Hall Consulting's
Hybrid Gun Design Tool

Main Window Messages/Warnings/Errors

As previously discussed in the Main Window Output portion of this webpage, HGDT's output portion of the main window includes a text box in which any detected warnings and/or errors are displayed. All warnings/errors, their precise meaning, and how HGDT deals with them will be discussed below.

ERR: Chamber volume <= 0
Most likely cause is the chamber's inner diameter being larger than it's outer diameter. In response, the simulation is terminated.

ERR: Disc fails during fueling
The failure pressure of the burst disc is below the pressure required by the current mix specification. In response, the simulation is terminated.

ERR: Proj mass <= 0
A projectile mass less than or equal to zero triggers this error. Clearly, no physical object in our world can have zero mass. Further, there is too much variation in projectiles for HGDT to make any simple assumptions about projectile mass. In response, HGDT simply terminates the simulation.

ERR: Burst disc still intact
All fuel has been consumed and the burst disc has not failed. From a physics and programming perspective this is not a problem, but it does result in a pretty boring gun. Either use a stronger fuel mix or a weaker disc.

ERR: Proj never cleared muzzle
Simply put, the projectile lodged in the barrel. Possible causes are numerous. Too low of a fuel mix. Too small of a chamber. Excessive frictional forces. Excessive barrel leakage (too much "slop" between the barrel and the projectile). An obscenely long barrel. All are possible causes. Simulation execution is terminated to avoid an infinite loop.

WRN: Proj diam > barrel bore
At first glance, one would think that a projectile being larger than the barrel bore should induce an error. That's an impossible situation, right? Well, sort of. Having a projectile larger than the bore is normal for something like an Airburst Rocket. Still, this situation is highly unusual and as such it is brought to the attention of the user in the event that it is an accident. Also, because programming logic has some issues with this situation (but it doesn't affect results noticibly for the systems in question), the projectile diameter is set equal to the barrel diameter at simulation run-time.

WRN: Barrel unnecessarily long
For a given sized reservoir, pressure, valve, and projectile combination, there exists an optimum length barrel that will result in the highest muzzle velocity. If a barrel is longer than this optimal length, the projectile will actually slow down inside the gun barrel. In such a situation, the gun would actually perform better if the barrel were shortened. The above warning is nothing more than a notice to the user that the projectile is decelerating as it clears the muzzle and that the gun would produce higher muzzle velocities with a shorter barrel.

WRN: Combustion incomplete
The projectile exited the muzzle before combustion was complete. Given the crude nature of HGDT's combustion model this warning should be taken with a grain of salt. Maybe it's happening; maybe it isn't.

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