October 24, 2011
Replicators Have Arrived
The north pole of the Moon: Real or facsimile?
Of all the wonders depicted in science fiction books and movies, one of the most intriguing is the machine that makes anything that you need or desire. Merely enter a detailed plan, or push the button for items programmed into the machine – dials twirl, the machine hums and out pops what you requested. Technology gives us Aladdin’s Lamp. A handy device that will find many uses.
We’re not quite there yet but crude versions of such imagined machines already exist. These machines are called “rapid prototype” generators or three-dimensional printers. They take digitized information about the dimensions and shape of an object and use that data to control a fabricator that re-creates the object using a variety of different materials. Typically, these machines use easy to mold plastics and epoxy resins but in principle, any material could be used to create virtually any object.
What’s the relevance of this technology to spaceflight and to the Moon? One of the key objects of lunar return is to learn how to use the material and energy resources of the Moon to create new capabilities. To date, we have focused our attention on simple raw materials like bulk regolith (soil) and the water found at the poles. It makes sense to initially limit our resource utilization ambitions to simple materials that are both useful and relatively massive, which currently have those killer transportation costs when delivered from Earth. Bulk regolith has many different uses, such as shielding (e.g., rocket exhaust blast berms) as well as raw material for simple surface structures.
However, once we are on the Moon and have met the basic necessities of life, we can begin to experiment with making and using more complex products. In effect, the inhabitants of the Moon will begin to create more complicated parts and items from what they find around them, just outside their door. The techniques of three-dimensional printing will allow us to discover what makes life off-planet easier and more productive. We will experiment by using the local materials to maintain and repair equipment, build new structures, and finally begin off-planet manufacturing.
During the early stages of lunar habitation, material and equipment will be brought from Earth. With continued use, particularly in the harsh lunar surface environment, breakdowns will occur. Although initially we will use spare parts from Earth, for simple uncomplicated structures that are needed quickly, a three-dimensional printer can make substitute parts using local resource materials found near the outpost. Most existing 3-D printers on Earth use plastics and related materials (which are complex carbon-based compounds, mostly derived from petroleum) but some processing has used concrete, which can be made on the Moon from sieved regolith and water. In addition, we also know that regolith can be fused into ceramic using microwaves, so rapid prototyping activities on the Moon may eventually find that partially melting particulate matter into glass is another way to create useful objects.
The lunar surface is a good source of material and energy useful in creating a wide variety of objects. I mentioned simple ceramics and aggregates, but additionally, a variety of metals (including iron, aluminum and titanium) are available on the Moon. Silicon for making electronic components and solar cells is abundant on the Moon. Designs for robotic rovers that literally fuse the in-place upper surface of the lunar regolith into electricity-producing solar cells have already been imagined and prototyped. We can outsource solar energy jobs to the Moon!
These technical developments lead to mind-boggling possibilities. Back in the 1940s, the mathematician John von Neumann imagined what he called “self-replicating automata,” small machines that could process information to reproduce themselves at exponential rates. Interestingly, von Neumann himself thought of the idea of using such automata in space, where both energy and materials are (quite literally) unlimited. A machine that contains the information and the ability to reproduce itself may ultimately be the tool humanity needs to “conquer” space. Hordes of reproducing robots could prepare a planet for colonization as well as providing safe havens and habitats.
We can experiment on the Moon with self-replicating machines because it contains the necessary material and energy resources. Of course, in the near-term, we will simply use this new technology to create spare parts and perhaps simple objects that we find serve our immediate and utilitarian needs. But things like this have a habit of evolving far beyond their initial envisioned use, and often in directions that we do not expect; we are not smart enough to imagine what we don’t know. The technology of three-dimensional printing will make the habitation of the Moon – our nearest neighbor in space – easier and more productive. Even now, creative former NASA workers have found a way to make this technology pay off. In the future, perhaps their talents could be applied to making the Moon a second home to humanity.
