Drilled brick nozzles

The stuff does not drill easily and neatly. You could form the nozzle in place from "Leak Fix" cement. The kind used to repair leaks in the basement walls. It expands when cured and will stay in place. I have made some from ceramic also, formed them soft and had them baked. Local craft shop had ceramic lessons and I enrolled and made a bunch of nozzles. Tom

If you don't have access to a lathe and some graphite, this is an excellent idea!

James

I've thought that there are possibilities along this line for making composite parts, if one could get some high-strength ceramic fiber, wet it out with clay "slip", and then lay it up in the desired shape and bake it...

-dave w

Only if you're burning relatively-low temperature propellants. It might work out OK for KNO3/{Sucrose,Dextrose,Sorbitol}, but for aluminized APCP, you'd likely see substantial erosion. And no way will it work for hybrids.

I use firebricks on one of my test stands on the blast deflector. The stuff actually melts and flows, leading me to believe that it would be a relatively poor material for nozzles.

For sure I'm talking about simple single use motors. What I love is that this way nozzles come one per 5 seconds (well, there is some thinking about how to make them tight in motor case). For sure brick can't match grafite, but is it really worse then just clay? If yes, there is a lot of stone-like materials to drill, so I just have to test. KNO3 is only oxidizing stuff available here, so my choices are candy or kno3-epoxy.

Really. Can't be any worse than "Durham's Water Putty". Talk about erosion. I did my first batch of pvc test motors with it a few years back. Composite ate that stuff alive. At least I was smart enough to put a steel insert throat into them, or my "a" and "n" results would have been even more questionable. I have since refined my methods. And bought a lathe to turn graphite (among other things).

James

If you don't have a lathe, how can you turn the bricks? Sure, you can drill out the nozzle but you need a way to shape the rest of it too, right?

Brick sounds porous and therefore inclined to deal with heat unevenly and be mechanically weak.

I would think a better alternative would be to 'cast' your own, if you don't turn them on a lathe.

I'm thinking something you pour in a mold that either self-sets (cures) and/or later gets fired in a kiln.

Speaking of nozzles, are semi-exotic metals any help? Thinking of Titanium. It's more expensive than more common metals but you don't need _that_ much, do you?

TBerk

Titanium would be a bad choice.

Take hole-cutter of the same dia as motor casing and centering drill bite of the size of nozzle-hole you want (problem is, hole-cutters come with some standard dia centering bites so if it don't fit your design, you have to drill central hole one more time to get right dia). Shaping the inner part of nozzle is easy with $5 conical milling cutter and drill. Outer surface will stay as it is and will be glued (epoxy or clay, cement) to the casing. Remember, we're talking about simple single use motors - idea is to keep costs of tooling and materials as low as possible. Roughly: hole-cutter $10-12 (profi stuff $30), milling cutter $5 (or $10 if you take different angle cutters for inner and outer end of nozzle), brick or tile ? $1?. Hopefully hand drill is in household anyway.

Best

Vello

But this will be in many times more time. There are different materials to try, stone floor plates at first.

Melting point: iron - 2750 F, steel - 2500 F, titanium - 3034 F. Not big gap, but sure titanium nozzle will be lighter. What I can't know is the thermal stability of titanium. Titanium is melted and welded in vacuum, due "extremal reaction with oxygen in high temperatures"(Google). Price must be not too high - but no idea about retail shops:-)

Vello

Go ahead with titanium! Look

Wouldn't work with anything but KNO3+Sucrose or cooler. APCP composites, bi-props, and hybrids generally burn hotter than the melting point of titanium (1600C). And most titanium isn't pure, it's alloyed with other materials like iron, aluminum, etc. Which often lowers the melting point.

It doesn't say what these particular nozzles are for, but it wouldn't surprise me if it was for an RCS system with relatively low throat temperatures (or they're regen cooled--but it doesn't look like that in the cited article).

Graphite really is the material of choice for the amateur experimenter, and it *can* be machined without a lathe. In fact, graphite machines quite well generally, so the suggested method of using a hole saw to cut out slugs would work modestly well.

Cool! Looks like a big, high tech version of an Aerotech Medusa nozzle. I would have thought titanium would burn, though.

Isn't graphite too expencive for single use motor?

Do anybody know what they use in military/professional (apart of hi-tech composite materials)? Wolfram?