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Science Olympiad Event - its making my head spin


I coach Science Olympiad in my school district. A new event at the middle school level is called Rotor Egg Drop. The competition entails dropping an egg from a height and slowing its decent with some form of rotational means. The winning device will take the greatest amount of time to descend without breaking the egg.

The egg is to be held in a paper cup that is attached to the device. The cup with egg must be the first part of the device to touch the ground.

This poses an interesting aeronautical challenge. The simplest solution (which, in my interpretation of the specs, is not allowed) would be to use a rotational parachute. This means the rotor must be rigid.

My current thinking is that blade design should be a cross between a wind turbine and an autogyro. A wind turbine is designed to convert a straight-line wind into rotational velocity. An autogyro creates lift through the rotation of the blades due to the forward motion of the aircraft.

In this case, the blades are driven by the weight of the device falling toward the ground. Ideally, there will be enough lift generated by the outer portion of the blades to quickly reach terminal velocity and fall slowly.

I can't quite wrap my brain around the twist and taper of the blade design to optimize the ratio of rotor velocity to descent velocity. Does anyone have any thoughts or ideas they'd be willing to share?

What you are looking for is called a "Vortex Ring Parachute" or a "Rotafoil." Which can be built solely from trash bags or fabric, and have a fairly high drag coefficient ~1.5.


That is very cool. Thanks. Unfortunately, the rotating device has to be rigid, so cloth or plastic isn't allowed. However, it wouldn't be too difficult to make a lightweight, rigid version of this concept.