Indian Space Program: News & Discussion - Sept 2016

vina · Post by **vina** » 17 Sep 2016 17:53

You made this comment earlier and I am trying to understand your point of view

Ok. The basic point is simple.

The current config of the GSLV MKii as per the GSLV D6 Mission Brochure is this.

From the brochure we have the following for the core stage. Thrust duration of 106 seconds and 138 Tons of propellant loading.
The 4 liquid boosters burn for 148.9 seconds. ie . The liquids are burning a full 43 seconds longer than the solids at rated thrust.

Now large solid rockets have a propellant mass fraction of approx 92% in the lower stages (from comparable engines).As a good approximation the core stage of the PSLV weighs 138/0.92 , ie 150 tons. So the empty weight of the core stage without propellant is 150 - 138 = 12 TONS which is HUGE.

So, what the 4 liquid boosters are carry are 12 TONS of extra dead weight for roughly (43/149) ~ 29% of their burn time! Ok even if you take the fact that the solids are lit 5 seconds before lift off and you adjust it to (38/149) it is 25% of their burn time.

Now this bad design is exactly the reason why the exact same tech Ariane 4 and Long March 4 are able to put 4 to 5 tons to GTO while the GSLV manages 2.5T. They dont carry a huge dead weight for 45 seconds !

prasannasimha · Post by **prasannasimha** » 17 Sep 2016 19:30

The empty stage acted as a truss/support for the other engines so not actually a "dead weight". The design was based on constraints at that time.

nirav · Post by **nirav** » 17 Sep 2016 20:02

I dont quite understand the need for some to keep dissing on the GSLV mk2 and insisting that it should undergo radical changes in design to be able to lift higher tonnage to GTO.
Its getting tiresome now with every GSLV launch comes the same old sh!t.

Want radical changes, how about a clean sheet design which btw is called GSLV MK3 ?
Ever thought of that ?

For satellites weighing in @2-3 tons for GTO the GSLV MK2 is the launcher of choice.
For higher the GSLV MK3 will be the launcher.

The criticism in here is not taking into consideration that the choices ISRO has made wrt its launcher configurations are after decades of work into coming up with a configuration and constantly working on optimizing it.

If only rocketry was as simple a lego blocks like some here suggest, do solid lagao, liquid beech me daalo, char solid lagao , use "methane" and other blah blah .. and voila you get 10 tons to GTO.

eggspurts in rocketry, ISRO already did that and came up with GSLV MK3 rather than putting everything at stake in radically changing design of GSLV MK2.

A lot of criticism is being made about lugging an empty SRB tank for 40 seconds in the first stage.
Either ISRO could have aligned the liquid strapons burn time wth the S139 and jettisoned it together or like they are doing use the L40s to the max burn time and achieve the best parameters from the combination being used. One must consider the fact that ISRO guys would have worked out all possible burn time angles to come up with an optimised solution.

One must try to calculate the impact of the 40 secs of the SRB tank riding on the 1st stage on the payload capacity rather than constantly banding about how "ineffecient" the design is.
Unless one has that figure and can demonstrate what a huge impact the 1st stage design choice has on the rockets payload capacity all this criticism is just plain nonsense.

ISRO manages to put satellites into orbit using the GSLV in very accurate orbits. Its also important to note that the requisite velocity for injecting the satellite into desired orbit is 9.77 km/s which is exactly what the current launcher configuration does beautifully even after "lugging deadweight" of the SRB tank
Takleef kya hai then ?

geeth · Post by **geeth** » 17 Sep 2016 20:14

They 'waste' another tonne of propellent by starting the liquid strap ons 4.8 seconds before liftoff

nirav · Post by **nirav** » 17 Sep 2016 20:16

^ must ask rocketry eggspurts to File a PIL.

Hizzoners will keenly listen and ban GSLV MK2.

Varoon Shekhar · Post by **Varoon Shekhar** » 17 Sep 2016 20:26

First satellite from IIT Bombay, to be launched on Sept 26th with Scatsat et al

http://timesofindia.indiatimes.com/city ... 337045.cms?

MUMBAI: IIT Bombay's first student satellite, Pratham+ , will be launched on September 26 from the Satish Dhawan Space Centre, Sriharikota. The nearly-10kg Pratham, which is also Mumbai's first satellite, will launch aboard the highly-proven Polar Satellite Launch Vehicle (PSLV) at 9.30 am.

Pratham's main role will be to measure what is known as the total electron count in the ionosphere. It has a

prasannasimha · Post by **prasannasimha** » 17 Sep 2016 22:13

^^ CAG investigation for wasting resources

vina · Post by **vina** » 17 Sep 2016 22:47

One must try to calculate the impact of the 40 secs of the SRB tank riding on the 1st stage on the payload capacity rather than constantly banding about how "ineffecient" the design is.
Unless one has that figure and can demonstrate what a huge impact the 1st stage design choice has on the rockets payload capacity all this criticism is just plain nonsense.

Why, didnt you read it clearly enough. The loss of payload to GTO is 2.5 tons. ie. Roughly half the potential throw weight to GTO is wasted / unrealised. That is HUGE!

Want radical changes, how about a clean sheet design which btw is called GSLV MK3 ?

The GSLV MK3 is EVEN more inefficient than MK2 in the current configuration. It puts only 4 T to GTO. (lower mass fraction than MK2)

A lot of criticism is being made about lugging an empty SRB tank for 40 seconds in the first stage.
Either ISRO could have aligned the liquid strapons burn time wth the S139 and jettisoned it together or like they are doing use the L40s to the max burn time and achieve the best parameters from the combination being used. One must consider the fact that ISRO guys would have worked out all possible burn time angles to come up with an optimised solution.

Performance optimisation is the last thing ISRO seems to have thought of with the MK2 . They basically slapped up some legacy stuff together (and that too badly and poorly designed) and went for a "Hail Mary" in terms of cryogenic engine to keep things together, but that too took way too much time.

