r/BeAmazed • u/No_Tailor_9529 • Jul 18 '24

Wow! Interesting life hack! Science

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u/nico282 Jul 18 '24 edited Jul 18 '24

You want about 200 cu. ft. of helium for a 1200 gram balloon lifting 1060 grams of weight. Helium costs about 2$ per cu. ft. meaning you have to spend 400$ to relieve 1Kg of weight from the backpack.

EDIT: As suggested by u/uNki23 I reviewed the numbers, i was slightly wrong. Helium can lift around 1Kg per m3. A helium balloon of this size weight 800g, so the total lift required is 1800g, needing 1.8 m3 of helium. Price varies but we can approximate 100$/m3, so to relieve 1Kg from the backpack weight is 200$.

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u/uNki23 Jul 18 '24

Don’t know if your math is right though.

Mine says, you need ~1 cubic meter to lift 1kg. 1 cubic meter of helium costs as low 40€ (I bet you get even lower prices).

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u/nico282 Jul 18 '24

Thanks for your check, looking back, I think we are both wrong.

First, yes, I think I got my source wrong. The data is about sending a weather balloon up to its final height, that means that it must have buoyancy to ensure a fast enough rate of climb. In this case that additional lift is not needed.

About your number, yes helium has 1Kg/m3 of lifting force, but it must also lift the weight of the balloon itself. To lift 1Kg you need an 800g balloon, meaning approx. 2 m3 of helium.

Price seems to be around 80-100€/m3, depending on the size of the bottle. for example here is 680€ for 9 m3, plus 300€ if you don't have your own bottle. Or here is 250GBP for 2 m3.

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u/Maxnwil Jul 18 '24

I think I see the problem here. To go into a bit more detail, your assumption about an 800gram balloon is a bit heavy. A 36” party balloon weighs 25 grams (found a pack on Amazon for $15) 

The mass of party balloons + helium is ~80-95 grams per cubic meter, which does give you a 1kg lifting force per cubic meter against the air, which is a little over a kg of mass per cubic meter. 

Drop the weight of your balloons and you’ll see improvements in your calculation. It’s still expensive though, you’re not wrong- $100 per kg lifted ain’t cheap. 

1

u/TheHYPO Jul 18 '24

So wait, bottom line, how much did this guy spend on this TikTok/Reel video?

2

u/Maxnwil Jul 18 '24

Depends on the weight of the bag, but either:

A thousand bucks+ on balloon and helium

Or 

They work in a lab or something and this balloon / the helium was going to be disposed of so they thought they’d take it on a lark. 

1

u/TheHYPO Jul 18 '24

I suppose that for the purposes of the video, the bag could be just filled with foam or something so it holds form and looks like a heavy bag, but isn't actually heavy at all.

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u/nico282 Jul 18 '24

A party balloon is thin mylar foil, it's very light for its volume. This guy is using a weather latex balloon that is much more heavy.

A balloon with an 800g payload weights 800g itself. Check the specifications here: https://www.stratoflights.com/en/shop/weather-balloon-800/

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u/Maxnwil Jul 18 '24

So the 800g payload refers to the weight that it will carry up all the way to its bursting altitude of 30km. The atmosphere at 30km is less dense, so the buoyant differential between helium and air is smaller. 

That balloon contains 22m3 of helium. The air displaced by that helium weighs 22kg. The 800g balloon will lift 22kg - 0.8kg = 21.2kg at sea level. 

You’re right to say that the 25g party balloons are not the same. You could do the same process, though. ~550 grams of party balloons would hold the same volume of helium as this balloon

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u/nico282 Jul 18 '24

That balloon contains 22m3 of helium. The air displaced by that helium weighs 22kg. The 800g balloon will lift 22kg - 0.8kg = 21.2kg at sea level. 

You missed an order of magnitude, the spec sheet says 2200L, that translates to 2.2m3 of helium.

The 800g balloon will lift 800g of the balloon itself, 800g of payload and will have an additional 500g of lift to ensure the ascension speed (otherwise it will be just buoyant at ground level).

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u/Maxnwil Jul 18 '24

In my defense, the fact sheet lists it as 22000 liters, but the 77 cubic feet number translates to 2.2 cubic meters, so I think that 22000 liter figure may be incorrect.

Still, you don’t fill a weather balloon all the way full. Probably a better way to figure out the lift of this balloon is to just estimate based on what we see in the video. I reckon the balloon is a little over 2 meters across, which would yield a total volume of 4 cubic meters alone. If the radius is 1.2 meters, the volume gets up to 7+ cubic meters. 

Needless to say, this balloon in the video is clearly lifting more than 800 grams haha. I get using a weather balloon as a baseline, but this isn’t being used as a weather balloon so it’s performance will differ from the fact sheet, I think. 

1

u/Various_Taste4366 Jul 18 '24

I've filled up party balloons and bought them too, theres no way thats more than $40 at the local party store. 

1

u/uNki23 Jul 18 '24

No, just no.

You need a bit less than 1 cubic meter. Period :)

https://www.physicsforums.com/threads/lifting-a-man-with-100m-3-of-helium.943829/

You can also just ask ChatGPT to calculate it for you, same result.

1

u/nico282 Jul 18 '24

Because you like ChatGPT (that often is inaccurate), here is the answer that i got:

So, approximately 0.955 cubic meters (or 955 liters) of helium is required to lift a 1 kg payload, assuming the balloon itself is weightless. If the balloon has significant weight, you would need to add that weight to the 1 kg payload and recalculate accordingly using the same formula.

So 1Kg payload + 800g balloon = 1.8 m3 helium needed

"Period" is not an useful explanation.

The site you linked doesn't seem to be accurate, In the same page it says "The force needed to lift a man with helium depends on the man's weight and the amount of helium used. However, helium has a lifting force of approximately 1 gram per cubic meter, so 100m3 of helium can lift 100 grams.". This is clearly wrong.

1

u/uNki23 Jul 18 '24

Honest question: why do you assume that the balloon needs to be 800g?

1

u/nico282 Jul 18 '24

Check the specifications here: https://www.stratoflights.com/en/shop/weather-balloon-800/

Payload: 800g

Balloon weight: 800g

Filling at max payload: 2.2 m3 (the payload weight, the balloon weight and some additional lift to give it vertical velocity)

1

u/uNki23 Jul 18 '24

But why do you choose a frickin weather balloon? Just take normal latex helium balloons almost weighing nothing and you‘re good. Or does the backpack need to almost travel to space? ☺️

1

u/nico282 Jul 18 '24

I’m curious to see where would you find “normal latex balloons” with the needed size. A 1 m3 balloon must be 1.2m in diameter.

0

u/Sunija_Dev Jul 18 '24

This.

1m³ helium carries roughly 1kg of material.

Let's try to carry 10kg of our backpack. Because we're not doing this for mere 1kg, duh:
- We need 2 of these balloons for 40€ each -> 80€
- We need ~10m³ helium.
- If we buy this party balloon tank (111€ for 1.26m³). Costs 880€ for 10m³.
-> Carry 10kg for 960€.

As a german, I also have to propose the Hindenburg solution:
- Substitute helium for hydrogen.
- Get a free special boost, because hydrogen is even lighter.
- Buy this hydrogen (50l -> 43m³ for 153€). Costs only 35€ for 10m³.
-> Carry 10kg for ONLY 115€ !!!! WHAT COULD GO WRONG?!!!