Messages in AirborneWindEnergy group.                          AWES 24112 to 24162 Page 374 of 440.
Group: AirborneWindEnergy Message: 24112 From: tallakt Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24113 From: tallakt Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24114 From: benhaiemp Date: 10/30/2018
Subject: Re: Fwd: Survey before Crowdfunding // Sondage préalabl e à un fin

Group: AirborneWindEnergy Message: 24115 From: dougselsam Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24116 From: joe_f_90032 Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24117 From: joe_f_90032 Date: 10/30/2018
Subject: Re: Fwd: Survey before Crowdfunding // Sond age préalabl e à un fi

Group: AirborneWindEnergy Message: 24118 From: tallakt Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24119 From: dave santos Date: 10/30/2018
Subject: Forbes continues to ponder Makani; UMD weighs in.

Group: AirborneWindEnergy Message: 24120 From: dougselsam Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24121 From: dougselsam Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

Group: AirborneWindEnergy Message: 24122 From: Pierre BENHAIEM Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

Group: AirborneWindEnergy Message: 24123 From: Pierre BENHAIEM Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

Group: AirborneWindEnergy Message: 24124 From: Pierre BENHAIEM Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

Group: AirborneWindEnergy Message: 24125 From: dougselsam Date: 10/31/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs

Group: AirborneWindEnergy Message: 24126 From: dave santos Date: 11/2/2018
Subject: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24127 From: dougselsam Date: 11/2/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24128 From: dave santos Date: 11/2/2018
Subject: Towing Physics: Does a tow line "use power"? Is there a paradox of t

Group: AirborneWindEnergy Message: 24129 From: dave santos Date: 11/2/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24130 From: tallakt Date: 11/2/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24131 From: tallakt Date: 11/3/2018
Subject: Re: Towing Physics: Does a tow line "use power"? Is there a paradox

Group: AirborneWindEnergy Message: 24132 From: dave santos Date: 11/3/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24133 From: dave santos Date: 11/3/2018
Subject: Re: Towing Physics: Does a tow line "use power"? Is there a paradox

Group: AirborneWindEnergy Message: 24134 From: dougselsam Date: 11/3/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24135 From: dave santos Date: 11/3/2018
Subject: Review: Simplified Flight Power Formula

Group: AirborneWindEnergy Message: 24136 From: dave santos Date: 11/3/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)

Group: AirborneWindEnergy Message: 24137 From: dave santos Date: 11/3/2018
Subject: Advanced Physics of Human Flight (humor)

Group: AirborneWindEnergy Message: 24138 From: Peter Sharp Date: 11/3/2018
Subject: Re: Advanced Physics of Human Flight (humor)

Group: AirborneWindEnergy Message: 24139 From: dave santos Date: 11/3/2018
Subject: Re: Advanced Physics of Human Flight (humor)

Group: AirborneWindEnergy Message: 24140 From: dave santos Date: 11/3/2018
Subject: Twingtec Demo Video

Group: AirborneWindEnergy Message: 24141 From: dave santos Date: 11/3/2018
Subject: AWES applicable Kinetic Energy Recovery Systems (KERS) emerge in For

Group: AirborneWindEnergy Message: 24142 From: dave santos Date: 11/3/2018
Subject: most advanced pocket-sled; a peek into Chinese kite industry

Group: AirborneWindEnergy Message: 24143 From: tallakt Date: 11/4/2018
Subject: Re: AWES applicable Kinetic Energy Recovery Systems (KERS) emerge in

Group: AirborneWindEnergy Message: 24144 From: tallakt Date: 11/4/2018
Subject: Re: Twingtec Demo Video

Group: AirborneWindEnergy Message: 24146 From: benhaiemp Date: 11/4/2018
Subject: Re: Twingtec Demo Video

Group: AirborneWindEnergy Message: 24147 From: joe_f_90032 Date: 11/4/2018
Subject: Re: Twingtec Demo Video

Group: AirborneWindEnergy Message: 24148 From: benhaiemp Date: 11/4/2018
Subject: Re: Twingtec Demo Video

Group: AirborneWindEnergy Message: 24149 From: gordon_sp Date: 11/4/2018
Subject: Re: TETHERED TURBINE ORIENTATION

Group: AirborneWindEnergy Message: 24150 From: dave santos Date: 11/4/2018
Subject: Re: AWES applicable Kinetic Energy Recovery Systems (KERS) emerge in

Group: AirborneWindEnergy Message: 24151 From: dave santos Date: 11/4/2018
Subject: Re: Twingtec Demo Video

Group: AirborneWindEnergy Message: 24152 From: dave santos Date: 11/4/2018
Subject: Aerotecture Notes: More Flying City Lore; Applicability to Kite Tech

Group: AirborneWindEnergy Message: 24153 From: benhaiemp Date: 11/5/2018
Subject: Drag Power Kite with Very High Lift Coefficient

Group: AirborneWindEnergy Message: 24154 From: benhaiemp Date: 11/5/2018
Subject: Re: Drag Power Kite with Very High Lift Coefficient

Group: AirborneWindEnergy Message: 24155 From: joe_f_90032 Date: 11/8/2018
Subject: Power Control of Direct Interconnection Technique for Airborne Wind

Group: AirborneWindEnergy Message: 24156 From: dave santos Date: 11/8/2018
Subject: Re: Power Control of Direct Interconnection Technique for Airborne W

Group: AirborneWindEnergy Message: 24157 From: dave santos Date: 11/8/2018
Subject: Re: Drag Power Kite with Very High Lift Coefficient

Group: AirborneWindEnergy Message: 24158 From: dave santos Date: 11/13/2018
Subject: Minesto trial reported successful, first commercial order by Faroes

