Indian Space Program: News & Discussion - Sept 2016

[Suraj]

Thanks for all the responses. Looks like I kicked off a stimulating discussion with my original questions

[disha]

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.

This is ridiculous. You are stretching and twisting words and then proceed to deride posts based on your own imaginations*.

It is not that they did not have LOX/Kerosene., they (soviets) just did *not* have *all* the functional soft and hard pieces including high grade kerosene to make an F1 size engine. In simple terms they did not have the industrial base to get to F1 sized engines in 1960s.

The above was in question as to why the soviets could not come up with F1 sized engines in 1960s.

Korolev/Glushko's uneasy "partnership" is legendary. Glushko never went in for LOX/LOH combination but instead relied on LOX/Kerosene only grudgingly and more quickly relied on UDMH bi-propellants. Korolev did not like the UDMH bi-propellants, considering them dirty (which they are!). And this uneasy "partnership" defined the engines that came out of the Soviet space program (and also influenced the Chinese space program to a big extent). It was further the intertwining of missile development influencing the space launch systems which further influenced their engine options.

Timeline here is important., from 1960 to 1974. In the intervening 14 years., Glushko had to do a major turnaround and had to use LOX/Kerosene for RD-170. Which itself was a slow and torturous progress. In fact, even in RD-170 they could not solve the combustion instability issues and had to fall back on clustering the engines with a shared turbo pump.

However the combustion instabilities is a known issue., what is not widely known is that the Kerosene itself was not good enough in 1960s to be widely used to create a F1 size engine.

And of course it is not just the industrial pieces like high grade kerosene and science on combustion instabilities which goes into making larger and more complex engine., it is that the entire technological base of the country needs to be tuned to achieve that result.

*RD-170 came about in late 70s/early 80s for the Energia program. This is where the Soviet tech came far enough to support a staged combustion cycle.

However you sir used response in context to different era (60s) and stretched it to support your pet imaginations derisively.

PS: Of course you posted that Nat Geo video which was circulated several times over on this very pages. That does not give any information on why Soviets lost out on the moon race in 60s.

PPS: Chinese lost their latest SHLV LM 5 rocket. This is their second attempt after 2 years and this one failed spectacularly (first one failed to reach the intended orbit)., what do you have to say about their big capacity?

[disha]

Thanks for all the responses. Looks like I kicked off a stimulating discussion with my original questions

Simulating? Or Controversial?

As long as it remains objective., it will be a worthwhile effort.

[disha]

...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.

This has been answered on this very pages., point is that the GSLV Mk1/2 is a reliable design and using already developed stages and barring the issues with russian engines and shroud tolerance issues., does reach its intended orbit - like the four consecutive successes of GSLV Mk 2.

Second., the payload penalty is few hundred kilograms. Not a huge deal. Of course., the next step is to replace the S138 booster with S200 and streamline the launch profile.

It is correct that the GSLV Mk-1/II design is sub-optimal., but my point is that is what the Indian technological base at that time could provide and being derisive about ISRO's achievements is thus not just silly or naive but racked with ulterior motives. Just to point out., it was with immense effort that the derisive name calling of ISRO (Indian) rocket engines came to a stop.

---

On the naming convention., I know it is a minor point., but I also provided the references to indicate why I think that LVM3X-CARE was a one-off.

[Suraj]

Simulating? Or Controversial?

As long as it remains objective., it will be a worthwhile effort.

I hope posters will simply ignore others' confrontational tone because overall a lot of useful and enlightening knowledge is being presented

I just read about the Chinese launch failure . As I understand, they took the Glushko approach by and large, using hypergolic fuels rather than LOX/RP1. Their recent efforts to build capability in the latter appear tortuous .

[sohamn]

Second., the payload penalty is few hundred kilograms. Not a huge deal. Of course., the next step is to replace the S138 booster with S200 and streamline the launch profile.

Where did you get the info that the empty core stage weight is few hundred kilos? I thought that the core stage shell + engine weighs few tons. And if I am right then it is a big penalty to haul few useless tons for a minute or so.

[disha]

^^Sohamn saar., I called it "payload penalty". So please read it right. It is "payload penalty"., the penalty on payload that is going to reach the orbit. That is because of the "inefficient" first staging., the payload penalty for GSAT GSLV Mk II is few hundred kilos.

