This is a library collection of information useful to those flying or seeking to fly High Altitude Balloons, original text from's Amateur Ballooning Compendium.

Regulations and Laws


To Be Solved

  • Need to find more information about predicting flight paths for long duration flights. - how should successive forecasts be blended together?

Experiments Performed

Preflight Preparations

FAA Coordination

File a NOTAM (Notice to Airmen) between 12 and 72 hours before planned launch. Call your local FSS (Flight Service Station) at 1-800-WX-BRIEF, and ask for the phone number to file NOTAMs.

NOTAM FILING NUMBER 2010: 877-487-6867

  • See section 6-1-10, Unmanned Free Balloons

While not required, it is adviseable to call ATC (Air Traffic Control) at your local major airport is recommended 1 hour before launch, at launch, when crossing 60,000 ft going up and down, and when landed. You may also want to call the regional ARTCC (Air Route Traffic Control Center) which controls all the airspace outside and above

Bowman (LOU) Tower: 502-479-3173
Standiford (SDF) Tracon Operations: 502-375-7440
Indianapolis Center ARTCC Operations Manager on duty: 317-247-2242

When filing the NOTAM, the FAA is looking for the following info: Launch location Nearest public-use airport to launch location Nearest VORTAC VOR, Direction of travel Rate of ascent Expected peak/cruising altitude (if ⇐60,000 feet) Time to expected peak/cruising altitude, or time to 60,000 if going higher

Sample NOTAM:


In this example, it is for an “Unmanned Free Balloon”, DKX is the ID for Knoxville Downtown Island Home airport, VXV is the nearest VORTAC VOR, 019004 represents the radial and the distance, 019 being the radial (000-359 degrees) and 004 the distance (in nautical miles). SE BND is the direction of travel (South East Bound), Reaching Flight Level (FL) 350, or 35000 feet, then the time/date of launch (03 APR 02:00) in UTC, to the time that the payload is expected to reach FL350 (03 APR 02:45).

To further clarify the VORTAC info, in the above example, VXV is the Volunteer VOR, located to the Southwest of Island Home Airport (DKX). From the VOR, DKX is located at a radial of 019 degrees with relation to North, and 4 nautical miles away.

NOTE: NOTAM formatting and information may change depending on the purpose of the balloon flight.

Position Reporting to FAA

Chadwick APRS-ATC Balloon Position Reporter

This is a highly useful tool, albeit one that requires the national APRS amateur iGate network be used. Balloon Position Report Page for ATC Russ Chadwick at NOAA in Boulder, CO, maintains a web page that will provide Air Traffic Control with position reports of your balloon flight in a format that they like best. The balloon position is provided as a triangulated reference to two known aviation navigational beacons, known as VORs. You must contact Russ several days before each flight to have the particular flight entered into the list of trackable flights. Each mission must have a unique identifier callsign (not the ham callsign), such as EOSS114 or UX18.

To Add a local VOR navigation beacon for your local ATC, start more than 1 WEEK ahead of your flight:

Contact your local ATC and see what VORs they would like you to use for your position reports to them

Go to and get the Latitude, Longitude, and Magnetic Declination for the VORs

Email Russ Chadwick russ(at) to politely ask for the VORs to be added.

To Add a flight, start at least 3 days before launch:

Email Russ Chadwick russ(at) with the Flight callsign (not ham callsign, see above), Ham Callsign, Launch Date, Launch Time, and phone number to be reached at during flight.

Flight Path Prediction

BallTrack by Bill Brown, Balloon Track by EOSS' Rick von Glahn, and LiftWin by Hank Riley are the standard tools for this. Much more information is available at EOSS's Balloon Software page

To predict the path of a balloon flight, you will first need to predict the vertical travel of the balloon using LiftWin. This will give you the vertical climb rate, and also the burst altitude. Use these values to enter into Balloon Track.

; Weather Data Sites for use with Balloon Track : NOAA ARL READY Instructions for use:

  1. Type in nearby 3-letter airport code where is says ICAO or WMO ID: or search for a nearby city.
  2. Click the Sounding pulldown menu
  3. Choose one of the NAM or GFS models that covers the shortest window of time between now and your launch site. I.E. if you launch on Saturday, and it's now Wednesday, the 0-84 hour model will be more accurate than the 0-180 hour forecast.
  4. Click Go
  5. Set Output to Text only and enter the security code given on screen
  6. Click Get Profile
  7. Select all the text in the large table onscreen and select Copy from the Edit menu.
  8. Open a text editor and paste into an empty text file, saving it as a .txt file.

