Indian Space Program: News & Discussion - Sept 2016

Gagan · Post by **Gagan** » 21 Sep 2016 03:48

2024! That is 8 years from now!

Goosebumps onlee!!!

disha · Post by **disha** » 21 Sep 2016 04:56

Enail., anything after GSLV3 is plug & play. That is ULV is a virtual rocket. Please read previous pages.

disha · Post by **disha** » 21 Sep 2016 05:10

just want to highlight the reliance on solid rocket boosters...

indranilroy wrote: 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

Glad that ISRO is looking at maintaining their lead on solid rocket boosters

SSSalvi · Post by **SSSalvi** » 21 Sep 2016 10:41

PSLV C35 next week 26th, 0912 AM.
SCATSAT release after 17 minutes.
( Next is MY interpretation, not official )
4th stage reignition planned in 2nd orbit visibility after about 100 minutes to place last satellite in orbit at a lower orbit when the satellite is on other side of globe.
There seems to be following sats : SCATSat-1,Pathfinder-1, PiSAT, CanX-7, Pratham, Alsat-1N, Alsat-1B, Alsat-2B

Source: http://epaper.deccanchronicle.com/artic ... id=6360981

======================================

Possible path based on NOTAM issued for the event.

Notice that the warning has been issued almost upto South pole. ( Due to 2nd burn of SP4 ?? )

SSSalvi · Post by **SSSalvi** » 21 Sep 2016 12:40

Graphic pertaining to a stale subject.

A comparison of PSLV launching to a GTO with a GSLV.

Speed profile against altitude is drawn.. Notice that both flights impart same performance upto end of 2nd stage.
Then PSLV is slow in acceleration and it attains orbital velocity ( about 10 kms/sec ) only at 600 kms whereas GSLV reaches to that speed at 200 kms altitude itself.

3 lines on left show SHAR and the perigee points for 2 sats.

amit · Post by **amit** » 21 Sep 2016 14:09

For those who lament, ISRO's very SDRE driven cautious approach, here's a perspective of what happens when you suddenly become uber TFTA

China's Tiangong-1 space station 'out of control' and will crash to Earth

However, speaking at a satellite launch centre in the Gobi Desert last week officials said the unmanned module had now “comprehensively fulfilled its historical mission” and was set to re-enter the earth’s atmosphere at some point in the second half of 2017.

“Based on our calculation and analysis, most parts of the space lab will burn up during falling,” the deputy director of China’s manned space engineering office, Wu Ping, was quoted as saying by official news agency Xinhua.

The announcement appeared to confirm months of speculation that China had lost control of the 10.4m-long module after it suffered some kind of technical or mechanical failure.

Jonathan McDowell, renowned Harvard astrophysicist and space industry enthusiast, said the announcement suggested China had lost control of the station and that it would re-enter the Earth’s atmosphere “naturally.”

If this is the case, it would be impossible to predict where the debris from the space station will land.

nirav · Post by **nirav** » 21 Sep 2016 16:03

Vina,

I think you are having a severe case of brochuritis.

ISRO has had a long arduous journey with the GSLV and its after all these years they finally have a *reliable* launch vehicle.

The thing to note here is, the configuration, which includes the "lugging" of the S139 was chosen way back.
The decision then was taken based on a multitude of variables and represents a mix of optimised configuration taking into account variables of core competency,available technology,funds,mission objectives,timelines and a few others in the mix.

Now you keep going on and on about "inefficiency" about the S139s lugging.
As per your revised calcs, it might be able to lift some extra ~ 500 KGs to GTO.

If you hear the speeches of the gentlemen post the launch, they managed to hike payload capacity by about 100 KGs in this very launch.

so do you really think changing the configuration at this stage is absolutely necessary for another 400 KGs increase in payload ?

Its about the opportunity cost for that.Now that they have got it reliable, their focus is on increasing manufacturing speed and launching ability per year. Uber ISP values and payload capacity values mean crap if you cant regularly and reliably launch the rockets.

Id like to say one last thing.

THERE IS NO GOLDEN RULE in modern rocketry.
Because the americans or chinese do it, doesnt mean we have to do it.
Our Rocket program is unique and caters to our own needs while keeping in mind various constraints faced by us.

vina · Post by **vina** » 21 Sep 2016 16:47

As an update to my earlier post, there is now clarity on another thing.

The empty mass of the S139 stage is 27 TONS, as per this GSLV D1 specs from VSSC . So what the 4 liquid L40 stages is lugging is 27 tons for nearly 45 seconds . So the details I worked out in terms of loss of throw weight penalty in my "Correctly Configured Case" is 1.23 tons and upwards.

The 1.23 tons is a underestimate. How ? Because, the moment the stage is discarded, the remaining velocity gets a momentum boost (due to law of conservation of momentum) and also the heat shield is not discarded as well (and that will get an additional boost) . I have not considered those two as well because as a first approximation, they can be ignored, and we don't need to get into that kind of granularity. Safe to say, it seems like 1.4 to 1.5 tons is what is the payload to GTO loss and a "correctly configured" GSLV , with the exact same components will be able to put 4 Tons to GTO.