Note: The image at the beginning of this post is a model of the lunar north pole, made using a three-dimensional printer and LRO laser altimetry data by Howard Fink of New York University. The scale of the model is about 30 cm across.
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Very nice article. I agree. Any reason you did not use the term “bootstrap”?
Comment by Ron Menich — October 24, 2011 @ 3:11 pm
Ron,
Many thanks.
Any reason you did not use the term “bootstrap”?
No.
Comment by Paul D. Spudis — October 24, 2011 @ 3:30 pm
I think its worth mentioning that the 3d printing technology is not just for high tech endeavors, its affordable for DIY’s hobbyists, and the quality and variety of the builds they make is rapidly increasing.
See http://reprap.org and http://blog.reprap.org/
Anyone can have an open source hw/sw 3d printer on their desk for $500-$2000, or even far less if they have the building skills
Comment by kert — October 24, 2011 @ 5:03 pm
Just like most “science fiction”, there is real science behind self-replicating machines – but it’s a big leap to get to even one completely self-replicating machine working here on Earth, much less an airless moon with 1/6 gravity.
I put this kind of stuff in the same category as fusion power, in that I’ll wait to celebrate until it happens. Until then we should be keeping our feet planted in the capabilities of today, and figuring out how we can move out into space while on limited budgets.
Comment by Coastal Ron — October 24, 2011 @ 5:29 pm
but it’s a big leap to get to even one completely self-replicating machine working here on Earth,
And nobody needs completely self-replicating.
Duh.
Especially for a lunar application, if you can manufacture a 90% of mass of the machine itself, you have just made possible to land 10x more useful mass on the site in your mission architecture.
Completely self-replicating machines is a red herring, as is a completely closed life support system, or a completely self-sustaining off-earth colony.
RepRap can already manufacture what .. 50% ( random guess ) of its own mass in parts ? And its not even optimized for weight.
Comment by kert — October 24, 2011 @ 9:59 pm
[...] Replicators Have Arrived | The Once and Future Moon [...]
Pingback by Replicators Have Arrived | The Once and Future Moon | New Space: A New Era In Space Exploration | Scoop.it — October 24, 2011 @ 10:59 pm
Interesting article.
I actually had occasion to see some examples of a rudimentary stage of this technology going back to the early 1990’s. We were working on neutral buoyancy/micro-gravity aircraft testing to verify ISS Assembly/Maintenance techniques. One of the designers came in with some fairly complex representations of Quick Disconnects made of a wax like substance. We could not use them in the testing at the time because they were two fragile. But the detailing was impressive.
If the technology has advanced to the point where metals (etc.) can be used, it would indeed be (to put it mildly) highly useful. I would think one of the first things that would be desired to manufacture would be tankage for lunar propellants (high volume and mass – and thus expensive to launch). Anybody know if manufacturing articles that large would be practical?
Comment by Joe — October 25, 2011 @ 9:42 am
Anybody know if manufacturing articles that large would be practical?
With some intelligence in your design, you can build items as large as you wish with current printers, assuming your mechanical design is composed of several parts.
A set of 3d printers are best complemented by an assembly robot with a few tools and a welder, which is a very mature technology.
In fact if you look around in thingiverse ( the open source repository for solid models used in these printers ) you can find some emerging new mechanical design patterns there in parts that are specifically optimized for the printing process.
Comment by kert — October 25, 2011 @ 3:41 pm
Comment by kert — October 25, 2011 @ 3:41 pm
Thanks
There are still a number of detailed questions to be answered:
- Are there resources in the Lunar Materials available to make insulated tankage for cryogenic propellants (for use both for depots and tanks for vehicles)?
- Can the 3D printing system handle combining different types of materials?
- Etc.
Never the less a good start.
Comment by Joe — October 25, 2011 @ 4:50 pm
Replacators are a bad idea , any one who has watched stargate sg1 knows that , they will get out of control and self replicate till all of a planets resources are used up !
Comment by Frontrowsentiant — October 25, 2011 @ 6:34 pm
Actually, a RepRap can print everything for itself except guiderails, motors, wire, printing nozzles and circuit boards. Say 70%
And don’t get distracted by “3D printers”.
