Fast Takeoff: Errors, part 2

A comment by Todd Andersen got me thinking about the variety of factors that affect error rate in a molecular manufacturing system.

Todd is right that error checking of finished sub-blocks may be a way to reduce error rates. Whether this works depends on the details of the process. In some processes, it may be relatively easy to build a 100 atom part (of which maybe 98% will be perfect), then test and throw out the 2%, then stick the perfect parts together to make a perfect meta-part.

In other processes, an error will not only destroy the workpiece, but also the tool. So if a 10,000-atom tool is destroyed by each error, then the success rate needs to be 99.99% or better.

In a multi-stage process, each stage may have a different error rate for a different reason, and need different error handling. (Note that, unlike in chemistry, many kinds of errors can be corrected, reducing the eventual error rate.)

Tools that can only be built by molecular manufacturing may reduce the error rate drastically. For example, sorting rotor cascades can give you any purity you need, and atomically perfect sliding seals can exclude all contaminants. In that case, it may be a quick step from just barely good enough, to so good you don't even have to think about it.

A more general argument is that once you have general-purpose molecular manufacturing, you can probably build improved versions of your tools right away. So... although I can't prove that any given molecular manufacturing pathway will have a fast takeoff thanks to error rates crossing a threshold of significance, it does seem pretty likely.

This follows a general trend of argument: the difference between unfeasible and adequate is generally bigger than the difference between adequate and excellent. Feed "excellent" into an exponential growth equation, and you get a fast takeoff.

In future posts in this series, I'll be following this trend of argument in other areas, including range of machinery that can be built, size of design space that's accessible, and fabrication speed.

Chris Phoenix

Comments

[Tom Craver]

Chris -

What would you consider "fast" for take-off?

I would agree that once we get to the point of self-copying molecular manufacturing technology, the global roll-out could be quite rapid, if not restricted.

But I suspect there'll be a rather long interval - probably several years at least -in which it'll be widely recognized that we have the ability to make a wide range of atomically precise "nano-machine parts", but have not yet been able to produce a reasonably efficient self-copying system.

That would be a critical period.

E.g. nanotech arms races might be triggered, in which all work on molecular manufacturing is "classified", as multiple nations compete to be first.

Traditional manufacturers would be aware and afraid of the impact - perhaps lobbying government to place licensing and other restrictions that will allow them to retain advantages.

Social movements might spring up in anticipation - post-capitalists, neo-socialists, darwinian survivalists, etc.

[Chris Phoenix]

Anything less than 5 years would be fast. I think it could actually be less than 2.

As to "widely recognized" - Aono was pick-and-placing silicon atoms in 1994. We've had Schafmeister polymers and Rothemund staples and Seeman's DNA-building-DNA machines for years now.

We may already be in the critical period of classified arms races. But it's certainly not widely recognized that MM is near. Even Drexler is saying it's too early for diamondoid work. (Not that MM is the same as diamondoid, but I'd expect MM to bootstrap to diamondoid pretty quickly.)

Chris

[Tom Craver]

Sure, we've had limited atom moving and bonding ability for some time - but nothing that seemed to enable building a wide variety of component parts that could be assembled into a larger device. That, I think, is going to be the trigger on the starting gun.