Balloon and Helium

There are two kinds of balloon that you can use:

  • Sounding balloons
  • Cold Weather balloons

Sounding balloons will typically weigh in at 200 grams to a full kilogram and lift 250 grams of payload. They will also go up to 20 – 30 km.

The cold weather balloons can carry a good kilogram and are made to go to the stratosphere (from 10 to 50 kilometers high where temperatures can be lower than -75 degrees C)

The balloon I used for MSP-1 & MSP-2 was a Kaymont Cold Weather KCI TX1200 balloon.  It cost about $105 (shipping included). I now use Hwoyee‘s 1600g balloons from Scientific Sales.

Kaymont’s balloon has a 12 cm long thick neck used to fill the balloon and attach the load lines.

When you manipulate the balloon, I highly recommend that you use latex gloves. It’s not to protect you but to prevent you from damaging the balloon with your nails and your sweat.

Remember: The balloon is very fragile. Find an area that’s very protected from the wind otherwise, it will bounce against you and the ground a lot and may be damaged before even launching it. Because it’s so fragile, you must launch it from somewhere with no possible contact with fences, trees, phone or electric lines.

How much Helium?

To fill the balloon, I highly recommend to use Helium over Hydrogen.

Hydrogen is lighter than Helium but the difference is ridiculous when you think about the risks. Hydrogen is extremely flammable whereas helium is an inert gas. Moreover Helium is easy to obtain and you do not need any special permits if you decide to start transporting several tanks of it around in your truck.

You can find helium tanks at local party stores or welding supply stores.

I found mine at SF Party in San Francisco.

One cubic foot of helium will lift about 28.2 grams. Kaymont recommends a gross lift of 3440g. So I needed 3440/28.2= 122 cf of helium. I took the 244cf tank + a dolly. It cost me $148. Be careful the tank is very heavy.

How to to fill the balloon from the Helium Tank?

Helium tanks from party stores usually come with special regulators for party balloons. It’s not the best thing in our case because the flow rate is low, you need to constantly bend the valve  and consequently it slows the filling process down.

The obvious issue is to link the small regulator’s mouth to the 3 cm wide balloon’s neck.  You need to build the joint/adaptor yourself.

You need:

To make sure the dimensions are correct, bring with you the balloon and the regulator when you go shopping. You can find the materials at Lowe’s or Home Depot.

The reason you want to a long plastic tube is to be able to inflate the balloon on a clean plastic cover away from everything.

The balloon’s neck is about 3cm (1.2 inch) wide, a 1inch wide PVC tube is large enough to keep it tight. Make sure to secure it with 2 tie wraps and a solid pair of hands.

Since the inflating process can take up to one hour, the person responsible for the balloon can get very tired. The reason you want an Elbow shape is to attach the inflating balloon to something heavy to prevent it to fly away and to measure the lift.

How much Helium is enough?

The tank regulator may or may not have a volume gauge. To measure the balloon’s lift, I found very hard to use a hanging scale. It’s great to weight your payload but absolutely not convenient to measure the lift. The scale is not accurate if there is any wind. It requires at least 2 person and tends to recalibrate itself each time you switch it on.

The best way I found was to attach the regulator joint to a jug of water. Add the desired amount of water to match the lift (3440g -> 3.5 liters). When the balloon is at equilibrium you know you have reached the desired lift.

Remember: It’s always better to have more lift that not enough. (More Lift = Faster ascent rate = Shorter flight time = Fewer problems)

About sealing the balloon, Dave Mullenix has the best instructions: using tie wraps or heavy twine, tie the balloon neck off tightly above the filling adaptor. Remove the joint. Tie the neck again, four to six inches below the first piece of twine. Tie your payload cord to the neck between these two pieces of twine. Now bend the neck over double and tie it again, twice. You will now have the neck of the balloon bent over double, with the payload suspension cord nestled in the bottom of the bend and the whole thing securely tied.

You’re ready to go over your pre flight checklist.

