Balloons

For each balloon we launch, we need to design and assemble a payload and attach it to a suitably-sized parachute and balloon. This post covers the design and implementation of each Casa de Balloon payload.

For technical details about how how we designed our payloads and sized our balloons and parachutes, take a look at the How to Pack and How to Fly blog posts.

Table of Contents:



Launch 1: "Learning Launch"


Launch Goal: Get our feet wet with small, light, simple payloads. This was our very first launch — we weren't even sure this would work!

Basic Balloon 1


Bill of Materials:


Notes:
  • The Z992 GPS was not reliably acquiring a fix, so we had no tracking during the flight.
  • We accidentally under-inflated the balloon and had a 3-4 hour flight as a result, instead of the ~2 hour flight we expected.
  • Our app failed to reacquire a GPS fix on the ground, but Android Device Manager checked in and helped us locate our payload.




Basic Balloon 2


Bill of Materials:


Notes:
  • This worked magnificently!
  • As expected, phone GPS only tracked up to 60k feet.




Takeaways






Launch 2: "Fancy Photography Launch"


Launch Goal: Bigger balloons, heavier payloads, better cameras, and radio tracking. This was the first launch in which we used real cameras rather than relying on camera phones. We also tried radio tracking on this one (in parallel with phone GPS).

Basic Balloon 2


Bill of Materials:


Notes:
  • Overinflated. It burst at a lower altitude, resulting in a shorter flight.
  • We'd been including the toe warmers to raise the temperature in the payload (for better battery life and electronics functionality), but this time we suspected they were the cause of condensation on the phone camera lens.




GoPro Balloon


Bill of Materials:


Notes:
  • We forgot the toe warmers on this one, but it didn't make a difference.
  • We lost GPS radio signal after a couple minutes (using standard 1/4 wave antennas on TX and RX).
  • We had two parallel methods of GPS tracking — the radio signal, which was only sending out a signal and not logging GPS data locally (and which signal we lost), and the phone GPS, which stopped above 60k feet.




NEX-3N Balloon


Bill of Materials:


Notes:
  • Also forgot the toe warmers on this one, and it also didn't make a difference.
  • Also lost the GPS radio signal after a couple minutes (using standard 1/4 wave antennas on TX and RX).
  • Five lightly-used Ultimate Lithiums worked fine in the NEX-3N, but five new ones produced too high a voltage and the camera refused to operate. We had to swap out new ones for used ones right before launch.




Takeaways


  • Photos and video from real cameras look amazing! So much better than phone cameras.
  • Ditch the toe warmers. They add no value and potentially cause condensation problems.
  • Have to use better antennas for radio tracking.
  • Should locally log GPS results from the radio tracker so we can retrieve that data later.
  • Put a voltage regulator for bigger cameras instead of relying on "close enough" direct battery power.




Launch 3: "Sunrise Launch"


Launch Goal: Capture a sunrise! This was a dawn launch. We also used better antennas for the radio tracking in the hopes of not losing the signal this time.

NEX-3N Night Balloon


Bill of Materials:


Notes:
  • The 6x battery holder was very loose, and the batteries popped out upon landing impact.
  • The uBlox GPS stopped tracking above 60k feet.
  • Ground tracking with a 433MHz Yagi antenna worked amazingly — we never lost radio contact.




EOS-M Night Balloon


Bill of Materials:


Notes:
  • The MagicLantern custom intervalometer module failed to override camera auto shutter settings (despite it working previously in a test run).
  • The camera batteries also popped out on landing impact.
  • The lid to camera box was lost.
  • The uBlox GPS also stopped tracking above 60k feet.
  • But radio tracking worked perfectly in this balloon as well!




Takeaways


  • Morning twilight photos are the best!
  • Use more tape on everything. Batteries, lids, EVERYTHING.
  • Test custom camera firmware modules over and over again.
  • Read the GPS module datasheet and make sure it's set so it will default to "Airborne" mode (in order to track above 60k feet).
  • Directional Yagi antennas rock and make for awesome stormchaser-style live tracking.




Launch 4: "Back to Basics Launch"


Launch Goal: Push our Android phones to the limit! In every other launch, the phone GPS had stopped working at the 60k-foot altitude limit. This was the first launch in which we used our patched Android phones to get around this. On this launch, we hoped our phone hack would allow us to track up to 100,000 feet!

Balloon Chuva


Bill of Materials:


Notes:
  • The GoPro Hero 4 overheated and stopped recording after 5 minutes (long before the payload was even launched), so we got no usable footage.
  • The iRulu U1S (Mediatek chipset) stopped tracking above 60k feet. 
  • Everything else worked as expected.




