HiBall-8

3/4/2006 - Falkville, AL

Joint project of ES-OS and WB8ELK

300 cubic foot ES-OS cylinder balloon (25 feet long)

HiBall-8
Callsign WB8ELK-12
Balloon Type ES-OS 300 cu ft zero-P (1.32lb)
Flight Train wgt 3.31 lbs
Payload weight 1.56 lbs
Ballast 1.0 lbs sugar cubes
Helium 166 cu. ft.
Nozzle Lift 8.9 lbs
Frequency 144.39 MHz APRS
Radio Alinco DJ-S11T
APRS Opentracker OT-1x
GPS Garmin GPS-18 LVC
Batteries

8 AA lithiums for Opentracker and GPS

3 AA's in Alinco

- Eveready L91

Downrange 178.79 miles
Flight Time 3hr 4min

This was our first flight test of the trans-Atlantic zero-pressure balloon built by Mark Caviezel NG0X from ES-OS. The ballast consisted of 1 pound of sugar cubes in a rubber mesh (same kind as refrigerator liners). The concept is that after the balloon descends at night into the ocean, the sugar cubes suspended 100 feet below the payload will dissolve allowing the balloon to ascend again. 50 feet higher up the line was a styrofoam ring designed as a backup float to keep the payload out of the water until solar heating at sunrise caused the balloon to fly again in case the sugar cubes weren't enough for lift off. Concern about high surface winds caused us to pump way too much helium into the balloon causing a wild gyrating flight until the balloon expanded to full volume. The flight train was laid out for a high wind launch, but the wind died out completely at balloon release causing it to snatch the payload backwards from my hands (causing a nice rope burn - my gloves won't be forgotten next time) and finally took off after dragging the flight train across the yard.

 

Internal view showing the Garmin GPS-18 LVC. Transmitter was an Alinco DJ-S11T with wire dipole soldered directly to the radio's RF output to replace the normal "dummy-load" stock antenna. The APRS board was an Opentracker. The box is a recycled Ozonesonde container. (All photos by Beth Oleska).

Bill WB8ELK holding the APRS payload just prior to liftoff.

Launch of the balloon (a plastic drop cloth was used to protect it in the wind as it was brought out of the barn). L to R: Barry N4MSJ (extreme left), Thad WB4VHF, Jason KG4WSV (behind balloon), Gary N4TXI and Jim WA8VWY.

Shortly after launch. An excess of helium caused the balloon to fold over and flop about during the first 17,000 feet of ascent.

The payload landed in the parking lot of Flint Technical College in Thomaston, GA. A group of extremely inebriated folks returning from the drag races noticed a big ole trash bag flopping around in the parking lot and went to investigate and called me asking "How much is that Reee-ward?"....they finally returned it with thanks for the beer money Reward. Other than the big hunting knife gash in the side where they tried to open it up, it's in good shape and ready to fly again.

Plot of altitude and ascent rate (plotted by Ralph W0RPK).

Closeup of the brief 5-minute float at 36,500 feet (plot by Ralph W0RPK)

Analysis of the flight dynamics by Mark Caviezel NG0X:

The balloon likely reached full inflation near 18k
feet, and with less drag, it shot upward, pressurizing
the balloon. The data shows an inflection in the
ascent rate about 17k feet.

With adequate venting, we should have seen a 44k foot
float altitude, but instead we got a short float at
36k feet, with a definite bounce and a 300 foot per
minute descent.

The aggressive ascent rate starts tapering at 30k feet
on the way up, neutral buoyancy achieved 12 minutes
later at 36k feet, then a bounce, then decent.

I hypothesize:
a). Full inflation reached near 18k feet
b). balloon was pressurized and started venting
helium above 18k feet.
c). The balloon vent was too small to handle the fast
ascent and eventually popped at a point along the
cylinder of the balloon near 30k feet. Increased
venting occurred from 30k feet on up to 36k feet.
d). as neutral buoyancy occurred at 36k feet, solar
heating expanded helium in the balloon. Due to
differences in the molecular structure of helium
versus air, the helium was supercooled somewhat during
the fast ascent. The subsequent expansion of the cool
helium by sunlight and convective interchange with the
air at 36k feet caused the slight bounce.
e). as decent starts, the helium bubble shrinks,
causing a sessation in helium loss at the popping
point. A near constant descent rate entails with
near constant negative free lift.
f). decrease in descent rate could be caused by air
entrainment and subsquent solaring, making the balloon
into a helium-air solar balloon. The slight decrease
in negative free lift may have caused the slowing of
the descent rate.

the above is caused by: TOO DARN MUCH HELIUM!