In-Space Manufacturing of Self-Replicating Machines

How do we get to a future of self-replicating, Von Neumann space probes? What are some of the steps required to convert the Asteroid Belt into a partial Dyson Sphere?

The answer lies in ISAM or in-space servicing assembly and manufacturing, 3D printing on-orbit, and fully automated, ‘lights-out’ production on-Earth. Making it on the Moon. Let’s do it. But, with what and how?

3D Printing a new atmospheric entry vehicle above a new planet is cool. Repairing a reusable re-entry vehicle above Earth is essential.

Ordinate systems, or number lines, form the basis of all additive manufacturing. Unfortunately, these numerologies are trapped within the traditional manufacturing system. The number line ends at the border of the 3D printer box. And the parts that they produce are attached to one another in the real world, not the digital world. If the number lines for every manufacturing system were shared between the 3D printers and the welders, then new horizons would be unlocked. Each sequential manufacturing process should place its co-ordinates along the ordinate lines of the super-structure that is being produced. If we are to produce a kilo-meter scale structure on-orbit, don’t you think we need a single map to guide us? It is difficult to imagine new technology without a continuous digital workspace. But that is how we do things today.

Sensors Across Length Scales

One of the reasons that we have inherited a fractured digital workspace is because of the history of ideas; the history of aerospace blueprinting. Those of us from the digital age eschew the paper world for cyberspace. Vision: the ability to see beyond the horizon. Any sufficiently enhanced digital technology should allow for us to see into the next adjacent digital technology without break. The smaller, more precise, components will be 3D printed inside of Endo-Robotics; the assembly of parts larger than the Endo-Printer will be welded together with Exo-Robotics, the assemblies will be joined together with Construction-Robotics. But can one eye see through all of these fabrication environments without break? Do we have a sensor package upon which to lay our number lines? That is essential. Robotics systems are inherently limited by reach. The motion platforms’ reach should not determine the interoperability of manufacturing processes.

Industrial robots in-space enable numerical scale-up of ISAM systems to the thousands. Around 440,000 industrial robots are delivered to Earth factories per year. Less than one space robot is launched per year.

Kung Fu is robotic motion — continuous.

Carbon Fiber

Enter continuous carbon fiber. The Bruce Lee of materials. Nothing is stronger. Nothing is more direct. Using Carbon Fibers to fluidly manufacture, assemble, and construct is good Feng Shui. In-Space manufacturing calls for fluid, continuously rotated, motions and additive manufacturing of continuous fibers across all robotic contexts. Internal, external, and construction robotics are at the greatest potential if they all share the same tools, materials, and digital domain.

Wire Harnesses

Re-Enter the Dragon; Excite the wires. Embody the intent. There are well over 100 successful metal printing companies. But none of them are printing wire harnesses into/ onto the vehicles. Why not? Because that would require that the whole airframe and its manufacturing processes are digitized and available to a control network and multiple manufacturing processes. This is challenging. Automated fiber placement seems like it should work, but it does not.

Primarily for two reasons: Lack of tow steering; so surface conformal pathing/motion with arbitrary steering is impossible; and, the lack of a continuous digital environment that integrates with multiple manufacturing processes blocks the control computer from understanding the whole vehicle.

Also, you could anticipate that error detection and automated correction is complex and essential. So Orbital Composites has spent years to create a contiguous digital environment and scaleable real-time control network to “Enter the Dragon” — to bring your spacecraft to life as one part — wires and all.

End-Of-Life, Recycleable Materials, Un-Printing

The end-of-life for orbital assets also needs to be accounted for. Dumping things down into the atmosphere, or parking dead-things into the ‘graveyard’ is irresponsible. A 200-million-dollar satellite is still an asset even if it lacks fuel. ISAM allows for these ‘dead birds’ to rise again. Re-fueling is movement without regret.

One primary challenge today is the variety of materials. Coatings make re-usable materials, like Aluminum, un-recyclable. We must plan to take things out of service and then rip them apart and allow for the re-manufacture of new satellites. Any responsible aerospace material scientist must advocate for this.

Reversible chemistries and open-ended physical process manufacturing methods allow for recycling. It would be great if we could run the execution code of our 3D printer in reverse and un-print our parts. Continuous fibers should make this easy, right? Can you imagine the power of being able to unravel a satellite onto the spools its fibers and wires were rolled off of?

