High-altitude balloons are unmanned balloons, usually filled with helium or hydrogen, that are released into the stratosphere, generally attaining between 60,000 to 120,000 feet (11 to 23 mi; 18 to 37 km). Such a flight allows for the collection of an enormous amount of interesting scientific data. For our balloon, we chose to measure Barometric Pressure, Relative Humidity, Temperature, Battery level Voltage (to see the effects of temperature on battery life), Altitude, and Radiation (measured in CPM, count per minute). Out of all of these measurements, we found radiation to be the most interesting, as there was a HUGE difference in the radiological readings obtained on the ground versus those taken as the balloon increased in altitude. Finally, we also took 1080p video of the flight, using a GoPro HERO 4, which provided some amazing footage of earth from near-space altitudes.
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Step 1: Basic Flight Materials Overview
The design of our high-altitude balloon is fairly simple. From the balloon, we have a rope which attaches to the parachute, and then the payload. The payload is constructed out of a standard Styrofoam cooler, painted bright orange for visibility. Inside the payload we have our sensors, including the GoPro, and hand warmers in order to keep the electronics from dying in the cold temperatures.
Step 2: Flight Predictions
One of the most important steps in launching the balloon will be your flight predictions. We found that flight predictions would wildly vary. Sometimes our payload would end up in Arizona, other times only 20 miles away.
We used the predict applet of Habhub.org to get flight path estimations for our balloon:
- Select your Lat/Long on the Map.
- Pick a rough altitude for your launch, we found a suitable location (parking lot of an elementary school) prior to running the calculator.
- Pick Date/Time Accurately
- Keep Ascent Rate as reflected, and Burst Altitude.
- (If you used Project Aether's 36 inch parachute) Put descent rate as 15mph, or 6.70m/s.
Step 3: Payload Vessel Construction
At the bottom of our styrofoam cooler, we have carved a hole in order for the GoPro lense to stick out. Alternatively the hole could be carved in the side of the box, which would allow for a different perspective of the flight. We also made holes to access the record and power buttons. The GoPro is equipped with a “BacPac” which extends the battery life. In addition, we included a external battery back composed of six lithium AA batteries. It is important to use lithium batteries as lithium-ion batteries take a massive performance hit in cold temperatures. The GoPro is secured in place with duct tape and a zip tie which goes through the styrofoam box.
Next to the GoPro, a GPS tracker would be installed. The exact specifications of the tracker we used can be found (and it can be bought) here: http://www.byonics.com/mt-aio
This tracker must be configured using a HAM radio callsign. Then, once it is configured, one can track GPS locations sent out from the beacon. We had data access during the recovery mission, so we chose to use a website specifically made for integration with google maps: http://www.aprs.fi
We simply cut a hole in the side of the styrofoam box using a screwdriver (poking might be a more accurate word), where the antenna for the tracker would stick out.
Above both the GoPro and the GPS tracker, we placed the Electronics Sensor Payload, which contained our scientific instrumentation for the flight.
Step 4: Electronics Payload: Selecting Sensors and Equiptment
Inside our payload box, along with the GoPro, we housed our electronics apparatus. This consisted of an Arduino mega 2560, A SparkFun OpenLog, SparkFun Geiger Counter Board, and an Arduino Weather Shield. These were powered by a 6xAA Lithium (NOT LITHIUM ION) battery array which allowed us to keep the sensors powered even at 80,000ft. where the temperature can drop below 0 degrees celsius.
We utilized a Mega 2560 because we needed additional RX/TX to communicate with not only one sensor base (The Weather Shield), but also the Geiger counter, and be capable of pumping out raw data to the open log. So, we needed a total of 3 RX/TX ports, which the Mega 2560 has.
The full-connection of our wiring for the sensors apparatus can be seen in the schematics photo, attached to this step.
Some important notes: The 6xAA batteries are wired in SERIES. The microphone in the schematic, as it is labeled, represents the TX/RX lines on the Geiger Counter board, which should be tied to their respective partners on the Arduino Mega. Be advised, the Geiger Board also needs power, which it gets from the same 5V rail as the OpenLog on the Mega.
