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JPL Annual 2003 Invention Challenge Results Gallery
Entry 3
 
 
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entry03-001      
Comments

a) What your team thought of the challenge (objective)?
Cute pun. This year's challenge was a nice simple concept. It really let me apply the KISS principle: Keep It Simple, Stupid. Thanks again to Paul for organizing this fun and educational event each year.

b) What ideas your team considered?
Since I didn't want to build a launcher, I wanted something whose flight path would be insensitive to the launch speed. I figured that aerodynamic forces (lift, drag, moment) scale in proportion to velocity squared, and so does centripetal acceleration, but gravity obviously doesn't change with launch speed. Therefore, I wanted gravity to be relatively unimportant. I didn't want a gentle glide path because the landing point would be very sensitive to variations in the launch conditions. Instead, I imagined a glider that would climb rapidly, while rolling strongly over, about half of a barrel roll, and swoop down upside down at a steep angle into the ground. On the entry form, I called it the Corkscrew. I thought this approach would give a fairly repeatable path that would not vary much even for different launch speeds. If it went fast enough, the wind wouldn't be too important either. A lightweight device might be expected to come off at high speed, and might approach this condition. But I was also afraid that a light object would have so much drag that it would not reach 40 feet distance from the launcher. I also wanted something sturdy that could take repeated impacts with the ground without changing its shape. I didn't have a lot of time to invest. I wanted to keep it as simple as possible. In the end, I purchased a relatively large, yet lightweight glider made of Arcel. This material is a lot tougher than Styrofoam. I considered different ways to adjust the roll control. I thought of having ailerons and elevators with some kind of turnbuckle adjustment pushing on a control horn (sort of replacing the servos in a radio-controlled aircraft). I thought of strips of sandpaper on the right wing to spoil the lift and create drag. I thought of actual spoilers like speed brakes on some real gliders. I ended up being guided by what I had available. I used strapping tape to attach a strip of balsa wood to the top of the right wing. At first, I tried to make it into an aileron on the trailing edge, but it was hard to keep the angle fixed using tape. I ended up just taping it on top of the wing so it was angle upwards somewhat. It must have provided three different effects: a little downward lift, a little extra drag, and a little extra weight all on the outboard part of the right wing. These things could all be expected to contribute to the required right turn.

c) What was your final design?
Final design was a store-bought glider with a flap of balsa taped to the top of the right wing tip.

d) What was your testing process and how did you improve?
Since I didn't build a launcher, I had to guess initially at how hard it would launch the glider. I thought it would go really fast. It just seemed like a very strong spring. I basically threw it by hand very hard and adjusted things (elevator setting, size of balsa strip) as best I could. Then I signed up for a 20-minute testing period with the actual launcher. I found that it launched much less forcefully than I had been throwing the glider. It tended to climb, but did not have enough umph to do the barrel roll I'd imagined. Instead, it stalled and wallowed. I had to adjust the elevator to produce more level flight. I also adjusted the size of the piece of balsa (simply broke it in two and stuffed it back under the tape) to get the glider to go far enough. I also threw it by hand a few times to get a feel for how hard I should throw it to duplicate the launcher. I went home and screwed a couple of long screws into the nose to add weight, and launched it by hand a few times until it seemed about right. Another contribution to the right turn was allowing the glider to rest on the launcher with the right wing low. By aiming the nose slightly right or left, I could change both the roll angle and the initial direction of the flight.

e) What your team learned at the regional contest (if applicable)? N/A

f) What were your feelings or experiences at the JPL contest?
I really did not expect to do well. I did not have a very repeatable setup. I knew that my glider would generally go in the right direction, but I only had the one opportunity to test it with the real launcher. I knew that luck would play a big part. But that was OK, I just wanted to have a bit of fun. I was one of the early launches and my first launch did pretty well. It landed about seven feet from the mark, which put me in first place at that time. Of course, I was pleased with that, but I certainly didn't expect it to last. But then quite a lot of the entries tended to fly too straight, and I started to think I had a chance after all. Then suddenly, about four shots in a row dropped closer to the mark than my entry. My second launch did OK, but not quite as well as the first, and I had to leave to go to party, so that was that, as far as I was concerned. Only later, as I was returning to my office, someone congratulated me on my entry. Uh? "Sure, they announced your name." So I dashed back to the mall and found out that I'd placed second in the JPL portion. Of the four entries that got closer than mine, three were in the school division. Congratulations to them, but I was only competing against other JPLers. Sure, I'm happy to have placed well, but I attribute it mostly to luck.

g) How would your team improve your design?
It's not so much the design I would change as I would do more testing. I relearn that lesson every time I enter this contest. Well, I don't actually relearn it because I do remember it from the previous times, it's just that I don't have time (or choose not to invest the time) to do more testing. However, it does seem to be a general observation that we tend to put things off until it's too late to do a lot of testing and readjusting.
 
 
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