Embedding foundations from low lunar orbit?

Question

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)

Answer 1

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.

Answer 2

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.

Answer 3

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.

Answer 4

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.

Answer 5

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.

Answer 6

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.

Answer 7

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.