Can we achieve practical personal flight with current options?

[dragoneyes001]

the more i think about a ranch use the more I'm inclined towards a simple type of helicopter which doesn't need a few thousand hours of flying time to master.
also small enough to range alone but able to link with other units to become a large weight hauler.

 

[mheslep]

Power source: ... Electric will be better, but until you can make something more energy dense than the lithium ion battery

Electric fans/props and batteries work, the problem is range. I believe max range is ( Cbatt/g ) * battery mass fraction * efficiency * (L/D), where C is the battery capacity in joules per kg; L/D = lift/drag is best case 30 (global flyer); mass fraction maybe 70%. For the current best 1 MJ/kg batteries, range is then ~1600 km. That's short range compared to large commercial aircraft, but for a personal single seater I doubt many people want to travel that far in one hop. Ceiling would be interesting.

 

[HuskyNamedNala]

There are some pretty technical considerations and it comes down to the propulsion system. Unless you want to give a person a 20-30 foot wingspan you need to generate enough thrust such that you can obtain sufficient lift, while over coming drag (which won't be trivial since a person can be approximated as a rectangle), for an extended period of time, that is also lightweight... and safe.

The only thing I can think of is rocket propulsion to get the person to altitude, then a high efficiency propeller for cruise. Interestingly, there is a "jet pack" that uses pumped water at a high velocity to generate thrust. You are limited by the hose and head loss, but it is pretty neat. This makes sense too, as the density of air is just under 1000 times higher than air, and thrust generated by an accelerated column of fluid is approximated by
rho*delta(V^2 *A).From an aerodynamics standpoint I am a big fan of biplanes (even though they went out of style a hundred years ago I think with composites they can come back), which would maximize lifting surface area without occupying too much space. A good biplane design can obtain about 30% more lift with double the wing area. I think with the right stagger and a reflexed airfoil you could overcome stability issues too. MIT developed a human powered aircraft that used flapping with technology. It cruised about...1 foot above the ground with 1 human as a payload.

 

[Dale]

I want to talk about personal flight options. I have searched in, and external to, this forum and understand there are various types of options currently available. However I'm not sure they are truly practical to usher in a new era of personal flight.

Why personal flight? I cannot think of a good use case for mass personal flight. If you are talking "practical" then there has to be some practical use case.

For commuter transit an infrastructure based approach will be cheaper and safer. With the 15 minute flight time it seems unlikely to satisfy either business or leisure travel needs. For ranchers it is hard to see how you could beat a 4x4 truck. Etc.

Until you know what problem you are solving you can never tell if a solution is practical.

 

[timthereaper]

Why personal flight? I cannot think of a good use case for mass personal flight. If you are talking "practical" then there has to be some practical use case.

For commuter transit an infrastructure based approach will be cheaper and safer. With the 15 minute flight time it seems unlikely to satisfy either business or leisure travel needs. For ranchers it is hard to see how you could beat a 4x4 truck. Etc. Until you know what problem you are solving you can never tell if a solution is practical.

My views exactly. For people that would have a good use for a personal flight vehicle, they can buy a plane/gyrocopter.

 

[GTOM]

I also wondered about the option of flapping wings, whether it is more energy efficient (for low speed and altitude at least), or not?
Gliding is more energy efficient than constant thrust (compared to a jetpack), with flapping wings, lesser runway is needed.

Well i could sure accept such a thing for leisure at very least.

 

[HuskyNamedNala]

Flapping wings are only applicable to low Reynolds number applications. Check out the MIT PhD project published within the last 5 years.

 

[Dale]

Well i could sure accept such a thing for leisure at very least.

What would be the use case? Are you talking about traveling to a leisure destination or are you talking about a "joyride"?

If the former, then what destinations could it serve that are not already served. If the latter, then what are you looking for that hang gliding etc does not already provide.

 

[anorlunda]

Baluncore,
The loss of power issue I think is best handled with a parachute. They are simple, small, proven over time. No reason not to have one as a last resort.

The sad fact is that parachutes that land in trees or anything other than open ground often result in injury or death to the passengers or to people on the ground. Parachutes are worthwhile to carry, but they are no solution to safety. If you are flying lower than 1000 feet, a parachute may not have time to deploy. An ER nurse told me that the number one cause of injuries locally are paragliders that lose power over wooded areas.

As for "advanced controls" as a throw down trivial solution to real life problems, Airbus 320 comes to mind. All the kings horses and all the kings men may not be able to design advanced controls that will save Humpty Dumpty.

