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The 4th orbit raising manoeuvre of ISRO's Mars probe (MOM or Mars Orbiter Mission, informally called Mangalyaan) did not go as planned, as the LAM (Liquid Apogee Motor) shut down prematurely. According to ISRO:

However, when both primary and redundant coils were energised together, as one of the planned modes, the flow to the Liquid Engine stopped.

  1. What was the root cause of this failure?

  2. Was this redundant mode tested on ground before launch?

  3. Will ISRO be uploading a software patch to ensure redundancy at MOI (Mars Orbit Insertion)?

Assuming that both primary and redundant coils can be energized independently, but not together, for operation of the valve, one cause of this anomaly which I could think of is, that the coils are wound in opposite directions. Or the current to one of the coils is being fed in opposite direction, maybe because the terminals got connected in the wrong order, thus resulting in cancellation of magnetic flux / force.

update ( to expand the question ) Why have redundant solenoid coils but not redundant valves? Is it not more likely that mechanical components ( valves ) are more likely to fail than the electrical components ( coils )?

Also what is the intention of energizing the coils together:

  1. Extra force in case the valve is stuck or sluggish?

or

  1. To open the valve wider for more thrust?
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Dr. Kiran Kumar of ISRO, in his speech at IITG Ahmedabad has confirmed that the magnetic fields of the coils cancel each other when energized together. This was (fortunately) found in earth orbit, during the fourth orbit raising manoeuvre.

http://www.youtube.com/watch?v=l_e7L0nJTQw#t=392 ( from 5:02 onwards )

I believe this confirms my original guess on the cause of failure:

"one cause of this anomaly which I could think of is, that the coils are wound in opposite directions. Or the current to one of the coils is being fed in opposite direction, maybe because the terminals got connected in the wrong order, thus resulting in cancellation of magnetic flux / force."

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