Indian Space Program: News & Discussion - Sept 2016

[Lilo]

"The GSLV Mk III rocket weighs 640 tonne with a capacity to carry four tonne satellite. But when one compares the ratio of the GSLV Mk III's weight to its carrying capacity to geo transfer orbit (GTO - where communication satellites will be placed) with rockets of other countries, the former ranks low," an industry expert told on the condition of anonymity.

For instance, Japan's H-IIB rocket weighs 531 tonne but can place an eight tonne rocket in GTO. Similarly, Soyuz, Russia (312 tonne, payload to GTO 3.2 tonne); Falcon, USA (549 tonne, payload to GTO 8.3 tonne) and Proton, Russia (693 tonne, payload to GTO 6.3 tonne); Long March, China (weight 879 tonne, payload to GTO 14 tonne) and Ariane 5, Europe (777 tonne, payload 10.9 tonne).

http://economictimes.indiatimes.com/new ... 178611.cms

While reading up on the news regarding GSLV came across above.
Handy comparisons of the payload fractions of major rocket systems to GTO.

Also some tidbits on the rocket's weight from same article.By one unnamed "industry expert" and two named ISRO experts.

Agreeing that the GSLV Mk III payload to GTO as compared to other rockets is less, G. Ayyappan, Project Director, GSLV Mk III, cited a couple of reasons for it. "From the rocket's propulsion point of view, in foreign rockets, the lower stages (engines at the lower part of the rocket that are fired first to lift the rocket and make it escape earth's gravitational force) are powered by semi-cryogenic or cryogenic engines," Ayyappan said. The thrust power of semi-cryogenic or cryogenic engines are higher than that of engines fired with solid fuel. The GSLV Mk III is a three stage/engine rocket. The core of first stage is fired with solid fuel and its two motors by liquid fuel. The second stage is liquid fuel and the third is the cryogenic engine. "We use solid fuel in the lower stages as it is cheaper than cryogenic fuel. Even other space agencies are looking to use solid fuel to cut costs," ISRO's Liquid Propulsion Systems Centre Director S. Somanath told IANS. "But other space agencies are looking at solid fuel to reduce cost only after their rockets carry far much heavier satellites than Indian rockets," the space industry expert pointed out. ISRO officials said the mass of communication satellites is also coming down and hence India may not need a heavy-lift rocket.
"Nearly 55-60 per cent of a satellite's weight consists of its chemical fuel. Now the idea is to shift to electric propulsion of satellites which would reduce their weight," Ayyappan pointed out. Somanath said: "ISRO started designing GSLV Mk III with four tonne carrying capacity when it was making two tonne satellites. At the global level also the weight of satellites are coming down. It is very difficult to predict the market trends." "Electric propulsion will not drastically reduce the weight of satellites to make much of a difference in the rocket's carrying capacity and it cannot replace chemical fuel. The chemical fuel will be used to take the satellite to its space slot and for managing it later electric propulsion would be used," the expert said."The Chinese government approved the Long March 5 project sometime mid-2000 to have a rocket with a capacity of 14 tonne. The size of communication satellites will have to go up as there is limitation on the orbital slots. It all boils down to planning and also predicting the global trends," the expert added.Citing the example of Japanese H-IIB rocket, Ayyappan said the Japanese use lot of composite materials to make the rocket more efficient and light weight."In future we will also be using more composites in the upper stages instead of metal. Half of the rocket's velocity is achieved only at the upper stage and composite will be the only choice in future," Ayyappan said. "The specific impulse of our cryogenic engine is also slightly less than that of others," Somanath added while listing out other reasons for GSLV Mk III's lower carrying capacity."The aluminium used in some foreign rockets are less dense and their weight is less. We will also use such materials to reduce the weight of our cryogenic stage by 500-600 kg," he said.Somanath said there are plans to reduce the weight of the electronics by around 150 kg so that every kilogram of weight reduced increases the payload capacity. According to him, switching off and restarting of cryogenic stage in the space would also increase the rocket's capacity. Experts said India has to realise its semi-cryogenic stage faster and it can not have the luxury of spending a decade or more in developing newer rocket technologies.

[Ankar]

Only meaningful criteria I see when comparing SLV's are cost/kg to orbit and accuracy of injection into orbit.

[Prithwiraj]

GSAT 17 successfully launched by Ariane 5

[Suraj]

I was hesitating to post my own articles here, but am posting here since they have not been posted earlier. These were blog posts on the Planetary Society blog just before and just after the GSLV-MK3 launch.