 

[Syed Ammar]

What I think at this point after going through all the post and its replies, is a solar-aircraft with fold-able body, with high storage power batteries. If carrying power with you is a hurdle, why not put up a solar station (in geostationary orbit and elsewhere, just suggesting) and use microwaves to beam it to your required machinery?
hyteck9,
The traffic, security and political problems ( Blah bla bla) will have to be handled later ( Politicians across countries never agree to anything good anyway :3 ) . What really matters here is the science involved behind personal flight.. And it is also a point to be noted that personal flight (until an extremely efficient power source is discovered) will be limited only to entrepreneurs and the "BIG SHOTS".

 

[Ryan_m_b]

What really matters here is the science involved behind personal flight

Actually I think Dalespam highlighted what really matters here: unless you can fully identify and characterise a problem you can't envision a sensible solution. This thread seems to be trying to merge two separate conversations poorly;

1) The interesting and perfectly legitimate discussion on how personal flight could be achieved through current science and technology

2) The discussion on how to overcome the impracticality (economic, legal, safety) of personal flight

I think it's pretty clear to most people that widespread personal flight is a non-starter due to a host of reasons related to point 2. That doesn't stop it being a fun exercise discussing how to do it and under what niche circumstances it might make sense but slotting the two together is putting the cart before the horse.

 

[nitsuj]

Hmmmm...Futurama seems a fairly accurate prediction of future travel. So for inter-city travel it will likely be tubes with a vacuum. Maintianing body position is important.

piloting personal flight devices must be so fun and exciting. And they all seem to have "fail safes" implicit in the design. Such as gliding ability or a parachute.

why no massive paracuhte for passenger jets, for those situations where it's clear a crash is going to happen. Surely there is a "frame" of sorts that the chute could attached to, same as the what ever the seats are attached to. Surely it's been toyed with, I wonder the issues with it.

 

[timthereaper]

I think it's pretty clear to most people that widespread personal flight is a non-starter due to a host of reasons related to point 2. That doesn't stop it being a fun exercise discussing how to do it and under what niche circumstances it might make sense but slotting the two together is putting the cart before the horse.

Agreed. It seemed the OP wanted more than to discuss current technologies that could have applications in personal flight. The problem is that to mature any promising ideas we have to look at the most practical use case scenario and base all our tradeoffs on that, and there is no accepted practical use case scenario. That means we keep bouncing between points 1 and 2.

 

[dragoneyes001]

if you look at the four propeller drones hobbyists fly around making one large enough to carry people while not making a military sized unit would be a possibility for this application. it could be electric. the controls would need to be self leveling for ease of flying it so tilting rotors to accelerate and slow flight with enclosed rotors for additional safety. the big issue is how to create a safe loss of power decent.

 

[GTOM]

Flapping wings are only applicable to low Reynolds number applications. Check out the MIT PhD project published within the last 5 years.

Cant it be solved with better components? Feathers are hard to mimic.

If the latter, then what are you looking for that hang gliding etc does not already provide.

That requires starting from a high place.

Otherwise, an energy efficient way to fly above traffic jams wouldn't be bad, if it can be solved. (We got a number of them in our country.)

 

[GTOM]

What would be the use case? Are you talking about traveling to a leisure destination or are you talking about a "joyride"?

If the former, then what destinations could it serve that are not already served. If the latter, then what are you looking for that hang gliding etc does not already provide.

I have to correct my last answer. So yes, there are multiple options, airplane and glide once you are up, start from a mountain, dragged by a fast land vehicle.
But IMHO, nothing as good as take off on my own, and theoretically, even able to land in our garden.
I wrote about the other application i can imagine in the previous post.

 

[meloettakawaii]

Here's my proposal:

Lets first understand and mimic what nature did because nature solves problem oh so well.

The goal is a bird form factor scaled to the size of a human.
The pilot will strap on an exoskeleton with collapsible wings just like the birds for space saving and wing controls.
The pilot will have full range of control over the wing's degrees of freedom similar to how birds can rotate, extend, bend, manipulate each of their wings independently.
The exoskeleton amplifies the pilot's actions therefore enabling vertical takeoff like birds, or with the assistance of a quick dash and a jump.
The exoskeleton plus the pilot will have a center of gravity precisely balanced so that in freefall, and movement of the wing / other body parts would change the flight trajectory.
Materials used to build this would be high strength to weight ratio such as titanium, carbon fiber, etc.
Actuation would be artificial muscles, (coiled nylon/fishing wire?, pneumatic?, etc.) must be lightweight
Power source at this point would high density batteries or if you have a better option that better with work to weight ratio.

what do you think?

lets not get into the non-technical issues, if this can be build today, the world would bend around making this commercially available.

 

[king_me]

Self driving cars will be implemented, the steering wheel will eventually be removed & algorithms to control this ‘network’ of vehicles will be finely tuned over an extensive time period.

