Over the Hills and Through The Woods...

It's getting close to that time of the year when the snow flies. I like to hit the mountains once there is a fair amount of snow. These pictures are from last winter after the first storm. There was 3 feet of snow in that storm. That's me snowshoeing in (uphill, both ways) with a sleigh full of supplies.

Mush, Mush I say.

Sweet Seclusion.

It's always enjoyable to be up there when the snow is coming down. I'm at about 7000' and just below the ridgeline so the clouds pile up there during a snowstorm. The snow crystals form right in front of your eyes and then fall just a few feet to the ground. It's odd, but quite mesmerizing.

How About a Nice Curve Fit?

I've been meaning to do this for some time. That is developing a Windows based system for fitting equation of state terms to experimental data, rather then relying on other people's fitting routines. One of the more common equations of state (P-v relationship) people like to use in the explosives world is the Jones-Wilkins-Lee (JWL) equation of state. There are others but I won't go into them for now. One form of the JWL equation of state for the products of detonation is given by:

The data to fit to has to be in an Excel file and can be imported directly into the application. The data file needs to be in the form displayed. The pressure units are in GPa.

A Digression of Sorts

I spend most of my time here talking about technology, and acquiring and using one's skills. What I haven't really talked about is the why. Why study this, why learn this, why write about it? The why is just as important as the how. I firmly believe humans are meant to explore and build. We also have a tremendous desire to determine how it all fits together and where we stand within it. Our science, art, religion, and our very cultures are a reflection of this desire. We also have a need to understand the way things work so that we may prosper as an individual and as a species. Anything that furthers this goal of knowing we undertake. Sometimes for better, sometimes for worse.

The Covid-19 pandemic is an excellent example and has brought a few things into better focus for me. I have worked my whole adult life around hazardous materials and under hazardous conditions. It's not my death or injury that concerns me, I'm used to taking that into account. A pandemic, and the response to it, potentially threatens our society and that is an entirely different matter.

Properties of Explosives and Their Application Part 3

Energetic materials in general and explosives in particular are incredibly important to an industrial/technological society. For propellants it's their ability to produce large volumes of gas in a short time frame during combustion. Rocket motors put our satellites in space that provide us with other forms of important technology. The airbags in your car are nothing more than an energetic material undergoing rapid combustion to fill the bag. I don't think you want to know what energetic material is probably in there.

The usefulness of explosives comes from the fast generation of gas, on the microsecond timeframe or less, that provides a large power density and amount of work available. This allows us to do extensive momentum transfers for a relatively low cost (blasting for mining and construction). The metals production industry, and subsequent manufacturing industries heavily depend on the low cost production of raw materials. The power densities in explosives allow for the high velocity acceleration of metals which produces the shaped charge effects needed in oil and gas well completion.

Terminal Ballistics: It Was a Really Bad Day on Earth

I've posted about some aspects of interior and exterior ballistics but I haven't mentioned the last part of the puzzle, terminal ballistics. Approximately 65 million years ago, it was a very bad day for planet earth. An asteroid impacted at hypervelocity speeds and the ensuing disaster killed off a vast percentage of life on earth (nearly 75% of all species). So this post is about terminal ballistics or impact phenomena. 

But first, a video simulating that asteroid impact. The projectile is a nickel/iron mix and the planet is simulated with a layer of water over silica. Consider the scale of the impact. In the model the projectile is scaled such that it would have been about 8 miles long by about 5 miles in diameter. The resulting crater depth would have been nearly 10 miles or roughly twice the height of Mt. Everest.

Building an Outdoor Oven

One of the first things I did after I built one of my houses was to pour a patio slab and build an outdoor oven. I enjoy doing the holiday cooking outside. I can cook a 20 pound prime rib and a big turkey in my outdoor oven without batting an eye. Near the end of the cooking I'll throw cast iron Dutch ovens in for my bread. The cooking process is simple. 

