AlnessW
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- Oct 6, 2013
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I ground tested the surgical tubing (drogue) charges today for a new 3" MD rocket I'll be flying at BALLS, and the results weren't entirely successful. With the design I'm using, I only need to pressurize about 11" of airframe. I ran these figures through the Rimworld/NASSA calculator and it estimated .6g:
11" x 3" compartment
15 psi
3 x #2-56 nylon screws
I started out with .5g and got no separation. Upped to .75g...still nothing. The shear pins didn't even show any signs of wanting to cut.
Unless I'm mistaken, I would have thought that .75g would be plenty in a 3" airframe. Hence I'm wondering, could the issue have been with the charges themselves? I used the standard setup - surgical tubing with BP/ematch inside, and cinched closed with cable ties on each end. Upon visual inspection they seemed to have worked properly, splitting open with no leftover BP inside as far as I can tell.
The only other thought I had was that my tightly-packed chutes had muffled the charges enough to keep them from cutting the shear pins?
Heading back out to the test stand tomorrow with some bigger charges, but any theories here are welcome.
11" x 3" compartment
15 psi
3 x #2-56 nylon screws
I started out with .5g and got no separation. Upped to .75g...still nothing. The shear pins didn't even show any signs of wanting to cut.
Unless I'm mistaken, I would have thought that .75g would be plenty in a 3" airframe. Hence I'm wondering, could the issue have been with the charges themselves? I used the standard setup - surgical tubing with BP/ematch inside, and cinched closed with cable ties on each end. Upon visual inspection they seemed to have worked properly, splitting open with no leftover BP inside as far as I can tell.
The only other thought I had was that my tightly-packed chutes had muffled the charges enough to keep them from cutting the shear pins?
Heading back out to the test stand tomorrow with some bigger charges, but any theories here are welcome.