We always struggle a bit with the dog days of summer– its hot and humid and no one really wants to do anything. That coupled with the sinking “summer is ending soon” feeling that I always get this time of year always seems to make me cranky in august. So instead of sitting around we decided to break out some simple projects that benefit from sweltering heat- the first of which was this solar balloon.
What is a solar balloon anyway? “A solar balloon is a balloon that gains buoyancy when the air inside is heated by solar radiation, usually with the help of black or dark balloon material. The heated air inside the solar balloon expands and has lower density than the surrounding air. As such, a solar balloon is similar to a hot air balloon. Usage of solar balloons is predominantly in the toy market, although it has been proposed that they be used in the investigation of planet Mars, and some solar balloons are large enough for human flight.”
Not only is it fun to watch this guy float around, but running around like a maniac and filling it with air is good fun too. When you first fill it it will be a little wrinkly, then as it warms up in the the sun you will see it expand and start to rise which is pretty magical.
You can take things a step further by checking out artwork like 59 Steps to Be on Air by Sun Power by Argentinian artist Tomàs Saraceno. It is a set of instructions for creating a hot-air-balloon-style flying device from garbage bags that uses solar power and can actually lift a person. The artist made and tested a version himself, and provides extremely detailed instructions. He says it will take two people 24 hours to build.
Make a Solar Balloon
This balloon is not capable of lifting people but you will be able to see the science in action. It’s important to use black bags because they absorb the most heat and give your balloon its lift.
Materials:
- 3 thin plastic bags
- clear packing tape
- string
- scissors
Method:
Unfurl your garbage bags on a day that isn’t super windy. Leave one as is, and cut the bottom seam off the other two.
Lay them all out in a row and overlap the seams by about an inch so you have a long tube that is seal on one end. (The seam you didn’t cut off) Tape the bags together with the packing tape. Make sure the seams are taped all the way around and have no holes or gaps.
Now run around and fill your giant tube with air. Quickly cinch and tie the open end trapping as much air as you can.
Attach a string so you can tether the balloon to the ground and place in full sun. Watch as it heats up and the air starts to expand– eventually floating off the ground! The heat being generated inside the balloon decreases the air density of the balloon, which creates lift.
!! Important !! Don’t release your balloon (or any balloon!) When you are done, take apart and recycle your balloon or use the bags for their intended purpose.