Recently I had some anomalies on a launch of my 54mm MD Tomach to 15,000+ AGL @ a velocity of Mach 1.8ish. The accent was nominal however the decent appears to had some issues, which I would appreciate some insight.
There were two apparent anomalies. One was a slow decent rate from apogee. The other, my primary SL100 altimeter stopped reporting data @ 1,889 AGL or 543.55 seconds after launch detect. The rocket was recovered without issue 2.4 miles away.
There are two scenarios I was considering for the slow decent. One being high winds, which was confirmed, the other being my main deployed @ apogee, for whatever reason (electronics or failed shear pins). I am leaning towards the premature main deployment, based on the decent rate and consistency of it recorded on the altimeters.
As for the lack of altimeter data record, I have two working theories. First off I am not 100% sure if my altimeter was off when I recovered the rocket, I am pretty sure it was off when I think back. However as it was recovered 2.4 miles away close to an hour later, at the end of the day, I was more concerned about finding the rocket and just put it in the back then drove away and turned off the electronics when we got to the bar J so I am not 100%. The first theory is that there is an issue with the altimeter; the second, that there was an interruption in power. My gut tells me power, as all tests on the altimeter have come back nominally, however the wiring also checks out so its a bit of a mystery.
A bit about the rocket and altimeters: This was the rockets fourth flight and the AV bay electronics has been put through the mock deployment bench/ground tests, at least couple dozen times now. Besides working out the BP charge (1.5 g), I have never had an anomaly. The AV bay is literally keyed, so it is impossible to assemble upside down, (drogue instead of main or vice versa). The wiring is hard wired to the drogue bulkhead and keyed to a removable forward, main bulkhead. There is adequate slack in the wiring harness, in case of any movement. The battery (1S Li-Po) was fully charged @ 4.2, and just shy of 4.2 volts two weeks later. The altimeter was tuned back on post flight, same battery two weeks later, to grab the data and run tests; it ran for about 1.5 hours still reporting about 4.1 volts. The altimeters are both StratoLoggers, main (which had the anomaly) an SL100, the backup (which performed nominally) the new SLCF. Wiring is all stranded 20 gauge, with all connectors securely crimped and finished with heat shrink tubing. The terminals on the featherweight magnetic switch are soldered to the ring terminals after they are first crimped to the wires, followed by an inspection under a LED magnification lens then tested with a bench top multi-meter, which is sensitive to 1/100th of an ohm. All wiring and connections were inspected and tested post flight, and all nominal. The rocket was about 11lbs on the pad and 7-8 something on decent. I use a 12 Fruity chute classic elliptical drogue, which normally provides a 75-90/s decent rate, depending on AGL. The main is normally 25/s. The drogue is deployed when the altimeter bay, payload tube and nosecone separate from the booster via dual 1.5g charges, 1 second apart shearing 3 2/56 nylon shear pins. Main is deployed after dual charges 200' apart using 1.5g charges to separate the nosecone from the payload tube and altimeter, after shearing 3 2/56 nylon shear pins.
Attached are the two altimeter log files, Tomach SL100 Loki K830 SF Aug 29 2015.xlsx is from the main altimeter which had the anomaly. Tomach SLCF Loki K830SF Aug 29 2015.xlsx is from the backup altimeter.
View attachment 271980
View attachment 271981
There were two apparent anomalies. One was a slow decent rate from apogee. The other, my primary SL100 altimeter stopped reporting data @ 1,889 AGL or 543.55 seconds after launch detect. The rocket was recovered without issue 2.4 miles away.
There are two scenarios I was considering for the slow decent. One being high winds, which was confirmed, the other being my main deployed @ apogee, for whatever reason (electronics or failed shear pins). I am leaning towards the premature main deployment, based on the decent rate and consistency of it recorded on the altimeters.
As for the lack of altimeter data record, I have two working theories. First off I am not 100% sure if my altimeter was off when I recovered the rocket, I am pretty sure it was off when I think back. However as it was recovered 2.4 miles away close to an hour later, at the end of the day, I was more concerned about finding the rocket and just put it in the back then drove away and turned off the electronics when we got to the bar J so I am not 100%. The first theory is that there is an issue with the altimeter; the second, that there was an interruption in power. My gut tells me power, as all tests on the altimeter have come back nominally, however the wiring also checks out so its a bit of a mystery.
A bit about the rocket and altimeters: This was the rockets fourth flight and the AV bay electronics has been put through the mock deployment bench/ground tests, at least couple dozen times now. Besides working out the BP charge (1.5 g), I have never had an anomaly. The AV bay is literally keyed, so it is impossible to assemble upside down, (drogue instead of main or vice versa). The wiring is hard wired to the drogue bulkhead and keyed to a removable forward, main bulkhead. There is adequate slack in the wiring harness, in case of any movement. The battery (1S Li-Po) was fully charged @ 4.2, and just shy of 4.2 volts two weeks later. The altimeter was tuned back on post flight, same battery two weeks later, to grab the data and run tests; it ran for about 1.5 hours still reporting about 4.1 volts. The altimeters are both StratoLoggers, main (which had the anomaly) an SL100, the backup (which performed nominally) the new SLCF. Wiring is all stranded 20 gauge, with all connectors securely crimped and finished with heat shrink tubing. The terminals on the featherweight magnetic switch are soldered to the ring terminals after they are first crimped to the wires, followed by an inspection under a LED magnification lens then tested with a bench top multi-meter, which is sensitive to 1/100th of an ohm. All wiring and connections were inspected and tested post flight, and all nominal. The rocket was about 11lbs on the pad and 7-8 something on decent. I use a 12 Fruity chute classic elliptical drogue, which normally provides a 75-90/s decent rate, depending on AGL. The main is normally 25/s. The drogue is deployed when the altimeter bay, payload tube and nosecone separate from the booster via dual 1.5g charges, 1 second apart shearing 3 2/56 nylon shear pins. Main is deployed after dual charges 200' apart using 1.5g charges to separate the nosecone from the payload tube and altimeter, after shearing 3 2/56 nylon shear pins.
Attached are the two altimeter log files, Tomach SL100 Loki K830 SF Aug 29 2015.xlsx is from the main altimeter which had the anomaly. Tomach SLCF Loki K830SF Aug 29 2015.xlsx is from the backup altimeter.
View attachment 271980
View attachment 271981