You want to look up Direct Laser deposition.
Basically just take a starter stick, dig it into the surface to attach some dust, and use laser to sinter the sections you want. The biggest hurdle here on earth is the size of the vacuum chamber.
The coolest application is that you don’t even have to make fuel tanks for your printed rockets. just print out a platform with some tie downs on it, and take some pre-made steel tanks w/nozzles, and sinter them right into the body of the rocket platform. Add an igniter, and hook up some wire to the nozzles to steer em (or not) and pack em full of moon dirt and some ice. It has enough oxy,mag,and aluminum to launch itself, plus 40% extra fuel for restocking orbital, and relanding.
http://www.sciencedaily.com/releases/2009/10/
091007161127.htm
look up aluminum moon rockets think in the Moon Miners Manifesto for isp info. College group is launching a 6 footer already. Regolith is already mixed at correct values, might want to drag a magnet thru it to remove iron.
You have to bring wire, iphones and optics for Nav,comm eqpt. and the engine bells, but everything else you can manufacture on-site with regolith.
Would be great to have a printer up there building structural beams, rover and truck parts, water tanks, etc. while we plan and develop habitat and provision designs.
http://www.eurekalert.org/pub_releases/2009-01/ps-sfn012209.php
for water, darktime energy and attitude jets.
Comment by morganism — October 25, 2011 @ 8:54 pm
Comment by kert — October 24, 2011 @ 9:59 pm
“RepRap can already manufacture what .. 50% ( random guess ) of its own mass in parts?”
Thanks for the example.
I’m not sure if mass is the prime concern here. If you look around a pressurized laboratory like the ISS, or even an arctic remote outpost, the components that are the most vital are either extruded at high temperatures (sheet & rod aluminum, sheet plastic, extruded metal beams & wire) or molded under pressure. My early career years were spent in a machine shop environment using & making extruded parts, which is why I bring this up.
I know we’re looking down the road here, and I guess my point is that I don’t know if self-replicating machinery can fulfill that role for that type of material. We use such specialized machinery today, and the lunar environment is going to require the highest performing materials we can afford to make, and I don’t think that can be outsourced.
Out of curiosity, have they been able to make 3D parts that can be sintered? That at least would get you things like bearings, which would be in big demand for heavy machinery on the Moon.
Comment by Coastal Ron — October 26, 2011 @ 2:00 am
Printed ball bearings are a common demo showcase of the 3d printers, do a quick google or youtube search. Most of them are plastic, but there are metallic bearings being sintered too.
>> the lunar environment is going to require the highest performing materials we can afford to make
Only if you are thinking in terms of traditional space construction and traditional manufacturing methods. With 3D printing, the design patterns would likely change. Because you would not be mass limited in anything, you probably would use low-quality materials with massive margins in the designs.
You have to flip the design equation around, i.e. go from “how do i print all the parts for a lunar bulldozer that i just designed using a 3d printer” to “having a 3d printer or the moon, how would i design a bulldozer so it could be mostly printed on site with the least amount of mass shipped from earth”
And once again, please do not think “self-replicating” as in fully self replicating, which would make no sense.
Comment by kert — October 26, 2011 @ 2:01 pm
When you consider something as complicated as a space station or interplanetary spacecraft, one of the more interesting potential applications of this technology is on-demand production of replacement parts. Instead of carrying a supply of parts and hoping you’ve chosen the ones you’ll need, you manufacture parts as needed to the extent possible. However, this might mean you’d want to use the technology to produce the original parts so the replacement parts would be identical. Otherwise, the replacement parts might not be as strong or capable as the original pieces.
It’ll be a while before this technology can produce every possible part a spacecraft might need but it could possibly be ready in the next decade or so. This could greatly simplify mission logistics. It’ll be interesting to see how well this would work in a micro-g or reduced G environment.
