Others have questions too.Emily Lakdawala http://www.planetary.org/blogs/emily-lakdawalla/2013/11110806-mars-orbiter-mission-update.html
..., it's not clear to me whether both primary and backup valves to their main engine were supposed to be operated together, or if that was a mistake, or if it was a surprise that it didn't work to operate them together. "As one of the planned modes" makes it sound like it was intentional (or, at least, that it should have worked), but evidently it didn't work to operate them together. And why did the flow of fuel to the engine stop? Because the spacecraft detected a problem and stopped it, or because (for some reason) flow didn't proceed with both valves commanded to operate at the same time?
At least, when flow stopped, it sounds like the spacecraft successfully detected that and attempted "thrust augmentation" by using the attitude control thrusters to support the planned orbit maneuver. That is good logic to have in place when you are planning a must-not-fail event like a planetary orbit insertion maneuver. However, the final sentence is concerning, because it sounds like the augmentation with the attitude control thrusters did not accomplish what it should have. Rather than increasing the spacecraft's velocity, "This sequence resulted in reduction of the incremental velocity." That sounds bad for two reasons: it sounds like the autonomous function didn't accomplish what it should have, and it also means that precious fuel was wasted. If the orbit adjustment maneuver had simply been an underburn (the main rocket didn't fire for long enough), then there would have been no cost to fuel reserved. But if the attitude adjustment rockets actually reduced the spacecraft's velocity, that would have cost fuel.
That's where I cam coming from. It's the fuel that concerns me.
I get the warm versus hot redundancy but wouldn't the system have interlocks to ensure that either the primary or the redundant valve works - not both together. An XOR situation?
Or Maybe they [ISRO] meant to say "This sequence resulted in reduction of the [planned] incremental velocity," explaining why they only got 35 m/s of increased velocity instead of the planned 130. I'm not sure. So I don't know whether we have two anomalies or just one. Regardless, ISRO is unconcerned enough to proceed with a supplemental burn immediately
This would be a nice outcome.
"While this parallel mode of operating the two coils is not possible for subsequent operations, they could be operated independently in sequence." - ISRO statement
Again, I am left wondering if it was a surprise to mission operators that it did not work to operate both the primary and backup valves to the main rocket engines at the same time. Looking to media reports for quotes from officials makes it seem as though it was a surprise, but one that they say isn't a problem because they won't need to do it in the future. (If that's true, then why test it?) Here are a few statements:
However, from http://www.bbc.co.uk/news/science-environment-24900271
"In that redundancy test, two coils in the liquid engine were supposed to be energised simultaneously....Mr Bagla told BBC News that the attempt on Monday morning used up about 2kg of the craft's 852kg fuel load. But he added that the spacecraft's insertion into Earth orbit after launch on 5 November had been so precise, 6kg of liquid fuel had been saved. Even with Monday's glitch, the mission still had a fuel surplus of 4kg."
- So its a glitch but the PSLV's precision has provided a fuel buffer.
Unofficial confirmation about the glitchhttp://blogs.wsj.com/indiarealtime/2013/11/11/first-hiccup-for-indias-mars-mission/
The fault was discovered when two coils in the satellite, which are responsible for speeding the satellite up and slowing it down, were turned on at the same time. This led to a blockage of fuel and oxidants to the main liquid-rocket engine. 'The satellite’s engine doesn’t work when both coils are simultaneously on,' a spokesman for the ISRO told The Wall Street Journal. 'This is not at all a setback, we got our redundancies [backup plans] checked by this process,' said the spokesman, who declined to be named. He said it was not necessary for both coils to be on at the same time during the rest of the flight plan. [So why test it?]"