Amber G. wrote:
Barathji - I sincerely suggest - if you have time and interest
and basic physics understanding
check out my one year old posts saythis
Please, no ji for me
Thanks for the links, but those links are irrelevant AFAIK. While background is useful, discussions of Chandrayaan trajectory going off-base start from around page ~20x
===> Trajectory is hardly "out of control" or space craft is hardly off the path .... .
We have a failure in communication. I do not understand how trajectory
during fine braking phase below 2 km can be described as nominal/or in control. Around and subsequent to that is what we are talking about (though some deviance and root cause can predate it). In this period, the spacecraft attitude (due to guidance/control) and thrust are possibly not in nominal. There's been unconfirmed reports of tumbling and of excessive braking thrust [Again Isro has not posted the actual failure / root cause analysis report, let alone failure sequence so one cannot contradict it]
We're not talking about things upto the rough braking phase end..
When all is said and done: Vikram was within one of the site chosen by ISRO weeks before. It selected/chose the final landing place and landed *exactly* at the landing point.
The spot indicated was within 500m with debris flung over 750m or more. Now you could say it is well within the margin of error. But the telemetry was received for most of the descent. So I'm hoping that the data in combination with simulations, one could usefully reconstruct parameters and actions in the last 2 km that are best fit . Maybe, maybe not. /shrug.
Now Apollo 11 ran 4 miles downrange and about 1 1/2 minutes earlier, based on 40 sec longer powered distance, and Armstrong's manual operation/intervention. But that was a different era in guidance and precision. So possible ?
==> I gather from your comments that you may not be aware -- But Vikram's final moments are not like a plane/drone/missile getting off target on earth. Ironically if there was air on the moon, the landing would be a child's play.
No air !?! Maybe there is water instead ! In fact I remember Chandrayaan-1 with NASA M3 discovered water. So one should send ships instead of spacecraft ! That's why the failures ! Nobel prize if someone confirms that there is no air ! Hey, how about this sail ship
? /sarcasm /joke
([b]no, trajectory did NOT go out of control)
I think we have a failure
to communicate. Braking engine thrust, thrust variations and loss of guidance/loss of refined attitude/guidance might result in small deviations in trajectory and landing point. Maybe this is completely swamped by normal tolerance and errors, maybe not ?
..Most likely inertial guidance system couldn't keep the bearings straight - or glitch in the computer / .. it's altimeter or in its obstacle avoidance camera etc. (My guess, the primary reason was inertial guidance system losing a gimbal type lock and computer was not fast enough to resolve it - (Disclaimer: ISRO has not confirmed the root cause ) hopefully they will resolve it in the next one)
Quite possible. IIRC,there was discussion about "hunting" behaviour before..from about 4-5km on down. A public failure report (with root cause) published would, hopefully, be unambiguous.
===> This was NOT unexpected . Most of us (and in ISRO) were hoping that it may work but knew that virtually every other attempt like this in the past resulted in a failure.
ISRO allowed the hype to build up where Vikram/Pragyan was perceived as the standard for success and failure. The "sexy" overrode a more rational and realistic sense.
ISRO did NOT invest too much in Vikram's other pay load (They did not include even a RTG) as they were not really sure that it will succeed but hoped it will give enough data for the next mission.
Would you have insight into the different payload options considered and how they were chosen? That would be pretty interesting. All I am aware of now was payload restrictions/risk that were re-visited after Russian feedback and move to GSLV III
Also, since you are apparently concerned about explaining things for the n'th time and that maybe I'm just doing this for debate - no more posts for some time from me