Balloon Virgina


Bill of Materials:


Notes:
  • The GoPro Hero 4 also overheated.
  • The Nexus S refused to boot with fresh batteries. We had to boot off used batteries and then hot-swap fresh batteries using parallel packs.
  • The Nexus S patched GPS drivers worked flawlessly and tracked up to 100,000 feet.
  • The GPS Tracker logged inconsistently, possibly because it was sharing a power bus with phone.





Balloon Juan


Bill of Materials:


Notes:
  • The GoPro Hero 4 also overheated.
  • The Samsung GC100 Galaxy Camera patched GPS drivers also worked flawlessly and tracked up to 100,000 feet.
  • The GPS radio tracker also logged inconsistently.




Takeaways


  • Android hardware is amazing!
  • The patched binary GPS drivers are awesome and make for the perfect balloon tracking payload.
  • The GPS Trackers should have dedicated power supplies.
  • GoPro Hero 4 Blacks are trash — we now refer to them as NoGos because of their total failure. 




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Leftover Helium



WARNING: As mentioned in Safety First, please note that inhaling helium is dangerous and can result in injury or death. We do not promote inhaling helium, but if you do, be safe:
  1. Never inhale helium from the tank (or any other pressurized source) as it could damage your lungs, killing you instantly. We partially fill a practice balloon with excess helium and then inhale from that balloon.
  2. Do not take more than one breath of helium at a time. After an inhalation, breath air normally for a few minutes.
  3. STOP if you feel lightheaded!


At the end of a launch, sometimes the helium tanks aren't completely empty, and so we experiment with altering our voice using helium. Since it is lighter than air, it changes the resonate frequency of your vocal tract and therefore the timbre of your voice.

Here, for your viewing pleasure and amusement, we present the results of our experiments:












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Photography

One of our biggest motivations in establishing the Casa de Balloon Club was to get our very own pictures from the edge of space! Most of our photography is done using either cell phone cameras or low-end mirrorless compact cameras.

First Launch


Our first launch outing just relied on the cameras built into cheap Android phones:




As we learned, the secret to balloon photography is the same as the secret to all photography — take a ton of pictures and only show the good ones!

The biggest challenge with shooting from balloons is that we really have no control over orientation, so most of our photos end up looking like this:





But sometimes the horizon lines up just right, and we get a beauty:



Second Launch


Armed with the confidence that we knew how to both launch and recover balloon payloads, we decided our second launch outing would feature bigger, heavier, better cameras.

On one of our payloads, we used a GoPro Hero 3+ Black pointing out the side and set to 4K 15fps. In order to make it work, we had to mod the GoPro to run off Energizer Ultimate Lithium AA batteries.

This was done by splicing a 3xAA battery holder into into a GoPro AC coupler:



We also used high-quality Sandisk Ultra 64GB microSDXC cards because we'd hate for a faulty memory card to ruin our day.

The resulting video looked awesome, especially with the wide-angle lens of the GoPro!


We also got a pretty good sense of just how much motion one of our payloads undergoes during launch, ascent, and descent.

Our other payload contained a Sony NEX-3N mirrorless camera with a Sony 16mm f/2.8 pancake prime lens. We chose this particular camera because it was one of the cheapest and lightest mirrorless cameras that supported an external intervalometer. For lenses, we wanted the widest lens we could get that was still reasonably cheap and light, thus the Sony 16mm f/2.8.

 Sony NEX-3N camera with Sony 16mm f/2.8 pancake prime lens

One of the biggest challenges for us was not really having any idea what the appropriate exposure settings were for high in the atmosphere. Given that it was bright daylight, we decided to shoot in shutter-priority with 1/2000 second shutter speed and ISO-200, and let aperture vary to set exposure.

This worked out pretty well:




Most of our pics ended up with aperture settings of f/5.6 to f/8. We shot in RAW+JPEG format and had plenty of space on our 64GB Sandisk Ultra SDXC card.

The other big challenge we had is actually triggering the photos. Frankly, it's inexcusable for any camera these days to not have an intervalometer built in, but with the Sony, we had the next best thing — a terminal to hook up an external intervalometer.

That particular intervalometer was designed for terrestrial use, and is rather big and clunky for what it actually does. The way most SLR/mirrorless intervalometers work — including this one — is that they have 3 wires: focus, shutter, and GND. Normally, focus and shutter wires are held floating/high (5V). To take a picture, the intervalometer first brings the focus wire low/GND, then pulses the shutter wire low/GND, and then brings the focus wire back to floating/high (5V).