Curtain raiser on the launch
http://www.planetary.org/blogs/guest-bl ... eague.html

Post-launch update
http://www.planetary.org/blogs/guest-bl ... ocket.html

Great articles, Sridhar ! Do you have any background on why the GSLV Mk III was called as such, despite being an entirely new creature ? Why didn't they just stick to LVM3 ?

[Gagan]

It was overcast and so ground based cameras could only see so much. But arianespace made up for that with really really slick animation, onboard camera footage in near real time. ISRO's GSLV-3 onboard camera footage is better!
Enjoy!

GSAT-17 launch
https://youtu.be/oiLALQMHg1Q

[Gagan]

Pre launch GSAT-17 video by Arianespace

https://youtu.be/QuNgifQ2SVQ

[Gagan]

Probably not the correct thread to post this, but one can use time lapse photography to capture Geosats at night

https://petapixel.com/2015/10/07/geosta ... ime-lapse/



Look closely at ALPHASAT, EUTELSAT 16C, ASTRA 2D
BADR 4/5/6 are co located

[SSSalvi]

^^^
Reverse of Astronomical Star tracker.

Simply amazing results by NOT TRACKING!!

And a couple of Low Altitude satellites moving bottom to top as faint traces .. watch carefully .. the streaks are fainter and slightly differently patterned.

[Sridhar]

Suraj,

Thanks. I don't know the rationale for the name switch back to GSLV-MK3 from LVM-3. But that name has largely been discarded and Mark-3 is the short form people within ISRO use in conversation and GSLV-MK3 more formally.

[disha]

Great articles, Sridhar ! Do you have any background on why the GSLV Mk III was called as such, despite being an entirely new creature ? Why didn't they just stick to LVM3 ?

LVM3 was a one-off to test the design of GSLV Mk III minus the Cryo-stage. LVM3 design did not have the canted nose boosters and did not have the ogive nose cone. Further LVM3 was to test the clustered liquid first stage. If you notice., there are only two, so balanced in only one axis. If there is a significant deviation in thrust between the two engines, entire rocket will start doing cartwheels* or spin dancing!

Given that LVM3 is a one off for the final GSLV Mk III.

*Clustering in rocketry is very tough. I have seen several high powered rockets do dangerous cartwheels just because they are misfired by few milliseconds. This is actually a design problem when the rocket designer has not taken into account variable thrust arising out of say misfires.

[Sridhar]

If I understand correctly, you seem to be saying that LVM3is the name of a one-off vehicle used in the LVM3-X/CARE experiment, and was not another name used for the GSLV-MK3 vehicle. That is not accurate. The LVM3 name was used internally as well as for external messaging purposes to refer to the GSLV-MK3 vehicle more generally and not just to the experimental vehicle.

See this ISRO link for instance.
http://www.shar.gov.in/SDSCE/lvm3.jsp

If anything, the use of the name LVM3-X for the experimental rocket suggests that at that time, ISRO was referring to GSLV-MK3 as LVM3, with the -X suffix being used for the sub-orbital experimental test.

I have no idea if this is permanent, but at least in the case of the latest launch, there was no use that I saw of the LVM3 name. Formally, it was always referred to as the GSLV-MK3 and sometimes people informally referred to it as just Mark 3.

Personally, I prefer the LVM3 name - it is a distinct name from the GSLV and requires no clarification (as I had to do in my article) that it is not a derivative or variant of the earlier vehicles. Also, it is easier to sound out (Indians of a certain vintage are familiar with the Mark 1/2/3 etc. names since that was used by the Ambassador car, but outside India, few people know right away that MK3 refers to Mark 3). Or call it something totally different if the concern is that LVM3 is too much like the SLV3 ( - I have heard at least one person express this concern, but the SLV3 is so much ancient history by now that I don't see this concern as being particularly valid).

For instance, one could call this series the HLV (for heavy lift vehicle) - more descriptive and better branding. And as the ULV series evolves, give numbers to the variants - HLV-1, HLV-2 etc. Or even now, if there is a plan for lower powered versions of the ULV for smaller payloads and lower orbits, call this middle of the road GSLV-MK3 as HLV-3. That leaves room for future smaller launchers in the series to be called HLV-1, HLV-2 and higher powered ones with higher numbers. I even wrote to Madhavan Nair when he was Chairman ISRO - even though it may be a trivial point internally, it is non-trivial when it comes to outside messaging and branding - but did not receive a response from his office.

