Balloon helium and Pi-in-the-Sky costs

[Oliver de Peyer]

Dear all,

I am not sure of people's individual email addresses or who to ask what exactly so apologies for the communal enquiry.

1) How long will a Qualatex balloon stay inflated at ground level (for a possible tethered display)?

2) Can they be refilled?

3) I see 30L-ish cylinders of helium on Amazon for three for £48. How many Qualatex fills will I get‎ from these?

4) How much does the Pi-in-the-Sky board cost?

5) Where can I get one?

6) Can a Qualatex lift it?

Pi is probably preferred since I have a colleague who wishes to write his own tracking software in Fugio, a graphics and video programming language that he has created himself and used for gallery exhibits running off Pis‎. It may seem a long way round to do it but that is what he wants to try.

7) Does anybody have experience of running a special events station and callsign? I thought I might segue this into the same exhibition (i.e amateur radio as well as telemetry from a tethered balloon).

The idea is still to deploy a tethered balloon and exhibit at the Eden Centre this summer. I am itching to try a true balloon launch nearby as well under my own auspices.

Any advice gratefully received.

BW

Oliver

M0LVR

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[David Bowkis]

I have had a Qualatex stay inflated for 3-4 weeks at ground level - but this was not carrying any load and it gradually lost helium over a period of time so you should test one with a payload.  I have refilled one.

See Random Engineering Balloons for balloon data "These balloons have an approximate weight of 37g and a approximate internal volume of 0.1cu m before envelope stretching. This means they can lift payloads of approx. 60g (or slightly more if you allow for stretching). "

Pi in the Sky see  Welcome to the Pi In The Sky Project - Pi In The Sky Project

Welcome to the Pi In The Sky Project - Pi In The Sky Project

Balloons

---

From: 'Oliver de Peyer' via UKHAS <uk...@googlegroups.com>
To: Ukhas <uk...@googlegroups.com>
Sent: Thursday, 11 May 2017, 0:44
Subject: [UKHAS] Balloon helium and Pi-in-the-Sky costs

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[Steve Aerospace]

1) I’d say several days before top up is needed.  I have a similar balloon in my living room right now and its been inflated since about 20th April - I’d say it was now 80% full.

2) yes - just put a bit more gas in the valve - see https://ukhas.org.uk/guides:filling_foil_balloons

3) the Qtex 36” foil balloons are 40g and will lift about 60g (i.e. have an internal volume of about 0.1cum). You need to know the internal pressure of the disposable cylinder to know how much gas it holds - the ones listed on the ukhas website https://ukhas.org.uk/guides:balloon_data are 0.25cu m (BOC small) and 0.4cum (BOC large).

4) https://store.uputronics.com/index.php?route=product/product&path=62&product_id=52

https://store.uputronics.com/index.php?route=product/product&path=62&product_id=96

6) I suggest the PITS zero as its smaller with onboard GPS antenna - its listed as 60g and will need batteries (I assume 60g is without batteries - Anthony?). You might remove the standoff hardware and save a little weight.  It says 20hrs on 3 x AA - so say about 6 hours on AAAs.  Lithium iron disulphide AA and AAA batteries are 15g and 8g each respectively (http://data.energizer.com/pdfs/l91.pdf http://data.energizer.com/pdfs/l92.pdf).  You could look for some other power solution which might be lighter - lightweight solar cells might be cool?

Steve G8KHW

 

[Oliver de Peyer]

Dear Steve and David,
Many thanks for your answers.

Regarding helium, Amazon for instance is currently showing this:
https://www.amazon.co.uk/Helium-Canister-Balloons-Cylinders-Super/dp/B00JEA7O8I/ref=sr_1_17?s=kids&ie=UTF8&qid=1494493013&sr=1-17&keywords=helium+canister

Which is three 0.25cum for £48, so 0.75cum total. I think this is actual helium instead of "balloon gas" so is this a good deal?
It is still only 7ish refills of Qtex 36'' balloons though (that would probably get me through the entire exhibition period at Eden though).

Regarding PITS zero, it is currently showing out of stock on Upu's pages. Will it be back in stock soon?

PITS + batteries on Qtex = too heavy, as far as I can see, but is there any reason you can't gang Qtexes? E.g two Qtexes on one line would lift 120g and so on.

The other cludge for a tethered display is that the tether can be a wire with the power supply on the ground.
However, the Eden Project is quite interested in the bioprospecting angle, e.g bioprospecting inside different domes and so on. So I need to add a payload of some sort on top of the PITS. Again, this can be cludged for a static display, for instance a length of tygon tubing running to a pump on the ground, so the air is being sampled at height but the balloon doesn't have to carry the pump.