And sir, you are assimilating the information wrong. Payload penalty is say one is able to launch 2800 kgs GSAT in optimal configuration., one ends up launching it at 2200 Kgs because of "inefficient" first staging.

[prasannasimha]

^ The weight penalty calculation was done previously and the penalty for the final payload was not as large. .The thing is that what was done was with whatever PSLV architecture that they had.

[sohamn]

Just read in spaceflights that empty S139 weighs over 30 tons. So, without seeing the calculations ( and I could be absolutely wrong ) - hauling approx 30 useless tons in the lower atmosphere for 60 secs just gives a payload penalty of few hundred kilos looks weird.

[Sridhar]

Suraj

Second the comment about the quality of the discussion. Vina's and ldev's posts have been very enlightening in particular. Thanks for the inputs/links.

Launch vehicle technology is unforgiving. Failures are to be expected for even the most competent of players. The Chinese will figure it out as well - they have the commitment and the funding.

The achievements of ISRO are that much more creditable given the difficulties involved, the constraints placed by the industrial base and the funding levels.

Disha: I wasn't trying to diss ISRO for their design choice - they must have surely gone through a thorough discussion given the strong culture of reviews they have. I am also aware that this was discussed earlier on this thread (but then so were many other things discussed on the forum ). That said, will look up that discussion again to see what was the payload reduction due to this design choice.

[Sridhar]

Vina,

Further to your comment about soot and the Soviet/Russian launchers, isn't it the case that the pre-burners in the R-7 Semyorka derived launchers do not even use RP-1/kerosene in the first place? So, the question of soot does not even arise.

[Sridhar]

Where is Mullah Enqyoob btw? Really miss his knowledge and humor on the forum.

[negi]

RD-107s on R-7 used steam generator using hydrogen peroxide and catalyst to drive the turbines so the turbines did not need any LO2-RP-1 mix to be burnt in a pre burner to generate 'gas' it was basically similar to the V-2 rocket setup.

[negi]

The topic of combustion instability in a large combustion chamber is imo being unnecessarily mixed with use of kerosene ; it is not as if Russians have made large nozzles using some other propellant other than Kerosene .

On similar lines F-1 is a wrong analogy it employs gas generator cycle i.e. Americans have also not mastered or made RP-1/LH2 powered engine which employs staged combustion in class of RD-170.

Basically both chose different paths depending on circumstances and interests .

Americans when they mastered the SSME chose to simply come out with RS-68 a much simpler derivative of the same and hence Delta LVs employ LH2 in the first stage (which is counter intuitive given the storage and fueling constraints around LH2) i.e. they never went out of the way to make a RP-1-LH2 based staged combustion cycle engine ground up. Soviets did the same they had achieved their numbers by mastering the staged combustion cycle using RP-1-LH2 combine so why would they go out of the way to solve combustion instability issues with large nozzles , they got their numbers by clustering the combustion chambers .

[vina]

Further to your comment about soot and the Soviet/Russian launchers, isn't it the case that the pre-burners in the R-7 Semyorka derived launchers do not even use RP-1/kerosene in the first place? So, the question of soot does not even arise.

The kerosene is used to cool the combustion chambers via regenerative cooling. The kerosene is specially formulated (RP1) not to gum up due to residues / build soot there due to disassociation there as well.

[disha]

- hauling approx 30 useless tons in the lower atmosphere for 60 secs just gives a payload penalty of few hundred kilos looks weird.

Sirji., Just because it appears weird does not mean it is wrong.

Think about it., take any rocket launch. A 400 tonne rocket ends up launching say 4 tonne payload! Isn't that weird?

[disha]

Where is Mullah Enqyoob btw? Really miss his knowledge and humor on the forum.

Mullah enqyoob is trying to figure out GST nowadins

[sohamn]

- hauling approx 30 useless tons in the lower atmosphere for 60 secs just gives a payload penalty of few hundred kilos looks weird.

Sirji., Just because it appears weird does not mean it is wrong.

Think about it., take any rocket launch. A 400 tonne rocket ends up launching say 4 tonne payload! Isn't that weird?

Yes, Dishaji - the world seems too weird nowadays. May be I should have focussed on Physics a little more in the good old days.

[disha]

Yes, Dishaji - the world seems too weird nowadays. May be I should have focussed on Physics a little more in the good old days.