Group: AirborneWindEnergy Message: 24159 From: tallakt Date: 11/13/2018
Subject: Q about moving the AWE forum to a new platform

Group: AirborneWindEnergy Message: 24160 From: Pierre BENHAIEM Date: 11/14/2018
Subject: Re: Q about moving the AWE forum to a new platform

Group: AirborneWindEnergy Message: 24161 From: joe_f_90032 Date: 11/14/2018
Subject: Re: Q about moving the AWE forum to a new platform

Group: AirborneWindEnergy Message: 24162 From: Joe Faust Date: 11/14/2018
Subject: Re: Q about moving the AWE forum to a new platform



Group: AirborneWindEnergy Message: 24112 From: tallakt Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
Hi. This is a lot harder to explain than I initially intended, and I am adding a lot more detail than i intended in the first place. I don't think this is the place to for totally in depth, that would probably be better done in a PDF with figures and proper equations, but I hope that I got across the general idea.

What I was hoping to show, is that for any flying tethered device, you can make some simple approximations to estimate the power needed to stay afloat. If this power comes from the wind, a propeller, rockets, or any other power source doesnt matter. Its all a matter of conservation of energy. So in the case of two flying hanggliders, you just need to look at the amount of power lost along the way, then you can imagine what propulsion system could make them fly indefinitely.

I believe that for flying in a constant wind, it will not be possible to fly indefinitely without a tether or motorized power. Drag will eventually cause the system of hanggliders to move with the exact speed of the wind.

My point being - don't be to worried about how many hanggliders you have, and the total mass of the glider+human. The simple energy considerations will give you some ballpark feasability numbers.

I tried to get the drawing posted on the forum by sending it to JoeF. Hopefully the readers of this forum will be able to understand my equations then.

I did not cover any equations about the kites being powered by the wind. Like the other considerations I did, this the power generated by a kite flying in the wind will be a matter of simply multiplying the flying speed of the wing by the Lift+Drag forces in the direction of the kite motion. Using vector mathematics would be: Power is dot product of velocity vector and (sum of lift and drag forces). For the power of the wind to be positive, the apparent wind must have an angle to the velocity of the kite, so that the dot product is also positive. I wont go into more detail, but the effect is much the same as adding a motor with propeller, as we all know from experience with flying kites.
Group: AirborneWindEnergy Message: 24113 From: tallakt Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
Sorry, I missed some comments:

G is a pretty standard name for gravitational forces (at least for me). I did not realize not everyone would understand this, but it is described in the figure also. The value of the force G is mass times gravitational constant g (G = mg). (I'm sorry if I sound patronizing here, I don't mean to and just want to get the message across clearly)
Group: AirborneWindEnergy Message: 24114 From: benhaiemp Date: 10/30/2018
Subject: Re: Fwd: Survey before Crowdfunding // Sondage préalabl e à un fin
Group: AirborneWindEnergy Message: 24115 From: dougselsam Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
Tallak:
You just said:
"G is a pretty standard name for gravitational forces (at least for me). I did not realize not everyone would understand this, but it is described in the figure also. The value of the force G is mass times gravitational constant g (G = mg). (I'm sorry if I sound patronizing here, I don't mean to and just want to get the message across clearly)"

My reply is:
Google: W = mg  and you will come up with what we learn in high school physics.
Google:  G = mg and you'll come up with some gram-to-milligrams conversion.
W stands for "weight" which is the gravitational force on a mass, here on Earth.
:)
I have to confess, I'm completely confused as to what your basic message is or was.
I wonder if it could fit into a short sentence.
Anyway, mutually-tethered gliders pulling themselves skyward with at least one winch onboard was the topic, as far as I know.  Sounds like pulling yourself up by your own shoelaces, except it could actually work, in theory anyway...  The way things go in hang gliding, there would probably be a lot of accidents and people killed before they got the details worked out.  I mean, towing has been around for decades yet people still occasionally die from lockout.



---In AirborneWindEnergy@yahoogroups.com, <tallak@...
Group: AirborneWindEnergy Message: 24116 From: joe_f_90032 Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
Group: AirborneWindEnergy Message: 24117 From: joe_f_90032 Date: 10/30/2018
Subject: Re: Fwd: Survey before Crowdfunding // Sond age préalabl e à un fi

Same: 
Group: AirborneWindEnergy Message: 24118 From: tallakt Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
Let me try to make my message short, and sorry for th confusion (I never saw W = mg before, thats conpletely wrong to me ;) ):

The power necessary for endured flight may easily be estimated by the equations described. It does not matter where the power comes from. A winch between two hanggliders is a plausible option, and the winch must instill as much power into your system as what is lost in drag forces

Tallak
Group: AirborneWindEnergy Message: 24119 From: dave santos Date: 10/30/2018
Subject: Forbes continues to ponder Makani; UMD weighs in.
Introducing Prof. Williams of UMD to our notice; her opinion pasted below applies to AWE in general, not just Makani. Forbes itself is quite foggy about AWE details, but has a persistent interest in the disruptive possibilities. As AWE finally reaches true engineering validation milestones, massive investment can rapidly follow, given how much awareness has now built up.

"The kite has the potential to disrupt the wind segment of the energy sector, according to Ellen Williams, a University of Maryland professor who served as director of U.S. Department of Energy's Advanced Research Projects Agency-Energy from 2014 to 2017."

https://www.forbes.com/sites/jeffmcmahon/2018/10/29/can-googles-energy-kite-rise-above-the-wind-farms/#2884add96b5b
Group: AirborneWindEnergy Message: 24120 From: dougselsam Date: 10/30/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
Tallak said:
"Let me try to make my message short, and sorry for th confusion (I never saw W = mg before, thats conpletely wrong to me ;) ):"

My reply:
Maybe this page for high-school kids, from NASA, where capital G is used interchangeably with small g, will help:

If not:
"This page is intended for college, high school, or middle school students. For younger students, a simpler explanation of the information on this page is available on the Kids Page."

