Cryogenic rocket engine : India

[IND151]

The cryogenic engine cycles (see figure) normally used are gas generator cycle, staged combustion cycle and expander mode cycle.

Particular cycle is chosen based on consideration like engine thrust, duration, state of art available in the organization etc.

In the gas generator cycle (GG Cycle) the LOX and LH2 turbo pump are driven at two different speeds. It is done by using either a single turbine mounted on LH2 pump shaft and with gear box for reduced speed for LOX pump. Other option is two independent turbines for LOX and LH2 pumps mounted in either series mode or parallel mode. GG cycle is simple, and leads to independent development of subsystem like gas generator, turbopumps and combustion chamber. In GG Cycle the gas generator is run on
small quantity of LOX/ LH2 tapped from the pumps. In this cycle there is overall loss of Isp due to lower Isp delivered by the turbine gas.


In staged combustion cycle (SCC) the gas generator uses full LH2 flow rate and small quantity of LOX to generate the hot gas at temperature acceptable to turbines. The hot gas expands in the turbines to develop the power required for LOX/LH2 pumps and then it enters the combustion chamber where it burns with remaining LOX to develop necessary thrust. Since combustion take place in staged manner in this cycle, hence it is called staged combustion cycle. In this cycle since gas generator gas enters the main combustion chamber there is no loss of ISP. Only draw back is that sub system level development is complicated and
also pump/turbine power ratings are higher compared to GG Cycle for the same chamber pressure.

In expander cycle (EPC) the turbine drive gas, Gaseous hydrogen is tapped from the regeneratively cooled passage. The warm Gaseous hydrogen (GH2) after driving the turbine enters the combustion chamber where it burns with the oxygen to produce necessary thrust. This cycle is comparable to (SCC) as far as Isp loss is concerned. This cycle has yet another advantage
that the turbine runs on GH2 at subatmospheric temperature. However the cycle has limitations that the engine size/thrust is limited by the magnitude of the heat extraction by hydrogen from the regenerating cooling passages.

Thanks for the informative post

 

[S-DUCT]

Thanx for the excellent post, it was really very helpful n very detailed explanation in very simple language...

I'll try to summarize what i have understood so far on this topic here, plz point out any deficiencies u notice

What i have understood so far is SCC engines r the most complicated but the most efficient engines n Russia leads this tech with its RD180 n r generally used at 2nd or 1st stage to get the rocket outta Earth's atmosphere as they r highly efficient n have high weight to thrust ratio. Most countries r still trying to catch up with the Russians here. These engines r so efficient that the considerably reduce the booster requirement of the rocket.(Indian eg.- SC200)

Then comes the expander engines which r also complicated(but not as much as SCC) n here the US leads the package with its RL10 these r also efficient engines n r generally used at the upper stage to lift the satellites to its final position. These r smallest in size n have max thrust limitation(around 300kn).

The smaller size helps in reducing the over all weight of the upper payload making the rocket lighter in size(in comparision to using Gas Generator Engines in upper stage) Although these r smaller in size n have limited thrust but provide good thrust to weight ratio good enough to lift the satelittes at upper stage.

But most countries r either not able to make them small enough (RL10 vs RD56) to provide the necessary thrust at the upper stage.(Indian eg.- CE7.5)

The last one r the Gas Generator engines which r least complicated n can be easily expended to provide higher thrust at upper stage(as high as 1300kn) but r not very efficient(bcoz the Gas generated in not reused again) resulting in lower weight to thrust ratio.

But these r the most widely used engines world wide n r used by majority of the nations(Except US n Russia for upper stage). France leads it with there Vulcan Engine. (Indian eg.- CE20 n CE60).

Even though they provide high thrust but at the same time increased weight too but most countries prefer them due to their simplicity. But they have to use much bigger engines to produce the required T/W ratio(In comparision to Expander Engines).

Plz provide ur views on my understanding.

@S-DUCT i would like to hear ur comments too on my explanation...

I think every pont besides these points are excellent.
1)CE-7.5 is a very complicated SSC CE.IMO, being 1st generation of SSC CE it has a very low thrust than any SSC CE.

We can think of expander cycled CE as Tata Nano having excellent mileage and low weight,Gas generator cycled CE similar to Honda city low mileage but has medium HP and SSC CE like Ford mustang GT having very high HP.

 

[S-DUCT]

Thanx i didn't notice that i thought CE60 will be a Gas Generator Engine.

@S-DUCT
What r ur thoughts on the third engine i.e. the Nuclear powered one...

Just asking,What are your thoughts on the same.
BTW,Happy Ramnavmi!

 

[Safriz]

^^^ RD180 is efficient due to one more reason.
It uses LOX and kerosene.This fuel mixture gives more energy per mass volume than Hydrogen oxygen fuel mixture.
Another thing is that LOX and refined kerosene have same viscosity so the engine needs one pump instead of two different pumps running at different speeds.
This feature increases RD180 reliability.

 

[Yogi]

Just asking,What are your thoughts on the same.
BTW,Happy Ramnavmi!

Happy Ramnavmi to u n all other members too...

I have some reservations about it as i believe India is still not very good at minitiarizing Nuke reactors(Arihant is one example) n neither India currently has all other Infrastructure which will be required for such an amibitious project like GSLV MK3, RLV, SC200, CE60, etc. All these r still underdevelopment n that too on priority basis.