We then hooked up the RX/TX to the corresponding wires from the Sparkfun Geiger Counter Board to the Arduino. For the weather shield, all we had to do is simply attach it to the base of the arduino (be advised, it fits the mega perfectly, though it is only advertised to fit with the Arduino Uno R3). Finally, coming out of the last RX/TX ports Arduino, we had the data lines which hooked up to the corresponding RX/TX lines on the OpenLog. NOTE: We made sure to use the RX/TX “0” line (it is labeled as such) on the Mega, so that when we activated our serial console in the Programming, it would use this port to post data to the Open Log. You do not have to use this same line, but make sure the programming reflects this change, as in “Serial.begin()” vs. “Serial1.Begin().”
Here is a list of the aforementioned parts and where we bought them as well:
Arduino Mega 2560: https://www.sparkfun.com/products/11061
Geiger Counter Board: https://www.sparkfun.com/products/11345
GoPro HERO 4: http://www.amazon.com/GoPro-CHDHY-401-HERO4-SILVER/dp/B00NIYJF6U/ref=sr_1_1?s=photo&ie=UTF8&qid=1424842279&sr=1-1&keywords=GoPro+hero+4
Sparkfun Weather Shield: https://www.sparkfun.com/products/12081
Necessary headers (Shield comes without them): https://www.sparkfun.com/products/115
Step 5: Electronics Payload: Powering Equiptment and Getting Data
As stated previously, the power for the majority of our systems came from pure Lithium batteries which can operate in very cold temperatures. However, one exception was the goPro.
The GoPro remained powered via its onboard (extended) battery pac, though we supplemented this through the use of a AA--> USB (5V) adapter as seen here:
We found this was perfectly sufficient to POWER the GoPro, HOWEVER, we did run out of storage just near the end of the ascent due to only having 32gb of storage. Be advised, 1920x1080 resolution videos take up quite a bit of storage on the memory card.
We powered the other sensor systems (which themselves draw power from the Arduino) using this:
We also recommend you consider purchasing a 64GB Micro-SD card for recording video of the flight, and a 16GB for recording data during the flight.
Step 6: The Programming
All programming for this project is done in the arduino IDE, which uses a modified version of C. The IDE can be download from here: http://arduino.cc/en/main/software
The program does the following in psuedo-code:
- Starts serial interfaces (these are the TX/RX pairs on the Arduino)
- begins receiving/sending data on these interfaces, in order to talk with the OpenLog, Weather Shield, and the Geiger counter Board.
- Every 30 seconds, the Arduino will read data from the sensors and post this to the OpenLog where it will be logged as a comma-separated-value text file for later analysis.
- Continue this reading/writing process infinitely.
A link to our code can be found here: http://pastebin.com/B2qWDhf2
If you find yourself overwhelmed with the Arduino syntax, we recommend using the following as a reference and learning source: http://arduino.cc/en/Tutorial/HomePage
NOTE: If you encounter any errors in the code, please make sure you have all necessary libraries installed! Initially we had trouble as the necessary imports and libraries were not installed for the IDE to function correctly (We did our programming in Ubuntu 12.06).
Step 7: Physical Apparatus: the Balloon and the Parachute
In order to get to space (or close) we're going to need a balloon. But not just any, a very special balloon.
We chose a balloon used many times in the past successfully by others who have launched high altitude balloons:
This balloon will allow you to get to 100,000ft. or above.
You will also need a parachute to slow the balloon and payload train (the rope holding everything on it) after the balloon pops when it gets very high! We recommend opting for a well-known parachute especially if this is your first time. We chose a high rated parachute again manufactured by Project Aether, which insured quality.
This parachute worked great for us.
Step 8: Physical Apparatus: the Helium and Regulator
In order to actually fill the balloon so it can fly, we're also going to need helium!
We rented our Helium from AirGas, a company in California. If you are affiliated with a school or extra-curricular organization, as we are, it will be easier to open an account and rent a tank of Helium. We made do just fine with 150 cubic feet of Helium, and had about 40 cu. ft. to spare after filling the balloon.
Also, be advised, you will NEED a helium regulator in order to safely operate the helium tank and fill the balloon. Although the balloon could in theory be filled without the regulator, there are numerous stories of this going badly very fast, as the helium tank is essentially a rocket just waiting to shoot off, you can imagine there is serious potential for injury. The company you are renting the helium from will provide you with a regulator, sometimes with extra cost, sometimes included in the price.
Step 9: Packing the Payload Vessel
Packing the payload vessel is an essential step as it ensures that the payload instrumentation will remain secure throughout the flight.
