How to obtain Altimetry- and Pressure-Data in High-Altitude

[MalfunctionM1Ke]

Hello Folks,

I am thinking about a Payload for a Weatherballon.

Any ideas how to obtain Altimetry- and Pressure-Data in High-Altitude? (up to 30.000m/100,000ft)

A household Altimeter will only calculate up to say 5000m and a Barometer 980-1050hPa.

I guess I need something more special or a way to think outside the Box.

My Current Idea of a Payload is the following:

-Camera (HD, maybe a GoPro?)

-Battery-Pack

-GPS-Tracker

-2-3 Handwarmer to keep the camera and battery from freezing

All packed in one Styrofoam-Box

Mainly I want to avoid to build an Raspberry Computer myself as I haven't soldered something in a long time and never programmed a Computer.

Any Ideas?

Thanks a bunch.

Edited October 6, 2015 by MalfunctionM1Ke

[UmbralRaptor]

Some sort of thermometer comes to mind. If you're willing to throw $100-200 at it, you could make a smartphone be the payload (camera, loads of sensors, onboard computer that is admittedly more locked down than a RasPI)

[Nibb31]

-Camera (HD, maybe a GoPro?)

-Battery-Pack

-GPS-Tracker

A cheap Android cell phone has all of those built-in. If you don't want to program, you can automate most tasks with Tasker, and it can even call you back when it lands. The GPS will provide altimetry data. For temperature and air pressure, you could make an arduino bluetooth board or maybe one of those bluetooth weather stations from Oregon.

Edited October 4, 2015 by Nibb31

[MalfunctionM1Ke]

A cheap Android cell phone has all of those built-in. If you don't want to program, you can automate most tasks with Tasker, and it can even call you back when it lands. The GPS will provide altimetry data. For temperature and air pressure, you could make an arduino bluetooth board or maybe one of those bluetooth weather stations from Oregon.

Some sort of thermometer comes to mind. If you're willing to throw $100-200 at it, you could make a smartphone be the payload (camera, loads of sensors, onboard computer that is admittedly more locked down than a RasPI)

The Smartphone looks like a great alternative.

Are there any specific Apps you can recommend?

[Shpaget]

GPS has some imposed limits on altitude, so make sure you check up on that.

[GoSlash27]

A mechanical or electronic barometer isn't going to be sensitive enough to register such low pressures, but a pressure column could do it.

You would have to keep it vertical and not jostle it around too much. Just set up a scale next to the column and take pictures every now and then. Also, the fluid doesn't have to be mercury. You just want something that will remain fluid throughout the flight. I think ethylene glycol (automotive antifreeze) would do nicely.

Best,

-Slashy

- - - Updated - - -

GPS has some imposed limits on altitude, so make sure you check up on that.

^ "Export restriction mode". I had a run- in with that once.

If your cell phone exceeds 60,000' altitude, there's a better than even chance 100% certainty that it will refuse to track it's location via GPS for at least 15 minutes. You might lose the whole thing if you don't have a backup plan.

Best,

-Slashy

Edited October 4, 2015 by GoSlash27
assuming your location is accurate...

[MalfunctionM1Ke]

A mechanical or electronic barometer isn't going to be sensitive enough to register such low pressures, but a pressure column could do it.

https://www.chem.wisc.edu/deptfiles/genchem/sstutorial/Text9/Tx94/tx94p1.GIF

You would have to keep it vertical and not jostle it around too much. Just set up a scale next to the column and take pictures every now and then. Also, the fluid doesn't have to be mercury. You just want something that will remain fluid throughout the flight. I think ethylene glycol (automotive antifreeze) would do nicely.

Best,

-Slashy

- - - Updated - - -

^ "Export restriction mode". I had a run- in with that once.

If your cell phone exceeds 60,000' altitude, there's a better than even chance 100% certainty that it will refuse to track it's location via GPS for at least 15 minutes. You might lose the whole thing if you don't have a backup plan.

Best,

-Slashy

I think building a pressure column will exceed my abilities and I actually could roughly calculate the pressure if I had altimetry-data.

So how to get it if not via GPS?

Edited October 5, 2015 by MalfunctionM1Ke

[MalfunctionM1Ke]

Just a bump, maybe this gets to someones Attention

[K^2]

A while back, I've seen some "unlocked" GPS units from China. These don't have normal altitude/velocity limits and will continue to report position and altitude with precision of a few meters. I would strongly recommend finding one of these.

For pressure, just find a lab-grade sensor. They have enough precision. The trick is that you might end up needing a heater to keep it operational. Same might go for much of your instrumentation. In general, I would recommend housing electronics well insulated, leaving just a narrow channel for pressure sensor.