Well, according to this Space website, the inert mass of S139 is a whopping 28 tons. This seems a pretty knowledgeable site with lot of technical info, from there,

The four boosters ignite 4.6 seconds prior to the first stage to allow the Vikas engines to reach operational conditions before the Core Stage is ignited and the rocket blasts off. In flight, the four boosters continue to burn after first stage shutdown and are separated from the vehicle with the first stage. The advantage of this simpler design is that a Booster Separation event is avoided, but it comes at the cost of performance because the four boosters have to propel the first stage once it has burned out which represents nearly 30 tonnes of dead weight

The 30 ton figure they have for the inert S139 stage seems excessive (giving a stage mass fraction of only 82%). I would stick with 90% fuel mass fraction for S139 and 12 tons as inert stage weight as an estimate. My numbers seem more reasonable.

The sad fact is , the GSLV MKII could have can be fixed with far less effort the lower stages of GSLV MK2 to realise it's full potential of 4 ton GTO, Instead, ISRO developed a brand new vehicle with an even more sub optimal config with a name plate capacity just 4Ton GTO! . In the process, they developed a new solid stage, a new clustered liquid stage and a brand new cryogenic stage!

The only way to salvage this haphazard effort is to get the semi cryogenic stages in and replace the inefficient lower stages fully, the ULV/"Modular" concept. That would be a 3rd configuration altogether in less than 15 years!

abhik · Post by **abhik** » 18 Sep 2016 02:49

disha wrote:
abhik wrote:Re returning the whole first stage vs just the engines, Jeff Bezos unveils Blue origin's next launcher:

https://twitter.com/JeffBezos/status/77 ... 78304?s=09
Abhik'Ji - that is an impressive rocket., and looks very good and also the booster returns back to earth after its flight.

But.,

1. Does it fly?
2. When will it fly?
3. Will it fly regularly - like some 20+ consecutive launches *without* *any* mishap?
4. Will it be cost effective? And if the answer is yes - How?
5. What market will it serve? Space Cargo (water to ISS for example)? Human Space Exploration? Launching of EO Sats? Comm Sats? All of the above? One of the above? Some of the above?

I think answers to question specific to Blue Origin rockets itself must be taken up in 'International space' thread.

But I do have to point out., for folks going ga-ga over Blue Origin and SpaceX., fact is they are looking over at ISRO and trying to learn how ISRO is doing what it is doing. There is a healthy competition and no serious rocketeer is running down other's program (even Chinese!).

It is reported to fly by the "end of this decade"(which is not that far away), and some of those questions will be answered only in due time. I only posted this in the context of the reuse of just engine vs the whole first stage debate. The New Glenn will be the second launcher to demonstrate complete 1st stage recovery after the Falcon 9 (and will likely do it years before either ULA or Ariane are projected to demonstrate their reusability model, if ever). By the time ISRO starts to make concrete plans for the future launcher the trend on reusability will be clear.

enaiel · Post by **enaiel** » 18 Sep 2016 09:11

My 2c..

ISRO created PSLV using 4 stages with a strange mix of propellants - but that was because it was what they could manage given the situation at the time. It was a low risk approach to get a working launch vehicle that has since proven to be a reliable work horse. GSLV was designed around re-using as much of PSLV as possible with the only unknown being the cryogenic upper stage which they bought and licensed from Russia, again with an aim to reduce the risk. Even the boosters not separating is to reduce risk. LVM3 continues down the path of low risk designs. At least this time the boosters will separate, so I think they are intentionally under-reporting the max capacity of the launcher.

If they started off trying to master semi-cryogenic and cryogenic engines, we might have ended up like Japan, with an incredible TSTO workhorse H2A/B that can deliver payloads to ISS. Or we could've ended up like Brazil, with a canceled space program. I am glad that ISRO took the low risk approach - because we might have not had Chandrayaan and Mangalyaan. But at the same time, the low risk approach has kept us at the back of the pack. And that has got to change now that there is no possibility of turning back on our space program.

And I think that ISRO has already started to change. In interviews ISRO chairman mentioned that with companies like SpaceX in the commercial launch space, ISRO will have to improve their efficiency if they want to stay in business. And so they have started working on much better designs like ULV and RLV with some urgency. Although I would have preferred if ULV used semi-cryogenic engines for it's boosters as well, instead of solids, to increase thrust and commonality among it's components.

symontk · Post by **symontk** » 18 Sep 2016 09:26

The argument is that 12 tonne is lugged for 40 seconds. But that is in first stage, any weight saving in first stage will give only marginal improvement for the final payload weight. Like if you save 100 tonnes, you can add 1 tonne to the payload weight (based on an in house article I read about PSLV/GSLV long time back). So if you save 12 tonnes, you will add 120kg, which is of course significant BTW considering the miniaturization that is happening in electronics every year. But to say that removing it would help GSLV2 attain payload of 4 tonnes is not correct

GSLV2 would improve its payload capability over the years like PSLV improved its. But that would be achieved by removing redundant electronics and other things in the upper stages once ISRO gains confidence in the cryo engine. The upper stage weight savings directly translates to payload. Like if you remove 1 tonnes of weight from upper stage, you can add 1 tonnne to the payload

geeth · Post by **geeth** » 18 Sep 2016 10:16

Indeed..the improvement in payload capacity will not be much and definitely not double. Weight reduction in 2nd/third stage would have a far better effect on payload enhancement.

disha · Post by **disha** » 18 Sep 2016 11:00

abhik wrote: The New Glenn will be the second launcher to demonstrate complete 1st stage recovery after the Falcon 9 (and will likely do it years before either ULA or Ariane are projected to demonstrate their reusability model, if ever). By the time ISRO starts to make concrete plans for the future launcher the trend on reusability will be clear.

I would paraphrase it more like the New Glenn may likely demonstrate complete 1st stage recovery by end of the decade.

Now here are the subtle points which people who say look at SpaceX/NewGlenn etc to ISRO miss. Just because 1st stage is recovered does not mean 1st stage *will* be reused immediately. It is likely to be still a decade away from reusability of 1st stage. Multiple tests will be carried out on the recovered platform before all the 9 engines recovered will be put into an operative mission.