The GoPro was mounted looking through the bottom hole in the box as already discussed, and was secured in place using a zip tie and duct tape.
The MicroTrack AIO was set adjacent to the GoPro, horizontally, with the antenna facing outwards.
On top of this, we had a small cardboard box that fit snugly in the top of the styrofoam box, which contained the Arduino mega 2560, Geiger Counter Board, Weather Shield (attached to the Arduino, of course), and OpenLog. This layout can be seen in the schematic depicted on the graph paper.
NOTE: Over each item, especially focusing on the Arduino and GoPros, we added many hand warmers (oxygen activated) just before launching the balloon in order to keep the equipment warm as it reached near space.
Finally, on the outside of the payload vessel, make sure to put some identifying information that shows where the payload is from and who to contact if it is found! We also chose to mention the possibility of a cash reward!
Step 10: Assorted Items for Launch & Recovery
In order to have a smooth launch and recovery, you'll also need the following:
- A large tarp, on which to inflate the balloon.
- A 25lb weight, or around there, to hold the balloon to the ground once its been filled.
- Some other weights or people to stand on the tarp and prevent it from flying off.
- A offroad vehicle
- Snacks for recovery
- Cellular Data access (not 100% needed, but very helpful)
- Latex Gloves
- Extra handwarmers and extra batteries
Step 11: Finding the Optimal Lift
In order to have a successful flight, it is essential that you fill the balloon with sufficient helium such that the balloon will have enough lift to ascend relatively quickly, but not too much as to cause the balloon to pop prematurely.
We used the following technique to properly gauge the lift for our balloon:
- Mass the entire payload (with everything inside) and the parachute.
- Multiply this number by two.
- Fill sandbags such that some are 0.5kg, and others 0.2kg.
- Adjust the sandbags until you have roughly twice the mass of the payload (this is the lift we chose, and we reached 80,000ft.)
- Rope or Zip-Tie these together, such that they are connected to the neck of the balloon.
- While filling the balloon, make sure to stop filling once the balloon successfully lifts the sandbags such that its total lift (aka nominal lift) is roughly double the payload mass.
Step 12: Filling the Balloon
Filling the balloon is a relatively straightforward process, but is important for safety reasons to ensure everything is done properly.
If you are confused at any point in the procedure, we also found it helpful to refer to the following videos that show practically how inflation takes place:
We utilized the following procedure to fill the balloon.
- Lay out CLEAN tarp on ground where balloon will be filled. Place rocks or weights on the corners to stop it from flying away in the wind.
- PUT ON LATEX GLOVES. DO NOT TOUCH THE BALLOON WITHOUT GLOVES!
- Clean the output tube from the regulator with rubbing alcohol.
- Slip the neck of the balloon over the CLEANED output tube from the He regulator. Zip tie this connection multiple times.
- Attach weights/sandbags (calibrated to TWICE the payload weight) to the neck of the balloon via string and zip ties.
- Turn the dial on the regulator and begin the flow of He into the balloon.
- Once the balloon reaches sufficient lift, tie the balloon off with multiple zip ties, being sure to fold the balloon neck on over itself multiple times to prevent any leakage.
- Put a weight to hold the balloon down to the tarp, and prepare payload/parachute for attachment to the main line. (AKA Lift Train)
Step 13: Attaching Payload and Parachute
The attachment of the payload and the parachute is also known as the attachment of the Lift Train, which consists of the payload box (in our case a Styrofoam box) and a parachute from Project Aether.
The parachute from Project Aether comes with some Carabiners, which will be used to attach to the lift train.
We used the following procedure to attach and secure the Lift Train:
- Attach the main flight string around the tied off neck of the balloon.
- Leave a significant amount, perhaps 25ft, of rope left to attach the payload and parachute.
- Make one knot in the main flight string, than attach the first carabiner from the parachute above this knot, so it rests on it. Attach the other carabiner somewhere below this knot.
- The remainder of the lift train rope can be used to attach to the payload box. We chose a "box-sling knot" to attach this, though any kind of knot that securely envelops the box will be acceptable for flight. A picture of this kind of knot can be seen in the photo with one of our members holding the payload box.
- Add duct tape and extra loops around the payload box to ensure its integrity during flight, and of course its attachment to the main lift train.
Step 14: Launch Checklist (HAVE ONE!)
