Aerotech Delay Adjustment

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UhClem said:
What makes you think that the delay burns at atmospheric pressure in the motor?
...
Because of the small burning surface the pressure rise will be small but it will not be zero and it will vary with throat diameter.
Click to expand...
David,

You may be on the right track, but I think the pressure would have to be around 50 to 100 PSI to account for a 2:1 difference in burn rate.

I don't know much about the composition of the delay element, but I think it is similar to the APCP propellant. It contains some additional chemicals to keep it burning at low pressures. The burn rate is proportional to the pressure raised to the power of the "burn rate exponent".

I suspect that people that know the real answer to the question about burn rates are not commenting because it may get into an "Ex" discussion.

Dave
 
bobkrech said:
CTI Pro38 motors were the first to be certified with adjustable delays. These certifications were performed by CAR. After that AT announced that shortening delays by drilling was acceptable, and AMW then started manufacturing very long delay that begged for shortening.


Bob
Click to expand...
Bob,

The Pro 38's were first certified by TMT before CAR had a motor committee. Each delay setting had to be certified which made for a very large test matrix. The original ProDAT tool was intended to be infinitely variable but TMT insisted on discrete settings for whatever reasons.
Once CAR formed a motor test committee, we invited Jack Kane from NAR to participate in a joint certification session for the Pro54's. These used an infinitely adjustable delay. The test results from a matrix of settings were analyzed and found to be accurate regardless of the setting on the tool and were accepted by both organizations.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
 
Anthony Cesaroni said:
Bob,

The Pro 38's were first certified by TMT before CAR had a motor committee. Each delay setting had to be certified which made for a very large test matrix. The original ProDAT tool was intended to be infinitely variable but TMT insisted on discrete settings for whatever reasons.
Once CAR formed a motor test committee, we invited Jack Kane from NAR to participate in a joint certification session for the Pro54's. These used an infinitely adjustable delay. The test results from a matrix of settings were analyzed and found to be accurate regardless of the setting on the tool and were accepted by both organizations.

Anthony J. Cesaroni
President/CEO
Cesaroni Technology/Cesaroni Aerospace
https://www.cesaronitech.com/
(941) 360-3100 x101 Sarasota
(905) 887-2370 x222 Toronto
Click to expand...
Doh! Must have been before I joined S&T.

I do remember when Jack went to that joint session and also reviewed CAR motor certification procedures. Shortly thereafter S&T voted to accept a reciprocity agreement on cross NAR-CAR certifications.

Definately agree that CTI adjustable delays were throughly tested and were found to be very accurate and reproducible.

Bob
 
I flew a rocket yesterday with a G64 reload and an HDK-22 delay element. I drilled out 0.05" from the delay element to shorten the delay slightly. The altimeter data shows that the ejection charge went off at 14 seconds into the flight. The G64 has a 2-second burn time, so this would make the delay 12 seconds after the burnout.

Based on the published NAR data the expected delay would be
16.6 - 0.05/0.018 = 13.8

Based on the published Aerotech data the expected delay would be
14.4 - 0.05/0.021 = 12.0

So for this particular flight the results matched the delay predicted by the published Aerotech data.
 

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