Need help with high altitude balloon

I've been trying to read and understand the topic of high altitude ballooning, but boy is it confusing. I'm trying to coach my kids for a science fair project.

We need:
the balloon, parachute, payload container, 'chute and rigging (check, I understand this)

Here's where I'm confused and really hope you folks are willing to help us out.
I need to build an APRS station. There's something called the Tracuino (SP?) but that's build onto an Arduino, or in addition to it?
I want to track the following info during the flight (3-4 hours):
altitude (if it's not culled from the air pressure)
air pressure

I guess that's really it. I'm looking for someone to help be build a shopping list. What do I need to buy to get this thing off the ground?
Am I making sense?
Thanks for the help.

A most important thing to do is to decide how much everything will weigh. That will determine the size of the balloon and how much helium you need to buy. There are several web sites that will help you estimate everything.

You can buy or build inexpensive APRS trackers. You need an amateur radio operators license and call sign to operate one legally. If there is an APRS repeater close enough to the balloon path and connected to the internet, your tracking data will appear on under your call sign.

Or, you can use a satellite locator such as SPOT. HAB tracking overview.

Check something like this out P17166-ND or MCP9700A-E/TO-ND. Both plug into the analog pins making them really easy to integrate. Can't find any GPS stuff though but I imagine you could send up an old phone with a GPS tracking app.

Digikey is your best friend for finding sensors though it can be tough to navigate.

Good luck

APRS is out unless you or a friend have an amateur license. That's a pity because Byonics have a great range of stuff for exactly what you want. Beware that a lot of their equipment assumes you have a radio.

SPOT or Delorme make good satellite trackers that can be tracked on the internet easily.

The on board Arduino can just log position and sensor data, without trying to transmit it. Use a data logger shield with an SD card. Some have GPS built in. Add a BME280 sensor for very accurate temperature, pressure and humidity.

If you dont have a Amateur Radio License, you cant use APRS.

There is an alternative, you can track the balloon yourself, ground to high altitude balloon, using ISM band LoRa devices.

Easy Build LoRa Tracker

Put a medium yagi on a tripod and point it at the balloon, LoRa will give you around 500kM range at circa 1500bps and 10mW. Even further than that if you reduce the data rate.

And if your following the balloon, assuming you want it back, you can build a portable LoRa receiver that will give you the location of the balloon as it comes in to land.

I would suggest that you store and retrieve, rather than trying to down-link your data in real time. It gets cold in the upper atmosphere, so you will need to insulate and heat your electronics. GPS will get funky above 40000 feet, radio communications will be sketchy at all altitudes. Monitor the high altitude wind speed and direction so you know where it will be. If you use a weather balloon, you will be able to see it up to 100,000 feet if you know where to look.

Temperature and pressure are easy. Get a couple sensors, and save the output to the eeprom, or an sd card.

Position - GPS will work once it has returned to ground. Use a beacon that turns on once it’s down and sends you the location. Trying to keep up with airborne telemetry will be a headache, especially on your first flight! (They have high altitude GPS devices, but they are expensive and not as easy to use as the GTop and UBlox devices that are commonly used in amateur devices. If it gets into your blood, think about investing in one of these, so you can track it in real time.)

Altitude - get an altimeter breakout. It will take T and P into consideration. Record this as well, and read it after landing.

First thing to get is a balloon. A latex weather balloon will get to 100,000+ feet when filled properly. Other balloon stuff is the filling rig - you can use helium or hydrogen. Hydrogen has the advantage of about 20% more lift, and 1/100th the cost. It’s disadvantage is that it is flammable. Once your balloon is aloft, this isn’t a problem. On the ground it requires strict adherence to safety procedures. Every launch I have been part of has used H2.

The next thing is a site. Your balloon can travel some distance. Launch on a calm day to limit it’s range to 10 miles or so. You want to avoid populated areas, air traffic lanes, and restricted airspace. Get FAA approval for your flight if you are in the US.