Honestly., I blame the edu sector for making all this subject uninteresting and unnecessarily challenging.

We fly diwali rockets and nobody is able to explain why the rocket engine (it is a single solid state engine) is in the front attached to a long stick. This is an interesting question here itself!

I mean as kids we do launch our own rockets but that is never a question in any of the physics paper I attempted. In fact, in std 7 itself the dynamics of rocket propulsion (bhu chakkar & rockets for eg) could be introduced with kids asked to only observe, contemplate and then apply what they have learnt in physics/maths to their real world observations.

[sanjaykumar]

Yes, many lament the way physics is taught. Start with kinematics, just in case they have an ember of interest in physics, then when they have all departed for good, lecture on the more interesting topics of quantum mechanics, special and general relativity in reverberating empty halls.

[nirav]

I mean as kids we do launch our own rockets but that is never a question in any of the physics paper I attempted. In fact, in std 7 itself the dynamics of rocket propulsion (bhu chakkar & rockets for eg) could be introduced with kids asked to only observe, contemplate and then apply what they have learnt in physics/maths to their real world observations.

Yes.
Our curriculum is way short on the rocketry aspect.
The only exposure kids have is Sivakasi rockets in diwali.

I've been fascinated with rockets since childhood.
My attempts at model rocketry however always ended up in big kabooms.
I did however manage successful staging with Sivakasi rockets with the help of some mseal and cardboard fins

Always envied US model rocketry scene. And ogled at Estes rockets..

The scene is still the same..

[Atmavik]

Yes, Dishaji - the world seems too weird nowadays. May be I should have focussed on Physics a little more in the good old days.

Honestly., I blame the edu sector for making all this subject uninteresting and unnecessarily challenging.

We fly diwali rockets and nobody is able to explain why the rocket engine (it is a single solid state engine) is in the front attached to a long stick. This is an interesting question here itself!

I mean as kids we do launch our own rockets but that is never a question in any of the physics paper I attempted. In fact, in std 7 itself the dynamics of rocket propulsion (bhu chakkar & rockets for eg) could be introduced with kids asked to only observe, contemplate and then apply what they have learnt in physics/maths to their real world observations.

That would be safranization of edu. Physics education is still better than Math education where avg folks are scared off.

[akashganga]

http://spacenews.com/darpa-trying-to-la ... an-rocket/

[ArjunPandit]

Yes, Dishaji - the world seems too weird nowadays. May be I should have focussed on Physics a little more in the good old days.

Honestly., I blame the edu sector for making all this subject uninteresting and unnecessarily challenging.

We fly diwali rockets and nobody is able to explain why the rocket engine (it is a single solid state engine) is in the front attached to a long stick. This is an interesting question here itself!

I mean as kids we do launch our own rockets but that is never a question in any of the physics paper I attempted. In fact, in std 7 itself the dynamics of rocket propulsion (bhu chakkar & rockets for eg) could be introduced with kids asked to only observe, contemplate and then apply what they have learnt in physics/maths to their real world observations.

dishaji,
how will you set sivakasi rocket to fire from a limca bottle if the single state is in bottom or middle.
In my childhood i did try doubling or tripling the raackets, and once it ended up in my neighbour's house and caused some damage to him and my backside . After that redshift, I reverted to the single stage old fashioned from our ceiling.

[disha]

^^Arjun'ji look at the positive side., with your singular focus you at least became pandit on redshift! But no, you must not put the SSME (Single Stage Main Engine) in the middle or the bottom. Thinking about it, you were lucky to not get the redshift from the rocket itself!!

I did not learn about redshift but discovered black hole., what I did was tie 2 of them together (my first clustered stages if you will) and figured out a way to fire them together by making sure that the batti is just right size and has a common point to burn from. All worked, except the raakit gracefully arc'ed into the neighbor home like a bhramos and I scooted & hid under a bed in the farthest room one can think off.

So the question is why the raakit behaved that way? Point is why does SDRE Hindu raakits have their SSME (Single Stage Main Engine) at the top of a stick?

[Atmavik]

not sure if this was posted before. UAE and Chiliean customers watching Performance Normal and then trying to figure out some Hindi

https://www.youtube.com/watch?v=mU4jVkj0Um8

[disha]

Atmavik'ji., Hindu rockets when young are short and lean and without any mass due to all the malnutrition. As they age they become wider with addition of boosters due to all the rice they take and acquire a shorter & darker look. Look at SLV, ASLV and GSLV-mkIII - just what is the difference between ASLV and GSLV MkIII? Both are three sticks stuck together!.

