RRC3 Aux Programming Questions

[csoechtig]

It's been a while since I've flown a high power two-stage rocket. I just want to double check my understanding of Aux settings on my RRC3. I’m using it for DD and air-starts. It is currently set this way:

• Aux Output Control Sequence (OCS): Event > Timer > 1-shot Comparator.
• Trigger Event: Launch.
• Aux Output: One-Shot Output.
• Aux Timer: “30” (3 seconds).
• Aux Comparator Operation: Alt.>ACVx100-Compare AGL Altitude for >ACVx100.
• Aux Comparator Value: “10” (1,000ft).

My question is about the Aux Timer… The manual says the timer starts at the trigger event. In my case, that's at LAUNCH. Once the rocket is confirmed to be at or above the Comparator value (1,000 ft), it should fire the Aux. Correct?

I’ve used an I284W and an I366R in the Booster Stage. The burn time is between 1.5-2.0 seconds. That’s why I set the timer at 3 seconds. I figured it would light the second stage about 1 or 2 second after the Booster motor burnout.

However, I evaluated a couple previous launches I have on video. It seems like the second stage is igniting about 5 or 6 seconds after launch (+/- 3 seconds after burn-out). It makes me think the timer is starting at the comparator value.




Of course, the problem with a delayed air start is that the rocket starts to arch and the second stage goes off course. I would love to hear from some more experienced 2-stage flyers to ensure I am setting the altimeter optimally. Thanks!

 

[Jee3300R]

The RRC3 detects launch once the rocket reaches the arming altitude. Default for arming alt is 300', so the timer would only start once the rocket has reached that height, which is usually 1-2 sec after liftoff. The output should fire at the timer value only if the rocket is higher than the ACV value.

 

[csoechtig]

The RRC3 detects launch once the rocket reaches the arming altitude. Default for arming alt is 300', so the timer would only start once the rocket has reached that height, which is usually 1-2 sec after liftoff. The output should fire at the timer value only if the rocket is higher than the ACV value.

That makes perfect sense. Thanks for the reply.

 

[rokit]

You can use the mDACS software to look at the details for the flight, including the time when the AUX event occurs. Compare that to the video to see if the issue is due to the settings for the flight, or maybe the sustainer motor taking time to come up to pressure (or some of both).

Mike

P.S. The RRC stores up to 15 flights, so if you've used it since those flights, you might still be able to get the data.