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.cb Personal flying machines

	During World War II, journalists, when otherwise unoccupied, would
speculate about the ``post-war world''.  Unlike present journalistic
speculations with similar titles, theirs were generally optimistic, and
one of the themes was that certain new inventions would make our lives
more comfortable.  One such speculation was that helicopters would become
as common as cars and be used instead of cars.  Forty years have passed,
and this still hasn't come about.  Why didn't it happen?  Is it impossible
or can it still happen?  What is required?  Whose fault it it anyway?

	To begin with, what good would be a personal flying machine
that could be used like a car, i.e. kept at home and flown to work
or to the store?  To many people, myself included, it seems obvious,
but there are many skeptics and negative thinkers, so it's worthwhile
spelling it out.  Here are some advantages:

	1. If the flying machine was reasonably fast, the comfortable
commuting range would be much larger.  More people could live where
they want, and husbands and wives would be more independent of each
other in the job market.

	2. Intrinsically there is plenty of room in the sky.  With
accurate enough electronic control, there wouldn't be traffic jams.

	3. Less land would be occupied by highways and there would
be less expense in building them.

	4. Flying is fun.

	The idea was good, but the speculations were
naive.  With 1990s technology, the dream may be technically and
economically realizable, but it may require innovations in the social
mechanisms for supporting technology in order to get the development done.
It may require the reversal of some recent innovations in technology
assassination in order that it be allowed to happen.

	To begin with, what's wrong with helicopters.

	1. They are expensive.  A reasonable four place helicopter
with instrumentation costs $250,000 and $150,000 per year to maintain.
(These figures are guesses and to be replaced by current figures).  This
is not the decisive problem, because there a substantial number of rich
people who can afford that and who pay much more for private jets.  If
this were the only problem the rich would the restof us into the helicopter
world just as they led us into the automotive world.

	2. Helicopters are too dangerous unless operating restrictions are
imposed that seriously impair their usefulness.
  For a long time helicopters were regularly
used from roof tops, but this practice has mostly been replaced by
helipads in parking lots.   My impression is that occasional unpredictable
wind gusts caused too many accidents.
Also helicopters have only recently been able to fly in instrument
weather, e.g. through overcasts.  They can do this only at similar
altitudes to those used by airplanes.
Indeed it may be that the
only person who commutes anywhere regularly using a helicopter is the
President of the United States.  Even he can't go to the store
by helicopter or even go to Camp David without several hours notice.

	3. They require too much skill to fly them safely, and a lot
of willingness to cancel trips if the weather appears doubtful.

	4. They are too noisy.  Many cities forbid landings except
at airports, hospitals and a few other designated places.

	5. They have poor public acceptance.  There has always been
a problem of public acceptance of any new annoyance except by phenomena
in whose benefits the public already shares.  Remember the proposed laws about
there having to be a man carrying a flag walking in front of automobiles.
The anti-technological attitudes widely prevalent among intellectuals
combined with equalitarianism and litigiousness will be difficult to overcome.

	Here are some ideas about how the problems can be solved.
Helicopters are still a possibility but not the only one.

	1. We don't propose anything special concerning cost.  If
a large market develops, competition and automation will bring the cost
down.  The rich will lead the way.

	2. Personal flying machines must be entirely automatically
flown.  This is independent of whether there is a big automatic
traffic control system or whether each machine avoids the others
with its own detection and computation apparatus.
Anyone who treats an airplane --- let alone a helicopter --- like
and automobile is asking for a short life.  We humans just aren't
reliable enough.  Airliners which fly fixed routes require at least
two professional pilots to achieve sufficient safety.  Getting
sufficient reliability in computer control is an unsolved but
solvable problem.  (Some computer scientists might disagree with this
judgment).  Much of the mechanical maintenance will have to be
automatic or automatically controlled and inspected.

	3. A new system of navigation and wind observation is
required.  The navigation problem is easier.  The
Navstar satellite navigation system is good to 10 meters, but
this must be supplemented by a local system good to a few inches.

Wind gusts must be detected and observed.  My candidate for this
is ⊗lidar, i.e. radar using light.  The lidar, whether mounted on
the flyer or on the ground must scan the air mass through which
the plane proposes to fly and determine the velocity field.  This
can be done in principle by doppler reflection from particles
suspended in the air.  So far, as I understand it, the technique
has mainly been used for atmospheric research.

	4. I don't know if the noise problem of helicopters can
be sufficiently solved.  If the answer is yes, then helicopters
are an obvious candidate.

	Another candidate is the airplane.  For this purpose the
airplane must be capable of slow speed flight.  It can keep the
noise down by having a muffler on the motor and a large slow-turning
propeller.  Lockheed built experimental models of such a plane, called the
Q-Star for the Army in the 1960s.

	One possibility for landing is that the airplane land and
take off from a perch like a bird using legs.  If the plane's
landing speed is 64 feet per second, and if the legs can extend
16 feet, then an acceleration of 4g will stop the plane in one half
second.  I believe that anyone can withstand this, properly supported,
because it isn't necessary to breathe during that time.  Whether people
will find the short acceleration
 acceptable is a matter on which a priori opinions aren't
worth much.

This version of fly.ess[ess,jmc] pubbed on {date}.