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Practical personal flight

  1. Jan 16, 2015 #1
    Hello to all,
    This is my first post, other than the introduction of course. 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. The Martin Jetpack is just enormous with limited direction and range and JetMan can't really take off and land as one would going to and from work every day. So how do we take it to the next level of usefulness? By asking good questions, that is how. Let's focus on individual components of the engineering and build up, rather than deconstruct what others have done top down. A few categories to get started:

    Power source: electric , liquid fuel, solid fuel, other? Why? Weight vs. work potential? Practical availability and cost?

    Thrust mechanism: Rotor, turbine, rocket? Why? Safety over size? Control and agility over speed?. What about a combination?

    Form factor: Backpack , minimalist pod, flying car? A backpack or open cockpit is only a good weather device, but would flying cars be grounded in bad weather anyway, either by FAA or common sense of self-preservation?

    I will define practical flight as a 15 minute minimum flight time with easy take offs and landings, plus it must fit in a 10x20 parking space.

    I think that is enough to get started on. Please feel free to chime in on any or all of the subject areas. Support your choice logically and/or highlight what is holding us back in a certain area with examples. (this is fun!)
  2. jcsd
  3. Jan 16, 2015 #2
    Are we assuming that personal flight is a viable option? Because I don't for a variety of reasons. But with that assumption:
    • Form: I would think aerodynamics and basic safety would rule a jetpack out. It might have to be a flying car simply because you might want to pack stuff with you if you're going anywhere appreciably far away.
    • Power source: Until newer technologies develop, gasoline is really the only thing that's affordable enough with enough energy density to get everyone places. That's the real problem with trying to get away from fossil fuels. Electric will be better, but until you can make something more energy dense than the lithium ion battery, you're stuck to black gold/Texas tea.
    • Thrust mechanism: There's been too much research into turbines to make it much else commercially viable. Safety is the biggest issue and I can't see a company risking it all on a new technology that hasn't been proven. Plus, I can't see anything else competing for efficiency. Turbines are getting more efficient all the time.
    IMHO, the real barriers are non-technical. There are a lot of other problems you have to solve first in order to make personal flight vehicles a practical reality.
  4. Jan 16, 2015 #3
    Thanks for the reply. Please elaborate on the hurdles you perceive. I'm interested.
  5. Jan 16, 2015 #4
    Like I said, the problems are non-technical:
    • Complexity: Some people have trouble driving a car constrained to a flat plane. Think about your daily drive. How many people do dumb things all the time when you drive places? Cutting people off, speeding, going reeeallllyyyy slow. If some people can't control a vehicle in 2D, adding a third dimension would just blow their minds.
    • Safety: With flight, you can't have a fender-bender. It's really all or nothing. Making a vehicle light and strong enough to survive a crash are almost exclusive to each other (I said almost). Modern cars can handle crashes, but that's at 55 mph. Imagine adding a fall from some height above 400 feet.
    • Police: Staying on a predetermined flight path would be hard to enforce because you know there would be some idiot that would veer off to "explore". With the sheer number of extremists out there, flight just offers another way to cause mayhem. Plus, how do you "pull over" or set up roadblocks for a plane?
    • Distractions: We can't get people to stop texting and driving. Texting and flying?. Flying under the influence (FUI)? I shudder to think.
    • Maintenance: maintaining a car is tough enough for some people, but making a vehicle flightworthy is SO much harder. Plus, pilots are ultimately responsible for the vehicle they fly in. I knew experienced test pilots that died because they didn't realize the maintenance crew installed some of the control surfaces upside down. Experienced test pilots. Can't imagine Joe Blow doing a diligent preflight on a daily flier, especially if he's late for work. Some people don't even scrape the ice off the windshields on cold days.
    • Distance: Planes burn up a lot of fuel during takeoff and climbs. To make it worth that fuel cost, you'd have to be traveling pretty far.
    • Air traffic: Air traffic control would be hard. It's hard enough with as many planes take off from certain regions. Can;t imagine how congested things would get by adding even 2-3x the number of vehicles. Even though you could add more regional airports, you'd still have to deal with the air traffic routes around the city. You can't just take off, land, and fly over any part of the city you'd like.
    • Infrastructure: You'd have to regulate all the air traffic somehow. That would necessitate more air traffic controllers, more airports, more FAA (!), etc. We have trouble maintaining all the roads, bridges, tunnels, etc. for cars. I can't see us pouring money into infrastructure for flight. Also, there would have to be a better regulatory system for licensing than for cars. It's not a major hurdle, but there would definitely be more pilots than now if flight was more affordable.
    • International air traffic: Mainly for people who live close to other countries. How would you make sure Florida pilots didn't "accidentally" fly into Cuba? Or Cuban pilots into Florida? Or South Korean pilot into North Korea? It would cause an international incident.
    • Vehicle Cost: This veers a bit into technical, but if all the relevant systems were installed and safety features were in place, would this end up costing more than just owning a car AND a plane separately? Plus, if you want the car to drive as well as fly, you'd have to make an internal combustion engine drive a turbine, or a turbine power a drivetrain. Or maybe have both, but then you'd never get it to fly because of weight.
    There are probably more than these concerns, but I can't think of anything else right now. IMHO, if you can solve those problems, then the technical ones will be a breeze.
  6. Jan 16, 2015 #5
    ah ha! Now this is fun stuff to talk about. :) Thank you for talking the time to type out a detailed response. I actually feel technology 'can' solve a lot of those issues. Other solutions may require a departure from our current flight standards. Here are my initial thoughts.