That begs the question, why at all did they develop this brand new LVM3 , while a far easier "fix" was available.

vina · Post by **vina** » 21 Sep 2016 17:04

indranilroy wrote:Just sharing some of the low resolution screenshots of the slides shared by S. Somanath at Aug 2016

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

The trouble with the LVM3 / GSLV3 is that it is a STUNNINGLY inefficient rocket, probably the most inefficient in this day and age of in service rockets. If the GSLV MK2 is inefficient (for the tech it contains) because of it's layout of lugging close to 30 tons for nearly 45 seconds, the LVM3/GSLV3 beats the MK2 in inefficiency, and that takes some doing.

How so ? Well, it burns gargantuan amounts of low Isp solids as the 1st stage /zero stage . All other vehicles with large solid stages (Ariane V and the Space Shuttle) have a powerful cryogenic stage that is active at liftoff, so the average Isp will be sort of okay and you have reasonably efficient vehicles. Not so with LVM3 /GSLV MK3.

The LVM3 layout should be scrapped and the components got from it, the CE20 engine , the S200 repositioned . The L110 must be fully changed to 4M dia, 2 * 2MN Kerosene/Lox stage using , the stage lengthened to burn for around 260 seconds or so, and lit at the ground. This should be ULV/ Common Core. That way, you can get a 2.5 T to 10 ton GTO capability, by mixing the CE 7.5 and CE 20 cryo and with no booster, S139 and S200 boosters combos along with the ULV core.

The replace meant of the Vikas engines with a SINGLE 2MN kerosene and lighting it mid air is terribly wasteful and guarantees that this will continue to be the least efficient launch vehicle among the contemporary ones that it will be flying with.

disha · Post by **disha** » 21 Sep 2016 21:55

vina wrote: The replace meant of the Vikas engines with a SINGLE 2MN kerosene and lighting it mid air is terribly wasteful and guarantees that this will continue to be the least efficient launch vehicle among the contemporary ones that it will be flying with.

The above bolded part is utterly wrong and goes against basic understanding of science. Further there is utter disregard to the actual launch sequence of GSLV Mk III.

On GSLV MkIII it has been stated repeatedly that once the thrust from the solid state boosters fall off., the liquid core is ignited. Just because the boosters are on the side and are called 'boosters' they do not become something different and are to be considered as first stage. The core liquid stage becomes the second stage and so on... Here the 'boosters' are hung on the side and not in tandem.

Making bellicose statements about 'terribly wasteful and inefficiency' does not make it so. So please keep your rhetoric and your bellicosity out. It does appear that you got rejected from ISRO and has a personal axe to grind.

And again for measuring rocket efficiency., only set that you are using is payload! And that too comparing payload with a another space agency on the North-East which does not even publish its launches leave alone trusting its payload capacity!

--

Coming back to your calculations for GSLV MkII., there are several errors and mis-assumptions you are making which need to be corrected while somebody else has the onus to present a cleaner set of numbers. I was glad that the discussions was going towards numbers at the very least.

disha · Post by **disha** » 21 Sep 2016 22:10

vina wrote:
The empty mass of the S139 stage is 27 TONS, as per this GSLV D1 specs from VSSC . So what the 4 liquid L40 stages is lugging is 27 tons for nearly 45 seconds . So the details I worked out in terms of loss of throw weight penalty in my "Correctly Configured Case" is 1.23 tons and upwards.

This is classic case of selectively pulling 'data' to prove a particular point!

1. The number quoted above is for GSLV D1 MkI (since retired) where ISRO was on record to say that it has underloaded the propellant mass. In the above case., the propellant loading is @129 tonnes.

2. And here is the link for GSLV F05 MkII which is currently operational http://www.isro.gov.in/sites/default/fi ... -final.pdf and check the propellant loading. It is @138 tonnes.

There is a reason why ISRO calls it S139/S140 solid booster stage!

Indranil · Post by **Indranil** » 22 Sep 2016 00:01

I have to agree with you Vina. However, I do not know enough of the science in play here to ascertain the correctness of your calculations. If you look at it from the mass fraction point of view, GSLV is inefficient. But from the dollar fraction point of view, it is not. ISRO like all our govt. entities have taken the safest cheapest route to get where they are today.

Now, coming to the LVM3, I don't think that you are vieing it for what it is. It is not our next generation of launchers. It is actually the test vehicle for our next generation of launchers, aka the HLV. HLV will require completely new set of constituent engines than PSLV/GSLV. The GSLV engines can take us to at most 4 Tons (if you are correct), but not much more. Now, the components needed for HLV are:
1. Higher thrust liquid engines for core stage
2. Cluster of above engines for core stage
3. Higher thrust cryo stage
4. large solid/liquid boosters

Unfortunately, the order in which these components are ready is 4, 3, 1, 2. 4 has been flight tested once, 3 will be flight tested soon, 2 has finished components testing and will be ready in two years, 4 will arrive by 2024. So, what do they do in the interim? In classic SDRE style, they have come up with a test-cum-launch vehicle, aka LVM3. It will incrementally incorporate the components as they become available. When 4 was being tested, they could not put a satellite in space, so they tested the human crew recovery module. When 4 and 3 will be available to test in the next flight, they will try to launch a heavy communication satellite. When 1 becomes they will flight test and launch an even heavier, or more number of satellites, and so on. The only thing that they have designed extra for the LVM3 is the L110 stage. And this is lot a complete waste either. It allows them to test and refine parts of 2. I think you should view LVM3 for what it is: a test vehicle which is being used to launch satellites.

