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Advantages of Pneumatic Servos (from KitePlanes to Megascale AWES Units)

More Forum Review, with updated explanations-

Conventional UAS methods have severe disadvantages for AWES deployment. For instance, typical electrical systems are radar reflective, creating excessive radar clutter, especially if deployed aerobatically in large numbers. Electrical flight servos are a particular UAS problem area- they are expensive, heavy, fragile, and just don't last long enough (100-hour inspections, with 1000 hr typical continuous-duty lifecycle, at moderate loadings).

The "standard" servo duty-cycle predicted for complex AWES UAS is a full orbit occurring every few seconds, for months at a time. The Achilles-Heel of ordinary servos is shock-loads, which hammer individual gear teeth. Once a few teeth break, the servo fails. Heavier gears add unwelcome mass. The only electrical-servo solution that currently makes engineering and economic sense is actuation by cheap massive long-lived industrial servos kept on the ground.

We can invent new UAS AWES technology to resolve existing limitations. Pneumatic servos are an interesting option. They are typically rated for tens of millions of work cycles (10,000 km of travel). Compared to gear-based servos, they are inherently tough and shock absorbing. They come in all-plastic nonconducting versions to alleviate radar and lightning concerns. They are the lightest actuator solution (highest power-to-weight). They typically cost about 1/4 the cost of a comparable electrical actuator (by power).

One can find claims that electrical servos are somehow better that pneumatic servos, but these are not true inherent advantages, only successful legacy cases improperly presented as conclusive systems-engineering evidence. Similarly, hydraulics have many successful cases, but specific inherent defects (like dependence on maintaining a hydraulic fluid supply, compared to freely available "weightless" air). All in all, ordinary air is good stuff, and pneumatics use only grows in modern control engineering.

We even have recourse to create wonderful new methods of large low-pressure actuators based on air-bladders and blowers, for megascale AWES actuation aloft. Existing UAS electrical servos are fine for toys and many conventional flight platforms, but they simply do fit AWES super-duty needs, nor scale well for giant AWES use.

Comment and development of this topic will be occurring here.       
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