Anatomy of a Gas Balloon

 A gas balloon is made up of several components, the envelope, a net (if it is a netted balloon), a gondola and a the various pieces of equipment used in the flight.

The envelope is a gas-tight cloth sphere, inflated with one of the normal lifting gases: Hydrogen, Helium or Ammonia.  At the top of the envelope is a valve which is used to control ascents of the balloon by allowing some of the lifting gases to escape when opened.  Some of the newest gas balloons have a parachute valve that is made out of balloon fabric.   The pressure of the lifting gas and centering lines keep the valve in place.    The pilot listens for the sound of gas flow and vibration of the parachute  lines to know how much gas has been vented. Most modern gas balloons have one or two deflation ports at the top of the envelope that are closed until the balloon is landing.  Just before landing the deflation ports are opened and the lifting gas is allowed to escape.

Appendix / Diffuser	Gas Valve	Deflation ports & valve

At the bottom of the envelope is a tube used to fill the balloon known as an appendix.  The appendix is used as a pressure relief for the  lifting gas as it expands with the heat of the day.  Many of the modern gas balloons also have a rip panel which is a rectangular cold frame with a flap to which a rope is attached.  It is pulled to help vent the lifting gas quickly to help deflate the balloon rapidly.  This helps keep the balloon from dragging during a high wind or emergency situation.

(If the balloon is netted).  It is the main suspension component over the gondola.  The net covers the envelope and contains suspension ropes which are tied to the suspension hoop of the gondola.  The net is used to spread the load evenly over the surface of the envelope.  The suspension hoop of the gondola is either made of wood or metal. 

Non Netted balloons incorporate suspension cables into the fabric of the envelope.  The suspension hoop is attached to the ropes of the net or suspension cables on a non netted balloon with toggles to form a junction between the envelope and the gondola. 

The gondola is a rectangular basket generally made up of wicker or metal or a metal frame with a fabric skin.   The basket hold the crew and is their protection during the flight.  Some examples of baskets are displayed below:

Basket size is depends on the size of the balloon and the number of people to be carried.  A basket for 4 should measure at least 4.6 ft X 4 feet and be 3.5 feet high (interior measurement).  Most baskets are rectangular not square.  Each basket is hung to the by suspension ropes.  Each side of the basket must have at least two maybe three suspension ropes.  The suspension ropes pass under the floor of the basket and are protected by wicker so they are not damaged by sharp objects or metal support channels.  Most support lines will carry at least 3100 lbs individually. 

The drag line is a rope that is attached to the load ring that is used to orient the balloon upon landing.  The drop line or drag rope when uncoiled and touching the ground, its weight and friction force make it a good ballast (approximately 60 lbs) and a partial brake that slows the balloons forward motion and orients the balloon so its deflation ports are in their proper position.  The best ropes are made from coconut fiber.  It is very strong and light.

Gas balloons use ballast that is thrown overboard to control ascent or descent operations.  Ballast can be in the form of sand or water.  The pilot will choose the amount of ballast each bag has in it base on their own preferences.  It may be 20 – 30 lbs per bag.  There are two types of sandbags used on a gas balloon.  The first is inflation bags.  These are sand bags used to keep the balloon on the ground during inflation.  They are just filled up and then placed around the basket during the time the lifting gas is being added to the balloon.  They are removed from the basket prior to liftoff.

Flight bags are sand bags carried during the flight.  They are measured using a scale to the exact weight the pilot desires.  They are added to the balloon prior to flight and an exact count is made so the amount of weight carried can be calculated.  These bags are hung outside the basket.  Some are carried in the basket and some are emptied in to a sand hopper.  A sand hopper is just a bag with a scoop in it that is used during the flight to drop sand from the aircraft.

The basket will also carry many different types of instrumentation that is used during the flight such as:

1.      Altimeter – Used to measure altitude

2.      Variometer – This is a rate of climb indicator

3.      Transponder – This equipment is used to communicate altitude and speed of travel to the flight control centers during the flight.  It helps other aircraft see the balloon in clouds, dark or near airports with an electronic signal.

4.      Barograph – Is an instrument used to record flight length and altitude during the race.  It produces a written document or electronic document of the flight altitude during at predefined time intervals.

5.      GPS – Global positioning system.  Helps track the balloon in flight to provide geographical and airspace references to the pilot.

6.   Aircraft Radio - Used to communicate with flight service and the chase crew.

6.      A list of other equipment carried is available in the  Gas Balloon Equipment List