From LVL1
Revision as of 14:15, 24 August 2010 by Steamfire (talk | contribs)
Jump to navigation Jump to search

Long Duration Balloon Project Known Constraints

These are major factors which must be considered when designing/selecting the mission hardware/software or making logistical choices.


GPS model selected (not the actual unit) must be previously flight proven - some GPS models stop functioning at high altitudes to prevent use as missile guidance.


  • Night time ambient air temperatures will usually be around -50C
  • Good lightweight insulation is required for the batteries to maintain voltage output
  • All electronics should be tested to -60C to avoid having to insulate them (that's more weight)
  • May want to create crystal ovens for oscillators
  • Wire heaters (a few high watt resistors) into battery packs, determine temperature threshold by cryotesting batteries
  • Temperature sensors are recommended for outside air, electronics, and battery pack.


Available power is constrained by weight. The power should be budgeted, and frequently negotiated as electronic components are reviewed. Power system other than optimal batteries must outperform the equivalent weight of optimal batteries over 72 hours of predicted actual flight conditions.


  • Battery choice should be made based on three factors, high capacity, low weight, and low temperature operation. This pretty much leaves Energizer e2 lithium batteries.
  • Likely about 2-3lbs of the electronics box will be available for battery weight. Minimizing the weight of the insulated payload container will increase this.
  • Some battery power MUST be reserved for emergency heating of the battery stack.


Northern hemisphere winter will be the flight conditions

  • low sun angle in winter
  • flight to high latitudes up to 60 degrees is possible
  • good for longer flights

Flight Path

  • Jet stream must be targeted, float between roughly 30,000 ft and 40,000 ft
  • Ballast should be dropped to maintain altitude within the jet stream
  • Plan consumables for for 72 hour flight


  • File NOTAMs 24 hours in advance with 1-800-WXBRIEF
  • Notify local ATC (SDF and Indianapolis Center) 1 week in advance, several hours in advance, and at moment of launch
  • Do not transport helium tanks in passenger vehicle compartments. If it must occur, open all windows.
  • Ensure all flights have high descent drag to slow impact speed (parachute or large plastic balloon envelope)



Detailed rules explained at Edge of Space Society Important constraints:

  • 12lbs total maximum weight
  • No individual payload container may weigh more than 6lbs
  • No Ham shortwave HF telemetry over USA (FCC regulation, not FAA)



  • Optimal launch time: Just after sunset. This optimizes for maximum flight time. The idea is to launch as far before sunrise as possible. Reaching float altitude in the dark allows the helium to be densest when it overflows out the vent. Then at dawn, the sun heats the helium and it expands, with some flowing out of the vent, maintaining altitude.
  • Try to select a launch time that that does not let the flight path cross major metropolitan cities, such as Washington, D.C. or New York City.

Site Conditions

  • Clear of obstructions taller than 50 feet and powerlines for at least 100 yards downwind
  • Clear of obstructions taller than 10 feet at least 50 yards downwind
  • Some paved surface is recommended for ease of setting out tarps and tools and rolling heavy tanks around.
  • absolutely no sharp objects or corners in/on the ground for 100 feet from anywhere the balloon will be while laying on the ground, or while tethered to a ground handler.
  • Site should be available for 3 hours before and 3 hours after planned launch time. (most launches do not happen on time, and involve a bit of DIY fixing that delays things)
  • Accessible closely by pickup truck - helium T cylinders are over 100lbs

Site Location

  • Recommend that site should not be within controlled airspace classes B, C or D.
  • Recommend that site should not allow common flight paths to pass into controlled airspace classes B, C or D. These airspaces extend up to 10,000ft MSL.
  • Recommend to inquire with local ATC for where approach/departure paths for high traffic runways are, and avoid flight through these corridors as well.

Site Weather

  • Low wind required at time of launch - safe maximum 5MPH, technical maximum 10MPH. Higher than this are likely to damage balloon or injure people holding balloon.
  • Clear sky - for airplane safety, balloon should not enter clouds
  • Temperature - Any is acceptable, however ensure that the balloon envelope is inflated and remains at outside air temperature if any lift force measurement is to be performed. (do not inflate in a heated hangar, and check lift force in there) When the Jet Stream is ready for balloon insertion, it will be one of the coldest nights of the year.
  • Barometric pressure - Any.