Anyone who has never seen W=mg, or does not understand it, well, I don't know what to say.  Only so much I can do from my chair...
Group: AirborneWindEnergy Message: 24121 From: dougselsam Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.
We humans love to drink our own Kool-Aid.
"Google's Makani Energy Kite is reportedly nearing take off,"
(as usual.)  Everything about this news cycle sounds like a DejaVu, hiring, HR people, etc.
Reminds me of the old joke about nuclear fusion:  "About a decade away, and it always will be."
Or a similar joke I heard about India on the Bloomberg: "India looks very promising, and in another decade, will still look very promising."  I guess there is some history there or something...

""And so what curve will this new technology follow?" Williams asked before that news broke. "Will it develop new niche markets that just happen to fit in places where standard wind can't play, or is it actually going to turn out that it's so economical and so much better than wind that it's going to drive down and become competitive? We still don't know the answer to that question."

A trick question.  She didn't mention a third possibility, the usual result for "improved" wind energy devices: "Will it not find a use at all?"

I guess it could eventually end up being the next big thing, but what I saw looked a bit cantankerous.
Still wondering why these types always promise to power hundreds or thousand of homes before they can even power one home.  Why?  It's part of the syndrome that has been part of wind energy for as long as I've been involved.  Like government itself, the worse it performs, the more the problem must be it's just not big enough yet!  The old: "they won't take us seriously unless we demo at utility-scale".  Maybe it just needs to get to the jet stream.  Or somewhere way up there.  I suppose that really could be the answer.  Except those winds are too fast - the propellers would have to be supersonic.



---In AirborneWindEnergy@yahoogroups.com, <santos137@...
"The kite has the potential to disrupt the wind segment of the energy sector, according to Ellen Williams, a University of Maryland professor who served as director of U.S. Department of Energy's Advanced Research Projects Agency-Energy from 2014 to 2017."

https://www.forbes.com/sites/jeffmcmahon/2018/10/29/can-googles-energy-kite-rise-above-the-wind-farms/#2884add96b5b
Group: AirborneWindEnergy Message: 24122 From: Pierre BENHAIEM Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

Makani'M600 circular path being assumed to be 135 m radius (please see on http://www.energykitesystems.net/FAA/FAAfromMakani.pdf ) leads to a 57226 m² area before cosine correction. A conventional HAWT with a 50 m diameter rotor sweeping 1962 m² can deliver 600 kW like the M600. And the M600 sweeps about 15 times the usefull swept area due to flight requirement. 15 M600 would be needed to optimize a 135 m radius area.

In the video https://www.youtube.com/watch?v=CKFlMDUHtLg&t=710s , in the 6th minute, one can see that 30 secondes are required for a complete loop, leading to about 28 m/s wing speed if the radius is 135 m. It is a low value, perhaps due to a low wind.

 

PierreB

 

 

 

 
Group: AirborneWindEnergy Message: 24123 From: Pierre BENHAIEM Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

Direct link for the video: https://www.youtube.com/watch?v=CKFlMDUHtLg&t=710s.

 

PierreB

 

 

 

 
Group: AirborneWindEnergy Message: 24124 From: Pierre BENHAIEM Date: 10/30/2018
Subject: Re: Forbes continues to ponder Makani; UMD weighs in.

In 16th minute of the video (https://www.youtube.com/watch?v=CKFlMDUHtLg&t=710s), the flight looks to be faster: 25 secondes for a loop, so 34 m/s wind speed.

 

PierreB

 

 

 

 
Group: AirborneWindEnergy Message: 24125 From: dougselsam Date: 10/31/2018
Subject: Re: Winch-powered Flight of Tethered Wing Pairs
I should have looked closer, and remembered college physics:

Capital G is the gravitational constant, whereas small g is the resulting acceleration (on a planet of a given mass, at a given radius = 9.81 m/s/s on Earth's surface.)
Sorry about that.
Looks to me like they make their explanations for kids a little more complicated than necessary - oh well, nerds, ya know...
Either way,  W = m g  (weight = mass x acceleration of gravity)  is about as basic as science gets, even at a high school level.
Group: AirborneWindEnergy Message: 24126 From: dave santos Date: 11/2/2018
Subject: W = m * g (NASA syntax) v. W= mg (DougS syntax)
Its best to create a new topic when an off-topic question drags out.

In the case of W = mg v W = m * g (as NASA better put it, the intended multiplication operation made clear), but Doug's starting use of W = mg may have seemed to invoke milligrams (mg) somehow intended as a unit-of-weight. There is also the issue of varied mathematical expression of equivalent math, which is why engineering-science papers carefully define terms in normal practice.

Whatever the source of mg confusion was, the winch-tow topic was not the correct place to draw it out. This is the place.
Group: AirborneWindEnergy Message: 24127 From: dougselsam Date: 11/2/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)
daveS in quotes: "Its best to create a new topic when an off-topic question drags out."
My reply: * I'm trying to keep things ON topic AND factual in the continuing discussion.  Not my fault if it "drags out". 

daveS in quotes: "In the case of W = mg v W = m * g (as NASA better put it, the intended multiplication operation made clear), but Doug's starting use of W = mg may have seemed to invoke milligrams (mg) somehow intended as a unit-of-weight. There is also the issue of varied mathematical expression of equivalent math, which is why engineering-science papers carefully define terms in normal practice."
My reply: * The actual topic is: Tallek defined mg, or m x g, or m * g (all 3 equivalent) as G, rather than W (weight).
Further, when I pointed out what we learn in high school, the simple equation W = mg (or m * g, or m x g), Tallek stated that he did not believe W = mg, and that there was something wrong with that.

