Test objects

I printed up a couple of test objects to see how well a 3D printer could produce the substrate for a first-surface mirror.  Just a couple cm long.  Pretty good results, with some concerns.

- slump.  There's a real danger that the mirror will sag while bing printed.  Very bad given that I need soe degree of precision, especially if I'm building an array of small mirrors.  I'll need to take preventative measures in mirror design (vertical support for the curved surface from the bottom up)
- the thickness of the layers affects surface smoothness and slump

Next task: mirroring.  I've picked up some chrome paint.  Chrome paint has a pretty poor reputation for actually producing an even shiny surface so we'll se how it goes.

First you get the sugar...then you get the power...

Disappointingly, my PLA plastic has yet to arrive.  I'm wondering if it's been misdirected in shipping.  I'll need to look into it.

While waiting I had an idea: sugar.  There's precedent for 3D printing sugar objects, though my idea is a bit different.

Move the focal point of a mirror over a bed of sugar.  A point heat source can caramelize sugar; think of the way a butane torch scorches a creme brule.  Sucrose caramelizes at 160°C.  Having browned a 2D pattern, add a thin layer of sugar on top of the bed and repeat.  The layers should be thin enough that each layer fuses to the one before.  When all necessary layers are complete, the printed object can be lifted out of the bed of sugar, extra sugar being shaken off.  Might work.  One challenge: sugar darkens as it caramelizes, and a darker surface absorbs light better.  The rate the sugar is being heated would go up just when heat is no longer required.

Maybe I'm just feeling a bit bitter.

Handheld mirror: Plan A

So, here's the first proper test mirror I intend to make.  The plan:

- First surface mirror
- 3D printed PLA plastic substrate
- Off-axis mirror
- approximately 20cm x 20cm

Details inside

Everybody needs a hobby

A few weeks ago I had an idea for an odd little hobby project: solar sintering.  I was inspired by this art project by Markus Kayser.  It struck me that a much smaller scale project would be a novel way of 3D printing plastic objects.  Fun.  Using paraboloid mirrors rather than a Fresnel lens would make it quite inexpensive to build.

Part of the appeal of the idea was that there was the option of taking it in a more ambitious direction, with some difficulty.  As demonstrated by Kayser, it could be scaled up to 3D print ceramic objects by melting sand into glass.

The idea was also appealing for another, somewhat more whimsical reason.  I like to read about space-related technology, but I suspect that any large scale project outside Earth orbit would be economically impractical without space-based manufacturing.  There's a problem of where to begin.  Something like lunarcrete is a good idea (more on that later) but fabricating it would require assembling a whole factory.  In contrast, a small array of mirrors capable of sintering lunar regolith could be made comparable in mass to probes currently being sent to the moon on a semi-regular basis.  An idea worth considering, perhaps, or at least amusing to imagine.  Call it a Lunar Industrial Module (LIM), hence the title of this blog.