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.

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.

This is my Rifle...

This is my gun... I don't suppose I need to repeat that little ditty that one picks up in Basic Training in the U.S. Army. I assume they don't use that anymore given the coed nature of the Army these days. This is the object I'm speaking of.

Some New Ballistics Calculators Added

As I've been developing my Android application for a shooter's assistant I've also been putting the pieces I need to make it function in spreadsheet format. The recent one I have completed was looking at the exterior ballistics problem using Pejsa's Methodology which you can read about at the link. An internet search will bring up a number of uses of it. I have provided my version of it in my downloads area. The spreadsheet can be found here.

Ballistics Calculators

I've been working on a system to take with me shooting. It's essentially an external ballistics application for my Android phone that gives me bullet path calculations. It's not meant to be a whiz bang super ballistics calculator that will tell you everything for every bullet and condition. It's set up to calculate the functions I want for a limited number of cartridges, loading conditions and projectiles.

The first thing I did was develop the means to make any corrections needed for the flight path due to temperature, humidity or altitude. These can be all lumped together by calculating the air density. This is the circuit for the Assistant set-up. It's a little module (Bosch BME280) that reads temperature, atmospheric pressure, and relative humidity. I use those inputs to calculate the air density. It also accounts for any altitude corrections that might need to have been made through the direct reading of the atmospheric pressure. In fact the manufacturer likes to claim you can get an altitude within a meter or so from it. The values are read in and sent via Bluetooth to my Android app.