Wow, I think that comment is as long as my original essay. Lots of good points. Let me take them one by one.
I see a few potential benefits to efficiency-imparing simplifications:
lt reduces the size/cost/complexity of the initial self-replicating system. (I think this motivation is misplaced, and we should be shooting for a much larger initial size than 1 meter cubed.)
The real motivation for the efficiency-impairing simplifications is none of size, cost or complexity. It is to reduce replication time. We need an Autofac efficient enough that what it produces is higher value than what it consumes. We don’t want to reproduce Soviet industry, much of which processed expensive resources into lousy products worth less than the inputs. Having achieved this minimum, however, the goal is to allow the shortest possible time of replication. This allows for the most rapid production of the millions of tons of machinery needed to produce massive effects.
Consider that the Autofac, 50 kg in a 1 m^3, is modeled on a regular machine shop, with the machinist replaced by a robot. The machine shop is 6250 kg in 125 m^3. I just scale it down by a factor of 5, and thereby reduce the duplication time by a factor of 5. So it duplicates in 5 weeks instead of 25 weeks. Suppose we start the Autofac versus the robot machine shop at the same time. After a year, there are 1000 Autofacs versus 4 machine shops; or in terms of mass, 50,000 kg of Autofac and 25,000 kg of machine shop. After two years, 50,000,000 kg of Autofac versus 100,000 kg of machine shop. After 3 years, it’s even more extreme. At any time, we can turn the Autofacs from making themselves to making what we need, or to making the tools to make what we need. The Autofac wins by orders of magnitude even if it’s teeny and inefficient, because of sheer speed.
That’s why I picked a one meter cube. I would have picked a smaller cube, that reproduced faster, but that would scale various production processes beyond reasonable limits. I didn’t want to venture beyond ordinary machining into weird techniques only watchmakers use.
I see a few potential benefits to efficiency-imparing simplifications:
...
It reduces the engineering effort needed to design the initial self-replicating system.
This is certainly a consideration. Given the phenomenal reproductive capacity of the Autofac, there’s an enormous return to finishing design as quickly as possible and getting something out there.
To me, it seems that the Autofac dream comes from a particular context—mid-20th-century visions of space exploration—that have unduly influenced Feynman’s current concept.
Let me tell you some personal history. I happened upon the concept of self-reproducing machines as a child or teenager, in an old Scientific American from the fifties. This was in the 1970s. That article suggested building a self-reproducing factory boat, that would extract resources from the sea, and soon fill up the oceans and pile up on beaches. It wasn’t a very serious article. Then I went to MIT, in 1979. Self-reproducing machines were in the air—Eric Drexler was theorizing about mechanical bacteria, and NASA was paying people to think about what eventually became the 1981 lunar factory design study. I thought that sending a self-reproducing factory to the asteroid belt was the obvious right thing, and thought about it, in my baby-engineer fantasy way. But I could tell I was ahead of my time, so I turned my attention to supercomputers and robots and AI and other stuff for a few decades.
A few years ago I picked up the idea of self-reproducing boats again. I imagined a windmill on deck for power, and condensing Seacrete and magnesium from the water for materials. There was a machine shop below decks, building all the parts. But I couldn’t make the energy economy work out, even given the endless gales of the Southern Ocean. So I asked myself, what about just the machine shop part? Then I realized the reproduction time was the overriding consideration. How can I figure out the reproduction time? Well, I could estimate the time to do it with a regular human machine shop, and I remembered Eric Drexler’s scaling laws. And wow, five weeks?! That’s short enough to be a really big deal! So, a certain amount of calculation and spreadsheets later, here we are, the Autofac.
I considered varied environments for situating the Autofac:
a laboratory in Boston. Good for development, but doesn’t allow rapid growth.
a field near a railroad and power line in the Midwest. Good for the resource inputs, but the neighbors might reasonably complain when the steel mill starts belching flame, or the Autofacs pile up sky-high.
Baffin Island. Advantages described above.
Antarctic Icecap. Bigger than Baffin, but useful activities are illegal. Shortage of all elements except carbon, oxygen, nitrogen and hydrogen.
The Moon. Even bigger. Ironically, shortage of carbon, nitrogen and hydrogen. No wind, so the Autofac has to include solar cell manufacture from the git-go. There will be lots of problems understanding vacuum manufacturing. Obvious first step toward Dyson Sphere.
Carbonaceous asteroids. Obvious second step toward Dyson Sphere.
