It isnt upside down. It wasnt ever meant to land thrusters-down. It should be on its side but is on its nose... 90 out rather than 180. The BBC has better renderings of how it should have landed.
The first image on that page, the one showing the spacecraft nose-down, is said to be an actual photograph, not a rendering. Is that true? On the one hand, the image has a few flaws that I would not expect on a rendering, but on the other hand, how in the world could such a photograph have been taken? Were there two landers?
Apparently there is an HN rule stating that we should never ask a commenter whether or not they have read the article posted. I respect that rule, it's there for a reason to prevent snark and all sorts of flamebait that can turn a forum toxic. However, for the sake of encouraging thoughtful and constructive discussion I am going to politely point out that the answer to that question was to be found in both the original article posted and the BBC story subsequently linked in the parent comment.
I wonder if they had accelerometers recording exactly what happened as it touched down and ended up on it's back?
It was meant to use a rather odd "two-step" landing procedure where it first touches down on the lunar surface on it's rear/primary landing gear, then pivots forward/falls under gravity to also touch down on the front/secondary landing gear.
Presumably this landing procedure was simulated under lunar gravity, but it seems there are multiple potential failure modes:
1) After rear "leg" touchdown, over-rotate forwards over front leg (ending up on back), OR
2) After front "leg" touchdown, bounce/recoil backwards off front leg, flipping onto back, OR
3) Front landing gear hits rock on one side (left or right), thereby flipping it sideways onto back
The whole procedure seems to rely not only on having correctly simulated under lunar gravity (and with correctly simulated stiffness of the vehicle) to avoid scenarios 1) & 2) (which would be different under earth gravity), but also the softness of the landing site being uniform and as simulated - otherwise if landing site surface was harder (rock) or softer than expected, or uneven, then this type of pivot and bounce/not landing would not go as planned.
NASA seems to have done a better job in designing fool-proof landing mechanisms, from the bouncing ball of the first mars rover, to the sky-crane landing of the latest one (which appears over-complicated, but no doubt was chosen at least in part because it is in fact more predictable than the alternatives).
The two-step sounds precisely like how all forward-moving aircraft land: Rear touch first. The alternative (front touch first) is dangerous for reasons any BMX biker could explain: You're much more sensitive to pitching forward from forward-of-gravity friction.
But for a propulsive landing, why would they want to have forward velocity at all, unless by design for this type of landing ? I'd have thought the preference would be to kill forward speed and land vertically.
> One of the lander's main engines lost thrust about 50 meters (54 yards) above the moon surface, causing a harder landing than planned.
When I first heard that they might have landed upside down, a part of me felt a pang of indignation and condescension, for about ten seconds. But I kept my mouth shut and realized these things are hard and something I didn't think of in the ten seconds as an armchair lander-designer might have occurred.
I found the tone of your comment pretty condescending, tbh. Hot landing is hot landing, and you're just speculating as a layman without any insight into their design and decision-making process. "Not simulating lunary gravity correctly." Like c'mon, that's just an insult to their intelligence.
Well, I did also mention stiffness which would relate to how much of a shock absorber effect there would be - preventing a bounce, so if they came in hard, that may indeed have been a factor. Maybe more to the point, it seems to be a fairly unforgiving mode of landing - maybe a NASA "bouncing ball" landing would have absorbed the harder landing without issue ?
Considering they knew these failure modes in advance, would it not have been prudent to put some sort of self-righting mechanism on the lander? Something like the mechanical arms you see in Robot Wars.
Mechanisms weigh a significant amount, long mechanisms like arms even more so. The more mass you spend on contingencies the less science you bring and the less valuable the mission is, even with a flawless touchdown.
It's big vindication for the bouncing ball approach. On the other hand the proximity of the moon makes it much more practical to field crude designs on a more frequent basis, or to put parts in orbit and assemble them into something more ship-like.
