First of all, I've been lurking this forum for a while - but I've never had a reason to post because the search feature works very well Thanks goes out to all the contributors on this forum for creating such an awesome knowledge base.

This may be answered somewhere else, but when designing my own rockets it would be helpful if there was a chart available that shows the average volume displacement generated by the ejection charge for a given motor type (primary c,d,e, and f).

In the past, I just look at semroc and find rockets similar and size to what I want to design/build and copy their rocket internals (baffles, engine mounting, etc...) to insure that parachute deployment will be successful. It would be nice to know the actual volume displacement so I could design my own internals.

Thanks!

Nick

There may not be an estimated volume generated by the burning of the ejection charge, possibly the value in psi for the burn, the accuracy of which may be a little fuzzy due to the variety of variables on the motor: storage conditions, temperature, humidity and pressure. They are estimates only and I have never seen a concise collection, although I am sure that some may have contributed this in the past. I also believe that the ejection charge is more standardized by diameter of the motor (9/18/24) as opposed to the rating in Newtons - this of course for the packaged motors.

http://www.info-central.org/?article=303

There is one thing I am sure of and that would be while the volume displacement may prove an intersting piece of information it is the speed of the charge that causes the most concern. A "shotgun ejection" from a minimum diameter model will be far in excess of the charge permitted to disapate over a larger diameter and volume. Even with older designs there is an advantage to reducing the volume of the parachute compartment through the use of a stuffer tube to extend the ejection charge pressure through larger diameter and tube lengths.

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The spreadsheet on that page is very interesting and helpful! Is there anywhere that has the amount of black powder listed for the ejection charge for the various motor sizes? What is the optimum amount of force to use when ejecting a parachute and nose cone? Is there a way to estimate what it should be?