Doug Jones wrote:
> Spike Jones wrote:
> >
> > The reason Im having difficulties with Moller's aircar is a neat
> > little estimating technique for the thrust required to maintain straight-
> > and-level flight: you need to know the power-off glide ratio. If it is
> > 10 forward to 1 down, then it takes a thrust of about 1/10 the weight
> > of the aircraft to fly at the power-off glide speed.
> >
> > The Moller aircar looks like it would power-off glide like a set of
> > car keys. What is that little airfoil way back aft for? Just to look
> > cool? Glide ratio 10 down for every one forward?
>
> Hey, even a skydiver can do about .8 forward for 1 down- it's fun!
Even a brick can do ok, look at the space shuttle.
> > In any case, it looks
> > like you would need to be making power at *almost* the vertical
> > takeoff rate just to fly straight and level, and with the numbers they
> > call out on the website, with those little tiny rotors, the straight and
> > level power requirement looks like in the neighborhood of 800 hp.
> > Recall that a typical modern Detroit mobile, ambling down the
> > freeway at 100 kph only requires about 30 hp, if I may mix units.
> >
> > Nowthen, if we want to theorize a really high horizontal speed
> > associated with that 800 hp, we are up against the drag-as-square-
> > of-velocity problem, and so we still have a voracious fuel appetite.
> > Perhaps Doug Jones will weigh in on this, hes more aerominded than
> > I am.
> >
> > I am uncomfortable being in the nay-sayer position, dont like
> > doing that. But the Moller aircar as shown on the website
> > wont fly in that configuration. spike
>
> I pretty much agree with you- the aspect ratio of their lifting surface
> is abysmal, and the frontal area is huge, so they have high induced drag
> AND high parasitic drag. This would make a MIG-15 look economical.
Word is that:
In full foward flight:
a) forward nacelles provide 25% of lift
b) fuselage produces a full 50% of lift
c) rear wing produces 25% of lift
d) rear nacelles produce 2/3- 3/4 of thrust
e) forward nacelles produce 1/4 -1/3 of forward thrust
So essentially they are utilizing some lifting body aerodynamics (and apparently
they've got the wind tunnel work to prove it) to provide the majority of the
lift in forward flight, and the rear wing is there merely to take some or all of
the load off of the rear engines so they can produce more forward thrust...
This archive was generated by hypermail 2b29 : Thu Jul 27 2000 - 14:10:04 MDT