Is it possible to refill a latex balloon?

Obviously we might be outside the weight range of the Qtexes especially if we actually try to fly a similar payload for real later on.
One could imagine some sort of valve permanently fixed in the balloon mouth to allow refilling. Has this ever been done?

About ganging lots of Qtexes together:

On a tangent, I have been previously thinking about novel canopy materials such as c‎opperised mylar etc but found this quite daunting.
I have been wondering instead about a non-gastight outer canopy and then a conventional inner canopy (latex, mylar etc). Thin copper foil or mesh would do for instance.

Obviously this is much easier to do for a non-stretching inner canopy. This argues for mylar balloons not latex.

So is there any limit really on how many Qtexes or similar that can be ganged together? Has this been tried?

Ten Qtexes would lift 600g, and so on?

Any advice gratefully received

Best wishes

Oliver
M0LVR

--
Oliver de Peyer, PhD
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The opinions expressed in this email are my own and may not necessarily reflect those of my employer.

[Steve Aerospace]

Its a fair deal for disposable canisters - but at £65 per cubic meter is a bad deal for helium in general - if your also thinking of a personal latex launch you should consider standard BOC/Air Products cylinders - which give prices down at about £25 per cubic meter or less. There are some good deals around - even some with indefinite cylinder rental.

but is there any reason you can't gang Qtexes? 

Nope - You can certainly use more than one foil balloon to lift a heavy payload for indoor tethering.

Is it possible to refill a latex balloon?

Yes - by either careful removal of the ties - or by using a radiosonde neck stopper/valve.

One could imagine some sort of valve permanently fixed in the balloon mouth to allow refilling. Has this ever been done?

Yes:

https://www.flickr.com/photos/16828840@N07/albums/72157635949806404

So is there any limit really on how many Qtexes or similar that can be ganged together? Has this been tried?

Ten Qtexes would lift 600g, and so on?

Sure - we used to do it all the time in the early days of picoHABing: https://www.flickr.com/photos/16828840@N07/albums/72157680601428823

- before we found out about reliability of clusters in flight.  OK for indoor tethered use though.  For free flight under the UK small balloon rules one should ensure the balloons and payload all fit inside a 2m sphere.

Steve

[Stuart Robinson]

On Thursday, May 11, 2017 at 12:35:48 AM UTC+1, Oliver de Peyer Astrobiologist wrote:

> Dear all,
> I am not sure of people's individual email addresses or who to ask what exactly so apologies for the communal enquiry.

> I have a colleague who wishes to write his own tracking software in Fugio, a graphics and video programming language that he has created himself and used for gallery exhibits running off Pis‎. It may seem a long way round to do it but that is what he wants to try.

That bit sounds interesting, could you contact me from my website ?

www.LoRaTracker.uk

[Oliver de Peyer]

Thanks again

Regarding the helium, our hosts were already getting a bit skittish. I will ask if I can take a bigger cylinder on site, otherwise I will have to hide smaller cylinders in plain sight. Even that has problems because the camping on-site is more like glamping (heated tipis and so forth). We already have a variety of static and video displays about our 2010 flight so the danger is always that they suggest we leave it at that. I want to winkle out a balloon flight (tethered or otherwise) if at all possible. I am sure they must have a cylinder farm somewhere, I just need to ask very nicely!

I know that latex balloons perish quite quickly under illumination (in the gallery exhibit in Birmingham there were latex balloons illuminated by video projectors, and they began to discolour and then crack where they were illuminated). The Eden domes are designed to let in maximum sunlight. So upon reflection I think it will have to be Qtexes.

I wonder if a way can be found to improve reliability of ganged Qtexes?

It occurs to me that the neck is designed to be load bearing and it should be kept vertical to prevent lateral strain. Therefore Qtexes could be ganged along a rigid pole perhaps? Or maybe a circle?

This might even be stable since the moment of inertia of a long pole might be quite high.

How thick is an inflated Qtex please? 

I was just wondering how closely together they could be stacked (vertically or horizontally)

Reliability wise, I imagine that a failure of one Qtex causes a slow descent?

This might in fact be OK for payloads requiring a vertical transect.

I like that Totex mouth valve - was that 3D printed?

As usual this has been a very interesting thread, I have lots of ideas for a real flight following on from Eden (if it goes ahead). I think probably it still has to be Qtexes since I could use a single outer inelastic, non-gastight envelope, copper mesh or suchlike (which is a standard bulk product for lithium batteries, it turns out).

I am still trying to find a coating for latex balloons, but I suspect their toxicities will be too high. So a outer copper shell might be best.