Here is an article on ASLV-I failure in full. Emphasis mine.

http://indiatoday.intoday.in/story/fail ... 36942.html

NewsMagazineSCIENCE AND TECHNOLOGY
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Setback in the sky
The failure of the ASLV mission less than a minute after a perfect blast-off is a major blow to India's ambitious space programme. The launch represented a quantum jump in space technology. An analysis of the implications of this set-back.

Amarnath K. Menon
April 15, 1987 | UPDATED 16:44 IST

The 31-hour countdown was smooth, the lift-off perfect. But, less than a minute after the sleek Augmented Satellite Launch Vehicle (ASLV-1) blasted off from the Sriharikota Range last week, and arched into the sky trailing squiggles of smoke, the 40 tonne rocket suddenly lost height and direction and plunged into the Bay of Bengal.

The course taken by the first flight of the new generation of rockets was symbolic of the sudden dampener the failure represents for India's ambitious space programme.

The ASLV-1 launch, delayed by 15 months, was tom-tommed as a "quantum jump" for Indian space scientists - a giant leap into the use of an array of hi-tech, inter-active microprocessors, to form what is called, the closed loop guidance system meant to keep the rocket on course at the right speed, and to make in-corrections if it goes astray. The other major technology to be tried out by the Indian Space Research Organisation (ISRO) for the first time, was the strap-on systems - two boosters tied to the main vehicle to give the rocket a more powerful thrust at lift-off.

All that came to naught when the ASLV-1's mid-day blast-off from the Sriharikota Range in coastal Andhra Pradesh, ended in a watery grave. For the scientists, the failure was a bitter and traumatic development. Everything had gone with clockwork precision from the start of the final countdown, at 5 a.m. on March 23. All checks were completed and launch readiness conveyed to Mission Director M.S.R. Dev for the final okay, 14 minutes before lift-off. Finally, at 12.09 p.m, the two strap-on boosters were ignited and ASLV-1 soared majestically into the sky, leaving behind a fluffy trail of smoke.

From the terrace of the two-storeyed mission control centre, Prime Minister Rajiv Gandhi, ISRO Chairman Professor U.R. Rao, Andhra Pradesh Governor Kumudben Joshi and Chief Minister N.T. Rama Rao watched. Another 10,000 were watching the historic event from viewing galleries and housetops in the Sriharikota Range employees colony. As the rocket climbed steadily, they hugged one another and shouted in excitement. At a height of 12 km, the boosters separated and came down in two slender smoke trails.

The ASLV blasts off

But in the mission control room, scientists and engineers quickly realised that something had gone wrong. The first warning of the impending disaster came 48.5 seconds after lift-off, when the plotters and consoles in the Range Safety Room showed ASLV-1 going off course. Four seconds later, the burnt out strap-on boosters separated, and the rocket went astray.

In the blockhouse bunker, barely 100 metres away from the launch pad, the 44 scientists and engineers stared in disbelief at the console spewing data, gathered from signals sent by the 150 kg satellite sross-1 (Stretched Rohini Series Satellite-1), intended to be put in a 400 km circular orbit by ASLV-1. The console showed the rocket taking a sharp nose dive.

All of them, including five women, had spent sleepless nights during the last three months, assembling and linking the 55 sub-systems of the rocket to a specially prepared computer programme, for its final launch. The data showed that the rocket motor to be ignited after 48.5 seconds had not fired, and finally, 163 seconds after blastoff ASLV-1 dropped headlong into the Bay of Bengal.

The cruel irony is that the motor which failed was a proven one, being the first stage of the earlier Satellite Launch Vehicle-3 (SLV-3) rockets. Said the Director of Sriharikota Range M.R. Kurup: "It appears that the failure of the motor to burn is the reason for ASLV-1 not going up, but it will be two weeks before we can conclude why the motor failed."

Nearly two hours after blast-off, Rao officially announced that ASLV-1 had failed. "It is a setback. But ISRO will be at the drawing-boards to get the rocketry programme operational as quickly as possible. We are committed to self-reliance in launch vehicle technology," said Rao. Prime Minister Rajiv Gandhi tried his best to reassure the disappointed scientists. Congratulating them for "the good work ISRO has done", he told them not to lose heart. "It is only a setback in time. It is only when you stumble that you can get up and walk better," he said.

