Chandrayan-2 Mission

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UlanBatori
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Re: Chandrayan-2 Mission

Postby UlanBatori » 25 Sep 2019 22:07

This means that they need to send a low-ballistic craft ("jaspreet") to probe this layer. Maybe send down 6 of them. Single thrust chamber valve-connected to 6 nozzles distributed around the ball. Gravity sensor to tell up from down. Don't depend on external e-mag signals.
Finally something other than regolith and iron - manganese deposits to study on the Moon.
But note: now the discussion has shifted to a scenario exactly like Godzillaji reaching up and grabbing V-Kramji.

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Re: Chandrayan-2 Mission

Postby hnair » 25 Sep 2019 22:45

UB-saar, fourth cousin had chai and:
- higher up (till now) is against release of pics because, well, with what they have, there might be none of shakinaw effect that is nowadays demanded of missions
- orbiter took pics allright. Visual spectrum might have glare/albedo/something causing lack of resolution (probably needs multiple passes under various light conditions to stitch up a half decent passport-photo of the lander)
- infra-red also was suboptimal: by the time orbiter flew past, the lifeless lander has cooled down to ambient temperature and melded into the backdrop
- visual spectrum however seem to show shadows of lander legs doing a Jean-Claude van Damme style sidekick

Added later: the earlier chai, just after the thud was that at last point of contact, the flame was pointing upwards. That flip causing anomaly is probably where the entire investigation is going on about.

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Re: Chandrayan-2 Mission

Postby somdev » 26 Sep 2019 00:04

Vayutuvan wrote:^somdev,

how strong is the field at 2km height? I think milspec hardening will take care of this kind of radiation. that said, there could be a bad key component or an exposed connector.

reliability figures for these components will be needed to assign a probability of the kind ramana is asking, data like MTTFF for each component, subsubsystem, subsystem.

when doing system tests, ISRO would have exposed VL to intense radiation. they also,would have stress


Various models have estimated the lunar dust-plasma fountain to be present up to ~100kms altitude and this has been confirmed by measurements to some extent(e.g., ray-pattern streamers). It is hard to say how strong the field is at 2km height at any instant and there could be significant variations during day/night transitions, solar wind intensity (could be GeVs in a single burst), high energy cosmic rays etc. Again, w.r.t. Earth's magnetic field, Earth's magnetotail extends well beyond the orbit of the Moon and once a month the Moon orbits through it. During the crossing the Moon comes in contact with a gigantic plasma layer of hot charged particles trapped in the tail and this could further add to the woes (see figure below). Again cumulative effect of all these factors are little understood as of yet and difficult to model or simulate!

Again, difficult to say MTTF for each component in such environment. But electronics failure or degradation in space in not uncommon. For instance, NASA's Mars Reconnaissance Orbiter suffered single event upset with corruption (soft error) noted in command and data handling subsystem (C&DH) which is the brain of the spacecraft and controls all spacecraft functions (specifically rad. hardened static RAM) which was mitigated by uploading additional CRC protection. I can think of the following hazards:

1. Spacecraft surface charging leading to massive electrostatic discharge
2. Total ionising dose exceeds permissible levels
3. Displacement damage causing displacement of atoms from their normal lattice positions
4. Single event upset, latch-up or burnout

AFAIK, ISRO uses its own Vikram processor SOC fabricated by Semi-Conductor Laboratory, Chandigarh and am sure adequate radiation exposure/testing has been carried out including cables and connectors (MM, HBM, CDM ESD models) and there are multiple redundant systems built into the lander - real estate permitting. However, electronic components still fail in space environments and at times compromising missions. Even solar panels are included as electronic components and subsystems.

Like everyone else I am trying to think of what could have gone wrong!

Image

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 00:46

somdev wrote:
1. Spacecraft surface charging leading to massive electrostatic discharge
2. Total ionising dose exceeds permissible levels
3. Displacement damage causing displacement of atoms from their normal lattice positions
4. Single event upset, latch-up or burnout
....
Like everyone else I am trying to think of what could have gone wrong!


Sure, I have no problem with that. I am just trying to qualitatively understand the radiation levels.

We also need to look at solar flare data and sun spot data in an interval straddling the time at which communications were lost.
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Re: Chandrayan-2 Mission

Postby somdev » 26 Sep 2019 00:57

I am pretty sure ISRO had an interface with/input from solar and lunar physics scientist community and did extensive modelling on the date ranges planned ... but then again space weather is so unpredictable and there are so many variables that it is hard to estimate radiation levels

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Re: Chandrayan-2 Mission

Postby somdev » 26 Sep 2019 01:08

Vikram lander has directional high gain antenna which would not work if the orientation is not right ...but then again what about the low gain antenna on board for such critical situations?

