April 16th, 2017 – Bruin Space’s balloon program, Project Overseer, had its first flight. This flight used a styrofoam container to loft a camera, Project Reach‘s radio, and the tracking & recovery radios mentioned below.
Total payload mass was ~1200gm including the a 4qt styrofoam cooler with 1.5inch walls, and used a High Altitude Science 1200g balloon along with a Rocketman 5ft HAB parachute. We targeted 1200g of lift from Camino del Valle Park in Castaic, CA.
The plan was 2.5hr flight to 100kft, with an estimated landing near Victorville, CA. It took nearly 5 hours, went to 109kft, and went about 55 miles further east, landing inside the Marine Corp Air Ground Combat Center.
- Tracksoar v1.2 VHF APRS transmitter
- homebrew 1/2 wave dipole antenna based on VE6SBS design
- Antenna was vertically polarized to match our mobile & typical digipeter antennas. We figured the spring steel of our dipole would handle the landing fine
- Set to 89s cadence with W6YRA-11 callsign, no time slot, WIDE2-1 path
- Next time will have a slotted ~2min cadence, with dynamic pathing based on altitude along with recorded burst altitude & other features
- Powered off of 2x Energizer Lithium AA batteries
- homebrew 1/2 wave dipole antenna based on VE6SBS design
- tBeacon Amber UHF RDF beacon transceiver
- 1/4 wave wire antenna
- Powered off of 110mAh rechargeable li-po polymer battery
- Stock 60mAh battery was bloated – either due to overcharging, or from -20F freezer endurance test
- Set to 441.000 (best spot we could find on the SCRRBA 440-450 band plan that was far away from LoRa packet channel to minimize receiver desense concern)
- Responds to 1750Hz call tone by transmitting RF received signal strength with synthesized voice followed by three tones at varying power levels. Repeats a few times, then returns to a power-saving standby mode
- LoRa UHF transmitter (BSpace Reach test)
- rubber duck ant
- Picked 431.200 since it is the lowest frequency allocated to a 100kHz packet channel on the SCRRBA 420-440 band plan
- Default LoRa Bw125Cr45Sf128 modulation, +23dBm
- GoPro Hero 3+ silver
- set to 720p 30fps with 64GB SD card, allowing for ~9 hrs of video
- 3x TPS61200 boost converters
- Powered from 9x Energizer Lithium AA batteries (3s3p)
- Provides up to 1.6A max combined @ 5V
- Estimated 6 hr runtime with the GoPro
- Loosely load balanced with equal lengths of wire from the output terminals
- 8x “Hothands” 2oz handwarmers (all were taken out – read on!)
Camino del Valle Park was perfect. Quiet, picnic tables for setup, descent horizontal area in case the winds took the balloon sideways on liftoff (though there are inevitably power lines and trees in the distance)
Launch preparation (a lesson in delays)
Four things delayed out launch from the planned 10AM to just before noon:
- Late departure from campus
- Had to go to the store for rubber bands & handwarmers
- Last minute troubleshooting & reprogramming of Reach LoRa transmitter
- Had to open up payload right before launch due to overheating from handwarmers
- The Tracksoar had stopped transmitting, & the GoPro had stopped recording. It probably exceeded 50C in there, burning out one of the boost converters in the process – thankfully there was redundancy here. All handwarmers were removed, but the payload was still quite warm, but functional, when we launched. A >25C interior temperature was maintained throughout the flight.
Additionally, due some miscommunication about positive & total lift, the balloon was seriously under-filled, stretching out the flight. But hey, it allowed us to reach a higher altitude!
There were also a few “bad touches” of the balloon with ungloved hands and even bouncing onto someone’s head & hair as the wind gusted. The concern is natural oils may cause the balloon to pop early. I wonder how much further & longer the flight would have been if the balloon was truly clean.