Bottomline - ISRO started using the LVM3 name to refer to GSLV-MK3 at some point. And then reverted to the GSLV-MK3 name. I personally no insights into why the two name changes occurred, and what the future plans are.

[Suraj]

Thanks Sridhar and disha for your responses!

disha, don't Russian rockets use clustered engines as a long time design approach ? They seem to prefer it over single chambered J-2 or even monster F-1 like designs, which required a lot of experiments themselves, to sort out combustion instability within the large chambers.

[Prem]

X-post about Chinese Space program
https://chinaspacereport.com/2016/06/20 ... ing-rd180/
China a step closer to acquiring RD-180

It was first reported in July 2015 that China is interested in buying Russia’s RD-180 dual-combustion chamber 400 t-thrust engines for its future super-heavy-lift launch vehicle, as a source familiar with the situation told Interfax-AVN, possibly referring to the proposed Chang Zheng-9 (CZ-9, Long March 9). The CZ-9 rocket, which is still in its pre-research stage, will be comparable in size and performance to the U.S. Space Launch System (SLS), capable of delivering up to 140,000 kg payload to LEO and up to 50,000 kg payload to Lunar Transit Orbit.However, the RD-180 is only one of the options being considered for the CZ-9’s propulsion. According to China Daily, Academy of Aerospace Propulsion Technology (AAPT) of the China Aerospace Science & Technology Corporation (CASC) consortium is currently developing a 500 t-thrust LOX/Kerosene engine and a 200 t-thrust LOX/LH2 engine that will be used on the future super heavy-lift rocket. It is likely that the RD-180 acquisition will be running in parallel with the indigenous development project, in case one of them fall through.The most capable rocket engine developed by China is the YF-100, which is being used on all three series of the country’s new generation launch vehicles: the CZ-5, CZ-6 and CZ-7. Like the RD-180, the YF-100 is also a stage combustion cycle engine burning the LOX/Kerosene bi-propellant. However, the engine can only produce a maximum thrust of 122 t. The YF-100 has been developed from the technology of the Russian RD-120 engine, examples of which was obtained by China in the 1990s. Development of the YF-100 began in the early 2000s and It took the Chinese space industry over a decade to fully digest the RD-120 technology.Nevertheless, China’s attempt to obtain more powerful rocket engines and develop a super heavy-lift launch vehicle is a reflection of growing ambition in expanding its space programme, which already includes robotic lunar landing and sample return missions by 2018, the construction of a permanent space station in LEO by 2022, and a Mars probe mission around 2021. Once the CZ-9 rocket becomes available, currently speculated to be around 2025, China will possess a launch capability enough to support a manned lunar landing mission, as well as other missions beyond Earth orbit.

[disha]

Thanks Sridhar and disha for your responses!

disha, don't Russian rockets use clustered engines as a long time design approach ? They seem to prefer it over single chambered J-2 or even monster F-1 like designs, which required a lot of experiments themselves, to sort out combustion instability within the large chambers.

I came in to answer Sridhar'jis post but will go with answering yours first (since clustering is a topic I have not mastered on my model rockets ).,

Soviet (or Russians) went for clustered engines since they did not have J-2 or F-1., they had design capabilities but not manufacturing capabilities for creating single chambered high thrust engines. They were aware that they will run into combustion instabilities and they (Glushko) also recognized the fact that they just did not have the computational power or budget or industrial strength to do development & testing.

The only way they could get around it given the industrial base of Soviets in 50s and 60s was to cluster engines together. So clustering was a workaround to their problems of large chamber engines. And once a engine design is successful, it gets reused. Several times over as its issues worked out over time. For example the RD-170 is a very successful clustered engine (and our own Vikas is a successful engine where all its kinks have been worked out over 2.5 decades). Soviets compensated their lack of large chambered engines by burning their engines hot., that is go after staged combustion and wring out efficiencies from there.

The classic case of their reliance on clustering is the N-1 Rocket. All four of them failed. And they did not have budget to put it on test stand to understand the anomalies., but more importantly it was clustered around semi-cryo N-15 engines. Another reason why they stuck with N-15 and its derivatives (till RD-170 came about) was because the soviet had very bad oil refining capacity., their "rocket fuel" was very sooty and that would play havoc with their engines leaving soot deposits in their regeneratively cooled nozzles. Hence restarts of an engine was a scary proposition.