What SpaceX has demonstrated is partial recoverability. They are saying that by putting some extra fuel., the 1st stage with its 9 engines can be recovered. And that's all has been demonstrated. This is at the same level as RLV with the scramjet test.

symontk · Post by **symontk** » 18 Sep 2016 14:44

Regarding the new design for Gslv3 attempted by ISRO, cryo stage has entirely new technology and they are going for a 4 meter sized rocket. In that case isn't it better to use proven one rather than a new one. If ISRO went for SemiCryo instead of Vikas in case of failure nothing would ever get validated

SSridhar · Post by **SSridhar** » 18 Sep 2016 15:16

IMO, there is no point in discussing the decision made in the 80s on the roadmap. In hindsight, and after having achieved some success, many things can be better. I will quote from a lecture given by former ISRO Chief Dr. Kasturirangan:

The sizing of the GSLV had to consider the increasing space segment capacity demand in the coming decades, the experience we had gained in launch vehicle technology and optimal utilization of PSLV heritage in order to reduce the cost, improve the time schedule and increase the reliability of operation. A large number of vehicle design options were studied to evolve an optimum GSLV vehicle design which can cater to two classes of satellites viz. 1500 Kg and 2500 Kg. class. The chosen configuration is also consistent with range safety and mission considerations, modularity in design and growth potential.

GSLV is a three-stage vehicle, the core being the 129-tonne solid booster as in PSLV, the second stage being a liquid propulsion system with a propellent loading of 37.5 tonnes again as in PSLV, and the upper stage being a restartable cryogenic engine with a propellant loading of 12 tonne and using liquid oxygen and liquid hydrogen. The core with six ASLV-type strap-ons, symbolically represented as (S125 + 6S9) + L37.5 + C12, is capable of launching a 1500 Kg satellite into GTO which forms the Mark 1 version of GSLV. By replacing the Mark 1 strap-ons with four liquid strap-ons of Vikas engine with a propellant loading of 40 tonnes each, GSLV Mark 2 (S125 + 4L40) + L37.5 + C12 is capable of launching upto 2.5 tonnes into GTO. Without any strap-ons, GSLV has almost the same capability as PSLV and GSLV Mk 1 & Mk 2 can launch over 1500 Kg and 2500 Kg into sun-synchronous polar orbit. The first two stages of the chosen configuration of GSLV fully exploit PSLV pedigree. PSLV launch Pad itself is being augmented to launch GSLV.

A Nandy · Post by **A Nandy** » 18 Sep 2016 20:24

It is likely to be still a decade away from reusability of 1st stage.

http://www.space.com/33444-spacex-reusa ... -fall.html
http://www.marketwatch.com/story/spacex ... 2016-08-30

SpaceX’s recycled rockets have found their first client — just don’t call them used.

Satellite operator SES, based in Luxembourg, said Tuesday it will be the first company to launch its SES-10 satellite on a “flight-proven” Falcon 9 rocket booster from SpaceX. The launch is scheduled for this fall.

While we can sit on our laurels, we need to push even harder now so that companies like SpaceX do not even remain competitive in the GTO launch market. They can goto Mars.

vina · Post by **vina** » 19 Sep 2016 08:02

symontk wrote: So if you save 12 tonnes, you will add 120kg, which is of course significant BTW considering the miniaturization that is happening in electronics every year. But to say that removing it would help GSLV2 attain payload of 4 tonnes is not correct

This is not the same mass at take off. The entire idea behind staging is to improve mass fractions as propellants get used up. Carrying this 12 ton dead weight simply prevents this.

How bad is it ? Look up the figures for Long March 3A. It does not use any booster rockets , clusters 4 of 75KN class hypergolic rockets in the core, a single 75KN hypergolic stage for 2nd stage and a 3rd stage cryogenic.

Now the Indian versions of the same hypergolic rocket is more efficient as is the Indian cryogenic stage (both have appreciably higher Isp than the Chinese version). But, the Chinese rocket puts 2600 Kg to GTO, which is the same as the GSLV, which as a solid core in addition! So net-net, it seems that the entire S139 stage contributes ZERO, and if going by what LM3A has done, if they had clustered the 4 liquid engines into the core , you probably would NOT have neeeded any solid boosters at all (do away with the S139 cost and weight) for 2.5T to GTO!

So, the LM 3A has a take off mass of the order of 250 tons , while GSLV MK2 has take off mass of 415tons.

The configuration of LM3 series that corresponds to the GSLV MK2 is the LM 3B which has 4 booster in the lower stage and puts 5 tons to GTO!

Ok, the Chinese launchers inject at an inclination of 28 deg for GTO, while ISRO injects at 20 deg. , and going by the Long March user guide , the payload for a 20 deg inclination launch is 1.8 Tons for LM3A and 4 Tons for LM3B .But then the Chinese launch from a higher latitude as well and less benefit of the earth's spin unlike the GSLV, and that sort of evens out the two. That is why I maintain, that the GSLV Mk2 , if "fixed" has the potential of around 5 Tons GTO. That begs the question of why did ISRO build he GSLV MKIII at all a brand new vehicle.

IMO, there is no point in discussing the decision made in the 80s on the roadmap

Now even, if one can understand the design choice of the 80s for the GSLV MK1/2, I simply CANNOT undertand the design choices for GSLV MKIII, which were made in around 2000 , especially for the L110 liquid stage.

The L110 is a 4 M dia stage and they cluster TWO liquid engines, when there is ample space for 4 . A 4 engine cluster core would have "fixed" the GLSV MK1/2 (like shown for LM3A, and with the same 4 liquid boosters as in present config, would give 5 tons to GTO and removed the immediate need for GSLV MK3) .The Long March's 1st stage is a 3.3 M dia core and the engines are clustered as below. Developing a 4 cluster core engine stage would have been the easiest and shortest path to realizing 5 tons to GTO instead of the costly and long effort to develop and entire new vehicle!

symontk wrote:The argument is that 12 tonne is lugged for 40 seconds. But that is in first stage, any weight saving in first stage will give only marginal improvement for the final payload weight.

Paging AmberG . Another worthy phyiscs question. How much more would the payload to GTO be, if the spent core stage has been dropped? We know all the IsPs and the masses and this can be calculated from the basics. I dont have the time to do it, but will be a worthy exercise of applying Tsialkovski's rocket equation.

disha · Post by **disha** » 19 Sep 2016 12:18

A Nandy wrote: While we can sit on our laurels, we need to push even harder now so that companies like SpaceX do not even remain competitive in the GTO launch market. They can goto Mars.

