Complete molecular manufacturing systems will have many subsystems, designed to meet many constraints

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A complete molecular manufacturing system (like a complete conventional manufacturing system) will be complex. It must have, for example:

• a casing to protect its interior from air, moisture, and dirt
• inlets for liquid feedstocks to supply molecules for processing
• molecular sorting mechanisms to purify inputs
• alignment and binding mechanisms to organize streams of molecules
• mechanosynthetic devices to process inputs into reactive tools
• mechanosynthetic devices to apply tools to workpieces
• mill-style mechanisms to join workpieces into larger blocks
• programmable mechanisms to join blocks into complex products
• a port to deliver finished products while protecting the interior space
• motors to drive moving parts
• computers to control material flows and assembly mechanisms
• stored data and programs to direct the computers
• data communication channels to coordination actions
• electrical systems to distribute power
• a cooling system to dissipate waste heat
• a structural framework to support the casing and internal components

Further, all these components must include adequate redundancy to enable operation the the presence of a significant fraction of failed nanoscale components (chiefly due to damage from background radiation). Individual operations must either be subject to testing and correction, or must be extremely reliable. Moving parts must be supported by bearings. Building blocks must be relatively rigid, and must be designed to fit and join when brought together with correct alignment. The analysis of molecular operations must take account of quantum phenomena and thermal vibration. The overall analysis must take account of entropy and thermodynamic issues. Finally, one must consider how such technologies can be implemented in the first place.

These subsystems and design issues are described and analyzed in quantitative detail in Nanosystems. Chapter 14 builds on these analyses to describe a reference manufacturing system with the following properties:

• mass < 1 kg (with a less hefty design than suggested by the above illustration)
• volume ~ 50 liters
• raw material input 2.5 kg/hr (chiefly acetone, oxygen from air)
• waste heat output 1.3 kW (air cooled)
• surplus power output 3.3 kW (from oxidation of surplus hydrogen)
• waste material output 1.5 kg/hr (chiefly water)
• product output 1 kg/hr (chiefly diamond)

Note that this rate is far less than what a simple scaling analysis of submicron assembly might suggest — as it should be, because larger, lower-frequency parts form much of the system. It is also substantially slower than the rates enabled by more recent convergent assembly concepts. A reanalysis based on these more recent concepts would describe substantially faster systems with limits set chiefly by cooling constraints.