Charge Calculation

[z_wright]

So I am working on a charge calculator script for MATlab, and I am trying to get some sample data to make sure I am getting the correct data. I have seen some general information that the internal pressure should be between 8 and 15psi (depending on the diameter of the rocket). Would anyone be able to validate any of this and/or provide some samples of their black powder charge sizes?

It doesn't have to be super specific, just diameter, a rough estimate of the recovery bay, and the charge size. This would be really helpful if I could get this info, thanks everyone for your help! I appreciate it!

 

[JohnCoker]

There are many calculators online, but the one on INFO-central also includes its method:
www.info-central.org/?article=303

 

[z_wright]

I have looked at the info central page, thats actually where I started. I'm just looking for some down and dirty charge sizes so I can get a rough idea if things are working out correctly and so I can include a rough Factor Of Safety for the charge. Obviously there will still be ground testing, I'm just trying to include some real data points so it isn't all just theoretical (as from info central)

 

[Titan II]

https://www.vernk.com/EjectionChargeSizing.htm

 

[JohnCoker]

I'm just looking for some down and dirty charge sizes so I can get a rough idea if things are working out correctly and so I can include a rough Factor Of Safety for the charge.

I usually start with the charge estimated to produce 10PSI. That's generally enough, but if it doesn't open the rocket with enough authority, I'll up it 5-10% and try again.

I'm not sure it makes sense to put the "margin of safety" into the calculation since there are so many variables, but it probably does make sense to round up to the next tenth of a gram since most portable scales people have in the field aren't capable of higher resolution.