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Re: Chandrayan-2 Mission

Postby UlanBatori » 26 Sep 2019 01:17

hnair wrote:Added later: the earlier chai, just after the thud was that at last point of contact, the flame was pointing upwards. That flip causing anomaly is probably where the entire investigation is going on about.


Maybe someone programmed rotation by 270 deg. instead of 90 deg. JUST IDLY SPECULATING!!! Fortran in some versions could not distinguish between 1st and 4th quadrant when doing InBharj Tanghent unless u put ATAN2, and a pi/2 is a pi/2, + or minus. But if the flame was upwards at 2.1 km, it is a miracle that anything is left of anything to point upwards. So it kept on rotating maybe? And the legs are there, but rest of lander is in Godzillaji's tummy?

Too many unknowns. They don't know the gravity field too well. They don't know the dust field. They don't know the plasma field, They don't know the variations in surface magnetic field - and they live dangerously by zooming along at 2000 m. - or was it 300m and do they know?

Maybe Vikram landed smack dead center in the deepest ice lake on the Moon. Like the Valujet flight that dived at transonic/supersonic speed vertically into the Florida Everglades. Disappeared without a trace until months later.

They need to send the Jaspreets.

Landing in any orientation is a success then, and it can hop around wherever it wants. Take a mobile Phone foto each time it hits the ground and each time it reaches zenith. Maybe I should get the Ulan Bator Yak Madarssa to design this. If there is interest in the chaikadai.

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 01:38

Just to give a sense of the energy produced when something similar to VL crashes into the moon -

https://en.wikipedia.org/wiki/Beresheet

The final telemetry reading indicated that at an altitude of 150 meters the craft was still traveling over 500 km/hour (139 m/s), resulting in a total loss on impact with the lunar surface.[39][40]


I read somewhere else that this produced energy equivalent of 2 tons of TNT. I posted the before and after animation from Bersheet crash site from LRO.

If VL had crashed, it would have produced a before-after signature similar to the Bersheet. If anything, the altitude was ~2x and VL has higher almost 4 times the mass of the Bersheet lander. Of course, it was traveling slower than the Bersheet.

The autonomous system might have recovered but communication circuitry got fried, may be.
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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 01:39

UlanBatori wrote:They need to send the Jaspreets.


What is "Jaspreet" in non-pingrez? :)

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Re: Chandrayan-2 Mission

Postby UlanBatori » 26 Sep 2019 01:53

Vt: This is very interesting. What is the probability of the gyroscope for the main engine on the first ISRAELI Lander ... and the whatzit on the first INDIAN Lander, both failing at essentially the SAME final stage of a hugely complex mission?

Worth contemplating. Are u sure Pakis are not sitting there with Stingers?

Added:

"Jaspreet" is a Highly Elastic Resilient, Low-Ballistic All-Attitude Lunar Low-Altitude Probe and Rapid Lunar Locomotion, Reconnaissance, Photography and Communication System.

Can "land" at 200 kmph vertical speed without damage, bounces like a Bumrah Bouncer, and has (at least) 6 nozzles pointed in 6 directions, to allow it to skip along the lunar surface at speeds up to 150kmph (like a Bumrah no-ball speeding past Pant to the boundary). Versus the 2cm per hour top speed of the silly Chinese rover etc.

Think of it this way: Extra-terrestrial locomotion has been hog-tied by the "Science Package" gangs, who insist on Rovers that look like gold-plated Meccano carts (or "honey wagons" but I was trying to be nice..) with flags like a Mahabbarata Chariot. Design has not evolved much since the Luna-9.

A set of 6 Jaspreets could be dropped from a moon probe, to slow down by retro-rockets and land wherever. And bounce around, with the mobile phones inside taking photos. Transmission to the Orbiter may be a slight problem, we haven't solved it yet.

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 02:11

UlanBatori wrote:Transmission to the Orbiter may be a slight problem, we haven't solved it yet.


If a working Jaspreet with the required structural integrity can be made, why would the comm design lag behind, hain ji? The whole body of Jaspreet can act like an omnidirectional atenna. :mrgreen:

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 02:27

UB saar,

Here is one interesting design, albeit dated.

Lunar Lander Structural Design Studies at NASA Langley (PDF)

The design of the supporting struts can be arranged spherically, then you have the Jaspreet. Struts also can act as antennae.

