Author Topic: Chandrayaan-2 GSLV MkIII NET January 30 2019  (Read 164755 times)

Offline AJA

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #100 on: 01/28/2014 08:55 AM »
Can any one guess the Antenna Type? I have never seen T shaped antenna on any planetary rovers

Maybe they want to let the Rover receive and watch the new digital HD Doordarshan :P

Quote
Thus,
the Chandrayaan-2 Rover solar panel may be expected to see temperature of Teq = - 182.07374 degrees C

really?!? to the fifth decimal???

Hold on, maybe the numbers they used as inputs for the calculation were known to the tenth decimal :D But yeah, doesn't surprise me though... almost all students sleep through the lesson on significant figures. Maybe if they start using them in school exam marking schemes...


Oh, and how are they going to tackle the ultra-low nighttime temperatures? Are they going to use RTGs as well?
Does anyone have enough Plutonium at the moment? I guess they could try with some other nuclide though.


[/font]
http://news.ninemsn.com.au/technology/2014/01/28/11/14/chinese-lunar-rover-cutely-broadcasts-own-death


Ah. That sucks. If it is confirmed to be dust, then I guess the lander's UV telescope would be pretty vulnerable too. The rover does probably dredge up more by nature of its motion though.
« Last Edit: 01/28/2014 09:18 AM by AJA »

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #101 on: 01/28/2014 08:59 AM »

Oh, and how are they going to tackle the ultra-low nighttime temperatures? Are they going to use RTGs as well?



Only If they can develop RTG on time, else they will use the old trusted active thermal management method of ISRO flex heater bank + rechargeable batteries + solar panels. 
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #102 on: 01/28/2014 09:03 AM »
Can any one guess the Antenna Type? I have never seen T shaped antenna on any planetary rovers

Maybe they want to let the Rover receive and watch the new digital HD Doordarshan :P



That would be disaster for the rover health!  :'(

it seems to be a compact microstrip patch antenna not a T shaped antenna. Could be a dual/multi band patch antenna. Any rover which used microstrip patch antenna??
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline sanman

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #103 on: 01/28/2014 09:28 AM »

Oh, and how are they going to tackle the ultra-low nighttime temperatures? Are they going to use RTGs as well?



Only If they can develop RTG on time, else they will use the old trusted active thermal management method of ISRO flex heater bank + rechargeable batteries + solar panels.

What about some kind of phase change material, which could provide some "thermal mass" to buffer the temperature changes? Or would the amount of material required make it too heavy and mass-inefficient? You're only trying to heat the electronics to prevent them from being damaged, right? With nifty lightweight insulators like aerogel, maybe it could be done that way.





Offline AJA

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #104 on: 01/28/2014 09:46 AM »
Only If they can develop RTG on time, else they will use the old trusted active thermal management method of ISRO flex heater bank + rechargeable batteries + solar panels.

Running off a battery for 20 odd days is going to be a real challenge. So much so that I think lunar night operations demand a Radio-isotope heater unit. Doesn't have to be RTG, but something that provides the heat. You'd radiate the heat during day-time operations, and fold up the radiator for night time ops.

But that's a guess. Anyone know if any of the probes that've been to the moon endured a lunar night (or several), and used only batteries (+heaters)?

What about some kind of phase change material, which could provide some "thermal mass" to buffer the temperature changes? Or would the amount of material required make it too heavy and mass-inefficient? You're only trying to heat the electronics to prevent them from being damaged, right? With nifty lightweight insulators like aerogel, maybe it could be done that way.

Thermal mass is mass too. So yeah. Heavy. They'll almost certainly use lightweight insulators, but they'd want it to do double duty as a structural member. Again, to save mass. Which is why I don't think they'll use aerogel. You may as well have a evacuated space double-walled membrane with one or two support posts (aerogel probably doesn't have the structural strength) - eliminating conduction altogether - like a thermos flask.

EDIT: Time to look like an idiot. Spirit and Opportunity are insulated with aerogels. As was Sojourner. So there's obviously something I'm not considering.
« Last Edit: 01/28/2014 09:56 AM by AJA »

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #105 on: 01/28/2014 11:27 AM »

What about some kind of phase change material, which could provide some "thermal mass" to buffer the temperature changes? Or would the amount of material required make it too heavy and mass-inefficient?

Yes, ISRO will employ both passive and active thermal control management for the rover. Passive TCM involves use of thermal grease, thermal paint, multilayer insulation, thermal filler materials, Heat pipes, Thermal flap, optical solar reflectors (OSR), heat radiators etc.
 Active TCM uses flexible heater banks and thermistors. ISRO will have to manage the tradeoff between TCM requirements and weight requirements.


You're only trying to heat the electronics to prevent them from being damaged, right? With nifty lightweight insulators like aerogel, maybe it could be done that way.

Both multilayer insulation and heater banks will be used for designing the Warm electronics box (WEB) that will house all the electronics.

