Kaveri & Aero-Engine: News & Discussion

[Rakesh]

https://x.com/shreedharsingh9/status/18 ... 1106696339 ---> GTRE is working on improving the thrust-to-weight ratio of the Kaveri engine. Now the T/W ratio is 6.5, it should be 8. To improve the power-to-weight ratio the internal temperature of the turbine must be high. GTRE is working with DRML to develop a single crystal casting to improve the turbine internal temperature. For reducing the weight, we are using bladed disc. Its usuage will reduce the weight by 25%. On the turbine side, we're going to use a boltless blade arrangement to save weight.

https://x.com/shreedharsingh9/status/18 ... 2060214375 ---> Powder Metallurgy Discs: GTRE is working with DMRL to develop Powder Metallurgy Discs, for this we require 50,000 tonne forging press.

[Ashokk]

INDIAN Startup Making JET ENGINES : Success, Struggles, Big Dreams | DG Propulsion

[drnayar]

Scaling up and the high temperature core metallurgy are the issues keeping within the weight limitations.

[Rakesh]

When we talk about cancelling MRFA in favour of hundreds of Tejas, please remember the below. This is why our own turbofan is so important.

The MRFA would not exist if India had her own turbofan. But the decision are hell bent on not properly funding the Kaveri program.

The U.S. Tries to Axe the Gripen-E Fighter Sale to Colombia
https://turdef.com/article/the-u-s-trie ... o-colombia
25 Feb 2025

Infodefensa reported that the U.S. authorities have shown intentions to prevent Colombia’s acquisition of Gripen fighter jets so that Colombia will move towards the F-16 option.

[Rakesh]

https://x.com/livefist/status/1894294740130209833 ---> With nearly $15 billion in Rafale orders to France, India has had more than enough leverage to force France to either share jet engine tech or set up a JV in India — time to cut the bullshit and ask why that didn’t happen?

https://x.com/FinestYew/status/1894356059432550539 ---> Jet engine technology is effectively national sovereignty. No one is going to hand it over. If that was the case, the gulf countries would have been military superpowers by now.

Why Didn’t India Force France To Share Engine Tech?
https://www.livefistdefence.com/why-did ... gine-tech/
25 Feb 2025

[Rakesh]

https://x.com/livefist/status/1894690111037813049 --->

• Egregious neglect
• Zero oversight
• Zero vision
• Failed project management
• Misplaced optimism

In 2019, Admiral Arun Prakash (retd) wrote the most scathing, prescriptive column for @ReviewVayu on India's Kaveri engine program. Timely today:

Flying Blind? Urgent Need to Revive India’s Aero-Engine Dreams
https://www.livefistdefence.com/flying- ... ne-dreams/
26 Feb 2025

This article first appeared in the April 2019 issue of Vayu Aerospace & Defence Review and used here with permission from the publisher. Livefist has decided to re-publish this column in the context of the current flashpoint over U.S. jet engines delaying India’s Tejas Mk1A fighter jet deliveries.

[maitya]

https://x.com/shreedharsingh9/status/18 ... 1106696339 ---> GTRE is working on improving the thrust-to-weight ratio of the Kaveri engine. Now the T/W ratio is 6.5, it should be 8. To improve the power-to-weight ratio the internal temperature of the turbine must be high. GTRE is working with DRML to develop a single crystal casting to improve the turbine internal temperature. For reducing the weight, we are using bladed disc. Its usuage will reduce the weight by 25%. On the turbine side, we're going to use a boltless blade arrangement to save weight.

https://x.com/shreedharsingh9/status/18 ... 2060214375 ---> Powder Metallurgy Discs: GTRE is working with DMRL to develop Powder Metallurgy Discs, for this we require 50,000 tonne forging press.

All valid points but another exhibition of severe lack of informed counter-questioning (when such information is being made available to them by GTRE et all) viz.

Wrt SC Casted Turbine Blades and Vanes:
1) DMRL has been exhibiting SC TF turbine blades and vanes from early 2000s - IIRC 2005-6, can't recall the exact timelines. So what's new now?

2) Similarly, indigenous DMS4 (4th Gen SC grade) material has been available for >1.5 decades now - why have we not progressed wrt processing them blade (and vane) manufacturing level. Are we instead, looking at commercially available 2nd Gen SC grade material from CM (e.g. CMSX4)?

3) Have we mastered Alumina based Ceramic shell moulds (over a wax pattern) for blade/vane at mass-manufacturing level? More so, since we have already implemented the same for a casting temp capability of 1550 deg C (but using DS CM247LC superalloy) - and since, SC casting-temp for CMSX4 are typically at 1540-1560deg C.

4) CMSX4 is already used for SC turbine blades and vanes in HTSE - so, then, SC casting tech for CMSX4 should be already available inhouse? Or is the internal cooling-path architecture so drastically different from the HTSE blades/vanes, that whole new casting tech needs redeveloping?

5) What's the plan for TBC? Assuming we already have implemented 8-YSZ based TBC for DS-Casted Kaveri Turbine blades, are we aiming for anything different (like bilayer TBCs, like LZ-YSZ being tested for A/B flaps)?
Have we developed mass-manufacturing tech for EBPVD application (for TBC), as opposed to lab-level capabilities (in IREL)?

6) Given that we have already implemented Laser-Drilled film-cooling architecture for the Kaveri Turbine blades, is it safe to assume we have the required technology for implementing the same for SC-casted turbine blades and vanes?

