mDACS - What caused a RRC3 early Main event...and what does Main Rate mean

[Sailfish1957]

I launched an IRIS 3 in dual deployment yesterday using the RCC3 with a drogue setting at apogee and the main set at 500. The main popped way too early (3 secs after drogue). I rand the Flight Data in mDACS and I see the drogue opening at apogee as expected; then no Main shown on the data, but a dramatic speed change at 3 seconds after the drogue (but way above 500 feet). The Main Rate is indicated at -3 in the Flight Summary stats. Anyone know why the early Main Event may have occurred at what "Main Rate" means? Drogue Rate is "Infinity". Thanks!

 

[tfish]

More info would help trouble shoot.

Did you see the entire flight? Does what you saw correspond with the flight data?
Are you using shear pins? how many what size?
How big of drogue and main chutes
Has this rocket/setup flown like this before?
Did you ground test your deployment charges?
Are there more then one flight saved on the Altimeter?
Did you download and look at how the altimeter was configured?
How many and how big are your vent holes for the ebay?
Are there vent holes in the other sections of the rocket?

post the flight and configuration details

Tony

 

[user 30299]

Can you post the RRC3's Flight Settings file (".rsf" extension), and the Flight Data file (".rff" extension).

Did you set the flight conditions through the LCD or through mDACS?

 

[tim cubbedge]

As Qfactor stated, posting your flight settings and data file would help!

 

[Sailfish1957]

Can you post the RRC3's Flight Settings file (".rsf" extension), and the Flight Data file (".rff" extension).

Did you set the flight conditions through the LCD or through mDACS?

 

[user 30299]

Thanks for posting the "rff" file.

Can you post the "rsf" file?

Did you set the conditions through the LCD or through mDACS?

 

[Sailfish1957]

I used mDACS to set up the file. It works well with the BTMM (Bluetooth). I seem to be having trouble attaching the .rsf file for this flight. The "Events" were set to deploy the Drogue at apogee; and the main at 500'. I had a proper sized vent hole(s) in the av-bay, the booster and the upper airframe. The NC was friction fit and has flown that way successfully before. The upper airframe was attached to the av-bay with three screws (not shear pins). It stayed intact. Only problem was that the Main deployed at about 3 seconds after the drogue. The flight file as you can see, does not show a "Main" event; but there is a spike shortly after the Drogue.

 

[Sailfish1957]

I changed the file suffix to .rff so that it would allow me to attach it here. CHANGE IT BACK TO .rfs !!!

 

[Banzai88]

Sounds like it could be as simple as the nose shook loose and it took a little bit for the main laundry to shake out and inflate. It happens, regardless if it 'never happened before', especially with friction fit nose cones. Humidity and temperature are notorious for wreaking havoc with friction fits.

Just as likely that it was some sort of sensor anomaly, too, that didn't record in the data. The fact that you have strange data for drogue rate and a missing event in the data seems to suggest a software/processing error. I've had it happen a few times of the years, especially with long pad times during hot and humid conditions.

Was the main ematch (or whatever you used) fired?

 

[tim cubbedge]

Not sure if RSF files can be downloaded. @Sparky can you add the rsf file extension to allowable downloads?

 

[Sailfish1957]

Sounds like it could be as simple as the nose shook loose and it took a little bit for the main laundry to shake out and inflate. It happens, regardless if it 'never happened before', especially with friction fit nose cones. Humidity and temperature are notorious for wreaking havoc with friction fits.

Just as likely that it was some sort of sensor anomaly, too, that didn't record in the data. The fact that you have strange data for drogue rate and a missing event in the data seems to suggest a software/processing error. I've had it happen a few times of the years, especially with long pad times during hot and humid conditions.

Was the main ematch (or whatever you used) fired?

Thanks for this advice. The rocket had a LONG pad time (unfortunately) as the LCO was taking his time after I armed everything. You can see that in the data file attached. The ematch went off (and the charge was correct - I do ground tests and even use a vacuum for a bench test (without the charge attached ogf course).

 

[Sailfish1957]

More info would help trouble shoot.

Did you see the entire flight? Does what you saw correspond with the flight data?
Are you using shear pins? how many what size?
How big of drogue and main chutes
Has this rocket/setup flown like this before?
Did you ground test your deployment charges?
Are there more then one flight saved on the Altimeter?
Did you download and look at how the altimeter was configured?
How many and how big are your vent holes for the ebay?
Are there vent holes in the other sections of the rocket?

post the flight and configuration details

Tony

Here are my answers....

Did you see the entire flight? YES
Does what you saw correspond with the flight data? NO REALLY AS THE DATA IS A MESS (attached)
Are you using shear pins? NO - Friction fit the NC and the booster
How big of drogue and main chutes? Drogue is 12" and Main is 36"
Has this rocket/setup flown like this before? This was a first using DD
Did you ground test your deployment charges? Yes all good.
Are there more then one flight saved on the Altimeter? Yes there are two.
Did you download and look at how the altimeter was configured? Yes. .rsf is set at Drogue at apogee; Main at 500'
How many and how big are your vent holes for the ebay? All vents are properly sized.
Are there vent holes in the other sections of the rocket? Yes

 

[Banzai88]

Occam's razor. I think it was a sensor/data record issue coupled with a nose cone shake off from the drogue event. It happens.