    Complexity to operate: I would offer that tHis can mostly be solved by technology with features like intuitive controls, auto hover, even object avoidance and other such features are now found in toy drones. I Agree that different government licensing would be required to make sure the person is capable.

    Infrastructure, Air traffic, police: Perhaps what we need is a system designed to work within itself. All vehicles are software capped at max alititude of 400 ft, GPS tracked, aware of other vehicles + the afore mentioned object avoidence and "emergency zones" etablished for landing vehicles who's computers read anything out of spec. Police can also "OnStar your ride" and kick on the emergecy zone protocal forcing the vehicle to land. Sure, any software can be hacked, but bad people will always do bad things.

    Safety: I think with advanced features, proper licensing, and inteligent diagnostic onboard systems it is about as safe as one could hope for. People die in car crashes all the time, but cars have very limited 2D options to get out of the way too.

    Maintenance: I had not speficically considered this, but as part of the licensing I would think a vehicle inspection is needed, perhaps annually. If the vehicle is not reliable to make it a full year for an inspection, it is a design flaw.

    Cost: Tesla is selling electric cars for $120k and people are buying them. Is that practical? hard to gauge this question at this point I think.
  7. Jan 16, 2015 #6


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    Seems like the most practical possibility would be a gasoline-powered ultralight aircraft with some folding/compacting capabilities. It would be a good idea to enclose the prop in a cage, and use computer flight and navigation controls, so the person using it did not need to be a skilled pilot.

    That would still require some organization of places to take off & land, but things like sections of parking lots could be used for that, perhaps.

    Something like this:

  8. Jan 16, 2015 #7


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    Safety requires reliability under “loss of power” conditions. The solution is available now, it has been developed over the last 150 Ma; called birds, they have two wings and a tail. Efficient personal flight will require an efficient wing, as a powered glider. Present machines need have propellers and fast IC engines to keep the weight down. With time, variable geometry wings will become more common. Then, as efficient propeller speed falls we will reach the point where flapping the wings will become a better and safer solution.

    Fuel will always be a problem. Aviation up to now has been dependent on liquid fossil fuels. A change to something like ethanol or hydrogen can be expected. The engines or actuators that convert fuel to movement will change once flapping wings appear.
  9. Jan 17, 2015 #8

    Wes Tausend

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    A recent PBS episode (Ep 4, Season 5) of The Aviators included a segment about Jet Man (Yves Rossy) and a jet-powered strap-on wing he wears for airshows. The carbon wing straps on like a backpack and is powered by four Jet-Cat P200 jet engines modified from large kerosene-fueled model aircraft engines. Rossy can do aerobatics, including loops. He launches from other aircraft.

