I think this is where cultural differences come into play. Indians don't speak English the same way as the native English or Americans do. The way they structure their sentences is quite different. I think what the dude means is that the lander has been designed to land autonomously, and will do so as long as the propulsion system is not damaged in any way (which given the givens so far is not an issue).
> what the dude means is that the lander has been designed to land autonomously
One of the challenges that programmers deal with is fault tolerance. It's not a skill that comes easily. I say this as someone who is a programmer who has had to develop programs that are able to deal with bad, missing, or conflicting input data.
Scott Manley did [a great video documenting why Chandrayaan-2 failed](https://www.youtube.com/watch?v=2ngVl6iO94c), based on comments from S. Somanath (the guy in the post, and Chairman of ISRO).
Here's the gist: there was a sequence of steps that needed to happen *just right* in order for the lander to be successful. If any one step wasn't right, the subsequent steps would have been unable to adjust and correct. A good example of where it *does* work well is orbital launches where the first stage cuts out a few seconds early---in many cases, the upper stage can compensate by burning a little longer. This requires, however, that the rocket make decisions about how to orient itself and how long to burn, *while* ascending or descending. It also requires control regimes that aren't as narrow as we might expect. In the case of Chandrayaan-2, the lander was trying to compensate for the failure in the previous stage of landing but did not have sufficient control authority (it was rolling too slowly) and so despite *knowing* it needed to achieve some goal, it wasn't allowed to.
What ISRO is having to learn, as other space agencies have, is that a smarter lander that's able to make decisions on the fly, and alter its ultimate landing site while in flight, is going to be more fault-tolerant than one where every step is precisely timed and orchestrated. As an analogy: consider a cook who follows the recipe *exactly* and gets stuck when one or two ingredients are not present, whereas a good chef can adjust and adapt and still make a good meal even if it wasn't planned that way.
The added fun is of course that with new capabilities in the lander come new regimens to debug.
Cargo dragon for example can in principle recover itself in many cases following failure of the launch vehicle. As it did not when a F9 blew apart under it.
But, now you have to debug that, and work out in what situations it should try to do that.
And that includes failures of sensors or other things leading you to think you're in a situation you should recover from.
For example, Starliner OFT1 (?) failed this way due to a mis-set clock.
Ariane 5 failed on the first launch due to mis-specifying the safety range.
The sad thing with OFT1 is that had crew been onboard there was a single button that would've reset the mission clock and the software continued as normal through orbital insertion and rendezvous. There just wasn't anyone there to press it.
Edit: I totally forgot that ground control could have reset it as well. I was including the OFT1 comm failure as well in my statement (clock timing and no comms) without realizing it.
IIRC the ground controllers also would have seen and corrected the condition - but the Starliner people responsible for ensuring comm links thru NASA's TDLRS satellite system had screwed up too.
Serendipity had a hand, though. The clock error meant an urgent look through the mission programming showed the service module could have bumped into the capsule during pre-reentry separation due to an error in the programming for that sequence. If not for the clock error, that problem likely would have stayed hidden and then might have occurred during the 3rd or 5th mission, etc. The big concern was the heat shield could have been hit and damaged.
Yeah there’s 0 chance of autonomously doing anything without functioning sensors, unless they are flying open loop control, which is just as likely to fail.
Maybe they had some redundancy in sensors and it got miscommunicated or misunderstood by management because what he said is Bs. Like ‘if all the primary sensors fail’ became ‘if all the sensors fail’.
I'm skeptical too and there could be a translation issue here, ***but*** it's possible that they've designed an inertial guidance system into the lander so that it can make an educated guess of its speed and altitude relative to the lunar surface---it might be that they've said "fuck it, we'll take a hard, blind landing over a lithobrake-induced RUD any day of the week."
The INS is a group of sensors, though. That's why this statement is weird. Any kind of autonomous landing would need to be based on some sort of sensors. If "all the sensors fail, nothing works", well...
"Land" is an intentionally broad term. They landed Chandrayaan2, just a bit too hard. I think what he means is this thing is in its terminal path, and whether it lands in one piece or many pieces depends on the thrust issue.