Now here is the intriguing part., the soviet Energia rocket was costly and cancelled., part of the cost was that the soviets did not have a good SRB technology that allowed them to launch Energia cheaply.

Here interestingly the chinese followed the soviet path and lately realized that SRBs are a very cheap high thrust reliable options that they have started working on it now!

[disha]

X-post about Chinese Space program
https://chinaspacereport.com/2016/06/20 ... ing-rd180/
China a step closer to acquiring RD-180

So what happened to their much vaunted engine development? I am surprised that they could not go beyond YF-100 which itself is a derivative of Russian RD-120.

I think with this news., I am surmising that Chinese launch options are going to be in doldrums in a decade or two., imagine your future super-heavy rocket is based on a RD-170 (derived into RD-180) which was designed by the Soviets in 80s.

[vina]

Thanks Sridhar and disha for your responses!

disha, don't Russian rockets use clustered engines as a long time design approach ? They seem to prefer it over single chambered J-2 or even monster F-1 like designs, which required a lot of experiments themselves, to sort out combustion instability within the large chambers.

1. What is "clustering" ? When you tie 4 liquid engines (and a solid core) together like in GSLV Mk2 , is it clustering ? If not , why not ?
2. Are the Russian engines like RD-180 "clustered" ?

Clustering, Russian & American F1 etc , might help.

To say ISRO has not "clustered" engines and that the first time it was done was in the L110 stage in GSLV MKIII is a misnomer.

Soyuz has core (with multiple chambers) and 4 "boosters" . But is the core itself "clustered" ? Don't think so.

[Sridhar]

Vina,

Correct me if my understanding is wrong. But in my understanding, a clustered stage configuration involves two or more thrust chambers but shared propellant tanks and turbines. The Soviet clustered stages involved this - their main issue was sustaining stable combustion in a larger thrust chamber and Glushko solved it by having a cluster of separate combustion chambers but gaining from the lower weight of shared propellant tanks and turbo pumps rather than separate ones.

If this definition of a clustered stage is correct, the L110 is ISRO's first clustered configuration (though DRDO has previously used it successfully at a much smaller scale on the Prithvi missile).

[vina]

The classic case of their reliance on clustering is the N-1 Rocket. All four of them failed. And they did not have budget to put it on test stand to understand the anomalies., but more importantly it was clustered around semi-cryo N-15 engines. Another reason why they stuck with N-15 and its derivatives (till RD-170 came about) was because the soviet had very bad oil refining capacity., their "rocket fuel" was very sooty and that would play havoc with their engines leaving soot deposits in their regeneratively cooled nozzles. Hence restarts of an engine was a scary proposition

As always, there are FACTS and Fiction Writing. The post above (not just the snippet I posted and copied above) should be shelved "firmly" in the section labeled "Fiction Writing"

Facts .
1. The N15 (later relabelled as The NK33 designed by the aircraft engine guys, Kuznetsov and not the traditional rocket engine guys.. probably the reason for the radical design) NK-33 was an Oxygen Rich - staged combustion design.
2. Oxygen rich combustion does not LEAVE soot or gummy residues in the lines.
3. For cooling channels, Soviets had the required RP1 fuel back in the 50s. In fact, Soyuz, directly descends from the R-7 Semyorka Ballistic Missile and the RD-107 engines (both in R-7 and Soyuz) run on RP1 Kerosene - LOX , which go back to 1950s!
There is an entire documentary (on Nat Geo I think) I saw on the NK-33 engines and how US acquired them, which is now available on Youtube.

Engines that came in from the cold

[vina]

But in my understanding, a clustered stage configuration involves two or more thrust chambers but shared propellant tanks and turbines. .

So how do you considered the Space X Falcon 1st stage (and indeed the Saturn V 1st stage and the Ariane 4 1st stage, LM 3/4 1st stage) as "clustered" (per your understanding) ?

[Sridhar]

Like I said, I am happy to be corrected. I am actually not sure but in the L-110, the turbopumps are not shared but the propellant tanks are. By that definition, its the shared propellant tanks and not turbo pumps that matters. Or would two separate boosters operating simultaneously but independently also be referred to as a cluster - any examples?

In any case, happy to be enlightened on this.