    The most significant part of this for you may be the modified jet engine innovation since it seems a slower "commuter" craft might more practically fly with two engines (or one) with at least twice (or four times) the range.

    Links: http://en.wikipedia.org/wiki/Yves_Rossy, http://www.jetman.com/

    A related arial quick get-to-work method might be a self-powered cable-car network strung diagonally above cities. I suppose traffic blending first-come/first-served like the freeways below, only suspended by cable.

    Steering concerns are removed if the cars automatically "switch track" (cable) on a predetermined route demand. Remaining movement safety then becomes a matter of adapting ordinary train anti-collision that has come in to vogue as of late. As a compromise, high speed cables may cost less than concrete and be more reliable than sky hooks hooked to stormy, wandering air, yet offer an exciting ride. Of course wear on the cables could be greatly reduced by super-cooled magnetic levitation while we are imagineering.

  10. Jan 17, 2015 #9


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    One does not see too may birds, if any, flying in bad weather.

    Planes will have the all clear ( and this is from a combination of input from the aircraft company, air traffic control, the airports-ground control and pilots ) on whether they can takeoff. It is not just the weather at your own location that is pertinent, but also the weather at your destination. Even with a short distance hop of only 15 minute flight, local weather patterns would have to be known.

    Wind, rain, snow, icing, freezing rain, fog, nighttime are all going to play into the decision to takeoff or not. The preparation time could jump drastically in a lot of cases.
    Freezing rain for example is combated at airports by the showering of the plane with several de-ice mixtures ranging from the cheaper to ultra expensive. Would a personal user know how to apply, and have the storage space available for the liquids.

    I would imagine that, when it is all said and done, only about 100 days out of the year, depending upon location, would be conducive for an owner to be able to fly with his personal craft without undue pre-prep, regarding the weather.
  11. Jan 18, 2015 #10
    I've always wondered why a small helicopter wouldn't incorporate an articulated nacelle surrounding its blades. This should improve efficiency and safety while allowing for the use of vectored thrust for directional control (in addition to the rear rotor and main rotor articulating blades). This could also allow for the stacking of rotor blades, the primary purpose of which would be to maintain required thrust within a smaller diameter while reducing the weight of the nacelle itself by making it smaller. I believe the primary issue with this has been one of added mass, but the use a lightweight alloy or an FRP (epoxy carbon/Kevlar/etc.) might change that equation, along with the cost equation too. Of course, the use of a nacelle might also reduce the area of unintended incidental impact, and so reduce the surprisingly rare incidental rate of decapitation, which would become a much more important safety factor when parking/landing in midtown Manhattan. Which also brings up one of the primary issues of mechanical man in flight, the safe landing, which many aviators define as a controlled crash, and which might well be a situation that would always require some sort of dedicated/independent ground facility specifically equipped to deal with large man made objects falling from space...see recent Space X barge booster landing...
    I think the surprising lack of large scale public engagement in general aviation has a lot to do with this specific function, and that most folks who've controlled a plane find the takeoff thrilling, if not transformative, the elevated view of the world around them inspiring and that flying something like a light plane into the ground is counterintuitive at best, and damned challenging (frightening) in a gusting 40MPH crosswind. So I'd say that conquering that matter would be perhaps the primary challenge, which might be well addressed by the emerging, or merging technologies associated with the autonomous (pilotless) automobile (vehicle). And a helium inflated parachute.
    Which gets me around to the 'flying parachute', which might be the best option currently available, due in part to the fact that's basic functioning design relies on the alternative to an impossible landing, and it lands at walking speed, literally. BT
  12. Jan 19, 2015 #11
    Someone was trying to build some vertical takeoff gyro copters a few years ago,
    one used ram jets at the ends of the blades, the other weights.
    The weighted blades would be feathered and spun up using axillary power from the
    pusher engine. Once up to speed the blades could tilt to catch the air, the
    inertia would jump the craft about 70 feet in the air.
    I bet it would be a thrilling ride!
    I found a youtube of this actually working,
  13. Jan 19, 2015 #12


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    “Practical personal flight” must be safe, economic and quiet. Unfortunately, any exciting mode of transport will be dangerous.

