A Philae Lander (like) anchoring harpoons on M-Type (metallic) asteroid. Can a nail gun and the effect of Cold Welding be a working solution?

Question

Everyone knows what happened to Philae lander (Rosetta mission). It is hard to predict the reliability of anchoring points before we know surface conditions on the asteroid. On the other hand, it is hard to plan any asteroid mining mission without a plan for anchoring points. Some practical ideas would be very welcome.

Cold Welding can bond two metals in vacuum because of the absence of gases and oxide layers. The metal atoms on the materials are able to join with one another when given enough pressure. The Galileo Spacecraft antenna did get welded to the spacecraft’s body, causing a failure.

Answer 1

Taking the point of homogeneity, internal structure and our knowledge of so called M-type asteroids further.

Given how data has been collected for some of the larger M-type asteroids there is still some uncertainty regarding the homogeneity and internal structure of such asteroids.

One of the better indicators of the homogeneity and internal structure of a asteroid is it bulk density. The higher the density, around 8 g/cm³, the more likely its internal structure will resemble a block of metal. The density of iron is 7.87 g/cm³, steel 8 g/cm³ and copper is 8.93 g/cm³. Obtaining the bulk density of an asteroid is difficult because accurate measurements of its mass and volume are required.

A number of the large M-type asteroids have bulk densities between 3 and 4 g/cm³. This indicates such asteroids may be porous and thus more consistent with a rubble pile or they may contain silicate minerals and thus resemble stones (crystalline) - something analogous to basalt which has and average density of 2.9 g/cm³.

Returning to your question. Using a high powered nail gun on a block of metal might work if surface debris can be removed prior to using the nail gun. If used on a crystalline metal rich asteroid, a nail gun could shatter the asteroid or break it up into discrete chucks, particularly if the asteroid contain discontinuities and planes of weakness. I would not recommend considering using a nail gun on a rubble pile.

Alternatively, resin grouted rock bolts might be an option. A hole would be drilled into the asteroid, preferably under rotation, with no hammer to minimize the possibility damaging the asteroid. Clean the hole with a blast of air. Insert the anchoring bolt with a resin cartridge and rotate to break the cartridge and encase its contents around the bolt.

For the resin to set a setting agent is required. This can either be done by inserting a cartridge of resin and one of the setting agent. Alternatively single cartridges are available that contain both, each separated by a membrane. Rotating the bolt and the cartridge breaks up the cartridge and given the correct rotation time everything sets nicely. To assist with mixing the resin, the part of the anchor inside the hole would have flat "paddles" or flared out parts along its shaft.

If resin bolts aren't practical, then mechanical anchoring, where a deformable barb, or expansion shell grabs the sides of the drilled hole, securing the anchor.

Answer 2

Answer: No, a nail gun can't cold weld to an asteroid.

Grappling anything in space is problematic. Partially because almost everything has angular momentum, partially because any contact with the object will produce equal and opposite momentum in the grappling spacecraft and partially because most objects you want to grapple (asteroids, debris) are either hard or friable.

One approach is to snare first, before trying to place hard anchors. See Is there an elegant method to stop an asteroid's spin? and Can space debris capture be modeled on surgical grapple baskets?

For reference, here is a picture of a surgical snare:

It's very unlikely "cold welding" will attach a grabble to an asteroid, especially using a nail gun. According to Wikipedia, cold welding requires "two clean, flat surfaces of similar metal" being pressed together. In conventional cold welding, high pressure is required. These requirements are unlikely to be met on the surface of an asteroid.

An alternative would be explosion welding. Like cold welding, it is a solid state welding process, but it is more tolerant of surface contamination and can weld dissimilar metals.

Answer 3

“…on M-Type (metallic) asteroid)”

Which one(s)? You presume not just monolithic asteroids but a monolithic type, in a deterministic and discrete typing system. That is, you presume too much. We have already spent mucho millions on a mission, and yet we still have handwaving notions about the homogeneity, petrology, etc. of Psyche. The gravity of Psyche also falls in a weird zone, not negligible, yet different enough from Earth-Moon to be an issue, not handwavable.

“ Or are there better alternatives?”

The alternatives that are robust to failure- mechanical failure, sure, out to failure of the imagination: a surface not anticipated, because why would humans anticipate it?

Terrestrial mentality is good at terrestrial solutions to terrestrial problems. People spend time, and get paid, to not be in the rut of terrestrial thinking. It’s harder than you think (or handwave away instead of thinking, or never even bother to even bother).