Kickin' Up some dust (Slide PDF)

This paper gives how to unfold a polyhedral complex. What one does is to embed the folded structure skeletal structure a spherically symmetric module (say dodecahedron) housing the instrumentation. Just before landing, the structure unfolds through actuators and link up to form a rigid protective cage around the core module. The protective cage would be rigid if it is a simplicial complex (in 3D case, it is a tetrahedral complex). That said, some links may be eliminated.

Joining Unfoldings, JMD2013 (PDF)

Read the above paper after reading the following Wikipedia page on Rigidity Matroids.

https://en.wikipedia.org/wiki/Rigidity_matroid
Last edited by Vayutuvan on 26 Sep 2019 04:13, edited 2 times in total.

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Re: Chandrayan-2 Mission

Postby ramana » 26 Sep 2019 02:31

UB The tumble is in pitch axis with a ~ 270 degree turn.
After that there is no recovery mechanism and no altitude or distance to make the recovery.
And this makes the reverse thrusters add velocity instead of reducing.

The tumble started in the rough braking phase itself.

Need to see the ISRO 6Dof model with the reverse thrusters and the small attitude correction thrusters.

This can be done in MATLAB.

Thinking about this may be the side 50N thrusters over corrected and tipped the lander?

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Re: Chandrayan-2 Mission

Postby somdev » 26 Sep 2019 03:28

Aditya L1 in halo orbit will return a deluge of data that will help in modelling and simulation of future lunar landings w.r.t. space weather and solar wind/particle flux

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Re: Chandrayan-2 Mission

Postby Haridas » 26 Sep 2019 04:37

somdev wrote:Vikram lander has directional high gain antenna which would not work if the orientation is not right ...but then again what about the low gain antenna on board for such critical situations?

As I was reading somewhere in the literature the final SNR (Signal to Noise ratio) was just 8 db or so and the antenna gain was >10 dB (perhaps 18 dB) for the designed bit rate. The post hard-landing radio tracking indicates faded but unambiguous carrier that could only come from the lander (as there are no other craft that is using that freq). The very fact that carrier can be detected (by synchronous detection in the digital radio receiver) indicates antenna pointing syndrome.

As for what about the low gain (wide angle) antenna. There is no indication it is for Lander to earth communication (where is the 10 times more power available for the moon-earth link budget even for very low data rate?), perhaps it is only for fall back comm between Orbiter and lander, and possibly the hard landing on its head crushed the low gain antenna.

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Re: Chandrayan-2 Mission

Postby UlanBatori » 26 Sep 2019 06:50

All point to the need for the Jaspreet. VTji, the whole point is to get rid of this dependence on legs, and allow a hard landing with bounce. The ISRO engineer who spoke (maybe out of turn) gave the truth away: Strange phenomena encountered at low altitude, which is fabulous news for science but causes huge uncertainty for engineers.

I hear the lunar surface is abrasive, but is it extremely hard? So what if it is? Bumrah smashes a leather ball on hard ground 240 times in an innings at 80 to 90 mph, and the ball gets smashed to the straight and cover boundaries quite a few times at maybe 150mph impact speed.

If the innards survive, what is the problem? That is the second aspect of my design argument: scrap the delicate science package and put in mobile phones in gorilla cases. If the shell can serve as an omni-directional antenna with a built-in grid that is fine, I don't know anything about antenna design.

But think about what we are reading: whole thing seems designed for a very very narrow Tunnel Of Survivability. High-Gain antenna that loses contact in case of high angular acceleration. Thrusters, where overperformance of one causes a moment that the others cannot restore. Requirement to do a Pogachev Cobra maneuver 300m above the surface, with no backup glide or parachute. Requirement to land precisely on 4 feet.

ISRO has to give its engineers more leeway. Hence the Jaspreet. The bonus is the bouncing mode locomotion that allows exploration of a far larger area than Pragyan could have ever hoped to cover in 2 weeks. Of course once fuel is exhausted it dies: I can't see how to make it solar/thermally-powered while also being able to survive hard bounce.

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Re: Chandrayan-2 Mission

Postby UlanBatori » 26 Sep 2019 07:08

If they insist on legs they should hire some cats as the first Chiefs of Lander Attitude Control. Cats seem to manage in-space roll recovery quite well?

But I ask again: Both the Israeli and Indian landers being lost in the same way, seems too much of a coincidence. Gyroscopes don't just fail that often, do they? This seems too much like a James Bond movie. Gyroscope spins itself to destruction. Final stage thruster keeps burning after it is asked t shut down. The hand of Blofeld and SPECTER is evident.