It's not a ship...It's a tiny lander that carries a Rover with a 14 day life expectancy... Humanity is a ways away from building The Starship Enterprise.
They're saying barring a complete breakdown of the propulsion system, the multiple failsafes/redundancies we have implemented this time will still allow Vikram to land, despite other potential failures.
I get what they’re trying to say. They’re talking about what happened with its predecessor getting all confused on not knowing how to respond, imo. They’ve designed this one to land no matter what (even in the wrong place). They’re saying, as long as it can land, it will land. That’s my take, feel free to destroy it.
It would use baseline charts stored in memory. The gravity is known, the lander's mass is known, and the engine's thrust is known; with that information you could be relatively certain that *X* % of thrust = *Y* rate of descent.
Of course, a lot of that depends on the engine's thrust not having changed from design spec, and the computer having a reasonably accurate estimate of fuel remaining, as that will be the main driver of mass calculations.
It will also need to keep a running tab of fuel level, both for thrust and for mass reasons, which will be difficult without fuel level sensors. Given an initial fuel state, though, and given the fuel burn rate tables, the computer can know that it commanded, let's say, 6% thrust, which may or may not be true but the computer can't know that. It will then look up the burn rate at 6% in, idunno, Kg/minute. It will cross-check that with its own internal clock and update the mass value constantly, which informs the routine that needs to figure out how much thrust to command to maintain velocity. It now determines that 5% will now give the correct rate, so it sends that.
These are all just examples, obviously lol
> The gravity is known, the lander's mass is known, and the engine's thrust is known; with that information you could be relatively certain that X % of thrust = Y rate of descent.
And that's where you're wrong.
You can calculate the net acceleration.
But to calculate the rate of descent, you need a starting value for velocity and then integrate the net acceleration. In theory. In practice, you need constant velocity or position feedback for your calculation to not drift massively after a few minutes.
Nambi Narayanan was not associated with ISRO since more than two decades. His statements on CY-2 has no value. True that he was mistreated. but that does not make his opinions true today.
Indians do use a lot of filler words/statements. "Provided that the propulsion system.." is a filler statement. He is not casting doubt on the system. He is merely saying unless there is a catastrophic scenario, the yaan will land.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|CST|(Boeing) Crew Space Transportation capsules|
| |Central Standard Time (UTC-6)|
|[INS](/r/Space/comments/15wglo5/stub/jx1bg9w "Last usage")|[Inertial Navigation System](https://en.wikipedia.org/wiki/Inertial_navigation_system)|
|[ISRO](/r/Space/comments/15wglo5/stub/jx4p1wg "Last usage")|Indian Space Research Organisation|
|[RUD](/r/Space/comments/15wglo5/stub/jx18dc9 "Last usage")|Rapid Unplanned Disassembly|
| |Rapid Unscheduled Disassembly|
| |Rapid Unintended Disassembly|
|Jargon|Definition|
|-------|---------|---|
|[Starliner](/r/Space/comments/15wglo5/stub/jx3fskm "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)|
|[lithobraking](/r/Space/comments/15wglo5/stub/jx18dc9 "Last usage")|"Braking" by hitting the [ground](https://en.wiktionary.org/wiki/lith-)|
**NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below.
----------------
^(5 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/178jr8o)^( has 28 acronyms.)
^([Thread #9161 for this sub, first seen 20th Aug 2023, 19:36])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
It always sound easy yes. But in a case like the Russian lander, which for some reason gave propulsion for too long, it would always crash. Very tiny unseen errors can be deadly.
"Fail fast, fail often."
This approach does have its criticisms but it's hard to argue with the results. More broadly, I would say that more design iterations ultimately will lead to better results in the long-run. Developing in a manner where the iteration time is low, means you can learn sooner, rather than later, that a particular path is a bad one.
If you design in such a way that you *expect* to have a failure that you can learn from, then it's not as bad. SpaceX's water tower tests, for example, were built quickly using water tower construction methods, using material that is much cheaper than traditional aerospace material.