So I took a moment to google W = mg, coming up with the NASA page for high school kids that explained W = mg I(or W = m * g or W = m x g, with all 3 being equivalent)
.
BUT I did not read the NASA page carefully the first time, I merely skimmed it, seeing big G and little g, and erroneously stated that NASA had used g and G interchangeably.

My next post apologized for not reading the NASA page more carefully because I had not noticed that the NASA site had actually gone so far as to introduce G, the gravitational constant (Tallek had previously used G to mean "weight - perhaps without even realizing it, saying G = mg, whereas we learn in high school W = mg)  Tallek then replied that he didn't believe W = mg, after previously giving us his assurance he understood the topic.  So, as usual, I was kindly providing a single, simple, well-known fact, to which some are "allergic", and to which Tallek has yet to reply.

daveS in quotes: "Whatever the source of mg confusion was, the winch-tow topic was not the correct place to draw it out. This is the place."
My Reply:  The source of the original confusion was Tallek saying G = mg.   The source of YOUR confusion is you didn't read the thread carefully enough to even understand what it was about.  Syntax of mg, m x g, or m * g, was not the issue.  The typical grasping-at-straws hope for relevance by accusing others of being "off-topic" is familiar, but still... not relevant.  You haven't understood the issue.  How to denote multiplication of two variables, whether placing them together, using an x, or using a *, was not something anyone was confused about til you entered the fray.  Personally, I pointed out, as usual, a simple high-school-level fact, apologized for initially misinterpreting the NASA explanation that went a bit further than I had expected, and I now have nothing else to say on this detail of the topic, which is still the topic, whether you ever understood the topic or not, which, apparently you did not.  When you find yourself in a hole, stop digging.
Group: AirborneWindEnergy Message: 24128 From: dave santos Date: 11/2/2018
Subject: Towing Physics: Does a tow line "use power"? Is there a paradox of t
DougS wrote: "The line TRANSMITS power, it doesn't USE power. Power in at one end = power out at the other end."

In fact, a rope-drive line must "use power" to do work, under classical thermodynamics, to charge its zero-point energy. Before a slack line can transmit any power it must first be tensioned, and this zero-point energy elastically stored in the working line is given up when the line is slacked.


DougS also wrote: "In the reference frame of the tether, it is not even moving. One person here has discussed this in the case of a boat towing another boat, calling it a "paradox" that the line itself doesn't heat up. Whew - off the rails, sorry."

Galilean Relativity, that Doug invokes in noting a line reference-frame, itself began as a "paradox" to resolve, of apparent motion. Galilean Relativity does bear on the engineering and scientific paradox of lossless transmission of high power by a ship tow-rope, especially when compared to lossy electrical transmission, and the best explanation involves both basic and advanced physics. In the AWE flygen/groundgen trade-analysis, not only is the tow rope lighter by power-to-mass potential, but it does not heat up significantly with power-dissipation, which takes cool phonon physics to best explain.
Group: AirborneWindEnergy Message: 24129 From: dave santos Date: 11/2/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)
Doug, j

Just keep trying to stay on topic, even if you think its others who send you helplessly off-topic. That means forming new topics as needed. Senior members of the AWES Forum are able to do this better than new members.

NASA's m * g syntax, which you helpfully linked to, would have been less likely to create off-topic confusion in the first place. Tallak's justified request for syntax disambiguation could have been answered more generously, including starting a separate topic, had you wished.

daveS
Group: AirborneWindEnergy Message: 24130 From: tallakt Date: 11/2/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)
Hi.

First, compounding to the problems here is the fact that oftentimes I am unable to reply to messages on the forum. So if I am very quiet about this, it will not be due to lacknof will/interest.

I think we should leave out topics about my physics skill level and also which letters to use to represent weight force.

To be clear, G=mg, W=mg, W= m * g or even F=ma make no difference to me, but as long as we are discussing my inputs to the discussion of power loss keeping hanggliders afloat, I se no reason to use anything else than the original G=mg. The reason W=mg is alien to me is probably that we always reserved W for work energy in my education, and w has little relation to the work «vekt» which is weight in norwegian.

Furthermore I dont care much which units you choose to represent values, but I will not be interested in finding the missing factor to convert eg feet/mph/mph into accelleration. The discussion of meteoc vs imperial is a discussion that I have little interest in (like most europeans i suspect). I regret niw having commented about this in the first place, as it is not on topic.
Group: AirborneWindEnergy Message: 24131 From: tallakt Date: 11/3/2018
Subject: Re: Towing Physics: Does a tow line "use power"? Is there a paradox
The «fact» that tension of a tether is constant is in fact an approximation that is not toally valid when there are forces (drag) that are applied to the tether directly on the tether. This will be the case whenever there is curvature on the tether, which is easily observed. I think a better way to approach this is to say that there mist be a balance of forces at either end of the tether and any forces acting because of drag, weight or moment of inertia (probably neglible)

Tallak
Group: AirborneWindEnergy Message: 24132 From: dave santos Date: 11/3/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)
Most of us are used to figuring out the various symbols used in various technical domains without thinking twice.

Aviation usage v. physics usage once again is relevant here, since in aviation "Weight", with its implicit Earth G value, traditionally stands for what is called "Mass" in physics, and similarly aviation's "Power" (Horsepower) stands for physics' "Work" (Watts). Doug tends to presume any such semantic confusion is the fault of his questioner rather than ordinary symbol ambiguity for him to better define.

