speculating that lander actually did not lost trajectory from 2 KM as shown and it could be more of connection lost issue... surviving 2 km crash and still intact is not feasible IMHO. Also it will matter that what about internals of lander - are all parts etc intact or damaged
If u look at the Armstrong lander test video again: When Armstrong ejected, that may have blown off one side of it (I don't see how they built an ejectable canopy into that but that was very good thinking!)
But the rest of the lander shot off to the far background, and fell down. The crash crumpled the thing and it exploded in flames.
Neither happened with Vikram. Hypergolic propellant is something which ignites without much prodding, and there must be some left, so why did it not explode into flames if it suffered that much damage? OTOH, how would one see a fire in Space? there is no buoyancy to send up smoke signals. This is why the initial report of "detected on thermal imager" was VERY bad news, unless it was dark and cold enough to detect the warm nozzles (which is good news that it was too dark to see by optical cameras, means sun is not up yet). But now BRF says there was no thermal imager so I don't know. In that case there was enough light to see using optics, which is **NOT** so good news.
OTOH if there WAS a fire, the thermal image should have been EZ to detect even from Earth. 2000K against a 200K background? If u can pick up stars u can pick that up.
Remember that the Apollo lunar lander was human-rated to carry 3 suited astronauts. Given the presence of the ejection seat, it can't have been the full final design, but the craft was probably stronger than Vikram since it had to carry at least one human. The ejection height was below 500 meters, hain? The acceleration down was no doubt higher than that above the Moon.
My point is that the drop from there shattered and crumpled the lander, you can see it happening before the dust and flames take over.
So I think the Vikram actually did "land". Maybe on a tilted surface? Why?
See my arguments from the above. I don't like them.
1) It came down within 500m, maybe much closer, of the intended site.
2) It started "Naaarmal" at 2.1km when it still had significant horizontal speed.
3) It ended up well within 500m of intended target (would be interesting to know whether it was further out or fell short)
4) It DID NOT free-fall from any significant altitude (Armstrong video and structural strength argument)
5) It CANNOT have had much horizontal speed at touchdown. (Ditto) IOW, you have to wonder whether there were multiple failures.
Rest is all speculation based on the above facts and inferences from the Armstrong Human-Rated Lander video of 1968.
Lander may have still been swinging. As Dileep says, large oscillations as the controller tried to compensate for an input much larger than its design. Not successful in fully damping the oscillation before touchdown. The thrusts to try and counter the oscillation, caused significant drift from the target zone, which also implies significant sideways speed as it tried to compensate.
So it was still aiming for the target: did not abort that and try moving to the secondary target? This is what bothers me. There was at least one more failure on-board after 2.1 km (maybe happened before).
I would have told the software that
eeph u r close to ground, IMPERATIVE to zero out sideways speed, forget target-center ambitions. X meters miss distance is perfectly fine, but Y > X not good within the following arcs...
It touched down, not fully on legs, or yes, but still with significant tilt and sideward speed due to swing. Or came down on a steep slope. Crumpled one or more legs.
Also, it does not appear to be sending out comms though it was supposed to have significant internal power and smarts to use the external power from the solar panels facing outward. How directional is the backup antenna (if any?) Maybe they decided that if Orientation not within 20 degrees, mission is kaput so no need for omni antenna?
But I have a more optimistic thought on the omni antenna. The reason to use a high-gain antenna is to minimize power required, at the edges of the Lunar Day, maybe last well into the night - and just MAYBE survive till dawn, which would imply a very long surface life.
The same low power put into an omni-directional antenna (huge solid angle!) would generate a far too weak signal - at dawn or dusk.
Remember that the Sun is always very low on the horizon at the South Pole even if one were on a flat surface (no hilltop landing attempted, presumably) So solar power right now may be very weak, which is another reason why cameras on Orbiter are having difficulty seeing the situation during the brief pass(es).
Perhaps as solar day progresses, Earth-based telescopes can resolve much better pictures, and maybe guide Orbiter to get better photos. And the generated power may get to the point where its calls can be picked up. When that happens, a SIT-REP may come out, and all functioning systems can report in. Possibility of re-orienting the directional antenna can be explored. MAYBE, just MAYBE, retracting the remaining legs and firing a thruster (I don't want to be the one that has to authorize that..) just right, could convince it to right itself and sit on its nozzles. Then the door ramp can be opened and Pragyan can roll out, maybe for the 6 days remaining. TOTAL scientific mission success, at that point, though the chemistry experiment raises my concerns about test tubes, burettes and pipettes... Hint: they make even Antarctic explorers carry those ancient things, don't they?
The lunar whatzit experiment and the seismograph (which must already have one good data set in it from the "landing") will work. 2 out of 3 ain't bad.
So! No reason to give up hope. The above may explain all the statements from ISRO.
- It is not coming upright even if thrusters can be commanded, because one or more legs are crumpled. Any such attempt will lead to more damage.
- It is difficult to contact, and not contacted so far.
- There is reason for hope, since The Day Is Still Young.
Given the above, even if contacted, it seems extremely unlikely that the Ambassador Mark 2019 Bullockless Cart can roll out. Getting that particular door open would be a miracle, getting the ramp to tilt down and provide a good angle to the ground is even more unlikely: the rover may roll over if it rolls down the ramp in that case.
BUT.... miracles do happen.
And then we can debate what was the second- and maybe third - failure that occurred. The first alone should ***NOT** have caused the bad landing.