>It's big vindication for the bouncing ball approach
Not really, it's only been used for a few Mars missions, and not recently. For lunar missions you don't have the benefit of aerobraking, so you have to use so much fuel to slow down already, the math doesn't work out to use airbags at the last step.
> For the pinpoint landing, Sakai said, he would give SLIM a "perfect score."
I get being really, really proud of what you accomplished here, but...perfect? Really? You can't think of anything that maybe could have gone better?
I know it's a much more sophisticated problem than this, but my inner child thinks they just forgot "the planet(oid) has to be 'down' on both ends of the trajectory."
Other commentors are already pointing out how we went from kilometers of precision to a target of under 100m for this mission. But in practice, the team is confident it landed within 10m, which is pretty darn good.
On the context of the "perfect score", they initially gave themselves a 60 out of 100 score during their first press conference after the landing, and today a member of the audience explicitely asked them to revise that score knowing what we know now.
The speaker made the point that achieving that much of precision is just ground breaking and will completely change how we frame the "where do we land" question from now on,so giving it a perfect score is I think legit.
> but...perfect? Really? You can't think of anything that maybe could have gone better?
The context of the comment in the article referred to the “pinpoint landing” aspect of the landing. They narrowed down the landing range from 10,000m (10k) to 100m… two orders of magnitude.
From the the article,
emphasis mine:
> For the pinpoint landing, Sakai said, he would give SLIM a "perfect score."
> "We demonstrated that we can land where we want," Sakai said. "We opened a door to a new era."
I don’t know if this comment was made in English or Japanese, but I could see how a very specific comment about the pinpoint aspect of the landing in Japanese could be vague when translated into English.
I don’t think anyone is disillusioned enough to think the overall landing was perfect.
I think I was including "landing" in the relevant part of "pinpoint landing," not just the pinpoint element, which was what made it amusing. It did (apparently) "land" and not "crash" (or at least that's what I'm assuming from the fact that it isn't crushed/doesn't look like it made primary impact on some part that was not intended for impact), but "landing and falling over" doesn't normally earns a perfect score in any other common context.
I'm far from a translator... but it is not "We opened a door" but "A door is open to do missions that were not possible before". And he says that might be the most important takeaway from this project.
It's possible that the "minimum success criteria" or "primary objective" of the mission was to touch down intact within a radius. If that was achieved, then I think even in English it is reasonable to call the landing "perfect" in that it achieved all of the mission goals.
But that all depends on whether, "land upright and measure things with the expensive instruments we sent it with" was originally included as a primary objective and whether they've just moved the goal posts to minimize the appearance of the failure.
We seem to be losing the definition of words. From "perfect phone calls" to "perfect landings" just feels like moving the goal posts. Let's tone down the rhetoric a bit. A very successful landing. sure. Met all of the necessary goals even if wasn't as designed. sure. Perfect landing. Let's not be silly
I can see talking yourself into that definition, but any 4-year-old can look at that picture and tell you it didn't land perfectly. "No, silly! It's upsidedown!"
As a comparator for the pinpoint landing, the 1969 Apollo 12 landed within walking distance (535 ft) of the Surveyor 3 probe (which had landed two years earlier). It did have a human pilot who flew the descent and managed terrain avoidance.
You could engineer-ize that kind of problem. Maybe they plugged it into a complicated optimization package (want to minimize stresses from the landing) but forgot to add a crucial orientation related constraint…
Probably, almost certainly, that isn’t what happened. But it could!
FWIW, ISAS Director General(the "faculty" president, also a PM in another probe in the past) Hitoshi Kuninaka scored it at 63 points, with 60 for the landing and bonus 1 point each for scientific camera and two payload probes, you could say he's more based or whatever.
OTOH, in defense of the PM, the lander showed exceptional robustness against loss of an engine, so he'd have a reason to be proud of an explosionless landing.
Oh definitely not saying they shouldn't be proud. I'm intensely impressed, and they should be extremely proud.