Yes W=mg is acceptable syntax here, if properly defined. NASA used W on its kid page, since aviation is its domain and the question was aviation-based. Physicists are as welcome here as aviation experts are, but they both use different terms for historical reasons. Newcomers to this Forum deserve extra regard, especially since we ourselves have invented and defined usages in AWES engineering that just need to be shared.
Group: AirborneWindEnergy Message: 24133 From: dave santos Date: 11/3/2018
Subject: Re: Towing Physics: Does a tow line "use power"? Is there a paradox
Tallak,

Yes, there are varied complex ways that a kiteline does store and return power to the system, and this storage effect is generally helpful to buffer ordinary gustiness and potentially destructive surge-force.

Its quite interesting to us that a constant balance-of-forces on either end of a kite line is only a quasi-static approximation; that definitely does not hold in dynamic conditions. If the kiteline is understood as a chain of spring-masses in a chaotic regime (ie. turbulence), then instantaneous forces anywhere on the line can vary wildly. We have even come to see the air as a coupled spring-mass medium to the line, which itself acts like a wing everywhere along its length; so its quite complex to model everything actually happening.

I have experienced emergent shock waves travelling on a thick UHMWPE kite-line in hurricane force winds, that caused anomalous line-failure at the fixed anchor-point that no static balanced-force approximation would predict. This is a very open area of research, involving sonic relativity, with the speed-of-sound along the line varying from zero to multiple kmsec in milliseconds. No one has modelled such exotic sonic relativity, as far I can tell from surveying the literature; yet such effects must occur in musical strings, which have been studied since Pythagoras, but still hold mysteries,

daveS
Group: AirborneWindEnergy Message: 24134 From: dougselsam Date: 11/3/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)
daveS said
"Most of us are used to figuring out the various symbols used in various technical domains without thinking twice."
*** dougS reply: which is why I had asked about Tallek saying G = mg.

daveS continues: "Aviation usage v. physics usage once again is relevant here, since in aviation "Weight", with its implicit Earth G value, traditionally stands for what is called "Mass" in physics,"
*** dougS reply: There is no "implicit Earth G value" since G is the gravitational CONSTANT.  It is  universal constant.  From Wikipedia: "In SI units its value is approximately 6.674×10−11 N·kg–2·m2."
The g we're concerned with here is NOT G, it is g = 9.81 m/s/s.

daveS further states: "and similarly aviation's "Power" (Horsepower) stands for physics' "Work" (Watts).
***dougS reply: No, power does NOT equal work in physics.  Energy E = work in physics.  Work is NOT measured in Watts.  Power is measured in Watts.   Go back to high school, then come back here and we can talk.
Again, we're back to me reciting simple high-school physics, which should not need to be explained in an engineering discussion. 

daveS goes on: "Doug tends to presume any such semantic confusion is the fault of his questioner rather than ordinary symbol ambiguity for him to better define."
***dougS replies: daveS tends to not understand or misstate simple high-school-level physics, which he clearly does not understand.  His replies to this discussion have been largely unresponsive to the actual conversation.  Meanwhile Tallek has kindly informed us of why he used G instead of W, due to conventions he is used to from Norway.  Tallek: We also sometimes use W to stand for Work, but mostly we use E = energy = work. 
Work = Energy.
daveS says (above) he thinks Power (Watts) = work.  No daveS, Power (Watts) = power, not work.
Like I said before, when you find yourself in a hole, stop digging.
Have a McDay.
Group: AirborneWindEnergy Message: 24135 From: dave santos Date: 11/3/2018
Subject: Review: Simplified Flight Power Formula
We have discussed the power required to keep a mass flying over many years and messages. The complexities of real flight prevent a concise exact formula, for example, to account for a reliably strong airframe v. a lighter too-fragile airframe, and many other odd factors, like wing-in-ground-effect. Human-Powered-Flight engineering has provided estimates of ~350W as a close-to-minimum-value, but these are not practical aircraft. ~5kW has been the effective minimum for marginal ultralight performance (ability to climb above ground-effect).

In Summary, our best formula for rough calculation has been 10W/kg, for both realism and ease of mental calculation. Therefore, a 100kg all-up assumption of an HG or PG aircraft gives 1kW as minimal power for sustained level flight. This is only a heuristic value; both ideal and real cases will vary.

DougS has in the past insisted that maintaining non-buoyant mass in flight does not inherently require power, but this was only found true for the extreme theoretic case of a wing that covers the earth like a bubble. This odd result does suggest that lowest wing-loading is the aeronautical design path of highest lift-to-mass (favoring the Single-Skin Soft-Kite wing).
Group: AirborneWindEnergy Message: 24136 From: dave santos Date: 11/3/2018
Subject: Re: W = m * g (NASA syntax) v. W= mg (DougS syntax)
Work itself needs to be defined in context, to distinguish between rate-of-work (W) and quantity-of-work (Whr). Rate-of-work as my intended meaning, which should not be confused with quantity-of-work.

This is not an issue of anyone's high school physics.
Group: AirborneWindEnergy Message: 24137 From: dave santos Date: 11/3/2018
Subject: Advanced Physics of Human Flight (humor)
An enjoyable mix of absurd and profound flight physics-

www.physicsforums.com/threads/is-human-flight-possible.241320/

Conclusion from AWE R&D trenches: Flying a toy kite is akin to Superman flight.
Group: AirborneWindEnergy Message: 24138 From: Peter Sharp Date: 11/3/2018
Subject: Re: Advanced Physics of Human Flight (humor)
Attachments :

    Hi Dave,

    The physics forum question was about whether it was possible to fly like Superman without flapping your arms and/or legs. The answer to the question is yes, as long as you are willing to do it underwater and fly a lot slower than Superman. Superman sometimes flies underwater. How he breathes remains a mystery.

