Design of gem-gum on-chip factories

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For a general overview over advanced atomically manufacturing the technology level III page.

For a less technical overview about nanofactories check out the general overview page.

Basic energy balance

As carbon carrying resource material the fuel gas methane (CH4) or the welding gas acetylene (C2H2) is used. When those gasses are not burned but are being put together to products there still remains a lot of excess energy.

  • heating values: CH4 55,5MJ/kg > C2H2 49,9MJ/kg > Cn 32,8MJ/kg (graphite)

As resource material the carbon carrying "exhaust-gas" carbon dioxide (CO2) in ambient air can be used too. Its like "ash" on the lowest end of the carbon combustion chain thus the heating value of zero. If it is used as building material high amounts of energy are needed.

  • heating values: CO2 0,0MJ/kg < Cn 32,8MJ/kg (graphite)

Personal fabricator as stationary device

Depending on the used building material the needed or excessive energy must be taken from of fed into the power grid.
Gas lines (CH4) and atmospheric CO2 lend themselves as existing building material supply.

Related: Form factors of gem-gum factories

Personal fabricator as portable device

Huge amounts of energy cannot be provided from the small device. The resource-gasses (e.g. CH4 or C2H2 in capsules) must thus carry along enough energy for production. Simply radiating excessive heat away may slow down production significantly because of the high chemical energies involved. It may be better to balance the excess energy roughly to zero by using atmospheric CO2 as building material too. To pump high volumes of air silent medium mover metamaterials can be used.

Convergent assembly

See main page: Convergent assembly

  • Convergent assembly should not be confused with with exponential assembly which is an entirely different concept.
  • Convergent assembly (putting things together in a hierarchical way) is not a means to speed up production in general.
  • The motivations for why to do convergent assembly are outlined on the its main page.
  • The lowermost three convergent assembly steps follow naturally from the character of the technology - see assembly levels to understand this.

Covergent assembly crossing so many sizescales poses a challenge to visualizing it and making it intuitively comprehensible. Possible ways to visualize convergent assembly include:

Nanosystem units

Robotic manipulators

Threading by systems

Cooling, vacuum and other logistics

Macroscopically separating design considerations

assembly level 0 splits up in capturing resource molecules from liquid phase by sorting mills and mechanosynthetic peparation. It makes sense to do the former in a warm and the latter in a cold environment. Makorscopic separation (possibly in seperate devices) can be considered. (Aerogel?)

  • cooling & isolation

Although diamondoid mechanosynthesis works at room temperature cryogenic cooling will probably be employed just because it seems rather easy to do (see: "Diamondoid heat pump system") and error rates can be shrunken by many orders of magnitude.

General nanofactory design method

Given a set of "base units" for different components of the bottommost assembly levels their combination to form a full nanofactory unit can be determined by first finding the relevant quantitatively or at least qualitatively (set of choices) of evaluable relevant metrics and determine numbers of base units and branching factors based thereof. (constraint logic programming - prolog library clpqr?) might be useful. level throughput balancing output frequency of an assembly level == input frequency of the assembly level directly above

Design metrics

  • ratio of manipulator to building block in volume, number of atoms or mass

Performance limits

The ultimate performance limit is determined by the accepted dissipation heat at the lower levels the maximal acceptable accelerations at the higher convergent assembly levels. Designs leading to practical speeds at human scale lie way below the performance limits.

Power dissipation is only a limiting factor at the bottom-most assembly levels. At higher assembly stages bearing area per volume drastically falls. If bearing volume is kept constant via stacking the total speeds can be dramatically increased till resonance or acceleration limits are hit. Either one accepts overpowered upper layers of the nanofactory which only can be used to their full potential when prefabricated parts are recomposed or one may deviates from the layer structure to a more complicated fractal structure for the bottom layers. (dynamic drag and breaking losses)

Threading by pre-products

Depending on whether general purpose mechanosynthetic fabricators or mill style fabricators (serial chain of tools with no spaces) are used predominantly more or less layers and channels for threading parts by are needed [?].

Speed limit at the bottom

Low density of actual mechanosynthesis locations are the reason why the bottom layers in a nanofactory need to be stacked up. SVG

slow speed of assembly level 0: The mechanisms to assemble parts normally can potentially be smaller than the parts being assembled. Since The mechanisms to assemble minimal sized DMEs need themselves to be DMEs the mechanisms must have a similar size as the products they assemble. Since only a few atoms are added per assembly step the density of actual building sites of atomic size is rather low and consequently mechanisms at the bottommost layers are quite a bit slower than the ones above and need to be included in greater numbers.

If assembly units of an assembly level produce (pre-)products slower than the size-characteristic frequency the next higher assembly level demands one can stack assembly units and thread by finished (pre-)products. Assembly units can be stacked as long as the size characteristic frequency of the threading by mechanics is not exceeded.

Speed is also limited by the requirement to keep the rate of friction heat generation in bounds. See: Scaling laws#Speedup.

Ratios between levels

Layer and stage ratios: In any convergent assembly step a step size can be chosen. Big steps limit the maximum possible speed of the considered assembly level step but makes planning and programming more flexible and easier.

A step size that is easy on the human mind is 32 since two such steps roughtly span three (dezimal) orders of magnitude (a factor of 1000). Starting from 32nm only three steps lead to around one millimeter sized products.

Conservative estimation

There is reason to believe that steps of this magnitude won't make a nanofactory design unpractical. Todays homebuilt 3D printers can fill about 20000 voxels in one minute assuming 100 mm/second head movement and 0.3mm lateral voxel size. (20000 voxels are about the same as 32^3=32768) Since frequencies scale up with shrinking size going down doesn't change the troughput capacity.

Step sizes will probably just limit high recycling throughput but not throughput when mechanosynthesis is involved in production.

Influences of the branching factor

Branching factor: A branching factor of port area to block volume = n2/n3 leads to perfect size and frequency matching in an easy to design 3D iteration extruded 2D fractal design. Other ratios lead either to inefficient port space frequency and under used / under utilisized assembly levels or require 3D fractal designs that are more difficult to design. (There is no scale invariant design as baseline possible then)

Influences of assembly style

In any convergent assembly step one can choose from the different robotic manipulators to do the assembly. Mill style can (with the exception of the bottommost asselmbly level) have the smaller size and higher characteristic operation frequency of the lower assembly level. Single manipulator style assembly have the bigger size and smaller characteristic frequency of the upper assembly level. (Intermediate forms are possible). The choice depends on whether programmability or speed is the primary concern.

More complicated geometries

non stratified 3D fractal designs need higher convergent assembly stages (assembly level IV) to hold the structure together. They have the highest possible performance (way above practically needed levels) other limits are likely to kick in at some point. Finding a general design methodology seems to be a hard problem.For physical changes of such a design a complete microcomponent disassembly end reassembly is likely necessary.

Notes

  • (TODO: list basic nanofactory subsystems as exhaustively as possible)
    Maybe add these block diagrams: [1]

Related

External links

Articles from E. Drexlers Blog:

External references

  • Nanosystems chapter 14

(TODO: add morphlense image)

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