High altitude balloon launch

[Baha Baydar]

Hey folks,

There's a group of us at work that are planning a space balloon launch later this summer.

Would anyone be interested in either helping or launching a second balloon? I've found a company in Ontario that sells them. We're looking at $75 for an 800g balloon.

Baha

[Evan d'Entremont]

That sounds like fun. What kind of altitude and what legalities are involved? 

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[Shawn Wilson]

I would love to, but I know I'm likely over committed already and can't take on any new recurring projects until the fall.  If you need anything specific (like use of a modest wood shop), I'd be happy to help.  I checked into balloon path simulations a year or so ago, though, and it seemed like they would go out over the Atlantic almost immediately.  I didn't get a feel for how much that changes day to day or season to season though.  Where would you launch it and where do you anticipate recovering it?

[Chris McDonald]

I've researched it a few times. Recovery is very difficult in NS. It has a very high probability of ending up in the ocean or a lake. 

What kind of a payload are you guys doing?

Tracking wise the the common payload is 2M APRS. A new cheaper(disposable option) is 30M WSPR.

http://qrp-labs.com/ultimate3/ve3kcl-balloons.html

They have been sending ultralite payloads around the world on mylar party balloons. Somewhat lower altitude than the edge of space I believe. 

Video transmission is far too much of a power hog for long missions. Transmitters and cameras are not all that cheap either. With a large tracking dish on the ground 5.8Ghz might work ok and be fairly cheap. Without a tracking dish your looking at a more expensive 70cm transmitter and even more power consumption. 

Then there is the fly it home option... unfortunately somewhat illegal. Once you have control of decent it likely gets classified as a UAV or guided missile. One could apply for a special flight operation certificate(SFOC) which would make the UAV legal. 

As for the legality of launching a balloon. There are not many regulations that apply as long as it's under 115 cubic ft. Its good practice to notify Nav Canada ATC. 

It's certainly on my bucket list of things to do. So I'm in either way. 

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Chris McDonald

[Baha Baydar]

We're hoping for between 60-100K feet.Surprisingly there don't seem to be a whole lot of regulations involved. Radio transmitter licensing depending on the bands used, size of the balloon has to be under 115ft^3, notification to nearby airports.

Depending on how this launch goes, we're planning follow up launches and may even graduate to large scale rockets.

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Baha Baydar
bba...@gmail.com

[Baha Baydar]

The current plan is to launch from somewhere in New Brunswick in order to maximize available land recovery options.

Thanks for the offer of the wood shop. Most of the construction will be foam and tape for the payload box.

On Thu, Jun 9, 2016 at 11:28 PM, Shawn Wilson <sh...@glassgiant.com> wrote:

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Baha Baydar
bba...@gmail.com

[Baha Baydar]

Yeah, we're looking at launching in NB in order to maximize recovery chances. 

The payload will be a sensor suite (TBD, but likely barometric, magnetic, GPS, etc) and two cameras. One will be a GoPro and the other a PiCamera attached to the Pi Zero flight computer. 

I don't think we're going to attempt live video transmission as we don't have the knowledge for that. We were looking at APRS and 430Mhz data transmission which seem to be the most common options for telemetry. 

Baha Baydar
bba...@gmail.com

[Chris McDonald]

Yea operating under an amateur radio licence is pretty much your only option unless your going to spend big money on an approved transmitter and licence. ISM band stuff would have to be Industry Canada approved with generally means super low power. 

Automated Packet Reporting System(APRS) on 2M is your best bet as there is already a network of ground stations in place that will report to aprs.fi automatically. A secondary 30M WSPR/JT9 transmitter wouldn't be a bad idea in case the balloon drifts out of range of the APRS network. 

I have my advanced amateur radio licence so I could oversee the radio systems. I could also apply for a call sign for it. 

The Pi is a bit of a power hog. I'd suggest using a micro controller as the flight computer. There are lots of lower power choices. On the cheap side an APM clone would be very easy to use. 

http://www.myrcmart.com/apm-26-neo6m-gps-ublox-combo-gps-kit-p-7817.html

or

http://www.myrcmart.com/apm-26-ardupilot-mega-26-flight-control-board-miniapm-v31-35x35mm-p-8000.html

One of these would take care of the APRS, GPS, etc...

https://www.tracksoar.com/

70cm (430Mhz falls in this band) might not be a bad idea for an uplink. Handheld yagi's could  be used to track the balloons position.

I'd be interested in trying 5.8Ghz wifi for the data link but again power consumption may be an issue. You can get pretty high gain out of a 1M dish (something like 30-40dB) at higher frequencies. I've got one behind my shed that I've been saving for something like this. Aiming the dish is the tricky bit. I've been collecting parts to build a 2axis dish rotor. Its kind of a someday project.   

A 5.8Ghz analog video feed would be pretty easy to try. I've only gone as far as 2km with a 250mW transmitter and 0dBi antennas. With a 600mW transmitter(+4db), 6dBi antenna on the balloon and maybe 30dBi on the ground antenna 100km(~35dB path loss) should be no problem.   Maybe set it up on a timed cycle to save battery. Power up for 120 seconds every ten min or something. 

