Bryan, sure, it could just be that. But, I could still barely see the
rocket at apogee, and I don't think the drogue came out. Other people
with better eyes were still able to track it a bit after that, and one
of the spotters said he saw a flash (like an impact) on or in the
direction of a point on the hillside. He gave me a very specific
direction to walk in, using the "A" launch rods as a guide. But, who
knows. At that distance it's really hard to judge how far something
really went, or where it came down.
I drove around the back side of the lakebed for quite a while after all
the launching was done and never picked up any signal. If it just
drifted and thus the GPS was OK (and it had a big enough battery to last
8+ hours) then I should have picked something up. That's why I expect
it got damaged somehow.
Terry
On 7/21/2019 10:45 PM, Bryan Langholz wrote:
Terry, I’m just wondering if you’ve talked yourself into a worse case scenario. Is it possible that just the tracker failed and that you lost sight of the rocket? In the wind it could have drifted pretty far.
On Jul 21, 2019, at 10:21 PM, Terry McKiernan <terry@xxxxxxxxxxxxx <mailto:terry@xxxxxxxxxxxxx>> wrote:
>> Did you get any position info from your GPS tracker?
Well, here's a case where I took a bad situation and made it worse.
The T3 GPS receiver (i.e. the part attached to my phone, for tracking) was getting telemetry for a few seconds after launch, then stopped. I didn't count the seconds to when it stopped but I think the rocket was past apogee but still in the air. I think it just got out of range. The rocket did not come off the rail very straight and while it climbed pretty high, it was tailing away from the launch area to the northwest. The projected apogee from OpenRocket was over 5000 feet and since it was going more parabolic I can see where it would exceed the T3 range. But, that's OK -- with just the direction of travel I figured I would just walk towards it and pick up the signal once I got close enough.
This is where I screwed up. Me and my brother-in-law set off across the lakebed, and after about 15 minutes (about 1 mile) we still had not picked up any signal. Here comes the blunder. I have seen a failure mode in the T3 receiver (or perhaps in my phone or Bluetooth GPS) where the Bluetooth connection to the HC-06 module on the T3 drops out and so even though Bluetooth GPS says it's connected, it's not getting any data. So I tapped Stop to drop the connection, then Connect. No NMEA data stream so I restarted the T3 receiver to see if it might pair up again. Nothing doing there so in desperation I restarted my phone too.
Notice the missing step? :) I didn't write down the last-known-good position before the disconnect/reconnect and the restart. It was just brain lock, or sunstroke, or something. In my mind the failure mode was one of connection between receiver and phone, when in reality it was more likely the transmitter was damaged. So I lost the last-known-good data. This was entirely my fault. Now, I am almost certain it was still in the air when the data stream stopped, so I would not have had the landing position, but it might have helped.
In retrospect also I regret one design choice for this rocket. For the T3 GPS you can get either a wire whip antenna or an RPSMA connector to mount the antenna of your choice. I went with RPSMA so I could put on a big antenna, maybe even an amplifier. In this case I used a 5 dBi antenna that's about 18 inches long; I put it up in the upper fuselage section with an RPSMA connector in the payload bay bulkplate and a cable to the T3 inside the payload section. This worked great in at-home testing but has a fatal flaw. In the case of a crash especially nose-first the antenna may get snapped off. With no antenna the effective range of the T3 drops to about 50 feet (I've tested this); not surprising since it would just be the tiny RPSMA female pin transmitting into free space. I suspect this is part of what happened -- something gone wrong in the recovery system, lawn dart into the lakebed, antennna damaged and thus T3 effectively rendered useless. I expect that the T3 itself survived; electronics boards are remarkably tough and I had it "floating" in the bay with some padding and strain relief on the battery connections, so it could take a really hard jolt if needed. But, the antenna outside the bay would not have fared so well.
I think I'll get another T3 since I've been happy with it, but either I'll get the wire whip antenna, or stick with RPSMA but use an antenna small enough to fit within the payload bay. I'll lose a little range but prevent this failure mode.
In hindsight however I should never have flown. When I first took this rocket out to the pad, despite many tests at home, there was a problem with the WiFi switch flaking out / dropping connections, and with continuity to the drogue ejection charge. I took it off the rail back to my table, took it apart, found a loose connection, rewired, retested (all good) and then tried to fly. I should have just stopped and taken it home for more thorough diagnostics. After all if there was one bad connection maybe something more systemic was wrong. But, I just really wanted to fly it since the idea was then to pull out the electronics and use them in my L3 cert kit, still under construction.
Also in highsight this was not a very good rocket! The only other time it flew was my L2 cert, and it went up about 2500 feet and then arced over, landing about 1.5 miles to the south of the launch pad. The deployment all worked but it was not a pretty flight. So that's 2 flights, neither of them very straight. I think one problem is that with this kit you have a long skinny rocket but relatively small fins at the bottom. With the light minimum diameter fuselage the weight is concentrated at the bottom so the stability calibers (or calipers :) ... sorry) is not high to begin with. I had added 2 camera bays (down and side-facing) on the outside, but I think I put them up too high. The added drag moved the center of pressure up and thus reduced stability further. I compensated with a nose weight and the extra payload section (made it longer to move up the CG) but that also made it more prone to flex ... it just wasn't a very stable rocket. I regret ever getting this kit!
<whining mode = on>
Not a very good 2 months for me in terms of rocketry. In June my canopy was destroyed by wind (I got a better one to replace it, with some super heavy tent stakes to hold it down better), and also I had an LOC Precision 3" Black Brant get ruined when, after landing, it was dragged by the wind across the lakebed for over a mile, losing 2 fins and the camera. This month I lost my green rocket with all the electronics, and for good measure the motor retainer in my White Wolf did not hold and so I lost its CTI motor casing. All told about $1000 in lost rockets and equipment, even before the cost of the motors for the unsuccessful flights. Ugh.
<whining mode = off>
Oh well.
Terry
On 7/21/2019 2:06 PM, Mike Riss (Redacted sender rockt_dude for DMARC) wrote:On Sunday, July 21, 2019, 8:35:49 AM PDT, Terry McKiernan <terry@xxxxxxxxxxxxx> wrote:
Furthermore the GPS failed (perhaps on impact) and despite spending a few hours driving around the lakebed
after the launching was done, my son and I never found the rocket.
Terry,
Sorry to hear about your rocket. Did you get any position info from your GPS tracker? If so, what was the last reported position, and what time during the flight did it correspond to (on the way up, somewhere around apogee, or on the way down).
Thanks,
Mike
