I’m back after a brief intermission to tell you how to do one of the neatest things I have ever done-flying a camera on a weather balloon into the mid stratosphere, where the sky is black and the horizon is curved.
We are definitely not the first people to do this; in fact it seems like every other day I hear about some high schooler launching a balloon into near space. But when it comes down to it, who cares how many times it’s been done? The pictures are spectacular:
A YouTube video with the photo sequence and some cool music:
Want the individual pictures? Have the entire photo set!
Note: the photos are released under the Creative Commons with Attribution license. If you display the photos for anything other than home use, please caption them with “Courtesy of Bovine Aerospace”.
How to do this yourself
The goal is to get a camera really, really high. You could use rockets, of course, but they are hard to build, very regulated, and have a tendency to explode. There is an easier way, however-just use a really big balloon. Here are the things that have to happen for this to work:
1. You need to lift the camera and protect it during flight.
2. The camera needs to either record video or take photos every so often. We did the latter.
3. The balloon needs to release the camera so you can get it back.
4. You need to be able to track the camera so you can find it again.
5. You need to slow the camera on the descent so it doesn’t smash itself into smithereens.
6. Last but definitely not least, the camera needs to land in the appropriate place (i.e. not water, rough terrain, or a military base). We had some issues with this…
GPS cell phone
Lifting the camera
We used a Canon A530 camera (around $30 used on Amazon) and we used the CHDK package to make it take a picture every 10 seconds. If you are not a programmer, either buy a camera that you can set to take a picture every so often or use a video camera.
We bought a Styrofoam cooler to protect the camera, and we threw in some hand warmers to keep it warm (it gets cold up there…like -90 F). We also had the tracking system in the cooler (more on that later).
We used a 600 gram weather balloon from Kaymont to lift the cooler. You can fill the balloon with hydrogen or helium. We used helium. It’s available from welding supply shops (you can buy 200 cubic feet for around $80, we used about half of that). Hydrogen is cheaper and will give you slightly more lift but it is harder to find and also extremely flammable.
Here we are with our balloon, parachute, and instrument package:
Once the balloon reaches a certain height (75,000 to 90,000 ft, for our balloon), it pops and the styrofoam cooler starts its descent.
You must track your balloon in order to get it back. Otherwise, unless you are extremely lucky and find your camera or someone else finds it and mails it to you, your camera will disappear into the sky and never be heard from again.
There are a couple of ways to track your camera. If you have good cell phone coverage where you expect the balloon to land (see section below on landing prediction), you can use a GPS enabled smart phone with the free Instamapper app. However, if you are concerned that the balloon might land in a place with poor cell reception, use the SPOT tracker. We used both Instamapper and SPOT. The cell phone never answered on the way down, so if we hadn’t had the SPOT we would never have gotten our photos back.
If you are into HAM radio, you could also use radio telemetry. I think there are websites that describe how to do this but I have no personal experience with it.
A styrofoam cooler that falls 17 miles will hit the ground pretty hard. We found this out on the first launch we tried (we think the parachute failed…we never found the camera). So it is very important to slow your falling camera down with a well made parachute. You can buy parachutes online, but my friend and his girlfriend ended up making ours out of ripstop nylon. Here’s a picture of the parachute:
You can use this online calculator to design a parachute that will work for you. I believe that you want your camera to land at less than 15 mph. After our first failure I was very conservative and designed ours to land at 6 mph. As I recall the cooler was undamaged (and styrofoam is pretty fragile!).
If you decide to design your own parachute, you can use this website to make a sewing or taping pattern. I also have a python script that will generate half sphere gores, and when I post it I’ll add the link here.
A couple of parachute construction notes:
Make sure that the parachute is a long way below the balloon. That’s because the shreds of material created when the balloon bursts can get tangled in the parachute and prevent it from opening…bad news for your 17 mile fall. Also, put in a spreader (a circle of tubing) near the parachute to make sure it is slightly open, so that when the balloon pops and the whole thing starts to fall, the parachute can open. Here’s a photo of the balloon in flight; note how far the parachute is from the balloon:
Predicting Where the Balloon Will Go
Balloon flight prediction depends on weather prediction. If the weather prediction is accurate, then this website will give you a very good idea of where your balloon will end up. If the weather prediction is not accurate…good luck. In our case, a snowstorm had just passed, and the jet stream was swinging north. Since the winds were changing direction so quickly, our balloon actually landed 50 miles south of where we predicted. That’s why it ended up in the mountains, and that’s why it took a 3 day hike to get it back.
A Final Note on Legality
What we did was legal under FAA regulations. However, it is your responsibility to ensure that whatever you do is legal. Find the regulations here. If you are not sure, contact your regional FAA office.