Author Topic: FAILURE: IRNSS-1H, PSLV C39, SLP, August 31, 2017 (13:30 UTC)  (Read 67859 times)

Offline input~2

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Two objects now being tracked.

42928  51A    163 x 6539 km x 19.15 deg
42929  51B    175 x 6515 km x 19.15 deg

Too early to speculate usefully on what's going on with that.
and now a third object ::) apparently something has separated..
(epoch September 2, 04:54 UTC)
42930 51C    173 x 6468 km x 19.14 deg

Offline Steven Pietrobon

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Team Indus says the problem was the pyro device circuit.

https://medium.com/teamindus/in-isro-we-trust-8ce42f6c7c78

"The glitch reported appears limited to a pyro device circuit in the nose-faring with all other systems working as they should."
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Ben the Space Brit

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My concern is whether the PLF will absorb just enough thermal and aerodynamic load as the vehicle descends that IRNSS-1H might be released into the middle or lower atmosphere at a low enough speed to survive the descent to the surface largely intact.
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Offline input~2

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Decay dates from SatEvo:

C:                              late October 2017
B (PSLV DEB):           around Christmas 2017
A (IRNSS 1H/PSLV):   early July 2018

Online mn

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1 tonne of extra weight doomed PSLV mission

Quote
The PSLV-C39 rocket, which failed to launch the IRNSS 1H satellite on Thursday, was dragged down by at least one tonne of extra weight from the unseparated heat shield after the second stage, its velocity reduced by one kilometre per second. This greatly reduced the altitude it was to reach for a successful mission, say scientists privy to the project.


So the mission failed because the rocket failed to reach proper orbit, hmm so interesting.

Silly me I thought it failed because the payload was trapped inside the fairing.

Online vineethgk

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http://www.thehindu.com/sci-tech/science/isro-scanning-data-on-pslv-c39-failure/article19611531.ece?utm_source=RSS_Feed&utm_medium=RSS&utm_campaign=RSS_Syndication

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The Failure Analysis Committee, headed by VSSC Director K.Sivan, is poring through the flight data of the mission in a bid to understand what went wrong. Dr.Sivan toldThe Hindu that a simulation exercise would be carried out to zero in on the exact reason. “We are on track and hope to reach a conclusion within a week,” he said.
Quote
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.
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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.

Offline worldtimedate

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Weight issue not linked to PSLV heat shield glitch: Isro chief

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Isro chairman AS Kiran Kumar on Saturday firmly denied that the PSLV-C39 rocket carrying eighth navigation satellite IRNSS-1H failed on Thursday as it was carrying one-tonne extra load. A report in TOI on Saturday had stated that "the PSLVC39 rocket, which failed to launch the IRNSS-IH, was dragged down by at least onetonne extra weight". The report stated that this was more than the design permitted.

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Speaking to TOI on Saturday prior to making a presentation at the Nehru Centre in Mumbai, the Isro chief said: "The report is incorrect and the rocket was not carrying any extra load." He said the heat shield added additional weight to the launch vehicle as it failed to get detached at the second stage and went along till the fourth stage separation point. "It was not because Isro put any additional weight prior to the launch," he said.

Quote
He added that a portion of the rocket with the satellite enclosed in the heat shield was currently orbiting 163km x 6,600 km and was being tracked by the multi-object tracking radar at Satish Dhawan Space Centre, Sriharikota. "It is expected to remain this way for another 25 days,'' he said. Kiran Kumar said a failure analysis committee was being formed to study the setback.

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Dr K Sivan, director of Thiruvananthapuram-based Vikram Sarabhai Space Centre (VSSC), said, "Launch failure will not affect future missions as they will go as planned. But corrective measures will be taken in future for all types of vehicles as the heat shield separation mechanism is similar in all launchers."

