Balloon Experiments

[trash]

There appear to be a few people playing with balloons as of late.


This has been a local group that have done a few launches that you can see track logs on aprs.

There are a few other people conducting simpler flights which also can provide some useful info.

I launched a LIPD on a party balloon with a temperature sensor for a bit of fun a couple of weeks ago. From data heard, the balloon went to about 20,000ft and lasted about an hour.
The payload was simple. A tiny 3V lithium battery recovered from a helicopter, a LIPD from jaycar and a surface mount 555 timer with some other SMD components to create a tone dependant on temperature.
It had 5 minutes of bench testing before it was picked up and sent off on it's mission, I never saw it again. I didn't have time to RDF it.

It was a small test by the club for a bigger balloon. One that is expected to go to 120,000ft. It will carry several transmitters including APRS. 1250MHz and 2400MHz ATV transmitters, SSTV and two still cameras.
It also has a geiger counter on board for measuring cosmic radiation.
The downlink is 433.920MHz AM. It's CW with modulated clicks typical of a geiger counter.

There will also be a cockroach riding on board. (The local scouts are running that experiment) and a paper aeroplane which will be released at altitude.
It will be interesting to see if it is recovered, where and when.

There's still some space left on board, I'm wondering if anybody has any other ideas for payloads.

[Fernbay]

3g/gps real time webtracker?
Wifi server/relay platform?

[Learjet]

Can you carry a couple of snakes up and drop them on New Zealand?

I did some party balloon experiments in the mid 1980's. They carried simple L/C transmitters that varied in frequency with temperature. I don't know how high they got before bursting but where ever they ended up it was MUCH colder than the freezer at -18C.

One night there was a temperature inversion and radio ducting was strong. The temp actually went up as the balloon rose into the inversion layer.

On a number of flights I noticed the wind changed direction 4 or 5 times, often with an accompanying change in temperature.

[Tasman]

No snakes to New Zealand. I might go there fishing again.
Suggestions. 1) Inflate your balloon with hot air from Kev and Jul. It might get as far as the moon.
2) Include them as experiments on the trip to experience global warming!
Seriously. Sound like a lot of fun.

[toadskin]

Maybe some Cane Toads to put in lake Burley Griffin....then the mongrels in Canberra may see a reason to do something about the ugly damn things.

[jok11n]

I don't know how high they got before bursting but where ever they ended up it was MUCH colder than the freezer at -18C.
.

I watched a story on ABC24 the other night about weather balloons, they showed them launching the balloons and talked a bit about what's involved etc, they showed the balloon at launch and it was about a meter or so in diameter and said that by the time the balloon explodes it grows to about the size of a two story house, I guess to do with the atmosphere, temp etc at those heights, never knew what was involved but found it interesting

[Coldamus]

You'll be in trouble if you hit the flying doctor!

Seriously, there are fairly strict regulations relating to unmanned free flight balloons:


I haven't read it all but Subpart 101.E seems to be applicable.

[gordon_s1942]

So I guess being on a light aircraft/Heavy route might get me few nasty looks from the CASA mob then??

Balloons expand as they rise because of the reduced atmospheric pressure which is exactly the reverse if you tried to submerge one.
From ignorance I think the Barometric pressure drops 1 inch per 1000 feet but dont quote me.
The one to see is the experiments they did way back in the 50's and 60's when they sent some totaly mad fool up in a Balloon almost to the edge of the atmosphere.
While going up was fairly hair raising, the only way down was to JUMP and Free fall thousands of feet untill the atmosphere was dense enough to fill the umbrella of a Parachute when it was finaly opened !!

[jok11n]

So I guess being on a light aircraft/Heavy route might get me few nasty looks from the CASA mob then??

I'd hazard a guess they would take some interest in what you were up to

the show I mentioned about the weather balloons showed them releasing them somewhere in the vicinity of the airport and they had to get clearance from the control tower as to when to release and had around a one minute window of opportunity to release it and get a lock on it for tracking, they send one up every day

[trash]

3g/gps real time webtracker?
Wifi server/relay platform?

GPS tracking. That's what APRS does.
The GPS is able to operate above 60,000ft for this balloon.

Wifi is an interesting idea, It might be worth an experiment in the future.
A cross band repeater is considered if we do other launches in the future.

You'll be in trouble if you hit the flying doctor.

Ah there is always somebody who wants to rain on the parade
Lucky for us, we have all the air traffic clearances sorted.
Air traffic will be diverted around the balloon in our case so if anybody hits it, they'll be the ones .... in trouble. They can blame the balloon as they both plummet to the ground

I'm still considering other experiments. I've managed to miniaturise quite a payloads now. The geiger counter is 18 grams and draws 65mA @ 3V, that includes the tube and the UHF transmitter.

I can get the GPS and the APRS controller down to less than 10 grams. I'm working on a 2m transmitter. I'm trying to get 5 watts out of it and keep it less than 30 grams. Argent data units are 500mW and about 14 grams.

[Uncle Fester]

...I'm working on a 2m transmitter. I'm trying to get 5 watts out of it and keep it less than 30 grams...

How many kilos is the battery going to weigh to power that ?

Might I suggest naked solar cells as a power supply?

Isn't it possible to design and load your balloon to stay at a certain height almost indefinitely, at least for a longer time without bursting?
As the pressure gets low so does the buoyancy. Shouldn't be too hard to calculate at what height your fully loaded balloon reaches equilibrium and it's pressure/volume in that state.
Then just make sure your balloon material can handle that volume perhaps with +30% reserve and at the expected temperatures which I believe will get lower than -70°C.
Then you can have your own private satellite

[trash]

I don't know the weight of the batteries. They're lithium, so the mission controller is getting a good power to weight ratio. Solar panels are heavy and not reliable. The balloon payload spins and sways.

