India Indian Scramjet and Hypersonic Programs

Gautam

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These slides were most interesting to me (being a combustor guy myself, but at far lower regime of velocity):
Let me repost an old post of mine from SF. I think you will like it.

A few old photos & diagrams from DRDO's Scramjet test stand.
1630154961917.png

The test stand has a multi-strut based supersonic combustor. The schematic of the combustor is shown below:
1630155051486.png

As the schematic shows the combustor is divided into multiple sections each housing a symmetric array of struts. According to position the struts are given a Stage number. A strut is an angular device often used in aviation industry with the intention of bifurcating stream lines. Depending on the shape & size struts may be used to control turbulences, generate lift or drag etc.

In this case however struts are used as fuel injectors. So the struts will slice the supersonic stream inside the combustor & inject fuel into the stream. Thus these struts will be subjected to incredibly high pressures & temperatures during the operation of the scramjet. This posed a challenge of materials, an appropriate alloy had to be chosen for making the struts.

This is how DRDO described the material selection for a series of ground tests of the scramjet engine :
1630155071655.png

The engine was lit for 20 seconds using refined Kerosene as fuel & with Mach 2 as combustor entry speed. Remember this is from a paper published a few years back. The problems described here are solved. DRDO eventually settled on Nimonic C-263 alloy to make the struts. The alloy was further modified by DMRL before undertaking the flight test that last year. The combustor casing was made of an unnamed Nickel-based alloy.

The design of the struts were also a challenge. The struts faced very different pressures & temperatures depending on where they were placed. The Stage-I struts were subjected to a cooler undisturbed flow of air. Thus they did not need any additional cooling.

STAGE-I strut :
1630155101626.png

The Stage-I strut is the only un-cooled strut in the entire configuration. The leading edge radius is R1.5 with θwd =12°. A total of 110 injector holes are used, each of 0.5 mm diameter. The fuel injection happens in the direction perpendicular to the flow.

STAGE-II/III struts :
1630155118850.png

Stage-II & III struts have a common design. These are cooled struts with two-passages for the fuel to flow through them which act as a heat exchanger. The cooling is done by the Kerosene fuel itself. These struts also have 110 injector holes of 0.5 mm size. Perpendicular fuel injection pattern has been employed to inject the fuel.

Here is a photo of one of the Stage-II after the 20 sec ground tests :
1630155141434.png

The photo shows that the nose of the strut has undergone a significant degree of ablation. The strut survived the tests & remained thermo-structurally safe to be used for longer duration tests.

During later stages of ground tests when the size of the scramjet combustor was increased there was another stage of struts that was included.

STAGE-IV struts :
1630155169056.png

This is the newest addition to the family & carries the most complex design of them all. The trailing edge of the strut features a series of alternating wedges. The injection hole are made on the trailing edge, thus the fuel injection happens in the direction of the flow. Though exact numbers are unknown, the number of fuel injection holes are less than Stage-II/III.

Here is the general flow path configuration used for both simulations and ground testing :
1630155195944.png

The revised arrangement of the struts :
1630155223626.png

A new middle wall was introduced which allowed increasing the number of struts. Notice how there are 2 Stage-I struts instead of one. Increased fuel injection is needed for increasing the speed of the vehicle but it comes with problems. Increased number of struts & more injected fuel means significantly higher temperatures. Thus these modifications are introduced only after some breakthroughs have been made on the materials research side.

Here is the newer wind tunnel test model :
1630155250394.png
 

Lonewolf

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Let me repost an old post of mine from SF. I think you will like it.

A few old photos & diagrams from DRDO's Scramjet test stand.
View attachment 29739
The test stand has a multi-strut based supersonic combustor. The schematic of the combustor is shown below:
View attachment 29740
As the schematic shows the combustor is divided into multiple sections each housing a symmetric array of struts. According to position the struts are given a Stage number. A strut is an angular device often used in aviation industry with the intention of bifurcating stream lines. Depending on the shape & size struts may be used to control turbulences, generate lift or drag etc.

In this case however struts are used as fuel injectors. So the struts will slice the supersonic stream inside the combustor & inject fuel into the stream. Thus these struts will be subjected to incredibly high pressures & temperatures during the operation of the scramjet. This posed a challenge of materials, an appropriate alloy had to be chosen for making the struts.

This is how DRDO described the material selection for a series of ground tests of the scramjet engine :
View attachment 29741
The engine was lit for 20 seconds using refined Kerosene as fuel & with Mach 2 as combustor entry speed. Remember this is from a paper published a few years back. The problems described here are solved. DRDO eventually settled on Nimonic C-263 alloy to make the struts. The alloy was further modified by DMRL before undertaking the flight test that last year. The combustor casing was made of an unnamed Nickel-based alloy.

