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Still unclear what happened. Did they not anticipate a big moon hole or did navigation fail when the rangefinder failed?
by 1970-01-01 2y ago
Still unclear what happened. Did they not anticipate a big moon hole or did navigation fail when the rangefinder failed?
- ceejayoz 2y agoI'm not sure what you find unclear. Navigation was fine - "Athena knew where it was relative to the surface of the Moon" - but without a working altimeter it was kinda fucked for actually touching down. Hard landing, skid, tip.
- walrus01 2y agoWas there no functioning laser or radar altimeter for the final descent phase?
- ceejayoz 2y ago"However, the lander's altimeter had failed."
- 1970-01-01 2y agoLooking at this closely, it was working, however it was noisy. I speculate that they didn't correctly anticipate the moon dust problem. Laser rangefinders may not be a workable solution for future landings. So engineers at Intuitive Machines had checked, and re-checked, the laser-based altimeters on Athena. When the lander got down within about 30 km of the lunar surface, they tested the rangefinders again. Worryingly, there was some noise in the readings as the laser bounced off the Moon. However, the engineers had reason to believe that, maybe, the readings would improve as the spacecraft got nearer to the surface. https://arstechnica.com/space/2025/03/intuitive-machines-second-attempt-to-land-on-the-moon-also-went-sideways/ https://arstechnica.com/space/2025/03/intuitive-machines-sec... https://www.space.com/nasa-moon-landing-dust-concerns.html https://www.space.com/nasa-moon-landing-dust-concerns.html https://en.wikipedia.org/wiki/Lunar_horizon_glow https://en.wikipedia.org/wiki/Lunar_horizon_glow
- ceejayoz 2y agoNoise at 30km altitude probably points more towards a sensor issue than dust.
- Aspos 2y agoMay it be that laser bounced off exhaust plume?
- lightedman 2y agoI think it would be unlikely that a plume was caused from 30km away on something with no atmosphere.
- echoangle 2y agoUnless their processing is very weird, that shouldn’t be the issue. You send a pulse and record the output of a detector to listen for the reflection. If the laser is reflected at the plume, you should get some pulses very quickly, but also faint and spread out in time, which you would be able to tune out. And the real response from the ground should be more narrow because it’s reflecting at a single distance. If very short range noise influences the signal when measuring 30km real distance, you’re doing something wrong.
- inamberclad 2y agoLaser is angled outwards at approx 45 degrees, I think it's well away from the exhaust plume.
- numpad0 2y agoLRFs and radars on the Moon has been fine for a long time, it can also be angled away from gravity axis and multiplied by sine theta if needed.
- 1970-01-01 2y agoIf navigation was fine, why was touchdown on a plateau?
- ceejayoz 2y agoBecause "where am I" and "how high am I over that position" are very different things. Visual demonstration of being at the wrong altitude in the right spot: https://www.f-16.net/f-16-news-article968.html https://www.f-16.net/f-16-news-article968.html
- deleted 2y ago[deleted]
- echoangle 2y agoIf you don’t know your altitude, navigation isn’t fine though. Navigation should give you a position in all axes.
- JshWright 2y agoThe top-heavy design didn't help things either. I'll be shocked if they don't go three-for-three on landing sideways given IM3 has the same tall design.
- ceejayoz 2y agoThe company claims it's not as top-heavy as you'd think from pics: https://www.theregister.com/2025/03/07/intuitive_machines_landing/ https://www.theregister.com/2025/03/07/intuitive_machines_la... > At his press conference earlier today, Altemus defended the design, saying the spacecraft doesn’t have a high center of gravity because most of its cargo attaches to the base of the vehicle. He said there were no plans for a radical rethink of his company's design. (We see this in returning F9 first stages, as well.)
- sandworm101 2y ago>> The top-heavy design didn't help things either Just wait for SpaceX to start trying to land starships on the moon. Also vertically. Also doomed to tip over whenever the surface is slightly out of spec. https://www.spacex.com/humanspaceflight/moon/ https://www.spacex.com/humanspaceflight/moon/
- JumpCrisscross 2y ago> Just wait for SpaceX to start trying to land starships on the moon. Also vertically SpaceX has done it. To date, other nation-states have tried and failed to replicate their achievements in this domain. IM’s design is wrongly optimised and probably requires a rethink. That the CEO won’t contemplate this isn’t a great sign for the company.