So, i believe its the nuke engine project is still in a very nascent stage but as we'll master other techs like better SSBN reactors(like Akulla) n know-how again from civilian nuke deals n development of GSLVMk3 n RLV this project will gain momentum.

Overall its a very promising project but we r still a long way to go IMO...

 

[Yogi]

@S-DUCT

Do u got any idea what kind of fuel is ISROSENE to be used in SC200...

Bluedot Can u shed some light on ISROSENE n how better it would perform in comaprision to kerosene in RD180...

 

[S-DUCT]

^^
Yeah.we should first develope basic propulsion engines that would atleast complete all GSLV sagas.
According to this pic,CE-100 will power upper stage of heavy launch vehicle.

@S-DUCT

Do u got any idea what kind of fuel is ISROSENE to be used in SC200...

IMO,it is similar to RP-1 minus toxicity,carcogenic effects.

 

[Yogi]

^^
Yeah.we should first develope basic propulsion engines that would atleast complete all GSLV sagas.
According to this pic,CE-100 will power upper stage of heavy launch vehicle.

I don't think this image is reliable bcoz its talking about GSLVmk3 providing only 4t capacity to LEO...

N 100t capacity is still quite far n we might see some more design changes there like improved booster structure as in the case with Ariane 5 or if we r able to come up with something near about RD180 then more of Atlas V like structure IMO...

 

[S-DUCT]

I don't think this image is reliable bcoz its talking about GSLVmk3 providing only 4t capacity to LEO...

Check again,it mentions 4T ,10T to GTO and LEO respectively.

N 100t capacity is still quite far n we might see some more design changes there like improved booster structure as in the case with Ariane 5 or if we able to come up something near about RD180 then more of Atlas V like structure IMO...

Yeah this concept is very far away.IMO, ISRO should emulate NASA's SLS configurations.
Edit:that pic is from 'Indian Space Transportation System: Present Scenario and Future Directions'

 

[Yogi]

Check again,it mentions 4T ,10T to GTO and LEO respectively.

It mentions both if u have noticed, 10t on the lefthand side n 4t under ''Long term perspective''...

 

[S-DUCT]

@Yogi
SuperNova: ISRO Heavy Lift Vehicle
^^Link for that image.

 

[Yogi]

Yeah this concept is very far away.IMO, ISRO should emulate NASA's SLS configurations.

If u look at the Atlas V n SLS structure they r not quite different(except for the nose) i.e. They don't need much boosters bcoz of better n efficient engines n r able to reduce the T/W ratio by reducing the no. of stages.

Thats why i suggested that we might also not need bigger boosters if we r able to produce better Cryo. Engines.

But i must say look at all these developments i m really proud of ISRO for their achievements considering the budgetary constraints they work under...

 

[BlueDot_in_Space]

Thanx for the excellent post, it was really very helpful n very detailed explanation in very simple language...

I'll try to summarize what i have understood so far on this topic here, plz point out any deficiencies u notice

What i have understood so far is SCC engines r the most complicated but the most efficient engines n Russia leads this tech with its RD180 n r generally used at 2nd or 1st stage to get the rocket outta Earth's atmosphere as they r highly efficient n have high weight to thrust ratio. Most countries r still trying to catch up with the Russians here. These engines r so efficient that the considerably reduce the booster requirement of the rocket.(Indian eg.- SC200)

Then comes the expander engines which r also complicated(but not as much as SCC) n here the US leads the package with its RL10 these r also efficient engines n r generally used at the upper stage to lift the satellites to its final position. These r smallest in size n have max thrust limitation(around 300kn).

The smaller size helps in reducing the over all weight of the upper payload making the rocket lighter in size(in comparision to using Gas Generator Engines in upper stage) Although these r smaller in size n have limited thrust but provide good thrust to weight ratio good enough to lift the satelittes at upper stage.

But most countries r either not able to make them small enough (RL10 vs RD56) to provide the necessary thrust at the upper stage.(Indian eg.- CE7.5)

The last one r the Gas Generator engines which r least complicated n can be easily expended to provide higher thrust at upper stage(as high as 1300kn) but r not very efficient(bcoz the Gas generated in not reused again) resulting in lower weight to thrust ratio.

But these r the most widely used engines world wide n r used by majority of the nations(Except US n Russia for upper stage). France leads it with there Vulcan Engine. (Indian eg.- CE20 n CE60).

Even though they provide high thrust but at the same time increased weight too but most countries prefer them due to their simplicity. But they have to use much bigger engines to produce the required T/W ratio(In comparision to Expander Engines).

Plz provide ur views on my understanding.

@S-DUCT i would like to hear ur comments too on my explanation...

Yeap!! some more info:

 

[Yogi]

@Yogi
SuperNova: ISRO Heavy Lift Vehicle
^^Link for that image.

A good read but assuming that SC460 n SC800 would be much better engines in comparision i doubt we would use the same structure.

Besides i think we r atleast 1.5-2 decades away from such a powerful rocket so i believe a lot can change.

Plus with Russia coming back in space race(a possible future space JV could be on the table ) n ISRO is collaborationg more n more with NASA so these developments might also have some impact on our future rocket structures n engine developments...

 

[Yogi]

Yeap!! some more info:

Thanx for ur time sir but it would be really helpful if u could provide one-one example for each of the different types of Staged Engines from real world(any country u feel like).

It would help us understand better about their potential use in ISRO's future programs