    By changing your buoyancy (using a weighted container of air that can you can compress it or let it expand), you can glide up and down to propel yourself forward. There are seagoing drones that travel great distances by changing their buoyancy (by pumping out water) so as to monitor sea conditions. Submarines can do it, but they usually add propeller propulsion while doing it since they tend to be in a hurry.

    A long time ago (1990’s) I proposed a winged dirigible in air that could propel itself similarly using internal bladders of helium, and pumps to compress the helium into pressure tanks. I think the concept was patented by somebody a few years ago. But I assume lots of people have had the same idea, so the patent must be about only a specific way to do it.

    Gliding forward, both up and down, underwater has been done by most people in swimming pools, and that might be the origin of those dreams about flying like Superman in air. Or it might be that when you are asleep you lose the sensation of your weight. I’ve had such dreams, and they seem quite convincing. During some of those dreams I’ve tried to figure out the principle I’m using. But no luck so far. I intend to keep trying though. I should ask a Freudian analyst about such dreams because those guys can explain anything.

    PeterS

     

    From: AirborneWindEnergy@yahoogroups.com [mailto:AirborneWindEnergy@yahoogroups.com]
    Sent: Saturday, November 03, 2018 10:40 AM
    To: yahoogroups <airbornewindenergy@yahoogroups.com

    Group: AirborneWindEnergy Message: 24139 From: dave santos Date: 11/3/2018
    Subject: Re: Advanced Physics of Human Flight (humor)
    Hi Peter,

    You seem to be suggesting Superman can vary his mass, including to negative mass, as a sort of antigravity buoyancy. On the other hand, he can swoop down faster than Lois Lane can fall, so that can't be the whole secret. I liked the theory of flying as a property of a physical consciousness field, in dreams, by drugs, or imaginable-on-demand by an adept.

    While we are at it, perhaps Superman flies by invisible tethers, much like Peter Pan by stage-craft. So perhaps Superman flies as a kite in a multi-dimensional dark-energy manifold. That neatly explains why kryptonite is so toxic,

    daveS
    Group: AirborneWindEnergy Message: 24140 From: dave santos Date: 11/3/2018
    Subject: Twingtec Demo Video
    Congratulations to the Twingtec team for a nice AWES demo using multi-copter launch-assist. While there is a definite scaling barrier to E-VTOL, it works at small scale, and the launch assist props in gen mode could recharge the avionics (esp. the actuation power demand). There is still a lot to do to integrate multicopter and glider.

    At least Twingtec has not fallen in the trap of scaling up too fast, and can make design changes in the field, almost instantly. Personally, I would scrap the multi-copter system for one small RAT, and use the moving vehicle to pay out the glider, and/or winch-tow. That would be a good operational model comparison-

    https://www.rts.ch/info/regions/berne/9940216-produire-de-l-electricite-grace-a-un-drone-une-idee-testee-a-chasseral.html
    Group: AirborneWindEnergy Message: 24141 From: dave santos Date: 11/3/2018
    Subject: AWES applicable Kinetic Energy Recovery Systems (KERS) emerge in For
    Regenerative Braking has over a century of motor-gen validation, mainly in train engineering. Now there is a newly-emerging COTS flywheel basis to recover braking energy: Kinetic Energy Recovery Systems (KERS), which must be hot if formula racing has adopted them.

    In AWES ME, we seek devices to smooth chaotic kinetic inputs for smooth gen power output. Car racing is an inverse motor case, of wanting to run an engine smoothly around a dynamic course of braking and acceleration. That carmakers like Honda are developing consumer versions means these units will be standard, reliable, and affordable for AWES use. While we were still waiting for cheap supercapacitors, cheap flywheel-mass may be winning the energy buffer race. KERS could also be an E-car solution for steady internal motoring in dynamic driving conditions.

    https://en.wikipedia.org/wiki/Kinetic_energy_recovery_system

    https://en.wikipedia.org/wiki/Regenerative_brake
    Group: AirborneWindEnergy Message: 24142 From: dave santos Date: 11/3/2018
    Subject: most advanced pocket-sled; a peek into Chinese kite industry
    As hoped, the "pocket" or "keyring" kite continues to evolve before our eyes, Darwinistically, without aerospace engineering. They are ever cheaper (~6USD) and fly better.

    The sled kite's historic start fifty years ago, as a kite that could roll-up, as two sticks, in pocket sleds those sticks are long gone, and even vestigial plastic whiskers, are now gone; the new kites are fully sparless. Their two ram-air fabric tubes have become closed pockets, for higher pressure stiffness. Flapping rear corner area is a stabilizing feature. Various resellers offer the same best-selling kite in many graphic choices. The factory webpage shows evolutionary models bringing us closer to the designers. The new pattern of kite looks ready to scale up, to see how it flies big, with pro-quality build.

    Testing mine straight from its tiny pouch, it flew well, if not at the highest angle that more complex kites reach, and also the crude silkscreen art weighed it down some. I customized the wing with a longer main bridle and single tail on a Y-bridle. There is also a curious scaling effect where cheap cloth is not the thinnest, and too small a kite can result in poorer performance. This kite trades performance to be the tiniest it can be for its cloth weight, for lowest unit cost. Put it on 300m of fine fishing line and it will reach 200m high. That's a lot of aviation in a shirt pocket, and it could loft a smart watch camera.