We decided to cut the end off the intervalometer and wire it up to an arduino with a simple sketch.


We did not place any filters on the camera. Though we would be risking damage to the front element of the lens in a crash, we also avoided potential issues with condensation. Since the lens was cheap, this was an acceptable trade-off.

Third Launch


Feeling good about our newly acquired near-space photography skills, we decided our third launch outing would tackle an unreasonably complex photography goal: capturing a sunrise from the edge of space!



We set a target launch time of one hour before sunrise so that our balloons would be way up high before the sun made its appearance.

Photography is all about trade-offs — balloon photography even more so. We wanted to get decent photos of the ground during both twilight and sunrise, which is a very wide range of exposure conditions. We wanted the biggest sensor and fastest wide-angle lens we could find, but had to remember that there was a good chance we would never see the equipment again. Also, heavier cameras and lenses meant more helium and bigger balloons, driving up total launch cost.

After much online research and reading many reviews, we decided to try two different payloads. The first was our trusty NEX-3N + 16mm f/2.8 lens, but with the addition of a 0.75x wide-angle converter. We kept the camera in shutter-priority, but changed the shutter speed to 1/500s and auto-ISO (capped at 3200). We also decided to switch to continuous-shutter mode and enabled auto-exposure bracketing (+- 0.3 EV) with a center at -0.3 EV.

We modified the arduino intervalometer sketch to hold the shutter line low for two seconds. This triggered a burst of three shots — one at -0.3 EV and two bracket shots at -0.7EV and 0EV. We found the best shots were either at -0.3EV or -0.7EV.

Center Exposure (-0.3 EV)

Low Bracket Exposure (-0.7 EV)

High Bracket Exposure (0.0 EV)


Of course, with these settings, we captured nothing but darkness for the first half hour of flight:




For our second sunrise camera, we decided to try the Canon EOS-M paired with a manual-focus manual-aperture Rokinon 12mm f/2.0 lens. It's neither the lightest nor the best mirrorless camera available, but it has one very unique quality: thanks to the efforts of the team at Magic Lantern, it's fully programmable. This meant we would be able to experiment with many more combinations of ISO and shutter speeds to see what worked best for low-light ballooning.

Unfortunately, the EOS-M port of Magic Lantern is still a bit rough around the edges, and one of the main things it lacks is support for a simple script interpreter. Which meant if we wanted to program it, we'd have to be compiling and loading our own binary module — wooooo!

This sounded like an intimidating task, but the Magic Lantern community forums were super helpful and had a great guide to get new developers started.

With a weekend of hacking, we had our very own custom intervalometer module which seemed to work great, cycling through five different shutter speeds (1/4000, 1/2000, 1/500, 1/250) with auto ISO (capped to 3200) to cover our full range of shooting situations.

This module worked great when bench-testing sunrises and sunsets on the ground. But unfortunately something changed between our ground tests and launch day, and though the intervalometer script ran perfectly, the camera simply ignored the shutter settings and chose to set them automatically. As a result, most of our photos were exceptionally blurry:



Sometimes we got lucky, though — this shot wasn't too bad given a 1/20s shutter:



We also learned that sunrises themselves are exceptionally hard to capture because of the ridiculous dynamic range necessary to capture a dark ground and a sun peeking over the horizon. In most cases we just saw pretty abstract color patterns rather than anything resembling landscape.



We also had to deal with a ton of lens flare on both cameras — shooting into the sun is not easy!




But despite all these challenges, we learned that the absolute best view of the California landscape comes during twilight hours. Look at the way the light highlights the texture and colors of the ground:



Fourth Launch


Our fourth launch focused less on photography and more on improving our tracking software and system. But we still got some great photos from all of our phones as well as our one Android-equipped camera.




We were hoping to get some awesome video from this launch by putting a GoPro Hero 4 Black in each payload, all running at 4K 30fps. We equipped them with 3x sets of battery packs and 128GB SDXC cards, which provided up to 6 hours of continuous recording in our ground tests.

Unfortunately, one thing our ground tests didn't take into account is that the GoPro Hero 4 Black has a terrible overheating problem, which makes the 4K 30fps mode unusable for anything other than short bursts. After running into this problem the hard way with three payloads' worth of missing footage, we learned that this is a known issue. The fix according to GoPro is simple — "only use the camera for short clips", thus leading to the nickname "NoGo Hero 4 Black".

