It costs about a thousand dollars to loft a pound of anything into space. Scientists, astronauts, and project managers are therefore understandably careful about what they choose to send to the International Space Station.
Years of careful planning precede any launch and determine the contents of any launch payload. But as we all know, plans change when they encounter reality. So what happens when an astronaut on the space station needs something that didn't get packed into a shuttle payload?
They make do. The most famous example of the make-do spirit was the Apollo 13 mission, where - after an oxygen tank exploded in the command module - the astronauts had to survive in the lunar module. To do so, they had to build a carbon dioxide scrubber adapter from found parts, which consisted of the cover of the flight manual, duct tape, a pair of socks, and various other components.
While emergencies will undoubtedly still happen in space, and creativity and resourcefulness will still be necessary, NASA researchers have been working on an approach that could provide space station astronauts with a supply of objects, tools, and components using 3D printing.
This is an extremely powerful idea. Think about the general-purpose computer. Once it was possible to create one device that could run many different programs, the computer because an enormously flexible machine. It could be built and installed well before all of its uses were defined or even discovered. When a new program was needed, that program could be coded, and the same physical piece of machinery could run everything from inventory replenishment calculations to plotting missile trajectories - which have reached their cultural culmination in the computation of the flight path of small birds aimed at clusters of small, green pigs.
The general purpose computer is a single machine that can run a wide variety of programs. Likewise, a 3D printer is a single machine that can produce a wide variety of objects.
Scientists at NASA have seen the potential. This one machine can live on the space station and generate an almost infinite variety of objects, tools, and parts. Instead of, for example, waiting for the next shuttle mission to loft a special-purpose wrench to the space station, engineers can just email an .STL file to an astronaut on the station, who can print it out and put it to use.
In fact, there is a 3D printer on the space station, made by the firm Made In Space, Inc. The printer is a fused deposition modeling (FDM) printer very similar to the desktop 3D printers we've been using here in the DIY-IT 3D printing discovery series. In fact, one of the test objects printed on the station's 3D printer was just such a wrench, a small socket wrench shown below.
NASA has even made plans of the wrench, in STL format, available online. So, I decided to download the file and give it a run in my MakerBot Replicator. A special shout-out of thanks goes to MakerBot for providing the printer for our DIY-IT discovery series.
Printing the wrench
Printing the wrench turned out to be a very simple project. All I did was load the wrench into my slicing program and send it to the printer. I did, however, run into a number of problems creating an actual working unit, but those problems were limitations in my tools, not in the file or the 3D printing concept.
I have a printer that is designed to print polylactic acid-based plastic, otherwise known as PLA. PLA is biodegradable and based on corn starch. It's a reliable printing material and has the benefit of not only being good to the planet, it doesn't generate the acrid plastic smell that acrylonitrile butadiene styrene (ABS) plastic is known for.
While PLA is an ideal printing material, it is a little more brittle than ABS. There are ABS printers out there, but they often require a heated build plate and an enclosed printing area. My printer has neither. If you want a good example of something created from ABS, think of Lego bricks. There are roughly 400 billion Lego bricks in the world, and all were made from ABS.
NASA's space station 3D printer is also designed to print ABS, so the wrench design was specifically intended for an ABS printer. I tried it on my PLA printer.
I disregarded the design specs in another way as well. I decided to use the slicing defaults of MakerBot desktop, which included setting a 10 percent infill. Infill is the amount of plastic used to fill solid spaces. Rather than filling the entire space with plastic, various infill percentages generate diamond or honeycomb shapes inside the object. These often provide good strength and both reduce the amount of plastic used and the time used to generate the print.
My first print used 10 percent infill, so as soon as I tried to wrench anything with my first printed wrench, it broke.
My second attempt was unsuccessful as well, because after a little while, the print started to warp, lifting up off the print base. This is because, as layers cool, there is a difference in temperature between the lower layers (which are cool) and the upper layers which are warm. The difference tends to pull the print up off the printing base, and so my second wrench print, this time printed with 100 percent infill (or completely solid) failed due to warping.
Given how long it takes for prints to complete (roughly five hours each), I ran out of time after two prints. You can watch my video at the beginning of the article to see the process in more depth.
Even though the project failed for me, I learned some valuable lessons. I gained a tangible lesson about the strength of the plastic and the relationship between infill percentage and strength. I got a chance to experiment with an actual tool design intended for the space station. I learned a bit about how warping takes place as you increase the infill percentage - and I learned more about build plate adhesion. Finally, I learned that even though this project didn't succeed in the time frame I had available, the discovery process is just that, all about discovery. By attempting this project, I learned a lot and had fun doing it.
If you decide to try making the wrench, especially if you do it with ABS, please let me know how it worked for you in the comment area below.