Hall Consulting's
Hybrid Gun Design Tool


What is HGDT?
HGDT is my best attempt at a simulation of combustion-based gas cannons. In other words, "spud guns." Simple combustion. Advanced combustion. Hyrbids. HGDT should be able to do all three. The idea is to plug in a bunch of known parameters about the gun in question and have HGDT tell you what's going to happen with a reasonable degree of accuracy.

How accurate is HGDT?
As of this writing, the answer to that question is unknown.

How does HGDT work? Can you give me the equation(s) behind the curtain?
HGDT is not a simple set of equations for which a few variables are plugged in and answers spit out. It is a full-blown one-dimensional simulation. So if you're a student who's looking for information for a science fair project or something, all I can tell you is to read up on Newtonian mechanics, thermodynamics, gaseous combustion and compressible flow. If texts on those topics are beyond your comprehension, then so too are the inner workings of HGDT. If those same texts are within your comprehension, then you probably know everything you need to know about how HGDT works (or at least have much more specific questions).

What phenomena does HGDT attempt to take into account?
Oh, geez. That's a tough one to answer. I tried to take a LOT of stuff into account and I'm likely to forget to list them all. However....

What phenomena does GGDT not take into account?
Alas, no model is perfect and I am far from being a world renowned expert on internal gun ballistics. I wish I could claim laziness, but the simple fact is there are some topics for which I simply do not have the mental resources for. These topics were as a result, ignored....

Will you release the source code to the public domain?
Not just, "No." "Hell no." Don't like that answer? Go write your own HGDT-like application and release it yourself. I've written and released code in the past. It's a nightmare: Two weeks after initial release there are 47 versions of the code running around and everybody is coming to you for the answers to why their version isn't working the way they want it to work. No thanks. Never again!

Are you ever gonna release a version for the Macintosh?
Not unless somebody pays me my hourly rate ($100/hr if you're serious).

I've got an Acme Model XYZ gun. What are the design paramters for input into HGDT?
Off the top of my head? I have no idea! I'm trying to build a library of sorts (it should be pretty easy to find from the main menu), but very few people forward useful data on such stuff to me. Your best bet is to visit the Spudfiles Forums and ask around over there.

Who are you? What's your day job? Why do you know all this wierd stuff?
My name is David Hall. I'm a Mechanical Engineer employed at the Naval Air Warfare Center, Weapons Division, Ordnance Test & Evaluation Branch. I started my career writing flight simulations. These days I test rockets, and guns for the military. Combine those two assignments and voila.

OK folks, that's it! If you've got a question, ask me.

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