Extra-heavy minicopter 'Jetpack' astounds world+dog The big story on the gadget beat this week is undoubtedly the Kiwi ducted-fan "jetpack", now on show at the AirVenture expo in Wisconsin. The Martin Jetpack, decades in development by NZ garage inventor Glenn Martin, has suddenly achieved worldwide fame largely due to the fact that a New York Times scribe had a bit of a hover …
Helicopters actually have "Rotary Wings." The egg beaters on top are not a horizontal propeller. A wing produces twice as much force in lift as is created by the reaction of sending air downwards.
Lift is almost a "free" force in terms of energy cost. Whereas these "packs" work entirely on reaction thrust. A very high energy cost method indeed.
This would have been a sure bet during the dot-com boom. I could envisage companies of the period buying one in order to move from floor to floor within the newly-built corporate HQ. It's exactly the kind of thing that Ion Storm might have bought, so that they could get pizza up to the roof of their Dallas skyscraper (in through the giant skylight, like in "You Only Live Twice").
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If personal flight is the aim, wouldn't it be possible to combine whichever technology (the micro copter mentioned in this article maybe) with a small helium balloon to reduce the work it has to do.
If the mass of the machine, and say 50% of the mass of the passenger is offset by a balloon then the efficiency will increase significantly, and the danger of motor/thrust failure is ameliorated. (The balloon can be multi compartment to avoid a catastrophic puncturing event).
I know their impractical, expensive and all the rest of it.
But I want one (Of the Gen H-4's), I really do. I know I won't be allowed to fly one to work, but well, I think the fine would be worth it.
That ducted fan thing looks kind of cool, but I think the extra range of the H4 that Lewis linked too would be more fun.
My humble apologies oh revered one.
I shall contact Cessna immediately and tell them that the aircraft they made for the last 50 years can't actually fly!
The fact that their 700kg aircraft defies gravity on just 70kg of thrust is an abomination against the laws of physics and they shall be burned as heretics!
Thy blessed wisdom is a beacon to us all.
"A wing produces twice as much force in lift as is created by the reaction of sending air downwards."
Where on gods earth did you get that rubbish? 95% of a wings lift is from the Coander effect (diverting air downwards) 5% is Bernouli (low pressure lift)
In case you have never seen the Red Bull Air Race planes CAN fly upsidedown! and often stunt planes have symetrical wings so that ALL the lift is Coander and None is Bernouli. (Dont believe school Physics its all rubbish! - If it were all Bernouli flying upside down would not be possible!)
From one of these dictionary websites:
39. Aeronautics. the component of the aerodynamic force exerted by the air on an airfoil, having a direction perpendicular to the direction of motion and causing an aircraft to stay aloft.
Since the distance, that you have named s, is zero, the energy is zero. My bet is that when Mark_T talks about lift he talks about the force not the verb, and that he is fully aware that accelerating any object requires energy.
Valid point on numpties plunging from the sky. But a few counterpoints-
Bad weather, nil vis = no flying by anyone without IFR kit and skills. Not let's have a go anyway (cue slaughter) as in the case of road vehicles, but not happening at all - you can't fool yourself into thinking you can cope, as drivers do when setting out in icing or foggy conditions. If you do, you'll eliminate yourself at once.
Existing PPLs vs Joe Public driver on kicking the tyres before lighting the fires - not much in it I'd say.
Ten years heavy use of a minicopter would also see at least ten much more rigorous aviation MoTs - separate ones for engines, too. Aircraft maintenance is logged, checked etc far more comprehensively than that of cars.
Cars, trucks and buses kill people. Motorbikes kill a lot of people. Aircraft mostly don't. They are regulated and enforced to the nth degree, far more than road vehicles. Just personally, I'd relax it a little, maybe not down to the level where thousands died in aircraft accidents every year (as is now the case with the roads), but a bit.
