NSL-78

Mid-day on 19 December 2019, Tim W. and sons launched NSL-78 from Cardinal Gibbons High School in Raleigh.

This flight tested a newly configured QRPlabs LightAPRS-W board. This tiny, light-weight, solar-powered transmitter can send tracking information on the usual 2m HAM band via APRS, and also transmit grid location via the 20m HAM band using the WSPR protocol.

With a future around-the-world flight in mind, NSL-78 would test the performance of this dual-band tracker on a brief medium-altitude flight. Due to strong winter jet stream winds, the flight would need to be short to prevent landing in the Atlantic Ocean. The payload would be lofted with a 350g cell filled with a lot of hydrogen gas. 2500g of neck lift should shoot the balloon up close to 7 m/s and cause the cell to burst at 20km.

Below the 350g cell hung a small square parachute; then a backup AP510 APRS tracker; then a simple 808 #16 camera with small battery.

Below that dangled a thin string and 5m of even thinner wire that began part of the long 14MHz dipole antenna; then the LightAPRS-W tracker, solar panels, and APRS antenna. Finally hung another 5m of wire as the driven element of the dipole.

Launch from the school grounds went well. Tim's gang then loaded up their van to begin the chase east to Greenville, NC.

As the payload ascended, tracking packets started to come in from both APRS trackers and the 20m WSPR tracker. The first in-flight WSPR packet was heard at 1.5km altitude. This quiet 0.01W signal was received by WSPR stations near Omaha, NE and Santa Rosa, CA.

Successfully tracked 3866km distant on 10 milliwatts of solar power!

Packet sent at 1500m altitude

Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km
2019-12-19 18:14 KM4EFW 14.097161 -17 -2 FM05 0.01 WD4ELG FM06be 109
2019-12-19 18:14 KM4EFW 14.097169 -24 -1 FM05 0.01 N4JJS FM05on 24
2019-12-19 18:14 KM4EFW 14.097105 -28 -2 FM05 0.01 KD9KHZ EN53wa 1145
2019-12-19 18:14 KM4EFW 14.097190 -25 -2 FM05 0.01 KC8JNV EN11vd 1621
2019-12-19 18:14 KM4EFW 14.097094 -24 -2 FM05 0.01 KJ6MKI CM88oi 3866

A second WSPR packet, sent at 2.7km, was received around the US. And then no more...

The 808 still-image mode camera was added to the flight at the last minute. It had only a small battery and sadly ran out of power at 8km.

The LightAPRS-W tracker sent sporadic APRS packets up to 12km altitude -- And then also fell silent.

The chase crew headed east towards the projected landing site, guided only by the backup AP510 tracker.

Burst and descent went as expected. A soft 5m/s landing in a plowed field signaled that the parachute had worked as expected.

But when the chase crew arrived, they found that balloon pieces had fouled the chute -- thankfully this provided the same drag as a working chute.

And an even bigger surprise, the solar panels and 14MHz antenna wires were GONE!

Did the long antenna wires get ripped-off below 3km during a violent ascent? Did the solar panels get stripped at 12km? Or did the transmissions fail for other reasons and the parts instead get stripped during descent?

The 808 camera was configured to take still images to conserve power, so no in-flight video exists to explain what happened.