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Re: Chandrayan-2 Mission

Postby prasannasimha » 26 Sep 2019 07:52

Gyroscopes could have had a Gimbal lock
FWIW
The rotation loop completed the 360 Deg flip as seen from telemetry but during the flip it rapidly descended leading it to try to fire to decelerate for given altitude.
Now we had only 2 engines on which does not have enough theust. So engine valiantly tried to keep correcting but ended in a ground smack like a car losing its breaks and hitting wall despite pressing ineffective breaks.
Question about throttling down all 4/5 engines is was it throttlable down enough to the lowest level requirement.
While we talk of mobile hardware simple thing they are not radiation and delta T hardened enough -( remember even Chandrayaan 1's electronics got fried despite hardening to a particular level so they has to redesign)

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Re: Chandrayan-2 Mission

Postby Haridas » 26 Sep 2019 11:58

prasannasimha wrote:While we talk of mobile hardware simple thing they are not radiation and delta T hardened enough -( remember even Chandrayaan 1's electronics got fried despite hardening to a particular level so they has to redesign)

AFAIRrecall electronics was radiation hardened. OTOH there is no concept of Temp hardening as almost everything is Silicon based semiconductor and at best Military/space rated parts operate upto 125deg C and junction temp of 150 deg C.
CY1 partially failed due to bus thermal management design issue that did not expect very high lunar reflectance. So orbit had to be lifted from 100km planned altitude.

For higher temp rated semiconductors some day one could possibly have GaN based semiconductor that operate to 250 deg C junction temperature.
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Re: Chandrayan-2 Mission

Postby Haridas » 26 Sep 2019 12:01

prasannasimha wrote:Gyroscopes could have had a Gimbal lock

You mean IMU gimble lock? As the gyros sensors are solidstate. But for that exact reason one always has one more axis ; ie 4 axis.

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Re: Chandrayan-2 Mission

Postby juvva » 26 Sep 2019 15:54

One another possible scenario ( as we wait for ISRO to tell us what really happened - if they ever will):

- as Vikram transitioned from coarse to fine breaking phase, two of the four engines were shut down, by the control system. But one of the engines refused to die, or produced residual thrust flipping the lander into a tumble.

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Re: Chandrayan-2 Mission

Postby UlanBatori » 26 Sep 2019 17:20

What is 360 degree flip?

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 21:27

UlanBatori wrote:All point to the need for the Jaspreet. VTji, the whole point is to get rid of this dependence on legs, ... Of course once fuel is exhausted it dies: I can't see how to make it solar/thermally-powered while also being able to survive hard bounce.


piezoelectric generator to charge a battery? it can keep uploading all the data after it comes to halt. it may not be able to move around though or can it? thre are some interesting materials that display PE effect - ceramics, polymers (from Wikipedia page)

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 26 Sep 2019 21:35

UlanBatori wrote:What is 360 degree flip?

two flips or a flip flop. :D
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Re: Chandrayan-2 Mission

Postby prasannasimha » 26 Sep 2019 21:37

UlanBatori wrote:What is 360 degree flip?

If you see the image during the landing the animation showing the position of the lander actually did a Vishnu chakra type of somersault 360 deg rotation back to its vertical position and righted itself (I immediately commented as to why it was doing such a flip) but there was a sharp [period of descent when it was pointing itself "head down" towards the moon. By that time it had a steep vertical height loss. So the control system tried to correct the landers position which was supposed to be straight up in the fine breaking phase(or whatever they were calling it)

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Re: Chandrayan-2 Mission

Postby UlanBatori » 26 Sep 2019 22:03

Vayutuvan wrote:
UlanBatori wrote:All point to the need for the Jaspreet. VTji, the whole point is to get rid of this dependence on legs, ... Of course once fuel is exhausted it dies: I can't see how to make it solar/thermally-powered while also being able to survive hard bounce.


piezoelectric generator to charge a battery? it can keep uploading all the data after it comes to halt. it may not be able to move around though or can it? thre are some interesting materials that display PE effect - ceramics, polymers (from Wikipedia page)


Locomotion is the key advantage of the Jaspreet, compared to the honey-wagon Rovers/Chariots with their clunky wheels, transmissions etc. As long as fuel lasts, the ball can boost off the surface along a ballistic trajectory, and bounce along. May last only a day of hop-skip, but can cover a huge area. You can now trade off the fuel and nozzles cost against the savings by avoiding the legs, shock-absorbers, interior-carried rover, ramp, rover wheels, etc etc etc. Now that I think about it, that is a good amount of fuel.

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Re: Chandrayan-2 Mission

Postby somdev » 26 Sep 2019 22:16

UlanBatori wrote:What is 360 degree flip?