This is how the air space will be controlled, by the program that controlled the cars but reconfigured to work in the air. That or Amazon, Google with their drone delivery service.

Whatever is built can not be driven by humans, at all…ever.

85% of the safety is now taken care of but needs a decade+ to take effect. The last 15% is the risk factor in the flying unit itself.

Flapping:
You could genetically modify a person to have wings and fly but hell…all you would do is eat & sleep to get the energy to flap. Could you train a bird that was big enough to carry a person? It would rather eat you and if you ever got on it the takeoff & landing would be extremely violent.

Fixed wing:
Buy a plane and go fly it. Gliders are n/a.Gyro:
It’s a small helicopterRocket:
Kaboom!Turbine anything:
Old technologiesParagliding:
Motor & a propeller on the back and all you need is a head wind. N/A…requires human inputDrones – battery powered:
You can scale it up all you want but I’m not getting on it.

But hey, we’re talking The Next Level…………….3D printing: (basically teleporting)

You need a scanner to record your body (destroying it in the process) then wirelessly sending the signal to the other booth… less than 15 minutes but hey, you’re flying right!? (can you get to the moon in 15 minutes as a signal?) Ultimate in personal flight! Can you say we’re not heading in that direction in regards to the printing? It’s the recording that we’ll have issues with.

Is teleporting too far off the subject? My brain can go off on a tangent sometimes.

 

[Baluncore]

Gyro:
It’s a small helicopter

No.

A helicopter has a powered rotor, air is driven down by the main rotor. A tail rotor counters the torque. Rotor blade angle is controlled by the pilot through a swashplate. The axis of the main rotor is fixed relative to the body. A helicopter leans forward to fly forward.

An autogyro has an unpowered rotor, air moves up through the rotor. The rotor is much like a glider. There is no control of blade attitude as that self-adjusts on a rocking bar. The body hangs from the rotor, the pilot controls the relative axis of the rotor and body. An autogyro is usually pushed along by a propeller. It leans backwards when flying forwards so air will move up through the gliding blades.

 

[king_me]

No.

A helicopter has a powered rotor, air is driven down by the main rotor. A tail rotor counters the torque. Rotor blade angle is controlled by the pilot through a swashplate. The axis of the main rotor is fixed relative to the body. A helicopter leans forward to fly forward.

An autogyro has an unpowered rotor, air moves up through the rotor. The rotor is much like a glider. There is no control of blade attitude as that self-adjusts on a rocking bar. The body hangs from the rotor, the pilot controls the relative axis of the rotor and body. An autogyro is usually pushed along by a propeller. It leans backwards when flying forwards so air will move up through the gliding blades.

Oh yeah that's right! How silly of me.

 

[Ryan_m_b]

Here's my proposal:

Lets first understand and mimic what nature did because nature solves problem oh so well.

The biggest reason why this won't work: the square cube law. You can't scale an object up and expect it's characteristics to be the same as the volume increases faster than the area. In the case of birds this means that if you double the size you have double the wing area but four times the mass to lift.

lets not get into the non-technical issues, if this can be build today, the world would bend around making this commercially available.

Saying "let's not talk about this because I'm right" is a bit of a poor thing to do. Regardless the non-technical issues are probably more important than the technical ones in this case. We can build things like jetpacks and whilst they aren't very good they could feasibly be made. But the issues of safety and economics massively favour not doing this.

 

[Ryan_m_b]

Is teleporting too far off the subject? My brain can go off on a tangent sometimes.

Yes it is very off topic. Can members please remember that this thread is under the same site rules as any other. Keep all proposals to technologies that have been demonstrated to be possible, if not economical.

 

[meloettakawaii]

<< Comments deleted by Moderator >>[/color]

 

[timthereaper]

<< Comments deleted by Moderator >>[/color]

Good luck with getting that kind of contraption commercial. There might be someone like a Chuck Yeager willing to follow you up into the sky on a wing and a prayer, but no one in their right mind will pay you for that.

lets not get into the non-technical issues, if this can be build today, the world would bend around making this commercially available.

So again, what's your use case for this exoskeleton/wing vehicle? I agree that personal flight may have good military applications, but so does a tank and we don't see those riding down the street every day (unless you're in Crimea/Syria/Afghanistan/a military base). A strong commercial use case is a very non-trivial thing. Even if you could somehow build this thing tomorrow, for the world to bend around to make this commercial you have to show the world it needs this.

 

[berkeman]

This thread is closed for Moderation...

Thread re-opened. Let's all keep in mind Ryan's comments. We discuss mainstream science here on the PF.

 

[NTW]

Since a gyro has no tail rotor to counter the torque, that coupling is only possible during initial "spin-up" on the ground.