[Sridhar]

Did a quick review of the relevant section of "Modern Engineering for Liquid Propellant Rocket Engines" by Dieter K Hazel and realized that my understanding is not accurate. There are multiple configurations for clustering. For instance, the Saturn-V first stage used not just multiple engines with their own turbo pumps, it also used multiple tanks (though I have not reviewed the drawing to see how they were shared). Will review this and other references more in depth for getting a better understanding of the issue.

[negi]

There are many stories around Ru's decisions on 1st stage motors, differences between Korolev and Glusko being one among many where former was against usage of hypergolic fuels and latter was allegedly apprehensive about suitability of LH2 as fuel. LO2-RP1 was the only point of convergence for 1st stage engines.

I think the discussion is largely about 1st stage engines as in the upper stages everyone universally uses LH2-LO2 engines (even RU had made upper stage LH2-Lo2 engines in 60s) and whether you opt for a fuel rich or oxidizer cycle you do not run any risk of leaving a soot as there is no carbon in the cycle .

Once it was decided to use LO2-RP1 in the first stage the benchmark to be achieved was the F-1 engine now since Russians never got around solving or at least never bothered to solve the issues around instabilities involved in large chambered engines they opted for a system where smaller chambers in a cluster could together deliver similar if not more thrust than a single large chamber while sharing the turbo-machinery my reading is this would have costed them in terms of efficiency and hence they had to opt for a staged combustion cycle and when you opt for a stage combustion cycle with a fuel- oxidizer combination where fuel contains carbon they had to go with oxygen rich cycle I do not think they had any choice , I mean if you look at any engine that employs staged combustion today and burns a fuel-oxidizer combination where fuel is not LH2 then all such engines have to employ oxidizer rich cycle it's pretty obvious.

Americans never made any staged combustion engines that employ LO2 and RP1 my reading is simply because they got their numbers from a simpler gas generator cycle as they were able to achieve a working large chambered design .

I think all new entrants like Blue origin and several others who want to achieve re-usability are having to employ liquid propellants and hence they all are also using staged combustion engines that employ oxidizer rich cycle in 1st stages because no one uses LH2 as fuel for 1st stages as it is not a right fit and all other fuels do not burn 'clean'.

[rahulm]

No rocket scientist. Taking an analogy from DOO, wouldn't clustering be like parallel processing where computers are clustered to work together ?

In such a case, the architecture and internals of the individual clustered machines could be different as long as both machines work together as desired.

In the case of rocket engine clustering, then, should it really matter if they shared pumps and tanks or not as long as the cluster delivers desired performance ?

Genuine question onlee.

[Sridhar]

Have never seen two boosters operating in parallel being referred to as a clustered design. But others know more than me, and I am refreshing my understanding of this.

[negi]

My understanding on topic of clustering in rocket world is it is a rather 'loosely' defined term in the sense that if you have a rocket such that it has 'n' stages (I assume we have a fair understanding of what a stage is ) and then if a stage itself consists of multiple engines then that stage is said to be clustered so Saturn V first 'stage' consists of a 'cluster' of engines . However when you look at RD-170 which is a single engine it is a cluster of actually 4 chambers and nozzles that share common turbo-machinery and propellant tank so that is why I believe word clustering was used with it's scope limited to engine in this case. At least that is how I explained to myself

[negi]

Have never seen two boosters operating in parallel being referred to as a clustered design. But others know more than me, and I am refreshing my understanding of this.

I believe rightly so because they may or may not be ignited with main stage but separated independently from the stage that they are attached to .

[rahulm]

Hmmm. The strap ons fire and work together but are never defined as a cluster but the strap ons are solid.

[Sridhar]

GSLV-MK1/2 have liquid strap on boosters.

[ldev]

I think all new entrants like Blue origin and several others who want to achieve re-usability are having to employ liquid propellants and hence they all are also using staged combustion engines that employ oxidizer rich cycle in 1st stages because no one uses LH2 as fuel for 1st stages as it is not a right fit and all other fuels do not burn 'clean'.

The Delta IV Heavy which in it's current configuration is the highest payload launcher in the world and which launches 28 tons plus to LEO uses LH2/LOX in both stages including the first stage and two common booster cores. Intuitively it does not look optimal, but hey, they make it work quite flawlessly.

[Neela]

My assumption is rocket clustering, irrespective of whether tanks, turbo pumps, combustion chamber, is shared or not , is when these components belong to the _same_ stage.

