View source for Why ultra-compact molecular assemblers are too difficult

[[File:OutdatedMolecularAssemblersConceptualIllustrations.jpg|400px|thumb|right|'''OUTDATED CONCEPT''' several highly conceptual illustrations of diamondoid molecular assemblers. Common traits: Just one or two manipulators, a gastight hull enclosing everything, full selfreplicativity, very small size ~100nm, more or less optionally some sort of mobility some swimming others here unspecified]]
[[File:self-replicating-assembler-unit.png|thumb|'''OUTDATED CONCEPT''' Artistic depiction of a mobile assembler unit capable of self replication (linked to a "crystal" of assemblers and thus not ''free floating''). An outdated idea.]]
Up: [[Molecular assembler]]
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= Why too difficult as a near term bootstrapping pathway =

'''Note that this is [[direct path]] context.''' <br>

The molecular assembler concept comes strongly tied with <br>
the hard insistence that a monolithic selfreplicating unit <br>
must unconditionally fit into a very small given volume. Typically (100nm)³ and a bit above. <br>
A volume determined by the throughput of a single macroscale SPM needle-tip. <br>

Means of [[non-replicative prescaling]] to lift that restriction are not considered in the molecular assembler concepts. <br>
Perhaps an additional reason for [[pathway controversy|criticism]] on the [[direct path]] which is often associated with [[molecular assemblers]]. <br>
See: [[Bootstrapping]], [[Bridging the gaps]], [[Parallel macroscale SPM scaling]] <br>
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. <br>
Work on (guess)estimating minimal molecular assembler size is limited likely for the same reason. <br>
All the work that does exist may well suffer from '''underestimation of size (and building difficulty)'''. <br>
That's not a failure of analysis but a fundamental lack of reliable analyzability. <br>
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 <br>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 <br>
predictions about minimal size of an ultra-compact monolithic replicating nanobot <br>
are for the most part a house of cards based on which one should probably not make decisions on. <br>

Much the same holds for an (more realistic and promising) [[early nanosystem pixel (direct path)]] too. <br>
But this one can just grow to the size it naturally needs to have. <br>

It gets even more unpredictable going to early nanofactories with [[assembly level 3]] and above. <br>
Side-note: The link here "[[assembly level 3]]" discusses the topic in the context of <br> 
advanced far-term systems which are much more amenable to exploratory engineering.

For a (not very useful) example of an unintentional analysis of molecular assemblers see <br>
Chris Phoenix's "Primitive Nanofactory Design by Chris Phoenix - October 2003" <br>
[[Discussion of proposed nanofactory designs]] <br>
This is pretty much about '''molecular assemblers tacked to a surface'''. <br>
Just small ultra-compact self replicative units at the very base. <br>
Putting focus on either more near term or more far term system analysis <br>
is a more productive use of time compared to putting focus on <br>
the maximally blurry spot in the middle of the bootstrapping pathway.

== 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. <br>
It gives a lot of [[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. <br>
Well, parametric designs are possible but not as trivial as just <br>
expanding an open grid of tracks to get the additional space needed <br>
in an [[early nanosystem pixel (direct path)]].

== Some concrete stuff - not necessarily major ==

Molecular assemblers often come with the expanding vacuum hull requirement. <br>
A quite complicated system adding to the [[replication backpack]] overhead.<br>
This can be entirely avoided. See: [[Vacuum lockout]]

Rather minor: Mobile molecular assemblers would need a potentially <br>
more complicated motion system moving the whole monolithic thing around.

== Capabilities and limits of SPM technology ==

=== Progress towards 3D capabilities ===

Recent capabilities with qPlus nc-AFM demonstrated <br>
– the capability of subatomic resolution scanning scanning of the top of <br>
very flat topped tetramantane molecules that are higher than the picked up CO molecule used for scanning. <br>
– the capability to pick up a C60 and covalently fuse it to 3 3D graphene nanoribbon. <br>
So going 3D is finally rudimentary experimentally shown possible as of 2025. <br>
{{wikitodo|Add references to these two experimental demonstration papers.}} <br>

Some form of [[SPM focus fusion]] might even allow to <br>
subatomically resolving qPlus nc-AFM scan the tops of surfaces <br>
that are not extremely flat, like e.g. an atomic step. <br>

STM can image atomic steps but structures are more often than not not properly interpretable by human intuition. <br> 
Rater they are more often than not highly deceiving, which can be a big problem. <br>

Anything notably beyond singe atomic steps is till closed off for both AFM and STM for a long time still <br>
as SPM needle tips of current technology are pretty much more like a giant balls rather than sharp tips <br>
as many (almost all) illustrations misleadingly might make one believe. <br>
See page: [[Tip surface folding shadow]]

=== Remaining severe limitations even in best case ===

Still with all that solved anything beyond the top <br>
and everything in the SPM tips [[tip surface folding shadow]] <br>
is permanently buried and inaccessible for imaging. <br>

There are only very few viable nondestructive methods (if any at all) <br>
to find out anything about what is going on down below the disjoint imageable patches <br>
of the very topmost imageable surface. <br>

And finding out about what is going on under the topmost surface is crucially important <br>
to the debugging of early prototype systems. <br>

This is related to data IO and it is one of the biggest challenges. <br>
The more '''distributed, flat, and spread out''' the early bootstrapping systems are, <br>
the more accessible they are for our current suite of analytic capabilities. <br>

This also makes for more economic side use opportunities.

=== Concluding with identification of much better approaches ===

Alternate systems that follow these constraints <br> 
('''distributed, flat, and spread out''') will be much more viable. <br>
See pages: <br>
[[Early diamondoid nanosystem pixel (direct path)]] & [[Mixed path]]

= Difficulty of KSRM type molecular assemblers in the context of presence of advanced naofactories =

* Ultra compact replicative molecular assemblers still hyperbolically more difficult with shrinking size. 
* A bit bigger totally possible by then. But still totally impractical. <br>Beyond making a point that they are not fundamentally impossible.

----

With advanced gemstone based [[APM]] and [[nanofactories]] <br> 
already being a fact of reality, designing and building things becomes much easier. <br>
So there's a good chance of someone coming along to design a compact <br> 
selfreplicating KSRM type molecular assembler just to show that it is <br> 
indeed physically possible (albeit not economically sensible). <br>

This thing will likely be notably bigger than the 100nm sidelength cube proposals. <br>
Mostly because … <br>
– size is not a problem at that point and … <br>
– designing bigger ones is hyperbolically easier. <br>

This of course leads to safety concerns. See: [[Reproduction hexagon]] <br>
At that point we might have already had to deal with more severe calibers of malicious nanosystems. <br>

No matter how far the tech advances, there will always be a certain volume below which <br>
any kind of monolithic selfreplicative molecular assemblers is truly fundamentally impossible. <br>
We have a true singularity here. <br>
Thus a hyperbolical drop in difficulty not a merely exponential drop in difficulty in size.

It may well be that the current ultra-compact molecular assembler proposals (100nm)³ <br>
remains hard even with mature technology (and AI designers). <br>
Time may tell.

= Related =

* Up: [[Molecular assembler]]
* '''[[Proto-assembler]]'''
* '''[[Molecular assemblers as advanced productive nanosystem (outdated)]]'''
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* [[Why ultra-compact molecular assemblers are too inefficient]]
* [[Why ultra-compact molecular assemblers are not desirable]]
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* [[Why nanofactories are not molecular assemblers tacked to a surface]]
* [[Early nanosystem pixel (direct path)]]
* [[Direct path]]