Gas Balloon Terms and Definitions

Aerostat Theory – The basic theory of balloons.  Lifting Gas is lighter than air.  If the gas is enclosed in a gas tight envelope the whole object is subject to a lifting force.  If a net is thrown over the envelope and a light gondola is attached to the net, the result in principal is a free balloon.

Altimeter – An air pressure meter that measures the static pressure of the air surrounding the balloon and displays this value as altitude over a certain reference level such as mean sea level.

Archimedes Principle – A fundamental equation which states a body immersed in a liquid becomes lighter by the weight of the liquid it replaces.  The balloon receives a lifting force of the same proportion but opposite direction to the weight of force of the air it displaces.

Appendix – A cylindrical tube made of balloon fabric attached to the bottom of the balloon envelope at its lowest point.  It is used as a filling point for the lifting gas.  It acts as a pressure relief location for expanding lifting gases to be released if over pressured.  It is also the point where the valve and deflation port lines enter the envelope.

Appendix Lines -  Ropes that run from the basket to the appendix.  They are tied off to prevent the lower portion of the envelope from being pressing into the upper half of the balloon during inflation or rapid decents or during landing. 

Ascent Force – When the carry force of a balloon is greater than the weight force being carried.  When this occurs the balloon rises.

Balanced Pressure Balloon – A gas balloon is a balanced pressure balloon when the appendix is open and the filling gas in the envelope is in pressure balance with the surrounding air.

Blow Off – The loss of lifting gas during filling as a result of over pressure of the lifting gas.  It blows off excessive gas through the appendix the gas mass decreases with the blow off through the open appendix.

Balloon Basket – A rectangular shaped container (Car or Gondola) made of wicker, rattan, metal, fabric that carries the instruments, pilots and ballast bags.  It is used to provide comfort and protection for the occupants of the balloon. 

Ballast –is usually Sand or Water that is carried during flight operations to control ascent or decent operations.  Measured precisely prior to the flight to determine total weight.  Ballast is carried in lightweight flight bags or containers.

Barograph – An aneroid barometer with plotting and recording equipment that follows the movement of the barometer during the flight.  They are mechanical or electronic.  They will track the altitude based on barometric pressure for up to 10 hours at a time.   Tracks are reported on paper or electronically depending on the unit.

Carry Force – The force a balloon has when the lifting gas in the envelope is lighter than the air it displaces.  Archimedean lifting force + weight force of the lifting gas.

Clack – A component of wood or metal valves used in gas balloons.  It is opened via a valve line.  It is held in place with springs or rubber bands.  There are two types.  A single clack (German valve) or a double clack (French valve).

Compressible – The process of gas atoms contracting and moving closer together as heat is removed from the gas.  Speed, energy and force is removed from the gas. As cooling occurs.

Contraction – The cooling of the lifting gas caused by the loss of solar radiation at sunset.  Compression of the gas results which results in the loss of lift and a change in the carry force of the balloon.

Deflation Port – A fabric tube attached at the top of the envelope used for venting the lifting gas during landing procedures.  The deflation port is sealed shut during the flight with a Velcro strap that is attached to a deflation port line that runs down to the basket through the appendix.  During landing it is opened so the lifting gas can escape causing the envelope to deflate quickly.

Diffuser – A baffling devise that is attached to the lifting gas fill line.  It helps diffuse the gas pressure of the gas being added to the envelope.  It is secured in the appendix during the inflation.

Drag Rope - A rope made of natural fiber products like coconut fiber that is carried on the balloon.  It is used during landing to orient the balloon, reduces the decent speed prior to landing due to friction on the ground.  Drag Ropes are usually about 150 feet or 50 m in length.  Drag ropes are attached to the load ring.

Emergency Locator Transmitter (ELT) – is a transmitter that is activated manual or upon impact to transmit a signal used for emergency site location so a downed aircraft can be located by search teams.

Envelope:   A synthetic fabric bag used to contain the lifting gases. 

Equilibrium - When the carry force is equal to the weight force (balloon equipment and load) in the surrounding air.  The balloon “Floats”.

Expansive – The process of gas atoms attempting to distance themselves from others in random directions.  Heat increases the expansive effects on speed, energy, and force.