Push harder where? Without a cogent answer to why one needs "10 Tons to GTO commercial space launch capability"., statements like "we can sit on our laurels and need to push even harder now" are reduced to cliches.

So the question is 'Push where?' - Given that rocket science is costly and requires highly skilled AND talented persons - a country has very limited resources - and hence pick only one (only one!):

1. RLV (Re-usable)
2. Scramjet (lower orbit cost to maybe $1000 per KG)
3. ULV (Universal Launch Vehicle., like the plug-and-play rocket concept) - here is a simple enunciation of it:

"Once ISRO masters clustered liquid engines, semi-cryo, cryo in both GG and SC cycle, solid motors., GSLV MkIII will be the ULV. Need a polar capability., take out the solid boosters and launch a core only 2-stage rocket. Need a higher LEO capability., replace the UDMH liquid cluster with a semi-cryo. Need heavy lift to GTO., replace UDMH based liquid with semi-cryo. Super heavy lift., maybe add in two more solid stage boosters"

This above ULV will give multiple mission capabilities for the next 2-3 decades.

4. 10 Tons to GTO (at $10,000 per KG) by adding strap-ons to GSLV-MkII.

Now out of the above., pick only one. Yes only one. That enables one to 'Push harder' and 'not sit on laurels'.

disha · Post by **disha** » 19 Sep 2016 12:29

Also people confuse reliability with capability.

Just because a rocket is capable to launch '10 tons to GTO'., does not mean it will reliably launch '10 tons to GTO'.

Also why '10 tons to GTO' (or equivalent of 20-30 tons to LEO)? What use will it be?

1. If it is to launch man'ed missions - then solid boosters are out. Particularly one mishap with solid boosters and ISRO's space program will be killed.

2. To launch space station missions., does one need capability at the cost of reliability AND launch cost or does one need reliability and cost effectiveness at the cost of capability (3 variables to an equation., only 2 of the 3 are avl. at any design point. For example a highly capable launcher need not be reliable and may not be cost effective or a highly reliable launcher may not be capable and/or cost effective. Rarely one can have a highly reliable and cost-effective launcher (for eg. PSLV) ).

---

Answer to how much lack of capability to GTO is affected because ISRO lugs the solid stage for some more time has been answered and has been answered earlier as well. It is not more than 150 Kgs.

disha · Post by **disha** » 19 Sep 2016 12:33

symontk wrote:Regarding the new design for Gslv3 attempted by ISRO, cryo stage has entirely new technology and they are going for a 4 meter sized rocket. In that case isn't it better to use proven one rather than a new one. If ISRO went for SemiCryo instead of Vikas in case of failure nothing would ever get validated

Further on semi-cryo., industrial base on refined petroleum has to be developed first. I will come to the issues of semi-cryo later.

SSridhar · Post by **SSridhar** » 19 Sep 2016 13:56

vina wrote:The L110 is a 4 M dia stage and they cluster TWO liquid engines, when there is ample space for 4 .

Are you sure? The engine diameter of each Vikas L110 is 1.7m.

prasannasimha · Post by **prasannasimha** » 19 Sep 2016 19:27

Vikas is 2.9 Meyers and nearly 1 meter wide. L110 is 4 meters wide. To accommodate 4 engines you need more than 4 meters as space for plume divergence is required.Also L110 needs space for nozzle movement for thrust vectoring.

vina · Post by **vina** » 19 Sep 2016 21:03

SSridhar wrote:Are you sure? The engine diameter of each Vikas L110 is 1.7m.

The L110's engines are lit not at lift off, but at high altitude. The nozzle is over expanded if lit on the ground and will be inefficient. The Vikas/Viking engines that are ground lit have nozzles of 1 m diameter.

Check out this link of Vikas and Viking Engines. The Vikas -X , Vikas 2B are analogous to Viking 4B with nozzle dia of 1.7m. Check out Ariane 4. The Viking 4B is used in the 2nd stage. The first stage L220 cluster uses Viking 5C engines which has a nozzle of 1m diameter. The equivalent Vikas 1/ 1+ (from the table in the link I posted) similarly has a dia of 1m. Vikas 1/1+ are the engines used in the GSLV MK1/2 booster stages.

Now the Ariane 4 L220 is a 3.8m diameter stage. It packs 4 Viking 5B engines, with sufficient margins for engine deflection in the x and y planes for pitch, yaw, roll etc. Mounting 4 Vikas 1+ on a 4m dia stage wont be a problem at all.

What ISRO really should have done when they developed the clustered stage for MKIII, they should have done an equivalent of the Ariane-4's L220 stage / Long March 3 first stage,hat would be ground lit and that could have been used first in MK1/2, and then replaced that with a Lox /Kerosene stage for a higher payload to orbit in later versions , and probably clustered the 75KN cryogenic engine into 2*75 KN (like the Centaur upper stage, with comes in 1 engine or two engine versions) and got a full range of payloads from 2.5 T to 10 Ton GTO in a very efficient 2 stage config (when they got the Kerosene/LOX in, but even otherwise, they would have got a good 5 ton GTO capability in quick time with hypergolic lower stages and cryogenic upper stages, CE 7.5).

Instead, for some inexplicable reason, they created an L110 with 2 Viking engine stage that is air lit , an S200 stage ,a brand new cryogenic engine CE-20--infact an entire new launcher family , whose core L110 needs to be replaced ASAP! Sorry, Can't figure out why.

disha · Post by **disha** » 19 Sep 2016 22:35

This sounds more like an upgrade path. An ISRO version of L220 with 4-clustered engines can be put in place as the clustered engine reliability increases. This will be more like a natural progression for GSLV-MK III.

The semi-cryo is still work in progress., ISRO signed MOUs with Ukraine and then with Russia and that too restricted to ground infrastructure to avoid geo-political risks. If at all semi-cryo comes., it will be only in the next decade! In the meantime GSLV Mk III is flying within a year.

