Mechanosynthesis core

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(TODO: Add stylized picture of single mill style core in volume showing wireframe box.)

Akin to processor cores defined by the local environments of arithmetic logic units the cores of APM systems can be considered to be the local environments of the places where mechanosynthesis is actually executed. They are located in assembly level 0.

Robotic mechanosynthesis cores can be divided into two classes: conveyor belt style and general purpose which may have a bit of a gray zone in between . [todo explain intermediate core]

Cores

General purpose cores

General purpose cores are robotic manipulators that can do special tasks that is create many of the physical permissible building material structures.

  • clearly separable from the transport structure delivering the moieties
  • more voluminous and slower than conveyor belt cores
  • more degrees of freedom and bigger build envelope - a wide variety of robotic manipulators can be used.
  • good random access to different tool-types
  • carrier pellets can make sense

[application spike-barrel...]

Conveyor belt cores

Converyor belt cores can complement general puropuse cores to gain higher speeds (synthethisation rates).

They are charactericed trough the following traits:

  • robotic transport structure and deposition structure are inseparable and may connect seamlessly to the tooltip preparation zone
  • active ends of conveyor belt cores are more compact than general purpose cores
  • possibly fewer degrees of freedom (e.g. only three if that suffices) & possibly smaller range of motion
  • limited random access to different tool types
  • no or very limited limited range of programmability (physical reversible hard-coding with diamondoid wedges may be useful)

conveyor belt cores of "molecular mill style" that use lots of axles likely consist out of a lot of structures with bending induced through dislocations or strain (strained shell structures). This suggests a rich indirect incremental technology improvement pathway leading there.

Core arrangement - Factory columns

Since the robotic mechanosynthesis cores form the lowermost and smallest assembly level the assembly mechanics need to be a lot bigger than the pieces they are handling (one to a few atoms) and the products. This limits the speed of a single core making it finish one product of its own size much slower than the higher up assembly levels can process and thus calls for high parallelism. Conveyor belt cores could e.g. only add a few stripes of a layer (unstrained standard infill) and then pass the extended diamondoid molecular element to the next conveyor belt core so that the conveyor belt tool delivery cores are combined with conveyor belt assembly threading each DME from its spawning to its reception point e.g. a redundant crystolecule routing layer.

General purpose cores could be used for the outer passivation and special non-regular or not yet automated structures and interspersed in the aforementioned threading.

For moiety transport for both core types rotative (normal mills or sideway mills or screw drives) or reciprocative molecular conveyor belts can be used.

Distribution of factory columns

It makes sense to include more Factory columns for the most often used standard parts than for more seldomly used parts. Columns for DME-to-DME-converyor-coupling adapters can be kept rather sparse since the adapters can often be reused.

Energy and power management

Main article: Dissipation sharing

(wiki-TODO: Add sketches for illustration of backshootup and internal oscillations: (1) geared torsional deflection decay, (2) much simpler for easier understanding map system to linear reciprocative configuration (one tip-gap - one transmission-rod - one tip-gap) )

Inseperability from energy subsystem

Since mechanosynthesis operations often deliver energy rather than consuming it mechanosynthetic cores cannot be clearly separated for dedicated energy providing subsystems (generators). Energy can flow both ways, in and out of the system.

Backshootup

The balance of forces pulls to lower potential energies, but that is not what determines the systems direction of motion. If not taken care of the whole complex chain-tree of gears and axles sitting between all the mechanosynthesis tips and all the generator/absorber tips first "falls" down to lower potential energies converts this efficiently into kinetic energy and followd by an immediate back conversion. That is the system shoots right back up out of the lower potential energy state again. All as a rigid very complex whole. That is not exactly what is desired.

Related: How friction diminishes at the nanoscale

Internal oscillations

Also possible flexure of torsional compliance DOFs of the axles between the systems (intra- and inter-system) need to be considerated.

Low frequency limit

In the low frequency limit ("mechanostatics" / statics) this mechanical issue may be more pronounced than in electrical systems since in most electrical systems systems voltage is not high enough such that the small self-capacitance of wires (corresponding to inverse stiffness aka compliance in mechanical systems) can cause any significant current.

Nominal frequencies

An other issue at higher frequencies is that there will be complications if the outermost spacial dimensions of an independent power equilibration cell gets near to the wavelength that is natural for the system at its nominal operation frequency.

To estimate the wavelength one needs the speed of sound for the system. The speed of sound in diamond is 12km/s with 1MHz of assumed operation frequency this would give 12cm (plenty of space). But the speed of sound may be a very bad estimate. It's better to get the systems speed of sound from the stiffness of the axle and gear system system.

There is the contribution of:

  • (1) the angular stiffness of the axles
  • (2) the gear teeth contact stiffness (strongly depends on gear compression pressure)

If those two are not matched up estimation of the speed of sound runs into complications. Is a simple average good enough?

(TODO: look into that math)

Stiffness matching

A mismatch in stiffness also leads to wave reflections, which are likely not desirable. Inter-meshing gear teeth rows provide stiffness only from a single line while axle stiffness comes from the whole area. So matching axle stiffness to gear teeth interface stiffness may lead to the effect that for the minimal possible gear-size a matching axle diameter would be smaller than atoms, and for axles with minimal sized diameter gears will be so big that (1) pressing them together hard enough to get the desirred stiffness may bend the axles and (2) the gears may introduce a lot of inertia of mass. Possible solution: hollow axles.

Side notes:

  • Stiffness matching is not really possible and done in macroscale machinery.
  • A bonus of bigger gears is that they can (if helical in design) average out atomic bumps better (better superlubricity) and thus can run smoother.

Well controlled dissipation: preventing backshootup and internal oscillations

One probably wants to avoid both "backshootup" and "system internal oscillations" by proper minimal damping (thermalizing kinetic energy) at the right times at the right locations. Whatever those are.

With slower operation speeds one can get away with less dissipation. (Main article: Low speed efficiency limit)
To regulate speeds smart and efficiently (not a stupid throttling break) it may be possible to use a mechanical analog to pulse with modulation.

Curiosity: recurrence of internal oscillations - if undamped

Warning! you are moving into more speculative areas. Barely damped high Q systems (aka well isolated systems) allow mechanical oscillation waves to travel long distanced around corners and through complex systems.
(Can these still be called phonons? "mechanocircuit phonons" ??) Wave propagation also can split up (fracture) or fuse together (superpose) through forking points (aka mechanical differentials). Superposition of time shifted reflections may lead to some quasi-thermalisation of waves in the closed system. Possibly with rather short recurrence times. Possibly shorter than the true dissipation out of the system, so that in-closed-system-recurrence can be observed.

Motion

Mill style mechanosynthesis imposes a rotative motion and specific (that is circular) approach path profiles on the process.
An obvious question is then: Does this need to be compensated (e.g. by compmementary workpiece holder plattform motion) or can this motion be used as is? Maybe the answer is different for different deposition and abstraction processes.

If motion compensation is necessary:

  • then how to distribute it between the tooltip-holder-drum and workpiece-holder-plattform?
  • then how does this effect the continuity of motion?

When there's no fully continuous motion then there are many possibilities for intermittent motion:

  • only wavy or
  • with full stops or
  • even with partial backwards motion)

(Something like a geneva drive is probably too crude.)
Large scale full stop intermittent motion may cause serious losses due to radiation of vibrations. local mass motion compensation might be of interest.

Related

For Standard parts that could be churned out by mechanosynthesis cores check out:

External links

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