The design of the struts were also a challenge. The struts faced very different pressures & temperatures depending on where they were placed. The Stage-I struts were subjected to a cooler undisturbed flow of air. Thus they did not need any additional cooling.

STAGE-I strut :
View attachment 29742
The Stage-I strut is the only un-cooled strut in the entire configuration. The leading edge radius is R1.5 with θwd =12°. A total of 110 injector holes are used, each of 0.5 mm diameter. The fuel injection happens in the direction perpendicular to the flow.

STAGE-II/III struts :
View attachment 29743

Stage-II & III struts have a common design. These are cooled struts with two-passages for the fuel to flow through them which act as a heat exchanger. The cooling is done by the Kerosene fuel itself. These struts also have 110 injector holes of 0.5 mm size. Perpendicular fuel injection pattern has been employed to inject the fuel.

Here is a photo of one of the Stage-II after the 20 sec ground tests :
View attachment 29744
The photo shows that the nose of the strut has undergone a significant degree of ablation. The strut survived the tests & remained thermo-structurally safe to be used for longer duration tests.

During later stages of ground tests when the size of the scramjet combustor was increased there was another stage of struts that was included.

STAGE-IV struts :
View attachment 29745

This is the newest addition to the family & carries the most complex design of them all. The trailing edge of the strut features a series of alternating wedges. The injection hole are made on the trailing edge, thus the fuel injection happens in the direction of the flow. Though exact numbers are unknown, the number of fuel injection holes are less than Stage-II/III.

Here is the general flow path configuration used for both simulations and ground testing :
View attachment 29746
The revised arrangement of the struts :
View attachment 29747
A new middle wall was introduced which allowed increasing the number of struts. Notice how there are 2 Stage-I struts instead of one. Increased fuel injection is needed for increasing the speed of the vehicle but it comes with problems. Increased number of struts & more injected fuel means significantly higher temperatures. Thus these modifications are introduced only after some breakthroughs have been made on the materials research side.

Here is the newer wind tunnel test model :
View attachment 29750
Can these struts survive 300 sec ? as that would be the time required atleast for the range required from such a system , as at 2km/s it would cover 600 km and adding the glide phase which will be small it will get us to 750 km atmax ,but if burn time can be increased we can get more range .
 

Gautam

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Can these struts survive 300 sec ? as that would be the time required atleast for the range required from such a system , as at 2km/s it would cover 600 km and adding the glide phase which will be small it will get us to 750 km atmax ,but if burn time can be increased we can get more range .
These photos shown above are from experiments conducted many years ago. Getting a scramjet to run for any period of time on the ground is easier than doing the same in air.

A couple of years back ISRO was getting 250-280 sec on ground with their scramjet engine. DRDO was then still at that 120-130 sec level. Its only natural, ISRO started their scramjet project 5-6 years ahead of DRDO.

In Feb 2020, ISRO stated that they intend to test their scramjet at Mach 6-7 at 25 km height, expect a flight test in 1-2 years. If that test succeeds then ISRO can start working towards that 300+ sec burn time. DRDO will no doubt take longer to get there. Even if ISRO were to hand over their engine to DRDO, don't expect a fully ready hypersonic cruise missile to be ready in less than 5 years.

Also when you calculate the range of a scramjet powered cruise missile consider the fact that the engine can't work unless the air rushing through the intake is supersonic. So you need a solid booster to get you to that supersonic speed. That booster will push the missile to a significant distance before the missile goes supersonic & the booster can detach. Add that range to your calculation and you will see that a scramjet engine capable of 300 sec burn can easily get to 800 km+ distance.

Do we know the range of the 2 hypersonic cruise missiles DRDO is working on ?
 

Lonewolf

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These photos shown above are from experiments conducted many years ago. Getting a scramjet to run for any period of time on the ground is easier than doing the same in air.

A couple of years back ISRO was getting 250-280 sec on ground with their scramjet engine. DRDO was then still at that 120-130 sec level. Its only natural, ISRO started their scramjet project 5-6 years ahead of DRDO.

In Feb 2020, ISRO stated that they intend to test their scramjet at Mach 6-7 at 25 km height, expect a flight test in 1-2 years. If that test succeeds then ISRO can start working towards that 300+ sec burn time. DRDO will no doubt take longer to get there. Even if ISRO were to hand over their engine to DRDO, don't expect a fully ready hypersonic cruise missile to be ready in less than 5 years.