7) Are we looking at any brand-new initiative like developing SLS/DMLS technology for intermetallic Gamma-TiAl (or Gamma-TiAl-Nb) usage for LPT blades and vanes (and maybe even the last HPC stage blades)?

Wrt Blisks:
1) Our Fan in particular, and also somewhat for the HPC stages, the RPM levels are lesser compared to F404 or other 4th Gen TFs. By roughly what %, if at all, are we looking at enhancing the Fan/LPC and HPC RPM levels, by using BLisk technology (and thus making these stages lighter)?
What is the OPR improvement we are aiming at (by enhancing the stage PRs), from the current 21-22 levels?
Or is it that blisk-usage is exclusively form the overall weight-reduction perspective, and the LPC/HPC RPM levels (and thus the PR levels) are to be maintained at the current levels?

2) Presumably we won't need the distortion-tolerant Fan for std K9 TFs, so are we looking a brand new Fan design (3D stacked design) of 4.5 PR levels? If yes, how much are we aiming at enhancing the dry-thrust levels purely from the bypass component (aka LPT-LPC aspects)?

3) By using lighter blisk technology, are we aiming at improving the polytropic efficiency levels of the HPC stages? If yes, by roughly how much?
Any initiative wrt laser-shock-peening tech for improving the surface smoothness levels of the HPC stages, thus minimising secondary losses?


Wrt overall weight reduction strategies:
1) We are aware of the successful PMC usage wrt the bypass duct - similarly, are we looking at using CMCs for static parts like Shrouds, Casings etc
Any thinking towards PMC Fans?
etc etc.
==================================================================================================
Have typed up the above, hoping-against-hope, that some of these folks with some contacts within GTRE/DRDO mgmt levels, can copy-paste these questions and seek some open-source/publicly-releasable relevant info wrt them.
However, given the level of knaawlidge publicly paraded by most of these folks, I wouldn't be holding my breath wrt them developing wherewithal to even copy-paste these questions, and sending them etc.

[csaurabh]

https://x.com/shreedharsingh9/status/18 ... 1106696339 ---> GTRE is working on improving the thrust-to-weight ratio of the Kaveri engine. Now the T/W ratio is 6.5, it should be 8. To improve the power-to-weight ratio the internal temperature of the turbine must be high. GTRE is working with DRML to develop a single crystal casting to improve the turbine internal temperature. For reducing the weight, we are using bladed disc. Its usuage will reduce the weight by 25%. On the turbine side, we're going to use a boltless blade arrangement to save weight.

https://x.com/shreedharsingh9/status/18 ... 2060214375 ---> Powder Metallurgy Discs: GTRE is working with DMRL to develop Powder Metallurgy Discs, for this we require 50,000 tonne forging press.

The thing about the thrust to weight ratio makes NO sense to me.
Lets say that the thrust is 80 kN, then at T/W ratio of 6.5 the weight is 1230 kg and at T/W ratio of 8 the weight is 1000 kg. A difference of 230 kg.
Meanwhile, the Tejas can carry a payload of 4000 kg.

Just think about the difference between having a fully operationalized indigenous engine (T/W ratio be damned) and having 5% decrease in payload with imported foreign engine..
Should be no contest really. Except if the generals are import bahadurs.

[ernest]

Just think about the difference between having a fully operationalized indigenous engine (T/W ratio be damned) and having 5% decrease in payload with imported foreign engine..

I have been trying to rationalize this as well, and came to similar conclusions that you did. However, to add some more nuance. A heavier engine will have cascading effects on structural members' strength and weight. I do not have the expertise to quantify that. But I still think, that could be traded off with some payload capacity and range. Overall, still think that a heavier desi engine is good enough if it delivers on other absolute parameters like thrust, fuel consumption, reliability, etc. Still a good replacement for Mig-21/27/jags

[fanne]

My take on T/W. I have asked these questions few time. Hopefully Maitya sir or someone will answer.
T/W ratio is not really impacting overall weight as such. As you point out, LCA carries 4000 kg of weight. It can easily sacrifice 230 kg, If that means it can carry an indigenous engine. Anyway, whatever config you try, LCA is left with few 100kg of weight not taken.
The T/W more or less dictates how efficient is the engine. The exhaust through the turbine has to rotate the whole engine (the moving/rotating part that is). All else being same, a lighter engine means that for lesser work, the turbine can rotate the engine more faster (resulting in better mass flow and better burning) or if they keep the RPM same (refer to M post above), because higher RPM may mean more burn, higher TeT that may not be acceptable, they can do so by burning less fuel (as the rotational mass is less).

[pravula]

https://x.com/livefist/status/1894294740130209833 ---> With nearly $15 billion in Rafale orders to France, India has had more than enough leverage to force France to either share jet engine tech or set up a JV in India — time to cut the bullshit and ask why that didn’t happen?

https://x.com/FinestYew/status/1894356059432550539 ---> Jet engine technology is effectively national sovereignty. No one is going to hand it over. If that was the case, the gulf countries would have been military superpowers by now.

Why Didn’t India Force France To Share Engine Tech?
https://www.livefistdefence.com/why-did ... gine-tech/
25 Feb 2025

Nonsense. How many billions of $$$ has India spent with Airbus and Boeing again? How much of CFM56 tech is made in India? Heck, the new Air India orders alone had 570 aircrafts, so a minimum of 1040 engines!!!