    Gyrocopters / autogyros have not yet stopped killing their operators. The insurance of an autogyro costs more than the fuel. Ram jets at blade tips are certainly not quiet. I have a couple of blades from an autogyro that show where some of the rotational energy goes when there are problems while still on the ground.

    In transport systems, conversion of stored energy is always going to be a problem. The faster you travel, the more kinetic energy you must convert when stopping. The higher you fly, the more potential energy you must convert when landing. "Engine" power is the maximum rate of energy conversion.

    Low bridges permit traffic flow to cross without risk of collision. Railways and bicycles are relatively safe, economic and quiet. Is there yet an equivalent mode of flight available?

    If motorised road vehicles cannot be operated safely by “normal” people, then what hope can there be for flying machines?
  14. Jan 20, 2015 #13
    These are all great posts. Allow me to respond to each of these posts.

    The ultralight idea is a very good concept. If it could be enhanced with vertical take-off, and folding/collapsible wings for parking and storage its not a bad way to go. How would you propose to resolve this?

    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.

    I like JetMan. But he can't take off or land under his own power, the two biggest hurdles to overcome. How would you propose to resolve this?

    Mechanical flapping wings are an amazing thing to think about, How would you implement this? Is wing span alone impractical for taking off in congested areas like a driveway?

    Can you elaborate or provide a sketch of what you are envisioning? I think I have it, but I would like clarification.

    That is a great find. Thank you for the link. I would imagine that vertical takeoff method is "single-use only" then the ramjets must be replaced. Can you think of a way to make it a maintenance free and repeatable?

    You have raised several questions about noise, energy and transportation infrastructure. I agree noise is a concern for residential areas. Energy and infrastructure have been talked about a little bit in the threads above, Do you have any proposals for resolving them as well?

    To all I will say:
    Bad weather is a real hindrance, I totally agree. It would take considerable technology combined with an abundance of power to make bad weather travel easy. I would propose a computer stabilization method using airspeed sensors on all sides mated with fine-trim thrust devices, all operating in a rather seamless fashion to the average user. Not impossible. but very tricky.
  15. Jan 20, 2015 #14
    The ram jet gyro as I recall just burns the fuel the gyro uses, (all be it lots of it)
    The weighted rotor has power clutched from the pusher engine.
    both are repeatable, the weighted rotor just requires spin up time.
  16. Jan 20, 2015 #15


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    albeit :)
  17. Jan 20, 2015 #16
    I think there are more important non-technical considerations.

    If your car runs out of gas, you just come to a stop and you are only at risk if you are in very heavy, fast-moving traffic. If a plane, even a small one, runs out of fuel, you can still control your descent and glide to a safe enough landing. A helicopter goes into auto-rotation if it loses power and the pilot can still control the descent safely enough for a non-lethal landing. If a jet-pack runs out of fuel, you plummet to your death, unless you're at a high enough altitude to feasibly deploy a parachute.

    So any failure of the jet pack will likely result in death or at least possibly severe injury for any useful speed or altitude.

    Then there is the nature of how people will control their jet packs. Unlike on the ground, in the air there are no brakes. Unless you can turn fast enough without stalling, you have no way to avoid a collision. Jet packs have no lift so a very quick turn may kill enough forward momentum to cause you to fall unless you can accelerate fast enough in the new direction.

    So I don't think we'll be seeing exotic solutions like jet packs or rocket pods.

    Ultra-light fixed-"wing" aircraft I think would be the solution for personal flight. If memory serves there are ultra-lights that cost not much more than cheap cars. However, they still need a take-off and landing strip or at least enough open space, which might make using them for your morning commute a little difficult, unless a VTOL ultra-light is invented. They're rather limited in range and I think there are some rather stiff legal restrictions regarding their use, but I think that's our solution.
  18. Jan 20, 2015 #17


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    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.
  19. Jan 21, 2015 #18
    It seems like a good portion of this thread is focusing on "fixed wing" or not. Yes, a fixed wing craft can glide to the ground with some hope of survival. Add a parachute to a non-fixed wing craft, and I feel it has an equally if not higher rate of survival. Does everyone agree with me?

