Balloon Project #2

On the way to school today I spotted some large-scale (big enough to hold people in the gondola) hot air balloons floating above our fair city.  This really got me excited to get to work on our project in class!  Balloon Fiesta is on its way; look to the skies in the morning to see hot air balloons in action.

Today we worked on prototypes in class.  We worked out a pattern for our design using the triangle model as can be seen as a link on Isabel's blog ( http://vimeo.com/8557013 - this is a link to the video).  The shape will have an equilateral triangle as the base (which will end up being the top of the balloon).  Using some volume formulas from our bookmarks we have determined that the base triangle will have to be about two feet minimum on each side for there to be enough volume inside the balloon to create lift.

Please look at the pictures that Isabel has posted for today's lab-work:  http://unknown-scienceclass.blogspot.com/2011/09/prototype-mockups.html

In the first two pictures you can see our tiny-scale pattern for our initial concept of the design.  This model is constructed of equilateral triangles that are of the same size.  The base triangle is two inches on each side.  The four triangles together create a larger equilateral triangle with four inches for each side.  The next picture is of our first functional prototype test subject in its not-yet-constructed form.  This design is slightly altered from the tiny-scale design in that we changed the angle of the side triangles (to 70 degrees instead of 60 degrees) and cut off the tips (so that there would be an area to put the fuel source).  We did this to increase the volume of air contained within the vessel and to increase the distance between the top of the balloon and the fuel source.  The next two pictures are of the construction process.  The final picture is from after our first attempt at checking for balloon buoyancy.  We used four candles, and preformed our experiment in the "Center of the Universe."  The inside of the vessel did get hotter than that of the atmospheric temperature.  Based on our collection of formulas (contained in our bookmarks) we believe that the reason that our balloon did not float well is because there was not enough lift for the weight of the construction materials.

As can be seen, this prototype caught fire.  We did not use alum-paper for this prototype, but this experiment shows how the alum-paper would be of benefit for our next production model.  Also finding a way to centralize the heat source would help prevent the sides of our balloon from catching fire.  We still have yet to address how to attach the fuel source to our balloon. We have put some thought into a design for this, and once we construct the proper size balloon we should be able to work on getting our fuel attached to the rest of the construction.

We'll get some images of alum's awesome fire-retardant powers up soon!