But his words sounded hollow in the face of the failure and its implications. For a space programme begun way back in November 1963, when a 7 kg pencil-shaped rocket was launched from a decrepit church building at Thumba near Trivandrum, last week's performance was a major setback. It was the first launch in four years, and the second of five launchings to fail in the last nine years.

The first SLV-3 rocket came hurtling down five minutes and 15 seconds after lift-off, on August 10, 1979. The next three SLV-3 launches were successful and ISRO changed gear to put the first ASLV in flight, skipping the schedule for two more SLV-3 launches, ISRO also decided on a brain transplant, and put in the closed loop guidance system in ASLV-1, instead of using the open loop guidance system, as was originally planned. But the gamble to save time in order to take rocketry to the operational phase, did not pay off.

The strap-on booster separates: Watery grave

The major setback caused by the failure of the ASLV-1 mission is in testing the flying qualities of the new class of rockets. Though in its external features ASLV-1 is an upgradation of the earlier SLV-3 design, the 'brain' of the rocket is an improved one. The closed loop guidance system is the new kind of brain to control the rocket's speed, its direction and make corrections in flight, if it deviates from the pre-planned path, and ultimately lob the 150-kg SROSS-1 satellite into the 400-km circular orbit.

Mission Director Dev said at the end of the scientists' "quick look review" that "the setback is the lost opportunity in getting first hand information from the satellite about how the ASLV-1 behaved and the efficacy and accuracy of the closed loop guidance system."

Satellite tracking specialists also missed the chance to study how the distance of a satellite in orbit can be measured by firing a laser beam at onboard reflectors, ISRO is to decide by May whether the experiment can be repeated on the ASLV-2 mission already committed to carrying a new kind of earth scanner. The actual cash loss by the failure of the" ASLV-1 mission is about Rs 6 crore. Says Kurup: "Failures are part of the game but the setback is only one of time. This can be absorbed before we begin flying the next generation of Polar Satellite Launch Vehicle rockets."

With the stand-by sub-systems, including the main rocket vehicle, built by Hindustan Aeronautics Ltd and motors on the shelf, the engineers at Sarabhai Centre can get the second one ready in less than a year, after making changes to be suggested by the ASLV-1 failure analysis committee by April 15.

Space programmes the world over face failures. Rocket technology is tricky and much of the know how is not shared among countries. Only six nations - US, USSR, France, China, Japan and India - have developed launching facilities. All the programmes have had their share of failures. Strangely, China, a latecomer to the field, has the most enviable record of 18 launch successes and only three failures.

In that context, ASLV-1 cannot really compare with rockets like China's Long March, the European Space Agency's Ariane, US's Delta and USSR's Proton. They all stand more than 33 metres tall, weigh more than 220 tonnes at lift-off and can send a satellite more than 1,500 kg into orbit around the earth. Even the next generation of Indian rockets - the Polar Satellite Launch Vechicle - will, for its 44 metres height and 260 tonnes weight, be able to put only a 1,000 kg satellite into orbit.

Clearly, the height-weight factor is a crucial one, and if heavier loads are to be ferried into space, ISRO will have to work on alternative designs, admit engineers of the Vikram Sarabhai Space Centre, Trivandrum, where the designs are drawn. It involves much more than the money now spent on the space programme. The ASLV project is likely to cost Rs 23 crore and the Polar Satellite Launch Vehicle is to cost more than Rs 350 crore.

For India, the stakes in the space programme are huge. In addition to acquiring international prestige, the development of rocketry can perhaps bring the country a thick wad of much needed foreign exchange through commercial launchings by the turn of the century.

Extra launches can also spread the heavy cost of developing each rocket. But for the present, the concern is with mastering the hi-tech in avionics for guiding and controlling spacecraft, and collaborating with Indian industry to supply space grade equipment. Admits S.C. Gupta, director of the Sarabhai Centre: "All this could not be put to test by the first ASLV, but we hope to be back with the second flight in a year to try out the new technologies."