[Neela]

https://x.com/shreedharsingh9/status/18 ... 1106696339 ---> GTRE is working on improving the thrust-to-weight ratio of the Kaveri engine. Now the T/W ratio is 6.5, it should be 8. To improve the power-to-weight ratio the internal temperature of the turbine must be high. GTRE is working with DRML to develop a single crystal casting to improve the turbine internal temperature. For reducing the weight, we are using bladed disc. Its usuage will reduce the weight by 25%. On the turbine side, we're going to use a boltless blade arrangement to save weight.

https://x.com/shreedharsingh9/status/18 ... 2060214375 ---> Powder Metallurgy Discs: GTRE is working with DMRL to develop Powder Metallurgy Discs, for this we require 50,000 tonne forging press.

The thing about the thrust to weight ratio makes NO sense to me.
Lets say that the thrust is 80 kN, then at T/W ratio of 6.5 the weight is 1230 kg and at T/W ratio of 8 the weight is 1000 kg. A difference of 230 kg.
Meanwhile, the Tejas can carry a payload of 4000 kg.

Just think about the difference between having a fully operationalized indigenous engine (T/W ratio be damned) and having 5% decrease in payload with imported foreign engine..
Should be no contest really. Except if the generals are import bahadurs.

Standard cycle used in every industry.
Incremental development => test => sell, deploy & have no red numbers in balance sheet => get field experience => debug => iterate => incremental development => next generation . The cycle continues.
From 3rd or 4th gen, you start making variants as confidence grows. ( e.g. our missile platforms just exploded in last 10 years)

But, not wise to oversee typical stakeholder interests
1. R&D wants funding ,development with achievable targets.
2. Production agencies want customers before putting up money for jigs, long term viability of investment, sell wares and keep P&L in black.
3. Babus look at overall progress of programs and watch P&L.
4. Forces ,ideally, deploy platforms with capabilities, incrementally improve and expand the scope of same.

If any of the above interests has deviations in their approach (e.g forces asking for X´5th gen performance right at start, ), the whole project falls apart.
this is true for commercial business . this is true to a great extent , for military too. There is , generally, subventions and special assistances for military R&D, military acquisitions, as tech denial is an issue. For large countries, tech denial s hard reality as no foreign producer wants to lose a large market . So ToT , will never ever happen until enough RoI is made and they have moved to next gen.
India has no choice but to invest continously and hold ground. From all the chaos b/w 2000-2015 and the naysayers shaking their heads, Tejas came through and very reasonable numbers are being produced and reached stage 4.. For Kaveri, we are at stage 1.

[maitya]

...
T/W ratio is not really impacting overall weight as such.
...
The T/W more or less dictates how efficient is the engine.
...

I think, this is 400% correct ... T/W ratio is nothing but one (of the many) measure of efficiency of the TF - and provides probably the closest understanding about the technological superiority of different TFs irrespective of their form-factor.
And is thus most widely used as a lay-man method to categorize between various Gens of TFs.

To expand it a bit, just as an example, the AL-31F series with lesser dry T/W ratio than, say a M88-2, will mean AL-31F is an "technologically inferior" design compared to these 4+ Gen TF (but is superior to, say, Adour Mk871 etc).
The flip side of course is, had AL-31FPs been "theoretically" technologically upgraded to produce 85KN dry thrust (12% increment, almost the AL-41F1 level), without increasing the weight, then it could have claimed the same 4+ gen TF level TWR.

But all these doesn't make the Su-30 series (with AL-31FP) a slouch compared to Rafale or Eurofighter - as these platforms were designed with a certain TF capability in mind etc.

So corollary is, Kaveri (K9) should have produced 54KN dry and also reduce weight by ~150Kg to have reached the same 4+Gen TF level TWR.
Similarly, going by the same AL-31FP/Su-30 analogy above, the current 51KN (dry)/1150Kg K9 could have been adequate for powering the Mk1/Mk1As.
But the program was quite haughtily abandoned approx 1.5 decades back, on the first hint of Wet thrust shortfall (by about 15%) - so GTRE et all, never got a chance (wrt K9), that Saturn (and the WS-10 in China) got, to incrementally upgrade the AL-31F to AL-41F1 levels.

Question is, hypothetically, what would have happened if 50% of the 2 sqns of Mk1s, were powered by K9 series over the last ~decade?
And today, when they were being finally forward-deployed, if K9s were not able to reach the wet thrust levels, how difficult would it have been to swap them with F404s (which were already ordered and were available during the MK1 deliveries, anyway)? Hain jee ...

Instead, see how cleverly the current-delay in deliveries of Mk1As are pinned on HAL - would that be the same scenario had the Kaveri program continued with inductions and follow-on dev initiatives.
After all, Atmanirbharata doesn't come about via sheer-pathological-contempt towards indigenous tech dev programs, as exhibited by IAF and MoD - it's one thing to publicly lament about lack-of-magic-wands etc*, it's quite another to appreciate and nurture ab-initio programs, towards strategic independence, in the long term.

PS: You may have noticed, in any of the examples above, I haven't used Wet TWR - pls refer to my prev post, as to why it's utterly fallacious to do so. Or maybe I'll write a detailed post someday wrt this.
==================================================================================================
* And also secretly covet furrin-maal (as advertised in their technicolour brochures) - sorry how does the actual thrust levels achieved by these imported TFs, during April-Aug in our desi airfields (or say from Leh and other high alt airfields, all year around), compare to what K9 would have produced in these same situations.
Never will these details come out/published, as that would be akin to letting the proverbial cat out of the bag.

[drnayar]

https://x.com/livefist/status/1894294740130209833 ---> With nearly $15 billion in Rafale orders to France, India has had more than enough leverage to force France to either share jet engine tech or set up a JV in India — time to cut the bullshit and ask why that didn’t happen?

https://x.com/FinestYew/status/1894356059432550539 ---> Jet engine technology is effectively national sovereignty. No one is going to hand it over. If that was the case, the gulf countries would have been military superpowers by now.

