Chandrayan-2 Mission

[UlanBatori]

tolerance could be there for pressure loss with minimal impact on performance for launch to go ahead?

usual question that comes up: "Schedule is a schedule, hit da switch?"
I assume this 350Bar HELIUM tank is relatively small (must be very heavy otherwise) and is intended to displace the toxic explosive propellant with inert Helium as it is pushed out into the pumps, before being REALLY pressurized and injected into the engine combustion chamber. When propellant is all gone, you just have a bit of inert helium inside.

So the question is: WHY is there a leak? Is it saying that
(a) a pipe fitting is faulty (minor) or
(b) that there is a crack in a weld of the 350-atmosphere tank?

What happens in either case when the engine fires up and the vibration shakes the whole vehicle? I don't think there is any question of taking that risk. In one case the flow of propellant to the pumps cannot be regulated (or may stop), so getting to the right orbit is impossible, and in the other case, more immediate catastrophe during launch itself.

The NOTAM suggests that they have found and fixed it, but are now checking in more detail. One faulty fitting, then what about the others? I assume that they can test the tank pressure-holding without filling the propellants. Case (b) must have been thoroughly checked and tested per SOP, so it must be a huge relief to find that it is (a).

I wonder seriously if much deeper gyan about precise equipment specs etc is a good idea to share here to impress each other.

[prasannasimha]

Helium is used to pressurize ullage space to ensure pgopellant is flowing ptppefly in zero gravity. They will have standard parameters for these.

[UlanBatori]

Reminds me of putting LeakSleuth soap-solution from a plastic bottle around the joints and watching for bubbles from a 2500 PSI hydrogen or methane tank. Plenty of Teflon Tape on hand. Weld-checking means X-rays etc, hain? Standing up a long way above the ground, this must not be not so easy.

[Mort Walker]

Reminds me of putting LeakSleuth soap-solution from a plastic bottle around the joints and watching for bubbles from a 2500 PSI hydrogen or methane tank. Plenty of Teflon Tape on hand. Weld-checking means X-rays etc, hain? Standing up a long way above the ground, this must not be not so easy.

I've used children's bubble liquid for detecting leaks in systems pressurized with inert gasses which works very well and is cheap, but this won't work for helium. For very small leaks caused by a vacuum system you have to use a specialized helium leak detector system. Helium is used by the semiconductor and electronic component manufacturing industry, so it's readily available.

[Rishi_Tri]

tolerance could be there for pressure loss with minimal impact on performance for launch to go ahead?

usual question that comes up: "Schedule is a schedule, hit da switch?"
I assume this 350Bar HELIUM tank is relatively small (must be very heavy otherwise) and is intended to displace the toxic explosive propellant with inert Helium as it is pushed out into the pumps, before being REALLY pressurized and injected into the engine combustion chamber. When propellant is all gone, you just have a bit of inert helium inside.

So the question is: WHY is there a leak? Is it saying that
(a) a pipe fitting is faulty (minor) or
(b) that there is a crack in a weld of the 350-atmosphere tank?

What happens in either case when the engine fires up and the vibration shakes the whole vehicle? I don't think there is any question of taking that risk. In one case the flow of propellant to the pumps cannot be regulated (or may stop), so getting to the right orbit is impossible, and in the other case, more immediate catastrophe during launch itself.

The NOTAM suggests that they have found and fixed it, but are now checking in more detail. One faulty fitting, then what about the others? I assume that they can test the tank pressure-holding without filling the propellants. Case (b) must have been thoroughly checked and tested per SOP, so it must be a huge relief to find that it is (a).

I wonder seriously if much deeper gyan about precise equipment specs etc is a good idea to share here to impress each other.

Thank You.

[disha]

I remember reading somewhere that Mk III does not have SITVC. What looks like SITVCs are actually tanks carrying oil. The oil/liquid must be for hydraulics or something on the flex nozzle.

https://www.isro.gov.in/sites/default/f ... ochure.pdf

You are right, per link you posted it clearly mentions as oil for FNC (Flex Nozzle Control(?)). So the SITVC-lookalike is actually *not* SITVC but FNC Oil tank.