I wouldn't be allowed to, though, because of perceived risk. Everyone is happy to walk along a two-inch-high pavement in pissing rain and/or ice, fog etc with traffic roaring past nose to tail at forty mph plus, driven largely by Joe Numpty who hasn't checked his tyre tread in months, has his ABS warning light on, his brake lights and headlights dark often enough, and who may not actually have ever passed a licencing test. Just the other day a bus driver rammed a pub down my way, partly wrecking it - a whole lot more damage than a 150-lb minicopter would do coming down on its emergency chute. Articulated trucks jacknife on the motorways all the time - do we panic? No sir.
But the moment a personal minicopter came down on its parachute and squashed someone's foot, that would be it - my relaxation of minicopter regs would be repealed that week.
People are strange.
what i've always wondered about these 'personal flying machines' is nobody seems to attend to the question of weight?
why not, somehow, attach some sort of balloon system that can reduce the weight of it all, then you will need less power to get going?
or some sort of reverse gravity system?! (ok, maybe that last one is a biiiit ahead of it's time, but you can see my thinking!)
cheers,
bill
stuff and nonsense: http://www.eupeople.net/forum
OH MY GOD !
Never in my time using El Reg comments has someone's mind numbing ignorance driven me out of a thread, but you have achieved it !
"Where on gods earth did you get that rubbish? 95% of a wings lift is from the Coander effect (diverting air downwards) 5% is Bernouli (low pressure lift)"
Where? Well since you ask, I am a fully qualified commercial pilot and flying instructor so I have taught aerodynamics. I have flown single and multi-engine aeroplanes, helicopter and glider. I also competed in national aerobatic competitions and held an FAI competition licence.
I actually have flown upside down !
Ignorance is bliss so they say. Please continue to have a truly blissful life.
I think not! The right hand of the "pilot" in that photo is in the classic "pistol grip" position of...Action Man.
Clearly a rather sub-standard mock-up.
I look forward to seeing The Register's exclusive footage of NASA's moonbase next, along with an interview with the commander, Major Matt Mason.
We've got this personal flying machine, we've also got an exoskeleton lifting and carrying machine (albeit quite recently) we've got gps and satnav and carbon-fibre structure to lighten the load! Why can't we put all this together and mass produce to reduce the cost?
The end-result should be a machine that will fly us on a pre-determined route with 'on-the-fly' error correction and look totally awesome while we're at it.
Follow the link in the article to "existing mini-copters" and continue to the end of the second page for this classic comment:
"Also in development is a more powerful version of the GEN H-4 with 15hp engines that will carry a larger pilot built more specifically for the American market. "
it's still pretty cool, at least some one's crazy enough to dream.
Though they might consider a micro gas turboshaft for lighter engine weight and better reliability. Course your fuel consumption is higher, so the trade off might not be worth it.
Still, Mr. Page, ya gotta give credit where credit is due. A typical "summer jetpack story" would be one of those guys who're just repackaging the old Bell hydrogen peroxide jobs. This thing and the H4 are at least different and kinda interesting.
besides, some day, someone might crack the design and make something awesome. Perhaps combining this ducted fan unit with that jet powered skydiving wing. Either way, there'd be no progress without *trying*.
A little stressed are we?
I do hope that you do not react to stress when in the air by shouting, taking the name of your God, or maybe someone elses God, in vain and then threatening to take your toys home.
Just for the record, lift is the result of dirrecing air downwards. It's one of those action/reaction things. Just take a look at the downwash from a large aircraft. Bernouli is very good at explaining how a venturi works but not how a 747 wing works. The Coanda (I'm surprised that as an aerodynamics instructor you did not correct the spelling) effect is present, but only in a very thin boundary layer on the upper surface of a wing. The magnitude of the effect is very small. I know that you can do a demo under the kitchen faucet with a round glass, but what you see is a demonstration of the surface tension of water.
Paris, because she knows how uplift is generated and it ain't from Bernouli sucking!