[ldev]

True engine clustering as illustrated by this Falcon 9 first stage with 9 Merlin 1D engines without the shroud:



and the benefits of 9 smaller engines illustrated in this Falcon 9 flight when 79 seconds into flight 1 of the 9 engines failed. Flight computers re-calculated the ascent profile and the launch continued with the remaining 8 engines to deliver that payload to the ISS:

[vina]

GSLV-MK1/2 have liquid strap on boosters.

We are quibbling over semantics here, but here is how I think of it.

Booster rockets - Generally rockets that have a smaller burn time than a sustainer /core engine and fall off (staged) when they are done giving the "boost"

Cluster : - Multiple individual rocket motors working in parallel (to increase total thrust and also in case a single/few engine fails remaining engines have thrust reserves to allow mission success). So corollary of this.
1. Cluster rockets engines are not "dropped" /"staged" . They are all dropped as a single stage together (and all engines usually start and stop together)
2. You can start and stop an individual engine in a cluster independently of the other. An RD-180 like engine (shared turbo machinery and gas generator, multiple nozzles), is NOT a true cluster. It is a single engine in reality. If the shared turbo machinery/gas generator fails, the engine is kaput (unlike in a true cluster)

Now watch this video between 0.10 and 0.20


Does the rockets attached externally to the "core" resemble "boosters" or do they resemble "cluster" (rockets working in parallel and the entire set of rockets falling off together once expended)

I would describe the GS1 stage of GSLV MkII as "liquid rockets, externally mounted to a solid core, forming a cluster" . Think of it, if hypothetically there is a burkha/"shroud"/casing that encloses the external rockets and the core in GS1 (not that the shroud will add any value and indeed will just increase dead weight), what would you describe the GS1 as ?

[disha]

My assumption is rocket clustering, irrespective of whether tanks, turbo pumps, combustion chamber, is shared or not , is when these components belong to the _same_ stage.

Clustered engines vs. clustered stages. It is easy to get confused on clustering and some people purposely add to that confusion.

An example of clustered engine is RD-170. Shares the tanks and turbo pump etc.

Take any of the boosted rockets, they are either clustered stages or strap ons.

GSLV Mk-III has both clustered engine (the L110 liquid engines*) and clustered stage (the side boosters)., but the side boosters are referred as boosters since that is what they do., boost the core high up.

And the last one is clustered engines combined into a single stage. Share the same tank but different turbo pumps.

*It will be interesting to know details of the L110 designs. However it has to be public information and not some chaiwallah., since some of this designs need to be closely guarded secrets!

[disha]

Oxygen rich combustion does not LEAVE soot or gummy residues in the lines.

^Bad & Bellicose.

How will one do "Oxygen rich combustion" In the lines of the regeneratively cooled nozzles?

====

Combustion happens in combustion chamber., oxygen rich or not. Not in the lines of the regeneratively cooled nozzles - and neither in any lines.

Regeneratively cooled nozzles are nozzles where the fuel either LOH or Kerosene (based on cryo or semi-cryo) is "piped" around the nozzles to cool them. The "piping" is either "pipe lines" or tubes or channels around the nozzles.

Due to the extreme heat of the nozzle., the Kerosene disassociates and forms a layer of soot in the lines around the regeneratively cooled nozzles (the nozzles are hot and if they are not cooled they will develop fractures and may blow apart).

The kind of soot formed depends upon the formulation of Kerosene.

[SSSalvi]

I don't know .. it could have been posted earlier .. still posting a 'open heart' failure analysis disclosure

http://www.frontline.in/cover-story/gsl ... 596588.ece

If you look at the PSLV’s first flight, which failed, when we did the simulation on the ground, there was a wild point even at that time. Only one out of some 1,000-plus simulations, but it was taken as a wild point and ignored. So the lesson that we learnt is that wild points are not to be ignored but to be studied. They are an indication of something else that is happening.
.....
In F06, it was an inspection problem. The cryo-stage shroud, which is expected to move a little bit during the vehicle movement, is supposed to be provided with a lanyard of about 15 mm. But it was almost not there. It was only about 1-2 mm, resulting in greater tension. Two connectors are provided. But both connectors came out. And then we lost the signal from top to bottom.
.....
In [GSLV-F02], ... A dimension was not inspected during the manufacturing process. When that component was tested, a deviation was seen but that was taken as a wild point, something to do with the facility. It was too abnormal because we got a flow rate almost nine times what was expected. It was an annular gap which was supposed to be 0.5 mm. Something which was to be 17 mm was made 16 mm, and because of this dimensional change, what was to be 0.5 mm became 1.5 mm, hence the flow rate.