My respect for Asia's largest solid rocket booster goes up a couple of notches! It makes sense that PSLV/GSLV attain Arjun-brand precision in their sat launches.

[Amber G.]

It all started with ..
Not too long ago .. On November 21 1963, that a small rocket took off from Thumba..

[Amber G.]

Meanwhile - Just for the record, let us post this:

[UlanBatori]

Building stadiums (stadia?) / amphitheaters is probably not a great bijnej plan on the Moon. One stadium every couple of miles! And if the landing speed is a bit off, whammo! Another stadium with a small mound of melted metallic trash in the middle.

[hnair]

Hopefully the big lady rises majestically in next few days itself, with blessings of the gurus

[Vips]

Isro pinpoints Chandrayaan-2 leak to ‘nipple joint’ of cryogenic engine.

Working overnight on the aborted Chandrayaan-2, the Indian Space Research Organisation (Isro) teams have pinpointed the leak in the GSLV-MkIII cryogenic engine to a ‘nipple joint’ of the helium gas bottle that supplies pressure to the fuel and oxidiser. Why it happened remains the crucial question Isro engineers are trying to answer.

Isro had aborted the Chandrayaan-2 launch 56 minutes before its scheduled lift-off at 2.51am on Monday.

“The good news is that we can fix the leak without dismantling the rocket, since there is an access door to the gas bottle which is atop the oxygen
tank,” a senior scientist told TOI. “The bad news is that unless we ascertain the reason for the leak, there is a probability of the problem recurring.” Not having to dismantle means Chandrayaan-2 may be able to fly before the end of the July launch window, but a final failure analysis will be available only in a day or two.

Sources told TOI that the leak wasn’t serious enough to impair the flight, but Isro decided to apply “abundant caution,” given the importance of the Rs 978-crore project that would make India only the fourth country – after the US, Russia and China – to land a craft on the lunar surface.

The helium gas bottle has a capacity of 34 litres and it was to be pressured up to 350 bars before regulating the output to 50 bars. “The leak was bringing down the pressure by four bars per minute. The rocket could’ve still made it, but we didn’t want to take any chances,” a source said.

A veteran of Isro failure analysis said teams would now look at the proximity of the faulty ‘nipple joint’ to the oxidiser tank that stores liquid oxygen at minus 183 degrees Celsius. “If the joint was close to such a low temperature, the reason could be micro shrinkage of the joint. In that case we need to insulate it or shift the joint away from the coldest point,” the scientist said.

Bigger leaks in the gas bottle can, besides affecting combustion and velocity, send the rocket spinning out of control. For now, Isro is confident of rectifying the fault and flying to moon without much delay.

More than 7,000 people from across the country had gone to the Sriharikota spaceport to witness the Monday launch.

President Ram Nath Kovind was with senior Isro scientists at the mission control centre when the launch was called off at 1.55 am.

[ArjunPandit]

^^hats off to these guys..once all this is done hope some guys interview them and make these guys national herrows who did the right thing even when the president of nation was there..

[g.sarkar]

the opposition to India's space program continues even today, driven by commercial jealousy and fear of loss of business.
The prospect of India sitting at the high table for formulating rules for the exploitation of space resources and conduct of stellar explorations is unnerving many whites and also the hans.
India may yet be able to pay them back for her thus far and malicious exclusion from the NSG and the SC.

[/quote]
I would love to get the book:
https://books.google.com/books/about/Re ... &q&f=false
Gautam

[UlanBatori]

At a lower level of OT-ness, here is something for Luna-ticks:

https://apolloinrealtime.org/11/

[UlanBatori]

“The leak was bringing down the pressure by four bars per minute. The rocket could’ve still made it, but we didn’t want to take any chances,” a source said.

Did someone say "culture"? THAT is 400% chalta-hain
Leaking 4 atmospheres per MINUTE. That was not bubbling: it was a "fisssss!!!!" The hose/pipe may have blasted loose with takeoff vibrations.