So, I decided to propose an intermediate environment. Obviously, it was rooted in the mid-20th-century visions of space exploration. But that didn’t set the size, or the use of Baffin Island, or anything else really. We’ll build a Dyson Sphere eventually, but I don’t feel the need to do it personally.
Wow, I think that comment is as long as my original essay. Lots of good points. Let me take them one by one.
The real motivation for the efficiency-impairing simplifications is none of size, cost or complexity. It is to reduce replication time. We need an Autofac efficient enough that what it produces is higher value than what it consumes. We don’t want to reproduce Soviet industry, much of which processed expensive resources into lousy products worth less than the inputs. Having achieved this minimum, however, the goal is to allow the shortest possible time of replication. This allows for the most rapid production of the millions of tons of machinery needed to produce massive effects.
Consider that the Autofac, 50 kg in a 1 m^3, is modeled on a regular machine shop, with the machinist replaced by a robot. The machine shop is 6250 kg in 125 m^3. I just scale it down by a factor of 5, and thereby reduce the duplication time by a factor of 5. So it duplicates in 5 weeks instead of 25 weeks. Suppose we start the Autofac versus the robot machine shop at the same time. After a year, there are 1000 Autofacs versus 4 machine shops; or in terms of mass, 50,000 kg of Autofac and 25,000 kg of machine shop. After two years, 50,000,000 kg of Autofac versus 100,000 kg of machine shop. After 3 years, it’s even more extreme. At any time, we can turn the Autofacs from making themselves to making what we need, or to making the tools to make what we need. The Autofac wins by orders of magnitude even if it’s teeny and inefficient, because of sheer speed.
That’s why I picked a one meter cube. I would have picked a smaller cube, that reproduced faster, but that would scale various production processes beyond reasonable limits. I didn’t want to venture beyond ordinary machining into weird techniques only watchmakers use.
This is certainly a consideration. Given the phenomenal reproductive capacity of the Autofac, there’s an enormous return to finishing design as quickly as possible and getting something out there.
Let me tell you some personal history. I happened upon the concept of self-reproducing machines as a child or teenager, in an old Scientific American from the fifties. This was in the 1970s. That article suggested building a self-reproducing factory boat, that would extract resources from the sea, and soon fill up the oceans and pile up on beaches. It wasn’t a very serious article. Then I went to MIT, in 1979. Self-reproducing machines were in the air—Eric Drexler was theorizing about mechanical bacteria, and NASA was paying people to think about what eventually became the 1981 lunar factory design study. I thought that sending a self-reproducing factory to the asteroid belt was the obvious right thing, and thought about it, in my baby-engineer fantasy way. But I could tell I was ahead of my time, so I turned my attention to supercomputers and robots and AI and other stuff for a few decades.
A few years ago I picked up the idea of self-reproducing boats again. I imagined a windmill on deck for power, and condensing Seacrete and magnesium from the water for materials. There was a machine shop below decks, building all the parts. But I couldn’t make the energy economy work out, even given the endless gales of the Southern Ocean. So I asked myself, what about just the machine shop part? Then I realized the reproduction time was the overriding consideration. How can I figure out the reproduction time? Well, I could estimate the time to do it with a regular human machine shop, and I remembered Eric Drexler’s scaling laws. And wow, five weeks?! That’s short enough to be a really big deal! So, a certain amount of calculation and spreadsheets later, here we are, the Autofac.
I considered varied environments for situating the Autofac:
a laboratory in Boston. Good for development, but doesn’t allow rapid growth.
a field near a railroad and power line in the Midwest. Good for the resource inputs, but the neighbors might reasonably complain when the steel mill starts belching flame, or the Autofacs pile up sky-high.
Baffin Island. Advantages described above.
Antarctic Icecap. Bigger than Baffin, but useful activities are illegal. Shortage of all elements except carbon, oxygen, nitrogen and hydrogen.
The Moon. Even bigger. Ironically, shortage of carbon, nitrogen and hydrogen. No wind, so the Autofac has to include solar cell manufacture from the git-go. There will be lots of problems understanding vacuum manufacturing. Obvious first step toward Dyson Sphere.
Carbonaceous asteroids. Obvious second step toward Dyson Sphere.
So, I decided to propose an intermediate environment. Obviously, it was rooted in the mid-20th-century visions of space exploration. But that didn’t set the size, or the use of Baffin Island, or anything else really. We’ll build a Dyson Sphere eventually, but I don’t feel the need to do it personally.
More to come.