It was just the juxtaposition of "perfect" with the picture of the thing upsidedown that made me laugh. "Near-perfect" I'll happily grant. Same with "impressive as all get-out." But "perfect" made me chuckle.
the main point seems to have been the precision with which they could land within a small region, and they did nail that. fta:
While most previous probes have used landing zones about 10 kilometers (six miles) wide, SLIM was aiming at a target of just 100 meters (330 feet). Improved accuracy would give scientists access to more of the moon, since probes could be placed nearer to obstacles.
The patient is alive. The lander still functioned on batteries. The solar panels are facing the wrong way, but they hope that the panels will produce power when the angle of the sun changes.
I cant help but think the Japanophile contingent on HN are super eager to grade-inflate anything and everything remotely applause-worthy Japan related in general.
Somebody had way too much fun writing the lead paragraph: "Japan's space agency said Thursday that its first lunar mission hit the tiny patch of the moon's surface it was aiming for, in a successful demonstration of its pinpoint landing system—although the probe appears to be lying upside-down."
If my kerbel space program has taught me anything it is that being upside down, side ways or whatever after a semi-safe landing, is only an issue if you want to go home.
Maybe I'm saying what you're saying, but that's a sentence, not a paragraph. I find it very annoying when I encounter these and it makes me question the competence of the author. It seems like the complexity of the grammar used reduces with more writing experience.
My opinion is that it should be:
"Japan's space agency said Thursday that its first lunar mission hit the tiny patch of the moon's surface it was aiming for. It was a successful demonstration of its pinpoint landing system although the probe appears to be lying upside-down."
The snark is strong in this - but I'll resist and just note that landing on the moon is hard. I reckon they did exceptionally well with nailing the landing site, and hope that next time they'll be completely successful.
Not mentioned in the article but touched in the conference is this is at least third time a 500N-class thruster failed on an ISAS probe. Last time it blew off on Akatsuki/PLANET-C Venus probe, before that was Nozomi/PLANET-B Mars probe, both cut apsis burn shorter than intended and later determined to be from salt buildups due to propellant leaks. Apparently apogee motors has been proving harder to do right than anticipated.
Readit News
https://www.bbc.com/news/science-environment-68091389
That juxtaposition is just uncanny. This japanese mission is surprisingly kerbal.
https://en.wikipedia.org/wiki/Smart_Lander_for_Investigating...
https://www.upi.com/Science_News/2024/01/25/Japan-SLIM-landi...
It was meant to use a rather odd "two-step" landing procedure where it first touches down on the lunar surface on it's rear/primary landing gear, then pivots forward/falls under gravity to also touch down on the front/secondary landing gear.
Presumably this landing procedure was simulated under lunar gravity, but it seems there are multiple potential failure modes:
1) After rear "leg" touchdown, over-rotate forwards over front leg (ending up on back), OR
2) After front "leg" touchdown, bounce/recoil backwards off front leg, flipping onto back, OR
3) Front landing gear hits rock on one side (left or right), thereby flipping it sideways onto back
The whole procedure seems to rely not only on having correctly simulated under lunar gravity (and with correctly simulated stiffness of the vehicle) to avoid scenarios 1) & 2) (which would be different under earth gravity), but also the softness of the landing site being uniform and as simulated - otherwise if landing site surface was harder (rock) or softer than expected, or uneven, then this type of pivot and bounce/not landing would not go as planned.
NASA seems to have done a better job in designing fool-proof landing mechanisms, from the bouncing ball of the first mars rover, to the sky-crane landing of the latest one (which appears over-complicated, but no doubt was chosen at least in part because it is in fact more predictable than the alternatives).
I wouldn't read too much into that choice.
More likely the velocity was a tad too high.
That's why I was never comfortable stopping in rollerskates or ice stakes.
> One of the lander's main engines lost thrust about 50 meters (54 yards) above the moon surface, causing a harder landing than planned.
