Make a Solar Heated Balloon




About: -Forever inventor -Want to be an Electronics Design Engineer -Windows will give you a glass of wine, but Unix will give you the rest of the bottle. To get the most drunk, you need to dual boot. :) -Je pa...

This instructable will show you how to make a hot air balloon. This balloon will not use any sort of flame to make this, though. Instead, it uses the sun to heat the balloon. I saw this at American Science & Surplus, but it was $17.50 USD, so I wanted something cheaper; I went out and made my own!

Step 1: How It Works

The black color of the trash bags makes the air inside heat up. Everyone knows that hot air rises, thus making the balloon rise.

Step 2: Materials

These are the things you need:
  • 30-Gallon Black Trash Bags
  • A large roll of duct tape (preferably black color), or a large roll of clear packaging tape
  • Scissors
  • A LARGE, dirt free environment without wind
  • Something to pump air with adequate volume (like the exhaust port of a shop vac)
  • Two or more hands
  • Free Time

Step 3: Prepare the Garbage Bags

First, take out about seven garbage bags. These will be the body of the balloon. After the bags are taken out, cut off the sealed ends of all but two of the bags. These are to extend the body of the tube, and also act as a coupler for each other garbage bag. Then, lay out four garbage bags, including one uncut garbage bag, on the large, clean surface. The surface needs to be clean, otherwise dust and dirt will prevent the tape from sticking to the bags. Finally, place the garbage bags inside one another, about 1 inch. Make sure that you place the bags inside one another so the air can travel though, without getting stuck in any crevices.

Step 4: Tape the Garbage Bags

When taping the garbage bags, make sure that the sealing edge of the bags is nearly dust and dirt free. This is because when you put the tape on, you need an air-tight seal. To start off, put tape on one side of the garbage bags, only going about 3"-4" underneath. After you do that to all the seams in the first section, flip the bags over and do it again. [See pictures 1-3]

Now onto the second section- Layout your final three garbage bags in the same fashion as the first, only take into consideration the overlapping of the seams, so the air will flow through properly when you inflate everything. Now, tape the three bags, flip them over, and repeat. Remember to go 3"-4" on the other side of the bags, otherwise they will fall apart when you try to flip them over.

Finally, it's time to tape all the bags together! Place the bag sections together, making sure they overlap. Next, tape everything together in the same fashion as the last sections.

Step 5: Inflate Everything

Now, it is time to inflate everything! First, take your handy scissors and cut a small slit into one end of the trash bags. Make this hole just big enough to blow air into using your pump (like the exhaust of a vacuum). Then, fill it up! This took me about two minutes with a shop vac. When your entire balloon becomes completely tight, seal the hole with a piece of duct tape. Also, you might want to attach a string so it won't float away!

Step 6: Have Fun!

Take the balloon out into the hot sun and try not to get this stuck 50' high in a tree! Also, try not to take this out on a windy day so it won't float away.



    • Build a Tool Contest

      Build a Tool Contest
    • Pocket Sized Contest

      Pocket Sized Contest
    • Remix Contest

      Remix Contest

    56 Discussions


    10 years ago on Introduction

    yea heh heh dont let this go near air ports ther think its a ufo or sumthing and cancelle a lot of flights and comircil airports will have it shot the airforce thinking its a threat to national security or somting like that. i know my local small air port the owner comes out with a rifle and shoots em till they come down.

    6 replies

    Reply 2 years ago

    so true unless there kids have made em before

    1- In most places in the U.S., it's illegal to discharge a weapon into the air. 2- Everywhere in the universe it's stupid to discharge a weapon into the air. Don't know why? I shot a arrow into the air it came to earth, I know not where. That's right, boyz 'n girlz, gravity. Don't be stupid like Mr. Airportowner, 'cause once you kill someone, you can't unkill them.

    Just firing a .22 caliber round can travel up to a mile, not accurately but still you could do a lot of damage if you shot your weapon into the air.


    Reply 10 years ago on Introduction

    I can see why he would shoot them down; aircraft approaching or taking off could easily get the balloon sucked into an engine, much like a bird strike. The farther up in the sky they go, the smaller the chance of an aircraft colliding with one. I wonder if there have been any weather balloon strikes on aircraft...


    7 years ago on Introduction

    My friend and I used to do this for fun. Our most successful flying design was more of a pyramid shape. I would also suggest filling them initially using a hair dryer, be careful not to melt the plastic but it really improves the lift.

