Drexlerian nanotech

[Alphadon]

...doesn't work. Sure, our formulation does, but the original does not. This is not because the assemblers themselves wouldn't work; It's because building a large object atom by atom is horrendously inefficient. Consider you want to make a metal ruler. Would you rather put it together atom by atom or just cut it out of a larger block of steel? This would make assembling from feedstock less efficient than traditional manufacturing in some cases, even in our version. Consider that.

[Drashner1]

That something may be less efficient in some cases is not the same as it not working. Your characterization also leaves out a lot of details and factors in trying to make its point, including not providing a clear definition of what is meant by 'Drexlerian nanotech' or considering alternate ways of making a ruler or all the circumstances in which you might make a ruler (for example).

I think it's a bit of an overreach to say it 'doesn't work' in any broadly sweeping way, at least based on the information provided here.

Todd

[Rynn]

Your argument only holds if the principle of molecular assembly was to construct things by the linear addition of single atoms, but it isn't. You can look to current work in generalist chemical synthesisers for a sign of how things can work: massively parallel synthesis in interconnected chambers who send their products to the next chamber in a kind of dynamic assembly line.

Whilst a fabricator is very likely to be slower compared to an equally sized specialist machine (like a device for spitting out metal pipes) what they are is incredibly versatile. A combination of approaches at industrial levels almost certainly exists in OA with generalist fabs recycling and building specialist fabs as demand requires.

At a domestic level the low output relative to specialist systems is still sufficient that for the most part domestic goods will be produced on site by generalist fabs. One or two specialist fabs might exist a home (e.g a food optimised bioforge) but most things are made by the general fab.

[Alphadon]

What I mean to point out here is that Drexler made no allowances for progressively larger manufacturing implements. This is the crux of the problem: molecular assembly is good for things like transistors, but bad for things like a block of steel. Molecular assembly MUST be integrated with macroscopic processes to be effective. Which is why in some cases, a reconfigurable manufacturing machine may be better than a traditional universal assembler, as it can do things like build said ruler without the added task of molecular synthesis.

[Rynn]

I'm fairly certain that's wrong, though I've not read Engines in over ten years so you could be right and Drexler never spoke of anything beyond assembling purely at a molecular scale. Other writers of the time like Merkle certainly did:
http://www.zyvex.com/nanotech/convergent.html. The idea being that lower layers would eventually feed macroscopic parts into a chamber that would assemble them using more conventional manufacturing techniques (which incidentally is how OA fabs work). For blocks of metal you could have all sorts of chambers for this e.g. a vacuum chamber with a metal spray nozzle that "prints" via vacuum welding. In any case "Drexlerian nanotechnology" doesn't just mean only the exact things Eric Drexler hypothesised. It's everything based on that (namely the idea of diamondoid structures and a nanofactory).

And besides all that I think the argument is kind of moot. Even if Drexler didn't mention parallel convergent construction (which I'm very skeptical of) I'd argue the vast majority of science fiction authors who write about nanofactories understand that it would be a key part of it.

[Drashner1]

Engines of Creation does discuss the creation of macroscale objects, although it does not spend a lot of time on direct examples. There is more of a focus on pointing out that natural nanomachines (aka life) produces very large structures such as redwood trees and whales (none of which use progressively larger manufacturing implements btw), rather than direct examples of how this might be done.

However, there is a section in which a rocket engine is 'grown' in a vat using assembler systems that work in a more biological mode than via convergent assembly or physically moving components around.

In Unbounding the Future a similar system, that also makes use of 'pre-fab' parts that are described as needing specialized systems or otherwise taking longer to make in their own right, is used to also rapidly 'grow' a number of items very quickly.

In his more recent writing, Drexler has focused more on the convergent assembly type of nanoconstruction (using something very much like what OA would call a nanofab or nanoforge) and has argued that it would be a superior option to the more biological systems he initially described, at least for many applications.

As far as it being a requirement that nanomachines MUST be integrated into macroscale processes - the planetary biosphere does quite a lot without using macroscale processes. So that argument doesn't really hold much water that I can see.

Similarly, the argument about metal rulers seems to be a case of picking a specific example to try to support a premise, rather than a generalized argument with wide applicability. If one were to consider a wooden ruler then it would be literally impossible to make it without the use of (bio) nanotech to grow the wood.

Beyond that, the metal ruler example is ignoring the vast amount of infrastructure, in some cases spread out over a goodly chunk of the planet, and quite significant amounts of time, that might go into making the ruler before the user ever sees it. Depending on the design and feedstocks it might take a nanoforge only a few minutes or less to whip up a ruler, metal or otherwise.

In some cases, it may indeed be more effective to combine macroscale systems with nanoscale ones - an argument can be made that most animals and plants on the planet do this to one degree or another. But that is:

a) Not anything like an argument that 'nanotech doesn't work'

b) Not a universal case, since in some situations, purely microscopic tech would be used (e.g., an artificial immune system)

c) Not an argument that starting from a nanoscale or microscale 'seed' would never be an effective option since there are various situations where that might be desirable for other reasons beyond sheer speed (which is what most people seem to mean when they say 'effective'). For example, being able to send a thimble size spacecraft to Mars and have it grow a complete base or colony in a year or three might be seen as quite desirable even if a macroscale system weighing many tons might do the job in a matter of days. In this case, the reduced mass of the system and thus reduced cost would greatly outweigh the presume advantages of the macroscale option.

