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Reading about Lunar Crater Radio Telescope and Lunar regolith thickness and composition, (roughly 5-10m of soft soil) and anchoring in soft regolith, would it make sense, in order to anchor large structures on the moon, like a kilometer sized dish-shaped hanging mesh, to plant stakes first, by jettisoning them before landing burn of the dedicated spacecraft, so that part of their kinetic energy is used to plant them at some required depth and make sure anchoring is strong enough?

basically the idea is to use part of deorbit kinetic energy to plant anchoring stakes around the dish/mesh/radiotelescope site, before the spacecraft they've been jettisoned from arrives on site. instead of soft landing a robot that has to wallclimb crater's rim and drill and secure anchorings on site from the surface.

Those stakes would be released at some velocity and altitude prior to spacecraft landing, then a rover can attach a cable to each anchor.

Is this concept valid or meaningless and why?

(those stakes could also be solid balls attached to cables that stay accessible on surface, so that straight planting attitude of each anchor once released is one issue less)

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Putting it bluntly, I don't like your idea.

In addition to needing accuracy and precision from afar and all the problems associated with that, as mentioned in the answer by @Nuclear_Hogie, I get the impression that like many others you are making invalid assumptions about lunar regolith.

Until now, there have only been six human missions on the Moon, two Soviet Lunokhod rovers and one Chinese rover. The longest hole drilled on the Moon was 292 cm, by Apollo 17. Thickness and properties of lunar regolith vary from site to site.

Given the history of meteor bombardment of the Moon over nearly 4.5 billion years and the lack of an atmosphere, lunar regolith will not have a uniform consistency. It is composed of items as small as a silt particle to boulders as large as a house; all having been ejected from craters during meteor impacts. Lunar regolith is not a uniform, smooth, soft material. It is a jumbled up mess, with boulders, stones and dust of varying sizes above and below the surface. Boulders that were once on the surface have been covered by the ejecta from latter bombardment craters.

The landing of Apollo 11 took longer than expected because Neil Armstrong had to overfly a field of boulders that were in the location where the LEM was originally going to land. Because of this, he only had about 30 seconds of descent fuel left when he landed.

If someone where to try what you are proposing, how would it be known that any pylon would not hit a large boulder that might be just below the surface?

On Earth, such a scheme would never be attempted, for various reasons. A site inspection would be done, geological and geotechnical assessments would be made and the appropriate anchoring method decided by civil engineers. Due to cost and time constraints people appear to want to avoid doing this for the Moon and Mars. Be prepared for failures.

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    $\begingroup$ I think avoiding hitting large rocks from far away is the critical part you raised. I assumed lunar regolith as some homogeneous slightly moist sand, while it isn't $\endgroup$
    – user19132
    Oct 27, 2023 at 15:26
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    $\begingroup$ The odds of any particular anchor hitting a boulder are probably relatively low. If one does then they would try again nearby with another anchor. Depth of the anchor probably doesn't have to be that precise as long as it meets the minimum, so different regolith conditions may not be that much of a problem. Comparing to installations on Earth with inspections etc. may not be as relevant since safety isn't really an issue if we assume that all construction is done with robotics. I would think simple rover photos of the anchor would confirm that it inserted deep and straight enough. $\endgroup$ Oct 28, 2023 at 2:14
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Accurately landing something on the moon is tricky business. Even performing a controlled landing within several hundred meters of your target is a noteworthy achievement. Dropping pylons from orbit on a ballistic trajectory will almost certainly have worse precision. Unless your structure can handle lots of leeway in where the structural members are placed, you simply won't be able to place them accurately enough with such a method - you'd be lucky to land multiple shots inside a 1km-wide crater, much less on its rim.

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    $\begingroup$ @jkztd I could see it working for a single pylon that you don't need to land precisely. But I have a hard time thinking of an application where you'd want the pylons 500m apart, but would be equally fine with them being 1000m apart or right on top of each other. We're talking about variability on the same scale as the structure being built. $\endgroup$ Oct 25, 2023 at 20:49
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    $\begingroup$ @jkztd actually if there was a bit of an atmosphere, I wonder if the flying stakes could have a camera in the nose and moveable tail fins for guidance and potentially improve their accuracy over dead drop in vacuum. You'd probably want a fairly low pressure atmosphere for this so that the effects of changing crosswinds weren't too large. Just a thought. $\endgroup$
    – uhoh
    Oct 25, 2023 at 21:25
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    $\begingroup$ Stakes could easily be guided. Get Elon and co to provide some :-) $\endgroup$ Oct 26, 2023 at 11:54
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    $\begingroup$ @jkztd Another important factor is that dramatically changing the weight of the vehicle during a de-orbit maneuver adds immense complexity to the de-orbit. $\endgroup$
    – David S
    Oct 26, 2023 at 21:04
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    $\begingroup$ Could be done. Deploy all the pylons in one batch, they have members that push them into the right arrangement. (Remember, they're in freefall, such a structure need not be strong. I'm thinking perhaps some inflatable tubing, pressure providing the strength.) $\endgroup$ Oct 27, 2023 at 3:25
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This is an idea that has had some investigation and could work, but probably not for a high-precision device like a telescope.

See Weiss & Yung, 2010 for a feasibility study on deploying a (lunar) ground-based navigation system to guide rockets to a precision landing zone. They concluded that it was possible, but their requirements for precision were much lower than what would be required by a telescope.