[UlanBatori]

Chetakji, its not "jealosy", it is cryogenically cold logic. Look at the other GEO-sat launch countries: USA (southern tip is still in temperate zone). Russia: Kazakhstan though slightly high altitude, is also 30+ degrees above equator. Frogistanis? They have to drag their stuff down to Guyana, or to Guinea-Bisseau. Both places are politically unstable and a LOOOONG way from their development HQ. Long March launch site is where? Tibet?

Payload fraction to GEO is pretty small, so the additional Delta-V required to change planes and get into the equatorial plane, is terribly expensive. So desh is in the long term, very well positioned for the cheapest launch to GEO. The way to negate that advantage, is to hike the insurance costs. Maybe desh should shift the launch facility down to Nicobar?

[chetak]

the opposition to India's space program continues even today, driven by commercial jealousy and fear of loss of business.
The prospect of India sitting at the high table for formulating rules for the exploitation of space resources and conduct of stellar explorations is unnerving many whites and also the hans.
India may yet be able to pay them back for her thus far and malicious exclusion from the NSG and the SC.

I would love to get the book:
https://books.google.com/books/about/Re ... &q&f=false
Gautam[/quote]

email address

[chetak]

Chetakji, its not "jealosy", it is cryogenically cold logic. Look at the other GEO-sat launch countries: USA (southern tip is still in temperate zone). Russia: Kazakhstan though slightly high altitude, is also 30+ degrees above equator. Frogistanis? They have to drag their stuff down to Guyana, or to Guinea-Bisseau. Both places are politically unstable and a LOOOONG way from their development HQ. Long March launch site is where? Tibet?

Payload fraction to GEO is pretty small, so the additional Delta-V required to change planes and get into the equatorial plane, is terribly expensive. So desh is in the long term, very well positioned for the cheapest launch to GEO. The way to negate that advantage, is to hike the insurance costs. Maybe desh should shift the launch facility down to Nicobar?

wasn't aware, great input.

thanks saar.


but dirt poor SDREs launching for the moon, also gots to be loads of jealousy there.

[Prithwiraj]

Chetakji, its not "jealosy", it is cryogenically cold logic. Look at the other GEO-sat launch countries: USA (southern tip is still in temperate zone). Russia: Kazakhstan though slightly high altitude, is also 30+ degrees above equator. Frogistanis? They have to drag their stuff down to Guyana, or to Guinea-Bisseau. Both places are politically unstable and a LOOOONG way from their development HQ. Long March launch site is where? Tibet?

Payload fraction to GEO is pretty small, so the additional Delta-V required to change planes and get into the equatorial plane, is terribly expensive. So desh is in the long term, very well positioned for the cheapest launch to GEO. The way to negate that advantage, is to hike the insurance costs. Maybe desh should shift the launch facility down to Nicobar?

wasn't aware, great input.

thanks saar.


but dirt poor SDREs launching for the moon, also gots to be loads of jealousy there.

Some BBC reporters were probably given assignments on how India has her priorities flawed with "aid" money being used for fancy space adventures while half of the country bla bla

[ramana]

So root cause was the helium bottle joint developed leak possibly due to environment of being too close to LOX tank?
Was this the first launch of the cryo-engine?
I don't think so.

[g.sarkar]

deleted

[Najunamar]

“The leak was bringing down the pressure by four bars per minute. The rocket could’ve still made it, but we didn’t want to take any chances,” a source said.

Did someone say "culture"? THAT is 400% chalta-hain
Leaking 4 atmospheres per MINUTE. That was not bubbling: it was a "fisssss!!!!" The hose/pipe may have blasted loose with takeoff vibrations.

Agreed that is quite high, but probably the thinking was if it did not deteriorate much then a possible 17 min to the final 3rd stage release would not be in jeopardy? Just guessing as it is hindsight onlee that it was the nipple joint, whether it was a stable leak rate or this was the rate observed quite some time after the abort in which case they may have some post hoc data to support the claim it wouldn't have mattered.

