Indian Space Program: News & Discussion - Sept 2016

Mort Walker · Post by **Mort Walker** » 31 Aug 2017 21:31

Singha wrote:at present i have heard 1 of the 7 IRNSS sats is malfunctioning and this launch was hoped to fill that gap.

The malfunction of the rubidium clock. I hate it when atomic clocks fail. Makes for bad synchronisation.

Singha · Post by **Singha** » 31 Aug 2017 22:23

my guess is cold gas thrust is used for fairing separation not pyrobolts.

prasannasimha · Post by **prasannasimha** » 31 Aug 2017 22:37

Singha wrote:my guess is cold gas thrust is used for fairing separation not pyrobolts.

It is a zipcord charge
Prasanna

Singha · Post by **Singha** » 31 Aug 2017 22:52

thanks..so like some airplane canopies i guess. these rubidium clocks do we make it inhouse or import ?

must be similar to this i suppose

Mort Walker · Post by **Mort Walker** » 31 Aug 2017 22:58

Rubidium clocks were imported from a European company. The one on Mangalyaan was made in India in house. Cost of one clock with associated electronics is around $5K. Even if it cost 10 times more to make in India, it is certainly preferable to launching and losing another satellite and wasted PSLV.

Kakarat · Post by **Kakarat** » 31 Aug 2017 22:59

Singha wrote:thanks..so like some airplane canopies i guess. these rubidium clocks do we make it inhouse or import ?

must be similar to this i suppose
http://i.stack.imgur.com/lQPqg.jpg

Import from Spectratime of Switzerland
Indigenous clock is under development

Mort Walker · Post by **Mort Walker** » 31 Aug 2017 23:40

From what I understand it is not the clock itself but the associated electronics bought from the company.

ramana · Post by **ramana** » 01 Sep 2017 01:15

JTull wrote:Haze Removal Algorithm developed for Cartosat Images

Wow awesome algorithm!!!

PSLV failure will be investigated. Essentially the Fairing did not separate.

Lets see.

Amber G. · Post by **Amber G.** » 01 Sep 2017 01:30

Mort Walker wrote:Rubidium clocks were imported from a European company. The one on Mangalyaan was made in India in house. Cost of one clock with associated electronics is around $5K. Even if it cost 10 times more to make in India, it is certainly preferable to launching and losing another satellite and wasted PSLV.

From what I know - One can get Rb clocks for even less, I have seen them on eBay for a few hundred dollars but with a $5K clock one can not do a Halfele-Keating type experiment on your next trip. ( Halfele-Keating used atomic clocks on a commercial air plane and saw relativistic effect on clocks (see << this > ..I want ordinary physics student to be able to do this as a lab

..

Again from what I have seen (or checked a few years ago) stability for available Rb clocks varies from the order about - 1 Year df/f 10^(-9) (cost about 1K) to 10^(-15). (price about $250K).. those which are "space certified" are normally costs 10X time the normal.

(Of course, prices over last few years may have come down and depends on lot of other factors than stability alone... lot of other factors go into effect to select the clocks).. Who knows Yb or even Sr type clocks may find some market.

Mort Walker · Post by **Mort Walker** » 01 Sep 2017 01:41

AmberG,

In the defense and aerospace industry, the $5K rubidium clocks are available, though they are not space certified and you're correct about being 10 times more. For any time dilation test I would be using a NIST certified cesium clock. The whole purpose of the rubidium clock is to get a very stable 10 MHz reference. From there you can upconvert without error to the L and S band frequencies needed for the navigation satellites.

Some properties of a clock you look for is aging in operation, phase noise close in frequency offset, package size and current draw. I buy my clocks from Wenzel Associates in Austin, TX.

Amber G. · Post by **Amber G.** » 01 Sep 2017 05:15

^^^ Just curious - how (quantitate terms) stable are those clocks?
***
(For GPS , one of course needs VERY stable clocks over a long period unaffected by temperature, EM- field and mechanical vibrations)
(Standard reference clocks on earth are laser cooled, and are stored in EM-shield etc)

***
From basic physics - (Assume that electronics is perfect and not introducing any additional error) Factors for Rb clocks in satellites (vs Cs clocks) -
Among other factors..
-- At typical temperatures in sats Rb has a lower vapor pressure making resonance effects little harder to observer (compared to Cs)
-- Cs has only one stable isotope (Cs133) so getting a really pure gas is easier. For Rb for real accuracy (so that hyperfine lines are thinner) isotopic separation is required.. adding to cost.
-- Rb hyperfine transition is not as large as Cs - (Cs has better Q fro resulting resonator)

Of course, at present the unit of time - second is defined by Cs transition .. so by definition it is standard. (It does show better intrinsic accuracy - about 100x times) and no aging effects. Rb clocks still have to "check" against standard to calibrate the drift.