When I first heard that they might have landed upside down, a part of me felt a pang of indignation and condescension, for about ten seconds. But I kept my mouth shut and realized these things are hard and something I didn't think of in the ten seconds as an armchair lander-designer might have occurred.
I found the tone of your comment pretty condescending, tbh. Hot landing is hot landing, and you're just speculating as a layman without any insight into their design and decision-making process. "Not simulating lunary gravity correctly." Like c'mon, that's just an insult to their intelligence.
[0]: https://news.ycombinator.com/item?id=39131130
[1]: https://www.bbc.com/news/science-environment-68091389
The purpose of this landing design was explicitly to allow landing in areas that wouldn't previously be considered acceptable: slopes.
Not really, it's only been used for a few Mars missions, and not recently. For lunar missions you don't have the benefit of aerobraking, so you have to use so much fuel to slow down already, the math doesn't work out to use airbags at the last step.
I get being really, really proud of what you accomplished here, but...perfect? Really? You can't think of anything that maybe could have gone better?
I know it's a much more sophisticated problem than this, but my inner child thinks they just forgot "the planet(oid) has to be 'down' on both ends of the trajectory."
On the context of the "perfect score", they initially gave themselves a 60 out of 100 score during their first press conference after the landing, and today a member of the audience explicitely asked them to revise that score knowing what we know now.
The speaker made the point that achieving that much of precision is just ground breaking and will completely change how we frame the "where do we land" question from now on,so giving it a perfect score is I think legit.
The context of the comment in the article referred to the “pinpoint landing” aspect of the landing. They narrowed down the landing range from 10,000m (10k) to 100m… two orders of magnitude.
From the the article, emphasis mine:
> For the pinpoint landing, Sakai said, he would give SLIM a "perfect score."
> "We demonstrated that we can land where we want," Sakai said. "We opened a door to a new era."
I don’t know if this comment was made in English or Japanese, but I could see how a very specific comment about the pinpoint aspect of the landing in Japanese could be vague when translated into English.
I don’t think anyone is disillusioned enough to think the overall landing was perfect.
> いろんな意味で新しい扉が開き、今後、これまでできなかったようなミッションができるようになるのでは。そこが一番の意義ではないか
I'm far from a translator... but it is not "We opened a door" but "A door is open to do missions that were not possible before". And he says that might be the most important takeaway from this project.
https://news.yahoo.co.jp/articles/08a8bfdd7a41486140a97a8570...
Chuck Yeager
But the passenger payloads deployed correctly, so we'll count that as walking away.
But that all depends on whether, "land upright and measure things with the expensive instruments we sent it with" was originally included as a primary objective and whether they've just moved the goal posts to minimize the appearance of the failure.
[0] https://en.wikipedia.org/wiki/Apollo_12#Lunar_orbit_and_Moon...
Probably, almost certainly, that isn’t what happened. But it could!
OTOH, in defense of the PM, the lander showed exceptional robustness against loss of an engine, so he'd have a reason to be proud of an explosionless landing.
It was just the juxtaposition of "perfect" with the picture of the thing upsidedown that made me laugh. "Near-perfect" I'll happily grant. Same with "impressive as all get-out." But "perfect" made me chuckle.
S rank! Play next time for SSS!
While most previous probes have used landing zones about 10 kilometers (six miles) wide, SLIM was aiming at a target of just 100 meters (330 feet). Improved accuracy would give scientists access to more of the moon, since probes could be placed nearer to obstacles.
The problem may have been in their metrics. The KPI should have been a successful landing for the full range of 'successful'.
My opinion is that it should be: "Japan's space agency said Thursday that its first lunar mission hit the tiny patch of the moon's surface it was aiming for. It was a successful demonstration of its pinpoint landing system although the probe appears to be lying upside-down."
Deleted Comment
It’s vindicating to learn that even the pros struggle to land on a particular spot and end up knocking over their moon lander anyway.
Of course, their environment is much more detailed than KSP and doesn’t have a quick-save button.
Space is hard.