[disha]

Bottomline - ISRO started using the LVM3 name to refer to GSLV-MK3 at some point. And then reverted to the GSLV-MK3 name. I personally no insights into why the two name changes occurred, and what the future plans are.

Sridhar'ji., to put it delicately., you came in during the time of LVM3 and when GSLV-Mk3 was referred to it as such you assumed that LVM3 is now called GSLVM3.

Here is some clarification on nomenclatures before we go into details:

LV -> Launch Vehicle
Thus: SLV, PSLV, GSLV. The last two viz. PSLV and GSLV primarily purpose the LV for Polar or Geo Sat launch.

LVM3 -> Launch Vehicle M(ark) 3.
LVM3X -> Launch Vehicle M(ark) 3 Experimental.

GSLV Mk 3 was referred to as GSLV M3 or gsLVM3 or GSLV Mk III from its very initiation of design in 2002/2003..

Here are the references:

1. From the Frontline article http://www.frontline.in/science-and-tec ... 731133.ece

“TOWARDS Sustained Self-reliance in Accessing Space” announced a huge poster on a wall in the cabin of S. Ramakrishan, the first Project Director of the Geosynchronous Satellite Launch Vehicle–Mark III (GSLV-MkIII). It was October 2002 and only five months earlier, in May, the Central government had approved the development of the GSLV-MkIII. Frontline was visiting the Vikram Sarabhai Space Centre (VSSC) in Thiruvananthapuram, on whose vast campus was situated, by the seashore at Thumba, a small building that housed Ramakrishnan’s cabin on the ground floor where the GSLV-MkIII project was taking shape. The massive vehicle, as I saw in the poster, was called “gsLVM3”, or launch vehicle Mark 3, India’s “Next Generation Launch Vehicle”.

2. From the book : Yearbook on Space Policy 2006/2007: New Impetus for Europe., Section 2.4 India Page 89

Indian leadership including President Abdul Kalam, one of India's space pioneers, has been supportive of its space programme and has even increased its financial support to space activities. In particular, ISRO's budget for the 2006/2007 fiscal year, fiscal year, funds have been allocated to the development of a new vehicle (GSLV Mk3) that will be able to lift the planned 4-ton satellites to geostationary transfer orbit (GTO) and 10-ton into LEO...

Bottomline: GSLV Mk III was called as such before the LVM3 was sent up as LVM3-X-CARE to qualify the L110 clustered engine and the Crew module Atmospheric Re-entry Experiment as a one-off.

%\%\%

Coming to your point on branding., you do have some valid points. We may have our preferences and ISRO may have its own reasons.

However., I would prefer that ISRO stick to dry naming like SLV or PSLV or GSLV and mk1 or mkII or mk III. Basically anybody in the entire org does not have to do mental calisthenics to determine what one has in mind when one refers it in design discussion. This is important for engineering divisions., a proper nomenclature where everybody easily cottons on.

Take the reverse example of Kaveri or Kabini. The Kaveri-9 block (or is it Kabini) is now refered to as K-9 and transliterated to "canine" as in a dog. That is the mental picture I get from a river or its tributary down to that of a dog. I do not like it.

Regarding branding., we live in interesting times. 10 years back I pointed out that India is becoming a leader in space., I was laughed out. Point is, the technological progress is tremendous and also the information about it is shared wide. That is why you will always have some gentleperson who will not be able to discern the complexities of a rocket and will blame the designers and engineers and project managers on various things including naming.

[vina]

Oxygen rich combustion does not LEAVE soot or gummy residues in the lines.

^Bad & Bellicose.

How will one do "Oxygen rich combustion" In the lines of the regeneratively cooled nozzles?

Ah. Perfect, and in line with exactly the kind of ridiculous fiction writing and myth making on display by you here. You ask a nonsensical question (on the lines of Why Haven't You Beaten Your Wife Today ?) and frame it as if someone else asked that question.

Combustion happens in combustion chamber., oxygen rich or not. Not in the lines of the regeneratively cooled nozzles - and neither in any lines.

There. Further examples of such random trolling couched as "knowledge" on display as followup on the "Why haven't you beaten your wife today ?"