3.POWERPLANT & ACCESSORIES
>>>Teledyne Continental IO-550-N Engine
>>>310 HP@2700 RPM
Certified for 100LL& 100 Fuel
Fuel Injection System
High-Pressure Wet-Sump Oil System
Oil Cooler
Induction Air Filter
Full Flow Oil Filter
Throttle Control - Vernier
Mixture Control - Vernier
Propeller Control - Vernier
Dual Ignition System
Dual Engine Exhaust Muffler
McCauley Constant Speed, 3 Blade Metal
Propeller with Blade Heaters
Propeller Governor
Propeller Heat Module with Harness
Propeller Spinner,
Polished Electric Starter
Always good to have something to do when there is a shortfall of news.
ballistic chute...
http://www.liveleak.com/view?i=cd4_1173052556
http://www.youtube.com/watch?v=JXQKaxp6Rlk
http://www.youtube.com/watch?v=CAwET3Q9Og4
http://www.youtube.com/watch?v=OvEQdEjX3Vw
http://www.youtube.com/watch?v=mt4biNan_JA
basically a rocket gun is used to pull the parachute out
So just about any idiot can fly the thing.
It is a helicopter but has fixed pitch so don't expect any magic counter rotation if it all stops.
The 4 in the title means 4 separate engines, it will land on 2.
It looks like a nice toy.
I did some research on this a few years back; $12000 (or so) would build me a jet pack.
I am just not old enough to fly one; because that price gets you the last flight, heh.
I'm loving Steve's statment 'catastrophic puncturing event'! I'm going to have to use that in a conversation at work somehow, probably toilet related.
Balloon assistance is a great idea but i guess it would end up being far bigger than you'd think to be of any use and would then be a massive drag (literally) or maybe even block yer ducts if you hit turb. "block yer ducts", man, now i have to use that in a work conversation.
MarK_T, mr bigshot instructor, glad you weren't my instructor, instructors are supposed to educate, all you've done is show off (nothing new there then). So what is the % difference maverick?, what about flaps affecting the camber of wings, what about power to weight, those redbull edge 540's/extra 300's are so powerful i've seen them take off vertical at my local airfield, vertical = stalled no? so thrust has to be doing all the work to get the relative airflow vs chord line under 16 degrees?
I only have a basic PPL (ran out of money for more) but was always willing to learn more about flying, and always willing to listen.
Mine's the one with the empty wallet in the pocket. Oh and a hole in it coz i had a catastrophic puncturing event woo!
am deeply reassured that even the experts can't agree about how a bloody wing works. pretty hard to argue with Mark_T's power/weight ratio but as far as why the air seems to behave like a solid support - guess I'll just have to embrace my ignorance
happy I'm a water engineer where the fluid is nice and unsquishy and provided it stays in its pipes, reasonably well behaved.
"Helicopters actually have 'Rotary Wings.' The egg beaters on top are not a horizontal propeller."
I'm not particularly aeronautical, but I always thought that since propellers have an airfoil cross section, doesn't that make them rotary wings?
Be gentle with me.
Paris, 'cause everyone else in the room is smarter than me...
"Well since you ask, I am a fully qualified commercial pilot and flying instructor so I have taught aerodynamics. I have flown single and multi-engine aeroplanes, helicopter and glider. I also competed in national aerobatic competitions and held an FAI competition licence.
I actually have flown upside down !
Ignorance is bliss so they say. Please continue to have a truly blissful life."
Even when your aeroplane is upside down, it is directing air downwards (Earth's reference frame). If the lift was generated from the Bernoulli effect, the plane would fall out of the sky as the path lengths across the wing's upper and lower (pilot's reference frame) do not change. However, the Coanda effect is more dependent on the angle of attack than the shape of the wing so the plane is able to stay airborne even when upside down.
It doesn't matter how qualified you are as a pilot, you can't change the fact that wings designed purely on the Bernoulli effect don't perform in the way they are expected to according to the theory. If you don't believe me, why not ask Einstein:
"Although it is probably true that the principle of flight can be most simply explained in this [Bernoullian] way it by no means is wise to construct a wing in such a manner!"
That was after having spent some time during WWI as a consultant designing an aerofoil based on Bernoulli's principles.
Jason, so as not to be rude to you I will post just once more to answer your question.
Your logic is impeccable and you are correct. Propellers do generate lift. However the proportion of aerodynamic lift to reaction is different as it must produce thrust under any situation. A propeller has a crescent profile which twists flatter to the tip to accommodate the difference in arc distance travelled per turn.
