slowrotor ~ this thread's for you

[Dave_Jackson]

An idea :8

In your now closed thread Back door approach for VTOL design (http://www.pprune.org/forums/showthread.php?t=200869) you were considering the possibility of an ultralight fixed wing VTOL. You have also considered the possibility of electric flight.

Here is an idea, or to be more exact, modifications to the previous submitted idea on post #2 of the above thread, in which the suggestion was made to use pre-stored compressed air as the means of assisting the engine during a vertical take off.

The modifications consists of 2 parts;

1/ Replace the proposed gas engine with electric motors. Electric motors are now very light and they are capable of providing 2 to 3 times their rated power for a short period of time. The time of additional power is only limited by the fast increase in the motor's temperature.

2/ Release some of the compressed air through the coils of the motors. This expanding air should have a significant effect in pre-cooling and during-takeoff-cooling of the motors.

Here is a motor for consideration. 20 hp out of a 4.2 lb motor! Plettenberg ~ Predator 37 (http://www.plettenberg-motoren.com/UK/Motoren/aussen/Predator37/Motor.htm)

Just an idea to provoke thought.

Dave


PS. This side-by-side electric rotorcraft (http://www.unicopter.com/ElectrotorGimbaled.html) is a somewhat similar idea that is currently being 'fleshed out'. This craft would be extremely risky but it might provide man's first flight in an electric helicopter.

[slowrotor]

Dave,
I think my idea for a slow evolution from powered assisted STOL to full VTOL is still valid.

At Oshkosh, I saw a C-17 land with power assisted jet flaps. The airplane looks like the giant C-5 but it can land in 1500 feet! More small airplanes should use this.

The Harrier, also at Oshkosh, performs the full VTOL show of course.

Would electric be the best for brief VTOL lift? I am not sure.
I think the motors can supply brief overload about 2 or 3 times rated power.
But the battery pack cannot be overloaded. The battery for brief burst of power is the problem.

An electric ultralight flew at Oshkosh. I did not see it unfortunately.
An electric Sonex was on display but not flown yet.
Electric is evolving.
slowrotor

p.s. I don't think any cooling would be needed for a brief (1 minute)overload on a small electric motor.

[Dave_Jackson]

OK http://www.UniCopter.com/ThumbsUp.gif

[Dave_Jackson]

Some more 'food for thought'.


Idea: :8

Take the specifications for a Very STOL airplane and replace the spars in the wings with long, light-weight, electrically driven, Rootes blower assemblies, to convert the airplane to VTOL.
In other words; Increase the pressure under the wing while at the same time reduce the pressure above the wing.

This is a little more information on the idea. (http://www.unicopter.com/1427.html#VTOL)

This posting is also to put the idea into the public domain.

Dave

[Graviman]

Slowrotor, why not just use a tri-plane?

[slowrotor]

Dave,
I can't tell if your post about the Rootes blower is one your joke postings or a serious proposal.

Mart,
For extreme STOL, we need powered lift to allow flight in the speed range where fixed wings would have little lift no matter how much area. Adding wings is not the solution. Low wing loading makes an aircraft unusable in normal wing conditions.

slowrotor

[Graviman]

Slowrotor, what speed are you trying to achieve for take-off and landing? Does the machine actually need to hover? If it has a cruise speed of <250Kts, then X2 is already showing the way. If you want the machine to be cost effective then a second, or third, set of swing-wings will be simpler/cheaper than a high disc loaded rotor...

[slowrotor]

Mart,
This it what I proposed in 2005.

Back door approach for VTOL design
I am considering a new approach for the design and development of an ultralight fixed wing VTOL. The idea is to build an aircraft that is more or less a conventional fixed wing ultralight and then add vertical thrust devices a little bit at a time. Instead of trying to build a craft that must takeoff and land vertically (very risky), how about a craft that has limited direct powered lift for shorter landings but not vertical?
The wing would take over the job of support in case of power failure so autorotation ability can be abandoned. This would allow high disc loading for the powered lift system.

So, consider an ultralight that stalls at 30mph without any powered lift, then add about 200lbs of direct lift. It would then stall at maybe 20 or 25mph. The test pilot could get very practiced with short landings. Then the next aircraft designs could have more and more thrust until hover is finally achieved. This sort of incremental approach would yield usable aircraft and the interest in the aircraft should remain strong until the final goal is reached. This is the approach the Wright Bros. used when they moved from gliders to powered flight.

[Dave_Jackson]

slowrotor,

The specific idea may not (or may) be practical however the intent was serious.

We probably agree that the wing is the most efficient method for forward flight, and particularly for fast forward flight. I am just trying to think of wild ideas that might be the foundation for, or the inspiration for, a short-duration VTOL addition.

The above is an attempt to utilize the wing as a barrier between a large and controllable, short-term pressure differential.


Dave

[slowrotor]

Dave,
I just assumed that using an pump such as a rootes blower would provide very little lift per horsepower(high pressure, low mass). If you are talking about pressure differential on a flat disc shaped surface.... that sounds like a flying saucer.

