Questions about Rocketry

I Remember back in the day Estes sold a Cold Rocket Drag Car kit. It essentially used 1 pound R12 cans with a dip tube and a “special” nozzle. We quickly found out we could just buy R12 at the auto parts store for $0.50/can and turn it upside down. Estes version was $3.25/can.

I feel I have personally destroyed 10% of the ozone layer :wink:

EDIT: Found they are doing it with Air Brush propellant these days http://www.rocketsmagazine.com/RocketsMagazine/Issue0023/sample.pdf

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If you proceed with Propane due to cost (which I completely understand), your “firings” should be done in an open field with no ignition sources around. Preferably on a windy day to dissipate the gas cloud quickly.

At the risk of going off-topic a bit, don’t fire up your diesel truck right after this, or you could find yourself with a runaway engine. Diesels have no throttle and don’t care where the fuel they are burning came from (injectors or pre-mixed in the intake air stream), and there are plenty of rather spectacular YouTube videos of engines blowing themselves up when someone operated them around flammable gasses (near petroleum wells, etc.)

Whether you can 3-D print the components depends on the amount of pressure you expect. People have built water rockets, water expelled by compressed air, using soft drink bottles and many of these can go hundreds of feet into the sky.

Because you are not planning to fly it, your working model need not generate a large amount of thrust or operate for a long time. That makes your job much easier.

Exactly! This is to prove a concept and learn how to fine-tune it. Once we can predictably alter the models behavior by swapping parts, I’d say we could move into making more powerful motors capable of flying something. And that will not be done with abs, but more conventional rocket building materials (like graphite, aluminum, carbon fiber, etc.)

Also it does seem that there is more interest in this project than I initially thought there would be. Anyone who would like to participate in this project: please post good times for you to meet up and we can try to schedule a night to meet at DMS and hammer out the details together.

The Qu8k team has done some amazing things with rockets:

http://ddeville.com/derek/Qu8k.html

Pressurized 3-d printed ABS.

This makes me wonder, does ABS shrapnel show up on x-ray? I have heard PVC doesn’t …

X-Ray is so 19th century… CT-scans should work.

Seriously though, a quarter inch of plexiglass should be enough shielding to protect for experimental purposes. Simply being alive is a certainty of death. Lets not get too worried about danger. A few simple precautions and nearly any subject can be researched with some degree of safety. And if it isn’t enough, the next person to do the research can learn from your mistake

http://www.reviewjournal.com/sites/default/files/styles/large/public/field/media/web1_test-site-jul25_2.jpg?itok=wkiOC7v5

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Looks like those shots were taken at Balls/Black Rock.

Nope, That is PGI (Pyrotechnics Guild International) Laporte, Indiana last summer. Just kidding, but we made similar visuals. :wink:

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I don’t see any good reason it shouldn’t work besides the ABS failing. As far as temp control goes, I wouldn’t sweat it. If you actually cared about temp, the thing to do would be to heat the gas up as much as possible like in a normal rocket; the way the nozzle works is it essentially converts the thermal energy into kinetic energy (it’s not exactly that, but I say it’s permissible to think about it like this).

How much do you have already worked out besides the fuel / propellant? Rocket nozzle design is an iterative PDE iirc (method of characteristics is the name), so unless you want to literally design the bell shape, I’d look around for a software or something that does it for you.

I’ve got a compressible aerodynamics book that might come in handy. It’s been a while since I took the class, but I bet if I spent some hours reminding myself, I could probably work something out.

Also thermodynamics.

Briefly reading about your propane / carbonated salt water … can you explain to me how you intend to mix these continuously?

Regarding propane in the local atmosphere, I have a fun story involving the accidental discharge of probably 100 gallons of propane when a tank’s stem got stuck open and my father and I could not get the hose back on. It is still the loudest thing I’ve ever heard, so loud I had to cup my hands and scream at the top of my lungs directly into my father’s ear to be heard. It so happens that as a result I know breathing in tons of propane makes your lungs hurt somewhat.

I witnessed firsthand the use of leftover propane in a fill hose to rapid-chill a couple of cans of beer. :slight_smile:

Wonder how the new 3d printer’s resin stands up to temperature :slight_smile: @themitch22

For the combustion chamber I have a few designs in mind as I am not sure if they will work or not. The first and simplest is a simple spherical chamber, filled with glass beads/marbles/airsoft pellets (Basically anything round, not destroyed by the reaction and too big to squeeze out the nozzle) with a custom printed manifold at the top that has the propane coming out inside a jacket of water (not sure how to explain the geometry, but it shouldn’t be a complicated print and I can draw it once we get together). Secondly using a very similar manifold, you could possibly just angle the water inward tward the propane stream (kinda like an aerospike nozzle, where the spike is a jet of propane) - The benefit to this design is that you should be able to get away without anything inside the combustion chamber, affording you a much smaller, and less encumbered combustion chamber. Third is a series of directly opposed injectors inside a cylindrical combustion chamber - Benefit to this is that the geometry of it makes it the easiest to mount in rockets if we actually get to that phase for future projects. These are just the ideas I have. The point of this model is to experiment, so if anyone has any ideas of their own I would encourage you to share them. Variety is the spice of life! :smiley:

This stuff may be worth looking into.

It would be interesting to play with, but I did find this:

…“We have no specific data about the thermal conductivity but there is little to no conductivity in copperFill due to the dominance of the base material, PLA/PHA.
The material is intended as an aesthetic material primarily.
Please keep in mind that due to the mix with PLA/PHA the Glass Transition temperature is relatively low so thermal applications will be limited.
There is roughly 80% metal in the filament by weight.
Both FAQ’s can also be found here in our Frequently Asked Questions list.
The datasheets of our materials, including the density, can be found on our materials page.
For copperFill this is listed as 4,0 g/cm³.”

My assumption is that this would be intended for copper’s thermal conductivity. Feel free to correct me if I’m wrong.

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This did get me looking around at other types of filament that may be useful, and I came across LAYCeramic which may be nice. It has a major drawback of inaccuracy, however, (It must be fired in a kiln after printing, and this will reduce it’s size by a less-than-accurate amount, ~25%) Though, after firing in the kiln, it should be able to handle temps of ~1200 degrees.