RWK High Altitude Balloon Launch Wrapup – August 23rd

The August 23rd High Altitude Balloon Launch (#7!) is in the books, and it was a good one.

The balloon was launched shortly after 9am on a bright and somewhat hot Saturday morning from Old Celina Park in Celina TX, and ascended to a maximum altitude of 105,528 feet before bursting and (rapidly) descending back to the ground just north of Justin TX.

The balloon path is shown below:

The balloon payloads (shown in the table below) worked really well this time (with just a couple of problems).

The cross-band VHF->UHF repeater once again was the star of the show, with hams in all directions reporting clear communications. Johnson Space Center and Pearland to the South, Abilene and Amarillo to the West, and several stations in Arkansas to the Northeast. You can listen to the recording [here].

The HD imagery for this launch was really good for this launch and we hopefully have solved the focus problem from previous launches. The image below was taken just before the burst at 105,000 feet (32014 meters).

SSTV also performed well and we welcome your reports of SSTV images that you received.

New to this launch was a Geiger Counter that reported data through the telemetry system (data TBD) and a 20M very low power transmitter that was transmitting Horus telemetry signal. The 20M signal was coupled with the K5RWK telemetry tracker, and unfortunately that tracker GPS lost lock shortly after launch (we suspect a desense problem). This was an experiment and it wasn’t a huge surprise.

The 360 video camera again provided spectacular imagery. This is a “mini-earth” view looking straight down. You can make out several of the local lakes (Lewisville, Grapevine and Ray Roberts are in the center).

After burst (at 105,000 feet!), the balloon had a very rapid descent back to the ground, in part because the majority of the 2000g balloon was still attached, preventing the parachute from fully inflating. For past launched, the balloon mostly shredded upon burst and didn’t stay attached to the payload string. Probably because of the rapid descent, the payload string stayed intact and all the payloads were recovered within about a 3 foot circle (on the ground and not in a tree!). But it was evident that impact was about 4000 ft/min or around 40 MPH.

All the payloads were recovered, but each had some amount of impact damage (all fixable). Luckily, the payload string landed very close to I-35W in a oil/gas lease/pasture property that was behind an unlocked gate. Thanks to Kip for talking to the property representatives. All in all, it was a very quick and easy recovery (for a change).

We will be posting more images soon…

Our next scheduled launch is tentatively scheduled for October 2025.

Submit your reports for a QSL card: https://forms.gle/1A212c3TgbaKA5Ky5

Flight Goals

• Finally capture some 360° camera footage from launch to burst
• Test 20m HF 50-baud Horus Binary v2 beacon on 14.070MHz @ 10mW with dipole antenna — what does the propagation look like beyond the radio horizon? (RX is easy, just feed sideband audio to your PC. See this page.)
• Fly a Geiger counter
• Measure pressure balloon pressure delta
• Prove data aggregator concept using Pi Pico W + BLE to Raspberry Pi (small sensors to Wenet payload)

Payload	Callsign	Frequency	Participate
SSTV + Wenet / SSDV	KE5GDB	432.5MHz SSTV Robot 36 (FM) 431.5MHz Wenet 115.2kbaud	SSTV on the air – Robot 36 Wenet live images at http://ssdv.habhub.org/KE5GDB Wenet RX
Crossband Repeater	K5RWK	446.0MHz Downlink 147.435MHz + PL67.0 Uplink	On the air
Tracker – RS41 20m Experiment BMP680 Sensor	K5RWK	14.070 @ 50 baud USB 432.700 @ 100 baud USB (-1KHz dial)	On the air / track online How to decode Decode online
Tracker – RS41 Geiger Counter	K5PRK	432.600 MHz USB (-1KHz dial)	On the air / track online How to decode Decode online
Tracker – RS41 Tried and true	K5UTD	432.900 MHz USB (-1KHz dial)	On the air / track online How to decode Decode online
360 Camera		SD card	Video after launch
Environmental Sensors		SD card	Post-launch report