BallastHalo

• To test the ballast system espcially the X-valves that we are using on the Atlantic Halo missions.
• The mission will use a latex balloon with a small vent in the neck, over time the amount of helium will decrease therefore reducing the lift, this will causes the ascent rate to decrease.
• Using the ballast system it should be possible to drop ballast to compensate for the loss of helium causing the balloon and its payload to float.
• After a period of time the ballast system will drop the remainder of its ballast which will result in more free lift and the balloon will continue to rise to burst.

• Aim is to test the feasibility of putting a vent in a latex balloon
• Will use a simple flight computer (arduino, gps, radio, cutdown) and a vent will be constructed that will be placed in the neck of the balloon once it has been inflated. The vent will have a small hole which will allow helium to slowly escape until the ascent rate decreases sufficiently to result in neutral bouyancy and the balloon floating.
• Will need to cutdown from the balloon to avoid the balloon descending slowly and causing trouble on landing. On cutdown the balloon will then rise again and burst while the payload descends
• Need to descend on a particular flight profile (such as time of day for launch etc)

• Flickr Stream

• Payload Box complete
• Cutdown finished and tested.
• Launch - 17/07/09, Churchill

• AVRmetrix - custom PCB with Atmega168, Radiometrix NTX2 and 3.3v Power supply
• Ublox RCJ-LJ GPS module (TIM-LF Chipset)
• Cutdown board - Power supply, relay, nichrome wire
• Balloon - 1500g, vent - based on WB8ELK earlier experiements 1/16th” hole
• Parachute

• Read GPS using tinyGPS library and parse the data
• Send data over radio using rjharrison's RTTY Code
• Every minute calculate ascent rate
• Cutdown logic:
  • IF payload exceed cutdown_square → cutdown
  • IF ascent_rate < 0.5m/s (sampled over 3 mins) AND altitude < 14000m → cutdown (as we don't want it floating in JS or busy air traffic
  • IF ascent_rate < -1m/s (sampled over 3 mins) AND altitude > 1000m → cutdown (don't want cutdown on the ground)

• 17/07/09
• Launched
• Ascended at 5m/s,
• Didn't achieve float
• Burst at ~35000m
• Landed near Haverhill - retrieved at night

• Telem Log
• KML file

• Note - lost telemetry during flight - went to eat hence large gap, most likely scenario is that it continued to ascend up rather then float.

• int altitude overflowed → needs to be fixed
• Need a slower ascent rate to achieve float (2-3m/s)
• Don't drop the payload out of the window

• 18/07/09 - 19/07/09, 10hrs 50min flight
• Launch pictures - simonvc Flickr
• Launch videos - simonvc youtube
• Flight was launched from Churchill at pretty much exactly 18:00GMT and ascended at a rate of 2-3m/s
• Float was achieved at ~21.15 GMT at an altitude of 27450m which was maintained for 7hrs 15mins (with a decrease of 500m)
• GPS lost lock at 22:45GMT (possibly due to being too cold) and restarted at 04:09GMT (warming by the sun)
• Balloon burst 04:12GMT and descended by parachute landing 53.085,-2.176 and was found by Laurence up a tree
• At present planning a rescue

• Telem Log Part1
• Telem Log Part2
• KML file

• Code
  • Sort out int/long/float issue with altitude
  • Increase accuracy of lat/lon
• Really need temperature sensor onboard

• http://www.sensor-networks.org/index.php?page=0827727742

Interesting flight in US: N4TXI