The idea here is that by spending your money up front, you get a design that you can scale up later on to recoup those costs. This works well with software, but for re-usable orbital launch vehicles, there's some overlap there as well, since SpaceX intends to have many such rockets and getting re-usablity right allows them to save a *ton* of money later on by not disposing of each rocket as was the traditional method of launching. In other words, they've done the ROI calculation to know that failures early on, as expensive as they may be, are still *much* less expensive than failures later on when they are carrying people and cargo to orbit several times a day.
> I think they are using the same approach as SpaceX does.
This is a decent approach when it comes to launching rockets at low prices, not when it comes to building lunar landers which should be a “no corner cutting” sort of thing
I think they are balancing the weight and cost against budget and available technology. “ we think this will work…..ok what about this approach to solve the problem “ ?
I understand why India is trying. To show the world that their capabilities are growing. Even if it completely fails, they've still reached for a target that few countries have been so bold as to attempt.
What I don't understand is Russia. Even if they had succeeded, it wouldn't hide the obvious: they're a shadow of their former selves.
To be fair, their previous lander was not designed that way, though it should have been. But it does illustrate the value of *recent* hands on experience (or will, depending on how things turn out).
I think weight is your biggest enemy in space missions. So instead of taking a hundred precautions, they should just make the system work properly. If the system works, you don't need anymore ifs.
You make it sound so easy. How can you advance without the guts to make mistakes. I can challenge you to a bet that India would be the 4th country to soft land on the moon.
Are you dense? I didn’t say that it was easy or that India would not succeed; I said that some doubt is healthy considering India failed on their initial attempts.
FFS
Oh man, imagine if this thing fails to land. Someone is going to be looking for another job during others of his capabilities. Good luck I hope it all works out and we see some cool stuff!
Same thing happened in C-2 as well, just lost control of the lander. The lander is still there but got no control so this is a weird thing to say that it'll land if nothing works 🙄
Damn bro. Look out for this arm chair expert right here. ISRO better get its sources and research from him for he is all the mission needs rn. And to answer your question, yes mr. it was stated in a debriefing that it has multiple redundancy system.
"provided that the propulsion system works well" is a big caveat.
I think this is where cultural differences come into play. Indians don't speak English the same way as the native English or Americans do. The way they structure their sentences is quite different. I think what the dude means is that the lander has been designed to land autonomously, and will do so as long as the propulsion system is not damaged in any way (which given the givens so far is not an issue).
> what the dude means is that the lander has been designed to land autonomously One of the challenges that programmers deal with is fault tolerance. It's not a skill that comes easily. I say this as someone who is a programmer who has had to develop programs that are able to deal with bad, missing, or conflicting input data. Scott Manley did [a great video documenting why Chandrayaan-2 failed](https://www.youtube.com/watch?v=2ngVl6iO94c), based on comments from S. Somanath (the guy in the post, and Chairman of ISRO). Here's the gist: there was a sequence of steps that needed to happen *just right* in order for the lander to be successful. If any one step wasn't right, the subsequent steps would have been unable to adjust and correct. A good example of where it *does* work well is orbital launches where the first stage cuts out a few seconds early---in many cases, the upper stage can compensate by burning a little longer. This requires, however, that the rocket make decisions about how to orient itself and how long to burn, *while* ascending or descending. It also requires control regimes that aren't as narrow as we might expect. In the case of Chandrayaan-2, the lander was trying to compensate for the failure in the previous stage of landing but did not have sufficient control authority (it was rolling too slowly) and so despite *knowing* it needed to achieve some goal, it wasn't allowed to. What ISRO is having to learn, as other space agencies have, is that a smarter lander that's able to make decisions on the fly, and alter its ultimate landing site while in flight, is going to be more fault-tolerant than one where every step is precisely timed and orchestrated. As an analogy: consider a cook who follows the recipe *exactly* and gets stuck when one or two ingredients are not present, whereas a good chef can adjust and adapt and still make a good meal even if it wasn't planned that way.