EDIT - It should also be noted that the current state-of-the-art is nowhere near as advanced as what Drexler proposed, and therefore it's a bit iffy to say that what he proposed 'doesn't work' when we've yet to reach the point of being able to even begin attempting to create the sort of devices he has described.

I tend to think of Drexler as somewhat akin to Leondardo da Vinci - even if what nanotech ultimately becomes doesn't operate in quite the way he describes, there is still something to be said for conceiving of and thinking about the idea in the first place, much as Leonardo is often credited with thinking about heavier than air flight. That modern aircraft have only a superficial resemblance to his designs doesn't invalidate his achievement in starting to think about such things long before.

Todd

[Rynn]

We don't have a like system on the forum, but if I could I'd like Todd's post. Completely agreed.

[Alphadon]

I never said that nanotech doesn't work in the first place. I merely noted that the initial ideas were flawed. And as for biology not using progressively larger systems-what do you think digestive organs are for? And we're nowhere near making wormholes either, yet we know exactly what does and doesn't work. Finally, remember that nanoassembly in air is pretty difficult from a mobility point of view-they don't have little thrusters, after all. And finally: biological cells are a highly controlled environment! Would bionano work outside of them? Has anyone seriously analyzed its feasibility? Don't get me wrong-I really hope it pans out, but I have doubts. After all, all the transhumanists and futurists before us had a bad tendency to get carried away.

I guess this is pretty far from the original topic by now, but I have a tendency to minirant. Sorry 

[Drashner1]

I never said that nanotech doesn't work in the first place.

Ahem. The first line of your first post in this thread basically said exactly that.

I merely noted that the initial ideas were flawed.

Hrm. That would be a matter of interpretation. If you meant to say the initial ideas were flawed in your opinion, then it might have been better to just straight up say that from the start, rather than making a fairly unequivocal statement on the matter.

More to the point, most new ideas are flawed when they are first conceived.

And as for biology not using progressively larger systems-what do you think digestive organs are for? 

Digestive organs are built from and by nanotech. Also, if you check my earlier post, I said:

a) the biosphere does quite a lot without using macroscale systems - not that it does everything without using them

b) In some cases, it may indeed be more effective to combine macroscale systems with nanoscale ones - an argument can be made that most animals and plants on the planet do this to one degree or another. But that isn't an argument against microscopic systems being used in others, nor is it an argument in support of the idea that 'drexlerian nanotech' (which is a rather imprecise term, as it happens) doesn't work.

And we're nowhere near making wormholes either, yet we know exactly what does and doesn't work.

No, we don't. We have theories about how wormholes might work, but those theories have changed numerous times over the years and probably will again before we ever get close to being able to make a WH. Also, there can be a large gap between having a theory about how something will work and actually creating a piece of hardware that will do something. The theory behind nuclear weapons was well established - yet it still took years of massive effort to actually make one and even today, it's not something that people can just whip up with no real effort. Also, the theories that OA wormholes are built on actually predict a vast number of different types of wormholes (think a 1 followed by tens or maybe hundreds of zeros), some stable, some not, some traversable, some not, and some with very weird properties, like turning anything that passes through them into antimatter or the like.

OA approaches this by saying that the different wormholes in use in the setting represent only those WH types that the archai have figured out how to create and stabilize (and presumably find useful - the EG doesn't know how many dud types they know how to create). But there are presumably a vast number of 'designs' that continue to elude them.

Finally, remember that nanoassembly in air is pretty difficult from a mobility point of view-they don't have little thrusters, after all. And finally: biological cells are a highly controlled environment! Would bionano work outside of them? Has anyone seriously analyzed its feasibility?

Plants and fungi seem to do quite well using nanotech while being immobile And biological cells essentially are nanotech. It should also be noted that Drexler has more than once said that nanotech would probably need a controlled environment in which to operate, unless the system in question was:

a) very advanced

b) explicitly designed to operate 'in the wild'

This point wasn't as emphasized in Engines of Creation, but was covered in more depth in Drexler's later works. In fact, Drexler has explicitly said that while he considered 'grey goo' to be a potentially serious problem when he wrote EoC, after thinking about it more he no longer does, at least in terms of such a thing happening accidentally - and if it was done on purpose then whoever did it would be employing very advanced and mature nanotech.

On a more general note, part of the issue here seems to be that we have different definitions of 'nanotechnology' running up against each other here. You seem to be defining it as only individual nanoscale robots operating independently and solely in an uncontrolled environment. I'm (roughly) defining it as tech that has components that have nanometer dimensions and that may encompass devices ranging from tens or hundreds of nanometers across to tens or hundreds of meters across (or larger) that employ various types of components all the way down to the nanoscale, including individual nanobots - but with the larger components built by or from or incorporating the smaller devices. I'm not sure how Rynn would define it, but perhaps he'll weigh in.

Todd

[radtech497]

Just as a historical aside, here is a transcript of Richard Feynman's 1959 lecture, "There's Plenty of Room at the Bottom."