    The hot competition is the SS pilot design, but with a more complex bridling. The simpler pocket kite derivative will be favored for lowest cost and simplest handling, and the SS for more demanding performance. The promising next development might be a superior hybrid of the best features of the two new kites, perhaps a new pilot-lifter standard. Some of the innovations could also migrate to power-kite and paraglider design. Its a golden age of revolutionary kite design advances.

    https://www.alibaba.com/product-detail/inflatable-pocket-sled-kite-from-the_60270158026.html
    Group: AirborneWindEnergy Message: 24143 From: tallakt Date: 11/4/2018
    Subject: Re: AWES applicable Kinetic Energy Recovery Systems (KERS) emerge in
    It is a choice between flywheels and batteries, or nothing at all, depending on; power and energy need, price, physical attributes, safety and more.

    It seems already products like Tesla’s powerwall are quite cheap and perform well in most catergories.

    The discussion KERS vs batteries vs other tech I believe really ends up being a choice comparing some of those qualities.
    Group: AirborneWindEnergy Message: 24144 From: tallakt Date: 11/4/2018
    Subject: Re: Twingtec Demo Video
    What do you mean by RAT?
    Group: AirborneWindEnergy Message: 24146 From: benhaiemp Date: 11/4/2018
    Subject: Re: Twingtec Demo Video

    Ram air turbine: https://en.wikipedia.org/wiki/Ram_air_turbine.

     

    PB



    ---In AirborneWindEnergy@yahoogroups.com, <tallak@...
    Group: AirborneWindEnergy Message: 24147 From: joe_f_90032 Date: 11/4/2018
    Subject: Re: Twingtec Demo Video
    RAT    : :      Usually on-wing "ram-air turbine."
    Group: AirborneWindEnergy Message: 24148 From: benhaiemp Date: 11/4/2018
    Subject: Re: Twingtec Demo Video
    Group: AirborneWindEnergy Message: 24149 From: gordon_sp Date: 11/4/2018
    Subject: Re: TETHERED TURBINE ORIENTATION
    Attachments :

      Hi Doug,

      In your Superturbine® patent #6616402 you propose using a cantilevered tail to orient the turbine so the axis is more vertical to aid in the lifting of the turbine. I suggest that this method is counterproductive because this turbine will generate almost zero power because of its orientation.  Increased lift should be achieved by increase the size of the lifter kite and/or changing its angle of attack.  Kites are inexpensive, have little weight and scale proportional to their area.  Turbines and shafts are more expensive, heavy and scale poorly. I suggest you use the cantilevered tail to orient the turbine in the horizontal direction to extract maximum power. See the attached PDF for more information.

      		   @@attachment@@
      Group: AirborneWindEnergy Message: 24150 From: dave santos Date: 11/4/2018
      Subject: Re: AWES applicable Kinetic Energy Recovery Systems (KERS) emerge in
      Tallak,

      Yes, we mostly disregard power smoothing in our proper focus on raw harvesting. Still, its a persistent question how to ideally or practically match energy demand to AWES output. For small grid-tied AWES plants, the electrical grid absorbs wind intermittency. Our AWES themselves absorb some elastic energy in gusts, and return energy in lulls. Altitude stores gust energy as potential energy. Pumping output can use springs, weights (incl. flywheels, etc., as buffering media. Battery/capacitor electrical storage is a top contender, but the energy/power-to-mass shortcomings of electrical storage made flywheels the surprise leader in formula racing. The big prize is to match synchronous generation to kite power, which no one has done well.

      Once again, we diligently look outside of AWE R&D for ready system solutions. Under the "test, test, test" ethos, we welcome anyone who includes a KERS experimentally, if only to properly invalidate it by trial. I would not hesitate to play with KERS, to extract whatever lesson occurs. Its worth making clear the limit to this exploration in AWE; to not try to reinvent mass-production COTS tech that is not AWES focusable. Its the pending COTS status of KERS that should most excite us, something we can get our hands on. On the theoretic side, its an open question if a colossal KERS might be the best buffer for GW-scale synchronous generation,

      daveS
      Group: AirborneWindEnergy Message: 24151 From: dave santos Date: 11/4/2018
      Subject: Re: Twingtec Demo Video
      Its also feasible that an actual rat in a running-wheel could power a small avionics system.
      Group: AirborneWindEnergy Message: 24152 From: dave santos Date: 11/4/2018
      Subject: Aerotecture Notes: More Flying City Lore; Applicability to Kite Tech
      The aerotecture concept of kite-based flying cities is inherently AWE-based; both the power to sustain massive flight and the power cities require. Flying cities are ancient ideas, from Vedic Vimanas to Ezekiel's City. We mine science fiction for clues to possible futures. Flying cities in modern sci-fi are too numerous to mention in one post, but some are too classic not to especially note, like Swift's 1726 Laputa, or Blish's 1950's Cities in Flight trilogy, or Anderson's Orion Shall Rise.

      Swift's Laputa is a hilarious Utopia-gone-wrong, a flying city that women will not return to if they get off, that attacks ordinary cities by shading or squatting on them. Blish paints a world where flying cities are so cheap and easy to produce that surface populations take-off en-masse. Anderson's Orion flying city is an elitist-domination HQ. Kite cities can embody many crazy possibilities suggested in millennia of flying city literature, and then some.

      https://en.wikipedia.org/wiki/Cities_in_Flight

      https://en.wikipedia.org/wiki/Laputa

      https://en.wikipedia.org/wiki/Orion_Shall_Rise

      We do not forget Wubbo's faith in us to create the AWE we want.
      Group: AirborneWindEnergy Message: 24153 From: benhaiemp Date: 11/5/2018
      Subject: Drag Power Kite with Very High Lift Coefficient

      This is the title of a paper published on: https://www.researchgate.net/publication/320742362_Drag_power_kite_with_very_high_lift_coefficient.

