We continued testing the 1 and 4-rotor mesicopters and have compared them with the computational predictions. The lift at a given RPM is quite close to what was predicted, but the motors require more than the expected surrent to achieve these speeds. Aerodynamic uncertainties are one possible explaination, but we need to be sure that the motors are delivering the claimed torque.
Lift tests were completed for variants of the optimized rotor design to check that 3-D viscous effects were not reducing the lift at a given twist angle. 2 new rotors with an additional 2 deg and 4 deg of pitch were constructed and tested. Little additional lift was obtained.
Shelly has made new rotors using while and yellow polycarbonate as well as epoxy. These rotors are much more flexible, but more durable as well. Further testing is needed.
For initial self-powered prototype tests we need a commercially-available battery. Of the batteries available
the choice seems to me to be a silver oxide #333(1.6g 6.8mmX1.05mm), #335(1.4g 5.8mmX1.25mm), #337(1.2g 4.8mmX1.65mm)
.16, .14, and .12 grams respectively. I have successfully removed .02 grams of skin from #337 with no change in
function. Scott will get enough of each size to test them as a group with material removed. Subsequent tests suggest
that they have sufficient current to power the mesicopter prototype.
To determine the motor torque so that we can calibrate the rotor performance code, Ilan proposed spinning disks for which a closed form solution for torque is available. Scott built some of these and started the tests.
These are the final tasks in phase I and many people are contributing. Our internal website now includes a rather
comprehensive image archive and papers from students.
Ilan gave talks on the mesicopter at CalTech, and NASA Ames. Many useful discussions regarding system architectures,
communication, and distributed control followed and will be pursued in subsequent phases of this research.
Our funding for Phase I ends 4/30/99, but we are continuing to develop the prototype system and expect to fly, carrying the power supply very soon. The next step will be to tackle the stability and control issues as well as system-level sensing and navigation concepts. This will be part of our proposed Phase II work, but Ilan is discussing various ideas with NASA researchers.