Further., CE-7.5 is a variable thrust SC engine (from 75 kN to 82 kN) with a significant higher chamber pressure than the CE-20 (with 200 kN thrust). It can be surmised that CE-20 can be scaled better compared to CE-7.5

Again the decision for clustering engines vs. single large engine is non-trivial. Further., when GSLV Mk-III was on drawing board., CE-7.5 was still being validated (and deemed unreliable)! So either pick a cluster of partially validated (or still non-validated) CE 7.5 or pick up a new designed but less efficient large engine (and more likely to be a reliable engine, see interview of ISRO chief on testability of the CE-20)

At the same time., the payload capabilities were being played out internationally. In fact commercially 4-5 ton to GTO is the sweet spot.

So the upgrade paths become simple for GSLV-Mk III and also options with different engines, stages and fuel combinations open up.

Indranil · Post by **Indranil** » 19 Sep 2016 23:37

The upgrade path has been already laid out.

1. There will be no more Vikas-based boosters after MkIII
2. Everything moving forward will be SCE 200 based for a while, which is equivalent to a cluster of 3 Vikas engines
3. Next step is cluster of SCE 200 engine + solid boosters (when required)

Vina, your points are valid. I have always thought why did they not design the booster and the strapons to fire for the same duration of time. I don't think it would have boosted the payload capacity of GSLV by 1.5 tons, but by a few 100s of kgs. I agree with you and that is important too. But all this is too obvious to people who are actually building these rockets and launching them successfully. We should probably find out why they went down the path they did. May be, they did not have the funds to do anything till very recently*. So they kept working with what they already had and small increments there of. By the way, I am told that MkIII is not the evolution of GSLV, but the stepping stone to ULV.

* Reminds me of this talk given by Wg Cdr (retd) Unni Pillai about the lessons learnt from the ALH project. He said MBB should not have been let go at that critical stage where HAL did not yet have the capability to take the design and testing forward. Dr. Atre at the end of the talk said, it is obvious that we shouldn't have. But at that time, our country was at the verge of bankruptcy and we were pawning our gold, we did not have the money to pay the consultants. So we should not judge them without being in their situation.

disha · Post by **disha** » 20 Sep 2016 07:37

If one goes by numbers alone., then a LH2-liquid Fluorine has even higher specific impulse than LH2/LO2 combination and can potentially give more than few hundred kgs payload capacity boost. But is never used and most likely never will be. Why?

---

IndranilRoy'ji - a fly in the ointment in your scenario., SCE-200 is not ready yet and will not be around this decade. What happens if it does not come out by the beginning of the next decade or by the end of the next decade it is not even needed? Look at the evolution of Arianne V and Arianne VI.

Problem with semi-cryo is the fuel itself., yes it is denser than LH2 and far less toxic than UDMH/HNO4 with better specific impulse and for its advantages it has its fair share of disadvantages too. RP1 equivalent kerosene has to be sourced from very few specific oil wells which produce oil with low sulphur content to start with. Further, it has to be refined to remove sulphur to the point of <=30 mg to a kg. Sulphur in the RP1 helps polymerization which means that when RP1 is used to cool the nozzle it will help polymerize the fuel and gum up the fine channels under high pressure and temp. leading to breakdown of the nozzle. RP1 further is refined to ensure that it has very high saturated hydrocarbons which tend to polymerize less. In fact if necessary., the nozzles are not cooled by RP1. This requires exotic alloys for the nozzle (niobium alloys for radiatively cooled Merlin-1C vacuum engines).

Interestingly., RP1/LOX2 engines also have issues with restartability., particularly if the nozzles are regeneratively cooled. That is why in missions where restarts are required (SSME for eg) they tend to primarily be LH2/LOX types if not the UDMH/HNO4 types.

Changing gears., it has been pointed out several pages back., GSLV Mk III is the foundation for ULV. And ULV can be thought of design expression till 2050s with various rocket stage technologies in play to give ability to mission designers to tailor a specific mission reliably.

From that perspective., all of ISRO's rockets are evolutionary., right from ASLV/PSLV/GSLV Mk-I/MK-II and now GSLV Mk III. Since ISRO was making small bets in mastering technology and building capacity. ISRO could have used its existence and gone in for a "10-ton payload to GTO" (which nobody needs currently for commercial purposes) and could have won bragging rights but it would as well have ended up painting itself into a corner. Take a look at JAXA itself and also the Chinese space program. The Chinese are scrambling to get a solid booster in place and are trying to ramp up on a cryogenic engine. Both of which will not be in play till the early part of next decade. In that, Chinese rocket program has fallen behind by atleast a decade.

With its conservative bets., ISRO is opening up itself to have a wide range of reliable plug/play stages (we call it ULV) and its foundation is GSLV-Mk III (which further built on the foundations of solid stage boosters, liquid and cryo engines of GSLV Mk-II which was a built up from PSLV which was a built up from ASLV!!).

So yes., on paper with SCE-200 we have tasked ourselves as the holy grail to be achieved by ISRO and setting us up for a collective rona-dhona when the SCE-200 may get delayed or even cancelled. And if it comes through, it is just another stage (or a piece) in the ULV tailored to a specific mission capability.

However it is sad is the degeneration of the thread in the past few pages for a penchant to gain immediate '10 tons of GTO capability' or rather crudely put a penchant for size comparison to other space agencies with irresponsible and purposely misdirected (mis)understanding of physics (quoting 1-2 ton payload boost vs. actual 100-200 Kg payload boost - a complete 10x ballooning)., unsubstantiated numbers (furthered with asking others to do the homework) and sheer derisive name calling. Basically a remarkable lack of understanding of basic science and lack of empathy for the engineers who toil within the choices out of their control., and anybody who would have countered such elitism would have been bullied into submission.

So yes., in principle I too am curious on why ISRO is lugging the empty shell in GLSV-MK II and instead of deriding them and doing a name calling on them, I am more interested in understanding what choices they had to proceed on that path.

For example., if there is a reliable infrastructure to manufacture S-139 that has been flight tested and validated several times on PSLV., it makes sense to use it as a base for GSLV-Mk 1/II. One has to note that the S-139 has been launched successfully and consecutively for 30+ flights (PSLV/GSLV combined together). Very few agencies have developed a very reliable very large solid state booster (only two other than ISRO - NASA and ESA). Trading some 150-200 kilos of payload capacity and gaining near 100% reliability is a very laudable goal indeed. And deriding that effort is plain intellectual dishonesty.

