originally posted by: theboarman
The Prototype Currently acts Like a Quadcopter Drone in Flight, But there is a place for Some type of jet technology.
The video says it acts
like a quadcopter, EXCEPT it can fly in any direction, implying a quadcopter can't do that. What? That makes no sense. Quadcopters CAN fly in any
direction, can't they?
Then in an apparent contradiction of that claim, it shows two (apparently model or fake) jet engines which definitely make it more unidirectional tham
omnidirectional:
If they were real engines, they would be heavy and form a weight imbalance.
Speaking of weight, that's very important in aircraft. So it's sort of like a quadcopter but the propellers are inside the aerodynamic shell, so
compared to a quadcopter it apparently has a weight disadvantage because that shell weighs something. So you would actually have to run tests to see
if the reduction in aerodynamic drag from the shell gives it more airtime than a similar quadcopter without the shell.
Also, I remember an aeronautical engineer wrote a long reply to your proposed disc aircraft design citing a lot of reasons why the design wasn't
optimal. Wouldn't those apply here too?
www.abovetopsecret.com...
For subsonic aircraft, designers generally prefer a rounded leading edge for the airfoil because it allows a greater range for AoA (angle of Attack)
without problems. A sharp leading edge for subsonic craft (it's demonstrated in subsonic mode and I doubt that model can go supersonic) can cause
problems as described here:
aviation.stackexchange.com...
To increase the range of angles of attack at wich the boundary layer stays attached and to allow for a more gradual transition between normal flow
and stall, the designers favour a quite blunt leading edge for most commercial and general aviation aircraft. This will increase the drag at zero AoA,
but won't force the air to follow a high curvature at positive AoAs.
If it actually flew supersonic, first of all forget the omnidirectional claim when it's supersonic, and in that case the sharp leading edge would make
more sense. But the omnidirection shape is not inherently stable, I think you need some drag in the rear end of the aircraft in things like tail fins,
or at least swept wings, for natural aerodynamic stability. I remember seeing someone testing various designs in a wind tunel and if there wasn't
enough drag in the rear end of the aircraft, it was unstable. I think that's why most planes seem to have tail fins and a vertical stabilizer. An
exception is the B-2 which doesn't have either, but it uses computer control of the trailing surfaces of the wings. So that can be done but then it's
no longer omnidirectional, it would need the control surfaces in the rear of the airfoil like the B-2 has, if you wanted to use the principles of how
the B-2 flies in a flying wing type of design.
Another advantage of the B-2 flying wing is the aspect ratio, it's not round, so the drag from the wingtip vortices is not as big a problem as it
would be with a circular flying wing, which is going to create a lot of drag from the vortices. The circular wing
Flapjack used counter-rotating propellers to help combat that problem, but the design proposed
in the OP lacks such propellers:
During WWII, Charles H. Zimmerman led a team at Chance-Vought that created a series of designs that eventually resulted in the Vought Flying
Flapjack,[5] one of the first aircraft explicitly designed as a disc for aerodynamic reasons. The Flapjack had a large wing and very low wing loading,
allowing it to take off easily from aircraft carriers. As with the earlier Vought V-173, the Flapjack's counter-rotating propellers were located at
the ends of the wings to help counteract the drag-inducing vortices that would normally result from a wing of such a low aspect ratio. By the time
the design was flying in the post-war era, jet engines had rendered the design obsolete and the US Navy lost interest.
My main thought is it seems a bit uncertain about what it is, is it omnidirectional as claimed or does it fly in a particular direction because of the
jet engines? Is it subsonic or supersonic? Obviously the test flight is subsonic but they are hyping supersonic, but I'd love to see what happens to
that design in supersonic wind tunnel tests. My prediction is it would be a disaster, but I'd love to see a test that proves otherwise.