Lift Gas


Hydrogen (H)

Hydrogen provides more lift per unit volume than helium, however it is less often used due to it's flammability. Hydrogen is much cheaper than Helium, and also is easily produced chemically.

=Hydrogen Safety= : A balloon filled with pure hydrogen will burn quickly, however a balloon filled with a mixture of air(oxygen) and hydrogen will explode violently. Make sure the balloon has no air inside before inflating. Electrostatic discharges can ignite hydrogen, so care must be taken to eliminate the possibility of static sparks. All equipment and persons near the balloon should be grounded, and conductive gloves should be worn by the balloon handlers. Conductive “ESD Safe” gloves and other static safety materials are available from companies such as

Helium (He)

Helium is found in natural gas or petroleum deposits, and is commonly pumped out of wells similar to Natural Gas wells. Helium is not practical to produce commercially or experimentally. Once released into the outside air it will rise to the top of the planetary atmosphere and be blown away into space by the solar wind. So, while safe and convenient right now, Helium is a precious resource that should be conserved.


SizeCapacity10% OverfillRatingWeigh
S 108ft³ 120ft³ 1800psi 70lbs
S 123ft³ 135ft³ 2015psi 70lbs
K 200ft³ 217ft³ 2015psi 140lbs
KH 219ft³ 244ft³ 2265psi 140lbs
T 265ft³ 291ft³ 2400psi 160lbs

Gases such as Helium and Hydrogen are available in the US in several commonly sized cylinders. These are usually available from local gas suppliers or welding suppliers, who will usually charge you a deposit to “rent” the tank for a defined time period. Ask if you need to leave a certain amount of pressure in the tank when you return it, they sometimes may charge you extra if you bring it back with zero pressure (The tank can be contaminated if it is allowed to equalize with atmospheric pressure).

Tanks identification markings maybe found stamped into the “shoulder” of the tank. The pressure that the tank is rated for usually follows DOT3A expressed as 4 digits in PSI. The last hydro test date is usually a month/year date, and a plus and/or a star after the date. The plus tells you the tank is rated for a 10 percent overfill. The star means the tank is good for 10 years instead of 5 years before it needs hydro testing again. (Ferriman 2001)

Pressurized Gas Cylinder Safety

The cylinders require special handling, though no special permit or license is required for transport or use. The cylinder must not be transported in the passenger compartment of an enclosed vehicle, i.e. you need to have it in a truck bed or trailer, not in your car/SUV trunk or back seat. Due to the high amount of energy stored as a compressed gas, the cylinder presents a powerful pressure blast hazard in the event of an accident or rupture. Injuries from deafness, lung rupture, and death are possible when high pressure gas cylinders undergo rapid decompression inside an enclosed passenger compartment.

  • It is recommended to always use a regulator
  • Avoid using the tank valve to control the flow/pressure of gas
  • Do not move the tank without it's protective cap screwed on completely
  • Do not leave unsecured tank standing vertically unattended.
  • Always open/close valves/regulators slowly
  • Never allow gas hoses to knot or kink - watch carefully during gas flow
  • Never use a non-flammable gas regulator for hydrogen

Cylinders are to be transported vertically when possible, securely strapped/chained to the vehicle/trailer. Must not be transported in the passenger compartment or trunk of a vehicle.


Use a non-flammable gas regulator for helium. Use a flammable gas regulator for hydrogen. The regulator will use a reverse-thread nut to screw into the tank - LEFTY TIGHTY - RIGHTY LOOSEY. The regulator control knob is also a reverse control - Left (counterclockwise) reduces the pressure output/flow, Right (clockwise) increases the pressure output/flow.

Gas Usage

  1. Hook all plumbing up to the regulator output before connecting regulator to tank
  2. Make sure the regulator is screwed into the tank tightly
  3. Close the flow control knob on the regulator
  4. VERY SLOWLY open up the tank valve, watch for pressure to rise on the regulator supply gauge
  5. Open flow control knob slowly to establish the desired flow rate.
  6. Pay attention to the balloon, do not let it flap in the gas stream.

