Monday, July 20, 2015

Feasibility of DIY 3D Printed Guided Missiles

The day of 3D printed guided missiles is now upon us.


Raytheon has announced that they are now 3D printing a missile.

If one looks very carefully at the photo, It is obvious this model was created with a desktop 3D printer.

But how would one theoretically create such a beast in their own shop?

First of all one needs a engine.

This model appears to have a solid fuel design although a hybrid model could just as easily be made.

Low cost solid fuel motors can be made from sugar and salt-peter.  Commonly known as Rocket Candy.


Rocket Candy is a type of rocket propellant for model rockets made with sugar as a fuel, and containing an oxidizer. The propellant can be divided into three groups of components: the fuel, the oxidizer, and the additive(s). The fuel is a sugar; sucrose is the most commonly used. The most common oxidizer is potassium nitrate (KNO3). Additives can be many different substances, and either act as catalysts or enhance the aesthetics of the liftoff or flight. A traditional sugar propellant formulation is typically prepared in a 13:7 oxidizer to fuel ratio.

Hybrid motors on the other hand use a combination of solid fuel like plastic.  This plastic could be Delrin, PVC, even rubber.  Since we are looking at 3D printing, we could 3D print the core as well.

From Wikipedia, the free encyclopedia


Hybrid rocket motor detail of SpaceShipOne
A hybrid rocket is a rocket with a rocket motor which uses rocket propellants in two different phases. - one solid and the other either gas or liquid. The hybrid rocket concept can be traced back at least 75 years.[1]
Hybrid rockets exhibit advantages over both liquid rockets and solid rockets especially in terms of simplicity, safety, and cost.[2] Because it is nearly impossible for the fuel and oxidizer to be mixed intimately (being different states of matter), hybrid rockets tend to fail more benignly than liquids or solids. Like liquid rocket motors, but unlike solid rocket motors, hybrid rocket motors can be shut down easily and the thrust can be controlled with a simple throttle. The theoretical specific impulse(I_{sp}) performance of hybrids is generally higher than solid motors, and roughly equivalent to hydrocarbon-based liquid motors. I_{sp} as high as 400s has been measured in a hybrid rocket using metalized fuels.[3] Hybrid systems are more complex than solid ones, but the significant hazards of manufacturing, shipping and handling solid rocket motors offset the system simplicity advantages.

The oxidizer for the DIY versions commonly is Nitrous.  Yes the same Nitrous used to boost car horsepower in drag racing.

Body


The body of such a design could be 3D printed with the exception of the motor casing, nozzle, and fins.

One could possibly print it in such a way so as that the solid fuel core and the outer shell is hollow like a mold where one could pour Phenolic Resin into.  A slow cure Phenolic resin that does not generate much heat could withstand the few second impulse that a small motor like this would generate.

Similar to this simple 3D CAD sketch I created below



Guidance systems.


This is where technology has come thru in machine vision that has flown under the radar.

The Pixy machine vision project (open source) has the potential to be uses as the guidance system along with some custom source code. 
Code and more info can be found below.
Available from Amazon. 
Using a infrared laser and using this type of code (example here) a engineer could replicate a laser guided rocket.

This is a project that will take a certain level of advanced coding expertise and skills, but not out of the realm for a really good fabrication lab.  A lot of this fabrication is beyond my skill level, However a couple engineering grad students could replicate this.

This is where the world is going to.  The USGOV technological advantage is being eroded before our eyes and invented in home workshops.

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