[MalfunctionM1Ke]

A while back, I've seen some "unlocked" GPS units from China. These don't have normal altitude/velocity limits and will continue to report position and altitude with precision of a few meters. I would strongly recommend finding one of these.

For pressure, just find a lab-grade sensor. They have enough precision. The trick is that you might end up needing a heater to keep it operational. Same might go for much of your instrumentation. In general, I would recommend housing electronics well insulated, leaving just a narrow channel for pressure sensor.

Thx K²

but i dont want to use a foreign System over its public limitations. "THEY" might come searching for me afterwards

Also I dont want to throw 200€ for lab-graded Equipment at the Project.

I was thinking about a way to get any indicator like, i am approximately at this altitude so my atmospheric density should be "this" and so on.

[Armchair Rocket Scientist]

A mechanical or electronic barometer isn't going to be sensitive enough to register such low pressures, but a pressure column could do it.

https://www.chem.wisc.edu/deptfiles/genchem/sstutorial/Text9/Tx94/tx94p1.GIF

You would have to keep it vertical and not jostle it around too much. Just set up a scale next to the column and take pictures every now and then. Also, the fluid doesn't have to be mercury. You just want something that will remain fluid throughout the flight. I think ethylene glycol (automotive antifreeze) would do nicely.

Best,

-Slashy

There are plenty of altimeters designed for amateur rockets that will read up to 100,000 feet with barometric sensors. Note: Don't use these on a balloon. They have high sampling rates (meaning they probably won't record hours of flight) and use accelerometers to detect a launch: the gentle ascent of a balloon probably wouldn't do much. You should be able to find Arduino-compatible pressure sensors with that resolution.

I'd also advise asking this question on DIYDrones or another amateur weather balloon forum: they'll be much more able to help you than this forum.

[magnemoe]

It the GPS really an problem, ok it cut out at 20 km, but why does it stay off for 15 minutes and how is it done? yes my guess is to avoid someone using it for guidance for an missile

However the parachute will use time to land and even if it use less than 15 minutes it will give you some location based on base stations then have it call back 10 minutes later with gps data.

[Shpaget]

You get a permission from your local aviation authority, file a flight plan and relevant flights are advised of the situation.

Hundreds of thousands of balloons are launched each year.

[Shpaget]

I can't speak for other countries but here in Croatia, approvals are given by Air Traffic Control. It is regulated and the law has clear wording for such flights. There is no need for such specific details you are talking about.

Those approvals are meant for private individuals whose cats are in no danger.

[andrewas]

I can imagine me coming to local aviation authority office with such a request. I'd probably never see my cats again.

Google for weather balloon regulations in your country, theres probably a procedure for it. It may be intended for scientific research rather than Joe Average who wants to send a camera to the edge of space for fun, but you could probably apply for permission easily enough if you wanted to.

And "flight plan" for the amateur balloon? You need to know exact ascend velocity as function of time or altitude, or you cannot use predicted wind velocities at all altitudes to calculate exact flight path. Same for return trip.

The important part is the time and location of launch, and you are required to ensure the balloon is visible to radar. That means air traffic control can identify it, track it and direct traffic around it if necessary.

[Shpaget]

Visible to radar? That would require a transponder, quite a costly device that would reduce the altitude and increase power usage.

[andrewas]

Or, a simple reflector. They know where and when its launching, so they can tag it immediately and track it till it comes down.

[Shpaget]

ATC relies primarily on secondary radars which require a transponder.

Primary radars have become secondary at best.

[MalfunctionM1Ke]

I work on an aiport here in Germany. Maybe not in the ATC itself but I am pretty sure that I can get an approval from the LBA and the local ATC pretty easily because there also Schoolprojects that send up Weatherballons.

You could, of course, run into trouble if you send up a weatherballon without any approvals or notice to the ATC however because you are violating national and international airspace.

In the case that your ballon hits a house, a car or you need the local forestry because your Thing gets stuck in a tree an ordinary personal liability insurance will do.

[wizzlebippi]

ATC relies primarily on secondary radars which require a transponder.

Primary radars have become secondary at best.

When anything in the air is painted with radar, and is big enough and moving fast enough to not be filtered out, that's a primary target. A secondary target is when an aircraft has a transponder that the radar can interrogate, and the transponder can issue a mode C (minimum of altitude encoding) or better response.

A weather balloon, regardless of if you equip it with a reflector or not, probably won't appear on ATC radar because of it's atypical path, smallish size and slow speed. You need to contact ATC with a time and place for the launch well ahead of time (at least a day) so they can route traffic around you. Don't be surprised if they require you to launch from a specific location to avoid airways.