Why Didn’t India Force France To Share Engine Tech?
https://www.livefistdefence.com/why-did ... gine-tech/
25 Feb 2025

Nonsense. How many billions of $$$ has India spent with Airbus and Boeing again? How much of CFM56 tech is made in India? Heck, the new Air India orders alone had 570 aircrafts, so a minimum of 1040 engines!!!

This is interesting but has an analogy elsewhere. Naval Group of France is on record complaining HDW is creating competitors by significant submarine technology transfers.
Now Naval Group or by extension, France will never enable creation of a competitor by technology transfer.

[srai]

^^^
Listening to Aero India interview of GTRE director, he expects foreigners to share the know-hows and know-whys

[pravula]

Nonsense. How many billions of $$$ has India spent with Airbus and Boeing again? How much of CFM56 tech is made in India? Heck, the new Air India orders alone had 570 aircrafts, so a minimum of 1040 engines!!!

This is interesting but has an analogy elsewhere. Naval Group of France is on record complaining HDW is creating competitors by significant submarine technology transfers.
Now Naval Group or by extension, France will never enable creation of a competitor by technology transfer.

But CFM56 is old tech, the new push is for LEAP56 engines...

[csaurabh]

My take on T/W. I have asked these questions few time. Hopefully Maitya sir or someone will answer.
T/W ratio is not really impacting overall weight as such. As you point out, LCA carries 4000 kg of weight. It can easily sacrifice 230 kg, If that means it can carry an indigenous engine. Anyway, whatever config you try, LCA is left with few 100kg of weight not taken.
The T/W more or less dictates how efficient is the engine. The exhaust through the turbine has to rotate the whole engine (the moving/rotating part that is). All else being same, a lighter engine means that for lesser work, the turbine can rotate the engine more faster (resulting in better mass flow and better burning) or if they keep the RPM same (refer to M post above), because higher RPM may mean more burn, higher TeT that may not be acceptable, they can do so by burning less fuel (as the rotational mass is less).

Does it really matter that much ? What is the specific fuel consumption of Kaveri w.r.t GE 414 ? Just carry some more fuel then, reduce the payload a bit more. It's not an unworkable problem.

let met put it this way, does anyone know what the T/W ratio of ISRO rocket engines are and do they compare with the advanced engines of the west (probably not) ? Why is no one bothered by it? Because we see the value of having an indigenous space launch vehicle, not the 'most efficient' one.

[Manish_P]

...
Does it really matter that much ? What is the specific fuel consumption of Kaveri w.r.t GE 414 ? Just carry some more fuel then, reduce the payload a bit more. It's not an unworkable problem.

let met put it this way, does anyone know what the T/W ratio of ISRO rocket engines are and do they compare with the advanced engines of the west (probably not) ?
...

Strangely enough I had the same argument with a fauji kid a few years ago when the kaveri engine was a hot topic... His answer 'an ISRO rocket is not carrying a pilot and not fighting a kill-or-be-killed duel with another rocket'

I said fair enough but can he guarantee that the fighter we buy will always come up against a fighter with equal or worse performance during it's entire lifetime of a few decades...

No answer

[fanne]

Maitya sir, another related question related to kaveri. Dry Kaveri works fine. It achieved it design goal. The dry thrust is very similar to f 404 in 20. The afterburner is mostly fuel injectors and the thermal lining. If I were to put a %, 90% of the tech is till the dry engine working. The wet part is usually 50% to 70% of the dry thrust. F404 is 48.9 kn thrust dry (compared to 52 kn of Kaveri), but after burning is 60% of it while we are struggling to get even 50% of dry thrust as wet thrust. There are no moving part in afterburner, temperature may or may not be as high as turbine inlet. What is the catch/ issue/ hold up there.

[V_Raman]

Is dry thrust the engine core and the crown jewel? if yes, why is it so hard to get ToT for wet thrust?

[Brad Goodman]

. What is the catch/ issue/ hold up there.

I have the same question, Always thought dry thrust was the challenge but looks like after burner is the new challenge we cannot find answer to

[fanne]

....

Thanks!!
Maitya sir, another related question related to kaveri. Dry Kaveri works fine. It achieved it design goal. The dry thrust is very similar to f 404 in 20. The afterburner is mostly fuel injectors and the thermal lining. If I were to put a %, 90% of the tech is till the dry engine working. The wet part is usually 50% to 70% of the dry thrust. F404 is 48.9 kn thrust dry (compared to 52 kn of Kaveri), but after burning is 60% of it while we are struggling to get even 50% of dry thrust as wet thrust. There are no moving part in afterburner, temperature may or may not be as high as turbine inlet. What is the catch/ issue/ hold up there.

[maitya]

....

Thanks!!
Maitya sir, another related question related to kaveri. Dry Kaveri works fine. It achieved it design goal. The dry thrust is very similar to f 404 in 20. The afterburner is mostly fuel injectors and the thermal lining. If I were to put a %, 90% of the tech is till the dry engine working. The wet part is usually 50% to 70% of the dry thrust. F404 is 48.9 kn thrust dry (compared to 52 kn of Kaveri), but after burning is 60% of it while we are struggling to get even 50% of dry thrust as wet thrust. There are no moving part in afterburner, temperature may or may not be as high as turbine inlet. What is the catch/ issue/ hold up there.

