Balloon size and total weight for 10L of helium

[HOLGATES HERE]

I'm going to struggle to get the college to fund 20 litres of helium, but can put my persuasive hat on and get a delivery of 10L.  

What kind of balloon size and total weight are we realistically looking at?  We need to launch and collect on the same day, so a short flight time is fine (preferable even).  Is 10 litres even within the realms of possibility?

We're now in the process of reducing weight as much as possible, re-making a smaller box, looking at lighter chord for parachute, maybe even re-thinking the parachute.

Thanks for any help.

[HOLGATES HERE]

I think I may mean G10/G20 from BOC, as opposed to 10/20 litres.

[David Akerman]

I think those are 10L and 20L, of compressed gas of course.  Those are nice cylinders - lightweight with handles and a gas gauge, but you do pay extra for those features.  Shop around and see if a regular steel cylinder is more in your budget.

Dave

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[HOLGATES HERE]

So I think I'm reading this correctly, an 800g payload with a Kaymont-600 balloon target burst altitude 30,000m requires 1.81 cu m of helium.  A x-small cylinder on balloonhelium.co.uk contains 1.81 cu m of helium so would just do the job.  I'm not suggesting I would cut it this close, but just so I'm sure I'm reading this all right.  We can stretch to £200 on helium at a push, and get under 1kg payload pretty easily.

On a side note, we had a skype call with a group of NASA scientists with regards to the project we're doing and they were talking about the payloads they've personally been involved in putting into the air, over a ton and a half weight and balloons bigger than football stadiums.  Our group were open mouthed to say the least.

[Steve Aerospace]

As Dave said 10l will be the cylinder size - and it will depend on the pressure (usually 200 or 300 bar) as to how much gas you get at air pressure.

I would allow yourself a fair margin for safety - don't assume you are going to get 1.81 cubic meters and the 3.72m/sec chosen is a bit slow an ascent rate IMO. Iin addition to the payload weight  also allow for the weight of the parachute, line, tape etc.  A  balloon often weigh up to 10% more than their size weight -  so a 600g balloon would typically weigh 660g (600g is a minimum weight).  Totex tend to be closer to their size weight (more of an average) - where as for Hwoyee it tends to be a minimum.  Balloon hellium tends to be about 97% pure in the UK reducing lift per cum (you are showing pure helium on the CUSF calculator)

I would suggest a 500g balloon and 400g payload and 100g allowance for parachute, line etc. (5m/sec ascent rate 29,831m burst 1.657 cu m of gas) as being more realistic for 1.81 cu m.

Just my oppinion. 

    Steve

On 28/01/2020 15:00, HOLGATES HERE wrote:

So I think I'm reading this correctly, an 800g payload with a Kaymont-600 balloon target burst altitude 30,000m requires 1.81 cu m of helium.  A x-small cylinder on balloonhelium.co.uk contains 1.81 cu m of helium so would just do the job.  I'm not suggesting I would cut it this close, but just so I'm sure I'm reading this all right.  We can stretch to £200 on helium at a push, and get under 1kg payload pretty easily.

On a side note, we had a skype call with a group of NASA scientists with regards to the project we're doing and they were talking about the payloads they've personally been involved in putting into the air, over a ton and a half weight and balloons bigger than football stadiums.  Our group were open mouthed to say the least.

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[HOLGATES HERE]

That's fab Steve, I think we'll probably end up with the size above that of 2.61 cu m which will allow room for a bit more weight in the payload.  They built the parachute themselves and I think perhaps the weight could have been less.  Might have to go back to the drawing board on that one.

On Tuesday, 28 January 2020 15:57:35 UTC, G8KHW wrote:

As Dave said 10l will be the cylinder size - and it will depend on the pressure (usually 200 or 300 bar) as to how much gas you get at air pressure.

I would allow yourself a fair margin for safety - don't assume you are going to get 1.81 cubic meters and the 3.72m/sec chosen is a bit slow an ascent rate IMO. Iin addition to the payload weight  also allow for the weight of the parachute, line, tape etc.  A  balloon often weigh up to 10% more than their size weight -  so a 600g balloon would typically weigh 660g (600g is a minimum weight).  Totex tend to be closer to their size weight (more of an average) - where as for Hwoyee it tends to be a minimum.  Balloon hellium tends to be about 97% pure in the UK reducing lift per cum (you are showing pure helium on the CUSF calculator)

I would suggest a 500g balloon and 400g payload and 100g allowance for parachute, line etc. (5m/sec ascent rate 29,831m burst 1.657 cu m of gas) as being more realistic for 1.81 cu m.

Just my oppinion. 

    Steve

On 28/01/2020 15:00, HOLGATES HERE wrote:

So I think I'm reading this correctly, an 800g payload with a Kaymont-600 balloon target burst altitude 30,000m requires 1.81 cu m of helium.  A x-small cylinder on balloonhelium.co.uk contains 1.81 cu m of helium so would just do the job.  I'm not suggesting I would cut it this close, but just so I'm sure I'm reading this all right.  We can stretch to £200 on helium at a push, and get under 1kg payload pretty easily.

On a side note, we had a skype call with a group of NASA scientists with regards to the project we're doing and they were talking about the payloads they've personally been involved in putting into the air, over a ton and a half weight and balloons bigger than football stadiums.  Our group were open mouthed to say the least.

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[John Laidler]

I've found 10l helium tanks on the web which say they can fill 125 18" foil balloons. My creaky mathematics suggests that is a total of 0.7 cubic metres.

John

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[HOLGATES HERE]

The x-small canister on balloonhelium.co.uk says it will fill 125 18" foil balloons and quotes it is 1.81 cu m.  How much is the 10L on ebay?

On Tuesday, 28 January 2020 16:34:20 UTC, John Laidler wrote:

I've found 10l helium tanks on the web which say they can fill 125 18" foil balloons. My creaky mathematics suggests that is a total of 0.7 cubic metres.

John

On Tue, 28 Jan 2020 at 14:17, HOLGATES HERE <hungr...@gmail.com> wrote:

I'm going to struggle to get the college to fund 20 litres of helium, but can put my persuasive hat on and get a delivery of 10L.  

What kind of balloon size and total weight are we realistically looking at?  We need to launch and collect on the same day, so a short flight time is fine (preferable even).  Is 10 litres even within the realms of possibility?

We're now in the process of reducing weight as much as possible, re-making a smaller box, looking at lighter chord for parachute, maybe even re-thinking the parachute.

Thanks for any help.

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[John Laidler]

My maths is creaky!  I've just done it again and 125 18" balloons comes out at 6.5 cubic metres. 

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[Steve Aerospace]

I've found the manufacturer quoted cu m cylinder capacity reasonably accurate when *everything* is accounted for.

I usually ignore the number of party balloon claims - I put that in the same mental dustbin as weather balloon sizes quoted in ft   - is that the  Barely Inflated Diameter, a working diameter or a burst diameter ? ...

    Steve

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