Turn turtle twice ... probably hit by enormous vortices of ‘space hurricane’ (due to Kelvin-Helmholtz instability waves) in the magnetotail crisscrossing the lunar orbit

Image

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Re: Chandrayan-2 Mission

Postby UlanBatori » 27 Sep 2019 03:06

Thanks, somdevji. Beautiful pic, but I doubt very much if such things can exert large forces, given that the vehicle was already traveling pretty slowly. Maybe caused buildup of an ion layer that zapped electrical circuits (may have also killed the Israeli gyroscope). But I thought that was what the gold foil coverings were supposed to accomplish: prevent charge accumulation on the surface.

In the pic, note that the Moon is around 300,000 to 400,000 km from Earth, while Earth's diameter is around 13000km. That is not 2.5 diameters away as shown in the pic, but about 25 diameters away. Could be considered to be "far wake".

The name "Kelvin-Helmholtz instability" is impressive but what is the source of shear? It is not a 2-dimensional (cylinder) wake, but the wake of a sphere.

One other minor quibble I have is with the shock wave ahead of Earth forming one Earth diameter ahead. With the Sun, there is s strong solar wind blasting out, so the shock if any will stand off, but Earth only blasts out hot air when Arundhati Roy opens her mouth. Any shock would form not far beyond the atmosphere (I know very little about magnetic field behavior, sorry), and be extremely weak.
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Re: Chandrayan-2 Mission

Postby Vayutuvan » 27 Sep 2019 05:12

A historical note: Radiation hardening of spacecraft/electronics was due to Van Allen Radiation Belts.

As for Kelvin-Helmholtz instability, since there are two plasmas - positively charged and electrons - could there be a velocity shear between the layers leading to turbulence?

The oppositely charged plasmas have friction (+ve and -ve ions recombining and neutralizing to form a dielectric layer). An unusually large solar flare might introduce the required small disturbance between the interface boundary of these +vely and -vely charged plasmas.

Please take a look at https://en.wikipedia.org/wiki/Debye_length for how at what length the potential difference falls off exponentially.

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Re: Chandrayan-2 Mission

Postby ramana » 27 Sep 2019 05:55

All this is interesting space phenomenon but has nothing to do with the Vikram lander anomaly.

There is a reason why I posted the signature of the anomaly and any failure hypothesis has to meet them.

UB please don't encourage out of carton thinking.

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Re: Chandrayan-2 Mission

Postby neeraj » 27 Sep 2019 06:06

Are there any pictures released of the moon taken by the orbiter?

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 27 Sep 2019 07:32

ramana wrote:UB please don't encourage out of carton thinking.


on second thought, I yield to Ramana. I understand why he wants to put a stop to this line of thinking. pranaam.

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Re: Chandrayan-2 Mission

Postby Amber G. » 27 Sep 2019 09:18

NASA/LRO mission imaged the targeted landing site of India’s Chandrayaan-2 lander, Vikram. The images were taken at dusk, and the team was not able to locate the lander. More images will be taken in October during a flyby in favorable lighting.
.Image
Link: Obscured in the Lunar Highlands?

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Re: Chandrayan-2 Mission

Postby SaiK » 27 Sep 2019 09:36

no impact marks?

e.g:
Image
https://www.nytimes.com/interactive/201 ... india.html

Image
More recently, the European-Russian Schiaparelli lander crashed during descent in 2016, leaving a dark splotch on a smooth Martian plain.

or could it be it got into a loose lunar soil and went few feet deep in... there should be some splotch pattern visible.

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Re: Chandrayan-2 Mission

Postby UlanBatori » 27 Sep 2019 17:29

No out of carton thinking. Also won't mention that carton can be sent to Moon low-cost via ion propulsion. Isp 5000 s. Very low Mass Ratio. EZ 4 PSLV.

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Re: Chandrayan-2 Mission

Postby SaiK » 27 Sep 2019 19:23

Then we should send as many cartons as we can to test land as missile payloads.

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Re: Chandrayan-2 Mission

Postby Vayutuvan » 27 Sep 2019 21:40

I think focus of this thread is limited to CY2 and RCA. best thread for "out of the box" thinking would be physics thread, IMHO.
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Re: Chandrayan-2 Mission

Postby UlanBatori » 27 Sep 2019 23:37

There is a verse from the Ramayana to describe why that is not feasible, sorry.

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Re: Chandrayan-2 Mission

Postby UlanBatori » 27 Sep 2019 23:43

What am I supposed 2 b seeing in this image? Looks like a moon-slide in the top right corner crater.

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Re: Chandrayan-2 Mission

Postby ashbhee » 28 Sep 2019 01:50

If ISRO has images of Vikram why not release it, why are they waiting for NASA to do it?


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