Gary Osoba <<email>> writes:

As you know, I have been active in exploring various flight regimes for some time and have often used a non-profit research entity to pursue some of these avenues. What they have in common is an interest in what I would term "natural flight" by its most efficient means. Areas of interest include gravity, solar, regenerative and human powered forms. Active investigations include: 1) The expansion of flight performance within existing fields; 2) Design and fabrication of efficient flying configurations; 3) Optimization of flight efficiencies and energy harvesting in typical atmospheric regimes; 4) Development of new piloting and/or flight control methods.

From time to time information comes to my attention which might be very useful to others. At earlier points in time, readers of the Oz Report were mostly anonymous unless they posted to the Report itself. With the advent of your forum and more comprehensive posting, it has become clear that many of them are interested in serious exploration, experimentation and science. Some of your readers are interested in battery powered technologies as applied to hang gliders and/or ultralight tow vehicles, and some are even interested in solar-powered flight.

My late friend Dr. Paul MacCready was a special pioneer in this field. Other hang glider pilots such as Eric Raymond and the late Guenther Rochelt have also been active in innovation with solar and/or human powered flight. Dr. Rehmet, current chairman of the OSTIV SDP (Sailplane Development Panel- a group I have worked with from time to time) wrote his doctoral thesis in connection with the innovative Icare II. Here is a recent compilation, courtesy NREL, which shows the present state of the art in cell efficiencies.

As can be seen, continual progress is being made in this regard. For the casual reader with some interest, a periodic search on MIT's Technology Review website under solar cells will reveal many other areas of investigation. Some of these will pan out, most will not. There is a particularly promising new alloy being investigated which possesses wide-spectrum responses and good heat transfer characteristics. I'm keeping my eye on that one.

A much easier to read version of these graphics is found here.

Of course, this reflects the efficiencies of the solar cell only. Total system efficiencies might run 1/4 of this when batteries, gearboxes, props, etc. are including in the power train.

Energy storage is another matter. Following is the Ragone plot for various devices, from Livermore Labs. I first became interested in alternative energy storage for flight propulsion during the early 1970's when Tom Dolsky, a member of the Pliable Moose hang glider inner circle and I experimented with natural rubber devices for launching rogallos. This proved entirely impractical at the time, but I did correctly envision the full value and cycle-specific application for regenerative devices. Tom went on to develop the modern pay-out winch, later implemented by Forberger and others.

One can readily see the challenges of battery powered flight when comparing, for an example, Lithium Ion technology to gasoline powered devices which reside an order of magnitude or so higher in specific energy density.

Of course costs also come into play. Here's a chart reflecting progress in cost-effectiveness over time for lithium ion batteries which may be applicable for our purposes. Some recent advances in larger batteries, mostly driven by hybrid technologies for autos (I've put about 75,000 miles on my 2006 Prius and love it), are not reflected. Nor are they in the present regime of interest for energy/mass comparisons and light flight. The efficient and light sector continues to be driven by small batteries for application in cell phones and computers.

One of the things that I have an interest in doing in the future is implementing a specific and heretofore unique design for slow, silent flight that can be utilized to study various bird species which are rare or hard to get to in habitat. These technologies would be important for such a project. One of the problems we all face is too many interests, not enough time, not enough funding. If anyone is seriously interested in pursuing something like this, and particularly helping to fund it, please contact me directly.

I hope the above info proves helpful to dreamers/experimenters who read your useful Oz Report, and therefore wanted to share this with them.