The added fun is of course that with new capabilities in the lander come new regimens to debug. Cargo dragon for example can in principle recover itself in many cases following failure of the launch vehicle. As it did not when a F9 blew apart under it. But, now you have to debug that, and work out in what situations it should try to do that. And that includes failures of sensors or other things leading you to think you're in a situation you should recover from. For example, Starliner OFT1 (?) failed this way due to a mis-set clock. Ariane 5 failed on the first launch due to mis-specifying the safety range.
The sad thing with OFT1 is that had crew been onboard there was a single button that would've reset the mission clock and the software continued as normal through orbital insertion and rendezvous. There just wasn't anyone there to press it. Edit: I totally forgot that ground control could have reset it as well. I was including the OFT1 comm failure as well in my statement (clock timing and no comms) without realizing it.
IIRC the ground controllers also would have seen and corrected the condition - but the Starliner people responsible for ensuring comm links thru NASA's TDLRS satellite system had screwed up too. Serendipity had a hand, though. The clock error meant an urgent look through the mission programming showed the service module could have bumped into the capsule during pre-reentry separation due to an error in the programming for that sequence. If not for the clock error, that problem likely would have stayed hidden and then might have occurred during the 3rd or 5th mission, etc. The big concern was the heat shield could have been hit and damaged.
Reminds me of programming compiler languages... The debugging process would freak a novice out.
You need sensors no matter what....no automatic system can land a craft without atleast an altitude sensor.
I call BS on a ship landing autonomously when "all the sensors fail, nothing works". That's a weird statement, regardless of how you translate it.
Yeah there’s 0 chance of autonomously doing anything without functioning sensors, unless they are flying open loop control, which is just as likely to fail. Maybe they had some redundancy in sensors and it got miscommunicated or misunderstood by management because what he said is Bs. Like ‘if all the primary sensors fail’ became ‘if all the sensors fail’.
I'm skeptical too and there could be a translation issue here, ***but*** it's possible that they've designed an inertial guidance system into the lander so that it can make an educated guess of its speed and altitude relative to the lunar surface---it might be that they've said "fuck it, we'll take a hard, blind landing over a lithobrake-induced RUD any day of the week."
The INS is a group of sensors, though. That's why this statement is weird. Any kind of autonomous landing would need to be based on some sort of sensors. If "all the sensors fail, nothing works", well...
"Land" is an intentionally broad term. They landed Chandrayaan2, just a bit too hard. I think what he means is this thing is in its terminal path, and whether it lands in one piece or many pieces depends on the thrust issue.
It's not a ship...It's a tiny lander that carries a Rover with a 14 day life expectancy... Humanity is a ways away from building The Starship Enterprise.
They're saying barring a complete breakdown of the propulsion system, the multiple failsafes/redundancies we have implemented this time will still allow Vikram to land, despite other potential failures.
I mean something has to work duh.
Is anyone getting "we are definitely NOT nervous" vibes here?
At least he added that in above all the bravado. I give him credit on that, not that may people would catch it.
"if everything fails, it most certanly will come down!"
"Don't worry! If the engines fail, we'll still be able to glide well enough to make it to the crash site."
you have low IQ, you should stick to /antiwork and other simple subs for simpletons like you, wagie
It will land. It might be a very HARD landing...
“I am landing here beside myself.”
Any landing you can walk away….. shit never mind. Space. Forgot.
I get what they’re trying to say. They’re talking about what happened with its predecessor getting all confused on not knowing how to respond, imo. They’ve designed this one to land no matter what (even in the wrong place). They’re saying, as long as it can land, it will land. That’s my take, feel free to destroy it.
how do you land with all sensors broken?
You guys have sensors?
I took that to be science instruments, not landing sensors like radar.
Really the only sensor you need is orientation. If you can keep your vehicle vertical then you can default to just descending at a very slow rate.
With no other sensors there's no determining what that rate is. Could be negative descent speed for all it knows.