- CamperBob2 2y agoSpaceX has done it. SpaceX has landed Starship on the moon?!
- JumpCrisscross 2y ago
- nomel 2y ago> "Athena knew where it was relative to the surface of the Moon" - but without a working altimeter it was kinda fucked for actually touching down. Z is an axis that exists in our 3d world, and a required value for any relative position, which means it DID NOT know where it was, relative to the moon.
- PantaloonFlames 2y agoYa the wording was not quite … satisfactory. I think they meant , it could tell X and Y, but not Z. But all three are important. Related - I’m not clear how the article can describe that landing as “not crashing”. If that was not a crash, what was it? Will they call it a crash only if there are Hollywood-style explosions?
- jacobgkau 2y agoBringing "Hollywood-style explosions" into it is a little much. If you slam the breaks on in your car, your tires hit some debris in the road, and you spin around and end up somewhere you didn't intend to be, but the car wasn't meaningfully damaged (i.e. you didn't hit other cars or manmade structures), you made a dangerous uncontrolled maneuver, but you didn't crash. That seems more like how they're describing this "skid." Relevantly, it sounds like this lunar spacecraft was still functioning after the hard (non-)landing. The only reason it died after that was because of debris settling on the solar panels, which made it run out of power.
- PhasmaFelis 2y agoIf you do something with your car that ends up with it skidding on its side, that's a crash by any possible definition.
- jacobgkau 2y agoProbably, but this is a space probe, not a car. It's lighter than a car, and is operating in an environment with less gravity.
- meindnoch 2y agoBut if they knew where it was relative to the surface of the Moon, they could have subtracted that from where it wasn't, or where it wasn't from where it was (whichever is greater), to obtain a difference, or deviation. The guidance subsystem could then use deviations to generate corrective commands to drive the missile from a position where it was to a position where it wasn't.
- martin_drapeau 2y agoScott Manley has a great video explaining what he thinks happened. https://youtu.be/ISZTTEtHcTg?si=0LZFyiCysBiFZrMz https://youtu.be/ISZTTEtHcTg?si=0LZFyiCysBiFZrMz
- 1970-01-01 2y agoScott Manley and I agree that altitude signal shouldn't matter if navigation is correct. Athena simply risked touchdown, and it didn't find a flat spot, it found a hole. https://youtu.be/ISZTTEtHcTg&t=1158 https://youtu.be/ISZTTEtHcTg&t=1158
- ceejayoz 2y agoCan you quote the bit you think is relevant here? He's saying modern spacecraft can null out the horizontal velocity to land, but without an altimeter, you don't necessarily know when to do so, nor when to give the thrusters a little boost to avoid an obstacle you're about to hit, like a plateau.
- numpad0 2y agotldw: speculation: landed with too much lateral velocity and one of legs broke
- someothherguyy 2y agoDoes anyone know an extension that strips this tracking information and normalizes YouTube URLs?
- tennox 2y agoThere's tons... Firefox: https://addons.mozilla.org/en-US/firefox/addon/clearurls/ https://addons.mozilla.org/en-US/firefox/addon/clearurls/ Android: https://github.com/svenjacobs/leon https://github.com/svenjacobs/leon
- wruza 2y agoJust in case, I’m using my own violentmonkey scripts rather than hoping for extensions, and everyone can do that too (now only on firefox, I guess, and maybe brave). For example, I remove &t=<n> from urls that youtube added recently in addition to regular watch position restoration. This broke it for me and they don’t seem to plan a revert.
- russdill 2y agoIt touched down with a large horizontal velocity component
- PantaloonFlames 2y agoThat’s another thing that bothered me about this story. They said they knew where the craft was , relative to the surface of the moon. Wouldn’t that also mean they should know of any substantial horizontal (x/y) component of velocity?
- gtirloni 2y agoYes, through image analysis.
- marcosdumay 2y agoI don't know if it's the case, but there's a difference between knowing something and calculating its derivative fast enough for it to be useful.