38mm Go Devil part 2

[charrington]

Hey all,

Yesterday I launched my 38mm Go Devil at Tripoli San Diego. This is the same rocket from my level 2 cert with a few modifications done with the goal of breaking mach 2. I am about to take off back to Sacramento international airport so I will give a flight report later tonight! This was a pretty cool flight and experience to say the least.

See you all then,

Cameron Harrington

 

[charrington]

This story starts off with my good buddy from college going for his Level 3 certification flight. We always fly together and I obviously wanted to be there for his L3 cert flight to be of assistance. The only issue is that I live and work in the bay area now while he is down in San Diego. Originally I was planning on driving down after work the day before the launch but after thinking about it I knew it would be a bad idea to make that drive so late at night. I got a plane ticket and then got my gear together. I had Wildman ship an Aerotech J825R to his house. My significant other was very hesitant about letting me borrow her suitcase but after a quick chat with airline staff, they had no problem accepting this.



For anyone interested in traveling onboard a plane with rocket gear, here is what I did:
1. Make 100% sure that you are not carrying any pryotechnic material - absolutely no e-matches, propellant, black powder/pyrodex, etc.
2. Make sure you aren't carrying any compressed gases such as CO2.
3. Clean off BP residue from all parts to the best of your ability
4. Store tools, and pointy objects inside checked bag
5. Make 100% sure that any batteries are in your personal bag or carry on and NOT your checked bag.
6. I told the attendant at the checked bag receiving area that there was model rocket kit inside but contained no hazardous materials.
7. I am TSA precheck and while I cannot confirm this helps, I believe it does as my bag had not even been opened and searched during my round trip.

 

[charrington]

I left work Friday and had my partner drop me off at the airport.

California is exceptionally green after all the rain we received this year.

Once landed at San Diego International, my buddy picked me up then we headed back to his place and got a few things ready. His launch obviously took priority and at this point neither myself or him knew how we were going to integrate the recovery system into my go devil. At this point I had launched my Go Devil once for my L2 cert (https://www.rocketryforum.com/threads/first-attempt-at-a-38mm-minimum-diameter-launch.175806/). In the previous configuration I did a standard dual deploy configuration with an AV bay in the middle and a tracker in the nosecone. To hit Mach 2 I needed to get rid of the AV bay and upper airframe and store all electronics inside the nosecone. This meant that I was going to attempt to use Tinder rocketry's piranha line cutters to do a drogue-less dual deploy. At this point I never have used line cutters which was my first mistake of 3. ALWAYS ground test before flight! For electronics, I planned on using a stratologger CF and Featherweight GPS for my recovery.

Going to bed the night before the launch, I knew just about what this OpenRocket file showed which was very little. The mission objective was this: Get there early in the AM, Launch and recover my buddy's L3 and then build my recovery system using whatever materials were available.

 

[charrington]

The day of the launch we headed out to Tripoli San Diego. I have really been enjoying this site. Do yourself a favor and take a trip out there if you are in the socal area. The drive from San Diego city is super beautiful too.

My buddy launched his L3 and it was a success! Loved watching it go up and Ill post some photos once I get them back.

After we recovered the rocket it was time to configure the recovery and this is what we came up with (Pictures taken after the launch because we were racing to get this thing on the pad.)



This is a *modified* egg timer Nosecone sled from Labrat rocketry. I drilled and carved out the spots that were used to mount eggtimers to be able to fit the stratologger and featherweight along with two batteries.



The stratologger was mounted with the channels facing towards the inside so that the baro unit was facing outwards. It was secured with electrical tape with the battery of the raven mounted below it. The batteries were on the opposite side of their respective devices. This is just how they liked to be orientated and overall ended up with a nice fit.



Here is the side with the featherweight tracker and batter for the stratologger. These were retained with frog tape and electrical tape.



I used a 1.5ml microcentrifuge tube as my charge well. First time using this method. Drilled a small hole into the bottom of the tube and fed my ematch wire through it. Added some dog barf and then taped it up nice and good. will definitely be using this method again. Extremely convenient.



Here is the configuration for the piranha cutter with rocketman high cd chute. As you can see it did not shear because I messed up on assembling the system lol. Always ground test! This was mistake 1.

 

[charrington]

Here she is on the pad:

If you look at the cone you can see the vent hole for both the altimeter and letting the wire through for arming the altimeter. I know it's not aerodynamic but its the best I could do with getting this done the day of the launch. This is where mistake number 2 was made BUT my buddy caught it before I launched. I taped down the wires and covered the vent hole with the tape lol. Defeats the purpose of a vent hole duh. Anyways, I removed the tape and just let it fly as it.

 

[charrington]

The moment we all have been waiting for...

Here is the Launch video:



Not a good photo by any stretch of the imagination but check out this flame to rocket ratio!



GPS was locked out while rocket was above Mach 1.5 and then regained tracking once it went below this threshold. It landed pretty close by and took about 10 minutes to get to.



Mistake number 3: I forgot to put masking tape around the base of the motor tube which allowed it to become loose during flight and unscrew from the minimum diameter retainer that retained it. Here is the crazy part tho. IF you remember mistake number 1, I didnt ground test my piranha cutters and ended up messing it up so it didnt deploy. The drogueless rocket was falling at about 80-100fps as intended from apogee. It got below 1k ft and was still falling at this speed so I was completely ready for a core sample. All of this is monitored in flight with the raven gps. Right before it hit the ground the motor tube came loose and fell out which SLOWED the decent rate to 30-40fps. The motor case and the airframe were found about 40ft apart, both completely undamaged. I can't believe how lucky I was. The Piranha did ignite but I failed to assemble it correctly if anyone was wondering. I followed the old instructions when I have the new model.


Here is the raven tracking data. The apogee almost perfectly matches the simulation. I have the stratologger data that I need to analyze too though I am confident that Mach 2 was broken from the simulated data and recorded data.

The next day I headed back to the airport for a 7am flight and landed in Sacramento, ready for work on monday!

 

[charrington]

Data:

According to the Featherweight GPS my max altitude was 13,691ft.

Here is the stratologger data:


I do not believe that I hit 3500 ft/s (Mach 3.1). I do believe that I was somewhere around the 2500ft/s area seen on the graph which actually matches my sim speed exactly (Mach 2.22). If anyone has any info on this discrepancy let me know. I know baro readings can get wonky at high speeds.

All in all an amazing day with amazing people. Thanks again to Tripoli San Diego for hosting an amazing launch day with excellent waiver!

Next launch...



See y'all in Colorado.

 

[OverTheTop]

Altimeter vent being near the nc probably caused some deviation in measured vs actual pressures.

 

[plugger]

That's Stratologger CF data, which is Baro only, which would lend credence to OTT's comment about the NC vent. Also, I'm assuming that when you say Raven you're meaning Featherweight GPS? As from your eBay photo upthread that what I think I'm seeing.

 

[charrington]

That's Stratologger CF data, which is Baro only, which would lend credence to OTT's comment about the NC vent. Also, I'm assuming that when you say Raven you're meaning Featherweight GPS? As from your eBay photo upthread that what I think I'm seeing.

Ah yes I meant featherweight GPS, not raven. Ill edit that now.