Flight Operations



HYSPLIT - for long range predictions


The High Altitude Environment

Air Pressure and Temperature

Atmospheric air pressure decreases as altitude increases, caused by the weight of air above the measuring point. While there will be minor variations due to local barometric pressure changes, there is a standard pressure and temperature known for each altitude. The standard reference is called the “1976 Standard Atmosphere.” This is available in online table or converter format at the Digital Dutch Atmosphere Calculator. A highly useful resource, this allows you to calculate the temperature or pressure for any altitude, in several common measurement units. Some example pressures: (kPa = kiloPascals)

Altitude Absolute Pres Pres rel to sea level Temperature 0 ft 101.3 kPa 0 kpa 15 C 18000 ft 50.6 kPa -50.7 kPa -20 C 35000 ft 23.8 kPa -77.5 kPa -54 C 70000 ft 4.4 kPa -96.9 kPa -55 C

Live Weather Information

Weather education

Materials Performance In Low Temperatures

The harsh environment at high altitudes usually is far out of the normal approved operating temperature range for electronics and equipment. Low air pressure is not usually much of a problem for electronics. Due to the low temperature, batteries will suffer premature voltage drop, crystal oscillators will slow down, and mechanical lubrication will harden. CMOS and CCD imaging sensor performance, however, will improve as temperature goes down. Their improvement will be seen as less visual noise and artifacts from the image sensor. Insulating containers and heaters can be used to keep electronics warm, however sometimes you will have to locate devices that can just take the cold.

Materials Performance Research

Balloon Physics

Bouyancy/Gas Calculations

Most of these calculations require extensive chemistry experience and close attention to detail. We will endeavour to provide unit converters and computation tools to simplify these calculations. Try to keep units all in metric if possible.

Reference Constants

R = 0.0820574 (L*atm)/(mol*K) Universal Gas Constant aHe = 0.034148 (atm*L^2)/(mol^2) Van der Waals attractive force for Helium aH = 0.24436 (atm*L^2)/(mol^2) Van der Waals attractive force for Hydrogen bHe = 0.0238 L/mol Van der Waals molar particle volume for Helium bH = 0.02661 L/mol Van der Waals molar particle volume for Hydrogen

Lift Force (Bouyancy Force)

Fb = (Dair - Dgas) * V * g Fb = Bouyant force in units N/m^3 Dair = Density of ambient air in units Kg/m^3 Dgas = Density of the lift gas in units Kg/m^3 V = Volume of lift gas in units m^3 g = Force of gravity in units m/s^2

Ascent Rate


For computations of volume, ambient pressure and temperature affect the outcome greatly. The Ideal Gas law, PV = nRT P = Pressure V = Volume n = Number of moles of gas R = Universal gas constant T = Temperature should not be used in most real situations, as it refers only to gases at standard temperature and pressure. The Ideal Gas law also leaves out some fine details concerning the diameter of the gas molecules themselves.

The Van der Waals equation takes all of these effects into account, and should be used when making calculations in the real world. (P+an^2/V^2)(V-nb) = nrt P = Pressure a = attraction constant for chosen gas n = number of moles of gas v = Volume of gas b = molar volume constant for chosen gas r = universal gas constant t = temperature of gas However, the Van der Waals equation is not easy to solve for volume, and it must usually be performed several times iteratively until the correct answer is acheived.


Density = Mass / Volume

(This will look right when we get TexVc installed):

<math>rho = frac{m}{V}</math>

Balloon Envelopes


There are several categories of balloon envelopes used in balloons.

  • Sounding
  • Zero-pressure
  • Super-pressure


Sounding balloons are made of natural latex rubber, are the simple to use, inexpensive and are the classic “weather balloons”. These balloons are designed by the manufacturer to burst naturally at a pre-determined altitude. Latex sounding balloons will burst when their differential pressure (pressure inside the balloon - air pressure outside the balloon) is greater than the *differential burst pressure*, usually given by the manufacturer. Available from Kaymont Consolidated, they come in a moderate variety of sizes and design purposes. While the manufacturers usually give a recommended payload size, far greater payloads can normally be carried by these balloons. Overweighting the balloons lowers their burst altitude due to the need for more helium, thus higher balloon pressure, at launch.