Toldbo et al., 2022 took the idea further, focussing on modelling the distribution of the deployed poles and a design for the probes and their deployment. As you can see in their paper, the precision is very low - good enough for navigation, but not telescopes. Additionally, the ground angle for successful penetration is relatively low: deploying probes on the edge of a crater is almost certain to destroy the probe.

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  • $\begingroup$ thanks for both links! $\endgroup$
    – user19132
    Oct 27, 2023 at 19:13
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The technique is popular for anchoring structures in deep water engineering. See for example torpedo pile, and similar.

The problems I see are the hardness of lunar regolith compared to marine sediment, probably solvable using hollow point anchors that generates a shaped jet similar to armour piercing shells, and the lack of an atmosphere to provide aero/hydro-dynamic stabilisation of the anchor while it is falling. Although lack of aerodynamic forces greatly simplifies aiming, the impact point is fixed and will not alter once the anchor is released.

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I see a critical problem here: Before you go embedding pylons in the ground you have a geologist check out what you're embedding them into. This is going to be an extra severe problem because you're driving them in one bang. It's like trying to use a nail gun without knowing what sort of material you're driving the nail into.

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    $\begingroup$ What if they have plenty of margin, they are dropping an anchor x meters long that just needs to penetrate at least y meters into the ground for stability, but no more than z meters to ensure that the attachment is above the surface. Assuming that by then they will know more than we do now about typical regolith conditions. And perhaps a rover has drilled some core samples in the target area, so they have reasonable confidence that it will go in okay. Bad luck hit a rock, try again a few meters away. Or try an anchor with different length and weight. Other methods are not risk free either. $\endgroup$ Oct 28, 2023 at 2:30
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This is a largely impractical concept.

As stated by Nuclear Hoagie, landing from orbit is difficult as-is.

In regards to your idea, to use some of the orbital kinetic energy to plant the stakes is not practical. The majority of orbital energy is in the form of lateral movement. Essentially, you are moving parallel to the ground. To de-orbit, you must get rid almost all of the lateral movement to land, even if you're using a runway. The space shuttle's orbital speed is 7.68km/s and its touches down at 0.1km/s.

Lateral movement means your anchors will not be perpendicular to the ground when they hit. They will be angled to some extent. Angled anchors means it is not as secure structurally as it would be if placed perpendicular to the ground (straight down).

Further, to ensure the pylons self plant and don't bounce off a rock and go flying into some sort of potentially dangerous manner, then the pylon will need enough energy to pulverize surface-level rock. This means you're going to create craters and send debris flying everywhere during a landing, as well as somewhat reshaping the surface you're going to be building on. This adds a lot of additional complications to account for.

If you're releasing pylons during a de-orbit maneuver, you're altering the flight characteristics of your craft during a critical event. These pylons are going to be heavy. The landing vehicle would need to be significantly heavier than the pylons for the weight change to be negligible. Otherwise, once a pylon is released, it is going to alter the flight of the vehicle. Not only in trajectory but in weight, which completely alters fuel consumption, the amount of boost needed, just about every important detail of landing is going to be adjusted. That is a lot of added complications during an already difficult task.

While I believe a lot of these are theoretically solvable engineering challenges, it introduces more complexity and problems than it solves.

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  • $\begingroup$ It would rather be released at an altitude/trajectory imposed by kinetic energy required to plant something. Might be after some large deorbit burn, and separation occur almost vertical or with low horizontal velocity relative to target, I messed the question title smh. $\endgroup$
    – user19132
    Oct 27, 2023 at 15:30
  • $\begingroup$ @jkztd I believe your concept is within the realm of possibility. As in, I think it can be done with enough of the engineering problems solved. I just don't think the benefit outweighs all of the added complexities and complications that it introduces. To me, figuring out and solving some of the challenges in the way of this idea sound quite interesting. The deal breakers are safety concerns with pylons that don't embed and debris from pylon impacts. No atmosphere means a lot of debris. So each deployment will likely have a restriction zone of miles around it. $\endgroup$
    – David S
    Oct 27, 2023 at 16:17
  • $\begingroup$ DavidS - flying debris etc. would prevent this method from being used to add facilities to an existing populated lunar base. But it wouldn't have those restrictions during initial construction of a base, or building structures not located in populated areas. As for pylons that don't embed, then they try another one. I would think that based on how deep a pylon inserted into the ground, along with its vertical orientation, engineers could make a reasonable estimate of its load bearing capability, since presumably they would build in plenty of margin to accounting for various regolith conditions $\endgroup$ Oct 28, 2023 at 2:59
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In addition to other answers, it should be noted that there are several methods routinely used in Earth to anchor pylons. Elevating the pylons with a large crane on an helicopter, although imaginable, is not one of them, because it wouldn't be practical or efficient.

Surely some of the usual earthly methods can be used in the Moon. Anchoring pylons by vibration or by percussion are likely to work well, and although they rely on gravity and the weight of the pylon or the weight of the hammer are reduced in the moon, the weight of soil is also reduced, and therefore that methods may work more or less similar as they do on Earth.

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  • $\begingroup$ Common methods on Earth would possibly work, the complication is designing and building customized equipment, then transporting it to the Moon, where it will likely not work exactly as expected, possibly needing redesigned equipment to be sent. Even more complicated if it will operate robotically. None of this is insurmountable, but dropping an anchor from altitude may not be any more complicated overall than other methods. Some anchor drop tests could confirm the idea before committing to a major project using this method. $\endgroup$ Oct 28, 2023 at 2:45

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