    The hardest part is just getting them off the ground a ways, once they're airborne and above the trees they will be blown around and will usually take off.

    Check out our flight:

    1 reply

    3 years ago

    Made one of these when I was a kid. The only thing I'd say is; you don't need to fully inflate it. Maybe only 75% then the expanding air has some space and it should float better.

    Eye Poker

    7 years ago on Introduction

    I refer you to Charles Gas Law.


    I think this is an AWESOME idea. But I have one question, How many bags would I have to use to lift a small point and shoot camera?

    2 replies

    my guess is that on a sunny winer/fall day at least double for this design.. but their are other designs that use less tape such as a very long tube.but to be honest i wouldn't trust this with my camera i would use a couple helium filled weather or a bunch of party sized balloons.


    sorry i didnt know i was on the long tube instructable.. but if you search for solar balloons youll find a ton


    7 years ago on Introduction

    Might also try it with a surrounding bag of clear plastic. It would add weight, but it would keep the heat of the black bag from radiating.


    7 years ago on Step 6

    Hm... (regarding added weight of duct tape)...

    How 'bout adding no weight at all? Just need a heat sealer (I've purchased 'em used for $30 or so):

    1) Placing the cut bag (=tube element) inside the end bag;
    2) With edges even with each other;
    3) Use impulse sealer (=industrial heat sealer) to seal exposed ends;
    4) Roll bag assembly towards or away from you until you've sealed the whole circumference;
    5) Pull the cut bag (=tube element) out of end bag, leaving the sealed edges sticking outwards (trim them with scissors if desired);
    6) Add the next cut bag (=tube element) and repeat;
    7) Continue 'til last bag: use the end bag rather than a cut bag (tube element) stuffed into the assembled long tube, with edges aligned.

    Might be a bit rough, as the 'bite' of the impulse sealer will be more like a series of scallops as you twiddle the bag (you can't seal continuous lines longer than the unit's size, so you have to lay just that length into the sealer, then move along). But it would probably be doable. Will try and post results... in my spare time...

    Thanks for the fun idea!

    1 reply

    Reply 7 years ago on Step 6

    overlap your plastic at the seams and put wax paper on top and bottom and use an iron to heat/melt them together (practice beforehand to know best temp and speed for moving the iron to seal completely). Much lighter/smoother...give it a go!


    7 years ago on Step 6

    If you pressurize your balloon you'll lose bouyancy and risk leaks or tearing, so you want the less dense hot air pressure to be the same 'pressure as the outside air. To do that you do the weather balloon trick of starting with a partially filled balloon.
    Doing the math: Let's assume the air inside the bag is going to get 25 degrees hotter than outside. I'll measure it if I try this project, but let's just throw some numbers around. (I chose 25 for a reason: stick with me.) A change of 25 degrees F = a change of about 14 degrees C (C=F*5/9, ignoring the 32 degree fudge since it's a difference we're talking about); this is also the change in degrees Kelvin, since the C and K degrees are the same size.

    PV=nRT is the universal gas formula where P=pressure, V=volume, n=number of molecules, R=gas constant, and T=temperature in degrees Kelvin 

    P you want the same (see above); n and R don't change, so what you get is: V=fT (f being a fudge factor), so

    V1=fT1 and V2=fT2

    Solve for f:     f=V1/T1 and f=V2/T2

    Combine the two: V1/T1 = V2/T2

    Collect Volumes on one side an Temps on the other: V2/V1 = T2/T1

    Thus the percent change in volume (V2/V1) is proportional to the change in temperature (T2/T1) ...which you knew: hotter = bigger

    But what is the percent change in temp? Thus, if T goes up by 25 degrees F = 14 degrees Kelvin (from the wild guess, above), it's going from about 300K to 314K, or a change of about 5%. (This assumes that it is 80 degrees outside.)

    So, if one UNDERFILLS the bag by five percent, it will inflate completely and to neutral pressure when it warms to 105 degrees F.

    To do this one would measure the bag length in inches and multiply that by 0.05, and roll up that length of plastic at the end and put some books or a board on it, fill to desired plumpness, seal, then remove the weight and let the bag slump a bit. For a ten-foot-long balloon that would come to six inches rolled up before inflating.

    I think. It's 3:41 AM...