This is a little dated, but basic fundamentals are still valid and some may find it interesting ..(from a forum of manufactures' of such clocks)

http://www.chronos.co.uk/files/pdfs/its ... y_2007.pdf

ramana · Post by **ramana** » 01 Sep 2017 05:23

The PSLV issue looks like ordnance for shroud separation failure. Could be in installing the ziptube in the shroud.

Mort Walker · Post by **Mort Walker** » 01 Sep 2017 05:35

Stability is better than 10^-10, phase noise is below -165 dBc/Hz @ 100 KHz. Usually these are Rb with an OCXO.

Cs clocks are larger, heavier and require more power. Putting on aircraft and spacecraft becomes a design challenge. All other electronics of the bird have life issues and won't last more than a decade. So if clock degrades to less than 10^-9 in 20 years, designers can live with it as other parts will have long failed by then.

juvva · Post by **juvva** » 01 Sep 2017 10:57

Mort Walker wrote:
Karthik S wrote:How long it'll take for next launch?
I wouldn't jump the gun.

Find out if it is a payload loading failure or an actual fairing separation issue. How does the fairing actually separate? Is it with pyro explosives or some other method?

This appears to be a $35-$50 million loss. An expensive loss for a country like India.

Yes.An expensive loss...unless the launch and/or satellite were insured ?

Amber G. · Post by **Amber G.** » 01 Sep 2017 11:09

This PSLV was to carry both the Team Indus and Hakota rovers to the moon for the Google Lunar XPRIZE. The competition has recently pushed back its deadline, so ISRO/they may still have enough time.

Mort Walker · Post by **Mort Walker** » 01 Sep 2017 17:47

The implication here may be a payload loading engineering problem that could affect not just the PSLV, but the GSLV too. The Google XPrize is one issue, but failure of Mangalyaan II would be a real technical and scientific set back.

ArjunPandit · Post by **ArjunPandit** » 01 Sep 2017 23:48

shiv wrote:
ArjunPandit wrote:there should also be an investigation of chinese angle as well. They may be extracting revenge for Doklam
This is revenge - how?

For possibility of some kind of cyberattack or cheap chinese parts by any of the private vendors

disha · Post by **disha** » 02 Sep 2017 19:36

Firing mechanism got triggered but did not fire., this could be a parts or install procedure issue.

An easily recoverable setback.

Achieving reliability for space launches is difficult.

vasu raya · Post by **vasu raya** » 03 Sep 2017 00:40

There is so much space debris that actually making this heat shield collide with one the right size and velocity will break it open?

kit · Post by **kit** » 03 Sep 2017 01:43

An easy but expensive solution. Get the Americans to use the robotic arm in their shuttle to pry it open .. the shuttle has a lot of missions going on i think. We need doctor satellites in the polar and Geo orbits with rotbotic arms to tend to ailing /wayward satellites.

kit · Post by **kit** » 03 Sep 2017 01:45

Also curious as to how " malfunction " can happen .. if it's an electronic signal from the ground that activates the firing mechanism can it be spoofed?

kit · Post by **kit** » 03 Sep 2017 01:49

JTull wrote:Haze Removal Algorithm developed for Cartosat Images

Wonder what the actual resolution is

Maybe we can see what the abduls are doing on the other side

.. live in action

Mort Walker · Post by **Mort Walker** » 03 Sep 2017 02:12

kit wrote:An easy but expensive solution. Get the Americans to use the robotic arm in their shuttle to pry it open .. the shuttle has a lot of missions going on i think. We need doctor satellites in the polar and Geo orbits with rotbotic arms to tend to ailing /wayward satellites.

The US space shuttle program has shut down. All shuttles remaining are museum pieces. The rocket boosters are all gone too.

Mort Walker · Post by **Mort Walker** » 03 Sep 2017 02:16

disha wrote:Firing mechanism got triggered but did not fire., this could be a parts or install procedure issue.

An easily recoverable setback.

Achieving reliability for space launches is difficult.