Future Launches


We have many more photography-related experiments for upcoming launches, including:
  • Fix the Magic Lantern module and get some quality sunrise or sunset shots
  • Add an IMU (gyro/accelerometer) to the intervalometer Arduino and program it to trigger photos only when level or relatively motionless
  • Try to stitch together 360-degree panoramas
  • Experiment with live-streaming FPV
  • Try out a lightweight gimbal

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#StarbucksSelfies

We inadvertently started a tradition of taking selfies at whatever Starbucks we'd stop by for breakfast on the way to our launch. We started hitting up Starbucks not because we are addicts — in fact, very few of us even drink coffee — but because it was the only thing open at 4:30 am in Los Banos.*

So, for your viewing pleasure, here are our super early morning, pre-launch selfies!


Launch 1
Launch 2
Launch 3
Launch 4

Launch 4, with the full film/drone crew!

*We in fact feel a little bad for waiting at the front door for the Starbucks for them to open at 4:30am on the dot...we don't think they actually expected anyone to show up so early. Thanks for serving us so early and allowing us to do our pre-dawn launch!
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Launch Crew

It takes a team to launch a balloon, so picking your launch and recovery team is important!

At minimum, you need three people to launch the balloon:


It is helpful to have a fourth to read off the handy Balloon Launch Checklist that Aether Industries includes with their Balloon Inflation Tube & Scale.



Aside from the four launch people (Helium person, Lift Person, Balloon Person, and Checklist Person), having another person around to take photos and generally be helpful is nice, but not required.

You only need two people to recover the balloon (because you should never go alone — safety first!), so if some launch crew members need to leave before recovery, that's okay. But recovery is the most exciting part!

Since it is usually a long drive out to the launch and recovery site, we try to make a fun day of it, with our post-launch celebratory orange juice and post-recovery snack and picture-viewing party.


Post-launch celebratory OJ!

Post-recovery ice cream and picture viewing.


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How to Fly

In order to send your payload to the stratosphere and get it back, you need three things:
  1. A lighter-than-air-gas — to pull your payload up. We recommend helium since it is the lightest gas that is not flammable.
  2. A weather balloon — to contain the helium during ascent and eventually burst, allowing the payload to descend.
  3. A parachute — to slow the decent of your payload.
To determine how much helium you need, what size balloon to use, and which parachute is appropriate, you need to decide your:
  1. Payload weight
  2. Flight time
  3. Maximum altitude
  4. Ascent rate
  5. Decent rate
  6. Budget
  7. Landing zone
There's no one correct choice; each of these decisions results in trade-offs.

For example, if you want to carry a heavy payload, you will need more helium — which results in needing a larger balloon and bigger budget. If you want a higher maximum altitude, you will need a larger balloon that is not over inflated (so that it does not pop too low) — but this could result in a longer flight time. Everything is interdependent.

For most launches, we optimized our payload to be as light as possible, have a flight time of ~2-3 hours, and have an ascent and decent rate of ~5m/s. This determined our maximum altitude. For one launch we optimized to break 100k feet, and that affected our flight time and budget.

The two most important tools you will use as part of planning are both freely available courtesy of the amazing folks at Cambridge University Spaceflight and UK High Altitude Society:


Payload Weight


In general, make your payload as small and light as possible. The smaller and lighter it is, the cheaper it will be and the more options you have with everything else. That said, we generally engineer our payloads first, weigh them, and then treat that weight as a constant around which balloon, helium, and parachute have to be optimized.

We highly recommend using a digital postage scale or kitchen scale.

Balloon Size and Helium Volume


The two parameters of balloon size and helium volume combine with your payload weight to determine almost everything about your flight: ascent rate, max altitude, and flight duration. In general, bigger balloons can go to higher altitudes before bursting. More helium causes balloons to rise faster, but also results in lower burst altitudes and shorter flight durations.

You can fiddle with the exact trade-offs using the CUSF Balloon Burst Predictor.





Balloon


Depending on our launch goals, we try to pick the smallest balloon and least helium that will give us 27000m burst altitude and ~5m/s ascent rate.

The predictor linked above supports a number of different balloon manufacturers, but we strongly recommend going with Kaymont Totex weather balloons.





Helium


Helium is available for rent at a number of local places, including party supply stores. Make sure you get pure helium and NOT 'balloon gas'. Some party stores only sell balloon gas, which is only 10% helium. Out here in San Francisco, we rent our helium tanks from the fine folks at SF Party.