Right, Afterburner should have been relatively easier than the TF core - however the expectation/specification is over the top - it's 60% thrust augmentation but with a mass-factor of 1.1.
Most TFs aim for 50%, which is what K9 also achieved - but 60% up-thrusting is where M88-2/EJ200/F414 levels, so again 4+ gen actually.

Do note here 45-50% upthrusting is turbojet territory, and Turbofans are expected to produce higher % of upthrusting.
As in a TF, the bypass air can be mixed with the after-turbine-gas-flow, and thus reducing its Oxygen "deficiency" levels (caused by the prev combustion cycle in the Combustor for the same gas flow mass).
Plus such mixing of the cooler bypass flow, results in lower gas inlet (to the A/B) temp, resulting in higher differential temp at the exhaust, resulting in higher upthrusting levels.
etc etc.

Anyway, there are multiple issues - but the trickiest is hot temp handling capability of the jet-pipe, flame-holders and fuel injectors. Do note the gas temp levels falls to low (by TF std that is) 600-700 deg C post the LPT stage - and you are essentially seeking to ramp-it up to atleast double of that in the A/B - so around 1500+ deg C.
Just for the heck of it, note doubling the temp levels from 700 to 1500 deg C will upthrust it by mere 36%, which is way lower than 60% that is being sought for - but even such calc doesn't work in real world, as those are for a perfectly efficient system.

Anyway such temp increment is via injecting more and more fuel - but here again there's a limit. Beyond 2.2 temp ratio (ratio of inlet and outlet temp in a jetpipe), the corresponding thrust increment ceases to be linear.

Other issue is velocity of the gas existing the turbines (typically at 300-400m/sec), and is thus very difficult to maintain stable combustion (fuel injection would be around 2-3m/sec levels). To mitigate this diffusers and also the V-Gutter (Vapor gutter) are used (to reduce velocity).
This itself needs careful designing, lest phenomenon like screech etc becomes an issue.

Also one needs to carefully "manage" the stagnation pressure build-up in the jet-pipe, so that any backflow to the core can be prevented (such backflows will cause compressor stall and fan surges).

Net net, there are some critical material (e.g. liner cooling, Thin-wall Metal-Ceramic liners etc) and also thermodynamic tech issues involved, if anything more than 40-45% upthrusting is required.
But then again, and as you've rightly pointed out, these challenges, though quite steep, are still not in the league of those faced in the core of a TF etc.

[Rakesh]

https://x.com/ShiroBarks/status/1897543773254459403 ---> Just gonna leave this here.

[Prasad]

Right, Afterburner should have been relatively easier than the TF core - however the expectation/specification is over the top - it's 60% thrust augmentation but with a mass-factor of 1.1.
Most TFs aim for 50%, which is what K9 also achieved - but 60% up-thrusting is where M88-2/EJ200/F414 levels, so again 4+ gen actually.

How much impact does lacking a full scale a/b test facility have on developing one

[arvin]

While rest of India plans chalo Goa as part of vacation, folks in GTRE will plan for chalo Gromov to have a nice time.

[srai]

https://x.com/ShiroBarks/status/1897543773254459403 ---> Just gonna leave this here.

10-years in power-> $20 billion imports
5-more years -> another $16 billion import lined up

[fanne]

Thanks!!

Right, Afterburner should have been relatively easier than the TF core - however the expectation/specification is over the top - it's 60% thrust augmentation but with a mass-factor of 1.1.
Most TFs aim for 50%, which is what K9 also achieved - but 60% up-thrusting is where M88-2/EJ200/F414 levels, so again 4+ gen actually.

..
Net net, there are some critical material (e.g. liner cooling, Thin-wall Metal-Ceramic liners etc) and also thermodynamic tech issues involved, if anything more than 40-45% upthrusting is required.
But then again, and as you've rightly pointed out, these challenges, though quite steep, are still not in the league of those faced in the core of a TF etc.

Thanks for the kind reply. So it looks like we have hit almost the max level possible with Kaveri as far as AB is concerned. Not to say that it cannot be further improved, but it comes with a decent leap in tech, an even then the gains may not be commensurate with the effort. This goes back to the design of Kaveri itself, where very less air is bypassed(16%) and that effects the AB (from providing less cooling - less temperature differential after AB hence less gain and less unburned oxygen).

We must have gone with good intent with Kaveri design (flat rating), and given our tech maturity in materials mainly, we are stuck where we are. The Kaveri consumes 78 kg/s of air, compared to 77.1 kg of f414 and 66.2 kg/s of f 404. And it has very low bp compared to these engine, yet it dry thrust is 8-9% more than f404 and 10% less than f414. It is in fact a F414 sized engine (not exactly width and length wise, only from mass flow pov, that is the one that counts), producing 10% less than F414 and 10% more than f404 (in dry thrust). Given its design, I dont think AB gains are going to be substantial, but any improvement in material, might see dry thrust moving from 52KN towards 57KN (or more, as more air is flowing through the core).
Given that planes work 90% on dry thrust, I dont know why do we say that LCAMK1a cannot take Kaveri now. If you look at many advanced planes (like Rafale, F-22), They have very very modest AB thrust. If a fully combat loaded (not theoretical) LCAMK1a can take off on Kaveri AB, and it can fly from LEH, it should be used.
Also, maybe we can use F414 with current MK1 and MK1/A. The airflow is for that.