An equally important reason for building rockets is to launch India's own satellites for telecommunications, weather forecasting, remote sensing and radio and TV networking. The Satellite Instructional Television Experiment covering village clusters in six states, with programmes for farmers and school goers in 1974-75, using channel-time bought on the France-German Symphonic satellite, showed the exploits of space technology to Indian planners for the first time. Meanwhile, the ISRO Satellite Centre made the Aryabhata and later, Bhaskar I and II satellites carry cameras to take pictures of the country to map its surface and sub-surface resources.

Eventually ISRO was able to convince the Government to contract Ford Aerospace to build the multi-purpose Indian National Satellite System (INSAT-1A). Though much of the ground work had not been done by the time INSAT-1A was orbiting the earth, the failure of the satellite and the orbiting of INSAT-1B gave user agencies enough time to build the earth stations and other facilities, to use the satellite efficiently. Today, the satellite's use for such practical applications goes on unnoticed.

The ASLV-1 with the booster rockets
"It is a setback. But we will get the programme operational as soon as possible."
U.R. Rao,chairman, ISRO

The use of satellite photographs for planning and improving agriculture, developing wastelands, tapping groundwater sources and mapping forest and mineral wealth has not grown, though pictures taken by the American Landsat series of satellites and the French spot satellite are available with the ISRO's National Remote Sensing Agency.

Says Rao: "This is a vital area where, if we have our own satellite, it is possible to map whatever resources we want to know about, and do not have to depend on others for the latest photographs." The Indian Remote Sensing satellite (IRS), to be launched by a Russian rocket in September-October this year, has comparable capabilities.

ISRO has an elaborate IRS utilisation programme to interpret the wealth of data beamed back by the satellite, for better planning in agriculture and mining of metals. But Rao says all states have not set up remote sensing data utilisation centres, as suggested more than four years ago. Laments Rao: "The realisation about satellite applications bringing a revolution in our way of life simply does not exist." But he is hopeful that the IRS utilisation programme will take the benefits of space technology down to the individual farmer.

The fall-out of the space programme is not as impressive as in the US, where space research led to the micro-chip and fibre optics revolutions. But one encouraging example of import substitution and indigenisation of technology is the making of a propellant fuel with unsymmetrical dimethyl hydrazine, by the state owned Indian Drugs and Pharmaceuticals Limited - for the Polar Satellite Launch Vehicle programme - using ISRO's own process of production.
The chemical used to make the fuel was found to be useful in agriculture. But for more striking spin-offs, Indian space technology itself has to evolve. After last week's failure, that process is certain to be delayed even further.

[symontk]

Just read in spaceflights that empty S139 weighs over 30 tons. So, without seeing the calculations ( and I could be absolutely wrong ) - hauling approx 30 useless tons in the lower atmosphere for 60 secs just gives a payload penalty of few hundred kilos looks weird.

You right in assuming payload penalty. But how much it will be is a complex calculation

One aspect to look is that top stage performance are critical than lower stage performance. For example, if you save 1 ton in top most stage, you payload can be increased by 1 ton itself. But as you go down the stages impacts of saving are less. This is because over all weight profile will diminish any weight gains

If you look at PSLV/GSLV design, roughly you can add 1 ton to the payload, if you are able to save 100 tons in the first stage

[Singha]

what is the revisit time to the same orbital plane of our 6 cartosats and 2 risats in polar orbit?

i am able to track them using nyo but not sure how to calculate it based on the satellite speed and rotation of earth

[Sridhar]

Thanks for sharing the article post the first ASLV test that resulted in failure. This test initiated my interest in ISRO. I wrote my very first article about India's space program for my school's annual magazine and have followed ISRO keenly ever since. It's amazing how far we have come since then. Could have never imagined a 640T behemoth being launched from SHAR at the time this article was written. Kudos to all the people who made it happen. And apologies to the people like Nambi Narayanan who we betrayed.

[Neela]

Following up on earlier posts on Cartosats.
More details here:
https://forum.nasaspaceflight.com/index ... =32023.480

Castosat 2E was launched last month.
Next is Cartosat3 series with resolution of 0.25m .
Mar '18 - Cartosat 3
Mar '19 - Cartosat 3A
Mar '20 - Cartosat 3B

[SSSalvi]

what is the revisit time to the same orbital plane of our 6 cartosats and 2 risats in polar orbit?

i am able to track them using nyo but not sure how to calculate it based on the satellite speed and rotation of earth

Rigorously speaking ' Repetitivity ' is the time period between 2 consecutive overhead passes at the same point. It is purely a function of i and h.