      In my opinion there are two main concerns: "High-Lift Aerodynamics" as developped on https://arc.aiaa.org/doi/10.2514/3.59830, and the biplan configuration. The results are interesting.

      PierreB
      Group: AirborneWindEnergy Message: 24154 From: benhaiemp Date: 11/5/2018
      Subject: Re: Drag Power Kite with Very High Lift Coefficient

      A video showing devices to increase the lift coefficient as suggested in the paper:https://www.youtube.com/watch?v=q_eMQvDoDWk&t=281s.


      PierreB
      Group: AirborneWindEnergy Message: 24155 From: joe_f_90032 Date: 11/8/2018
      Subject: Power Control of Direct Interconnection Technique for Airborne Wind

      How to cite: Ebrahimi Salari, M.; Coleman, J.; Toal, D. Power Control of Direct Interconnection Technique for Airborne Wind Energy Systems. Preprints 2018, 2018110158 (doi: 10.20944/preprints201811.0158.v1). 


      ==============

      Abstract

      In this paper, an offshore airborne wind energy (AWE) farm consisting of three non-reversing pumping mode AWE systems is modelled and simulated. The AWE systems employ permanent magnet synchronous generators (PMSG). A direct interconnection technique is developed and implemented for AWE systems. This method is a new approach invented for interconnecting offshore wind turbines with the least number of required offshore-based power electronic converters. The direct interconnection technique can be beneficial in improving the economy and reliability of marine airborne wind energy systems. The performance and interactions of the directly interconnected generators inside the energy farm internal power grid are investigated. The results of the study conducted in this paper, show the directly interconnected AWE systems can exhibit a poor load balance and significant reactive power exchange which must be addressed. Power control strategies for controlling the active and reactive power of the AWE farm are designed, implemented, and promising results are discussed in this paper.

      Subject Areas

      Airborne wind energy; Direct interconnection technique; Load sharing control; Active power; Reactive power exchange; Non-reversing pumping mode

      Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

      ===================================The following linked text did offer download of the PDF; I hope it works for you: 


      Power Control of Direct Interconnection Technique for Airborne Wind EnergySystems
      Group: AirborneWindEnergy Message: 24156 From: dave santos Date: 11/8/2018
      Subject: Re: Power Control of Direct Interconnection Technique for Airborne W
      Nice formal elaboration of what had always been supposed, that a multi-cell kite farm can even out large phase intermittencies of single-cell output, even in the hardest case of reeling unit-cells with long recovery phases.
      Group: AirborneWindEnergy Message: 24157 From: dave santos Date: 11/8/2018
      Subject: Re: Drag Power Kite with Very High Lift Coefficient
      Its long been known in kite physics, and other specific aeronautical contexts, that high CL beats high L/D. Key overlooked scaling parameters in this paper- power-to-weight, under square-cube scaling law, which constrains practical scaling up to the large biplane kite proposed; and scaling up heavier airframes to constant wind velocity. The real action seems to be ~1000m3 power-kites, such as SkySails and kPower propose feasible, not small rigid kiteplanes. This paper still clings to a flygen architecture. Lets hope this biplane flygen kite proposed gets built, to continue to exhaustively test out concerns (hopes) about (un)viability of the Makani-Joby concept this paper embraces.
      Group: AirborneWindEnergy Message: 24158 From: dave santos Date: 11/13/2018
      Subject: Minesto trial reported successful, first commercial order by Faroes
      Group: AirborneWindEnergy Message: 24159 From: tallakt Date: 11/13/2018
      Subject: Q about moving the AWE forum to a new platform
      The Yahoo groups platform is showing it’s age and I would like to ask a question to the maintainers of this forum:

      If a new forum was created, should (and could) we port the message archive of this forum into the other forum?

      The are are some reasons to do this, in particular to allow old messages to be included in a search.


      Tallak
      Group: AirborneWindEnergy Message: 24160 From: Pierre BENHAIEM Date: 11/14/2018
      Subject: Re: Q about moving the AWE forum to a new platform

      Hi Tallak,

       

      Dave Santos and Joe Faust founded this forum. So you could discuss it with them.

      My guess is that concerns and formats are different from limited and not specialized platforms such as https://www.researchgate.net/ or Linkedin, or even Twitter where there are some short discussions about AWE.

      This forum was established more than 10 years ago. Its long lifetime is also an indication of its success for what it makes. Recently a new AWE forum was created then closed. So creating a new AWE forum is not an easy task.

      This forum can be seen also as an intermediate platform to incite towards some more specific scientific researches and making prototypes.

       

      Pierre

       

       

       

       

       

       
      Group: AirborneWindEnergy Message: 24161 From: joe_f_90032 Date: 11/14/2018
      Subject: Re: Q about moving the AWE forum to a new platform

          You may copy any message in group AirborneWindEnergy into any space. 
      You may bring your youthful spirit into the AirborneWindEnergy forum by posting; 
      you may invite others to post there also.  
       
           I, for one, would be participating in any AWES forum that comes up. 

      The industry players have been quite hesitant to openly discuss much. The most discussion in open forum has been in AirborneWindEnergy forum. Actually, some of us consider the AirborneWindEnergy forum as yet in a toddler stage, not aged; everyone has been invited to participate, but the participation is low yet.   If you can manage to get higher participation in extant forum or new forum, great. Let us know when content shows in your new adventure. Or consider building the discussions you want in the extant forum. 

      Best, 
      JoeF
      Group: AirborneWindEnergy Message: 24162 From: Joe Faust Date: 11/14/2018
      Subject: Re: Q about moving the AWE forum to a new platform
      https://www.someawe.org/home/2018/9/10/forum
      has link to a zip file holding SomeAWE's forum posts.