[maitya]

...
Right, Afterburner should have been relatively easier than the TF core - however the expectation/specification is over the top - it's 60% thrust augmentation but with a mass-factor of 1.1.
Most TFs aim for 50%, which is what K9 also achieved - but 60% up-thrusting is where M88-2/EJ200/F414 levels, so again 4+ gen actually.
...
Net net, there are some critical material (e.g. liner cooling, Thin-wall Metal-Ceramic liners etc) and also thermodynamic tech issues involved, if anything more than 40-45% upthrusting is required.
But then again, and as you've rightly pointed out, these challenges, though quite steep, are still not in the league of those faced in the core of a TF etc.

Thanks for the kind reply. So it looks like we have hit almost the max level possible with Kaveri as far as AB is concerned. Not to say that it cannot be further improved, but it comes with a decent leap in tech, an even then the gains may not be commensurate with the effort. This goes back to the design of Kaveri itself, where very less air is bypassed(16%) and that effects the AB (from providing less cooling - less temperature differential after AB hence less gain and less unburned oxygen).
....

I'll try to keep this post short, however do note that 1.6 time upthrusting requirement for the A/B, is an appropriate one and should have been doable - there're quite a few technical challenges that needs addressing though, but those should have been /still is within GTRE's reach.
For a 0.16 BPR design, would mean still there are enough bypassing cool air to reduce the Jetpipe entry temp (and the depleted Oxygen levels etc), as remember, not the entire bypassed air is diverted for this purpose anyway.
The challenges are more in the realm of materials (jet-pipe heat shield) and wrt Flame stabilizer (V gutters alongwith fuel injection) system design - plus of course the variable area nozzle design itself.
Again, as said before, complex yes, but nothing unachievable or anything.

I think abrupt program cancellation, sometime in 2010-2012, paid put to those initiatives (K10 program, with aim to reduce weight and catch-up on wet thrust). Maybe the recently reported initiative of asking Brahmos Aerospace to develop the A/B section is a step in that direction (for any org working extensively on ramjet propulsion etc, this should be bread-butter stuff) - we'll see!!

===================================================================================
However, I get a feeling that, amidst all these milieu, we continue to get confused wrt what is being stated by GTRE et all wrt future of the Kaveri program etc, vis-a-vis what the current state of the Kaveri program is.

My reading (and can be completely wrong as well) is there's a 3-step strategy being followed:

1) Get KDE (with an aim of ~50KN dry thrust) certified fully

2) In parallel, get some K9 improvements done (drawing from the KDE program), so that a fully certified 51KN/81KN 4-gen TF (let's call it K9*) can be demonstrated. This is where Godrej (wrt KDE) and Brahmos Aerospace (for the A/B section) related recent news etc, comes in.
However, I doubt, in this initiative, they will be able to get the K9* weight to sub-1Ton levels (and may have to settle for something like ~1130Kg). Remember, there was a recent news (read it somewhere) that KDE is in the realm of 950Kg weight - adding 10% for the A/B weight (mass fraction of 1.1) takes it to 1045Kg level, which in itself is a fantastic achievement, but still not in the sub 1Ton category (the original design intent).

3) This is the so-called 90KN 4th Gen TF initiative comes in.
Now, to achieve 90KN wet-thrust levels, will mean achieving ~56KN dry thrust level (just as a comparo, F414's dry thrust levels are in ~58.5KN level), which is like ~10% dry-thrust increment.
Worse, if the flat-rating requirement would have to be carried forward, then it's more like trying to design a 59-60KN dry thrust 4th Gen TF level perf parameters (like TeT, OPR, SFCs etc), figuratively speaking - which is a whopping 14-15% increment.
Even worse, all of these while trying to loose 10% of K9* weight levels.

If you may have noticed there're multiple global 4th Gen TF programs, where such 10% dry thrust level increments has been achieved without touching the Core (or trying to touch at the periphery of the core), and mostly via improvements to the LPT/Fan/LPC aspects.
Difficulty with the current Kaveri's ultra-low-BPR design is, such initiatives wouldn't be able to deliver similar level of dry-thrust increments (via the LPT/Fan/LPC route tinkering) - though it would certainly be able to still deliver a good dry-thrust improvement levels (my guesstimate would be around 7-8% max).
So to drive such a 14-15% dry thrust improvements, the entire core has to be redesigned with moderately higher TeT/OPR (say, something like 1500+ deg C TeT, 28+ OPR) etc, without changing the dimensional aspects of the TF - aka a full-blown true/blue 4++ Gen TF program, requiring dedicated funding and support (and will require HATF and FTB as well).
Very very similar to the F404 -> F414-402 "evolution" program, and will be a pretty steep challenge - we'll see, but I've written extensively on this aspect, pls refer to them for further details (if you want, that is).

[fanne]

Thanks..
If I am reading the tea leaves correctly (and I sincerely want to be wrong), we will be denied f404/f414 (if not outright, through fables of supply chain constraint) unless we buy F-35 AND abandon russian tech altogether.
I know it is a very extreme scenario, most MUTU will swear will never happen, but more likely, and perhaps because of Trump. We may here, you are either with us or against us (not because Trump wants it, us wanted that forever, and they see Trump is the one that can most likely implement it, bring India in US orbit- and always remember what wise kissinger once said, to be American enemy is ....)

