Why ultra-compact molecular assemblers are too difficult
Why too difficult as a near term bootstrapping pathway
Note that this is direct path context.
The molecular assembler concept comes strongly tied with
the hard insistence that a monolithic selfreplicating unit
must unconditionally fit into a very small given volume. Typically (100nm)³ and a bit above.
A volume determined by the throughput of a single macroscale SPM needle-tip.
Means of non-replicative prescaling to lift that restriction are not considered.
Perhaps an additional reason for criticism on the direct path which is often associated with molecular assemblers.
See: Bootstrapping, Bridging the gaps, Parallel macroscale SPM scaling
Asking for a smaller volume makes the problem nonlinearly harder (hyperbolically, there's a wall).
Unreliability of estimations due to inapplicability of EE
There is no book like Nanosystems that is analyzing molecular assemblers for a good reason.
Work on (guess)estimating minimal molecular assembler size is limited likely for the same reason.
All the work that does exist may well suffer from underestimation of size (and building difficulty).
That's not a failure of analysis but a fundamental lack of reliable analyzability.
The "good reason" is that exploratory engineering (EE) can't be well applied here because …
- … no large safety margin (forced so by assumed throughput constrains in proto-systems production)
- … heavily compounding errors due to subsystem inter-dependencies
- … degree of uncertainty usually not quantifiable
- … even qualitative uncertainty as one might eventually find out that
one unexpectedly needs some more subsystems that so far were not at all considered.
For the reason of failure of exploratory engineering in this context
predictions about minimal size of an ultra-compact monolithic replicating nanobot
are for the most part a house of cards based on which one should probably not make decisions on.
Much the same holds for an early nanosystem pixel (direct path) too.
But this one can just grow the size it needs to have.
It gets even more unpredictable going to early nanofactories with assembly level 3 and above.
Side-note: The link here "assembly level 3" discusses the topic in the context of
advanced far them systems which are more amenable to exploratory engineering.
For a (not very useful) example of an unintentional analysis of molecular assemblers see
Chris Phoenix's "Primitive Nanofactory Design by Chris Phoenix - October 2003"
Discussion of proposed nanofactory designs
This is pretty much about molecular assemblers tacked to a surface.
Just small ultra-compact self replicative units at the base.
Putting focus on either more near term or more far term system analysis
is I a more productive use of time.
Consequences of system isolation & predefined size
Lack of system modularity (BIG ISSUE)
Squeezing a system in absolute minimal space/volume tends to make it
non-modular conflation of concerns with a rat tail of consequences.
More complicated design-time expandability
If more space is needed the whole thing needs a redesign.
Well, parametric designs are possible but not as trivial as just
expanding an open grid of tracks to get the additional space needed
in an early nanosystem pixel (direct path).
Some concrete stuff - not necessarily major
Molecular assemblers often come with the expanding vacuum hull requirement.
A quite complicated system adding to the replication backpack overhead.
This can be entirely avoided. See: Vacuum lockout
Rather minor: Mobile molecular assemblers would need a potentially
more complicated motion system moving the whole monolithic thing around.
When too difficult as a far term ideal target
Well with advanced gemstone based APM and nanofactories
already a reality designing and building things becomes much easier.
So there's a good chance of someone coming along to design a compact
selfreplicating molecular assembler just to show that it is
indeed physically possible (albeit not economically sensible).
This thing will likely be notably bigger than the 100nm sidelength cube proposals.
Mostly because size is not a problem and designing nigger ones is hyperbolically easier.
This of course leads to safety concerns.
See: Reproduction hexagon
No matter how far the tech advances, there will always be a certain volume below which
any kind of monolitic selfreplicative molecular assemblers is fundamentally impossible.
It may well be that the current ultra-compact molecular assembler proposals (100nm)³
remain hard even with mature technology (and AI designers).
Related
- Up: Molecular assembler
- Why ultra-compact molecular assemblers are too inefficient
- Why ultra-compact molecular assemblers are not desirable