For the benefit of other folks here, let me take a minute to explain what is happening , in liquid engines (specifically RP1/LOX)

1. The first "combustion" happens in the pre-burner ( "small" amounts lOX and fuel are tapped burned) and which generates the hot gases that these products are used to drive the turbine(s) which in turn pump the gargantuan amounts of LOX and Fuel to the main combustion chamber where they are burnt and expanded through the nozzle, driving the rocket forward.

2. In staged combustion cycle, the exhaust gases from the turbine are piped back into the main combustion chamber (where there huge amounts of fuel and lox are being pumped into by the turbo pumps) and expanded in through the nozzle along with the rest of the main combustion. In an open cycle, the exhaust from the turbine is just vented overboard and NOT piped into the main combustion chamber.

3. Staged combustion is more efficient than the gas generator cycle, because the combustion that is happening in the "pre burner" is NOT wasted (i.e. vented overboard), but is used to generate thrust, as all the gases are expanded through the nozzle . The difference is an order of 5% to 7% extra thrust in the staged combustion for the same amount of fuel and propellant. This is SIGNIFICANT (i.e. a 5% tsfc is big and translates into a big difference, if a competing aero engine had a 5% higher tsfc, the difference in range in payload in a same plane with a different engine will be huge)

4. Fuel rich or Oxygen Rich as the engine is called may be is in the PRE BURNER and NOT Main combustion chamber . So what is happening here is that in the pre burner, the fuel is burnt with higher than Stochiometric Ratio of either fuel (for fuel rich) or oxygen for (oxygen rich) ,resulting in oxygen rich gas or fuel rich gas coming out of the pre-burner to drive the turbine

5. Staged Combustion with RP1/LOX needs oxygen rich gas to be generated in the pre burner, because it is used to drive the turbine and then piped into the main combustion chamber through tubing. You need a clean gas. In a fuel rich gas, the combustion products of RP1/LOX are sooty, have gummy deposits from dissociated RP1 (check out the old Primus /Nutan kerosene stove around the burners) and you can't have that when you carrying that around in tubing. Another question, why not burn an exact stochiometric ratio in the pre burner ? The answer to that (if folks refer to the sermons of Mullah Enqyoob ud Din-e-Gas Turbine and discussions with him) is the flame temperature will be so high that whatever exotic ding-dong material you put behind that flame in the turbine will be a molten lump in seconds. So you need the excess oxygen there and burn the fuel fully so that there is nothing to gum up the lines further down.

Regeneratively cooled nozzles are nozzles where the fuel either LOH or Kerosene (based on cryo or semi-cryo) is "piped" around the nozzles to cool them. The "piping" is either "pipe lines" or tubes or channels around the nozzles..

The kerosene for this has been existence since at least 1950 . The first satellite put in space by man used that to get there. The first dog in space used it to get there.The first man to space used it to get there, the first woman in space used it to get there. That really knocks the bottom out of "Soviets didn't have the kerosene for this until much later" fiction writing of yours. Of course, if the agenda is to obfuscate combustion in the pre burner and carrying that around with cooling in nozzle channels, sure , par for the course I guess.

[Neela]

Vina-ji .Neat simple explanation.
Another point about the staged combustion cycle. The Preburner-turbine exhaust is fed to the main combustion chamber. That means there will back-pressure from main combustion chamber to the turbine. What precautions must be taken here ?

[Sridhar]

Vina,

Thanks for your post about clustering.

You are right - the MK1/2 strapons are not really boosters in the sense of being jettisoned while the core stage continues burning. It's a weird configuration where the strapons burn longer than the core stage and carry the dead weight of the burned out core stage. I wonder how much payload loss results due to this carrying of dead weight for almost a whole minute.

Disha - you are assuming that I am not familiar with the entire history of the vehicle or of ISRO. If you see carefully in my post, I refer to two name changes. First from GSLV-MK3 to LVM3 and then back again to the original name. When I first wrote to the then Chairman Madhavan Nair, it was in the pre-LVM3 name phase. I posted that letter on this forum at that time, as far as I remember.

In any case, the name is a relatively minor point.

[ldev]

Vina-ji .Neat simple explanation.
Another point about the staged combustion cycle. The Preburner-turbine exhaust is fed to the main combustion chamber. That means there will back-pressure from main combustion chamber to the turbine. What precautions must be taken here ?

This video explains how the full flow staged combustion cycle solves the back-pressure problem. Watch from roughly 10:30 for that specific answer, although the full video is also very useful.