Design a harness - the balloon goes up, and your device will dangle from a sturdy line. The parachute mechanism also hangs on this line. As the balloon ascends, the pressure and the temperature both go down. Reducing the pressure causes the balloon to expand. Cooling coses contraction. The altitude vs diameter function is complex. Use the real gas law for the lift gas in your calculations. Your balloon will have an approximate maximum diameter. Once that is exceeded, the balloon pops, and the payload drops. If you put baby powder in the balloon before filling, it will leave a white puff in the sky when it pops. It’s about 20 miles up, so look carefully.

Make your capsule - at moderate altitude (40-75,000 feet) it’s 40 below, so everything is going to freeze. Your box needs to insulate your electronics, as well as protect it from a high speed landing and dragging. Put some sort of heater inside. Styrofoam is really good material. Fiberglass with insulation glued on the inside is the best for strength, durability, and (depending on the material and thickness) the best insulator. It is also orders of magnitude more expensive. If you want to reuse your capsule, make it sturdy!

Keep your circuitry and mechanisms simple. When it’s cold it will be brittle, so limit movement, and it will contract and expand considerably. So it should be a bit flexible as well. Power will be an issue because of the pressure and temperature changes. Try to keep the internal temperature (slightly) above freezing, and use solid construction batteries. Remember, if your power fails, so does everything else.

Ublox GPS are the standard used over here in the UK, good to 50,000M and around £10 each.

You folks are very helpful. I posted a similar post for the Pi people and got one response. Thank you all.
I made myself to look more like a newb than I am I guess. I know I have to have the HAM technician license, one of my kids will do that.
I'm going to dig into the links and info you folks posted, thanks again.
[inner newbie coming out] So, the Arduino is a computer, like the Pi, but with flexibility, or maybe computing power? Is that right?
I'll need an arduino board, where do I get temp, altitude, and other sensors?
I'll look into LORA tracking.
I don't know why this is so difficult for me. I guess it's just because I have 0 experience with Arduino and Pi stuff.

I want to express my appreciation again. I'm a part of a big auto racing forum and I know if can be trying when someone comes in asking questions that, to the experienced, are super simple. But this seems like a pretty good group of folks here.

Over here in the UK you cannot use your Amatuer License in 'Airborne' transmitters.

In the US and a lot of other places there are no such restrictions so its common to use APRS for tracking, if you need more range you just use more transmit power. With modern Lithium batteries being light and cheap its not difficult to pack enough power for a 2-3 hour up and burst flight.

In the UK we mainly use ISM band comms at 434Mhz which is license excempt at 10mW only. With such low power you need very efficient comms. Until recently FSK RTTY @ 50-300baud has been used, this is a very long range mode and can be received with most Amateur radio gear or one of the USB SDR dongles that are so cheap these days. The audio from the receiver that is FSK RTTY, is typically fed into a PC, decoded by FLDIGI, and posted across the internet to the Spacenear tracking system. FSK RTTY is one way only comms however.

LoRa is quiet new and has several significant advantages; its easy to implemenent, low cost, very long range, good noise resistance, has two way communication (you can tell your balloon to do stuff, even from 100s of Km away) and can be used at high data rates, downloading pictures live for instance.

The link I posted earlier was for a very low component count LoRa tracker, and you could use the same tracker PCB with the type of Ublox gps module that has an integral ceramic antenna. That tracker will run for some weeks from 2 x AAA Lithium Batteries. Toward the end of the article is a picture of a simple LoRa receiver, its just a shield PCB, LoRa device and Arduino base.

In the US its likley you will use APRS, but you no longer have to as LORa is an easy way of tracking a balloon yourself.

LoRa ... can be used at high data rates, downloading pictures live for instance.

I'm interested in using LoRa, but everything I've read says it is for low data rates.

Can you post a link to a high data rate LoRa TX/RX combination and/or application?

[inner newbie coming out] So, the Arduino is a computer, like the Pi, but with flexibility, or maybe computing power? Is that right?

Yes, the Arduino is a computer but it’s not like the Pi.

The Pi is like a small PC. It has an operating system and you can plug in a screen, keyboard and mouse so you can use it to write email or run a (limited) flight simulator.

The Arduino is more like an industrial controller. It has simple 5V inputs and outputs that you can attach to switches, sensors, transistors or whatever. You can get LCD screens for Arduino but the Arduino has to individually fill in the pixels on the screen like a paint program with a single-pixel brush.