What caused it not to fire? Does it have some sort of altitude based fuse system which kicks in at 3rd stage ignition. Or it didn't fire due to payload loading? The fairing seperation mechanism could be an issue on other ISRO rockets too. Proceed with caution I would say.

kit · Post by **kit** » 03 Sep 2017 02:23

Mort Walker wrote:
kit wrote:An easy but expensive solution. Get the Americans to use the robotic arm in their shuttle to pry it open .. the shuttle has a lot of missions going on i think. We need doctor satellites in the polar and Geo orbits with rotbotic arms to tend to ailing /wayward satellites.
The US space shuttle program has shut down. All shuttles remaining are museum pieces. The rocket boosters are all gone too.

Was referring to the X 37 B unmanned space shuttle .. it has a quite active schedule !! though mostly military operations

ramana · Post by **ramana** » 03 Sep 2017 04:48

disha wrote:Firing mechanism got triggered but did not fire., this could be a parts or install procedure issue.

An easily recoverable setback.

Achieving reliability for space launches is difficult.

Disha, Was this reported in press? Wouls tie in with my above post.

ramana · Post by **ramana** » 03 Sep 2017 04:52

Mort,
Ordnance train is very, very finicky. By reviewing telemetry they can figure out electric signal was sent. Other telemetry will confirm if ordnance was functioned. Usually from vibration and or acceleration sensors in the equipment bay. Shroud separation will have unique signature. Could be absent indicating non function g
Also acceleration data could be lower indicating heavy weight. So let's see.

ramana · Post by **ramana** » 03 Sep 2017 04:55

Arjun Pandit,
While doing root cause one should throw in all causes but usually the simplest cause that explains the signature and fixing will eliminate the issue is the true root cause.

Cyber attack is se*y but not plausible as most signals will be analog.
Thanks but no thanks.

disha · Post by **disha** » 03 Sep 2017 08:44

ramana wrote:Disha, Was this reported in press? Wouls tie in with my above post.

Firing separators for shield separation is a one time event., even though the software has redundancies built in to give firing commands based on its INS or time from launch etc., the actual firing is a one time event which is destructively tested on a sample from a batch. Given that the heat shield did not separate., it points to "quality issues" within that batch or overall.

How does the heat shield separate? In simple terms, computer relays the command which is like a switch throwing on the light. Software is ground tested and has several redundancies and each path can be tested and it worked on some 35 PSLVs. The switch can also be ground tested several times*. Once past those steps, it is the electric circuit and the final is the firing mechanism. It is the firing mechanism which is always destructive (of course) and is tested as a component from a batch. There is always the case where similar "detonators" in the same batch might have gone bad, mishandled, mis-"attached", mis-configured resulting in a failure.

It will be too early for ISRO to confirm., but all reports from news also converge to that. I heard the news and immediately mind raced through the above steps and came here an posted., also saw Ramana' saar's independent analysis coming to similar conclusion.

Half of the news after that were doing the usual rona-dhona and then I ran into this link: http://www.financialexpress.com/lifesty ... ad/837748/

Here are the operative paras that I latched on immediately:

Noting all the commands are pre-planned and built into the computers, he said that there cannot be any manual command. “The computers have to give the necessary commands. The commands have to be relayed by the electrical circuits. The pyro circuit has to get initiated which, in turn, has to cut the mechanical elements so that the two parts of the heat shield get separated,” he said.

Prasad maintained that something could have gone wrong in this four-step sequence or in the sub-systems, as redundancies have only been built into some systems. “The computer programmes may have several redundancies to take care of an eventuality. So they can be tested on ground before and also during preparation for the flight. The electrical circuits and some pyro elements will also have redundancies.

“A rocket has several one-time operation systems. Such systems cannot be pre-tested and cannot have redundancies. Only sample tests can be made with items manufactured in that batch. And then a system is used in the rocket,” he said, terming the one-time operation systems “the riskiest items” in any rocket.

What I like about the above article is a clinical description of issues without the usual rona-dhona. Like:

Incidentally, the launch of the first navigation satellite IRNSS-1A was also postponed from its original launch date after a problem was discovered in one of the electro-hydraulic control actuators in the rocket’s second-stage engine.The second stage had to be dismantled to replace the actuator, which is an assembly of several components. It weighed around 20 kg. ISRO also had earlier dismantled a fully-assembled PSLV rocket to check a component in the rocket’s second stage.

In 2010, a fully-assembled PSLV rocket was dismantled to replace a gas motor in its second-stage engine. The gas motor powers the rocket’s second-stage control actuators for manoeuvring the engine’s nozzle — a process called gimballing, which enables the rocket to maintain a steady course on its way up.