[ramana]

Lets wait to hear what the joint looked like when its take apart.

[Mort Walker]

I feel that since we're talking about moon missions, then a little OT, but here is a pic of Apollo 11 astronauts in 1969 post mission visit to Bombay. I think nearly 2 million people showed up to greet them. Neil Armstrong on left doing namaskar to the public, Michael Collins in the middle, and Buzz Aldrin to the right waving to the public.

[UlanBatori]

Nicobar may not do the job. From what I heard recently, the trouble is that the first stage has to be dropped over water before reaching any landmass (or major shipping route). So this constrains how far you can go downrange before dropping first stage.

Maybe one solution in long term is to have a set of strapped-solid or flyback boosters, that do the initial boost and then fall or return, while the present First Stage then kicks in. Then that first stage will drop way out over Pacific or Atlantic. Or even do one full round and glide back to land at Lakshadweep. Easy to say from EZ-Chair, maybe tough to work out in the optimization. But India has to operate with a strange set of constraints, that gives the rationale for new solutions. Maybe Maldives/ DG might solve this, but even there, the first stage might drop too close to Indonesia.
Call Ulan Bator Cry-O-Jennikx / Hype-e-Sonix Division for deeper advice on TSTO etc.

Also, the real long-term solution per Evil 6th Coujin of UBCOJ is this: The cryogenic Third Stage which is the real cost of the program, should be replaced with a Space Tug that stays in orbit, and gets refuelled in orbit. Gets refuelled from spare fuel of boosters, collected into fuel stations. Comes and catches the spacecraft as it is lobbed into orbit by (expendable) 2nd stage. Takes it to orbit, returns to cruise around and wait for next launch. Just doing this would slash 90% of the cost of GEO missions, not least because of the savings in insurance.
Think about it: That 3rd stage is real bad news. It gets turned on only at the critical time, and has a total operating life of what? 30 minutes total? Huge waste of resources and risk cost.

[Ashokk]

Aborted Chandrayaan-2 may force Isro to tweak cryo stage for future launches

CHENNAI: Failure analysis of the aborted Monday launch of Chandrayaan-2 has presented the Indian Space Research Organisation (Isro) with some “unexpected learning curves” that may lead to tweaks in the cryogenic upper stage of GSLV-MkIII.
As it was first reported by TOI on Tuesday, Isro teams had found a leak in one of the ‘nipple joints’ of a helium gas bottle that supplies pressure to several systems including fuel injection. The reason turns out to be the proximity of the joint to the tank that stores oxygen at minus 183 degrees Celsius; the extreme cold must have strained the joint, causing the leak.

“Now we have to seal and insulate the joint from the cold or shift it away. The second option is tough if we were to work on the engine without dismantling the rocket. Now efforts are on to plug the leak without moving the rocket from the launchpad, so we can launch it sometime early next week,” said a source. A senior scientist said the Chandrayaan-2 setback has presented some learnings for the indigenous cryogenic engine CE-20, which was developed after studying Russian cryogenic engines. The joint that now presents a problem is defined as a rigid joint.
“That’s something Russians do all the time, while the Americans use flexible joints. The rigid joints have lesser chances of leak, but if there is one, they have to be discarded and made again. During their heydays, the Russians produced cryogenic engines by the dozen and they could afford it. They were also supremely confident of their engineering skills. Flexible joints can be repaired,” explained the scientist.
Having worked with seven Russian engines in the past, Isro adopted the rigid joint concept in several places, but it doesn’t have the luxury to discard and use another engine in short notice.
“We may not entirely drop rigid joints, but now we may think of having some add-ons like an ‘S’ loop or a ‘U’ loop that can help deal with such anomalies. This latest setback has been an unexpected learning curve,” he said.