Sounds like the Avro VZ-9 Avrocar. They invented a unique lift fan system but it never got out of ground effect.

Keep working on the short term lift system, it has to be the most efficient way to VTOL.
slowrotor

[Dave_Jackson]

slowrotor,

I was hoping that very long, very light, lobes consisting of a carbon composite shell with permanent magnets attached to the inside of their walls might create a high pressure differential that might be better than a 'fan in wing'.
___________________

Anything to get a pressure differential on each side of an extended wing and not just rely on pure thrust.
___________________

Another dumb idea might be to somehow have hundreds or thousands of little 'compressed air vacuum cleaner' type devices located between the upper and lower surfaces of the wings and in the HS. The compressed air comes from a tank. However, the venturi effect of these devices slows the velocity down by taking air from above the wing and placing it under the wing.

IE. Increasing the volume of the airflow and decreasing the velocity of the airflow. Optimally, making the area of the streamtube close to that of the planform of the wing and there by have a relatively low velocity passing through the wing.

This device might run at low power during flight to help with the conventional airflow passing over and under the wing.

Just thinking outside the box, or perhaps, inside the mental institute.

Dave


OOPS! It might be better if you don't go down this road.

If you come up with a means of creating a 9 lb/ft-sq, or less, pressure differential on a wing, then you have just terminated rotorcraft. :eek:

[Graviman]

Dave, your magic carpet already exists:

http://jnaudin.free.fr/lifters/main.htm

These work by ionising the air then using the electric field to create induced flow. At some point these guys will stop wasting time with triangle shapes and just go for a compact grid. Best if the wires are aerofoil shaped too, to minimise parasitic drag on the induced flow.

This technology might approach the helicopter for payload capability.

Slowrotor, you are absolutely right that the key to any of this is too minimise the mass for a given lift. Helicopter currently wins hands down over Coanda effect or ducted fan designs. If you include the main gearbox and anti-torque device then wings have better performance.

Still, good to think outside the box.

[Dave_Jackson]

Mart,

Many years ago, I brought this subject up on another forum in respect to AoA control. The idea was to ionize the air in front of an airfoil and then use magnetism to direct the air over or under the airfoil.

An unnamed professor at the University of Maryland (not Leishman) replied and said that only the impurities in the air could be magnetized.

I ate crow and gave up. :uhoh:

Dave

[Graviman]

Dave, the electric field works because the wire diameter is small. This causes a very high local e-field which ionises some component of the air. Your professor may be right that it only works on dust particles, and not the air itself. So far only very light structures have been demonstrated... :hmm:


If nitrogen could be ionised, there might be potential at supersonic speeds. The electric field would guide the ionised air to avoid the conventional shock wave, with consequent reduction in noise signature. I suspect the power requirements are prohibitive though. Besides a better approach is to build up the shock in smaller weaker shock waves, for example using a staggered pitot tube.


Still, good to think outside of the box...

[slowrotor]

Mart,
I think you meant to say "maximize the mass" in post #12.

But for the short duration lift that Dave and I are seeking, we really don't need good energy efficiency, for short term "who cares about efficiency".
It just needs to be possible.

[Graviman]

Slowrotor, i mean that the mass of the lifting system should be minimised for a given payload capability. The reason that all the wacky ideas out there, like ducted fan main rotors, have not got to market is because they are significantly more massive than a rotor. This nibbles into payload/fuel/range/etc...

I understand that you are trying to combine good range performance with VTOL at each end. The best solution is to copy the Joint Strike Fighter, which has similar objectives (albeit at much higher speeds). If you are not careful you will compromise the fixed wing efficiency.

What you need to clarify is the intended take-off and landing profiles. If a fault develops with the high diskloaded system the aircraft will fall horribly to the ground. The JSF is a military machine, and so is driven by mission requirements. Your civil machine will not have any autorotative capability - this means that the VTOL systems have to be ultra dependable/failsafe.

[Dave_Jackson]

From Wikipedia;
"A related technology development is the tiltwing. Although two designs, the Canadair CL-84 Dynavert (http://en.wikipedia.org/wiki/Canadair_CL-84) and the LTV XC-142 (http://en.wikipedia.org/wiki/LTV_XC-142), were technical successes, neither entered production due to other issues."


These craft are well known and so are their problems. However, the future is looking more and more http://www.unicopter.com/Lightning.gifelectrichttp://www.unicopter.com/Lightning.gif. The short-term high-power output of electric motors, combined with their good power/weight ratio may give cause to rethink the tilt-wing.

http://www.unicopter.com/lightbulb%20idea.gif
Long cord for prototyping tiltwing until improved batteries arrive.

Dave

[Dave_Jackson]

.... and another idea. ~ the Microraptor.