ISRO is also developing fluid circuits for TCM in the crew module, a derivative of which could be employed?

My guess is that ISRO will also move the rover inside the lander during lunar night for extra protection.
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #106 on: 01/28/2014 11:35 AM »


Running off a battery for 20 odd days is going to be a real challenge. So much so that I think lunar night operations demand a Radio-isotope heater unit. Doesn't have to be RTG, but something that provides the heat. You'd radiate the heat during day-time operations, and fold up the radiator for night time ops.

But that's a guess. Anyone know if any of the probes that've been to the moon endured a lunar night (or several), and used only batteries (+heaters)?



Yes running 20 days on battery might be challenging, but perhaps that shouldn't be problematic when most of the electronics will be shut down barring critical monitoring system.
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline AJA

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #107 on: 01/28/2014 03:04 PM »
My guess is that ISRO will also move the rover inside the lander during lunar night for extra protection.

I thought of that when Yutu started having issues. But that has its own attendant problems. First, as sanman's been saying: dust. You drive the rover back, and you'll bring whole heaps of dust into the lander.

Secondly, any deployment mechanism that will essentially have to be reversible will cost mass. (Letting something down onto the lunar surface can use frangible nuts/ cut wires etc. / exploit lunar gravity - but bringing something back up will require a motor. Sure You can simply open up a ramp and let the rover drive down and up along it as depicted in the picture, but then a) you need a ramp and b) folding that on top of the rover (presumably) to offer thermal protection would need a motor. If you didn't plan on getting the rover back into its place, then you could've simply had "drop down" MLI on top of the rover, which covers the vacant space once the rover leaves.

Thirdly, from a science perspective - you're going to limit the rover's range and traverses if it has to get back to the lander each time. This may be the case anyway if we have only a rover and lander (rover needs to stay within communication range)... but the diagram depicts an orbiter too. (Which would allow the rover a free rein).

But if they do decide to do this, then you can turn 1 & 3 into an advantage by getting the rover to sample dust and ejecta from different locations (assuming you put some sort of mini-lab on the lander that can do this analysis. Or shift the instrumentation from the rover to the lander; and make the rover more durable, and lighter.) As for 2 - maybe beef up one solar array structurally, and have it serve as the ramp. And cover it with Corning Gorilla Glass (TM) as a scratch-guard. That'll be a public outreach coup :D
« Last Edit: 01/28/2014 03:04 PM by AJA »

Offline ss1_3

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #108 on: 01/28/2014 05:22 PM »


Oh, and how are they going to tackle the ultra-low nighttime temperatures? Are they going to use RTGs as well?

If they are going to South pole, temperature shouldn't be much of an issue. It remains largely illuminated over a "lunar day" with relatively stable temperature (around -50oC), which should be well within operating range of electronics onboard.

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #109 on: 01/29/2014 03:58 AM »
My guess is that ISRO will also move the rover inside the lander during lunar night for extra protection.

I thought of that when Yutu started having issues. But that has its own attendant problems. First, as sanman's been saying: dust. You drive the rover back, and you'll bring whole heaps of dust into the lander.

Secondly, any deployment mechanism that will essentially have to be reversible will cost mass. (Letting something down onto the lunar surface can use frangible nuts/ cut wires etc. / exploit lunar gravity - but bringing something back up will require a motor. Sure You can simply open up a ramp and let the rover drive down and up along it as depicted in the picture, but then a) you need a ramp and b) folding that on top of the rover (presumably) to offer thermal protection would need a motor. If you didn't plan on getting the rover back into its place, then you could've simply had "drop down" MLI on top of the rover, which covers the vacant space once the rover leaves.

Thirdly, from a science perspective - you're going to limit the rover's range and traverses if it has to get back to the lander each time. This may be the case anyway if we have only a rover and lander (rover needs to stay within communication range)... but the diagram depicts an orbiter too. (Which would allow the rover a free rein).

But if they do decide to do this, then you can turn 1 & 3 into an advantage by getting the rover to sample dust and ejecta from different locations (assuming you put some sort of mini-lab on the lander that can do this analysis. Or shift the instrumentation from the rover to the lander; and make the rover more durable, and lighter.) As for 2 - maybe beef up one solar array structurally, and have it serve as the ramp. And cover it with Corning Gorilla Glass (TM) as a scratch-guard. That'll be a public outreach coup :D

In case of yutu, it wont be possible because yutu sits on top of the lander, so no mechanism to conceal it within the lander. I agree with your points regarding dust ,motorized ramp and restricted range. ISRO will have to take a call based on their.
feasibility studies.

Also, how effective will be the tiny rectangular/square microstrip patch antenna in communication with the orbiter?
« Last Edit: 01/29/2014 04:00 AM by antriksh »
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline AJA

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #110 on: 01/29/2014 04:49 AM »

Yeah, probably wouldn't have helped Yutu much, apart from being in the proximity of a warmer "floor" (or even "ceiling" - if it went and sat under the lander - provided there was enough clearance) that offered a better thermal radiation environment. Mutual benefit too. But I think the deployment was one way, and that the engine bell wasn't that far off the ground.. ruling both out.