Flight Bag - A container used to carry sand ballast during the flight.  Flight bags are emptied into a sand hopper or dumped overboard to cause the balloon to ascend or to stop a decent by bringing the lifting gas into equilibrium with the carry force.

Global Positioning System (GPS) – A satellite based measuring system used for navigational purposes.  It provide exact information about position, speed and time.

Inflation Bag – A container filled with sand used as weight to hold basket and envelope on the ground during inflation procedures.

Lifting Force – The lifting force is equal to the weight of the air mass that is displaced by its filling gas mass.

Lifting Gas – Any form of gas that is lighter than the surrounding atmosphere.  In ballooning the following lifting gases can be used:  Helium, Hydrogen, Ammonia, and Lighting Gas (Coal Gas).

Lighter than Air – The class of aircraft that gas and hot air balloons belong to.  The craft is filled with a gas that is lower in density than the air surrounding it.

Load Capacity -  Load capacity is determined by the volume of the gas mass X (air density – Gas Density).

Load Ring -  A ring made of wood or metal that is the connection point between the envelope load lines and the basket.

Net - A netting structure that is placed over the envelope that is used as a main suspension component of a netted gas balloon.  It is used to support the gondola or basket.  It is made of tightly woven hemp with long fibers that are very strong.

Oscillation -  The gentle rise and fall of the balloon during flight caused by the heating and cooling of the lifting gas as it moves in the atmosphere.  The balloon will rise and fall a few hundred feet in a normal pattern as the balloon seeks its pressure altitude.

Over Pressure Balloon -  A gas balloon that has a closed appendix.  This is a condition where the pressure inside the balloon is greater than the atmosphere surrounding it.  It is the third state a gas balloon can be in.  Failure to correct overpressure during a flight could result in the fabric of the envelop rupturing.

Parachute Valve – A fabric valve mechanism located on the top of modern gas balloon envelopes.  The fabric is held in place by the lifting gas and is centered over the opening in the envelope by use of centering lines.  A valve line is attached to the valve and is run down to the basket so the valve can be actuated by the pilot during the flight.  It is used to vent the lifting gas and to deflate the envelope.

Pressure Altitude – The level the gas balloon will seek based on the weight and the amount of lifting gas and effects of heating on the lifting gas.  The balloon reaches an equilibrium state and floats.

Pressure Height - The height at which the envelope becomes full of gas or under pressure and is determined by the percentage of fullness upon leaving the ground and by atmospheric conditions.  It is the point that the envelope is completely filled with gas.

Rain Curtain - A ring of fabric that is located on the bottom of a envelope that act as a rain drip edge.  It cause water running down the envelope to drip away from the basket and passengers.

Rain Fly - A clear curtain that covers the basket from the load ring down.  It is used a protection from water, dew, or rain that may be experience during flight.

Rip Panel - A rectangular flap of fabric that is opened to help deflate the envelope quickly.  It is usually operated during emergency situations and landings.

Sink Force – A condition where the weight force is greater than the carry force.  It caused the balloon to sink.

Solaring / Superheating – The effects of solar radiation on the lifting gases in the envelope.  The heat added to the gas by the solar radiation causes the gas to expand and the balloon to rise to pressure altitude.  The effects of solar radiation are reduced due to cloud cover or the setting of the sun.

Taut Balloon – An envelope filled with gas that the gas pressure at the level of the appendix opening is the same as the atmospheric pressure at the same level.  A taut balloon is characterized by a complete full envelope without wrinkles at the bottom of the envelope.  This state 1 of the 3 possible states of a gas balloon.

Transponder – An electronic device that is used by radar tracking systems to identify location, altitude, and speed of an aircraft. 

Un-taut Balloon – A gas balloon envelope that is not completely filled with a lifting gas.  The balance level moves to the lower level of the filling gas layer.  The envelope is wrinkled at the bottom near the appendix.  This is the 2^nd state of three possible states a gas balloon can be in.

Valve – A wooden or metal valve structure located at the top of the balloon envelope.  It is actuated using a valve line running from the bottom of the valve into the basket.  When opened it allows the lifting gas to escape causing the carry force of the envelope to change and start a decent.

Variometer – a mechanical or electronic instrument used to track the speed of the ascent or decent of the balloon.  Usually displayed in feet per minute.

Weight Force – The weight of the equipment, passengers being pulled downward by gravity.