Wires and fibers make this future more possible than thermoplastics alone. Neat thermoplastics and neat metals, non-composites, must be ground up for in-space recycling. Theoretically, one could scrape thermoplastics off of pre-manufactured parts, but it would be exceedingly difficult to make consistent, printable feedstocks that way.

Realtime Control Networking

Definition of real-time. As soon as possible (ASAP) control is not real-time control. Real-time network controllers deliver commands exactly when they are expected. You could think ASAP should work fine. But let us illustrate the problem. Imagine you have three explosive bolts that separate a rocket stage. The three explosive bolts have slightly different lengths of wire going back to their shared controller. A single, “Go Boom” command may arrive at slightly different times to the bolts. This would imbalance stage separation. A real-time controller would update the system-time at the bolts’ individual computers and tell them what time to “Go Boom.” This real-time control aspect will ensure that the rocket separates axially.

Real-time robotic control networking is a more difficult problem. If, for example, multiple robots are attempting to 3D print onto the same part but with overlapping motion spaces, then they must be in the right space-time in order to avoid collisions. Even deeper still, the motors that move plastic and fibers through the additive manufacturing system must also keep space-time with the robotic motions. Essentially, the real-time control network orchestrates the synchronicity of additive manufacturing with multiple robots.

ISRU of Feedstocks and Asteroid Mining

In-Situ Resource Utilization (ISRU) of carbonaceous, silicaceous, and metallic asteroids will be the feedstocks of the future. Pitch-based carbon fibers can be directly extruded from carbon dust. Microwaved and extruded regolith turns into fiberglass. And metallic asteroids can be directly ground up and extruded to form wires. With some advanced chemistry tricks, the polymers that we need can be synthesized from asteroids containing carbon and organic compounds.

Small metallic objects such as valves and batteries would need to be created. Metal foils and polymers can be used to create batteries.

Primary Structure, Pressure Vessels, Aerodynamics, Radomes, Wire Harnesses

How many different kinds of materials are required to form an additive basis for self-replication? We believe that there is more than one combination of elements that allows for this future. We can imagine that leading edge materials such as carbon fiber would be essential to make advanced vehicles. A polymer to bind those fibers together will also be required. Conductors and dielectrics would come next: wires and polymers. Radio transparent fibers must also be included. So, fiberglass. Most of a high-performance vehicle can be produced with these elements: carbon fibers, fiberglass, wires, and polymer. Leaving the fuel aside for one minute, ice, these elements could create as much as 80 percent of the vehicle. If we could freely place these continuous fibers conformally onto an arbitrary surface, then the technology for self-replication will be hugely complete.

Power Electronics, LEDs, CPUs, Optics, Rocket Nozzles, and Nuclear Reactor Components

High-performance materials are needed for harsh environments. Environments such as rocket plumes and nuclear reactors call out for Continuous Carbon Fibers with Carbon or Silicon Carbide matrixes. We call these materials C/C or C/SiC. In-space manufacturing of C/C and C/SiC will require lots of heat. But, in-space manufacturing also opens the horizon the larger-than-ever structures: such as a monolithic re-entry shielded vehicle without tiles. Finding a furnace on orbit is going to be tough. But creating an ever-growing solar concentrator is one way to collect the immense amount of thermal energy required to sinter/ melt metals and activate the Carbon and Silicon ceramic chemistries.

The optical mirrors on James Webb Space Telescope are made from SiC. Once a critical mass of mirrors are assembled on-orbit, melting siliceous asteroids will form a feedback loop of progressive scale-up and division of solar concentrators. The self-replication of Von Neumann’s space probe will be close at hand. It should be pointed out that on-Earth SiC chip foundries operate on the Mega and Giga Watt scales. The International Space Station by contrast is kept to the Kilo Watt scale. Power electronics, LEDs, CPUs, optics, rocket nozzles, and nuclear reactor components are all readily made from SiC. Mastering the in-space production of SiC is a huge leap forward for mankind’s technology of the Dyson Sphere. Melt the Belt!

This article was written by Cole Nielsen-Cole, Founder and CTO, Orbital Composites (Campbell, CA). For more information, visit here  .

---