A wing tends to be flat-bottomed to outward curved in order to maximise lift or solve other issues.
For those who actually want to learn the truth; Cut a strip of thin paper 12" by 1", hold one end to your bottom lip and blow across the top. The paper should lift up and flutter. Decide then for yourself if pressure differential lift is a strong real force or a lie like others propound.
Wiki also has a truthful though confused and misleading article on lift.
I tried arguing the Coanananada (however the hells it's spelt) effect with an aerodynamicist once. He rubbished it as the reason wings work, and gave me a long explanation why they do act7ually make planes fly.
I believe him - he works in a F1 team aero department.
And I believe the difference between propellers and wings is that propellers are required to produce maximum thrust by accelerating fluid past them at 90degs, whilst wings need to produce lift whilst going parallel with the air.
Or something like that.
"In case you have never seen the Red Bull Air Race planes CAN fly upsidedown! and often stunt planes have symetrical wings so that ALL the lift is Coander and None is Bernouli."
Have you ever heard the term "Angle of Attack"?
"Dont believe school Physics its all rubbish! - If it were all Bernouli flying upside down would not be possible!"
The Coanda effect you refer to is being used in high-lift devices in some airplanes by using a jet of air blown over the top surface of an airfoil. The Coanda effect in that case is the consequence of the Bernoulli effect, but it is not caused by the circulation of air around the wing but by the jet speading up the air in the boundary layer, increasing its speed and lowering the pressure (energising the flow).
The Coanda effect absolutely have NOTHING to do with imparting mechanical momentum on the lower surface of the wing as you seem to suggest.
I think that because you did not believe the school physics you have become slightly confused.
Away with your misguided pseudoscience!
The fact that blowing across one side of a piece of paper causes it to flutter is entirely irrelevant to your argument.
1) You are forcing air across the paper at a considerable difference in speed to the stationary air on the other side, and hence greating a larger pressure difference than for a rigid wing.
2) A piece of paper weighs a few grams.
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http://user.uni-frankfurt.de/~weltner/Flight/PHYSIC4.htm
Seems to be well written and the physics sounds valid as far as I can follow it.
What I would question though, is if the Bernoulli effect is pretty much irrelevant, then why do aerofoils have the profile that they do?
is people who look at the NYT article and then say, 'Ah, but the Gen H-4 is lighter!' Presumably while enjoying a glass of Real Ale through their beard.
Then again, my own reaction was, 'Cor wizzard! James Bond!' So I guess I'm not one to talk.
Mine's the battered old one that the wife keeps trying to throw out.
Maybe it's because the Bernouilli effect goes up with airspeed and is in effect "free" (though there is parasitic drag) which is used to increase lift and reduce AOA lift (which is a far greater drag than parasitic or air resistance) requirements.#
When flying upside down on a fixed-wing, you should take your AOA required to maintain height and compare it to the right-way-up. A smaller AOA required upright would show how Bernoulli this lift is.
Propellers don't use ANY of the Bernoulli effect to produce thrust: just AOA reaction thrust.
Now the reason why the 700kg Cessna works on 70kg of thrust is because the wing is to some extent like a glider, so its dead weight means it falls slower. Force x distance is joules (energy) and force x distance / time is watts (power) so when you fall slower you need less power to counteract it. If going 120mph is enough to stop gravity dropping you faster (terminal body on the non aerodynamic human skydiver with no parachute) then if you could get lift from going FORWARDS at 120mph and redirect its entire reaction to lift you will no longer fall DOWN.
AOA is one way but slows you down and increases the power required from the engine to maintain velocity (and hence the lift: it goes down as velocity goes down, so you need more AOA which slows you more and you need more AOA ... until you stall and fall out the sky). Aerofoil lift gets you a lot more lift per power required to maintain that velocity.
Just taken from what I do know about physics, lamellar flow and other fluid dynamics (again from physics degree) and adding what I know from PC flight sims.
Reads "right" to me.
YMMV.
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