One of the most important parts of the balloon launch is having a THOROUGH launch day checklist. The Launch day checklist should essentially be a summary of every step needed to launch the balloon and payload successfully. Make sure its followed exactly, especially pertaining to the electronics and sensors portion. Luckily, we followed the launch procedure to the letter and were able to ensure everything was properly turned on and running prior to releasing the balloon into flight.
Our check-list can be found here (its fairly long):
Feel free to use this same checklist, most of the items will probably still apply to you.
One piece of advice, if you are using a video recording device like the GoPro and not a Canon Digital Camera or something modified to take pictures in space, you do not need to worry about setting the focus to zero as described in the checklist.
Step 15: Launch Time!
At this point, you should be have the balloon filled, tied off, with parachute and payload securely attached to the Lift Train! All that's left to do is let it go!
Don't be surprised if the balloon ascends extremely rapidly! Our balloon took off very fast and this initially caused us to worry about how much helium we put inside (remember, the more helium added means the sooner it will pop).
Your flight time will probably be around ~2 hours. Our team went out for a nice breakfast and then went to the estimated landing
Here is our flight video (in glorious 1920x1080)
Step 16: Track It!
The time has come, the balloon and payload are now in the air, all thats left to do is track it!
For us, we had a fair bit of anxiety, as our Microtrack was not registering any data until halfway through the flight! This may have been due to a very fast ascent rate, as commercial GPS chips will not work above a certain altitude, due to nuclear weapons concerns.
We used the site http://aprs.fi/# to track our flight path since we were able to maintain almost consistent 3G access throughout the trip. If you lose data or cellular service altogether, REMEMBER to archive maps (set them to 'offline mode') prior to the loss of service. Then, using the latitude and longitude coordinates provided by aprs.fi, you can find the location of your payload utilizing the GPS chip inside your phone, that continues to work despite the fact that you don't have data or cell service.
Step 17: Recovery
Now comes the moment of truth! If you ran many simulations and have a general idea where your payload is going to land (and this isn't in the ocean) you should be in good shape. For us, our payload landed about 10 miles away from the estimated landing site.
One of the most difficult aspects of the recovery process is navigation. Most likely, depending on where you launched from and your estimated flight path, you will have to be taking fire roads or just completely unmarked paths onto private property. In our case, our payload landed on a rancher's land, but he was kind enough to not only allow us access but also guided us to the precise location where our payload was located! Needless to say, we had a photo of near-space printed and sent to him along with a thank you note! Side note, the photo attached in this step is from the ranch land we were driving on, as you can see, without help for navigation, it would have been very difficult to recover the payload (as the
If you do stumble onto an area where there are signs indicating no trespassing, your best course of action is to call the owner (or suspected owner) and just politely explain the purpose of the scientific experiment, and how you merely wish to recover your apparatus from the property. A cash reward might not hurt to mention as well! :)
Step 18: Analyze, Analyze, Analyze!
Now that you've recovered your payload, the most scientific oriented portion of the journey is about to begin. Recover your Micro-SD from the OpenLog and pop it in the computer.
You should see a variety of readings from the weather shield, geiger counter, and other sensors if you chose to use them. What is so nice about these readings is that they are in CSV (comma separated value) format. Simply rename the file to .csv and you can open and analyze the data in Google Sheets.
This data can then be graphed, manipulated, or analyzed in any way you see fit! For our project, we utilized the temperature and pressure recorded by the weather shield to calculate an altitude for the balloon. We found the balloon popped at around 85,000ft.
Attached to this step is one picture of readings we took close to the ground, and then readings taken higher up. You can see a HUGE difference in the radiation (CPM readings) and pressure readings. In fact, there exists a defined slope for the increase in radiation as you go up higher in the atmosphere, and we were able to calculate that rate-of-change based on our data. Without the shielding we have on the ground from the atmosphere, we would literally be irradiated to death (not to mention, as the pressure reached dangerously low levels, our blood would quite literally begin to boil!, how cool is that!!).
Step 19: Concluding the Project
At this point, you should be very proud of yourself, you've successfully achieved a feat of epic proportions, you've sent a device to near-space and back, with relevant scientific data and beautiful video/picture recording to boot!
We created our video using Sony Vegas Pro, and mashing all of the individual segments taken by the GoPro into one continuous video. The same thing could also be done with cheaper software, or free altogether, like Windows Movie maker.
A local news organization even ran a story on our launch! Science rules!
Grand Prize in the
Explore Science Contest