India, which has been using Russian cryogenic engines (KVD-1) for its GSLV launches, developed an indigenous engine (CE-7.5) for its GSLV-MkII and later the more powerful CE-20 for its GSLV-MkIII. Chandrayaan-2 was to be the third flight of GSLV-MIII using CE-20 (the first was in June 2017 and the second in November 2018).
Isro makes not more than a couple of cryogenic engines at a time, one for ground tests and one for flying, and every time one fails, the mission gets delayed for months till a new engine is fabricated. The Chandrayaan-2 experience may force Isro to make some changes in the cryogenic stage.

[UlanBatori]

The Russians got their Helium tanks connected at the Ivan Ivanovich Center for Re-education, Siberia, in January. So minor things like LOX don't make them feel cold. ISRO got theirs done probably at Appu's Toilet and Rocket Plumbing, Toothukkudi in 45 C weather.
In reverse-engineering cryogenic engine, someone forgot to do minor things like develop detailed specs for the operating environment of each part. Chalta hain. Hope they do that when going for private industry outsourcing.

[kit]

does this mean the launch is scrubbed or are they going ahead with next weeks launch?

[kit]

I would love to get the book:
https://books.google.com/books/about/Re ... &q&f=false
Gautam

email address[/quote]

why should it bother the Hans ? .. India started their space program much around the same time as theirs, and better than them in some aspects!

[ArjunPandit]

^^ashokk, this is an interesting post, looking back in time, I used to scorn at these S joints, welding in our initial engineering sems, I was not alone.
Wish I was aware of BRF and ulanbator then.

[UlanBatori]

^^ashokk, this is an interesting post, looking back in time, I used to scorn at these S joints, welding in our initial engineering sems, I was not alone.
Wish I was aware of BRF and ulanbator then.

The problem now is that they are racing to fly with a just-learned solution, implemented for the first time. If there is a failure there will be incredibly loud screaming. If this joint leaked because of the cold of the LOX tank, what happens to the helium tank used to flush the LH2 tank, after many minutes of exposure to that? That is like 6K vs the 183K of LOX.
There goes another ambition for when I grow up: Flight Director, GSLV-10/Chandrayaan-12.

[Prithwiraj]

Cutting corners and using Jugaad with shoe string budgets can only go upto a certain point --- as we cross the boundary of serious space exploration from relatively simple satellite launch--- you have no choice but to invest serious money

[Vips]

does this mean the launch is scrubbed or are they going ahead with next weeks launch?

Isro looking at July 21-22 for Chandrayaan-2 re-launch.

The Indian Space Research Organisation (Isro), which is keen to put Chandrayaan-2 in space at the earliest available window so it has the required time to navigate the lunarcraft to Moon's orbit, is looking at a launch window as early as Sunday afternoon (July 21) or the early hours of Monday (July 22).

The launch of India's second mission to Moon was scrubbed on July 15 after Isro detected a last minute leak in the cryogenic stage of the GSLVMkIII as first reported by TOI.

Sources privy to the ongoing rectification process - engineers are working on plugging a faulty joint - are now telling TOI that the space agency has two tentative schedules.

The TOI had first reported on Monday+ evening that a key decision on the new launch date could come as early as Wednesday and that the launch could be scheduled on July 21. According to sources: "First we thought it could be early July 22 morning, a similar time as the July 15 schedule. Now that has been reconfigured to even may be launch some time Sunday afternoon."

While Isro is yet to officially commit to this, an announcement may be imminent. A senior scientist from Isro's rocket stream, confirmed to TOI that the space agency is "hopeful" of a launch by Monday "That is what we are hearing from teams at the spaceport. It's either Sunday or Monday," another source said. Every launch has an optimal window to achieve the desired results and July 15 had the longest window of 10 minutes. But Isro has a window of at least one minute a day for the rest of the month.

The TOI had, on Monday evening, reported details about a review from the spacecraft side in Isro. As per scientists, missing the July 31 window would have an impact on the programme, as it would need more fuel to achieve the desired destinations. "It could even bring down the life of the orbiter to six months from the current one year around Moon," a source had said.

Also, in an indication of Isro's urgency to launch in the July window, a fresh NOTAM (notice to airmen) - an alert issued ahead of every launch - has been issued on July 15. The alert is effective on July 17 between 2.30am and 3.30am, and for July 18 to 31 between 2pm and 3.30pm.