I am interested in permanent neck valves for all balloon types since one idea I had in the past is for a very fast‎ ascent to minimise contamination with actively controlled venting to prevent bursting. I have an inside-versus-outside barometer I could use and some SMA venturi gas valves (where the SMA actuator is a wire through the venturi and de-occludes it when contracted under current, otherwise it blocks it).

Any idea when the PITS zero will be back in stock?

BW

Oliver

M0LVR

Sent from my BlackBerry 10 smartphone on the EE network.

From: Steve Aerospace Sent: Thursday, 11 May 2017 14:22 To: uk...@googlegroups.com Reply To: uk...@googlegroups.com Subject: Re: [UKHAS] Balloon helium and Pi-in-the-Sky costs

[Steve Aerospace]

On 12 May 2017, at 19:20, 'Oliver de Peyer' via UKHAS <uk...@googlegroups.com> wrote:

I wonder if a way can be found to improve reliability of ganged Qtexes?

SR: I’d don’t really expect a reliability problem with indoor tethered foil balloons - its only an issue where they get stretched to near maximum.

How thick is an inflated Qtex please? 

I’d say about 25 - 30cm nicely inflated  - depends on how much you stretch them.

I like that Totex mouth valve - was that 3D printed?

No its an injection moulded part.

I am interested in permanent neck valves 

My own neck valve (successfully flown and used) if you haven’t seen it before:

https://www.youtube.com/watch?v=eahxgo7u5nI  

Steve

Steve Randall

Random Engineering Ltd

st...@randomaerospace.com

+44 7802 242135

[Oliver de Peyer]

Many thanks‎ again

Where do the Qtexes tend to fail? 

I am wondering if any of the historical tricks that Dan dug up regarding bigger balloons would help‎ (such as minimising neck strain and putting a harness over the top of the balloon instead). I know people have moved on from ganged balloons but I have a feeling that that is what I will need to try for my purposes for actual flights.

I'll dig out the SMA valve if it is still around, to see if it fits in a Qtex neck. It is quite small but depends on gas flow when open to stop it overheating‎.

BW

Oliver

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From: Steve Aerospace Sent: Friday, 12 May 2017 20:18

To: uk...@googlegroups.com Reply To: uk...@googlegroups.com Subject: Re: [UKHAS] Balloon helium and Pi-in-the-Sky costs

[Steve Aerospace]

On 12 May 2017, at 21:04, 'Oliver de Peyer' via UKHAS <uk...@googlegroups.com> wrote:

Where do the Qtexes tend to fail? 

I got diagonal rips in these: 

https://ukhas.org.uk/projects:splat

36” Qtex foil under test:

https://www.youtube.com/watch?v=hr6x3r8phvE

pretty sure the failures occur mid face.

Steve

[Oliver de Peyer]

Interesting, this makes sense because the balloon will be under strain vertically when under pressure.

So Dan's trick from the balloon papers of yesteryear might still apply. Imagine a mylar balloon on its side, like a discus, with a harness over its top face. This will relieve strain on the neck and top face somewhat. I imagine it will bulge and burst on the bottom face instead eventually. But it is not being stretched vertically any more.

I have a reel of 150Ib rated Kevlar thread which was for a kite ham antenna project... might give it a go if we go ahead!

(It's actually very thin kevlar - but at a pinch it would take my entire body weight, that's crazy!! What do you guys use for the payload lines on picos?)

BW

Oliver

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From: Steve Aerospace Sent: Friday, 12 May 2017 22:03

To: uk...@googlegroups.com Reply To: uk...@googlegroups.com Subject: Re: [UKHAS] Balloon helium and Pi-in-the-Sky costs

[John Underwood]

I think the failure on the side of the balloon may have more to do with the local radius of curvature than the payload weight. Fabrics / membranes are better-able to carry pressure load when the radius of curvature is lower (i.e. more curvature).

Kevlar is incredibly strong. A few filaments would probably be sufficient for a pico-balloon; however, it is very susceptible to damage from UV. You could expect it to loose 50+% of its strength over a period of a few weeks in sunlight.

[Oliver de Peyer]

Dear John,

But the rips seem to be mostly vertical, if it was just down to local radius of the balloon's inflated shape then you would expect them horizontal as well.

However, I would still think that the balloon will be stretching itself into a slightly elongated ovoid along its vertical access due to its buoyancy (and meanwhile being stretched downwards due to payload weight).

Actually that will flatten out the balloon along the vertical axis ‎so indeed the radius of curvature will be less along the vertical direction.

Does that sound right?

Worth experimenting along the lines of what Dan found out, to see if a harness over the top of the balloon (instead of on the neck) reinforces it.

What is better than‎ kevlar? How about Dakron?

BW

Ol

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From: John Underwood Sent: Saturday, 13 May 2017 07:27