From: Doug Jones (random@qnet.com)
Date: Tue Mar 07 2000 - 00:01:09 MST
There was a long (and acrimonious) discussion of aircars in
sci.space.policy about a year ago... the most interesting item was a
straightforward scheme for traffic control that eliminated high speed
merging problems. I can't recall who originated it.
In the simplest instantiation, heading is a function of altitude,
incrementing by .25 degree for each meter relative to a zero datum. As
a skycar climbs, it turns to its right- if ascending at ten meters/s
(about 2000 FPM), this is slightly slower than a two-minute turn.
Descending traffic turns to its left- *and all vehicles at a given
altitude travel on parallel paths.* The only opportunities for
collision are during ascent and descent, handled by relatively simple
"flocking" algorithms to resolve conflicts.
All traffic is point-to-point, no "airways" to unnaturally concentrate
vehicles into limited airspace. With the high power-to-weight ratios
needed for VTOL flight, acceleration to cruising speed is rapid.
Additional layers of traffic allow higher speeds, and speed can also be
a function of altitude, so that all cars at a given altitude are
motionless relative to one another. Flight planning incorporates
offsets to compensate for the helical paths at the ends, and special
rules for local problems (like skyscrapers) can be patched in.
The system requires navigation of differential GPS quality, but control
is distributed and automated, and conflict resolution is local and
simple.
-- Doug Jones Rocket Plumber, XCOR Aerospace http://www.xcor-aerospace.com
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