But current satellites have a capability to look sideways on both sides so even if it is not overhead it can still image a point more often than the above period ( e.g. you can 'see' a place from 6 or 7 passes passing on both sides of the location.

This sensor stearability gives some good possibilities as shown here ( from Singapore satellite ).



This results in a more frequent revisit than cycle period. E.g. Cartosat 2 has a 'revisit' of 4 to 5 days while it has ' Repetitivity ' of ( yes, it is correct ) 310 days!!

n2yo or other orbit calculators will not be able give revisit period because it is a satellite sensor specific characteristics ( How much the sensor can look sideways )

For each satellite mentioned by you, you will have to refer to satellite sensor specific datasheet. ( like https://nrsc.gov.in/sites/all/pdf/brcartosat2.pdf )

[Singha]

what I am after is this:

my 'go to plan' based on a post by perhaps a retired IA type of Rohitsvats blog article that the red line for immediate counter mobilization is chinese brigades crossing the Tsangpo

between 6 cartosats and 2 risats , we "should" be getting atleast 1 daily revisit over the major roads feeding into the eastern sector from the tsangpo bridges and sniff out temporary military bridges built on the river to speed induction.

following this cue, RAW ARC could fly its GMTI sensor planes high over nepal or bhutan to confirm and track the movements of masses of vehicles on the flat tibetan plateau in any weather. obviously this has to be a on-call mission and not 24x7 which is possible only when we have global hawk sized platforms....but it can confirm findings and provide more specific cues to enemy intentions. we no longer have the Mig25R for manned dashes across the problem area.

there are about 10 bridges big and small between xigase and lhasa. heavy resources like armour bridges, missile batallions, artillery regiments and SAM units will likely move through these bridges to the south from depots further up in tibet or brought in by rail. and all of these will need 100s of trucks to ferry supplies like fuel and reloads.

hope both automated processing SW and teams of imagery analysts are on the job 24x7

[SSSalvi]

Yes they are ( at least 10 years back they used to .. so now much better may be ). All entities you mention had much better than what we think are.. rest assured.

[sum]

^^ Am curious if many these capabilities( like the processing and imaging SW, high res space optical lenses) are homegrown or many critical bits are sourced from abroad since these are usually very niche and closely guarded stuff and havent seen much on these aspects from any ISRO publications.

[SSSalvi]

Let's assume that they know their job better than we outsiders.

[abhik]

The planet satellite constellation launched by PSLV some time back is also an interesting concept. Dozens of small sats which "images the entire planet every day".

[SwamyG]

What can GSAT-7 Rukmini do

Rukmini is keeping a close eye on submarines at the Indian Ocean

What is Rukmini? GSAT 7, or Rukmini was launched on August 30, 2013. With the help of this multi-band military communication satellite, also known as Rukmini, the Indian Navy could actually expand its blue-water capabilities and minimise reliance on other foreign satellites which provide intel to its ships. It was the first military communication satellite developed by the Indian Space Research Organisation (ISRO) for the Indian Defence forces, with the Indian Navy being the primary user. Built on September 29, 2013, Rukmini is also the last of ISRO’s seven fourth-generation satellites. Weighing nearly 2,650 kg, the satellite has a minimum of 2,000 nautical mile footprint over the IOR. Rukmini was launched using an Ariane 5 ECA rocket from Kourou in French Guiana. This gave India a major push in maritime security

[akashganga]

Watched live webcast of spaceX launch using refurbished 1st stage which is again retrieved. In front of our eyes spaceX has done which no one else dared to do. By repeatedly reusing first stage they will be much cheaper than even ISRO in the long run. Nobody in india is even talking of reusing. At this rate spaceX will beat the hell out of all other competition including India, Russia, china. They are even researching reuse of second stage.

[sivab]

Watched live webcast of spaceX launch using refurbished 1st stage which is again retrieved. In front of our eyes spaceX has done which no one else dared to do. By repeatedly reusing first stage they will be much cheaper than even ISRO in the long run. Nobody in india is even talking of reusing. At this rate spaceX will beat the hell out of all other competition including India, Russia, china. They are even researching reuse of second stage.

Ignorance is bliss Why let the facts get in the way, continue pissing on India.