At 10:54 AM 9/26/01, Michael Flora wrote:
>Rex Anderson writes:
>
> > (And do a search at that site for "ornithopters.")
> >
> > People keep working on them, yes, but with little success so far,
>according
> > to the articles I scanned.  Even if they did get past the technical
> > problems, there would still be the incredible task of keeping all those
> > moving parts working in a desert environment of grit and dust.
> >
> > Rex Anderson
> > [log in to unmask]
>
>Of course, today we use helicopters in the desert.  Helicopters have a
>complex transmission system to tilt and drive the main rotor and tail rotor,
>and large ones typically have gas turbine engines that are highly
>susceptible to grit damage, yet somehow they are kept functioning.


It takes a rather substantial effort to keep helicopters working in desert 
conditions.

Back in the latter 1970s, when I was an officer in the US Air Force, I was 
an engineer in the branch of the Flight Test Center that tested all three 
versions of the cruise missile and various types of "unmanned aerial 
vehicles" (UAVs).  We operated out of Hill AFB in Utah and used a portion 
of the Great Salt Lake Desert as the test range.  Some of the UAVs were not 
designed with landing gear but were intended to be caught in mid-air by a 
helicopter trailing a hook arrangement that would snag a parachute released 
by the UAV when it completed its mission.  The rule of thumb was that it 
was necessary to have _two_ helicopters scheduled and ready to go at the 
start of a test flight for every _one_ that would be needed at its end, an 
hour or two later, because the desert environment was so hard on the 
helicopters that one of them would probably develop a problem.  Several 
times, scheduled test flights for projects I was working on had to be 
scrubbed due to there not being enough working helicopters in the hanger 
before the flight to insure that there would be enough in the air at the 
end of the flight to accomplish the mid-air recoveries.  It was especially 
critical on one project that I was project engineer on, because we were 
testing a system for controlling multiple UAVs at one time, which meant we 
needed multiple helicopters to catch all of them.  Occasionally we had to 
allow one of them to make an unplanned "ground recovery"--i.e., set down on 
its belly--because a helicopter had broken sometime during the 
mission.  (Although the parachute would slow the UAV to only a few feet per 
second before landing, some damage was unavoidable during a ground 
recovery, so those were to be avoided if possible.)

I left that assignment in 1979.  The next year, when I heard about the 
failure of the mission sent to rescue the hostages in Iran, one of the 
first things I noticed was that the helicopters they were using were the 
same ones we had been using in Utah, and I wondered who had been 
responsible for advising the mission planners to not send an adequate 
number of spare helicopters to allow for the inevitable failures 
encountered when using them in a desert environment.


>I doubt
>that an ornithopter would have more than twice the moving parts of a
>contemporary helicopter.
>
>This introduces the (perhaps trivial) question of why Herbert decided to use
>ornithopters instead of helicopters.  Simply more exotic?  Also, I seem to
>remember that antigravity devices were used (although I may be confusing the
>book and movie here).  Why mess with wings when you can just float where you
>want to go?


Just a guess (I don't remember whether it was mentioned anywhere), perhaps 
antigravity devices are more expensive to operate, so they would only be 
used by the rich or in certain situations when their higher cost was justified.



-- Ronn! :)

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