Hot air balloon – being inflated before flight

The hot air balloon was the earliest successful form of manned flight. A hot air balloon consists of a bag called the envelope that is capable of containing heated air. Suspended beneath is a gondola or wicker basket, which carries passengers and a source of heat, in most cases an open flame. The heated air inside the envelope makes it buoyant since it has a lower density than the relatively cold air outside the envelope.

For modern sport balloons the envelope is generally made from nylon fabric and the inlet of the balloon (closest to the burner flame) is made from fire resistant material such as Nomex. Beginning during the mid-1970s, balloon envelopes have been made in all kinds of shapes, such as rocket ships and the shapes of various commercial products, though the traditional shape remains popular for most non-commercial, and many commercial, applications.

Filled with hot air

Standard hot air balloons are known as Montgolfier balloons and rely solely on the buoyancy of hot air provided by the burner and contained by the envelope. This style of balloon was developed by the Montgolfier brothers, and had its first public demonstration on 4 June 1783 with an unmanned flight lasting 10 minutes, followed later that year with manned flights. The Montgolfier brothers worked through the steps in the [/Engineering%20Design%20Process Engineering Design Process] to develop their balloon.

  • Ask – Increasing the air temperature inside the envelope makes it lighter than the surrounding (ambient) air. The balloon floats because of the buoyant force exerted on it. The amount of lift (or buoyancy) provided by a hot air balloon depends primarily upon the difference between the temperature of the air inside the envelope and the temperature of the air outside the envelope. How can this idea be used for manned flight?

What are some ideas that use this method of generating lift?

  • Plan – The total weight of all the components for a 5 person balloon is (3.76 tons) 7517 pounds. The most-used size is about 100,000 cu ft (2,800 m3), and can carry 3 to 5 people. How much weight must be lifted? How big does the balloon need to be? If the balloon is spread out on the ground, how big is it?
  • Create – For most envelopes made of nylon fabric, the maximum internal temperature is limited to approximately 120 °C (250 °F). The melting point of nylon is significantly greater than this maximum operating temperature — about 230 °C (450 °F). Why does the melting point of nylon matter? Why is nylon used?
  • Improve (- Are there other materials that could be used to make hot air balloon? What are the benefits? What are the limitations of these new materials?

Engineering ideas

  • aeronaut, ambient temperature, atmosphere, ballast, buoyancy, gore, density, G.P.S., fluid, gravity, helium, hydrogen, cubic foot, displacement, pressure

Do it
Here are some challenges for you to work on…

  • build and launch a hot air balloon
  • fly the balloon flight simulator and report on your experience
  • Imagine that you have been given the opportunity to take the ultimate balloon flight. Where would you go? Who would you take with you? Why do you want to go there? What would you see? Write about your flight and why you would want to take it.
  • learn to use estimation for determining size and distance following the At Arm’s Length method. Work through the example.

Balloon Construction
Materials Needed:

  • Glue sticks, 2 small pipe cleaners, tissue paper 30 x 20 (6 sheets per team, 2 each of 3 different colors), gore pattern, and 3 paper clips. All of this is provided in the Zoon Balloon Kit ordered from Pitsco – Hot Air Balloons.
  • optional – use a blow dryer, old air popcorn popper or the Pitsco indoor launcher.

Directions:

  • Select three colors (total 6 sheets) of tissue paper.
  • Using glue sticks, generously place a 1⁄2” strip of glue along the 30” side of one sheet of tissue.
  • Glue the second sheet of the same color. Now the finished sheet should be 30 x 39 1⁄2”.
  • Place the three large sheets on top of each other being sure they match as closely as possible. Fold in half lengthways twice (hotdog fold).
  • a gore template. Place the template on the fold side of the tissue and use paperclips to hold in place.
  • Cut the oval part of the template. Do not cut on the fold side of your tissue paper or on the straight edge of your template. Remove paperclips and template.
  • Open up gores, count down three and flip the first three over and place on top of the bottom three. No two colors should be together.
  • Glue 1⁄2” long strip edge on one side of the first gore. Fold over the second gore and glue it to the first.
  • Flip gores around and fold the other side over exposing the second sheet. Glue the second and third gore together on that side. Flip the gores around and glue the third and fourth together and continue till there is one side left on the bottom.
  • Flip all of the gores over and glue the top and bottom gores together being careful not to glue any of the gores in between. Cut a round circle about the size of your hand out of the remaining tissue and glue it to one end of the envelope you just made.
  • Take the pipe cleaners and make a circle about the size of your hand and glue it inside the bottom of the balloon by making a hem and wrapping the hem around the pipe cleaner circle. Use plenty of glue as holes will keep the balloon from flying.
  • Use plenty of glue as any holes will keep the balloon from flying.
  • If you are testing inside, turn the air down to make the room cooler and the balloons will fly better.

Learn more…

  • Aeronaut: Pilot of a lighter-than air craft
  • Ambient Temperature: Temperature of the air surrounding a balloon
  • Atmosphere: Gaseous mass surrounding the earth
  • Ballast: Heavy material added to the gondola of a balloon to increase stability
  • Buoyancy: Upward force that a fluid exerts on an object less dense than itself
  • Gore: Individual panels that make up the envelope of a balloon
  • Density: Volume of a substance per unit of mass
  • G.P.S.: Global Positioning System. A navigational and positioning system developed by the U.S. Department of Defense, by which the location of a position on or above the Earth can be determined by a special receiver at that point interpreting signals received simultaneously from several of a constellation of special satellites.
  • Fluid: Substance that has no definite shape and readily yields to pressure. Particles move easily among themselves without dividing its mass.
  • Gravity: Natural force of attraction exerted by the earth upon objects in or near its surface * Helium: Colorless, odorless inert gaseous element used to provide lift for a balloon
  • Hydrogen: Colorless, highly flammable gas
  • Pressure: Force applied uniformly over a surface, measured as force per unit of area
  • Displacement: The weight or volume of a fluid or gas displaced by a floating body
  • Cubic Foot: A unit of measurement for volume. It represents an area one foot long, by one foot wide, by one foot deep.