I believe, if US tech is cut off, French are unwilling (that's the reason, even after 7-8 years of continuous negotiation, we still don't have engine tot tech from them, they are reluctant), UK will follow US lead. That leaves russia where the tech is inferior to the west and derided heavily in BR, India and within services and politicians (when we can ourselves cannot produce what they did 50 years ago, talk about being haughty)

While we doubledown on Kaveri, its derivative, we are at least 10 or 20 years away from a working/certified engine. It's good to have our design, that is the only way forward, but being obstinate towards only our design is not helpful. Not that our designs have been spectacular, Khukari was sunk because our sonar was not up to par and needed compromises. Our own designed IJT (HTT -36) was supposed to be ready in few years in 2003, is still being corrected for its design deficiencies in 2025. The point is not that we should not design, but our design is not sacrosanct, it will not work in the first go, or in multiple trials (just like everybody else). In the meantime can we not have a middle way?

The Russian RDMK33 is a good design (meaning it does not have flutter issues like Kaveri and is in production). It has its own challenges. But kudos to russians, they designed it around their tech capabilities. With Lower Tet, more HPC compressor stages (9, compared to 7 of f 404 and 6 of kaveri), more juice from afterburner (@1.65). From what I read, our material for turbine in Kaveri is better, maybe even HPC and LPC blades ar better or of same tech, AB is not good, can we not get the ToT and indenize it. Russians were per the news willing.

This is an interim measure. We may not get f404/f414 (most likely the strategy will not be to outright reject but drip feed, make us dhobi ka kutta), we indenize this engine, (latest RD33 mk gives wet thrust of 88 KN), use it for mk1a and MK2 (I keep on hearing 98 KN version of the same engine), do the necessary changes in the engine while we perfect Kaveri. We aslo test our material in RD33 MKI. Is that even possible? Does this thought process has any merit?

[chetak]

Thanks..
If I am reading the tea leaves correctly (and I sincerely want to be wrong), we will be denied f404/f414 (if not outright, through fables of supply chain constraint) unless we buy F-35 AND abandon russian tech altogether.
I know it is a very extreme scenario, most MUTU will swear will never happen, but more likely, and perhaps because of Trump. We may here, you are either with us or against us (not because Trump wants it, us wanted that forever, and they see Trump is the one that can most likely implement it, bring India in US orbit- and always remember what wise kissinger once said, to be American enemy is ....)

I believe, if US tech is cut off, French are unwilling (that's the reason, even after 7-8 years of continuous negotiation, we still don't have engine tot tech from them, they are reluctant), UK will follow US lead. That leaves russia where the tech is inferior to the west and derided heavily in BR, India and within services and politicians (when we can ourselves cannot produce what they did 50 years ago, talk about being haughty)

While we doubledown on Kaveri, its derivative, we are at least 10 or 20 years away from a working/certified engine. It's good to have our design, that is the only way forward, but being obstinate towards only our design is not helpful. Not that our designs have been spectacular, Khukari was sunk because our sonar was not up to par and needed compromises. Our own designed IJT (HTT -36) was supposed to be ready in few years in 2003, is still being corrected for its design deficiencies in 2025. The point is not that we should not design, but our design is not sacrosanct, it will not work in the first go, or in multiple trials (just like everybody else). In the meantime can we not have a middle way?

The Russian RDMK33 is a good design (meaning it does not have flutter issues like Kaveri and is in production). It has its own challenges. But kudos to russians, they designed it around their tech capabilities. With Lower Tet, more HPC compressor stages (9, compared to 7 of f 404 and 6 of kaveri), more juice from afterburner (@1.65). From what I read, our material for turbine in Kaveri is better, maybe even HPC and LPC blades ar better or of same tech, AB is not good, can we not get the ToT and indenize it. Russians were per the news willing.

This is an interim measure. We may not get f404/f414 (most likely the strategy will not be to outright reject but drip feed, make us dhobi ka kutta), we indenize this engine, (latest RD33 mk gives wet thrust of 88 KN), use it for mk1a and MK2 (I keep on hearing 98 KN version of the same engine), do the necessary changes in the engine while we perfect Kaveri. We aslo test our material in RD33 MKI. Is that even possible? Does this thought process has any merit?

Good idea, fanne ji.


We should try to buy jet engine tech no matter from where it originates, be it russia or the west, and not wait for the impeccable offer to be made for what our dunderheads consider the perfect engine which may be the 404/414 series (current favourites, but only until newer brochures come out to fuel more wet dreams)


Buying russian will probably cause other countries to sweeten their own offers because they may relent due to the FOMO factor.


Industrial (and military) espionage may also be a very real fear that may be complicating the TOT process. We are pretty casual about such risks, while in the real world, the owners of the IP will be rightly paranoid, especially when we have so many horny heroes in key positions leaking critical weapon systems data to their paki paramours masquerading as their so called सपनो की रानीs and the ISI is quite generous in sharing the data with the cheeni


No reason for us not to invest in two jet engines with different design philosophies along with TOT (assuming that we can afford it), and just maybe it turns out to be what is needed to push our own efforts to the next level


The idea of building a reverse engineered version of the SNECMA M88 or the Saturn AL-31, Klimov RD-33 series using Indian made superalloys developed by MIDHANI et al, and maybe some imports, in case we cannot as yet make the required superalloys, should perhaps be looked at as a quick study, if not already done

We are familiar with these powerplants, we already have the required test facilities, including real time flight data from hundreds of thousands of flight hours, failure patterns, limitations, and overhaul data from the shop. This is an advantage that can be exploited by the designers. The kaveri is a very long way off from producing/providing such data

[ashishvikas]

^^

It was discussed in Episode 36 : IAH with Saurav Jha 09 March 2025 | On The IAF's Plans To Restore Its Squadron Strength

EJ200 can be an alternative to 404/414s.

