3D Spare Parts

There are some folks who make their living forecasting the future. And they’ve done fairly well. After all, where would we be without our jet packs and flying cars?

But I suppose I shouldn’t make fun of them. Once upon a time they forecast we would have portable TV screens so we could see who we were phoning and be seen as well. They were predicted to be strapped to our wrists, but our smart phones allow us to do just that.

By now, of course, we were supposed to have settlements on the Moon and Mars and we should have been experimenting with hyper-drives to get us to the stars. Umm…not yet.

Still, we do have an International Space Station orbiting our world, at least pointing us in the direction of lunar colonies and trips to Mars.

I suspect that one of the reasons the prognosticators were so wrong is because they didn’t exactly think the problem through. It’s fine to imagine mankind living in environments as hostile as space or some orb without a useful atmosphere, but the engineers who actually design things have to ask themselves a very hard question: What will our brave pioneers do if something breaks?

Let’s imagine that your wonderful, technically sophisticated, vacuum-assisted space toilet decides to stop working. Granted, the space station has more than one, but you still run out of toilets pretty quickly. And you can’t call up your friendly neighborhood plumber to make a house call.

Okay, as it happens, you’ve got a crew that contains some of the finest engineers available. Surely they can disassemble a toilet. But if something inside is actually broken, Home Depot is also not going to be making house calls. Here is where the astronauts have to depend on another crew of engineers.

There are people in the space program whose job it is to anticipate exactly these sorts of problems. They create lists of potential failures and rate them both in order of fatal consequences and in order of probability. Then they look at one other factor: weight.

Their ulcer-making job is to come up with the spare parts list for the space station. If a spare part has a low weight and fair probability of failure, it goes on the list. If it has a moderate weight but potentially fatal consequences if it isn’t promptly replaced, it goes on the list. But if it weighs a lot and isn’t too likely to fail, it’s off the list.

Why all this fuss about weight? Using current technology, it costs a lot to lift anything up to the space station. As of a few years ago, the figure was $25,000 per kilogram. And the list of stuff that finally made it onto the space stations spares list comes to well over 10,000 kilograms. All that stuff is up there, just waiting for something to fail.

It doesn’t stop there. Each and every supply mission to the station carries as part of its cargo more spare parts and returns with a load of used-up spares. Human devices are simply not made to last forever.

So here we are with thousands of pounds of spare parts we had to lift into orbit that may never be used. And Murphy’s Law says the odds are pretty good that the next thing to break was not included in the current set of spares.

But if that seems bad, remember that the space station is only 260 miles up. The moon is about 240,000 miles away, and the minimum distance to Mars is 40,000,000 miles. A bit of a distance for a, “Sorry, Mom, I forgot my tool kit” phone call.

Believe it or not, NASA and a commercial outfit are currently working on an out-of-the-box solution to this whole problem: 3-D printing spare parts.

3-D printing is an existing technology that uses any one of various techniques to build up three dimensional objects by gradually adding material, following a pattern contained in a computer program.

Like this: Imagine a normal inkjet printer. Instead of ink, fill it with some gel that solidifies when exposed to air. Now imagine that you print a pattern of gel. Then you add more gel on another pass. You build up the gel, layer by layer, until you have a nice, solid object. Or, instead of a gel, imagine you deposit a layer of plastic with each pass. When you’re done, you end up with a sturdy, completely functional plastic part. And there are actually some processes using lasers that yield metal parts.

So, in principle, you could toss out that dead weight spare parts list, or most of it, anyway, and simply pack yourself some raw materials and a printer and a flash memory with the designs for all your spare parts. Break something? Just print yourself a new one. And, if you think this sounds crazy, they have already tested a prototype microgravity 3-D printer in the “Vomit Comet” and it worked just fine. Next year it will be going to the space station.

But wait, there’s more.

To the strange people who design space foods, they are all essentially just various organic materials that can be powdered, mixed with oil or water, and then prepared for eating. So instead of opening a freeze dried package of something labeled “Beef Stew,” imagine you go to your 3-D printer and just dial up a pizza.

And, yes, they’re actually working on this right now.

So after all the disappointments of those wonderful future predictions, isn’t it weird that they are finally coming up with gadgets that spookily resemble Star Trek’s “replicators?” Just dial up a cup of coffee and it makes the cup and the coffee.


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