*When I say "switch", the analogy is to bring it closer to what we know in our daily experience. The actual "switch" on PSLV will be a hi-tech electronic switch.

** Another news did say that the payload fairing separation command was issued. I have to dig that article out.

Added later., here you go:

http://www.thehindu.com/sci-tech/scienc ... 611531.ece

The fairing on the PSLV- C39 was programmed to separate from the vehicle three minutes into the flight but the rocket continued to travel with the satellite trapped inside, dragging down the velocity.

Based on the initial inference, informed sources at ISRO said the command for separation had gone through but failed to trigger the mechanical process that pops open the heat shield. They said the investigations were likely to centre on the electrically-initiated pyro devices that initiate the sequence of separation.

Pyro devices use explosive energy generated by charge ignition to sever the components and actuate a release mechanism to push the fairings apart.

What is intriguing for scientists is that the pyro device which probably malfunctioned, is based on an electro-mechanical process, one that is far less complex than thousands of other components in the rocket.

disha · Post by **disha** » 03 Sep 2017 09:06

Mort Walker wrote: What caused it not to fire? Does it have some sort of altitude based fuse system which kicks in at 3rd stage ignition. Or it didn't fire due to payload loading? The fairing seperation mechanism could be an issue on other ISRO rockets too. Proceed with caution I would say.

The word I was searching for the component was "electrically initiated pyro-devices"., they are basically simple detonators. Those devices either work or they do not work. And they can be tested only once since they are destroyed on testing. See my note above.

The software that initiates the ignition has several redundancies., like liased to INS or time delay from launch or altimeter based firing. And this can be tested several times on ground with appropriate simulation. Issue here is least likely. Also the fairing separation mechanism itself can be tested several times., there are videos of it being tested by ISRO. That leaves the pyro-devices by itself and as indicated earlier - they are destructively tested for a sample from a batch.

Mort Walker · Post by **Mort Walker** » 03 Sep 2017 09:15

^^^It almost sounds like a bad relay switch. Command given, but relays didn't actuate.

disha · Post by **disha** » 03 Sep 2017 10:52

Mort Walker wrote:^^^It almost sounds like a bad relay switch. Command given, but relays didn't actuate.

It could be., but my bet is on the pyro-device that further detonates the explosives to separate the payload fairing.

kit · Post by **kit** » 03 Sep 2017 18:58

Let's get a bit wild out of the world scenario. . Would it be possible for the Chinese to capture this ( they do have a space station though the capture mech might be variable) .. any use to them ?

vasu raya · Post by **vasu raya** » 03 Sep 2017 21:51

An old question, aren't relay switches which rely on induction to operate susceptible to EM pulses strong enough to either activate them or fry them

kit · Post by **kit** » 03 Sep 2017 21:58

vasu raya wrote:An old question, aren't relay switches which rely on induction to operate susceptible to EM pulses strong enough to either activate them or fry them

and that question, in turn, begs another question ..why did the atomic clock malfunction in the first place?

once can be an error, twice not likely ?!

kit · Post by **kit** » 03 Sep 2017 22:00

why not get GPS transponders for "all" indian satellites parked in suitable orbits instead of dedicated ones ?? .. more there are greater the redundancy

vasu raya · Post by **vasu raya** » 03 Sep 2017 22:05

They mentioned the use of I-1k bus for the IRNSS sats, while all new built ones are probably are using different bus

Mort Walker · Post by **Mort Walker** » 04 Sep 2017 06:22

vasu raya wrote:An old question, aren't relay switches which rely on induction to operate susceptible to EM pulses strong enough to either activate them or fry them

Those relays are space rated and well shielded. Relays do fail for electromechanical reasons. It could be that the pyro explosives simply didn't detonate.

vasu raya · Post by **vasu raya** » 09 Sep 2017 22:04

They have predicted two months of orbiting before the last stage hits the lower atmosphere, so instead of helplessly watching, can they use the exo version of the ABM, the PAD to pepper special sharpnel so they get embedded into the payload fairing which is mostly random, special in the sense they are charges with accelerometers that can be triggered from a ground station.

once attached one can study the accelerometers data from each charge and try to correct the tumbling as well as split open the fairing by selectively choosing the charges to explode. In the next stage they can use the electric thrusters as I believe the fuel is depleted, even if it takes 6 months to a year to reach its designated spot.

Indranil · Post by **Indranil** » 10 Sep 2017 04:48

^^^ Will the above movie also have Liv Tyler, If yes, I will love to watch it too.