Also when you calculate the range of a scramjet powered cruise missile consider the fact that the engine can't work unless the air rushing through the intake is supersonic. So you need a solid booster to get you to that supersonic speed. That booster will push the missile to a significant distance before the missile goes supersonic & the booster can detach. Add that range to your calculation and you will see that a scramjet engine capable of 300 sec burn can easily get to 800 km+ distance.

Do we know the range of the 2 hypersonic cruise missiles DRDO is working on ?
As per p kicker dfi,range is 1000 km +
 

SavageKing456

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Based off hstdv
There are two hcm underdevelopment
Screenshot_20211204-113726_Drive.jpg

There is a vishnu hcm underdevelopment which I guess is ground launched
So vishnu:-Ground launched hcm powered by scramjet.
And another is air launched based on waverider config which will be powered by dual combustion ramjet engine.
HCM will be mounted on top of a solid booster and boosted to desired Mach number. In the cruise phase, the vehicle will be propelled by long duration hydrocarbon fuelled scramjet engine to the desired destination. In the descent phase, the scramjet will be switched off and the vehicle will be decelerated to Mach 2 which result in a high energy impact. Waverider concept is utilized to evolve the cruise vehicle aerodynamics and vehicle integrated scramjet combustor has been designed. Coupled external-internal CFD calculations (involving nonreacting flow in vehicle forebody and reacting CFD in scramjet combustor) were performed to estimate aero-propulsive parameters of the vehicle. High fidelity design were carried out for thermal management of both external aerodynamic heating and exothermic reaction due to kerosene-air burning in scramjet combustor. Niobium alloy with silicide coatings, C-SiC composites, Inconel, Nimonic alloys and titanium are considered the candidate materials for combustor and air frames. The Dual Combustion Ramjet (DCR) concept which combines the advantage of both ramjet and scramjet propulsion system is considered for air launched option. DCR enhances the HCM’s air-breathing mode operation and thereby reducing the overall system weight and makes the vehicle capable of air launch. The fuel is added in a small dump-type subsonic combustor, which acts as a fuel-rich gas generator. The hot fuel-rich exhaust is injected into the supersonic combustor and made to undergo the secondary combustion with incoming air through inlet.


+We are also working on hypersonic glide vehicles(HGVs)
There was a tender issued by drdl for ground test hardware
PicsArt_12-12-12.35.17.jpg
 

Gessler

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This is a interesting thread. I guess India is also working on Ramjet.

Scramjet.

Ramjets were already produced & in use on many platforms like Akash SAM and BrahMos. New generation Ramjets are in development in programs like SFDR (solid-fuel ducted ramjet) for applications on lighter, smaller missiles like BVRAAMs. These are currently in testing:

Solid_Fuel_Ducted_Ramjet_SFDR_2.jpg


Scramjets are a whole other separate development for sustained Hypersonic applications (Mach 5+). These programs like HSTDV are also in development, first tests were conducted in 2016 (or before, can't recall) and the programs are continuing. Latest updates I have is that the tech-demo has matured & development of proper weapon system that uses the demonstrated techs in now underway.

In parallel there are other Scramjet projects in the country, one pursued by the space agency ISRO and one in collaboration with Russia for the BrahMos-2K. The latter will likely be similar to Tsirkon.
 

Nilgiri

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This is a interesting thread. I guess India is also working on Ramjet.

Yeah you can find ramjets in the cruise missile thread (brahmos) and also general missile thread (that gessler mentions with SFDR, akash etc)

This thread involves scramjets and hypersonics only given nothing has been deployed, its work in progress and so quite interesting to follow separately.
 

Nilgiri

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Is this guy working in one of the DRDO labs or have close contacts with some employee? I've seen him tweeting about a lot of technical stuff under development

I believe they are a networked bunch of fellas ("defence enthusiasts" they call themselves)....that search + compile stuff at http://fullafterburner.weebly.com/

A few of them might be in DRDO et al. itself....but I am unsure, and certainly not required to be given the archives around.

I would imagine they use open source resources like the following:

...And give a few tidbits+screencaps on twitter and so on is my understanding after search and sift etc.

Or tracking down such visuals + synopsis from further papers (residing in other archives) given in the references.

Well designed searches on google also give good results.

This guy/group for some reason dont give direct reference to where their diagrams+pics are from...I guess its not required on twitter TOS.

Piecing through and giving context and insight to specific details is whole different matter though, needing some intersection of degree of applied knowledge + background in the (precise) field and the spare time to muse, prepare and explain to others (who also need interest and some know-how to receive).

This last part is something I hope to do over time here on this forum....time is currently quite sparse for it on my end though.

@Paro @Gessler @Anmdt @Rajaraja Chola @Yasar @Saithan @MisterLike @T-123456 et al.
 

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