enaiel · Post by **enaiel** » 22 Sep 2016 01:06

Disha, I have been following ISRO for years, but I am still confused. ULV was supposed to be a modular rocket that was supposed to replace both PSLV and GSLV for the commercial launch business. HLV was supposed to be for the Human Space Program (HSP). LVM3 was supposed to be the testing ground for future technologies that go in ULV and HLV. But from what Indranil has posted, looks like there is no longer a ULV, only HLV.

disha · Post by **disha** » 22 Sep 2016 02:40

enaiel - See ULV as a "sand box" for HLV., GSLV - Mk III is the foundation. On the basic design., changing components or adding/removing stages will lead to a 'stick' of a rocket to a giant of a rocket. U in ULV stands for 'Universal'., that is it can be your TSTO to SSO or TSTO to GTO or HLV to Direct Injection GEO or with liquid cores your HSP.

---

IndranilRoy'ji can you please clarify on which points you agree with Vina? GSLV MkII design of lugging the spent 1st stage (where to prove his points, Vina pulls numbers from MkI (retd.) ) or GSLV MkIII where core is not fired simultaneously and the claim is that it is inefficient (and you *feel* that it is inefficient?**) or both?

** For a aero guru like you., a weekend reading of staged rocket sciences will give you enough information. For example in a 3+ staged rocket if your stage structure is <5% mass the efficiency gains in discarding spent stages is very minimal and the skew is maintained towards structural integrity! This is counter-intuitive. I do not have the mathematica codes with me currently (was there some 2.5 decades back) to bring out all the graphs and ratios. So have to work on this from a different sphere and station in life which to my own chagrin is a slow go. I would also suggest that go through the recent PDF brochures of PSLV/GSLV. ISRO is calling the Stage+Booster assembly simply as Stage I. I agree with that.

nirav · Post by **nirav** » 22 Sep 2016 05:34

without considering the larger picture of what goes on in deciding a configuration, all this talk of "inefficiency" is nothing but balderdash ..
sole focus is on lower ISP values and oh THAT lugging of the S139 tank !

The thought process behind a keyboard warrior thinking he knows it all and saying GSLV family is "inefficient" a thousand times gives the appearance that he thinks the kind people at ISRO are a bunch of hacks ..

a mirror is needed IMHO.

vina · Post by **vina** » 22 Sep 2016 06:02

If you look at it from the mass fraction point of view, GSLV is inefficient. But from the dollar fraction point of view, it is not.

Are you sure ? I am willing to bet it is NOT. If it is more dollar efficient all the companies operating in a market economy (where it pays to cut costs for a given revenue) like he US would have moved to a large(ly) solid based config and that would include new entrants such as Space X and Blue Origin, more so, when there are existing large solar boosters from other programs like the shuttle!

prasannasimha · Post by **prasannasimha** » 22 Sep 2016 07:19

Energy density also ahs to be considered which is why sold rocket boosters in the atmospheric phase is still used where it is beneficial. Also cryogenic engines have their own issues and frankly when both GSLV and MK3 where designed we did NOT have a cryogenic engine. Everyone cooly forgets that we have just had the first operational flight barely within this month. So how on earth where we able to go around designing without a viable engine with no backup program in case of failure ?

symontk · Post by **symontk** » 22 Sep 2016 10:26

vina wrote:As an update to my earlier post, there is now clarity on another thing.

The empty mass of the S139 stage is 27 TONS, as per this GSLV D1 specs from VSSC . So what the 4 liquid L40 stages is lugging is 27 tons for nearly 45 seconds . So the details I worked out in terms of loss of throw weight penalty in my "Correctly Configured Case" is 1.23 tons and upwards.

The 1.23 tons is a underestimate. How ? Because, the moment the stage is discarded, the remaining velocity gets a momentum boost (due to law of conservation of momentum) and also the heat shield is not discarded as well (and that will get an additional boost) . I have not considered those two as well because as a first approximation, they can be ignored, and we don't need to get into that kind of granularity. Safe to say, it seems like 1.4 to 1.5 tons is what is the payload to GTO loss and a "correctly configured" GSLV , with the exact same components will be able to put 4 Tons to GTO.

That begs the question, why at all did they develop this brand new LVM3 , while a far easier "fix" was available.

So GSLV2 can get 4 tons to GTO, ok now you replace the C12 in GSLV2 with C30 and will it put 6 tons to GTO. Is it possible? think about it?

vina · Post by **vina** » 22 Sep 2016 10:38

Ok. Have time to kill a bit in between meetings and I opened my GSLV Mk2 - Tsialkovsky spreadsheet again and looked at the numbers modelled on the GSLV D6 Mission.