Also, how effective will be the tiny rectangular/square microstrip patch antenna in communication with the orbiter?


Isn't that the whole point of a patch antenna? That you can "print" it onto surfaces? It can cover the outside of the rover and enlarge the collecting area. You'd almost definitely have to phase delay some elements of the patch, and perhaps even do this dynamically, depending on orbiter-rover geometry... but still..


That is, if they're going to use one at all. Still in the early phases aren't they?

Offline Steven Pietrobon

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #111 on: 01/29/2014 05:31 AM »
EDIT: Time to look like an idiot. Spirit and Opportunity are insulated with aerogels. As was Sojourner. So there's obviously something I'm not considering.

The Mars rovers used aerogel as the Martian atmosphere is thick enough so that multi layer insulation (MLI) is not effective. On the Moon, there is no atmosphere so using MLI is sufficient. There is no need to use aerogel on the Moon.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline AJA

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #112 on: 01/29/2014 07:44 AM »
The Mars rovers used aerogel as the Martian atmosphere is thick enough so that multi layer insulation (MLI) is not effective. On the Moon, there is no atmosphere so using MLI is sufficient. There is no need to use aerogel on the Moon.

Firstly, shouldn't aerogel take precedence over MLI? Given that it's lighter? If the aerogel didn't suffice, make it thicker, and if it still doesn't work, or the form factor is non-conducive...then maybe bolster the insulation with MLI. But surely you'd want to use aerogel first? Moreover, I don't think aerogel suffers from static charge build up, so there's that advantage as well?

Secondly, why use anything at all? If you need the conductive insulation, surely you add a thin shell around your existing rover body, and evacuate the space between the shell and the body. Mount this shell on a few non-conductive struts (perhaps the struts are made of aerogel), and you're done. A vacuum has lower thermal conductivity (zero) than aerogel.

Unless you're telling me that a slab of aerogel on all faces is actually lighter than that, and has the added benefit of offering some MMOD protection, and some structural stability for a very small tradeoff in mass/thermal conductivity.
« Last Edit: 01/29/2014 07:51 AM by AJA »

Offline baldusi

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #113 on: 01/29/2014 01:31 PM »
AJA, are you aware that you ended up describing MLI?

Offline AJA

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #114 on: 01/29/2014 02:46 PM »
AJA, are you aware that you ended up describing MLI?

Had a hunch, and checked before I posted. But I found

Quote from: Wikipedia article on MLI
In its basic form, it does not appreciably insulate against other thermal losses such as heat conduction or convection.

Same article also said

Quote
Spacecraft also may use MLI as a first line of defense against dust impacts. This normally means spacing it a cm or so away from the surface it is insulating.

This would insulate from conductive heat losses (from spacecraft to MLI, and to whatever the MLI's in contact with. Conduction & convection, if the MLI's in contact with a fluid)

But I don't think I've ever come across a case where the MLI's been applied like this. They always seem to wrap up the thing they're insulating, while being in contact with it. Hence "blanket" as opposed to "tent" or "awning".
« Last Edit: 01/29/2014 02:50 PM by AJA »

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #115 on: 01/29/2014 03:28 PM »
Probable payloads for the CH2 lander

1. An Electrostatic Potential and Dust Analyzer for a lunar lander mission, PRL
2. Chandra’s Surface Thermophysical Experiment (ChaSTE): A payload aboard Chandrayaan-2 Lander Experiment, SPL

CH2 EO payloads:
« Last Edit: 01/29/2014 03:35 PM by antriksh »
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline antriksh

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #116 on: 02/03/2014 05:54 AM »
Nasadiya Sukta:
Srishti se pehle sat nahin thaa, asat bhi nahin | Antariksh bhi nahin, aakaash bhi nahin thaa | chhipaa thaa kyaa, kahaan, kisne dhakaa thaa | us pal to agam, atal jal bhi kahaan thaa ||

From: 1st verse of 129th Hymn of the 10th Book of Rig Veda

Offline Revelf

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #117 on: 02/03/2014 11:23 AM »
something with legs?

Offline sanman

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #118 on: 02/04/2014 01:35 AM »
something with legs?

Like this?


Offline vyoma

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Re: GSLV-MkII, Chandrayaan-2, NET 2018-Q1
« Reply #119 on: 02/19/2014 08:20 AM »
Some tidbits:
http://www.newsonair.com/news.asp?cat=national&id=NN4455
Quote
The project is likely to be completed by 2016-17.
Quote
Also, a few landing sites have been shortlisted based on the images obtained from earlier Moon missions. A special team is constructing the Lander.
« Last Edit: 02/19/2014 08:22 AM by vyoma »