Ascent rate & Balloon shelf life

[Nick McCloud]

Hello everyone,

I see the cost of Helium has put a real crimp on activity which is a double-edged sword in todays climate - save the He vs reducing a real world project from budding engineers.

I have a couple of balloons on hand but they are pre-Covid & I suspect they are no longer viable - I see things like 24 month shelf-life for foil wrapped ones. Is this what others see / consider about right?

So if I can't get hold of the balloon size I'd like, what are the considerations I should be aware of with a slow ascent rate, slower than the 3-4m/s recommended?

If anything, this gives me more time to get the little loves (students) through McD's whilst the payload is airborne.

Supplementary question, would two balloons side by side (so latex on latex) work - I suspect this will be opinions rather than direct experience, which is fine.

Additional bonus opinion sought, if I fill with Hydrogen away from the students, if I have it 20m up when I bring it over to attach to the payload, so unlikely to have a spark trigger  any excitment, does this sound/feel safe(ish). 

Part of the fun for students is the "drama" of the fill, but I can probably substitute that with a much smaller 2nd balloon with a pico-tracker on it for them to fill with He.

Meanwhile, I've got to put my PitS on a diet ...

Nick

[Ed Moore]

Never had a problem using Hydrogen, you should be fine. Two balloons works too, they stay seperate (direct experience). V slow ascent rates risk the balloon not bursting but just reaching a super-pressure equilibrium. You salute it from the shoreline as it wonders off to explore the world.

Ed

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[Steve]

My 10p worth embedded below.

    Steve

On 02/06/2025 14:13, Nick McCloud wrote:

Hello everyone,

I see the cost of Helium has put a real crimp on activity which is a double-edged sword in todays climate - save the He vs reducing a real world project from budding engineers.

I have a couple of balloons on hand but they are pre-Covid & I suspect they are no longer viable - I see things like 24 month shelf-life for foil wrapped ones. Is this what others see / consider about right?

SR: If they are pre-covid (>5 years) then I wouldn't risk expensive helium on them - but I would risk Hydrogen if they are Hwoyee and stored well - Ive used old Hwoyees of that sort of age with only a minor degradation in performance.

Take a look at the colour - if still cream then probably OK,  if browning then probably not. 

So if I can't get hold of the balloon size I'd like, what are the considerations I should be aware of with a slow ascent rate, slower than the 3-4m/s recommended?

SR: Personally I aim for 5m/sec as a minimum - certainly 3 - 3.5 is in float territory - especially on the larger Hwoyees.

If anything, this gives me more time to get the little loves (students) through McD's whilst the payload is airborne.

Supplementary question, would two balloons side by side (so latex on latex) work - I suspect this will be opinions rather than direct experience, which is fine.

SR: I've flown balloons side by side before - use long enough lines and they separate (because of the air flow between them as they ascend).   If you use two balloons use cut-aways because one balloon will burst before the other and then the remaining one will probably float.  I use this technique to get latex floater flights.  Two balloons is noticeably less efficient than 1 larger balloon - so if you use 2 you probably won't be wanting to use helium.

Additional bonus opinion sought, if I fill with Hydrogen away from the students, if I have it 20m up when I bring it over to attach to the payload, so unlikely to have a spark trigger  any excitment, does this sound/feel safe(ish).

SR: I think the main danger point is if the balloon rubs against anything then potential for burst and static.  The only accounts I have of hydrogen meteorological balloons bursting into flames was from project outward - when the balloons rubbed against the canvas of the filling tents.  No-one died - but some burns resulted - instant sunburn they used to call it.  Several instances during the 100,000 flights.

Part of the fun for students is the "drama" of the fill, but I can probably substitute that with a much smaller 2nd balloon with a pico-tracker on it for them to fill with He.

Meanwhile, I've got to put my PitS on a diet ...

Nick

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[Mika Köching]

Regarding Hydrogen safety: I know someone who used a big Helium balloon to pull up an antenna. He said after some time the balloon actually burst because of an electrostatic discharge. This COULD be a problem. Maybe limit the amount of students involved with the balloon and quickly let them let it go before some electricity could build up. Might not be a problem with nylon line though.

[Nick McCloud]

 You salute it from the shoreline as it wonders off to explore the world.

Only managed that once and I'd sent DaveA off on the retrieve - not my finest hour!

OK, so summarise thus far:

• Don't risk He &/or Student launch with older balloons - they may work, they may not, my mileage may vary.
• Don't reduce the ascent rate - I've suceeded with 4.5m/s previously but I've also hit the international press & BBC Breakfast news with lost payloads so I'll take the hints not to warp time & space.
• Two balloons possible but introducing a cut-down is another complication (DaveA wouldn't have to drive so far if his cut-down had worked, so not ALL my fault except I retied it whilst Dave drove home for a replacement after he prematurely triggered it on the ground).
• Hydrogen plan has potential - I've not had issue with personal launches and I remember the videos on Project Outward plus SR & DA doing gymnastics during a height attempt - I'd be filling a safe distance away, letting it go up and then hooking the end of the line on to the student package which should take 10 seconds then they can release, so it will be at least 15m away and they will be exposed to the risk for ~30s. I'll talk to teacher who would love to pay for H2 now they've finally found out how much He is!

Thanks for inputs thus far, any others, please chime in!