Reach LoRa radio
BSpace’s is using a LoRa radio-on-a-chip in their Reach payload, to transmit GPS, accelerometer, gyro, pressure, and more when it is launched upon URP’s rocket at the end of the Spring Quarter 2017. Unfortunately the signal was lost well before the required distance was reached. Changing the modulation type to add more forward error correction, and substantial ground/RX improvements (QFH antenna, preamp, bandpass, tripod) are planned.
- LoRa UHF receiver + Arduino (picnic table only)
- Rubber duck
- Car #1 (Ryan NX1U, Erik)
- Subaru Forester XT aka “AWD Helium-carrying grumbly ground-looping Kenwood-mobile”
- TM-D710 for APRS & VHF simplex
- Needs APRS tablet interface
- 1/4 wave 2m/70cm dual bander on tri-mag mount
- Should have also brought 5/8 wave 2m to improve/enable post-landing APRS reception
- Should have brought portable VHF yagi
- Power & grounding issue suspected since range & voice quality wasn’t as good as expected
- TH-D72 for APRS/RDF
- Rubber duck
- UHF Arrow antenna (loaned from URP)
- Helium tank strapped down in the back, with a seat folded down (right initially, left preferred for more people)
- Car #2 (Alex, Justin KK6UPW, Daniel, Mitchell, William)
- Subaru Outback aka “AWD people carrier”
- FT-5100, Tram 1185 magmount for VHF Simplex (W6YRA)
- 12Ah AGM, powerpole bank & fused cigarette accessory
- 5100’s channel memory was not saving – probably dead CR2016 battery
- No TSQL
- Baofeng UV-3R plus Mobilelinkd to receive APRS (NX1U loan)
- Should have brought over-the-window BNC antenna mount & set up to improve reception
- Should be pre-paired with a configured Android phone/tablet for position TX too
- Car #3 (Aram KJ6YJS, Spencer NN5W, Chloe, Sam)
- Volvo S60 aka “pull over for a blown fuse ham-mobile”
- TYT Mobile hooked to Motorola Computer running YAAC for APRS; receive only
- Various HTs used for Simplex since we didn’t have a separate APRS rig as expected (Motorola HT1000, Relm RPV-7500, etc.)
- Computer crashes when vehicle restarted and when a relay box blew a fuse due to vibration induced short; need a battery backup
- PA for yelling at KK6IZF when he switched to the wrong channel on the Azden
- Car #4 (Akshaya KK6UPY, Franklin KK6IZF, Sai KM6ISQ, Avee)
- Ford Escape 4WD aka “we’re tracking a balloon – no rush. Oh crap we have to return the zipcar!”
- Azden PCS-6000 & 6m/2m/70cm magmount for simplex (W6YRA)
- Too much wind loading & too weak a magnet. Subsequently relegated to NX1U’s “desk duty” (filing cabinet really), freeing up another Tram 1185 dual bander for next time
- No TSQL
- 7Ah AGM, powerpole, fused cigarette accessory similar to Car #2
- Wouxun KG-UV899 plus Mobilelinkd for APRS
- needs a over-window or magmount upgrade, plus TX
Most cars had APRS reception, but some received better than others, so we kept each other updated over simplex as well. We got spread out after lunch, and simplex was becoming a stretch, so we should have planned for using some open repeaters.
We stopped in Palmdale for lunch, at which point we noticed how many restaurants were closed. It was Easter Sunday after all! We weren’t hunting for Easter Eggs, but what we were hunting was also brightly colored.
We relied on APRS iGates to keep an eye on the balloon as we ate. Once the last received packet became stale (15 minutes) we started getting concerned and cars #1 and #2 hit the road again to resume the chase while the rest finished their lunches and filled their gas tanks. They were able to take their time since once we we hit the road again we were still receiving packets directly. Leaving these APRS receivers on, and relaying that information to a phone/tablet over wifi/bluetooth, may be a nice convenience over relying on the cellular-internet-iGate route.
