Project Horus High altitude balloon project

Horus 4

Technical information:

Launch date 16/7/2010, 12:30pm
Landing date 16/7/2010, 14:35pm
Flight duration ~ 2 hours
Launch site -35.1276, 138.8477
Landing site -34.3892,139.7034
Flight path Web, KMZ
Distance traveled 113.3 km
Maximum altitude 14,413m
Average ascent rate 3 m/s
Impact speed 3 m/s (10 km/h)
Payload weight 400g
Flight computer Arduino Duemilanove
GPS module Trimble Lassen IQ
Radio transmitter Radiometrix NTX2 25mw
Sensors Internal & external temp
Telemetry 50, 200 & 300 baud RTTY, CRC16 checksum
Tracking Ground stations (distributed listener), 1 chase car, web based tracker


Horus 4 was launched on a much smaller balloon than usual (with an expected burst altitude of ~10km), the predictions put the landing site only a short distance away.

The predicted flight path, assuming 10km burst


Weather on the ground was good, with minimal wind & some cloud cover. We only had a single chase car today, so the balloon was inflated and tied to a fence, to let us get a head start towards the landing site - after getting onto the freeway at Mt Barker our friend Paul (who was at the launch site) was good enough to cut the line and let the balloon ascend - thanks Paul!

Tied to the fence and ready to release


Our target ascent rate was 5m/s-  unfortunately our balloon fill calculations didn't correctly take such a small balloon into account and we slightly underfilled, resulting in an ascent rate of about 3m/s, which meant we'd have a bit further to drive.

As the balloon passed the prescribed altitude thresholds, the higher speed telemetry kicked in and worked flawlessly - we decoded data perfectly at both 200 baud and 300 baud, both in the car traveling at 100km/h and also back in Adelaide - 100km away. This was excellent, we'll definitely consider higher baud rates on future launches given the success with this payload.

Expected burst altitude (10km) was passed, and then some. The balloon eventually burst at 14.5km, though not before entering the jet stream and being catapulted to over 160km/h - faster than we could match in the car! This put the landing site much further out than expected, with the balloon landing near Blanchetown. Our chase was slightly hampered by the fact that we had to cross the river at a point without a bridge - this meant waiting for the ferry.

Riding the ferry over the Murray

At the time of touchdown, we were approximately 25km away from the payload, but thanks to the great conditions and flat land around us, we managed to continuing decoding telemetry until approx 140m altitude.

From there it was simply a matter of driving to the recorded coordinates & collecting the payload where it lay 200m from the road in a field - in perfect condition.

The landing site

A big thanks to everybody who helped out today, especially Adrian VK5ZSN for tracking from home & Paul for cutting the payload loose once we'd gotten a reasonable lead!