One has to understand what ISRO does what it does before one tears it apart. Take for example LVMX-3. It was an experiment within an experiment within an experiment. First of all the aerodynamic profile and S-200 were validated., then air-lit clustered L110 engines were validated followed by CARE experiment. A pragmatic focus on capacity building is at play here where raw payload capacity is not the goal, but overall payload capability and reliability for different mission objectives is the goal.

It is interesting that ISRO on this very thread has been compared to SpaceX and Chinese space program. It shows complete lack of confidence in one's own capability! ISRO is neither SpaceX with deep experience of NASA's engineers and its launch pads and infrastructure built up during apollo program and accompanying billion dollar deep pockets and neither it is Chinese program tasked with maintaining Honor & Dignity stated on a political goal instead of being in service to its own citizens (show me Chinese EO infrastructure - from satellite building to using it and I have a Semi-cryo engine in my backyard to sell).

Question on what ISRO should focus on is valid. ISRO's overall goal is to reduce launch costs - basically reduce it by 10x (and even if it reaches 2x., that is laudable) and under that over-arching goal, ISRO must focus on technologies to achieve it and build its capabilities and capacity.

sivab · Post by **sivab** » 20 Sep 2016 10:04

disha wrote:
Problem with semi-cryo is the fuel itself., yes it is denser than LH2 and far less toxic than UDMH/HNO4 with better specific impulse and for its advantages it has its fair share of disadvantages too. RP1 equivalent kerosene has to be sourced from very few specific oil wells which produce oil with low sulphur content to start with. Further, it has to be refined to remove sulphur to the point of <=30 mg to a kg. Sulphur in the RP1 helps polymerization which means that when RP1 is used to cool the nozzle it will help polymerize the fuel and gum up the fine channels under high pressure and temp. leading to breakdown of the nozzle. RP1 further is refined to ensure that it has very high saturated hydrocarbons which tend to polymerize less. In fact if necessary., the nozzles are not cooled by RP1. This requires exotic alloys for the nozzle (niobium alloys for radiatively cooled Merlin-1C vacuum engines).

Interestingly., RP1/LOX2 engines also have issues with restartability., particularly if the nozzles are regeneratively cooled. That is why in missions where restarts are required (SSME for eg) they tend to primarily be LH2/LOX types if not the UDMH/HNO4 types.

ISRO is SDRE and do things SDRE way. They do disappoint TFTA jingoes though.

ISRO kerosene is called Isrosene and was ready to be commercially manufactured by an SDRE company HOCL 2 years ago.

http://www.hocl.gov.in/writereaddata/54 ... Report.pdf

After initial trial runs on pilot scale the ‘In-house’ developed vapour phase continuous
process for ISRO’s specific grade of Kerosene (Isrosene) was fine tuned. A model
developed on laboratory scale was also verified on pilot plant scale. Regular runs
with optimized parameters in ‘scaled down version’ of HOC’s commercial plant were
successfully completed. The product quality from these runs has been re-affirmed and
the capacity of the plant has also been established, based on these runs. The technology
is now ready for implementation in HOC’s available commercial plant. In this regard
meeting with ISRO was held. The detailed proposal was sent to ISRO. Company’s further
contribution in IPR field is maintained and grant of three nos. of Indian patents has been
obtained during this year.

More SDRE stuff on SCE from ISRO, sorry no exotic TFTA alloys

http://www.isro.gov.in/new-brazing-proc ... ished-isro

Manufacture of thrust chamber and pre-burner of Semi-Cryo engine requires joining of two shells by vacuum brazing. The inner shell is made of a copper alloy, whereas the outer shell is made of stainless steel. The inner shell has ribs on its outer surface which need to be joined to the inner shell. This joining is achieved by brazing which results in formation of active cooling channels in the finished hardware.

...

Using this setup, subscale hardware was realized and was evaluated through X-Ray radiography and was pressure tested by Semi Cryo Project team. It was confirmed that the hardware were free of blocks in the channels through X-Ray radiography. Pressure testing was done up to 500 bar and no de-bonding was observed. Figure 6 show the hardware and the cut cross section with typical rib fracture observed beyond 500 bar which implies the soundness of the brazed joint.

As it is a simpler process, brazing can be done at industries without any special equipment, and the advantages of this process are:

This is a simple method of applying coatings by electroplating in the channels thus avoiding use of costly braze foils
Time consuming and laborious brazing foil assembly on the contoured ribs is simplified.

They will only come up with some SDRE solution for all SCE problems. Such a disappointment.

They even hot tested CE20 engine for 25% more duration than needed by C25 stage, so it was tested for C30 stage as well. Very SDRE.

http://www.oneindia.com/india/isro-test ... 11850.html

The latest test was for a duration of approximately 25 per cent more than the engine burn duration in flight.

disha · Post by **disha** » 20 Sep 2016 10:14

Glad to see progress on SC-200!

Hey reusable on RLV is a different ball game! RLV is not a SpaceX type 'stage returnable' rocket and hence the comparison does end there.

I further did not get around to post on why RLV should be a focus and why RP1 (or its ISRO equivalent) is actually a good choice for RLV (higher density., lower volume and can be used in scramjet engines!). So yes it is great to see that RLV reusability is highlighted but in terms of reusability bringing in RLV is shifting the goalpost from traditional expendable launchers to re-usable launch vehicle. That does not negate my point!

Added later: The second link on the CE-20 test is the extended test of the cryogenic engine and not the semi-cryo., basically semi-cryo is at sub-scale testing level (good) but not yet at a fully realized stage level (targeted early part of next decade).

My point was, is and remains that semi-cryo must be pursued but it is not necessary the be-all and end-all for "10 tons to GTO" ~~as some 'SDRE jingo'~~ post it out to be.

*And what is this SDRE Jingo Vs TFTA Jingo about? If it was directed to me for my post., well the attribution is not appreciated.
---

Will be glad somebody corrects me., was USAF Titan III (3e?) also air-lit? GSLV-Mk III does look a lot like Titan-III E except for the payload fairing enclosing the centaur upper stage!