37 thoughts on “Balloon and Helium

  1. I learned a lot from this, thanks! It also helped me with my personal weather balloon project (currently in the drawing board stage). Keep up the nice work!

  2. I was wondering if you had any advice and safety tips on filling a ballon with hydrogen?


  3. i will send a weather balloon 1600 gr with 2500 kg weigt payload.
    is it gonna make a really big diffrence for reaching enoughf ??

  4. Hi Jack,

    Basically a bigger balloon will carry more weight or with the same payload, a bigger balloon will have more room to expend and you will go higher.
    A 1600g balloon (filled with the appropriate amount of helium) carrying a 2500g payload should be able to reach around 100,000ft.



  5. Thank you very much marc, i have one more question, does 13 inc parachute (from projectaether) can take that much weight> 2300 kg ??
    Thank you!

  6. How much helium would you advise me to use for the Hwoyee‘s 1600g balloon from Scientific Sales.

  7. How to follow altidue ( for example balloon reach 30000 meter) ?
    I have spot gps but i can only track..?
    Whats your advise?

  8. Hi Michael,
    Go to and check the required lift for a similar size. Based on the lift, you can deduct how much helium you need.
    Hope that helps.


  9. Hi Marc,
    i found this post very helpfull.
    I have another project in my mind and think of using a weather balloon to lift it in a height of 15 meters above the ground and light it from inside. The problem is that the weight of the staff i need to light it up is above 5 kg. This means that i can go with a big enough balloon, but is the 1200g enough to lift 5 kg?
    Do you have any recommendation?
    Thank you in advance!

  10. So you want to use a balloon to lift 5kg up to 15 meters?
    I am not an expert. A 1200g balloon seems small, I’d go with 1500g or bigger maybe.

  11. We live in eastern PA, and the U of Wyoming weather balloon predictor said that our project would land in the middle of the Atlantic Ocean if launched today…

    What type of weather conditions should we be looking for?


  12. Hi Mike,

    The less wind you have, the easier it will be to launch your balloon.
    Wind conditions change daily, you need to run the prediction tools often to get a general sense of where it’s going to go.
    Remember that it’s only a prediction, it will not necessarily follow the predicted flight path.
    Run them until you have trajectory that works for you and if not, be ready to travel to a better launch location.

  13. Hi marc
    Where can i buy a kaymont balloon? iam outside of US, They dont have a buy option…Before i used scientific but they sent me a cracked balloon, and we were in a very important project, so i cant buy from there..
    Thank you!!

  14. Hi Thomas,

    You need to call Kaymont to place your order.
    I have never had a problem with scientific sales. They sell different brands of high altitude balloons.
    I am sure you can find the Hwoyee brand online somewhere else

  15. Hello Marc
    Which altimeter do you advise for record the altitude of the balloon? Brand and type?
    Thank you!

  16. Hi Jack,

    To track the altitude, I have used Byonics GPS4 which is designed to work at altitudes up to 84kms.
    Whichever GPS you choose, make sure they operate above 60,000ft. (Most GPS devices do not work above 60,000ft because of ITAR regulations).
    Hope this helps.

  17. Hello again Marc..
    How can we track gps and altidue at the same time?? I mean while we tracking tHe gps, following the balloons reach altitude at the same time?? The spot gps only showz us tracking…
    Thank you very much!

  18. Hello,
    A group of students from my school are hoping to launch a weather balloon later this week (if of course all the preparations go ok) and we were wondering if you could help us and answer some questions about the set-up of everything. We are not sure how long the nylon cord has to be between the balloon and the parachute and between the parachute to payload. Also we watched a video where people used figure eight knots to tie the nylon cord. Is it the safest and strongest knot to use or are there better types of knots? We also looked at the set up of parachute and it seems that there are two ways of attaching it:×394/Weather_balloon_image.jpg and Which way would be the best to attach the parachute to the payload and balloon? Finally how are the ropes of the parachute kept from becoming entangled? Because that would cause difficulty for the parachute to open we suppose..
    We really hope you can help us as we really want this project to work and we only have one try!