It looks like that the GSLV GS2 stage, though it has a capacity of approx 40 tons of propellant, the spread sheet shows that they loaded only 33.76 tons of propellant. And also, it looks from wiki, that the GSLV Mk1 flew a mission with a propellant loading of 15 tons. From the brochure, the GSLV D6 mission flew with a propellant loading of 12.88 tons. So theoretically, they can fly the vehicle as it exists today with a propellant loading of 2.25 tons more in the cryogenic stage, and also possibly 6 tons more in the GS2 stage.

Fly in the ointment is, it looks like that given the delta V needed for orbit, you cannot simultaneously top up the GS2 tank and the CUS tank. You will be left with extra fuel in the one of the tank stages. So obviously, you will top up the cryogenic stage (as it is most efficient, and you need to accelerate the least mass as it is at the top stage) . Looks like the , max you can do is top up the cryogenic stage, and that gives it a 15 ton propellant loading and you can put in roughly one ton more propellant in the GS2 tank (so that nothing is left behind when the stage is shut down).

With fuel fully topped up as above, the difference in GTO will be 0.6 tons, and given the GSAT 6 satellite was 2117 Kgs, the max throw weight seems to be around 2700Kgs in the current config.

IF the GSLV was "configured ideally" , the extra throw weight would be 0.8tons more (largely because you can top up the GS2 tank to 40 tons) over the equivalent "ideal config" I posted earlier, giving it a total of 1.46 more than the fully topped up "current config" , giving it a total throw weigh of 2700 + 1.46 tons ~ 4 Tons to GTO .., which is what the comparable launchers throw.

Indranil · Post by **Indranil** » 22 Sep 2016 11:00

vina wrote:
If you look at it from the mass fraction point of view, GSLV is inefficient. But from the dollar fraction point of view, it is not.
Are you sure ? I am willing to bet it is NOT. If it is more dollar efficient all the companies operating in a market economy (where it pays to cut costs for a given revenue) like he US would have moved to a large(ly) solid based config and that would include new entrants such as Space X and Blue Origin, more so, when there are existing large solar boosters from other programs like the shuttle!

You have a good point. But from whatever little I have read till now, the cost of solid propellants is supposed to be lower. Also, I have a feeling that the empty mass of the S139 is not 30 tonnes. It should be less than 10% of the initial weight. Let me dig in more on this. Next, I have to understand the math.

Disha, I am not a guru. I just an enthusiast.

I think you and Vina are being so combative, that you are reading past each others' posts. For example, he says L110s are lit midflight, and you write a lengthy explanation of how the L110 stage senses the impending burnout of the solid boosters and ignites itself. You may also want to look at the Long March 3B config with respect to the GSLV. The main difference is the 1st stage and the 3rd stage. The difference in the payload is significant.

vina · Post by **vina** » 22 Sep 2016 11:13

indranilroy wrote:But from whatever little I have read till now, the cost of solid propellants is supposed to be lower.

The cost of liquid propellants is literally next to nothing compared to the overall vehicle cost. LOX is very easily available from industry and so is Kerosene. In fact hypergolic propellants will be more expensive as they will require setting up dedicated plants which will have far lower economy of scale compared to kerosene and LOX.

indranilroy wrote: Also, I have a feeling that the empty mass of the S139 is not 30 tonnes. It should be less than 10% of the initial weight. Let me dig in more on this. Next, I have to understand the math.

Dont "think and feel", look up the link I posted to VSSC of GSLV D1 .Just do arithmetic. There they have the take off weight of the S139 stage's take off weight and the loaded propellant weight. The difference between the two will give you the stage empty weight , which is 27 odd tons iirc (whether they loaded 129 tons or 139 tons is immaterial, what we are calculating is the empty weight)

Also, the Rocket Equation is plug and chug. The delta V of each rocket powered event is got in the GSLV D6 "event table" in the brochure. You have the Isp of each stage, you know the masses , you know the deltas , it is just plugging in to the "formula" , not much thinking required. There are no "trick" questions. All you need to realise is that when the stage is dropped, the mass of the vehicle decreases , and then using the data from the D6 launch, calculating the difference of mass carried to orbit is trivial . You have to apply the rocket equation at each event sequentially ,that is all .

disha · Post by **disha** » 22 Sep 2016 12:48

indranilroy wrote:I think you and Vina are being so combative, that you are reading past each others' posts. For example, he says L110s are lit midflight, and you write a lengthy explanation of how the L110 stage senses the impending burnout of the solid boosters and ignites itself.

Vina's contention is that lighting the L110s mid-flight is inefficient (GSLV Mk3). I am pointing out that L110s of GSLV MkIII act as the second stage., the boosters being the first stage. It does not matter if you put a rocket engine on the side and fire it and call it booster or attach it to the bottom and fire it and call it stage.

I am not contending that it is lit mid-flight. I am contending the assertion that it is inefficient.

You may also want to look at the Long March 3B config with respect to the GSLV. The main difference is the 1st stage and the 3rd stage. The difference in the payload is significant.

One of the problems with Long March 3B is that they do not specify the orbital injection parameters. Several of the GEO sats launched by Chinese LM3 carry almost 2/3rd of their weight in propellants. So one does not know if the rocket is indeed injecting it in the most optimum GTO or in an orbit which would require the sat to wade through to GEO.