[maitya]

^^

It was discussed in Episode 36 : IAH with Saurav Jha 09 March 2025 | On The IAF's Plans To Restore Its Squadron Strength

EJ200 can be an alternative to 404/414s.
...

Nope ... EJ200 (or even M88-2) can be a substitute for F404 (actually much better) but not in F414 levels - in fact, there're no other current TF that can best the 414 (as mentioned, always always look at dry T:W ratio).

Also most of the brochure specs (wrt thrust) for both M88-2, EJ200 etc etc will come unstuck quite a bit in our conditions - but since furring maal, there'll be thundering silence from the users, MoD et all.
Only F414 will provide somewhat acceptable level of perf degradation in our conditions, that all other such 4+ Gen TFs wouldn't - Kaveri, of course will have no such issues.

If F414 gets stuck, then it's bye-bye Mk2 (and also serious risk to AMCA Ph 1 as well) - as there's simply no time to develop an indigenous solution in the time-frames involved. And neither are there any suitable TFs (actually there is one, called Izdeliya-30, but no joy there) currently available, that can be optimally shoe-horned into these platforms.
For Mk1A, there are some options of course - starting from EJ200 to M88-2 or even RD-33MK etc, but except for RD-33MK, the OEMs for the other two will not share Manufacturing ToAsT (maybe, just maybe, for a few 10s of billions of $s, they may relent for fully imported units - plus of course addn charge and time to make them fit into Mk1As).

There are no easy choices ... of course, you neglect indigenous programs, these are the exact prices to be paid, in future.

[maitya]

I'm not sure who is ready to part the Tech that we want (are lacking), as those tech are either non-existent (e.g in M88-2 or EJ200 etc) or are available only in a handful of latest gen products of global OEMs (e.g. F135, Izdeliya-30 etc)
Are we alluding to that somehow these OEMs will gleefully simply handover these "differentiating" technologies of their latest products?

Only F414-EPE, could have come close to that possibility, maybe via Mfg ToAsT deal etc, but that's also not on the table.

All such technologies will have to be developed by either Snecma or Rolls Royce, via our funding - the advantage that they have of course, is the technology base of a "proven" 4+ gen TF, on which they can build upon - so maybe a shorter D&D time-frame, but that's about it, really.

Ofcourse, we will continue to naively assume that when these OEMs do develop these technologies, using our funds, they will just hand-it-over in the "true spirit of contract adherence" etc - c'mon just how much gullible can one be!!!
All the so-called "hand-over" that'll happen will be same as that is going to happen in the F414-ToAsT deal (maybe even less actually) ... until and and unless, there's a parallel 100% indigenous program trying to independently develop a 5th Gen TF (in which case only those technologies that we come close to develop, will get truly "handed over").

Oh Well ...

[sanjayc]

^^ The main problem is trying to achieve a world-beating state-of-the-art product in first attempt. They just never learn.

[Yagnasri]

We need to do funding at the required level, buy all the requirements for testing and improvements and give time but in a mission mode. As of now none of them is here. Are you surprised at the results?

[Tanaji]

^^ The main problem is trying to achieve a world-beating state-of-the-art product in first attempt. They just never learn.

Saar I would not fully blame GTRE in this. Blame the armed forces who behaved as an entitled customer who will not accept the very best and nothing else without considering the reality of domestic research. The armed forces will happily copy and paste best of breed requirements and expect you to meet them and refuse if you don’t. Even if you meet, they will do you a favour by placing token orders.

GTRE is between rock and hard place.

[A Deshmukh]

repeating again.
they need to design a UAV around the existing capability of Kaveri and produce it in small numbers.
this can be different from Ghatak (which will be advanced stealth bomber). not sure how long will Ghatak take to mature.
the new UAV can be primarily a testbed, but can be a carrier of small bombs/saaw/atgms, need not be fancy.

[vera_k]

There is this effort for a marine turbine given the war in Europe. Wouldn't have an afterburner, but if successful, it may make GTRE a viable business that can seek investment and not be bound to the government's purse strings.
India speeds up work on local marine gas turbine production

[chetak]

I'm not sure who is ready to part the Tech that we want (are lacking), as those tech are either non-existent (e.g in M88-2 or EJ200 etc) or are available only in a handful of latest gen products of global OEMs (e.g. F135, Izdeliya-30 etc)
Are we alluding to that somehow these OEMs will gleefully simply handover these "differentiating" technologies of their latest products?

Only F414-EPE, could have come close to that possibility, maybe via Mfg ToAsT deal etc, but that's also not on the table.

All such technologies will have to be developed by either Snecma or Rolls Royce, via our funding - the advantage that they have of course, is the technology base of a "proven" 4+ gen TF, on which they can build upon - so maybe a shorter D&D time-frame, but that's about it, really.

Ofcourse, we will continue to naively assume that when these OEMs do develop these technologies, using our funds, they will just hand-it-over in the "true spirit of contract adherence" etc - c'mon just how much gullible can one be!!!
All the so-called "hand-over" that'll happen will be same as that is going to happen in the F414-ToAsT deal (maybe even less actually) ... until and and unless, there's a parallel 100% indigenous program trying to independently develop a 5th Gen TF (in which case only those technologies that we come close to develop, will get truly "handed over").

Oh Well ...

maitya ji, one was suggesting that we try and buy from two different sources like one russki and the other western

that is the only way that may make it possible. The western manufacturers are mostly cross pollinated, technologically speaking

the west will not sell us two engines with TOT at the level suitable for absorption and exploitation by our guys

SAAB has successfully made afterburners in the past and may as yet retain the muscle memory for it, just saying onlee