In retrospect, the stale iGate position during lunch is peculiar since the APRS.fi download after the fact doesn’t appear to have any gaps at all.
The chase went on and on, and once we got past Victorville we managed to gain some ground on it, briefly getting within 20 miles again before the roads forced us further south than we wanted we were quickly back to around 30 miles range again. This was when the balloon burst.
Download the Google Earth KMZ file including the predicted flight, APRS recorded flight, APRS chase car, and extrapolated landing zone!
As alluded to earlier, the flight started 2 hours late, and the flight time was an additional two hours longer than expected. This meant a lot of time on the road as the balloon ultimately landed 55 miles further east than we had planned.
Unfortunately it landed on a Marine base so we couldn’t recover it. We didn’t know that at the time, so we drove, as quickly as possible on some fairly rough terrain. At this point we were getting worried about sunset, and over 90 minutes of rough dirt driving predicted. There wouldn’t be daylight left for any significant ground search, let alone driving back out.
We had only got 30 minutes in when we encountered a no trespassing fencepost. Given how late in the day it was, perhaps this was fortunate in hindsight.
A couple things could have helped us – real time plotting in Google Earth, better internet connections (or offline map caches), offline prediction tools, etc.
With a topo map, some effort can be made to find a perch to listen from after burst, so we can get lower altitude or even ground packets. Last packet we, or any iGate, received was still about one mile AMSL, or ~1000′ AGL, and the last few of those showed a significant change in heading to the north/northwest as the balloon encountered ground winds. But we weren’t able to figure out any of that in the field – we need a way to feed APRS packets into Google Earth in the field, without an internet connection and aprs.fi.
After it had landed, we were only able to get within 17 miles until we had to stop. There had been no additional packets received.
We tried sending 1750Hz tones to ping the tBeacon Amber’s RDF tones. We used handhelds that were already easily configured to do this, and with some digging through the menus the TM-D710 mobile was able to do the same at a higher power level through the mag mount. We even hooked up the Arrow yagi, intended to be for RDF handheld use. Nothing. Given the distance, and the terrain, this isn’t terribly surprising.
The tBeacon Amber is advertised as 5-6 days of standby time with default settings, which we didn’t deviate far from. However, we did have to switch out to a 110mAh battery, nearly doubling the capacity & runtime to 9-10 days (although we didn’t have a chance to test that). Still, at the time of this writing it is expected that even this battery is depleted.
In retrospect, we should have done a couple tBeacon pings through the flight, just to make sure it was still working. We only did it pre-launch. No need to waste the battery and the beacon’s standby time, but one/few pings at lunch time, or maybe just after burst, would have been a good confirmation of functionality.
There are a few ideas to improve the ground reception of the Tracksoar APRS and/or tBeacon RDF:
- 5/8 wave VHF vertical
- topographic perch / listening station
- quadcopter w/ APRS digipeter, or voice cross-band, to fly up to 400′ AGL. Ultra-portable tower! At least for a few minutes…
Lessons learned & next flight
Download the APRS data spreadsheet
We have fantastic temperature, ascent rate, descent rate, and other data from this flight.
This certainly won’t be out last balloon flight! We’re hoping to pull off another one hopefully this quarter (Spring 2017). Lessons learned (better testing & preparation, earlier launch, improved ground segment radios) have largely been covered already already – with one notable exception.
We Need A Cutdown Device!
- Mike “Swiss” Bales for rush sending us a replacement Tracksoar unit when our first one began acting up, and for helping us debug.
- Barry “Slow But Sure” Sloan VE6SBS for his Tracksoar usage & modification notes, detailed balloon flight and equipment pages, and modified Tracksoar firmware, which we will be using on our next flight.
- The “29 Palms” Marine Corp Air Ground Combat Center for taking our calls and looking around for a silly lunchbox-sized payload in not the most accessible of regions.
Check out Bruin Space’s tweets