Properties of Explosives and Their Application Part 1

This is the first part of a series on the properties and application of explosive materials. I suppose the first thing to do is define some terms. An explosive is any system, gas, liquid, or solid, that will propagate a supersonic wave front at a characteristic velocity that is supported by chemical reaction. A graphical relationship helps to show this.

One of the first aspects of explosive performance is the ability of the reacted material to move metal.  The Gurney Equations describe this well. R.W. Gurney did much of his initial work in Quantum Mechanics but later moved to the United States and was very productive in the field of metal motion due to gas dynamics from explosions. Gurney's equations could be considered near universal for many explosive systems. A copy of his original document is here in the Open PDF section of my Google Drive.

Introduction to Explosive Materials

Much of my work over the years involved testing and developing explosive systems. What I hope to do with this series of posts is to describe in a succinct form some of the background, both theoretical and experimental, that went into my work. This series of posts is an overview of explosive materials and their uses. It's similar to some texts available but I will be including links and various downloadable items that some readers might find useful.

There are three basic types of explosive materials: primaries like azides and fulminates; secondaries such as HMX, RDX, and TNT; commercial, which include variants of ammonium nitrate/fuel oil used in the mining industry.

Of Course

Now that I've cured and tacked out the Mojave Green skin there seems to be some debate over who gets the resulting product. Isn't that always the case once the work is done?

Meanwhile the skin is drying nicely. I make sure the skin is up off the board so that air can circulate freely.

Show Me The Model

I've been exploring the model space and it's a dark, cold place. You can get lost out there. I developed a basic SIR model for disease transmission and recovery and set out to turn the knobs on the values. Recall the original model looked like the graph below. What you can see is that the blue line is very nearly at zero and the green line is approaching 1000 or the total population that I used.

The blue line being very nearly zero means there are very few members of the population left that are susceptible to the disease. The red line indicates the infectious which are the people currently suffering from infection and potential death. "Flattening the curve" is spreading out the red line in time which can be accomplished by reducing the transmission rate (social distancing.)

That Took A Bit of Work

In my "What This Blog is About" page I mention about doing something yourself and then explaining it to someone else so you can really start to understand something. I have been asked a number of times my take on the Covid 19 business, and I have tried to stay honest and say I don't know enough about it to offer up much in the way of an opinion. I have been trying to rectify that ignorance and have made the first steps. This is my description of what I know to this point and what I have done.

That Should Do It

I've finished my shooting Android application to my satisfaction. It has my current burn model in it and some, I repeat some, error checking in it. As usual it can be found in my Downloads Section under Mk1ShooterMod1.apk for the built Android App and Mk1ShooterMod1.aia for App Inventor file.

...Onward Through The Fog.

A Burn Model Updated

I decided to put together a simplified burn model to incorporate into the Android App I put together for re-loading and exterior ballistics calculations. It gives me a little better feeling for the overall veracity of the application. The powder mass function was developed with a 4th order Runge-Kutta scheme which can be found in the Open Calculators downloads section of the blog. The velocity was derived from a lumped parameter energy balance model. I used a thermochemical solver for developing some of the powder constants. I'll probably put together a thermochemical solver for here which will also be useful for detonation and explosive properties calculations which I plan to write about in the future.