet test vehicle on March 27, 2004

The Guinness Book of Records certified the X-43A's flight as the current Aircraft Speed Record holder on 30 August 2004. The third X-43 flight set a new speed record of 6,600 mph (10,620 km/h), nearly Mach 10 on 16 November 2004. It was boosted by a modified Pegasus rocket which was launched from a Boeing B-52 at 13,157 meters (43,166 ft.). After a free flight where the scramjet operated for about ten seconds the craft made a planned crash into the Pacific Ocean off the coast of southern California. The X-43A craft were designed to crash into the ocean without recovery. Duct geometry and performance of the X-43 are classified.

How do ramjets and scramjets work?
Ramjet is subsonic and Scramjet is Supersonic Engine both use nearly same technology.
When mounted on a high speed aircraft, large amounts of surrounding air are continuously brought into the engine inlet because of the forward motion of the aircraft. The air is slowed going through the inlet, and the dynamic pressure due to velocity is converted into higher static pressure. At the exit of the inlet, the air is at a much higher pressure than free stream. While the free stream velocity may be either subsonic or supersonic, the flow exiting the inlet of a ramjet is always subsonic. The flow exiting a scramjet inlet is supersonic and has fewer shock losses than a ramjet inlet at the same vehicle velocity. In the burner, a small amount of fuel is combined with the air and ignited. In a typical engine, 100 pounds of air/sec. is combined with only 2 pounds of fuel/sec. Most of the hot exhaust has come from the surrounding air. Flame holders in the burner localize the combustion process. Burning occurs subsonically in the ramjet and supersonically in the scramjet. Leaving the burner, the hot exhaust passes through a nozzle, which is shaped to accelerate the flow. Because the exit velocity is greater than the free stream velocity, thrust is created as described by the general thrust equation. For ramjet and scramjet engines, the exit mass flow is nearly equal to the free stream mass flow, since very little fuel is added to the stream.

The thrust equation for ramjets and scramjets contain three terms: gross thrust, ram drag, and a pressure correction. If the free stream conditions are denoted by a "0" subscript and the exit conditions by an "e" subscript, the thrust F is equal to the mass flow rate m dot times the velocity V at the exit minus the free stream mass flow rate times the velocity plus the pressure p difference times the nozzle exit area:

F = [m dot * V]e - [m dot * V]0 + (pe - p0) * Ae

Watch Video How the USAF X-51A Scramjet Works |




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