Comparing rockets based just on their payload capacity is useless. My major umbrage is that an artificial payload goal is tied down as ideal and then we exorcize ourselves into unable to meet that ideal. Not unlike the size issues some humans face.

disha · Post by **disha** » 22 Sep 2016 13:12

The cost of liquid propellants is literally next to nothing compared to the overall vehicle cost. LOX is very easily available from industry and so is Kerosene. In fact hypergolic propellants will be more expensive as they will require setting up dedicated plants which will have far lower economy of scale compared to kerosene and LOX.

I do agree that in general cost of *all* propellants is next to nothing (in some cases avionics cost more than the entire propellants put together)., again a wild assertion is made that 'kerosene' is cheaper than 'hypergolic propellants'.

The above is another wild assertion and can be ascertained by just pointing out this two facts:

1. ISRO is developing a rocket-fuel grade kerosene called ISROSENE - yes it is a kerosene in the sense that we are all apes. But this is not the average 'ghas-tel' which our moms burnt it in the kitchen. It requires specialized fracking and tough quality controls and the market is limited to ISRO., just a few tonnes a year.

2. One of the hypergolic propellant., HNO4 is a derivative of nitric acid which is made at industrial scale in millions of tonnes as precursor to fertilizer.

So to come back and say that "hypergolic propellants will be more expensive as they will require setting up dedicated plants which will have far lower economy of scale compared to kerosene" is entirely bombastic statement without any basis.

Such statements are very similar in line of bringing in GSLV Mk1 D1 (retired) numbers to prove only a particular point of payload capacity when ISRO itself has moved to GSLV Mk II.

SaiK · Post by **SaiK** » 22 Sep 2016 19:06

http://indianexpress.com/article/techno ... y-3044368/

on Pratham, is this all IIT-B was focused on? I think they can do more on a 1 or 2 ft cube. A mil grade droid device with terrabytes of storage and RAM can load up many apps.

more sensors, more apps, more nano technology. It costs a lot to piggyback, so let us use it judiciously

Indranil · Post by **Indranil** » 22 Sep 2016 23:08

Vina, Disha,

I bow out of this discussion. I have much to learn before I can contribute meaningfully. I find the LVM3 very close to the Ariane 5 configuration.

1. Disha, China may call anything as GTO. Ultimately, I will have to consider the dry mass of the satellites that it launched to GO. for e.g. the drymass of Belintersat-1 launched by China is 2086 kgs, and that of INSAT 3D is 956. The former has a planned life of 15 years while the later has 10. So...
2. Vina, I understand that rocket motion is a matter of math. The problem, is I don't know the exact math. I know if I plug in the same numbers in the same equation that you have pointed to, I am likely to get the same answers. But is that all. The basic formulas that you are pointing to must be known to the ISRO guys too. Then why did they design GSLV Mk2 the way it is?

By the way, I don't know why but ESA designed Ariane 6 PPH as the cheaper alternative to Ariane 6 when launching a single satellite. Guess what, all its stages barring the last are solid state: boosters, first stage, second stage et al.

P.S. Vina, you were right. The inert mass of S139 is 28,300 kgs.

vina · Post by **vina** » 22 Sep 2016 23:14

symontk wrote:So GSLV2 can get 4 tons to GTO, ok now you replace the C12 in GSLV2 with C30 and will it put 6 tons to GTO. Is it possible? think about it?

Excellent question. Since we have the spreadsheet with us, let us not "think" , but actually do the math and find out!

On a broad level, the GSLV MKII has a lift off mass of 415 tons. A well designed and optimised rocket will have a payload mass fraction of between 1% to 1.5% , i.e. a payload between 4tons to 6 Tons GTO.

As I mentioned in my previous posts, the problem with the current version of the GSLV Mk2 is that it lugs around 30 tons without staging , and from the looks of it, it simultaneously can't top the propellant load in the GS2 tanks and in the CUS. It then strikes you the fundamental problem. The "using the PSLV components" to the maximum for the GSLV1/2 has left a hugely under optimised GSLV MK1/2 and the CUS doesnt fix all of it.

I already posted that if "clustered" the lower liquid stages and kept the GS2 and CUS as is ,but topped them to the max with propellants, we get 4 tons to GTO. Is this the "best" solution ?

If we look at the figures, the ISP of the S139 is 2412Ns/g and the L 40 is 2501N/g . The ISP of the lower stage comprising the S139 and the 4 L40s , when they are firing is 2453 NS/g (you calculate that by weight you weight the Thrust of the combined engines by the mass flow rate), which roughly halfway between the Isp of the solid and liquid. So really with a UDMH/N2O4 engine + Solid combo, the ISPs of both are comparable and the solids don't drag down the overall performance.

The killer seems to be devastation the mass fraction suffered by the upper stage in lugging the dead weight and the inability to load the propellants fully for the mass available in the upper stage.