  19. Thanks for your message.

    Here are my answers:
    -How long the nylon cord between the balloon and the parachute: I have tried either really close and really far with little difference. You just don’t want to rest of the balloon to be directly in contact with the parachute. So I would say 4-6 feet.
    -Between the parachute and the payload: 10 feet.
    -Knots: It doesn’t really matter. Figure 8 knots are rock climbing knots so they are easy to make and remember. Honestly my knots were terrible, double or triple them. Just make sure it’s not going anywhere. The knot should be in the neck of the balloon secured with zip-ties.
    -To attach the parachute: I have only used the first example. When the balloon burst, don’t think it’s gone, its remains are still heavy (probably at least one or two pounds) and fall under the parachute and pull on it from the top. The cord linking the parachute to the balloon tends to collapse the parachute a little bit. It’s not a huge deal. This is the dirty and easy method.
    The second method prevents that, allowing the parachute to be theoretically fully inflated (that depends of the attitude of the balloon: no spin, no unbalance – It’s pretty unpredictable). However because it’s facing upwards, it will slow the ascent, which isn’t a good thing. The slower it is, the more time it will be pushed by the winds. This is a safer but more complex method. Make a decision and don’t worry about it too much.
    -How to keep parachute lines from being entangled: Make your payload as stable as possible; Attach the cords between the payload and the parachute to the top of the payload and not the sides; You can also build a circle with holes to get the shroud lines separated. Remember that you will have little control over what happens.
    -How to retrieve it?
    Rule#1: Double or Triple your trackers. I highly recommend using a spot tracker (I would have not found any of my payloads otherwise)
    Rule#2: Make sure all trackers are activated and work from inside the payload before launching it
    Rule#3: Leave immediately towards where you think it’s going and have a laptop with 3G connection to track it live during the ascent and descent.
    Rule#4: Write your name and phone number in obnoxiously huge and BOLD. Add “reward if found”.

    I’d love to hear about your project. Feel free to contact me if you have other questions or news!
    Good luck!

  20. Hello,
    We are going to launch a weather balloon, i did it before. but i want to use diffrent systems like a transmiter and reciever with my camera for watching the same time as the balloon launching and landing on LCD screen.
    i find some sites;
    but thesee are only for 1000 meters. How can i use thesee systems with weather balloons for long distance??

  21. Hello. I plan on using an 8 ft diameter balloon. It weighs 300 g. How much will it weigh with the helium. How much helium do I need to fill an 8 ft diameter balloon to go near 100,000 ft? Thank you!

  22. Pingback: Balloon and Helium |

  23. Hi,
    is there diffrence between 2000 gr balloon vs 1200 for take 1,200 kg. kit to 11000 m.
    i feel like 1200 gr balloon better than 2000 gr.
    Whats your advise?
    thank you!

  24. Hey there,
    My friends and I will be sending a balloon up soon for a school project and I was wondering what size to get. The 1600 gram on scientific is a bit out of our price range and we are currently looking at the 600 gram and 800 gram ones. How high would these be able to get with about 2 pounds of payload?

  25. Hi Timothy,

    It really depends on the balloon characteristics provided by the manufacturer and on how much helium you use.
    You can look at the chart on Kaymont’s website to get a better idea.
    Hope this helps.

  26. Hi Marc,
    I m thinking of using a weather balloon to lift a weight of 2,5 kgrs in a height of 100 meters above the ground. I also want to keep the balloon tethered at that height with a wire. I think that the 1200g ballon (filled with 5 or 6 cubic meters of helium) is the propable for that job.
    I would like to hear your recommendation, could i propable use a smaller ballloon or it s better to try with it?
    Keep the good job,
    Thank you !

  27. Hi,

    I would like to send a load of about 600g, I have a 8ft (150G) balloon, would that be enough?

    Also, how much helium do I need to feel it up in m3?

    Thanks in advance

  28. Contact the balloon manufacturer to get details about it. I cannot guess it.
    For the rest of the math, read the article, everything is explained.

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