Balloon Electronics

The electronics on a balloon flight serve several basic purposes:

  • Track and find the balloon
  • Capture information about the trip (pictures, environmental conditions)
  • Remotely control events on the flight from afar



Servo current draws 300ma max when stalled or under external force, 4ma stationary with no external force, and 40 ma moving without load. PWM values in PBP for pulseout were 300 to 1200, with pulse spacing of 15, using a 20MHz clock oscillator.


A GPS provides very useful information on a balloon flight, such as Altitude, Location, Speed, Heading, and Time. Some models will not correctly report altitude above 65,000 ft or 32,000 ft. However, while above their cutoff altitude, they generally continue to report correct information for location, speed, heading, etc.


Most GPS units output data in a standard format, called NMEA 0183 which is ASCII text over a serial connection, with agreed-upon serial settings. Most modern GPS models allow you to change these settings.

NMEA 0183 serial connection : 4800 baud, 8 data bits, NO parity, 1 stop bit
5v TTL level signal

The actual text data that the GPS sends is in a form called called NMEA Sentences.

Pressure Altimeter

Pressure altimeters allow you to track the actual change in air pressure as you climb or descend. This should give a more reliable indication of altitude changes, though quantitative determination of actual altitude is not particularly accurate. May be useful in precise measurement of climb rate or altitude holding systems. Most sensors read in the mV range, which requires a fair bit of external circuitry to read into a microcontroller. Recently several manufacturers have developed models that will give an analog indication from 0 - 5v. Some are available with direct digital indications. Sensors are available in several physical configurations: Differential, Gage, Vacuum, and Absolute. Absolute is the one that will measure altitude easiest. The desired range for a sensor would be from .4 kPa to 102 kpa. That will cover the range of 120,000 ft down to sea level. For holding altitude, a sensor with more limited range may be used that covers the desired pressure altitude. Pressure altitudes are available from the Standard 1976 Atmosphere.

Possible Absolute Pressure Sensors, 5V powered, single pressure port:

Freescale: MPXV5100A 15-115 kPa, MPXA4101AC6U 15-102 kPa, MPXAZ6115AP 15-115 kPa (side port)

Honeywell: ASDX015A24R-DO class 0-100psi, digital I2C hex output


TypesCapacity (mAh)VoltageWeight (g)
Energizer e2 Lithium AA 3000 1.5 14.5
Energizer Alkaline AA 2850 1.5 23

Lithium L91 Battery Handbook

Due to the extreme cold temperatures encountered, and importance of saving weight, currently Lithium batteries are the best single-use choice for balloon flights. Lithium batteries perform well down to -40C, are lighter than other types, and hold more power. Rechargeable battery technologies generally have poor cold performance, however a chart of rechargeable battery performance information is available at Battery University has a great deal of information on battery technologies, and is recommended reading.


Generally Energizer e2 Lithium cells are available from Sam's Club and other major retailers. There are AA battery holders that will hold from 2 to 12 cells in series. This affords you a wide range of voltages. If you can find the holders with the 9V-style snap on connector on the top, this makes changing out the whole pack easier.

Always use fresh batteries for mission critical items, and always tape the batteries into the holder.


Radios provide the critical live location, and sometimes telemetry data for ground stations tracking the balloon. Balloons typically use lightweight amateur radio HTs or homebuilt transmitters. Power consumption and weight are primary concerns in selecting a transmitter for a flight. VHF/UHF bands are good for their high bandwidth data capabilities, but they become woefully inadequate when the balloon falls to the ground, usually beyond your VHF radio horizon. In these curcumstances, it is advantageous to use HF radios.


The 2 Meter band has many inexpensive, lightweight radios available, and there is an existing nationwide network of APRS iGates on 144.390 MHz to relay data to the internet. This is the most commonly used band and frequency for balloon tracking. The line-of-sight VHF radio horizon is over 300 miles at 100,000ft altitude, allowing much greater propagation than VHF normally can be used for. = Recommended Models =

Kenwood TH-D7A(G) : 2M/440 HT with built-in TNC, This is the only radio we've found that has all radio and TNC features controllable via ASCII serial commands. This allows you to change frequencies or power levels during the flight from onboard microcontrollers or computers. Controlling the TH-D7 via it's serial interface
Byonics PocketTracker : This little kit radio/tnc has had mixed reviews. While small and lightweight, lasting for weeks on one 9V lithium battery, it hsa problems when it gets cold. For what it costs (~120USD) and was designed to do, it is acceptable. It is not recommended for use as a primary location tracker, on balloon flights due to extreme cold sensitivity. When it gets below about -10C it's frequency and baud rate drift, causing it to send undecipherable packets. This radio has been discontinued by the manufacturer