So , let us do this. At S139 burnout, each of the L40 has consumed 30 tons out of the possible 40 tons it can be loaded with. So, let us load just 30 tons in each L40 , so that it's shutdown syncs with the S139 burnout and we immediately DROP the entire stage in one piece like happens currently. At this point, i.e. 109 seconds, the vehicle would have consumed 139 tons + 120 tons, i.e., 159 tons of propellant . Using Tsialkovskly equation, at this point, we calculate the vehicle velocity as 2400 m/s (which by the way is exactly what the velocity , the D6 broacher says is, when the L40s shut down after lugging the dead weight, remember the lift off mass is the same anyways) . Immediately you drop the entire stage which has an inert mass of 50.7 tons (just like it happens today, in one piece) and the vehicle weight drops to 415 - 159 - 50.7 = 105.3 tons only! Let us be cautions and take away 10 more tons (as a measure against uncertainty in ISPs and exactness etc), and keep the vehicle weight at 95 tons only.

The Delta V required for the mission is 9779m/s, so an increment of delta V of 9779 - 2400 = 7379 m/s is needed. Now , let us address the 2nd unoptimised part. The GS2 has a capacity of 40 tons. Let us lengthen the tanks (and the stage) by a bit, so that new GS2 now carries 50 tons of propellant . So at the start of the GS2 burn , the vehicle will weigh 95 tons , and will burn 50 tons of propellant and at the end of the burn will weigh 40 tons. The this burn will give a delta V increment of 2562 m/s. Now since this is an "enhanced" GS2, with larger tanks etc, let us be generous and put an inert mass of 11.5 tons for the stage, vs the existing one of around 7.5 tons and we drop this GS2. The vehicle's weight is now 28.45 tons. The balance delta V required is 4816 m/s. So we plug the starting weight of the vehicle, into the rocket equation, and calculate the end mass of the vehicle when the delta V increment is 4816 as 9.64 tons which is what is available for the balance. The inert weight of CUS is around 3 tons, an adapter and other stuff of around 400 kg, so yeah, it looks ok you can carry a 6 ton satellite in the 9.4 tons mass available at the end of the CUS burn.

So now it seems that the easiest "fix for GSLV MK2" is to load on 3/4 (i.e. 30 tons) of propellant in L40, drop that entire stage at 109 seconds when they burn out along with the S139, enlarge the tanks of GS2 slightly to carry 10 more tons and you are have a 6 ton class vehicle , that is comparable to the LM3B-Extended, which advertises 5500 ton to GTO. Now, of course, this is an estimate, these numbers can be refined if more granular is available and you can model in the Payload Fairing drop, probably go through another design cycle iteration and possibly the overall vehicle mass will come down by 25 to 30 tons etc.

On paper, fixing the GSLV 2 seems far easier than creating a brand new LVM3! Okay, the GS2 tanks need to be enlarged to carry approx 10 more tons, and the CUS probably needs to carry around 18 tons of fuel, it can definitely carry 15 tons, but might need a bit of enlarging as well) I suppose. Now, this is not outrageous, this has actually been realised in comparable vehicles (LM3B, Ariane 4 etc) , passes the 1% to 1.5% overall test and hence passes the smell test!.

Indranil · Post by **Indranil** » 22 Sep 2016 23:28

vina wrote: So , let us do this. At S139 burnout, each of the L40 has consumed 30 tons out of the possible 40 tons it can be loaded with. So, let us load just 30 tons in each L40 , so that it's shutdown syncs with the S139 burnout and we immediately DROP the entire stage in one piece like happens currently. At this point, i.e. 109 seconds, the vehicle would have consumed 139 tons + 120 tons, i.e., 159 tons of propellant . Using Tsialkovskly equation, at this point, we calculate the vehicle velocity as 2400 m/s (which by the way is exactly what the velocity , the D6 broacher says is, when the L40s shut down after lugging the dead weight, remember the lift off mass is the same anyways) .

I was doing a similar exercise of what would happen if I synchronized the burnout of the boosters and the first stage, and the bolded part troubles me. I can't believe that the guys at ISRO are such big dorks that they spend 40 tons of fuel for zero gains!

disha · Post by **disha** » 23 Sep 2016 00:00

There was a query on how Long March 3B is more TFTA etc., and we might be unnecessarily focussing on the GSLV D1 Mk1 (retd.) to prove that how ISRO are such big dorks., when it could be

1. Long March Cryo engine is not 75 kN (as understood from designation YF-75) but could be actually >150 kN
2. And it might be doing multiple burns.

Taken 1 & 2 together., I can think of a shift of 1 to 1.5 Tonne in the throw weight (or payload).

The unnecessary focus on the GSLV D1 Mk1 (retd.) is taking time out of actual valid questions., what is the real performance of the Cryo upper stage of Long March 3B (and its clones)?

The answer is there. If my understanding is correct (as pointed out in item #1 and #2 above)., then we are unnecessarily comparing two different rockets (even though they look the same!).