[chetak]

per the deccan herald

Chandrayaan 2 next earliest launch date is July 21, 22



The Indian Space Research Organisation (ISRO), after postponing the Chandrayaan-2 launch, is looking at the earliest available window for the rescheduled launch to happen. The new launch date is now planned for as early as July 21, i.e. Sunday afternoon, or the early hours of July 22, i.e. Monday.

[Mort Walker]

^^ashokk, this is an interesting post, looking back in time, I used to scorn at these S joints, welding in our initial engineering sems, I was not alone.
Wish I was aware of BRF and ulanbator then.

The problem now is that they are racing to fly with a just-learned solution, implemented for the first time. If there is a failure there will be incredibly loud screaming. If this joint leaked because of the cold of the LOX tank, what happens to the helium tank used to flush the LH2 tank, after many minutes of exposure to that? That is like 6K vs the 183K of LOX.
There goes another ambition for when I grow up: Flight Director, GSLV-10/Chandrayaan-12.

It maybe just learned, but pre launch parameters will indicate if pressure is holding in the He, LOX and LH2. ISRO solution should work and the launch of GSAT-22 on the next GSLV Mk. III. It’s not ideal, but we move on and do the best possible. Engineering solutions for deployed systems are often hardware and software patches.

[ramana]

UB, Its possible that the problem is due to scale.
The C-7.5 based on KVD-1 had a smaller LOX tank.
And may be the cold sink did not shrink the joint.
However C-20 has much bigger LOX tank and hence the shrinkage is more and damaging to the rigid joint.
I guess a flexible joint would have mitigated along with relocation.

This is a detail engineering issue not a big physics issue.


I concur that quick fix of implementing the lessons learned should be only for this flight.
The good thing is with their low rate of production, ISRO doesn't have too many engines to remediate.

BTW the 'source' is wrong KVD-1 was not built in qty. In fact it was dusted off and under production with ISRO contract in 1992 after FSU collapse. One more reason for the US umbrage.

Mort your last line works in computer industry and not 9 sigma products like deep space vehicles and strategic weapons.


I hope they make proper hardware change after this mission.
Its interesting that the issue did not show up in the ground test version and the earlier two C-20 stages.

Can some one put a picture of a rigid and flexible cryogenic joint?



Crossing fingers for 21 July launch.

[ramana]

Cutting corners and using Jugaad with shoe string budgets can only go upto a certain point --- as we cross the boundary of serious space exploration from relatively simple satellite launch--- you have no choice but to invest serious money

ISRO comes under PM with its own minister of state.
There will be adequate funding from now on.
No more shoe string budget to ensure there is margin.

[UlanBatori]

What is the little rocket strapped at the bottom of each booster?
I didn't realize that the main Vikas liquid rocket does not ignite until 114 seconds into launch, just 26 sesconds before booster dropoff. Seems a big waste, not to fire the liquid engine at liftoff. This must be the part about dropping the first stage (boosters) before doing serious horizontal acceleration.
Also, strapping on a couple more boosters should be possible with the same diameter stack, hain? So the payload can be boosted a good deal. We need those aerodynamic-glide boosters to get away from these limitations.

[Mort Walker]

Ramana,

You’ll be surprised on already deployed aircraft and weapon systems, there are a number of hardware engineering changes done to keep them fielded and operational. Add an RLC filter here and there, snip some resistors and off you go.

[prasannasimha]

The cryogenic stage is actually self pressurized so if the Hrlium tank failed the mission **may** have still been succesful ( the annoyncements from ISRO sort of confirm it). However they havevused Helium aa ullage pressutizing ahent as precaution or some specific reason so they qould not like to take a chancr.
Snother thing is this rocket will be the one going for GSP so they would take extra precautions to see no catast.ophic failure occurs.
All space agencies have had problrms.
People forget the recent catastrophic explosions of the Falcon eocket and Long March.
Its a part of rocketry - after sll its a contolled explosion