When practical, we also round our helium volumes to line up with the available tank sizes. This means we often launch with 55 cubic feet, 88 cubic feet, 110 cubic feet, or 143 cubic feet worth of helium. When inflating, it's much easier to completely empty a tank into the balloon than to try to estimate helium volume from buoyancy after only using a partial tank.

Parachute Size


Parachute size controls one simple variable: descent rate. Parachutes are generally light enough to have negligible impact on overall weight, and thus have minimal impact on the ascent parameters.

We recommend using the Model Rocket Parachute Descent Rate Calculator and entering your payload weight as the rocket weight. We choose a parachute size that gets us roughly a 5m/s descent rate.



We prefer to use parachutes from Spherachutes and pay a bit extra for the weather balloon attachment in the vent.


Landing Zone


Once you have a rough idea of your ascent rate, burst altitude, and descent rate based on your choice of payload, balloon, helium, and parachute, it's time to pick a launch spot and predict a landing spot using CUSF Landing Predictor. To read more about how to pick a good launch and landing spot, read our Location blog post.



Weather predictions change daily, so we only take them seriously starting a day or two before our target launch date.

In general, if winds are not conducive to a landing in a large safe zone (+/- 5 miles), we will abort the launch rather than fiddle with the launch parameters. But if we really need to do a launch for some reason, we can always adjust the target landing site by either over-inflating the balloon (increasing ascent rate, lowering maximum altitude, and shortening flight duration) or under-inflating the balloon (decreasing ascent rate, raising maximum altitude, and increasing flight duration).
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How to Pack

Packing a balloon payload is part engineering and part art. Your goal is to cram as many bits into as little size and weight as possible, while still making sure everything is snug and secure.

Foam Box Payload Container


We prefer to engineer our payloads around foam mailing boxes like these.



These are pretty pricey to buy brand-new, but can often be found in trash and recycle piles in the hallways of most biomedical research facilities. Ideal boxes are small and 1/2" to 1" thick. Just use common sense, caution, and Lysol.

Of course, a camera sitting in a foam box is no fun unless there is a hole for the lens. You can use a hot knife to cut lens holes in the sides of the foam box and then line up the cameras and phones to give unobstructed views.


To secure everything inside the payload box, we use custom-cut foam blocks to cross-brace, and then we tape everything down with either packing tape or double-sided foam mounting tape. Your payload should be secure enough that nothing moves even if shaken vigorously.



Phones


See our tracker section for more details. In each payload we include at least one phone running our tracker app. We've learned that it's best for the tracker phone to be on its own power supply.



Phones we're happy with:
Phones we're bench-testing:
Phones we're not thrilled with:
  • ZTE Z992 - GPS was flaky
  • iRulu U1S - GPS worked okay, camera was terrible for the price

Photo Cameras


We love having nice cameras in our payloads, but we totally understand if you're hesitant to send $500 worth of equipment off to a place where it might never be recovered again.



Cameras / lenses we're happy with:
Cameras / lenses we're bench-testing:

Video Cameras


Few things are more awesome than a balloon launch video. Action cameras such as the GoPro are the only way to go.



One thing to note — the wide angle lenses of most action cameras are surprisingly wide, which means you're carving out a rather wide cone in the foam to make sure the lens has an unobstructed view.



Action cams we're happy with:
Action cams we're bench-testing:
Action cams we're not thrilled with:
  • GoPro Hero 4 Black — the only reason to pay extra for this camera is for 4K 30FPS recording — unfortunately the camera can't record for more than a couple minutes in that mode without overheating and shutting down, making it useless for balloon purposes.

Batteries


Most of the electronics in your payload normally run off rechargeable LiPo batteries rated for either 3.6V or 7.2V. Unfortunately, these batteries stop working at high altitudes / low temperatures, causing the devices to lose power and stop working. This is the #1 reason most other amateur weather ballooners have lost contact with payloads.

We strongly recommend removing the LiPo battery packs for all electronic devices, and replacing them with packs of non-rechargeable AA-sized Energizer Ultimate Lithium L91 batteries wired in series.



A 3.6V LiPo can generally be replaced directly by three AA lithium batteries wired in series — we use 3xAA battery holders like these. 



A 7.2V LiPo can be replaced by six AA lithium batteries wired in series and run through a switching voltage regulator set to 8V like this one.


Some devices, if insulated well, will generate enough heat to keep the original rechargeable LiPos operational for the entire duration of the flight — GoPros inside their waterproof cases are pretty good about this. But we still prefer switching batteries just to be safe.

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