Chandrayaan-2

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Discussion

Eric Mc

122,037 posts

265 months

Saturday 7th September 2019
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I bet they will have a good idea eventually of what went wrong. There will have been a whole heap of telemetry broadcast from the lander as it approached and going through that data might give them a good idea as to what happened. WHY it happened might be more difficult to find out.

The problem is that landing tends to be a very hectic period with all sorts of events crammed together in a fairly critical sequence. If any one of those events does not happen correctly or on time or at all, the result will normally be a hard impact.

snake_oil

2,039 posts

75 months

Saturday 7th September 2019
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I'm probably incorrect but listening to the commentary last night from India TV they were seeming to imply that a 5th engine was supposed to fire, which did not, and that this was untested? Really?

Eric Mc

122,037 posts

265 months

Saturday 7th September 2019
quotequote all
Not unusual for these types of engines not to be pre-tested before flight. The Apollo Lunar Module ascent and descent engines were fired for the first and only time during their use on each actual mission.

There was a reason for this. The propellants used were hypergolic and so corrosive that the very act of pushing them through the pipe work, combustion chamber and nozzles meant that those components suffered corrosive damage and could not be used again.

I bet the engines on this Indian lander were of a similar type.

It does not mean such engines weren't tested on earth, it just means that the actual "flight" engines would not have been test fired before the mission.

snake_oil

2,039 posts

75 months

Saturday 7th September 2019
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Interesting, thanks!

eharding

13,723 posts

284 months

Monday 9th September 2019
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The Indians have found Vikram on the surface.

Given that they're trying to communicate with it, Vikram didn't smear itself all over the landscape either.

snake_oil

2,039 posts

75 months

Monday 9th September 2019
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eharding said:
The Indians have found Vikram on the surface.

Given that they're trying to communicate with it, Vikram didn't smear itself all over the landscape either.
I was reading the last known vertical velocity was in the region of 60m/s hence it's likely it went in pretty hard.

Beati Dogu

8,894 posts

139 months

Monday 9th September 2019
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That's about 134 mph, so It must have been lower than that on contact. It would be a new crater otherwise.

It is nearly 1.5 tonnes in mass, so about the same as a car.