[FoRK] Where the F&@# is my flying car?
Stephen D. Williams <
sdw at lig.net
> on >
Mon Sep 11 17:18:03 PDT 2006
I would like to point out some things that only became apparent after I
flew for a bit, even though they are obvious:
While you are likely to survive most mechanical failures in a car with
ease, certain things would be similar to having engine or control
surface trouble in an airplane: Losing a wheel or brakes at high speed
would not typically come out well (I lost nearly all brakes on an
Interstate years ago). Even a tire blowout, reasonably common in the
past, can be dangerous at highway speeds. You are also dependent on a
continuous availability of roads, intersections, signage, bridges, and
failure status. In the US, there is quite an involved system to manage
all of this. It is an interesting point that there may come a time when
there are more areas like most of Alaska where it is more economical to
fly than to build and maintain such infrastructure. Certainly if we
were to make use of vast stretches of land, say in the Rockies, flying
would probably make more sense.
While cars can stop pretty much anywhere, a big problem is that driving
usually means you are about 0.5-5 seconds from utter disaster. Small
and short lapses in concentration at nearly any point in travel can
create unrecoverable circumstances. The edge of the road, ditches,
trees / poles, crossing the center line, and unguarded mountain roads
(up the mountain from Nice in the snow or on the south side of Molokai
are both good recent examples for me) are all hazards that can take a
drive from a boring multi-hour activity to extreme danger in an
instant. I'm sure that the most dangerous thing that I do, and have
done many times in the last 11 years, is 500 mile driving trips while tired.
When flying, at least in current and foreseeable conditions, take off is
only slightly dangerous and enroute flying is characterized by decisions
and responses that are normally minutes or many minutes between an error
and actual danger. Usually there is plenty of time to catch your
mistake and take corrective action. Only in landing or high-traffic
pre-landing maneuvering does the attention have to be focused on
situations and actions that are seconds long. Most of this is really in
the last 30 seconds before landing.
One of the better proposals, on Popular Mechanics at some point of
course, was a model that had 6+ small turbofans or similar. The unit
was designed with so much redundancy that it could land under power with
just one unit functioning and take off with something like a majority.
The problems are solvable engineering issues. We have plenty of power
density, composites, engines, and avionics. Most of what is missing is
desire and belief that it can be managed.
Russell Turpin wrote:
> Eugen Leitl <eugen at leitl.org>:
>> Stabilizing a personal VTOL aircraft in a cluttered urban
>> environment is a control nightmare. Letting people fly is just
>> not an option. Building such an advanced controller in a cheap
>> enough package reliable enough to be insured is the reason
>> personal aircraft hasn't been happening yet.
> It seems to me there are two related issues of some significance. The
> automobile has the great advantage over air travel that one can
> stop practically anywhere, for anytime, for any reason: to buy
> cigarettes or coke, to drop off laundry on the way out of town, to
> give a young daughter a chance to relieve herself yet again, to
> take a picture from a scenic overlook, to stretch the driver's legs,
> or because something has suddenly become a barrier to one's path of
> travel. Movies that show flying cars as the wave of the future, such
> as 5th Dimension, often give them a similar behavior. They are not
> just short take-off and landing, but hover, at any height, without
> harming whatever happens to be underneath. And have good midair
> brakes. That makes thematic sense, and for the same reason, it is
> an important part of what would make a personal flying device truly
> useful. Alas, it is also a much more difficult engineering problem
> that building a small airplane.
> The other issue is the converse. Not only can one stop a car almost
> anywhere for arbitrary desire, but a car stopping when not desired
> usually is no great problem. Yes, if you're on a Houston freeway
> when your waterpump moves its last drop, or when your fuel filter
> becomes completely clogged, or when your timing belt breaks, your
> car will be towed quickly by a company who has won the city
> concession for moving inoperable vehicles from the freeways. Most
> times, you're able to pull over to the side of the road or limp to
> some parking lot, where you can arrange for tow or repairs more
> conveniently. An airplane losing its engine has a larger problem.
> Not usually a matter of safety. Because this circumstance now is
> rare, because planes usually fly at significant altitude, and
> because airports immediately answer such emergencies, a pilot who
> loses power most times has the time and opportunity to find a safe
> place to land. This all changes if a large fraction of the commuters
> are flying their cars about the city. These will break down as
> frequently as cars do, because most people will do no better at
> maintaining them than they do their ground cars. Altitudes will be
> lower, because no one flies to 5,000 feet just to get across town.
> And airports aren't going to be answering the needs of hundreds of
> thousands of flyers.
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