    Fixed wing craft typically do not VTOL which I feel is a huge part in making personal flight practical. Does everyone agree with that?

    Parking / Storage is another issue all together. folding wings could be a solution, but true fixed wings just won't cut it. Agree?

    If all agree, do we take fixed wing craft off the table then as a solution for practical personal flight?
  20. Jan 21, 2015 #19


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    If only things were that simple. If “fixed wing” is the enemy then you must define “fixed wing” before targetting "fixed wings" and making them the scape goat for all other failures. The human need for a common enemy leads to racism and genocide.

    No. For some reason parachutes are not widely used on helicopters. Gliders are still safer than parachutes.

    No. Crows cannot take off vertically, they use a hop, a skip and a jump. Why are we different?

    No. Storage is not a deciding factor. Some aircraft on aircraft carriers are fixed wing, some are folding wing and some are helicopters.

    No. We will evolve a practical technique by keeping our options open. Birds are a good example of that. Eliminating fixed wing eliminates the quietest, safest and most efficient options yet found. Fixed wings are necessary as the migration path to better solutions.
    Last edited: Jan 21, 2015
  21. Jan 21, 2015 #20
    I do not consider birds to be fixed wing. They are folding wing and flapping wing. better for both storage and VTOL.
    My definition of fixed wing is just that. A fixed inflexible unchanging wingspan.
  22. Jan 21, 2015 #21


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    There are fixed wing VTOL aircraft. It is irrational to eliminate “fixed wing” because you feel a need for VTOL.

    VTOL is inefficient and wastes energy. It is irrational to require VTOL for practical human flight when the most intelligent birds, namely Crows, do not require VTOL.
  23. Jan 21, 2015 #22
    OK, I will not make it a requirement, rather I will post the question which in my mind that makes it a requirement and ask you to provide a different solution.

    Here is my idea of a "practical personal flight" day.
    How would you propose on a nice sunny day, 5,000 people lift off from their suburb homes, head to work downtown, land and park their personal flight craft .. all during the 8am and 9am rush hour? There simply isn't enough time to queue them all up on a runway. If they cound vertical land on the tops of buildings, parking garages, grassy picnic areas, etc. It seems more feasible in my mind. What do you envision?

    Also I will continue to point out that the crow can fold its wings once on the ground. It makes a smaller personal space for the bird. This makes it easier for the bird to maneuver on the ground and protects its wings from damage. I would strongly support a design that at least folds up the wings for these reasons.
  24. Jan 21, 2015 #23


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    I would not duplicate a transport network. I suggest that the mode of transport used on a nice sunny day be the same as used on a nasty, wet and windy day. Ride a bicycle to the train station. Use your “personal flight craft” as an expensive hobby in your free time, until it ceases to be a novelty.

    When safer aircraft with more efficient low speed propellers or flapping wings become available the game will have changed.
  25. Jan 21, 2015 #24
    any public personal flight would pretty much need to be a big old balloon type flyer. with enough impact resistance to protect objects the flyer is run into otherwise its a pipe dream to expect any government to approve general public use. saving the pilot would be secondary compared to protecting peoples houses buildings people in general and the clincher all government facilities and personnel. there is no more paranoid group about their own safety than politicians the amount of bunkers/no fly zones concrete barriers specifically to protect them should be evidence enough to see where they will go with legislation of personal flyers if they became mass producible and cheap enough for general use.
  26. Jan 22, 2015 #25
    So that's it, huh guys? Why even try to build "the game changer" that becomes mass producible and cheap enough for general use? Let's just kill the idea before it even starts. Not really the feedback I was hoping for. Nothing exciting or new or great will ever happen if you only focus on the reasons NOT to do things. The next time someone asks me a question I'm just going to say, "Why bother having a discussion! The only thing that could possibly come from it is communication, information, understanding and progress!! We can't have any of that progress stuff happening in this country! The government and politicians won't stand for it! Status quo! That is what our country was founded on! Yeah!" *mic drop*
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