An NB launch would increase the odds of recovery. Where exactly are you guys thinking?

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Chris McDonad

[Evan d'Entremont]

Legalities :D

I'd be down for building a large tracking parabolic antenna. I also have a truck to mount it to and a garage to build it in. 

Guided missile is out? Becuase I have the software :) 

[Chris McDonald]

I should also note that its 35dB more path loss than the 2km I've tested. The absoulte path loss is in the 200dB ballpark. 

[Evan d'Entremont]

So 430mhz is about 70cm, so a mesh reflector would need to be less than 7 or perferably 3.5cm..

This seems pretty easy.. 

Use a gps for its current location, and have it point at another set of coordinates (sent from the baloon). 

Use this for aiming. http://www.instructables.com/id/Solar-Tracker-in-the-Internet-Cloud/

Lightweight reflector http://m.homedepot.com/p/Everbilt-1-in-x-3-ft-x-10-ft-20-Gauge-Galvanized-Poultry-Netting-308410HD/204331927

 wood frame like this 

http://greenpowerscience.com/PAYLENSESFORSALE/TROUGHKIT48X24.JPG

It would pretty much operate on the same principle as this 

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTxbCT9TRWgbiZA9sLMKG0f5ujXk2zMBfL_LXGc93BcOOGLtgGQNg

[Chris McDonald]

I was thinking you would need something like 20dB of antenna gain which you need a yagi array to get in the 70cm band. But I just checked the RFM22B(a common 433Mhz transceiver chip) specs and its +20dBm(20mW) transmitter and -121dBm receive sensitivity will do the 125dB path loss of 100km with simple dipole antennas and have margin of like 16dB. I'd still use handheld yagi antennas on the ground stations as there its unlikely we would be directly below . They have a large beamwidth so you just need to point them in the general direction of the balloon. 

The 70cm band is 420Mhz-450Mhz. The antenna elements would be around 1/2 wavelength, so around 35cm.

Here is a set of plans:

http://www.amsat.org/amsat-new/information/faqs/crow/JulAug06AmsatJournal.pdf 

A mesh reflector isn't going to get a whole lot of gain.

The guys bouncing signals off the moon(aka Earth Moon Earth or EME) use yagi arrays and this is what I thought we would need: 

http://www.g0ksc.co.uk/DJ3JJ.pdf

I still think 2m APRS is the best thing to use as the primary downlink. 

A 30M (10.1401Mhz) WSPR backup wouldn't take much cost, weight or power. That 30M backup signal would go around the world in the right conditions but the data rate is like 1byte/second or less. It takes something like 120 seconds to transmit call sign and location. The downside is the antennas are very large. On the balloon end the best antenna would be 7.5M up to the balloon and another 7.5M hanging below. 

Receiving 2M or 30M on the balloon end takes some serious processing power. So we would need something like an RPi on board. 70cm is easy with something like the RFM22B chipset. The power draw of the RPi is a pretty big concern. It draws around an amp depending on CPU load. 

At that kind of load lithium AA batteries only have a 1Ah capacity. The capacity gets worse as the temperature drops and the current draw goes up. We would need at least 3 cells in series to get above 3.3v, then we also need a low drop out regulator. A 4 or more in series with a switching regulator might be better. So for every hour of run time we need 4x15g, so 60g of battery per hour. It should increase significantly more than 1Ah per set of batteries added in parallel. So 3 cells parallel by 4 cells serise would give us 180g for the battery pack and well over 3 hours of run time. 

Battery Datasheet I'm working from:

http://data.energizer.com/PDFs/l91.pdf

   

Heat from the Pi would help to keep things warm. How warm depends on how well insulated.

If the temperature could stay above -10C, NRC18650 batteries would give us nearly 3Ah at 6.6v at only 94g for the 2 cells.

So many interesting challenges with this kinda project. So much to think about.

What happens to all that heat while its sitting on the ground before and after launch. Yet another thing to think about. Maybe a servo controlled vent that open and closes when things get too hot or cold. 

Remote balloon pop and parachute release might be handy. If it starts drifting towards the ocean or out of range cut the balloon and freefall most of the way down, release the parachute only once its closer to the ground so it doesn't continue to drift. 

So many thoughts and ideas... I'm just going to end here. 

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Chris

[David Johnston]

I am a licenced Amateur Radio operator, VA1 DCJ . we can use APRS beacon on 144.390 MHz for telemetry.

the Atlantic Canadian repeaters will put the beacons on the internet

[Baha Baydar]

Quick update to this. 

We're currently looking at the Labour day long weekend (3rd, 4th, 5th) to launch. 

Most of the payload is ready now and the APRS radio setup has been tested. (Thanks Chris!)

Let me know if anyone is interested in helping out.

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Baha Baydar
bba...@gmail.com