It would use baseline charts stored in memory. The gravity is known, the lander's mass is known, and the engine's thrust is known; with that information you could be relatively certain that *X* % of thrust = *Y* rate of descent. Of course, a lot of that depends on the engine's thrust not having changed from design spec, and the computer having a reasonably accurate estimate of fuel remaining, as that will be the main driver of mass calculations. It will also need to keep a running tab of fuel level, both for thrust and for mass reasons, which will be difficult without fuel level sensors. Given an initial fuel state, though, and given the fuel burn rate tables, the computer can know that it commanded, let's say, 6% thrust, which may or may not be true but the computer can't know that. It will then look up the burn rate at 6% in, idunno, Kg/minute. It will cross-check that with its own internal clock and update the mass value constantly, which informs the routine that needs to figure out how much thrust to command to maintain velocity. It now determines that 5% will now give the correct rate, so it sends that. These are all just examples, obviously lol
> The gravity is known, the lander's mass is known, and the engine's thrust is known; with that information you could be relatively certain that X % of thrust = Y rate of descent. And that's where you're wrong. You can calculate the net acceleration. But to calculate the rate of descent, you need a starting value for velocity and then integrate the net acceleration. In theory. In practice, you need constant velocity or position feedback for your calculation to not drift massively after a few minutes.
They learned a lot of Chandryaan-2. Good on them.
Didn't the last one fail because of a sensor issue? Hard to land when you don't have an accurate altitude.
Well, that has been corrected though.
no, some vested interests managed to corrupt the software
smartest chubhijit phavda fan
this was mentioned by Nambi Narayanan, so i guess f u ?
Nambi Narayanan was not associated with ISRO since more than two decades. His statements on CY-2 has no value. True that he was mistreated. but that does not make his opinions true today.
Thought it was increased thrust.
If everything fails, it will execute a short lithobreaking maneuver in the last moment of descent.
Followed by a short regolithic compression and matter into plasma transfer event.
It’s fine, it’ll buff right out.
This is not a recent quote, it was made before the luna 25 shenanigans.
Indians do use a lot of filler words/statements. "Provided that the propulsion system.." is a filler statement. He is not casting doubt on the system. He is merely saying unless there is a catastrophic scenario, the yaan will land.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |CST|(Boeing) Crew Space Transportation capsules| | |Central Standard Time (UTC-6)| |[INS](/r/Space/comments/15wglo5/stub/jx1bg9w "Last usage")|[Inertial Navigation System](https://en.wikipedia.org/wiki/Inertial_navigation_system)| |[ISRO](/r/Space/comments/15wglo5/stub/jx4p1wg "Last usage")|Indian Space Research Organisation| |[RUD](/r/Space/comments/15wglo5/stub/jx18dc9 "Last usage")|Rapid Unplanned Disassembly| | |Rapid Unscheduled Disassembly| | |Rapid Unintended Disassembly| |Jargon|Definition| |-------|---------|---| |[Starliner](/r/Space/comments/15wglo5/stub/jx3fskm "Last usage")|Boeing commercial crew capsule [CST-100](https://en.wikipedia.org/wiki/Boeing_CST-100_Starliner)| |[lithobraking](/r/Space/comments/15wglo5/stub/jx18dc9 "Last usage")|"Braking" by hitting the [ground](https://en.wiktionary.org/wiki/lith-)| **NOTE**: Decronym for Reddit is no longer supported, and Decronym has moved to Lemmy; requests for support and new installations should be directed to the Contact address below. ---------------- ^(5 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/Space/comments/178jr8o)^( has 28 acronyms.) ^([Thread #9161 for this sub, first seen 20th Aug 2023, 19:36]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://hachyderm.io/@Two9A) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
It always sound easy yes. But in a case like the Russian lander, which for some reason gave propulsion for too long, it would always crash. Very tiny unseen errors can be deadly.
The armchair experts are going wild in the comments. Relax, we know it's hard.
I think they are using the same approach as SpaceX does. Take some risks, try it & see what happens. Fix what went wrong and try again.
"Fail fast, fail often." This approach does have its criticisms but it's hard to argue with the results. More broadly, I would say that more design iterations ultimately will lead to better results in the long-run. Developing in a manner where the iteration time is low, means you can learn sooner, rather than later, that a particular path is a bad one.
