Back in 2006, when I was first working on ZoomIn, I decided I needed a hobby aside from computer programming (startups being quite a full on project). I had been reading the Armadillo Aerospace blog, I decided that I wanted to try and build a liquid rocket engine. So I bought a combination metal lathe and mill and $200 of aluminum stock.

I learnt a lot about metal work, how to cut the bar stock with an angle grinder, how to finish the cuts to a nice clean 90’ angle. How to center on the lathe, how to use a compound slide, how to bore out a hole. I’ve still got a collection of lathe drill bits and a nice boring bar somewhere, along with digital calipers and assorted other bits and pieces.

So now that I’m moving into a new place with a good sized man shed (and electricity!), I immediately started looking for another lathe on Trademe. But after a brief think, I decided that while milling another liquid fueled rocket motor out of stainless steel would be a fun way to spend winter evenings, I’d been there done that, I’d rather move onto the next stage.

So after a bit of googling I found the Rocket Moonlighting blog, where a guy has 3d-printed a rocket engine using Direct-Metal-Laser-Sintering. It’s an expensive process. Luckily his first motor came out right, because it cost several thousand dollars (more than the cost of the whole lathe plus all the metal I used to make my prototype engine), but the cool thing is that once you have your CAD file setup parametrically, you can just change a variable, email a design to shapeways, pay your money and wait a week and you get your 3d-printed motor in whatever size you want.

I’m probably not going to jump right into the deep end and start 3d printing and hot firing rocket motors in my back yard (I don’t have the disposable income for starters), but it did make me wonder whether I could 3d print a water powered rocket nozzle. That way I could work on most of the fun bits, ie valves, control systems, structure, and then just power it using a carbon-fibre paintball co2 cannister that forced water through a nozzle and hovered on its tail.

That’d probably be something that I could test in the back yard too - I’m not sure how cool the neighbours would be with me hot-firing a nitrous-propane engine on our lawn. I’ll definitely have a think about it, a 3d printed water-powered throttleable (solenoid PWM maybe?) rocket would be pretty awesome.