Design and build a miniature airship that uses a combination of a balloon and rotors for lift. What should make this interesting is the fact that the same rotors used for lift will also be able to control the steering of the airship, without adjusting their orientation relative to the main structure. Here's how:

By using a simple balloon with a weight suspended from a long line, "up" and "down" will always be definite things. By attaching rotors to this sort of object, you don't have to worry as much about a problem common to simple helicopter designs: flipping over. Also, by having some lift come from the balloon, crashes are far less likley to be catastrophic. Of course, this device will be slower and less maneuverable than a helicopter design, but in some circumstances, that's not a disadvantage.

Note: This is incomplete! More to come...

I've long been interested in the idea of airships. I find them fascinating. Given some people's enthusiasm for them, I'm not alone.

In thinking about these sorts of ideas, I came across this image -- an airship far smaller than what one would expect to need to carry a person. If it is an accurate depiction (rather than an artist's simplified rendering), then using even a weak rotor for lift can greatly reduce the needed gas volume.

Eventually, I tried to think of methods to control such a craft. Many insects (bees, flies, etc.) do a wonderful job of switching from hover to flight and back again; their controls for doing so seem far less complex than the code that's been created to allow automated flight of miniature helicopters and aircraft. It seems more like simply leaning one way or the other. By using rotors fixed to a balloon, together with a hanging weight that can be tilted from side to side, it should be relatively easy to demonstrate that sort of control.

I considered trying to build this on my own, but recognized how much it has in common with many problems in several physics courses: there's density and buoyant forces, of course, but there are also pieces related to electricity for the motors, and magnetism for the controls. Also, I am aware that other courses include projects to program control circuitry for rolling robots; if these controls are simple enough, then perhaps it could be automated.

So, this is an extra credit project. If you're interested, let me know in class.

Links:
• http://www.technovelgy.com/ct/Science-Fiction-News.asp?NewsNum=261: A lighting system using balloons similar to the one we're using
• http://www.arborsci.com/Products_Pages/Cool_Tools/CoolToolsBuy2.htm#Vectron: An ultralight toy hover vehicle, using counter-rotating blades.
• http://www.flyingmachines.org/ritch.html A link with a brief description and images of the airship designed in 1878 by Charles Ritchel.
• http://invention.psychology.msstate.edu/patents/ Simine's U.S. Aviation Patent Database, which includes a link to Charles Ritchel's patent
• http://www.robotgroup.org/projects/blimphst.html A history of The Robot Group's airships. Includes the following link:
• http://www.robotgroup.org/projects/envelope.html How to make micro-blimp envelopes
• http://j.piri.home.mchsi.com/freeplan.htm Making Bags and Blimps: free plans, plus a link to parts and accessories for building an airship.
• http://www.myairship.com/index.html Airship and Blimp Resources. Links, many dead, since they haven't been updated in a while.
• A news story about a tiny remote-controlled helicopter
• Another news story about the same "micro-robot" as above
• Radio Control Aircraft A discussion group thread about some pretty potent home-modified motors for small remotely controlled aircraft