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Old 17-05-2017, 08:38 PM
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OzEclipse (Joe Cali)
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Join Date: Jun 2012
Location: Young Hilltops LGA, Australia
Posts: 1,177
Hi Sil,

The design/launch team and tracking team included some very experienced people. We had someone from the Romanian Space Agency who had launched a HAB with a one ton laboratory payload with NASA. The launch and track teams conducted 2 test flights in Romania prior to the eclipse flight. I was running an eclipse tour for 110 people at the same time and so I limited my involvement to the legal compliance aspect. In order to do that, I had to be across the broad technical aspects but not in minor details.

All problems occurred pre-launch. Helium tank was not full leaving insufficient helium to fill the balloon for a 3kg lift. No problems with device failure or cold post launch because design had taken that into account. However, with 37km expected temperatures between -60C to -90C, the payload team used Li-Po batteries and a Byonics microbeacon with GPS module. These items were rated for those very low temperatures. It's essential, from air safety perspective, that you don't lose the package tracking.

Air Services Australia (ASA) and CASA are very risk averse. This seemed to be as a result of someone sending up a balloon early that year using 2 mobile phones, one on the ground tracking the one in the balloon. Tracking failed and they lost the balloon. ASA had to shut down an 800x500km window of airspace west of Brisbane for several weeks. Consider the consequences if your parcel brings down an aircraft. I had to sign a contract which stated that I was personally liable if anything went wrong.

Below are the details of our instrument packages. The weights had to be reduced when the helium deficiency was discovered.


Balloon
Weight : is 1500 grams

Payload
Weight : is 1500 grams

The balloon will carry equipment to measure : -

Pressure sensor;
Pollution grade, UV / IR sensors;
External temperature
photos and the movie from the on-board cameras
GPS and APRS micro beacon transmitter

In the capsule we'll have a MicroTrack from Byonics, 144,850 Mhz
configurable (+/- 0,5 Mhz), we also have a GPS module also from
Byonics. We'll track the device with the APRS system with assistance from Cairns amateur radio operators in the 144,80 or 144,85 band with recording data (in APRS).


When you say Arduino, I think you mean the measurement devices? I would definitely recommend use of a purpose built micro-beacon and APRS tracking. Don't take chances with a home made device. You'll need collaborators who are licensed amateur radio operators. We found the local club were very keen to get involved and two members had their rigs in 4wd's

Condensation isn't a problem. Package is warm at launch. Most moisture is in the first 3000 m then it gets very dry up high. If cold instruments condense water on the way down, that usually isn't critical. Air pressure at 40km is around 1% of sea level so hermetically sealed instruments could crack open if the cases are not strong enough to hold one atmosphere of pressure pushing outwards.

The package had a pressure triggered parachute. It rose to 37km then burst, fell to 18km then the parachute deployed. It landed high up in a tree relative to launch, it did a big arc and was only 5-10km from the launch point. The APRS tracking path is no longer in the database. The team had no trouble finding it in the Cape York region but it was 20 metres up a gum tree. They had no alternative but to go 100km back to Laura, found someone with a chainsaw and paid him to go cut it down.

I see you are in Canberra. Happy to have a chat to you in person and can help you test your Arduino instruments at -80C to test power supplies and instruments in a vac chamber to pressure test instruments. Best not to seal instruments if possible so they can out-gas. Just needs a tiny breather hole. Also a good idea to have independent Li Po power supplies for instruments and tracking. Make sure you have enough juice for tracking.

If you subscribe to Sky and Telescope, we wrote a feature article about this that was first published in Oct 2013 in S&T and republished in Dec 2013 in Australian S&T.

Regards

Joe

Last edited by OzEclipse; 17-05-2017 at 08:52 PM.
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