The Abstract (http://www.pnas.org/cgi/content/abstract/104/5/1576)
The full version - PDF file (http://www.pnas.org/cgi/reprint/104/5/1576)

slowrotor,
..http://www.unicopter.com/Idea.gif
Before you laugh and hangup the phone, consider for a moment, the possibility of implementing nature's microrapter into a man made S/VTOL craft.

The legs (airplane landing gear) have winged feet (small airfoils near the bottom of the landing gear).

In forward flight; the small airfoils and feet (AF) are located aft and are providing lift.
To slow down; the AF are swung down and forward to act as a biplane.
To land; the AF are swung further forward, which flares the craft and sets the feet up for landing.
For jump takeoff the AF are quickly move down and back from their landing position. This also puts the AF into position for cruise.http://www.unicopter.com/NoIdea.gif


Dave

[slowrotor]

Dave,
Did you watch PBS NOVA last night about the four winged microraptor?
They showed models in the wind tunnel at MIT and many other interesting things about how birds learned to fly. For instance, wings can help a bird to climb a tree by lifting a portion of the load as the claws provide the balance.
slowrotor

[Dave_Jackson]

You are a jump or two ahead.http://www.unicopter.com/ThumbsUp.gif

Yes. The PBS NOVA show is what started the thinking.

[Graviman]

Dave, i hate to break it to you but the dinosaurs are extinct. My own theory is that they died out due to mechanical complexity and poor payload-range performance. :E

Actually, a peculiar fact of nature is that it never evolved any rotating systems (outside of several microscopic examples). So if birds had evolved rotors instead of wings what would they look like?

Slowrotor, i'm still trying to figure out what the typical mission profile of your machine is? Are you trying to achieve fixed wing efficiency/range but with limited endurance VTOL landing? Even with a turbo-piston engine you will struggle to get much speed. :confused:

Basically i don't understand why you are rejecting the rotor as a main source of lift? Why not go the other way and design a rotor with large enough blade sections to handle lift at zero RPM. Then you can play with variable rpm counterrotators without any fear of rotor resonance...

[Dave_Jackson]

Mart.

What is neat about the Microrapter is the functional association between the location of the feathered feet and the flight attitude.


a peculiar fact of nature is that it never evolved any rotating systems http://www.zylex.geek.nz/tumbleweed.jpg :E :)

Dave

[Graviman]

Hehehe - that picture made me chuckle!

[AOA2007]

the only other I can think of is the sycamore seed

[Graviman]

Hmmm, didn't think of that.

Perhaps what i should have said is that nature never evolved any stator-rotator systems. This includes wheels, rotors, propellers, motors and in fact anything which requires roller bearings and seals to work.

Even here there are some single cell examples of chemically driven rotating motors.
http://ourworld.compuserve.com/homepages/dp5/flagellum.jpg
http://www.allaboutthejourney.org/microscopic-organisms.htm

The so-called "bacterial flagellum" is what propels a bacterium through its microscopic world. The bacterial flagellum consists of about 40 different protein parts, including a stator, rotor, drive shaft, U-joint, and propeller. Through 21st century magnification technology, we now understand that a simple bacterium has a microscopic outboard motor! The individual parts come into focus when magnified 50,000 times using electron micrographs. These microscopic motors can run at 100,000 rpm. Nevertheless, they can stop on a microscopic dime. In fact, it takes only a quarter turn for them to stop, shift gears and start spinning 100,000 rpm in the other direction! The flagellar motor is water-cooled and hardwired into a sensory mechanism that allows the bacterium to get feedback from its environment!

http://en.wikipedia.org/wiki/Flagellum

[slowrotor]

Graviman,
To address your question:"Slowrotor, i'm still trying to figure out what the typical mission profile of your machine is? Are you trying to achieve fixed wing efficiency/range but with limited endurance VTOL landing? Even with a turbo-piston engine you will struggle to get much speed."

I think the bird flight discussion here is a good start.
Consider the hummingbird to be the natural world equivalent of the helicopter. The hummingbird burns more fuel than a seagull because it stays in rotary wing mode. The seagull can maintain forward flight with occasional power strokes between energy saving glides and is more efficient. The seagull cannot hover for more than a second, I think, but this brief hover ability is all the seagull really needs to land on a rock perch.

A brief hover is all that is needed for a fixed wing. And if a hover is not possible in the first edition, direct lift is still useful in that the landing run could be as short as a few feet. In fact, it might be better to forgo attempts at hover as this requires additional complex control ability.

I was in a Pilatus Porter turboprop fixed wing that landed on the muddy tundra of Alaska in an area about the size of a tennis court. The pilot locked the wheels to eliminate mud flinging and applied full reverse and we stopped in about 50 feet it seemed.
The seagull lands in a similar manner, gliding in with a burst of reverse thrust just before touchdown the same as the STOL airplane. But the seagull also has brief LIFT added with reverse thrust and is therefor capable of a shorter landing. This extra lift, directed up and rearward is what I seek to provide, only needed for a few seconds. Turned forward and upward these lift fans would provide a quick launch.

Does this make sense?
slowrotor