And that basically means that we are comparing throw weight of a rocket with a CUS of 75-82 kN with a Cryo Upper stage of another rocket with >150 kN and/or multiple burns.

nirav · Post by **nirav** » 23 Sep 2016 04:16

indranilroy wrote:
vina wrote: So , let us do this. At S139 burnout, each of the L40 has consumed 30 tons out of the possible 40 tons it can be loaded with. So, let us load just 30 tons in each L40 , so that it's shutdown syncs with the S139 burnout and we immediately DROP the entire stage in one piece like happens currently. At this point, i.e. 109 seconds, the vehicle would have consumed 139 tons + 120 tons, i.e., 159 tons of propellant . Using Tsialkovskly equation, at this point, we calculate the vehicle velocity as 2400 m/s (which by the way is exactly what the velocity , the D6 broacher says is, when the L40s shut down after lugging the dead weight, remember the lift off mass is the same anyways) .
I was doing a similar exercise of what would happen if I synchronized the burnout of the boosters and the first stage, and the bolded part troubles me. I can't believe that the guys at ISRO are such big dorks that they spend 40 tons of fuel for zero gains!

Seriously ?

Are ISRO guys similar to the dorks at HAL who designed the exhaust of HTT 40 in such a way that would lead to its undercarriage tyres bursting ?

Well wait, that theory was nothing but hot air ..

Whos really the dork ?
Like id said earlier, few guys in here need to look in the mirror.

nirav · Post by **nirav** » 23 Sep 2016 04:25

Id also state a very real truth that no ones saying out loud.

If a person thinks that armed with Tsialkovsklys equation and a "spreadsheet" he can solve for GSLV mk2 to put 6 tons to GTO, then bhaisaab,i must say, aap c****** hai.

I would also like to ask for the record whats their professional background and experience in the rocket business that they are coming up with such magical fixes for the GSLV.

Pray tell the board, which rocket have you designed and worked on.

Indranil · Post by **Indranil** » 23 Sep 2016 05:13

I have left your report to be handled by another moderator. Now, I take my moderator hat off to reply to you.

nirav wrote:
indranilroy wrote: I can't believe that the guys at ISRO are such big dorks that they spend 40 tons of fuel for zero gains!
Seriously ?

Are ISRO guys similar to the dorks at HAL who designed the exhaust of HTT 40 in such a way that would lead to its undercarriage tyres bursting ?

All along, I have been questioning Vina's oversimplification. For example, here's the post just prior to the one you quoted.

indranilroy wrote: 2. Vina, I understand that rocket motion is a matter of math. The problem, is I don't know the exact math. I know if I plug in the same numbers in the same equation that you have pointed to, I am likely to get the same answers. But is that all. The basic formulas that you are pointing to must be known to the ISRO guys too. Then why did they design GSLV Mk2 the way it is?

See, the difference between discussing and arguing is that you can agree with your opponents when he is right. The inert weight of 1st stage is 28.3 tons. When this stage burns out at approx 105 seconds, and the strap ons keep burning for another 50-55 seconds lugging this dead weight. This is obviously suboptimal. I can't argue with these things. Nobody can. Vina is then quantitatively putting a value on how suboptimal this is. I have a problem with that number based on the fact that his calculations show no benefit for an additional 2.8MN of thrust for 50 odd seconds. What he is suggesting are such low hanging fruits, that the ISRO guys couldn't have missed them. The question remains, then what is the gap in our understanding. At least, I have the decency to admit flatly that I don't know. But, like me, you don't know either, but all you bring to the table is fowl language (starring it out does not mean that you are not saying it).

And I say again, I don't believe that the guys at ISRO are such big dorks that they spend 40 tons of fuel for zero gains! If you remove the burden of being offended at the slightest, you might be able to understand what others are writing.

And for the record, I was the first one on this forum who said that there was no problem with the HTT-40 exhausts wrt tyre overheating. The person who raised that question has relevant design experience. Anyways, the ensuing discussion was illuminating. I learnt new things from my "opponents".

nirav wrote: Whos really the dork ?
Like id said earlier, few guys in here need to look in the mirror.

Few guys on this forum should also cool down a little. You see, one doesn't have to wear his/her patriotism on their sleeve and flash it at every possible instance. For example, it is perfectly fine for desi-patriots to question a desi designs. If you can't understand this, in your own words,

nirav wrote: then bhaisaab,i must say, aap c****** hai.

Moderator hat on.

suryag · Post by **suryag** » 23 Sep 2016 08:32

For fundoos(who studied 4-6 books and think they can design better rocket configurations using advanced tools like spreadsheet and brag about their ability to out think someone who has been doing that for over 60 years now) and keyboard rocket designers lacking humility to accept that they know very little about the rationale behind ISRO rocket designs my request to admins is to start a "design your own rocket" thread

Indranil · Post by **Indranil** » 23 Sep 2016 09:26

^^^ That is a good suggestion.

SSSalvi · Post by **SSSalvi** » 23 Sep 2016 09:27

^^^ ^^^ ^^^
^^^ ^^^
^^^
Thanks!!

vina · Post by **vina** » 23 Sep 2016 09:53

Indranil wrote:I was doing a similar exercise of what would happen if I synchronized the burnout of the boosters and the first stage, and the bolded part troubles me. I can't believe that the guys at ISRO are such big dorks that they spend 40 tons of fuel for zero gains!

