The joy and pain of using a tracker...

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Dugway

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The UROC launch on Saturday was well attended and the weather was great, especially considering it's still March. My second launch involved a new scratch design that I worked on over the winter. I like everything about it except for one thing: the placement of the altimeter makes it impossible to use motor ejection as a backup. On top of that, in my rush to get the rocket ready to launch, I ran out of time to paint it or to GROUND TEST the ejection charges. Hoping for the best, I installed one of my 915mHz HopeRF/UP-501 based trackers and a Cesaroni J316 Pink and let it fly. A primer-white rocket against scattered white clouds made the rocket difficult to track after the violet flame ran out. Rocksim predicted an apogee of around 8,000 ft, and I lost sight of it long before then. Someone said that they saw it go over the top, but saw no ejection events. By the time I got back to my vehicle, my base station had quit getting packets from the tracker. Hmmm, not good.

A short hike in the direction I thought the rocket would probably land if it had come down under 'chute turned up nothing. Returning to my vehicle, I decided to study the tracker packets more closely. It looked like the GPS had lost its location data at launch (as usual), the radio had continued to transmit every second for 30 seconds or so, and then there were 7 packets with GPS location data immediately before the radio stopped transmitting. I figured we ought to at least see if there was anything at that location, so I entered the coordinates into my phone and my wife and I started on our 4400 ft. hike through the sage brush.

We got to within +/- a dozen yards of the location and couldn't find anything. The brush was quite thick in the area and I was getting tired of wandering around, and was ready to head back to the launch. My wife insisted that we try to get to the exact coordinates one more time, despite my phone saying that its GPS accuracy was only +/- 30 feet at the time. I got out my phone and wandered in circles for a couple more minutes until I got to as close to 0 as I could. I looked up and saw this:

crash.jpg

I don't learn things very easily some times, but maybe the loss of my tracker, altimeter, av bay, and 38mm 6-grain CTI case will help me to remember to ALWAYS GROUND TEST NEW DESIGNS. It was definitely more satisfying to find SOMETHING rather than just never knowing what happened to the rocket, but the only thing I was able to salvage was a couple swivels, even the parachute and Nomex shield were shredded. There is no way of telling if the charge fired but wasn't big enough, or if something else went wrong. As a result, this design is definitely going back to the drawing board so that I can use motor ejection as a back up. Even a VERY late ejection is preferable to this.

Further analysis of the tracker data showed that the GPS started sending location data in those final 7 packets when the rocket was about 1000' AGL. At the time it was travelling 333 mph almost straight down. The final packet was sent 100' before impact.
 
It’s bad enough to lose a $100 rocket.

But too load it up with $500 worth of electronics and lose that as well. . .

There’s just no good words for that.
 
It's tough to figure out what went wrong when all the evidence was destroyed. I know that I armed the altimeter and got the proper continuity beeps. I checked the resistance of the ejection charge before installing it and it looked good. I didn't swap out the battery from the previous flight on the Aerobee Hi so it may have been somewhat depleted after handling sustainer ignition and ejection duties. I had a fully charged LiPo sitting there but didn't take the time to swap it in. Maybe time for a checklist. I couldn't tell if the ejection charge had fired, in fact I couldn't find any remnants of the centrifuge vial at all. Everything smelled of burnt gunpowder, so it may have gone off on impact.

So going forward: always use a fresh battery on every flight, and redesign so that motor ejection is available as a backup.
 
A really tough loss.

If you only learned one thing from the flight, it was the cost of GO FEVER exceeds $500.... :facepalm:

Bob
 
A really tough loss.

If you only learned one thing from the flight, it was the cost of GO FEVER exceeds $500.... :facepalm:

Bob

Did a $359.00 loss with a converted Talon 2 on an I200. Would have been $500.00 if the guts hadn't been returned 18 months later. Altimeter, Parrot, needed a new piezo, motor casing was fine but Beeline GPS was pulverized and not present with the remains.

I thought I didn't have continuity on the pad with the Parrot altimeter and disconnected the apogee ematch to inspect. Eureka! I remembered right then that the Parrot did not give a directed continuity beep. If one match is connected properly and one isn't the same continuity sound in made as if two were connected. (Bad design) I reconnected the apogee match but missed one leg of the match in the terminal. Yeah, cataracts and I wasn't wearing the head magnifier. Got the one band continuity beep and launched. Apogee failed, main blew but shockcord broke, The main chute did not shread and still looks new after I found it and and the nosecone that apparently was sliced longitudinally by one of the fins. No packets received as I too failed to do an adequate ground test. Metallic paint, unbeknowst to me at the time, soaked up all the Rf! Lesson learned the hard way. I ground test everything now, charge/deployment sizes, running trackers with bare ematches in the altimeters for an hour dry run to make sure they don't pop or reset. Kurt
 
Sometimes, even when you've ground tested - and even flown successfully the day before - this can still happen to you. I flew my 3" Hawk Mountain Talon (which originally cost me $600 back when fiberglass was somewhat more rare - and expensive) on a Saturday to about 9000 ft and recovered it perfectly. It was a beautiful flight. Then the next day - despite full voltage and good continuity beeps from the Raven at the pad, there were no recovery deployment events of any kind, and I watched in horror as my $600 rocket, my beeline GPS and beeline beacon (two trackers worth about $350 combined) plus my $200 Contour video camera, the $200+ Raven altimeter, my $100+ parachute and my brand new (just bought the day before) 54mm L impulse CTI casing came screaming back down and dug a similar hole in the ground as yours did:

IMG_0410.jpg

The airframe had telescoped in upon itself - the 6+ foot long rocket was now less than two feet long. The altimeter, the trackers and the camera, the parachute and the motor casing were all destroyed. I never found the memory card from the camera, so I didn't even get a cool video. :-(

Here is the video from the flight the day before. Who knew she would only fly once more - and die horribly.

