In the 1950's, many of the first world countries spent huge sums on
developing VTOL test vehicles. These efforts included a number of ducted
fan powered lift systems. Having surveyed them for about 25 years, I have
to throw a little cold water on the proceedings and say there is no free
lunch in VTOL.
The Moller efforts have evolved slowly over the years. From
time to time he seems to have hired competent consultants, but the bottom
line is that even if his vehicle flys, it is physically impossible for it
to
meet the advertised performance specifications.
Take fuel consumption.
Lets be optimistic and put his consumption at .5 lbs/hp hr. The
thrust/horsepower for VTOL and transition will be 3-4 times the horsepower
requirement for forward flight. But it is this VTOL component that is the
selling point. He has 8 engines because of engine out conditions.
At some
point, someone must have suggested a turbine twin-pack and gear boxes and
shafts. Too complex and heavy you say. It is any heavier than the extra
engines at about 150 lbs (his numbers) per engine? Where are you going to
store the fuel and what is the vehicles capacity? The aerodynamics of the
vehicle in forward flight (especially the critical transition period) are
an
issue.
I suspect it is possible to make the thing fly and that it could
have been done long ago. But it would have very limited endurance and the
need for man-rated safety alone makes the costs astronomical. If they
really thought they had something, they would have developed a drone
version. And if anyone (like DARPA) thought they had something they would
have funded it out of a black bag. Remember that Moller has experience in
drones with the Aerobot series.
As for safe testing - we have this place
called Edwards with plenty of room. For a long time I've suspected that
the
Skycar project was nursed along to raise funds to put into the Wankel
engine
program. This is not a dumb idea if you have a worthwhile engine. I
don't
know how much money has been raised over the years for the Skycar. I've
never seen an audit report on where the money went, but I do know from
personal experience that projects that are chronically underfunded and
don't
show results are inefficient projects because the overheads keep going and
going and going like the energizer bunny. You end up with funds
supporting
the company structure with minimum return in development. You don't have
to
be criminal to be unrealistic. But the results are the same.
George Wright
I might mention that George co wrote a book on ducted fans.
Is the book still available George?
Paul Lamar
yes. I've just finished up a second book, "Modern Ducted Fan Aircraft" and
am scaring up the graphics for it. Won't be out until late 2007.
Marc de
Piolenc is putting the final touches on another volume including a good
section on ejector cooling. I'm afraid I slowed him down recently by
dumping a bunch of data on stator installations for ducted fan hovercraft on
him!
We're also doing a very low cost (500 kg payload) hovercraft prototype
for developing countries in the Phillippines. Not using a ducted fan. In
concept it is similar to the old Mississippi riverboats, cheap wood primary
structure good for 4-5 years, discard it and move the machinery to another
frame. The idea is to build something that uses local materials including
the unbiquitous Suzuki 3-cylinder (40 hp) used engines that are imported in
bulk. I'd love to try an industrial Wankel on this thing, but the import
duties in that area prohibit this.
We're using Hovey's Simplified
Propellers for Low Speed Aircraft for the wooden prop. I used the same book
in the late 70's with Jim Eich to do a prop for his Continental-powered gyro
and it came out right on the money. This lets us make the props locally.
Normally, I'd just buy a prop here and ship it in and just build a
duplicator on site, but the import duties hit you again and it is an area
where a genuinely skilled worker gets $4-5/day US and is happy as a clam.
George Wright
Don't forget to included this Kucheman & Weber illustration George :)
You can also use the rest of these if you give me credit.
Paul Lamar ...No rotor no motor.
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site.
http://www.rotaryeng.net
Copyright 1998-2006 All world wide rights reserved.