If ram jets at the tips of an autogyro's blades are used then you have a helicopter and the airfoil angle of attack must be reversed. A helicopter requires a swash-plate to control pitch. An autogyro flies forwards with nose up so air flows up through the blades causing them to "auto-rotate". The autogyro blades are then effectively gliders providing lift. A helicopter flies forwards with nose down as the blades push air down and backwards. The transition between those distinct modes is quite dangerous as the vehicle must fall through the low airspeed period without lift while the blade angle of attack is reversed.

I agree with everything you're saying here, and just wish to make a small comment: at the transition between 'helicopter mode' and 'autogyro mode', the blade angle of attack is not reversed, but just reduced, as autorotation takes place with positive angles of attack at any station of the blade.

Both helicopters and autogyros fly with positive angles of attack, as the relative wind is 'seen' from any station of the blade. If a helicopter has engine trouble, the pilot usually resorts to autorotation to glide safely to the ground, and in order to keep the rotor in autorotation he reduces the pitch to the optimal autorotation value, but the AoA is kept positive...

For the same reason that the wing of a glider has always a positive AoA, the autorotating rotor blade has to keep a positive AoA...

 

[Baluncore]

Thanks for the incisive analysis. I agree that “angle of attack is reversed” should be replaced with “angle of attack is reduced”.

So, if angle of attack is only reduced, then what is reversed to flip between the two distinctive modes?
Consider the airfoil lift and drag forces on a blade relative to the plane of the rotor disk. The vector sum of those forces on a driven airfoil is a backward leaning upward vector. On a glider, or during auto-rotation, it must become a slightly forward leaning upward vector. That requires a reduction in AoA. It seems that some lift is being sacrificed to overcome drag and so provide auto-rotation.

 

[NTW]

For every helicopter, there's probably a pitch setting that gives the best autorotation. That pitch is lower than the 'cruise pitch', and I'm sure that the manufacturer provides that vital information in the pilot's manual...

The 'helicopter mode' is not radically different from the 'autogyro mode'. In the latter, the rotor does also provide the lift, the rotor being indirectly powered (one can think in a 'pneumatic transmission' from the engine driving the propeller) by the relative wind produced by the movement of the aircraft.

In the very simple, present-day gyros, during the 'spin-up', the weight of the aircraft is slightly reduced, because the rotor is producing lift... The revs don't reach the critical value (the one usual in level flight), both for mechanical reasons (the pre-rotators, as they are called, are not built to transfer so much power, and a gyro rotor is not built, either, to withstand a very high torque) and because that could cause an unintended take-off and an accident.

 

[Baluncore]

For every helicopter, there's probably a pitch setting that gives the best autorotation. That pitch is lower than the 'cruise pitch', and I'm sure that the manufacturer provides that vital information in the pilot's manual...

It all gets a bit debatable. Unlike common propellers, the typical rotor blades of helicopters and autogyros have no twist along the blade. At any point in time, part of the blade is auto-rotating and part is driven. Those parts and the section between the two is producing lift. It is the sum of all the effects that decides performance. The active region may be centred at different radii at different points of the rotation cycle.

If you cannot get rotation in an autogyro without a pre-rotator, then it is probably unsafe to lift off. I have designed and evaluated autogyro pre-rotators and now believe them to be an unnecessary complexity.

Having just examined the discarded blades from an autogyro and a helicopter I notice the helicopter blade has a symmetric airfoil while the autogyro has an asymmetric profile. I assume that is because the helicopter blade must operate in both modes while the autogyro blade is always auto-rotating.

 

[NTW]

Present-day gyros use simple blades, without taper or twist. Helicopter blades are sometimes more complex, and that may mean a difference in the distribution of the driven/driving regions of helicopter and simple gyro rotors while in autorotation. Concerning the airfoil, an important consideration in helicopters is the movement of the center of pressure with pitch variation, so that feathering forces may be kept kept within limits, and that favors the symmetrical profile, where pressure center travel is short. In gyros, the choice of airfoil is directed to optimize autorotation.

But nothing of the above affects the main point; namely, that the rotor in autorotation is essentially similar to the engine-powered rotor. Hence, only a pitch reduction adjustment is necessary to pass from the 'engine-powered rotor' condition to the 'wind-powered' auto-rotating condition. They are different, but not 'reverse' conditions, and share a positive (if also different) angle of attack. Both are, after all, rotating-wing lifting devices.

The two gyros that I have flown had mechanical pre-rotators fitted. I have seen people spinning the rotor of their (lighter) gyros first by hand, and then taxiing 'to get revs' till they reached enough rotor speed to take off. But that's primitive and may cause blade sailing and much hammering of the stops...