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Offline maint1234

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HEAT SHIELD SEPARATION
 
The primary function of heat shield is to protect the payload and other sensitive system of launch vehicle from the aerodynamic and thermal loads during its ascent phase of flight and to provide the aerodynamic shape and thereby reduces the aerodynamic drag.  After meeting the functional requirements the heat shield should be separated from the launch vehicle as early as possible.  The system used for separation should impart necessary jettisoning velocity to achieve collision free separation. The heat shield is usually made in two halves and attached through separation system.  The velocity required for safe separation depends on the heat shield diameter, mass, flexibility and the state of motion.  However as the diameter and length of the heat shield goes up flexibility plays a major role in safe separation.  Also for many vehicles the heat shield separation takes place in thrusting phase.  All these factors necessitate a larges separation velocity and jettisoning system to impart this velocity as quickly as possible.  For these reasons the PSLV and GSLV have adopted a zip cord as jettisoning system for vertical separation.  The separation dynamics of heat shield is studies by combining the rigid body as well as flexible motions of the fairings using finite element method.
Fig [5] – HEAT SHIELD SEPARATION

Offline maint1234

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Offline Arch Admiral

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The use of the term "heat shield" for the component that failed on this launch is incorrect and confusing. A heat shield protects spacecraft during reentry, a payload shroud protects them during launch. They are physically very different.

Offline zubenelgenubi

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The use of the term "heat shield" for the component that failed on this launch is incorrect and confusing. A heat shield protects spacecraft during reentry, a payload shroud protects them during launch. They are physically very different.

Related question: What will they call the heat shield when they start flying crewed capsules or other spacecraft?
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Offline jcm

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The use of the term "heat shield" for the component that failed on this launch is incorrect and confusing. A heat shield protects spacecraft during reentry, a payload shroud protects them during launch. They are physically very different.

That's the modern US usage. However, it wasn't always that way. The 1960s NASA Scout launch vehicle's nose
fairing was always referred to as its heat shield. And it's clearly not incorrect, in that it does shield the payload
from the heat (ok, and ram pressure) of ascent.

I have the impression that Langley used 'heat shield', Marshall used 'nose cone', and the west coast used 'payload fairing', but it may not have been that systematic. In the US, terminology eventually standardized on 'payload fairing' for the forward heat shield and 'heat shield' for the reentry heat shield. But that's US English.  Indian English is perfectly
free to standardize on a different usage, and has done.
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Offline FutureSpaceTourist

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All propellant aboard PSLV fourth stage and IRNSS-1H has been vented. Accurate reentry location determination would be possible a week in advance.

https://www.reddit.com/r/ISRO/comments/6y48ax/all_propellant_aboard_pslv_fourth_stage_and/

Offline jgoldader

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All propellant aboard PSLV fourth stage and IRNSS-1H has been vented. Accurate reentry location determination would be possible a week in advance.

https://www.reddit.com/r/ISRO/comments/6y48ax/all_propellant_aboard_pslv_fourth_stage_and/


Would be interesting to know how they managed that.
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Offline Ben the Space Brit

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The stage 4 was always intended to burn to exhaustion. However, given that they cannot have had communications with IRNSS-1H whilst it was still in the PLF, I am sceptical that they were able to vent its prop tanks. We probably have either a mistranslation or someone lower down the chain in IRSO telling their top echelon what they want to hear.
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Offline s^3

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Yes, 4th stage vent is understandable but where will the 1H propellent disperse even if it could be commanded to do so?
« Last Edit: 09/05/2017 01:41 PM by s^3 »

Offline maint1234

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“we have depleted all the propellant through the gap in the heat shield and the fourth stage.” Dr K Sivan Director VSSC
As per reddit above.

Offline input~2

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Decay dates from SatEvo:

C:                              late October 2017
B (PSLV DEB):           around Christmas 2017
A (IRNSS 1H/PSLV):   early July 2018
Revised decay dates from SatEvo with latest TLEs (epoch > Sept 4, 22:48 UTC)

C (PSLV DEB)           early November 2017
B (PSLV DEB)           early November 2017
A (IRNSS 1H/PSLV)  mid-August 2018

Offline jcm

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“we have depleted all the propellant through the gap in the heat shield and the fourth stage.” Dr K Sivan Director VSSC
As per reddit above.

Interesting. Looks like there may have been a change in the decay rate around third apogee (2000 UTC Aug 31),
about when the two debris objects seem to have come off.
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Offline StevenV

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Could the sat have been configured to auto-passivate on battery failure?

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