In that sense it appears., the GSLV-Mk III boosters are 'stage 0' optimized for lower atmosphere and the liquid core (stage 1) is optimized for high altitude (near vacuum) conditions.

sivab · Post by **sivab** » 20 Sep 2016 10:22

disha wrote:
*And what is this SDRE Jingo Vs TFTA Jingo about? If it was directed to me for my post., well the attribution is not appreciated.

Not directed at you sir. It was a general comment about TFTA jingoes who have never built any rocket second guessing ISRO scientists/engineers. As the saying goes hindsight is always 20/20.

disha · Post by **disha** » 20 Sep 2016 10:27

^^ Thanks! BTW., it is not even 20/20 - if there is no empathy - it is more like a blind irresponsible statements.

As I used to say to my 5 year old., it is easy to do back seat driving - even for a 5 year old. Particularly for a 5 year old.

sivab · Post by **sivab** » 20 Sep 2016 11:06

disha wrote: Hey reusable on RLV is a different ball game! RLV is not a SpaceX type 'stage returnable' rocket and hence the comparison does end there.

I further did not get around to post on why RLV should be a focus and why RP1 (or its ISRO equivalent) is actually a good choice for RLV (higher density., lower volume and can be used in scramjet engines!). So yes it is great to see that RLV reusability is highlighted but in terms of reusability bringing in RLV is shifting the goalpost from traditional expendable launchers to re-usable launch vehicle. That does not negate my point!

1. Seems you missed a subtle point I was trying to make. ISRO always tries to hit two things at once. This is a very SDRE trait that even Modi talks proudly about himself. SCE200 is meant for both ULV and RLV. Though ULV is targeted first. Same thing they did with CE20 testing for both C25 and C30. It is ISRO slide, I am not trying to bring RLV into conversation. Now that you mentioned it...

2. ISRO RLV is a completely different thing than NASA shuttle. It is a stage returnable rocket. See the difference in these slides. The winged structure is not payload/orbit stage, it is first stage and will land using wings. ISRO does plan to land second/orbit stage on legs like SpaceX. All I am trying to point to here is ISRO thinks differently and I appreciate that.

disha · Post by **disha** » 20 Sep 2016 11:43

^^Sivab., actually 'NO'. I did not miss any subtle point - in my earlier post I pointed out that ISRO does 'experiment within experiment within experiment' which is both remarkable and laudable. ISRO's is a different and unique thought process., and is akin to hit two-to-three things at once.

Now I do concede partially that there are gaps in enunciating my understanding of what it does with RLV and other space experiments/missions and goals within the rubric of 'experiment within experiment within experiment'.

SSridhar · Post by **SSridhar** » 20 Sep 2016 17:36

vina, my discussion with a person who knows these things suggests the following: the airlit L110 when it is lit 110 secs after the S200, builds up acceleration very rapidly as the atmosphere is already crossed and even as the mass rapidly falls from ~150T to ~40T. The structural integrity issues with acceleration are the factors considered. When liquid engines become real boosters for lift-off, degree of clustering may be increased.

The sense I get is that because of ISRO's high capabilities & confidence in solid boosters, probably ISRO persisted with the S200 SRBs and the L110 core stage is actually a second stage.

symontk · Post by **symontk** » 20 Sep 2016 20:18

sivab wrote:1. Seems you missed a subtle point I was trying to make. ISRO always tries to hit two things at once. This is a very SDRE trait that even Modi talks proudly about himself. SCE200 is meant for both ULV and RLV. Though ULV is targeted first. Same thing they did with CE20 testing for both C25 and C30. It is ISRO slide, I am not trying to bring RLV into conversation. Now that you mentioned it..

You might be wrong. From my understanding SC200 is not reusable, of course the experience with semi-cryo will be useful in RLV. RLV engines need to developed separately and it is a different effort. Also ISRO targets watered down stages initially and so I wouldnt be surpirsed if SC200 turn to SC240 in future or C25 becomes C30

Having said that ISRO has a long way to go in RLV tech but will catch up with others soon. Their approach as you mentioned is better than what US did in shuttle. But one advantage that no other country has (except Russia / China) is that it can even recover 2nd stage and not just the first stage as for US / France / Japan due to A&N / IO Islands in its flight path (This was mentioned in of the newspaper articles)

vina · Post by **vina** » 20 Sep 2016 21:46

SSridhar wrote:vina, my discussion with a person who knows these things suggests the following: the airlit L110 when it is lit 110 secs after the S200, builds up acceleration very rapidly as the atmosphere is already crossed and even as the mass rapidly falls from ~150T to ~40T. The structural integrity issues with acceleration are the factors considered. When liquid engines become real boosters for lift-off, degree of clustering may be increased.

The sense I get is that because of ISRO's high capabilities & confidence in solid boosters, probably ISRO persisted with the S200 SRBs and the L110 core stage is actually a second stage.

I spent half an hour putting together a spread sheet which implements the Tsiolkovsky Rocket Equation to answer the question of what if the GSLV MK2 had been built the "right way", with the 4 liquids clustered in the core and the S139 as the booster and dropped after it burns out, what would the difference in payload be ? Will it be "small" (lets say less than 250kg as a few folks argue?)

For that I pulled out the GSLV D6 Mission Brochure that has the lift off mass of the GSLV D6, the lift off mass of the CUS stage, the payload weight and most importantly, a table with "Flight Events" and the relative velocity achieved at each event.

I watched the Youtube clip of the launch and I deduce the velocity at 109 seconds (which is the S139 stage shuts down) is 1.45 km/s (roughly, which is a good approx.) . We know the Isp of each stage and also the burn rates to stages .Given the lift off mass was 415.712tons and the 139 tons of solid fuel is spent as well as the 4 L40s have burnt around 118tons, the weight of the vehicle, at 109 seconds is JUST 158 tons which is less than 40% of the lift off mass.

Now the analysis is easy. If the S139 is dropped at this stage, the mass would be that much less. I have taken the spent PSLV stage case as 30 tons (as publicly available information suggests) and worked out the numbers and also the case if the case is 12 tons (which I worked out at 92% stage fraction).

