Chandrayan-2 Mission

Vayutuvan · Post by **Vayutuvan** » 26 Sep 2019 01:39

UlanBatori wrote:They need to send the Jaspreets.

What is "Jaspreet" in non-pingrez?

UlanBatori · Post by **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.

Vayutuvan · Post by **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.

Vayutuvan · Post by **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

ramana · Post by **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?

Haridas · Post by **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.

UlanBatori · Post by **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.

UlanBatori · Post by **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.

prasannasimha · Post by **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)

Haridas · Post by **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.

Haridas · Post by **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.

juvva · Post by **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.

UlanBatori · Post by **UlanBatori** » 26 Sep 2019 17:20

What is 360 degree flip?

Vayutuvan · Post by **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)

Vayutuvan · Post by **Vayutuvan** » 26 Sep 2019 21:35

UlanBatori wrote:What is 360 degree flip?

two flips or a flip flop.

prasannasimha · Post by **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)

UlanBatori · Post by **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.

UlanBatori · Post by **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.

Vayutuvan · Post by **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.

ramana · Post by **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.

neeraj · Post by **neeraj** » 27 Sep 2019 06:06

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

Vayutuvan · Post by **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.

Amber G. · Post by **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.
.

Link: Obscured in the Lunar Highlands?

SaiK · Post by **SaiK** » 27 Sep 2019 09:36

no impact marks?

e.g:

https://www.nytimes.com/interactive/201 ... india.html

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.

UlanBatori · Post by **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.

SaiK · Post by **SaiK** » 27 Sep 2019 19:23

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

Vayutuvan · Post by **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.

UlanBatori · Post by **UlanBatori** » 27 Sep 2019 23:37

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

UlanBatori · Post by **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.

ashbhee · Post by **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?

juvva · Post by **juvva** » 28 Sep 2019 06:57

Haridas wrote:
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.

What is the 4th axis? ( I thought, Einstein was the only guy, who believed in the 4th axis ).

UlanBatori · Post by **UlanBatori** » 28 Sep 2019 07:27

Vikram lander could have sailed on the lunar electric field like a "ballooning" spider?

2 solar panels and 4 legs outstretched: just like a spider minus 2 legs.

Haridas · Post by **Haridas** » 28 Sep 2019 12:29

juvva wrote:
Haridas wrote: 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.
What is the 4th axis? ( I thought, Einstein was the only guy, who believed in the 4th axis ).

A means to keep the 3 gimbles away from getting near lockin orientatuon.

SSSalvi · Post by **SSSalvi** » 28 Sep 2019 12:44

There are NO images.... Orbiter orbit does not pass over intended Landing Site.

If it has to image the area then they have to make the ORBITER look across track .. have they planned for that capability vis a vis onboard fuel budget of what they are claiming of 7 years lifetime?

SaiK · Post by **SaiK** » 28 Sep 2019 21:55

https://www.indiatoday.in/science/story ... 2019-09-27

The LRO passed over the landing site on September 17 and acquired a set of high-resolution images of the area; so far the LROC team has not been able to locate or image the lander.

LRO will next fly over the landing site on October 14 when lighting conditions will be more favourable, John Keller, Deputy Project Scientist Lunar Reconnaissance Orbiter Mission, Goddard Space Flight Centre, told PTI via email.

"It was dusk when the landing area was imaged and thus large shadows covered much of the terrain; it is possible that the Vikram lander is hiding in a shadow. The lighting will be favourable when LRO passes over the site in October and once again attempts to locate and image the lander," Nasa said.

UlanBatori · Post by **UlanBatori** » 28 Sep 2019 23:11

This thread is now more repetitive than an orbit by the LRO. As long as nothing new is discussed v should b fine. Maybe post a few pics of the launch?

Amber G. · Post by **Amber G.** » 29 Sep 2019 00:11

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

Both CY2, and Nasa's LRO are near polar orbit.., LRO's next pass will be in October over the site in better lightning condition. CY2 will also pass through (about once a month) over the course of the year. (Per ISRO the orbiter is functional and it is scheduled to send back observations over the year..) More eyes in the sky better it is.

>> Current orbits (Green LRO, other CY2). (Remember, moon surface below is spinning)

(Moon's North is thin vertical line - as you can see CY2's orbit is pretty close to exact polar orbit)

One part, some of do not understand that it is not that simple - For example, LRO's recent image - approximately 900 million illuminated pixels were examined for the target area (about 1km x 1 km) .. If I understand correctly each pixel is slightly bigger than a meter ([NASA/GSFC/Arizona State University has more details.).

ISRO's CY2 camera, is supposed to have a have a slightly better resolution but It is further than LRO's closest approach (which is about 50 km). I believe that CY2's slightly elliptical orbit is such that, it is slightly closer to the surface than average near the Vikram landing sight. .. As said before other conditions such as light etc are also a factor. In any case looking for Vikram is more complicated than many think,

Hope this is helpful.

prasannasimha · Post by **prasannasimha** » 29 Sep 2019 14:24

UlanBatori wrote:This thread is now more repetitive than an orbit by the LRO. As long as nothing new is discussed v should b fine. Maybe post a few pics of the launch?

Then please desist from posting if noncontributory

Amber G. · Post by **Amber G.** » 29 Sep 2019 21:59

Amber G. wrote:
ashbhee wrote:If ISRO has images of Vikram why not release it, why are they waiting for NASA to do it?

For example, LRO's recent image - approximately 900 million illuminated pixels were examined for the target area (about 1km x 1 km) .. If I understand correctly each pixel is slightly bigger than a meter ([NASA/GSFC/Arizona State University has more details.).
.

Just to give a sense, this is one picture from LRO ..( CY2 images will be similar too).. the circled part (and in real life, there were thousands such candidates) was suspected by some as possible Vikram.. One literally does that by comparing 'before' and 'after' pictures to see if there is anything new in the land-scape at the right point.

(ISRO does NOT have, neither expected to have pictures like:

prasannasimha · Post by **prasannasimha** » 29 Sep 2019 22:55

To put it into perspective the expected image even of the CY2 orbiter would be 3 pixels wide and that of LRO 1 pixel in size. The shadow analysis may give more information. As Amber G said it will require comparing of before and after images.