To tell the truth, I used to be a RRC3 fan boy, but then I started noticing some strange data occurrences that simply could not be explained. Usually didn't have any ill effects on the flight profile, but I'm a data junkie, so corrupted data annoys me.

What I learned going to other flight computers is that they're ALL prone to some sort of sensor or software related data glitch.

 

[Steve Shannon]

Could you hear the drogue charge go off at apogee?
Could you hear the main charge go off three seconds after the drogue charge?
If not, then did you hear the main charge go off at 500’?

 

[tfish]

Here are my answers....

Did you see the entire flight? YES
Does what you saw correspond with the flight data? NO REALLY AS THE DATA IS A MESS (attached)
Are you using shear pins? NO - Friction fit the NC and the booster
How big of drogue and main chutes? Drogue is 12" and Main is 36"
Has this rocket/setup flown like this before? This was a first using DD
Did you ground test your deployment charges? Yes all good.
Are there more then one flight saved on the Altimeter? Yes there are two.
Did you download and look at how the altimeter was configured? Yes. .rsf is set at Drogue at apogee; Main at 500'
How many and how big are your vent holes for the ebay? All vents are properly sized.
Are there vent holes in the other sections of the rocket? Yes

Thanks for the info..
I think you must have shook the main out right after apogee..sometimes it takes a few seconds for them to get out of the rocket and to inflate..

Not sure why your info does not show the Main firing or a change in the voltage showing it tried to fire.

Did the main charge fire?

Did you see when it fired..

The 2 spikes Alt and "Velocity" at 38 sec and 127 feet are interesting ...

Tony

 

[waltr]

From descriptions it does sound like nose came off or got loose at Drogue deployment. Then main slowly came out the inflated.
If this is true then the Main charge should have gone off at 500' (as others above have asked about).

I had this happen a few times when I started doing DD and a friction fit nose. Adding Shear pins and upping Main BP charge fixed it.

 

[mikec]

Not saying it happened here, but I have seen RRC3s behave strangely when there was a big leak into the avbay that the pressure sensor saw when the apogee charge fired, which seems to have triggered main deploy at apogee and messed up the logging.

 

[Buckeye]

Not saying it happened here, but I have seen RRC3s behave strangely when there was a big leak into the avbay that the pressure sensor saw when the apogee charge fired, which seems to have triggered main deploy at apogee and messed up the logging.

I can believe that. Look at the dramatic leak at the apogee event.

 

[Steve Shannon]

I can believe that. Look at the dramatic leak at the apogee event.

View attachment 588863

I agree there’s a pressure spike at apogee which definitely might be interpreted as having descended. Certainly it appears that the e-bay wasn’t protected against pressure from the ejection charge.
But the fact that there is another spike at a lower altitude might indicate that the main charge went off at that time. If those units on the y axis of the graph are meters, that would be very close to 500 feet.
I suspect that the nosecone simply came off as the result of a jerk from the apogee charge followed by a few seconds of flailing around in the sky. With no shear pins it’s certainly possible (or even with inadequate shear pins as I have personally experienced .)

 

[jderimig]

If the y axis is meters, then the peak at 38s is the main charge. I vote that you shook out your main at apogee.

Steve ninja'd me. Great minds think alike.

With that much leakage at both ends of your electronics bay I wouldn't be surprised if your apogee charge pressurized your main compartment a little. How much BP did you use?

 

[Sparky]

I have added rsf as an accepted extension.

 

[Steve Shannon]

If the y axis is meters, then the peak at 38s is the main charge. I vote that you shook out your main at apogee.

Steve ninja'd me. Great minds think alike.

With that much leakage at both ends of your electronics bay I wouldn't be surprised if your apogee charge pressurized your main compartment a little. How much BP did you use?

A compartment with flexible bulkplates and insufficient vents (like drumheads!) could also result in a pressure spike even without leaking, but leaking is the most likely reason.

 

[Buckeye]

The units are ft. I agree with mikec's theory and also that the main chute shook out after apogee.

 

[user 30299]

I have added rsf as an accepted extension.

Excellent!

 

[user 30299]

I changed the file suffix to .rff so that it would allow me to attach it here. CHANGE IT BACK TO .rfs !!!

The rsf file was fine. Configured just as you described.

Everyone had good explanations of what probably happened on your flight - so nothing to add.

 

[tim cubbedge]

Another question- how long was your drogue harness? I’ve seen nose cones come off at apogee if shear pins weren’t used and drogue harness too short.

 

[mundayr2]

My first experience with an RRC3 was the same. As said previously, nose cone separated at at apogee. I installed shear pins and have never had any problems since.

 

[waltr]

I did have Drogue charge pressurize EBAY and cause Main to fire ONCE. ensure ebay was sealed and never happened again. On ematch wires passing through bulk head I seal them with 'duct seal', a putty bought in the electrical dept.
The Altitude plot does show a pressure leak but probably did not fire main as this is seen to happen latter.

There are a lot of things to go wrong with DD which is a good reason to learn on a smaller cheaper rocket.
I am still in agreement that nose came loose at drogue deploy and then shook out the main.

This is still better than NO chute.