The advantage to using the Arduino is you control everything. There’s no operating system that makes its own decisions at random times. If you need to precisely time the rotation of a motor then you can do that, without the operating system suddenly deciding that it needs to update its disk cache in the middle.

The Arduino environment has been designed to make it easy to get started. You can have a working fish feeder with less than a day’s work. Unlike other starter systems, it’s not a walled garden. You have the ability to use all of the chip’s advanced industrial-control features without throwing away the supporting infrastructure which makes it easy to communicate with the outside world.

I guess it depends on what you mean by 'High'

While LoRa does excel at low data rate stuff, 1000bps and lower, its no slouch at higher speeds and it will go up to 37.5Kbits sec.

I have not tested at that speed, but in a test between ground and a Pico Balloon at 8km altitude, I had comms at 13.7Kbits second at 105km @ 7dBm only, receiving antenna was a Diamond X50N.

Now LoRa devices are capable of 17dBm or 20dBm (50mW or 100mW) depending on the type so at full power you might get the same distance at 37.5Kbits, thats an estimate though.

The UKHAS (UK High altitude society) guys have been experimenting with downloading pictures, see here for instance;!topic/ukhas/siZ99wbRNRg

But its early days yet, still lots of experimenting to do.

13.7 kbits/second is great for telemetry, but a 1 megabyte image would take about 10 minutes to download, minimum. Thanks!

A field I kmow absolutely nothing about - but fascinating.

For curiosity - why does ordinary GPS not work at very high altitudes? - It's closer to the satellites, so could get a (bit) better signal...?



why does ordinary GPS not work at very high altitudes?

By law, in the U.S. There are also restrictions on how fast the GPS receiver can be moving and legally report velocity (about 500 mph).

The U.S. government understandably does not want civilian GPS receivers to be used in guided missiles.

A field I kmow absolutely nothing about - but fascinating.

For curiosity - why does ordinary GPS not work at very high altitudes? - It's closer to the satellites, so could get a (bit) better signal...?



Because they are poorly coded;

Note the important bit;

"In GPS technology, the term "COCOM Limits" also refers to a limit placed on GPS tracking devices that disables tracking when the device calculates that it is moving faster than 1,000 knots (1,900 km/h; 1,200 mph) at an altitude higher than 18,000 m (59,000 ft).[2] This was intended to prevent the use of GPS in intercontinental ballistic missile-like applications.
Some manufacturers apply this limit only when both speed and altitude limits are reached, while other manufacturers disable tracking when either limit is reached. In the latter case, this causes some devices to refuse to operate in very high altitude balloons."

So as long as the balloon is not travelling at more than 1,200mph it is legal for it to report position and altitude, which is what the inexpensive Ublox GPSs do.

13.7 kbits/second is great for telemetry, but a 1 megabyte image would take about 10 minutes to download, minimum. Thanks!

Yes it would, bit longer than 10 minutes I suspect

High bandwidth and long distance comms are available of course, but then you end up needing large dish antennas or long base line arrays, all of which does not come cheap.

However LoRa devices are cheap and can use very simple antennas. If enough were augemented together over a wide bandwith you could up the effective data rate considerably. LoRa devices seem to exhibit a good degree of resistance to interferance to transmissions on adjacent channels, even whent there are two transmissions on the same channel that start at different time instances.

As yet it appears no-one has taken up the chalenge to write the software to see if such an approach would work.

At the very low data rates, the reason why LoRa works so well is that it can receive signals that are -20dB below noise level, as seen by the receiver. Previous low cost ISM type telemetry soloutions, such as the ubiqitous RFM22B\SI4432 were FSK based and needed a postitive SNR to work,

A field I kmow absolutely nothing about - but fascinating.

For curiosity - why does ordinary GPS not work at very high altitudes? - It's closer to the satellites, so could get a (bit) better signal...?



I know others have already answered your question, so I'll add this. This company (Sent Into Space) sells a 'black box' that has all the sensors most folks would want, and, because it's not a U.S. product, they say their GPS will work well, well over 100K feet. I might buy this, and use an Arduino for the LoRa tracker. I'm leaning toward the LoRa tracker because it sounds a bit better.