That part is wrong, and that is why I put it up in my post. While the answer I put up originally on what is the extra throw weight if clustering was done , had picked data out of the flight and so corrected for all errors from "ideal" because ," it is as happens in the real world "and was hence correct. For the answer I put up to SymonTk's question, can the GSLV MKII do 6 Tons to GTO, it is wrong, because I applied the rocket equation in the "ideal case" and did not correct for real world. The delta V at S139 burn out and L40 having burnt 30 out of 40 tons is 1400 m/s as I originally posted earlier and NOT 2400 m/s as I posted last night.

The rocket is still lifting off pretty steeply (though it would pitch over a few seconds immediately after launch), the Gravity Drag would still be high and the atmospheric drag will be high as well and together the penalty in delta V is 942 m/s. The 40 ton of propellants left in the L40 tanks is used to close that penalty and increase speed to 2400m/s at the end of burnout. That is where the 40 tons of fuel are spent.

I will modify my calculations for the Gravity Drag in the lower atmosphere and the early part of the 2nd stage (after that it is a non issue), and put up a modified answer to SymonTk's question.

SSSalvi · Post by **SSSalvi** » 23 Sep 2016 10:39

^^^
I love the DISCUSSION.
It would really be a good idea to have a real thread about design BRF.

symontk · Post by **symontk** » 23 Sep 2016 10:59

vina wrote:
symontk wrote:So GSLV2 can get 4 tons to GTO, ok now you replace the C12 in GSLV2 with C30 and will it put 6 tons to GTO. Is it possible? think about it?
Excellent question. Since we have the spreadsheet with us, let us not "think" , but actually do the math and find out!

Thanks for you to work on that. Regarding L40's in GSLV, they can go to L55 after success of GSLVmk3 since it has L110 for 2 engines. I dont know if ISRO will do that, but that is a suggestion

vina · Post by **vina** » 23 Sep 2016 14:10

Ok . Considered the considered the gravity drag and the other stuff and this is what we have.

1) Current Config - Lugging 28 tons, max possible propellant top up -> GTO max - 2.7 tons
2) Clustered core - No lugging - all other components same, solid staged efficiently on burn up --> GTO max - 4 tons
3) No lugging,core and L40s dropped at 109 s, 2nd stage and booster - enhanced tankage --> GTO Max - 2.96 tons
4) Clustered core with higher propellant loading - 2nd stage and booster -enhanced tanks --> GTO Max - 6 tons

The other thing one needs to consider is that the thrust of the GS2 engine is around 800KN , so that puts a max limit of the weight of the vehicle at 80 tons at the start of GS2 , because, you want to have a T:W ratio of 1 or better at 2nd stage start, as the vehicle is not fully pitched over.

So, now everything is clear. The current config with the S139 at the core is SO inflexible, that other than clustering the core (hence a brand new core stage) and also tweaks to the 2nd and 3rd stage (which will require a higher thrust CUS engine, the current one doesn't have enough thrust to accelerate quickly enough to have the least gravity drag), the current config is at it's limits . A clean design of clustering right from the beginning, could have given an Ariane 4 or LM3B equivalent and served us for the next 5 years.

The "cheapest"/"easiest" possible tweak is no 3. But then , it gives a very minimal advantage over the current config with existing components. So even if you tweak the 2nd and 3rd stage with extra propellants and drop the 1st stage at 109 s, you get very minimal gain, and hence it is not surprising that ISRO kept the PSLV components as is (S139 and PS2 stages) and preferred lugging the spent S139 case.

Now given the option of going the route of option 4) vs developing a brand new vehicle, ISRO chose to go the latter way. For heavier payloads, you need a CUS with a higher thrust, which anyways needed to developed , so they went ahead and did that. The lower stages is a very easy upgrade path from S139 to S200 . The only other thing was clustering 2 UDMH/N204 engines.

However, the config they have chose for LMV3 is pretty outdated. While removing the key bottlenecks imposed by the design choice in the lower stages of GSLV Mk1/2, they really should have gone for a more "modular" vehicle from the start. That would mean ground lit high Isp LOX/Kerosene lower stages providing the back bone of the lift (supplemented by solids as may be needed for higher payloads) . As is, the L110 needs replacement ASAP and provides a good opportunity to relook the product roadmap and strategy as it is still very early and it will cost very little to tweak it. Further along, changing the config etc will not be possible without huge costs.

The design choice of lower stages of GSLV MK1/2 STRANGLED what was a 6 Ton GTO potential vehicle (given the underlying tech it had) to just 2.5 tons . Such a mistake must never again be repeated , for any reason.

SSSalvi · Post by **SSSalvi** » 23 Sep 2016 15:04

At last launch brocure [urlhttp://www.isro.gov.in/sites/default/files/psl ... ochure.pdf[/url] is out for next launch.

SCATSat-1 released @ 730 Kms
PS4 reignited in next orbit for 20 sec to reduce altitude to 689 kms. Ignition for 29 sec
Alsat-1N, NLS 19, Pratham, PiSAT, Alsat-1B, Alsat-2B and Pathfinder-1 are released in that order.

symontk · Post by **symontk** » 23 Sep 2016 15:29

World space week celebrations

http://wsweek.vssc.gov.in/