Most HF radios on balloons are hand-built designs, found in magazines or online. Power output is usually 1 watt or less, putting these transmitters in the QRP category. The capabilities are usually very simple, commonly CW (morse code) on a single crystal controlled frequency. Less commonly, PSK31 on HF has also been flown. Many are built by, or based on designs by Carl Lyster, WA4ADG. HF reception must often be made by people very far from the balloon due to the skip zone in propagation. For this reason, HF beacon telemetry often includes a web site or email address where listeners can post the telemetry that they copied down.



Whip : 1/4 wave whip antennas work well, especially when augmented with ground plane radials. Vertical polarity is preferred due to payload rotation about the vertical axis.


Dipole : UTARC and other balloon groups have tested and regularly rely on simple vertical dipole antennas. The transmitter is located in a payload box, with one leg of the dipole extending up the support rope, and the other leg of the dipole dangling below. 26 Gage wire has been used with success in these installations, however it is recommended to put a small weight on the lower end of the antenna. While this works very well in the air, there has been concern over it's operation on landing. UTARC has found that when the payload lands in a tree, the dipole usually maintains enough separation to radiate well. When a payload lands on flat ground, and crumples the antenna around the payload, the dipole performance is somewhat unknown. UTARC has not tested the performance of this configuration, and looks to others to provide any info on their experiences here.

Radio Data Transmission

Common data transmission formats/modes:

APRS : Uses Packet Radio AX.25 packets to relay location, altitude, and telemetry using a standard format. Can be automatically received by iGates to servers and internet maps such as Findu and APRSWorld
  * Common Ballooning APRS Settings (Don't use these for ground-based APRS work!):
    * Callsign suffix:  -11  e.g., AA4UT-11
    * Path: WIDE1-1,WIDE2-2
    * UNPROTO string: APRS
    * Balloon Symbol: O (capital o)
    * Symbol Table/Overlay: /
    * Beacon Interval: ~21 seconds

CW (Morse Code) : This method is probably the best for low-power/long distance needs. Especially good for post-landing position reports via HF.
PSK31 : This HF mode is also good for low signal levels, however there are not as many people equipped to receive such a signal as CW.

PSKReporter : collects and maps heard call signs on PSK31… could it be modified to report ALL heard PSK31 data and upload to central server? Alot of hams already run Ham Radio Deluxe or fldigi, if they already work in digital modes, so to get people switched to our modified software should be easy (replace dll perhaps?)

RTTY or Radioteletype : This HF mode requires a very stable HF transmitter, but is simple to implement, merely by shifting the transmite frequency 160hz back and forth. UTARC has found this mode to be easy to implement, moderately high data rate, and surprisingly reliable given current computer decoding programs.
ATV (Amateur Radio Television) : Live NTSC standard television signals are possible, with video image overlays of callsigns, telemetry and location data.
SSTV (Slow-Scan Television) : Taking dozens of seconds to 2 minutes to relay each photo frame, and not having much small hardware available, this method is not often used on balloons.
Voice : Digital audio recordings can be played back and individual phrases, letters, and numbers can be played in order to communicate the live telemetry and location data.


Math Calculations

Serial Communications

RealTerm for Windows, is the free swiss army knife of terminal programs - you should always have this handy! Primary useful features are capture serial data to text file or network port, playback of data file to serial port, I2C device, interfacing, serial port pin state debugger lights, and lots more.

MTTTY for Windows, (not to be confused with MMTTY, a good RTTY radio data modem program) is a free, very full featured serial com port terminal program.

RS-232 Serial Links Reference is a great web site for understanding serial communications and has links to good software for development.

Radio Data Communications

MMTTY for Windows, (not to be confused with MTTTY, a good RS-232 Serial terminal program) is very good, and free, RTTY modem software.

CocoaModem for Mac OSX, is very good, and free RTTY modem software.

Decoding GPS Information


Miscellaneous Useful Information

VOR VXV Lat 35.9048386111111 Lon -83.8947263888889

Automated balloon launch system prototype

compendium.txt · Last modified: 2011/04/01 19:24 by steamfire
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