Early probes are one thing, but can we build a continuing presence among the stars, human or robotic? An evolutionary treatment of starflight sees it growing from a steadily expanding presence right here in our Solar System, the kind of infrastructure Alex Tolley examines in the essay below. How we get to a system-wide infrastructure is the challenge, one analyzed by a paper that sees artificial intelligence and 3D printing as key drivers leading to a rapidly expanding space economy. The subject is a natural for Tolley, who is co-author (with Brian McConnell) of A Design for a Reusable Water-Based Spacecraft Known as the Spacecoach (Springer, 2016). An ingenious solution to cheap transportation among the planets, the Spacecoach could readily be part of the equation as we bring assets available off-planet into our economy and deploy them for even deeper explorations. Alex is a lecturer in biology at the University of California, and has been a Centauri Dreams regular for as long as I can remember, one whose insights are often a touchstone for my own thinking.

by Alex Tolley


Crewed starflight is going to be expensive, really expensive. All the various proposed methods from slow world ships to faster fusion vessels require huge resources to build and fuel. Even at Apollo levels of funding in the 1960’s, an economy growing at a fast clip of 3% per year is estimated to need about half a millennium of sustained growth to afford the first flights to the stars. It is unlikely that planet Earth can sustain such a sizable economy that is millions of times larger than today’s. The energy use alone would be impossible to manage. The implication is that such a large economy will likely be solar system wide, exploiting the material and energy resources of the system with extensive industrialization.

Economies grow by both productivity improvements and population increases. We are fairly confident that Earth is likely nearing its carrying capacity and certainly cannot increase its population even 10-fold. This implies that such a solar system wide economy will need huge human populations living in space. The vision has been illustrated by countless SciFi stories and perhaps popularized by Gerry O’Neill who suggested that space colonies were the natural home of a space faring species. John Lewis showed that the solar system has immense resources to exploit that could sustain human populations in the trillions.


Image credit: John Frassanito & Associates

But now we run into a problem. Even with the most optimistic estimates of reduced launch costs, and assuming people want to go and live off planet probably permanently, the difficulties and resources needed to develop this economy will make the US colonization by Europeans seem like a walk in the park by comparison. No doubt it can be done, but our industrial civilization is little more than a quarter of a millennium old. Can we sustain the sort of growth we have had on Earth for another 500 years, especially when it means leaving behind our home world to achieve it? Does this mean that our hopes of vastly larger economies, richer lives for our descendents and an interstellar future for humans is just a pipe dream, or at best a slow grind that might get us there if we are lucky?

Well, there may be another path to that future. Philip Metzger and colleagues have suggested that such a large economy can be developed. More extraordinary, that such an economy can be built quickly and without huge Earth spending, starting and quickly ending with very modest space launched resources. Their suggestion is that the technologies of AI and 3D printing will drive a robotic economy that will bootstrap itself quickly to industrialize the solar system. Quickly means that in a few decades, the total mass of space industrial assets will be in the millions of tonnes and expanding at rates far in excess of our Earth-based economies.

The authors ask, can we solve the launch cost problem by using mostly self-replicating machines instead? This should remind you of the von Neumann replicating probe concept. Their idea is to launch seed factories of almost self-replicating robots to the Moon. The initial payload is a mere 8 tonnes. The robots will not need to be fully autonomous at this stage as they can be teleoperated from Earth due to the short 2.5 second communication delay. They are not fully self-replicating at this stage as need for microelectronics is best met with shipments from Earth. Almost complete self-replication has already been demonstrated with fabs, and 3D printing promises to extend the power of this approach.

The authors assume that initial replication will neither be fully complete, nor high fidelity. They foresee the need for Earth to ship the microelectronics to the Moon as the task of building fabs is too difficult. In addition, the materials for new robots will be much cruder than the technology earth can currently deliver, so that the next few generations of robots and machinery will be of poorer technology than the initial generation. However the quality of replication will improve with each generation and by generation 4, a mere 8 years after starting, the robot technology will be at the initial level of quality, and the industrial base on the Moon should be large enough to support microelectronics fabs. From then on, replication closure is complete and Earth need ship no further resources to the Moon.

GenHuman/Robotic InteractionArtificial IntelligenceScale of IndustryMaterials ManufacturedSource of Electronics
1.0Teleoperated and/or locally operated by a human outpostInsect-likeImported, small-scale, limited diversityGases, water, crude alloys, ceramics, solar cellsImport fully integrated machines
2.0TeleoperatedLizard-likeCrude fabrication, inefficient, but greater throughput than 1.0(Same)Import electronics boxes
2.5TeleoperatedLizard-likeDiversifying processes, especially volatiles and metalsPlastics, rubbers, some chemicalsFabricate crude components plus import electronics boxes
3.0Teleoperated with experiments in autonomyLizard-likeLarger, more complex processing plantsDiversify chemicals, simple fabrics, eventually polymersLocally build PC cards, chassis and simple components, but import the chips
4.0Closely supervised autonomyMouse-likeLarge plants for chemicals, fabrics, metalsSandwiched and other advanced material processesBuilding larger assets such as lithography machines
5.0Loosely supervised autonomyMouse-likeLabs and factories for electronics and robotics. Shipyards to support main belt.Large scale productionMake chips locally. Make bots in situ for export to asteroid belt.
6.0Nearly full autonomyMonkey-likeLarge-scale, self-supporting industry, exporting industry to asteroid main beltMakes all necessary materials, increasing sophisticationMakes everything locally, increasing sophistication
X.0Autonomous robotics pervasive throughout Solar System enabling human presenceHuman-likeRobust exports/imports through zones of solar systemMaterial factories specialized by zone of the Solar SystemElectronics factories in various locations

