"Larry Dighera" wrote in message
...
On Sat, 05 Mar 2005 17:26:33 GMT, "Colin W Kingsbury"
wrote in
. net::

Sure, it might fly, but who wants a machine with the fuel burn of an old
Lear (at low altitude), the maintenance costs of a big Sikorsky, and the
payload of a 172?

It's a start. It portends the future. It's going to need development
and refinement, but I believe these vectored thrust machines will
eventually be successful in achieving flight and eventually public
acceptance.

It seems to me that vectored-thrust aircraft face a couple of fundamental
challenges that will not be easily overcome.

First, you have the poor efficiency of turbines at low speed. The ducted fan
approach will improve this somewhat but if you look at the V-22, it has HUGE
propellers, more like mini chopper blades. The V-22 may be intended to spend
more time in hover than a Mollermobile, but I'll side with the machine
that's being flown seriously over the eternal prototype.

Second, the powertain complexity is considerable. You need at least 4
nozzles for control, and 2 engines cross-linked to drive the blowers. I'm
not a MechE but that sounds like a lot of transmission hardware to manage.
What's that statistic I've read about the ratio of shop hours to flight
hours for helicopters? This would be much worse.

And let's not even get into the control systems. These things would seem to
demand pretty sophisticated fly-by-wire and that's going to cost serious
money to design and certify, made all the worse by the fact that someone's
got to be first. Remember the Starship? FAA conservatism has more than a
little to do with why the plane became an albatross, though it also paved
the way for planes like the Premier.

Again, the V-22 is the best precedent we have to go on here, and the
evidence is pretty bad. Twenty-some billion spent as I recall and the things
are still nowhere close to deployment. Heck, by that standard the 70 million
or so Moller has spent seems like a pretty good investment. Still, I don't
see any of these guys solving or even coming close on any of these
fundamental problems. Remember the old engineering saying: 90% done, only
90% to go. Software has become fantastically cheap largely because consumers
have been willing to put up with 90% done. Aerospace does not enjoy this
advantage.

There are many technologies that stubbornly refuse to yield to our desire to
make them workable. Fusion power, for one. In aircraft, the real area to
watch (imho) is pulse-detonatation engines, which if they ever become
commercially viable would give us the "Orient Express" planes that take you
to Tokyo in a few hours. But Pratt and GE have been working on these for
some years, and expect to be working on them for many more, and cannot tell
you how close they are to getting it right. As much as I'd like my Jetsons
car, I doubt I shall be seeing one anytime soon.

-cwk.

Michael Jackson, on the other hand .... :-)