[video=youtube;Y0aU94OaPUY]https://www.youtube.com/watch?v=Y0aU94OaPUY[/video]
 
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So going forward: always use a fresh battery on every flight, and redesign so that motor ejection is available as a backup.
In my case, the battery was fresh. I always flew on a fully charged liPo with my Raven. There were two things I did differently on the last two flights (the successful one on Saturday and the lawn dart on Sunday) than any previous flights:

1) I flew with only 1 Raven altimeter
2) I flew with a BigRedBee beacon inside the avbay with the Raven

I can't be sure that #2 had anything to do with anything - since the Featherweight altimeter bay is actually designed to do this. I wasn't flying the Featherweight bay, it was my own design with the beacon on the opposite side of and opposite end of the sled from the altimeter. But these were the first two out of dozens of flights of this airframe where this combination was flown. I had previously flown many, many times with a single altimeter - my good old trustworthy R-DAS (original) and later R-DAS tiny. Never did I have any trouble with those. The failed flight was the second flight ever with a single Raven altimeter.

In the aftermath of this very expensive travesty, I decided that I would never again fly with this configuration. From now on, always dual altimeters with independent power sources - and no transmitters in the avbay (only in the nosecone).
 
1) I flew with only 1 Raven altimeter
You got bit by the Raven bug. I love the data the Raven provides - until it doesn't work. I've had 2 failures - beeping correctly on the pad - no deployment. One lasted 23 flights, the other failed on the 5th flight. I was able to solder on wires and pull the data the second time. It never detected liftoff. **Never fly a Raven alone**
 
You got bit by the Raven bug. I love the data the Raven provides - until it doesn't work. I've had 2 failures - beeping correctly on the pad - no deployment. One lasted 23 flights, the other failed on the 5th flight. I was able to solder on wires and pull the data the second time. It never detected liftoff. **Never fly a Raven alone**
You're not the first person I've heard say that about the Raven - but on the other hand there are many who swear by it.

I have/had flown dual-ravens a number of times in other rockets both before and since, and the trace data from both of them have always indicated flawless performance. Never did either Raven fail to detect launch, or suffer any other sort of failure. I even had a case of an e-match that shorted after firing, which caused one of my Ravens to pump a lot of current into that short for the full duration of the output pulse. Yet it did not fail.

I suspect the power was interrupted on this fateful flight. The perch was oriented with the screw terminals forward along the axis of flight. I oriented it this way because one must if one wishes to be able to run the flight simulation test in order to verify recovery performance on the ground. But in this orientation, the G-force tends to pull the battery out of the connector in the perch. It is essential to eliminate all slack between the battery body and the spacer/pivot of the battery retainer before securing the perch and retainer - so that the battery can't move at all. Failure to do so would permit the battery to disconnect from the perch during high-g acceleration. My components were placed such that the battery was a very tight fit between that pivot and the connector on the perch. It was actually difficult to insert the battery and rotate the retainer. There's no way it could become disconnected.

But I did't anticipate the possibility of that long #4 screw that holds the rotating battery retainer in place either shearing off or bending. Suppose this happened? The force of liftoff could power down the altimeter. The rocket would be just an arrow, and dutifully execute the ballistic arc I observed.

I never want to observe that again. It was horrifying. The sound of that 6 foot airframe screaming towards what I was certain would prove to be someone's house, car or head. The most sickening feeling I've ever had. I don't think I've ever been so relieved as to see it streak into an open area many yards from the nearest human.

I still fly Ravens, but I use 2 of them - and I never mount them with terminals up, always down. I always fly freshly charged batteries, and I don't put transmitters of any kind into my avbay.
 
You got bit by the Raven bug. I love the data the Raven provides - until it doesn't work. I've had 2 failures - beeping correctly on the pad - no deployment. One lasted 23 flights, the other failed on the 5th flight. I was able to solder on wires and pull the data the second time. It never detected liftoff. **Never fly a Raven alone**

Hmmmm, I attributed one main chute failure I had with an RII due to faulty programming on my part. Drogue did fine. I took the main charge, buried it so it wouldn't scare the neighbors and it blew with a 1.5V AA so it wasn't the ematch. I reset the device, had it run the flight simulation and also had both channels blow bare matches. I was "trying" to set a field elevation into the device but botched something. Never had a problem when I just set the main deployment and ignored the "field elevation". Will be trying it again sometime. I had a failure with the predecessor the Parrot that was definitely my fault. Missed a leg on the terminal with the main ematch.:facepalm: Suffice it to say the Parrot didn't give a "direct" continuity. One match could be bad and it still beeped continuity. Too bad, it is such a small package. Kurt
 
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