Saturday, April 11, 2009

Balloons and Rockets

First balloons:

For the last few years, I have been teaching a class on "system integration", which is basically a way to say, "put all of the these parts together and see if they work". As I have stated many times on this blog, I feel like students should have some hands-on practical experience. So, in my grad-level class, I don't teach them anything, I make them do something. And that something is launching a balloon up to 100,000 feet. But, they have to recover the payload and follow FAA regulations. The first part is relatively easy, but the second part makes things a bit more complicated. This is because, to track the balloon, all you need is a GPS and a radio. Stick that on the balloon and you are basically done. BUT, FAA regulations say that you have to be able to kill your balloon at a moments notice. Which means that you have to communicate WITH your balloon. Hence, you have to have a little computer on-board and enable a cut-down switch and all sorts of other crap, which is quite complicated. It is basically like launching a little satellite.

It is that time of year when the students are just about done with their balloon builds and are getting ready to launch. I have some great stories about balloon launches, which I will leave to another time, but I will include a picture from one of the balloons (from last year), and a story of tether testing...

This is a picture from pretty close to 100,000 feet. The balloon that took this picture landed in Lake Erie, which is was not supposed to do. Obviously. It was a pretty screwed up day. But, that is a story for another day. Let up proceed with yesterday's cluster f*ck.

First thing that you have to realize is that a weather balloon is BIG. Here is a picture of yours truly holding a balloon on a very, very calm day.

They are about 8 feet in diameter. On a calm day, this is no big deal to handle, but on a windy day, the horizontal drag force on the balloon is enormous. This means that it wants to go with the wind. Not stay in your hand. Go. Sideways.

The general idea of a tether test is to raise the balloon up a few hundred feet, and then verify that the communication system is working perfectly. You also test your balloon filling procedures and stuff like that. The big problem with tether tests is that they NEVER WORK! The wind ALWAYS causes a problem. The issue is that the balloon is lifting the payload in the air (but just barely, since the payload is heavy), but the wind (even a light wind), exerts enough force to blow the balloon back to the ground (picture an upside down pendulum).

Well, I had experienced this effect two times in the past, with disastrous consequences both times, so I was not feeling too positive about the tether test that the students wanted to perform yesterday. But, being adventurous, I agreed.

So, we get out on the field, and the wind is blowing at something like 10+ MPH constantly. It is quite difficult to actually control the balloon while filling it if the wind is blowing, so typically, you use a sheet over the balloon. The sheet has to be quite large, since the balloon is quite large. Like, really large. Typically, I encourage a big sheet with rope tied on to each corner. Well, they didn't have anything like that. So, we dealt with it. Then other things went wrong. And more things.

The predictable thing happened - the balloon didn't rise off the ground because the package was too heavy and the wind was blowing too strong. So, we packed it in and called it a night. Then, as we were reeling the balloon in (package in hand!) the cords snapped and the balloon took off. The perfect ending.

Or, a great start to balloon season!

Ok, now rockets.

For two semesters now, I have taught a rocket science class, in which we take a class period and actually launch rockets. In order to up the ante a little bit, I give extra credit to students who bring a rocket. Last semester, I got about 20 or so students. This semester over a hundred students brought rockets. It was absolutely insane. We set up three launchers, with Crab Girl helping out the students to launch their rockets.

We had many rockets in which the parachutes did not open, so they drilled into the ground. It was quite humorous. A really funny part was when one of the students did a very loud count down, and then nothing happened. Typical NASA.... Then another student, who had obviously built the rocket himself, launched it up in the air about 30 feet, where it jogged a bit to the left, circled around for about 5 seconds, then exploded. Very exciting stuff!

My Dad came to the launch. The kids, the neighbor and the kids and a co-worker and his son. As I was doing this, I thought, "Wow, I get paid to do this!"

In one of my last posts I said that I hate every aspect of my job. I don't. I hate all aspects, but these. I love these aspects. On days like Thursday and Friday, I am very happy to actually work where I work, doing what I do.

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