Table 1. The development path for robotic space industrialization. The type of robots and the products created are shown. Each generation takes about 2 years to complete. Within a decade, chip fabrication is initiated. By generation 6, full autonomy is achieved.

AssetQty. per setMass minus Electronics (kg)Mass of Electronics (kg)Power (kW)Feedstock Input (kg'hr)Product Output (kg/hr)
Power Distrib & Backup12000-----------------
Excavators (swarming)570190.3020----
Chem Plant 1 - Gases1733305.5841.8
Chem Plant 2 - Solids1733305.58101.0
Metals Refinery110191910.00203.15
Solar Cell Manufacturer1169190.500.3----
3D Printer 1 - Small Parts4169195.000.50.5
3D Printer 2 - Large Parts4300195.000.50.5
Robonaut assemblers3135150.40--------
Total per Set~7.7 MT
launched to Moon
64.36 kW20 kg
4 kg

Table 2. The products and resources needed to bootstrap the industrialization of the Moon with robots. Note the low mass needed to start, a capability already achievable with existing technology. For context, the Apollo Lunar Module had a gross mass of over 15 tonnes on landing.

The authors test their basic model with a number of assumptions. However the conclusions seem robust. Assets double every year, more than an order of magnitude faster than Earth economic growth.


Figure 13 of the Metzger paper shows that within 6 generations, about 12 years, the industrial base off planet could potentially be pushing towards 100K MT.


Figure 14 of the paper shows that with various scenarios for robots, the needed launch masses from Earth every 2 years is far less than 100 tonnes and possibly below 10 tonnes. This is quite low and well within the launch capabilities of either government or private industry.

Once robots become sophisticated enough, with sufficient AI and full self-replication, they can leave the Moon and start industrializing the asteroid belt. This could happen a decade after initiation of the project.

With the huge resources that we know to exist, robot industrialization would rapidly, within decades not centuries, create more manufactures by many orders of magnitude than Earth has. Putting this growth in context, after just 50 years of such growth, the assets in space would require 1% of the mass of the asteroid belt, with complete use within the following decade. Most importantly, those manufactures, outside of Earth’s gravity well, require no further costly launches to transmute into useful products in space. O’Neill colonies popped out like automobiles? Trivial. The authors suggest that one piece could be the manufacture of solar power satellites able to supply Earth with cheap, non-polluting power, in quantities suitable for environmental remediation and achieving a high standard of living for Earth’s population.

With such growth, seed factories travel to the stars and continue their operation there, just as von Neumann would predict with his self-replicating probes. Following behind will be humans in starships, with habitats already prepared by their robot emissaries. All this within a century, possibly within the lifetime of a Centauri Dreams reader today.

Is it viable? The authors believe the technology is available today. The use of telerobotics staves off autonomous robots for a decade. In the 4 years since the article was written, AI research has shown remarkable capabilities that might well increase the viability of this aspect of the project. It will certainly need to be ready once the robots leave the Moon to start extracting resources in the asteroid belt and beyond.

The vision of machines doing the work is probably comfortable. It is the fast exponential growth that is perhaps new. From a small factory launched from Earth, we end up with robots exploiting resources that dwarf the current human economy within a lifetime of the reader.

The logic of the model implies something the authors do not explore. Large human populations in space to use the industrial output of the robots in situ will need to be launched from Earth initially. This will remain expensive unless we are envisaging the birthing of humans in space, much as conceived for some approaches to colonizing the stars. Alternatively an emigrant population will need to be highly reproductive to fill the cities the robots have built. How long will that take? Probably far longer, centuries, rather than the decades of robotic expansion.

Another issue is that the authors envisage the robots migrating to the stars and continuing their industrialization there. Will humans have the technology to follow, and if so, will they continue to fall behind the rate at which robots expand? Will the local star systems be full of machines, industriously creating manufactures with only themselves to use them? And what of the development of AI towards AGI, or Artificial General Intelligence? Will that mean that our robots become the inevitable dominant form of agency in the galaxy?

The paper is Metzger, Muscatello, Mueller & Mantovani, “Affordable, Rapid Bootstrapping of the Space Industry and Solar System Civilization,” Journal of Aerospace Engineering Volume 26 Issue 1 (January 2013). Abstract / Preprint.