Ever since I was a kid, I’ve been interested in weather balloons. Truth be told, I’m still a little bit of a weather geek.
In middle school, my friend and I ordered away for a surplus radiosonde. A radiosonde is an electronic instrument that is either carried into the atmosphere by a balloon or dropped by a weather observing plane. In either case, the instrument sends weather information (typically pressure, temperature, and humidity) at various heights in the atmosphere to ground based receivers. The receivers track the travel of the instrument to determine the winds aloft.
The radiosonde we got was one that was to be dropped from an airplane. When we opened it, we saw a cardboard canister on top of the instrument with a metal cap and a pull ring, much like you’d find on a hand grenade, taped down. In bright red letters appeared a warning: “Danger! Explosive force!”
We knew this came from a military surplus outlet, so we took this warning seriously. We called the police and asked what we should do… and here’s where the fun begins. They said that we would need to safely discharge this by placing the unit on one side of a structure, such as a garage, tying a rope to the ring, and throw the rope over the roof of the structure to the opposite side. Once protected by the building, we could safely pull the rope, thus pulling the pin, and release the explosive force.
It should be obvious, by now, that the police knew exactly what we had and that it wasn’t dangerous… because if it had been, they would have been there immediately.
Well, that wasn’t so obvious to my friend and me. After all, this is what the POLICE had told us we needed to do. We arranged the instrument and device as recommended. It was on one side of our garage and we were on the other. Just as we were about to pull the rope, my mother came to the back door to see what we were doing. We explained what the police said. With a very concerned look on her face, she said go ahead, because she didn’t have any other ideas on how to safely discharge the thing… and, it is what the POLICE had told us.
We pulled the rope… and we heard a whirling sound like that which would be emitted from a wind-up toy. And then, “SPRONG!” was the sound of a spring being decompressed.
We raced to the other side of the garage to find the metal cap originally on the top of the canister, lying on the ground. Now revealed to us was a large spring, like what one might find in a spring mattress, connected to the cap. It was connected to a piece of silk cloth that was folded into what we discovered was a drogue parachute. The way the mechanism worked was then obvious:
- The person on the airplane would pull the pin and toss the radiosonde out the airplane.
- The timer would assure the instrument got far enough away from the airplane before deploying the parachute. If the parachute deployed immediately, it might get caught up in the airplane.
- The cap would pop off, pulling out the drogue parachute which would pull out the main parachute.
- The instrument would float to earth and send the weather data.
We never launched the radiosonde, but we learned a lot about how they worked. We took it apart and studied the electronics and mechanics. It was fascinating.
Looking back, you can understand why the warning was there: if you pulled the pin and this thing went off, you could have been seriously whacked in the face… but that’s about it. The spring wasn’t that strong: it could be compressed with one hand. In fact, we’d put the thing back together and show others how it worked by pulling the pin and watching the top spring off.
Fast forward to today. With the advent of cheap cameras, GPS, and disposable cell phones, there have been A LOT of folks who have created their own weather balloons experiments. It is so popular that Citi even featured this in one of their commercials: http://www.youtube.com/watch?v=gVRLGOFBQhY
So I’ve started to think about inexpensive ways to get started with my decades old dream. Perhaps the old fashion way: Launch a bunch of balloons with prepaid postcards and see what people find and comes back?
That got me wondering about the ecological impact of this idea. The web to the rescue! It turns out that latex balloons are really not that bad for the environment: being made of tree sap, they decompose at the same rate as a tree leaf. (http://www.balloonrelease.com/faqs.htm).
Another thing for the bucket list…