How to Do Holiday Cooking Outdoors

As If I Didn't Have Enough To Do

It's always rather surprising to me when people discuss certain aspects of  subjects and I discover they don't read much about the work in the field under discussion. What I have come to find out is that often times people just don't know where to look. I've solved that problem, sort of. There are 10's of thousands of journals from around the world that have open access, meaning free to download. This is why I said I have sort of solved the problem. You still have to do the reading.

Every week I spend at least 4 hours reading journal articles in fields of study I'm interested in. This is a habit I would encourage in anyone with a thirst for understanding. I used to spend a full day of work once a week doing the same thing with the published and bound dead tree version. If you like that sort of thing, I still do, go to your local community college, or university library and find the journals. These days though this wild and wooly thing we have called the Web has lots of resources.

First off, the Directory of Open Access Journals. Just search by keyword(s) and you're off.

Next up, Open Access Journals. This link takes you to the journals by subject.

Ok, for the pirate in you there is Sci Hub for journals behind pay walls. They have by-passed them. Sometimes you might have to follow them around as they've been sued by publishers several times. You might open yourself to civil action in the United States by using the site, so if you go there understand what you are doing. I think they are currently down, probably on the run again.

For United States defense related research, and a lot more, there is the DTIC or Defense Technical Information Center. For most US government labs and centers each agency will usually have a publications outlet site. 

A lot of people think that these journals are primarily for the experts in those fields. That is only part of it. They are meant to communicate your work to others in that field sure, but also many of the articles are written with a broader audience in mind. So dive in, the water is great.

It's Never Been Like This Before

Every so often I'll get in a conversation with someone about our droughts here in the mountains of California. The snow pack in the Sierra Nevada mountains is the major source of fresh water in the state so knowledge about it is vital. Fortunately there is data to be had that I can use to inform myself. I get the snow pack data for the two watersheds I am interested in from the California Data Exchange Center.

I update my files every year at the end of the snow season. This is usually April 1st. It's always surprising to me when people talk about the Sierra snowpack from news reports they hear or see, but don't actually look at the numbers. In fact some of the things I hear from people is so far from what the data implies it's troubling. Let me be clear from the outset, this is not about the overall water situation in California. It is about the two watersheds that directly impact my life. They are the Kern River Watershed and the Owens River Watershed.

Seki-Joju Bonsai and The End of The Season

I've finished up most of my horticultural work for the year and soon it will be time for the plant world to rest for the winter. We don't have much of a fall here but when winter descends it comes fast and with a vengeance. I planted my newest bonsai in its pot and it seems to be thriving. I have it wired for training and the root system is strong.

Seki-Joju Style Bonsai.

Down The Rabbit Hole

Charles Dodgson who wrote the wonderful book Alice's Adventures in Wonderland under the pen name Lewis Carroll was a mathematician by training and practice. His book was admirably illustrated by Sir John Tenniel. Dodgson  made some good strides in mathematical logic, linear algebra, and matrix operations. Of course, who doesn't remember who Alice spotted one fine day and decided to follow. 

 

Our notorious white rabbit, and so down his rabbit hole we go to do some exploring. Namely data, mathematics, curve fitting, and models,  all of which would be familiar territory for Dodgson. I was planning to post on a completely different matter when I realized I have been remiss, and that I needed to better define some things. 

SIR Model Revisited

I've gone back and cleaned up my basic SIR Model as described in a previous post. I have added some features and put some more thought into it. I hope to describe it here and what might be some of the ramifications. Given the current state of political affairs here in the United States and being the election season it has helped me wade through some of the effluvia that is always present in politics. Especially concerning this matter.

Properties of Explosives and Their Application Part 2

From the first post in this series I wrote about determining the performance of an explosive using the Cylinder Expansion test, or Cylex as it's commonly known. As I mentioned the radial velocity of an expanding cylinder (copper for the cylex test) is measured. This is done a number of different ways. The earliest method used a streak camera.

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.