So , if the vehicle continues in the current config , the vehicle mass initial vehicle mass is 158 tons, V of 1.45km/s and at L40 shut down is 109 tons . The vehicle drops 54 tons (30t - S139 and 24 tons of 4 Nos L40). The mass at GS2 start is 59t and at GS2 shutdown is 25.24 tons. Taking the payload weight and empty weight of the CUS and adapter , all at 6 tons (which is what the vehicle must weigh at CUS shutdown), we calculate the weight at CUS start at 18 tons (from Gaspudin Tsialkovsky) , which means that the 2nd stage empty weight + payload faring weight which is shed is 7.24 tons , which I think is reasonable, as the GS2 is of similar size and propellant loading as L40 and the fairing will be around 1 ton , along with the adapter.

Now in the "right way" config, the vehicle mass initial vehicle mass is 129 tons, V of 1.45km/s and at L40 shut down is 88.42 tons . The vehicle drops 24 tons only ( 24 tons of 4 Nos L40). The mass at GS2 start is 68tons and at GS2 shutdown is 27.558 tons.Dropping the 7.24 tons for the 2nd stage + payload fairing which we calculated earlier, the weight at CUS start will be 20.31tons and after same delta v of the stage as per the current config, the final mass will be 7.316 tons, which is is an INCREASE of 1.28 tons over the current config. So yes, it bears out what I said that the GSLV MK2 has a potential of 4 Tons GTO (by looking at comparable tech launch vehicles). Gaspudin Tsialkovsky seems to say yes.

If the S139 spent stage is 12 tons , the increase in weight to GTO is around 575Kg. Posting the tables data I have. DeltaV is the actual
Lugging S139
Event Start V End V Isp Isp*g Mass Initial Mass Final DeltaV
SBO Cutoff @109s to L40 Shutdown 1450 2392.3 255.20 2,501.00 158.87 109.00 942.3
GS2 Start to GS2 Shutdown 2393 4908 302.24 2962 59.00 25.240 2515
CUS Start to CUS Shutdown 4926 9787 454 4449.2 18 6.036 4861

If 4 engines clustered and solid booster dropped
Event Start V End V Isp Isp*g Mass Initial Mass Final DeltaV
SBO Cutoff @109s to L40 Shutdown 1450 2392.3 255.20 2,501.00 128.87 88.42 942.3
GS2 Start to GS2 Shutdown 2393 4908 302.24 2962 68.42 27.558 2515
CUS Start to CUS Shutdown 4926 9787 450 4410 20.31 7.31 4861

All these figures of V are from the brochure, the Isps are publicly available , as are the take off mass etc. The rest is just applying the rocket equation. This is as real as it gets. I have shown similar numbers from comparable vehicles and also from basic physics. If anyone else "feels" or "thinks" that it is a 100Kg or 150 Kg, difference, I would like to see the math and reasoning.

Think over it. The 30ton (or 12 ton or whatever) you are lugging is when the vehicle's mass is around 150tons. Thats a huge 10 to 20 % deadweight. If you were to drop the spent stage, you would be accelerating a far lower mass, and retain a higher mass fraction going forward. This is by no means "lower stage", but well into the higher stages where you are carrying deadweight.

Indranil · Post by **Indranil** » 20 Sep 2016 23:39

No more feelings. Time for me to learn.

Varoon Shekhar · Post by **Varoon Shekhar** » 20 Sep 2016 23:45

Any official announcement of the PSLV/Scatsat launch? It was supposed to be on Monday Sept 26th, but no information as yet on the ISRO website.

disha · Post by **disha** » 21 Sep 2016 01:14

Typing from mobile:

Just note: GSLV Mk II & MK III are different & for the later apply boosters as first stage. There is no payload performance penalty with airlit core liquid.

For mk2., treat burnt out 1st stage w/ boosters as additional stage & compare it w/ an equivalent virtual stage with better mass fractions

Will run numbers later.

Glad that we are talking numbers!

Indranil · Post by **Indranil** » 21 Sep 2016 02:23

Just sharing some of the low resolution screenshots of the slides shared by S. Somanath at Aug 2016 . Vina, you might be interested in the talk from 16:15 onwards.

1. Individual parts of SCE 200 have already been tested. Full test of SCE 200 scheduled for next year. First test flight is in single engine configuration by replacing first stage of LVM. This will be the first of a series called HLV capable of lifting upto 6 Tons to GTO

2. Next up, larger solid boosters, and two cryo stages (2 S250+SC200+C30+C25) which will be able to lift up to 10 Tons in geo-transfer orbit.

Note that this is a deviation from the 2 S250+SC200+C50 config that VSSC had shared before. In this config the two cryo stages were clustered instead of being two separate stages

3. Basically, they are saying that when the SCE200 comes on board, they will have the capability to launch anywhere between 4 and 10T to GTO with the different configs.
LVM: 2 S200 + L110 + C25 : 4T
LVM3-SC: 2 S200 + SC160 + C25 : 6T
HLV-1: 2 S250 + SC160 + C25 : 8T
HLV-1: 2 S250 + SC160 + C30 +C25 : 10T

3. Next, by 2024, they want to cluster five SCE 200 engines for the first stage (SC500) of a TSTO. The second stage will be a cryo (C27) stage. The TSTO can lift 6 Tons to orbit and will be India's first man-rated rocket. Another small cryo engine (C5) will be used for the crew escape, and will be tested soon. It will be able to take the crew 2 kms away from the launch site if required. The SCE200 can be reused 15 times.

4. Based on this basic TSTO, they can add strapon boosters for higher payload capacity. Adding two solid S250 boosters will allow 9.4T (?) to GTO. Adding two SC500 stages as boosters would provide 14.3T (?) to GTO or 50T to LEO.

enaiel · Post by **enaiel** » 21 Sep 2016 02:35

That's interesting - I was under the impression that LVM3 would lead to ULV which would lead to HLV and RLV. But there was no mention of ULV in the talk above - or did I miss it? Instead the slides show LVM3 leading directly to HLV. Is ULV dead and replaced by HLV?