Comment by Larry J — October 26, 2011 @ 2:09 pm
A fun design challenge by the way. Assume you would have a set of working SLS “printers” and a few dexterous assembly robots on the moon, something along the lines of Motoman SDA10D, that could be remotely assisted.
Leave aside for a second the question of mean time between failures and whether terrestrial units would work out of the box.
What materials would be workable ? What could you print and assemble to get a lunar outpost bootstrapped ?
Comment by kert — October 26, 2011 @ 2:11 pm
Call me skeptical. If it’s so easy (or even possible) to make anything you need from dirt, why aren’t we doing it down here? Sounds more like alchemy than science to me…
Comment by txhsdad — October 27, 2011 @ 5:47 pm
txhsdad, here’s a link to some info on 3D printing.
http://www.hoax-slayer.com/3D-printer-video.shtml
There are still limits to the technology that affect the price. In the video, a 3D printer creates a cresent wrench. It takes several hours to make that one wrench and I’m pretty sure it isn’t as strong as a forged steel unit. However, the price of shipping spare parts and tools to the moon is very high. Having the ability to create needed items there for use on the moon and building them mostly out of lunar materials changes the price equation considerably.
Comment by Larry J — October 28, 2011 @ 10:05 am
Comment by Larry J — October 28, 2011 @ 10:05 am
Thanks for the link. I was really looking forward to looking at it, as I am still somewhat ‘hazy’ as to how the capture of the design is translated into a solid (useful) object.
Unfortunately the link says the video is no longer available.
Do you happen to have another link?
Comment by Joe — October 28, 2011 @ 1:32 pm
I think that this post and discussion is particularly relevant to the issue of whether we could be able to establish a self-sufficient, off-Earth colony in the near-term as an insurance policy against human extinction.
I’ll comment later about:
– basic metallurgy and machining versus 3D printing,
– a “sufficient colony”, and
– bootstrapping.
But first, some basic questions:
– Can we obtain iron easy enough simply by separating it from regolith using a permanent magnet?
– Can that iron be practically melted and purified using solar concentrators (i.e. mirrors)?
– Is iron hard enough for our equipment needs and/or is carbon in sufficient concentration in lunar ice to practically use to make steel?
Comment by JohnHunt — October 31, 2011 @ 4:53 am
John,
Some quick answers:
– Can we obtain iron easy enough simply by separating it from regolith using a permanent magnet?
Depends on what you mean by “easily.” Much of the dust grains in the regolith are “magnetic” — they are covered in vapor-deposited, “nano-phase” iron (Fe). So a simple magnetic pass will not cleanly separate pure iron fragments from the soil. It will, however, be very useful in cleaning parts and equipment.
– Can that iron be practically melted and purified using solar concentrators (i.e. mirrors)?
Depends on what you mean by “practical.” Solar thermal can be concentrated into temperatures high enough to melt the soil and glasses in it. In theory, one could then gravity separate silicate (low density) from metal (high density), but it might be tricky. Better to smelt it directly from oxides (e.g., ilmenite) milled and magnetically separated from mare bedrock.
– Is iron hard enough for our equipment needs and/or is carbon in sufficient concentration in lunar ice to practically use to make steel?
Don’t know what your equipment needs are. However, I am told by Prof. John Lewis (Univ. Arizona) that absolutely pure native iron is similar in metallurgical properties to stainless steel. I do not know if he was thinking about strength in this formulation.
Comment by Paul D. Spudis — October 31, 2011 @ 3:04 pm
3D printing could be very useful especially if the plastics could be recycled. And if feedstock could come from lunar sources, that would be even better. But I don’t know if it is necessary to achieve mining operations or a colony. I think that the things which keep RepRaps from being able to fully reproduce themselves are the highly sophisticated items such as the computer chips and precision step motors. But this is high technology and we seem to be forgetting the lower technology of the ’40s and ’50s. Rather, in aiming for a fully self-sufficient colony, I would suggest the older, less sophisticated, more reproducible approahes of metallurgy and machining.
Comment by JohnHunt — October 31, 2011 @ 6:08 pm