What good does it do to keep rotating the disc after you have stowed the blades?
Pentagon boffinry chiefs, not content with the existing panoply of wacky new whirly-copter concepts, are to fund still another radical rotary wing project - the "DiscRotor". The idea of the DiscRotor is that of a helicopter with a large circular saucer-like hub and ordinary rotor blades extending out from it. The disco-copter …
Sounds like a typical payment in America's continuing subsidization of certain industries. Rather than look for people who are already doing the research, they pay it out to one of Lockheed, Boeing, or a small handful of others. I wonder how much Boeing is going to suck out of their government for this particular bit of "research" (read: pay 5% of money tendered for the report of the people already doing the research and pocket the other 95%).
The solid rotor generates lift the same way a solid wing does--mass flow. Its purpose is to provide lift in horizontal flight, not vertical flight--that's what the rotor blades are for.
You also use something other than the rotors to generate thrust for forward flight, like a jet engine. The rotors just take you straight up & down at low speeds. Since the outer parts of the rotor blades do most of the work, the idea is you can put a wig over the inner part & pack away the rotors when they're not needed to cut drag in forward flight.
As to keeping the disc spinning, probably because this is just a quick & dirty proof of concept, so why bother? DARPA just does the first draft, after that they let someone else worry about dotting the i's and crossing the t's.
As for cash, I'm surprised they can get something through a wind tunnel test for only $3mil. They're getting a discount, I'd say. You've got to get the test articles made & instrumented, get the facility set up, get the hardware in, do the test runs, reduce & deliver the data, analyze it and write it up, ten clear out the facility and throw the test article in the oneyard--unless you refuse to pay and the next program that wants to test ends up paying to get your junk out of the test cell.
My guess is the engineers are delivering pizzas at night and getting laid off 3 months each year to help make the $3M budget. Certainly they're not giving up money on janitorial services on "mahogany row."
Retract the blades after take-off/hover and then the disk acts as a rotating circular wing which allows you to fly faster than a regular whirlybird. By having the rotor blades retractable, you get the VTOL/hover abilities of a helicopter when they are extended. Best of both worlds. Oh, I would also guess it would be quieter than a regular helicopter.
One method is to make the disk with not only a regular aerofoil profile but also with vanes to force the air towards the outside of the disk. As this makes the air travel faster over the top of the disk, that produces lift no matter how fast the aircraft is moving, unlike a conventional wing which most be moving forward at a certain speed to be able to produce lift.
(No icon because I can't find one for "smartass")
Forget silly little helicopters with a spinning disk.
My 'invention' is an airplane wing that would consist of two sections, upper and lower flight surfaces, each like a conveyor belt in the cross section of the lifting shape of a wing. The two belts would emerge from the trailing edge, move against the air as if the airplane was moving, and then disappear together into the leading edge. Turn on the belt motors, and the airplane should go straight up even with zero forward velocity. The wing upper and lower surfaces move instead of the air. It's all relative; right?
Since it is such a ludicrous idea, I hereby place it into the public domain.
Unless you start sticking your disk-wing underneath (which would mean a reduction in rotary lift due to the fuselage) the pilot will have really poor view back and above, which is to say the "critical six" which helicopter pilots are taught to shoot down through to kill another chopper. However, having said that, it looks like the disk will be a lot smaller than the span of the equivalent ordinary main rotor, so should be better for getting into small and tight areas.
A helicopter gets lift and thrust by varying the angle of the blades, both across the blade to give lift (pitch via the collective control - normally to the pilot's left) and by tilting the ends up and down using the cyclic (the 'normal' joystick) to tip the direction of lift slightly off vertical - basically the heli moves its own definition of 'up' to include the direction it wants to travel in.
Once this thing pulls the blades in it will need some other method to push it forward as the disc will not be able to generate enough lift to keep it flying without something else to provide thrust to get the speed necessary to get the lift... and the inertia from the whole disc spinning one way is gonna need one hellova tailr rotor to counteract the torque...
Frisbees 'fly' because they catch a pocket of air which they ride on for a very short time - they are only marginally more efficient than a flat piece of wood compared to a 'proper' aerofoil. They are more like hovercraft - they only fly as long as their cushion is there, and they have sufficient forward momentum to maintain it - if you put a frisbee on a spinner, it doesn't take off on its own.
Oh and one final thing - other than publicity stunts, what other shape would a disc be except round??
If you're correct, and they have decent forward propulsion, this could work very well- a spinning disc that works as an aerofoil would provide lift while also providing massive stability thanks to the gyroscopic effect. The back rotor would provide a further stabalising system, meaning that when travelling at a constant speed this would probably be a good, stable platform.
So you've got a quick, highly stable VTOL platform. Sounds exactly what the DOD would be interested in!
I wonder what its radar profile would be like?
Look at the cross-section of an aircraft wing, or a helicopter blade - it's an asymmetric profile. That's the aerofoil shape. This means that even when the blade or wing is aimed level, it still generates lift.
Now look at the spinning disc, and tell me how that can assume the same shape. It can't, since it rotates. It can only generate lift by tilting the entire disc away from the direction of travel.
"Just wondered how much air-to-air chopper combat there has actually been?"
AFAIK, none, apart from exercises.
But the humble chopper *is* a fearsome weapons platform. Fixed-wing pilots are advised that the chopper's air-to-air misslies will be pointed at them 100% of the time. Heli's can hide right down on the deck, lose themselves in terrain, urban clutter or peek over the horizon with their sneeky radar/optronics masts and turn much faster to acquire a target
In all 1-on-1 fixed vs. rotary wing exercises, the fighter / ground attack pilot gets spanked He/she never even lnows what killed 'em.
Chopper vs. chopper would be much more... ...intersting.
S&K, 'cos heli's are deadly.
I dropped an 'n' in "wing" and it came out wig. Close enough, and more amusing.
As to airfoil shape--there's no need for it being asymmetric. At the right alpha and with enough thrust a brick will generate lift. (A common class exercise for young Aero students.) A saucer with the right dimensions is _far_ better than a brick.
Asymmetry has nothing to do with it--you've been looking at too many wing-shape cutaways in books that still say Mr. Bernoulli gives wings their lift since he knows how to match up air flows from the top and bottom of the wing. Mr. Bernoulli helps a bit, but mass flow gets you off the ground.
This could be the next Internet. We could all be flying round in giant frisbees if this thing takes off.
Yes I do remember streethawk, the bike was a road machine when on the road and magically changed into a motocross as soon as it's wheels hit grass or dirt. Amazing!
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