I'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.
> "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.
Ya 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?
Bringing "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.
"The only reason?" One reason for prematurely losing most of the investment is enough. The car analogy is inadequate but let's say my car skids gently into a position from which it won't start and I can't get out and I slowly die of starvation and/or hypothermia. Am I glad that I didn't "crash?"
But 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.
The 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.
> 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.)
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.
We can send small probes to image the moon in incredibly high resolution. It's a big place I'm sure there is a perfectly flat rock somewhere they can use.
Have you ever seen a perfectly flat rock anywhere on earth? One capable of supporting a large rocket? Also, the moon doesn't have the various navigation systems (GPS/radar) that is used when bringing rocket stages back the pad.
SpaceX has repeatedly and reliably landed vertical stacks. On any body. Out of the engineering problems inherent to HLS, sticking the landing isn’t material because for them, for that team, it isn't as novel a problem as e.g. in-orbit refuelling or getting Raptors to relight on the Moon.
Put another way, just because SpaceX has done it doesn't mean the same problem carries the same risk for a team like IM's.
A moving barge with a known flat surface of a known hardness and stability is a whole different category of difficult than doing the same thing on naturally occurring terrain with unknown voids, hardness, roughness and consistency.
They also have the atmosphere, with drag that will make all velocities trend towards zero. Don’t have that on the moon, gotta do it all with fuel. More than half of the energy she’s by the returning falcon is aerobraking.
Yes, the moon has substantially less gravity but it’s also exponentially harder to get the fuel there.
Lol. SpaceX has landed on prepared surfaces, concrete pads on land or on large barges. They literally have a big X to mark the target. Let's see them land on some random beach, an uneven surface that may or may not subside. But that is still peanuts comparted to the moon's surface.
> that is still peanuts comparted to the moon's surface
Sure. I'm not trivialising the problem in an absolute sense. Just going from floating barge or chopsticks to Moon is a simpler set of problems than reïnventing the sort of translational velocity and attitude control needed to get to first base.
For selecting and touching down on an unprepared surface, rockets are not the stepping stone. Start with helicopters. It is the same problem: can I land there and what will happen when I put weight on the surface. Try programing a large helicopter to identify and land on a random chunk of rocky terrain. It is not easy. And the bigger/taller the craft, the more difficult it becomes. Then add a 10-second time limit.
> You say this based on your history of landing rockets on the moon?
Actually, mini propulsive landers in lunar regolith stimulant. Yes. In atmosphere and with Earth gravity, both of which make it more annoying and more difficult.
For any of these landings, it's a problem of 3d positional/velocity precision. SpaceX has prove that they can reliably land on a target, usually within meters, with negligibly delta velocity on contact.
In other words, they've proven they have the control systems in place for placing a craft at a precise location, with a precise velocity. What requirement do you see outside of this that are far outside of placement and velocity? Autonomous mapping and adjustments for approach maybe?
Let's not assume they're going to try to use their current earthly landing legs.
> land on some random beach,
They did this I believe two starships ago, when they landed in the ocean. Came to zero xyz velocity some target distance above the water, and hovered for a bit. Unfortunately, the surface tension of the sea couldn't support the weight once they lowered for touchdown.
Which is not the future. Optical/lidar/positioning radio is the future, to make it closed loop (NASA’s Laser Retroreflector Array for high, lidar/optical for low altitudes).
> On a very highly engineered landing surface.
As I mentioned, we shouldn't assume the earthy landing legs are used. That would be a very silly assumption.
From what I can extract from your comment, you believe that the positioning system and landing legs are the issue, rather than the control systems. I suspect both are somewhat related: positioning system to place it over predictable regolith with some, yet-undeveloped, landing legs that need to work at 1/6th gravity.
I'm of the opinion that it's possible/solvable, as is NASA. It would be helpful if you would answer why you think it's not possible: what requirement do you see that make positioning and landing on regolith unachievable for SpaceX?
It may be possible. It may also be that the regolith is too fluffy in that area to support such a large structure without a pad. I don't believe we know.
Athena had multiple laser altimeters on board: they failed to get a fix, perhaps because of the weird surface.
It's my opinion that this isn't something that's easy to do, even for a company that has landed on Earth.
i think this becomes somewhat less of an issue once SpaceX gets Starship fulfilling contracts at scale. they're limited in width by the max payload faring width for Falcon 9, which is like half that of starship. add to that an exec claimed it's tall but not necessarily top-heavy as mass isn't evenly distributed throughout.
Looking 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.
Unless 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.
Hard landing, skid, tip.