It is possible to make a balloon ascend to a height and keep it there without bursting, but the helium does leak out, and eventually the balloon becomes negatively bouyant and it will start to descend. The balloon has to be neutral pressure. As the lifting gas expands, it starts to overflow from the balloon until it looses enough gas that it can't lift any more.
Temperatures are about -35deg, depending on how high you go. -70C is a little low. One might expect to see high altitude dry ice snow in that was the case.

No private satellite ... it will come down and much sooner than a LEO satellite.
Try cubesat for that kind of thing

[Uncle Fester]

I wrote naked solar cells, NOT panels.
Like these:

They weigh 6grams each.
10 cells weighing only 60 grams would deliver 17 watts in daylight and high above the clouds up there seriously more.
4AH of Li-Ion @ 7.4V weigh 180 grams and would be empty from that load in far less than 2 hours.
I was thinking to attach the cells each on one spot with a small dab of adhesive on the top surface of the balloon.

There are foil balloons that do not loose the gas for weeks even months.
As they do not stretch it might be an idea to fill a whole bunch of them for example only to a third of their volume at sea level. As they rise their volume increases but not their pressure. They then gain on displacement at higher altitudes and can continue to climb. Pressure will eventually build up as they climb higher but because they can not increase in volume they will not climb so much further and should not burst.
I am no mathematician but I am sure this can all be fairly simply calculated.

[Onefella]

A few times in the past, I have let a bunch of the XL party balloons go with multi-coloured flashing LED's inside them. The legs of the LED's were just sticky-taped to two 3V button batteries bought in bulk with the LED's.

On a clear night it's fun to watch the highest balloons in the group suddenly shoot off in another direction from a wind 'layer', with all the others following soon after. The effect is like dropping confetti on front of a fan, but in reverse.

Hard to say how high they got, but they were still visible with binoculars after about 45 minutes.

[trash]

I wrote naked solar cells, NOT panels.
They weigh 6grams each.
10 cells weighing only 60 grams would deliver 17 watts in daylight and high above the clouds up there seriously more.

But still not able to deliver the power required, when it's required.

I'm not the mission controller for our balloon, so I don't have to worry about supplying the power, just using it I know the batteries we're using are a bank of lithium batteries at 12V, I'm not sure of the storage capacity.

There are foil balloons that do not loose the gas for weeks even months. As they do not stretch it might be an idea to fill a whole bunch of them for example only to a third of their volume at sea level.

With a closed system like that is that it is positively bouyant and it's a closed system, so that bouyancy is fixed. The balloons will rise, expand and burst.
Unless of course you use only a small amount of gas in each balloon and they don't burst when they reach equilibrium with the surrounding atmosphere.
The problem with that is a lot of weight is lost just lifting the balloons.
Unless the gas can bleed off and escape, the rig will be too heavy to get off the ground or too light it will never be neutrally bouyant before balloons burst.

I have considered this for other smaller experiments with long duration neutrally bouyant flights. The trick is to take advantage of the balloons bursting. Lets say 10 balloons, more than enough to lift a small payload.
As the balloons rise, they expand until one bursts. Now the lift gas is reduced and the ascent rate reduced with it. Another balloon bursts and then another until the remaining balloons and payload are neutrally bouyant.
Party balloons aren't much good past 20,000ft. The idea needs a bit more research The other method we've tried is as before, allowing gas to vent.

As they rise their volume increases but not their pressure.

That's correct, but it's not the absolute pressure of the balloon gas, it's the pressure difference on the balloon that is the consideration.
So with 1000mB inside and 500mB outside, this exerts the same force on the balloon as 2000mB inside at seal level.

00000ft = 1000mB
10000ft = 700mB
20000ft = 470mB
30000ft = 300mB
40000ft = 200mB
50000ft = 100mB
75000ft = 40mB
100000ft = 1mB

and should not burst.

It depends on the strength of you balloon. But as you rise past the point where the balloon will not expand, then the relative pressure difference builds exponentially with a now rigid balloon, rather than elastically as it would with a latex balloon.

Testing the lifting capacity of balloons is surprisingly easy thing to do.
It's a great junior science (year 8 level) kind of experiment that kids can be asked to test.

If you're a bit more serious about it and have access to scuba gear. A diving pool is a great way to test balloon designs because of the dramatic changes in pressure under water. 10 metres simulates about 20000ft.

[Uncle Fester]

Party balloons aren't much good past 20,000ft. The idea needs a bit more research

That sounds like party ballons can handle twice the atmospheric pressure.
Don't need scuba gear and a deep pool to find out how much they handle, any old air pump with a pressure meter will do or a compressor.

So if I use my idea to fill 30 (+ 10 for dead weight) foil ballons only to 30% volume, they will reach max volume but still have pressure equilibrium @ 30,000ft.
They would possibly start bursting @ 45,000ft. Then following your strategy, the weaker ones will burst one at a time at this height until the rest becomes neutrally bouyant. Ten sacrificial balloons could be filled to 50% volume at take off so they will burst earlier for this reason.

Sounds worth a try!

A few of those 6 gram solar cells should surely do the shot to power a GPS tracker, a mini video camera, a 2.4Ghz transmitter 1W as a down link, and keep a tiny rechargeable LiPo alive for backup power through the night if needed.

Might travel around the world in 80 days

[Peck]

There's still some space left on board, I'm wondering if anybody has any other ideas for payloads.

How about a Carbon Tax Meter?
Might give us some idea what we're in for?