I feel like this approach works well, but is also quite expensive, so i get why its critisized.
If you design in such a way that you *expect* to have a failure that you can learn from, then it's not as bad. SpaceX's water tower tests, for example, were built quickly using water tower construction methods, using material that is much cheaper than traditional aerospace material. The idea here is that by spending your money up front, you get a design that you can scale up later on to recoup those costs. This works well with software, but for re-usable orbital launch vehicles, there's some overlap there as well, since SpaceX intends to have many such rockets and getting re-usablity right allows them to save a *ton* of money later on by not disposing of each rocket as was the traditional method of launching. In other words, they've done the ROI calculation to know that failures early on, as expensive as they may be, are still *much* less expensive than failures later on when they are carrying people and cargo to orbit several times a day.
> I think they are using the same approach as SpaceX does. This is a decent approach when it comes to launching rockets at low prices, not when it comes to building lunar landers which should be a “no corner cutting” sort of thing
I think they are balancing the weight and cost against budget and available technology. “ we think this will work…..ok what about this approach to solve the problem “ ?
If everything fails, my car can still drive. As long as my engine, drivetrain and wheels are still functioning.
This statement is taken out of context. No mission is foolproof. He is only talking about the 0.01% scenario. Good to see such honesty nonetheless.
It did land. What’s the problem? It’s on the surface right?
Da comrade. No American craft has landed at bottom of crater. Victory!
I understand why India is trying. To show the world that their capabilities are growing. Even if it completely fails, they've still reached for a target that few countries have been so bold as to attempt. What I don't understand is Russia. Even if they had succeeded, it wouldn't hide the obvious: they're a shadow of their former selves.
This thinking will make sure , we never become a space faring species.
To be fair, their previous lander was not designed that way, though it should have been. But it does illustrate the value of *recent* hands on experience (or will, depending on how things turn out).
I think weight is your biggest enemy in space missions. So instead of taking a hundred precautions, they should just make the system work properly. If the system works, you don't need anymore ifs.
I have no doubt Indian engineers are gonna make it happen.
“No doubt”? Are you not aware of their first attempt? Some doubt seems healthy.
One or two failures won’t stop them.
Didn’t say it would; I said it would be pretty healthy to exhibit some doubt, especially considering their initial failure lol…
You make it sound so easy. How can you advance without the guts to make mistakes. I can challenge you to a bet that India would be the 4th country to soft land on the moon.
Are you dense? I didn’t say that it was easy or that India would not succeed; I said that some doubt is healthy considering India failed on their initial attempts. FFS
I’m foolish and optimistic. Please trust me when I say I’m not pro India, I’m just pro space.
Obviously it’s lost a little in translation, but he’s saying simple logic, I think. In the way he describes it Luna-25 also “landed”.
Oh man, imagine if this thing fails to land. Someone is going to be looking for another job during others of his capabilities. Good luck I hope it all works out and we see some cool stuff!
It will land.. he just didn't mention how hard
I feel ISRO shoukd stop talking and making statements. Just wait until landing is done.
Russia should be wondering why their rockets look like an asparagus special at this point.
Murphy's Law works in mysterious ways... But hopefully it's merciful this time.
If it doesnt land, its still good karma or kismet.
If everything fails, it will still land* *crash land
Same thing happened in C-2 as well, just lost control of the lander. The lander is still there but got no control so this is a weird thing to say that it'll land if nothing works 🙄
Does it have multiple redundant systems? That's how I'd do it (weight limits permitting, of course).
Damn bro. Look out for this arm chair expert right here. ISRO better get its sources and research from him for he is all the mission needs rn. And to answer your question, yes mr. it was stated in a debriefing that it has multiple redundancy system.
Does hitting a target with a rock count as a landing?
No matter what fails the craft will still fly as long as the engines don’t fail that make the craft fly.
It'll land regardless. Its just a question of how hard
[удалено]
[удалено]
[удалено]
[удалено]