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I am imagining a para-glider shaped balloon. Hot air balloon scale, of course.
So two baskets, two burners with their associated vents and one lightweight arcing framework linking baskets (Can be inside the balloon, but more complex). Think two standard balloons leaning towards each in a kiss.
The
balloon would have sewn structures, heat resistive strapping, to modify the balloon into a more an aerofoil shape. Control lines could be incorporated to have some collapse-able sections. This, with the advantage of venting, could allow for a shape changing hot air balloon wing.
So with a bit of Bernoulli's magic, the heat of burners and the pilots' skill, the balloon can have a new found freedom.
Jetairship
Jetairship
[theircompetitor, Nov 24 2017]
Inverting paper torus
https://www.youtube...watch?v=G27dNeUjKWk
I made one from granite once just to see if I could. [2 fries shy of a happy meal, Nov 27 2017, last modified Dec 03 2017]
21Q, where are you?
http://www.halfbakery.com/user/21_20Quest
[normzone, Dec 03 2017]
Phoenix airship
https://newatlas.co...vehicle-fish/59434/
They're stealing our ideas again... [neutrinos_shadow, May 14 2019]
Wikipedia: Underwater glider
https://en.wikipedi...i/Underwater_glider
The actual inspiration for the above? Works the same way, just underwater [notexactly, May 22 2019]
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... to go wherever the wind blows it. |
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Without propulsion and control surfaces (apart from the envelope "wing-warping") it's still a free balloon, not a dirigible. |
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With a wing shape it's going to have a glide path. |
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To have a glide path, you need net weight. If you have a neutrally-bouyant balloon with no propulsion, it will just sit there in its own block of air, and go wherever the wind blows. |
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A venting balloon is going to fall with the direction of the wind. A wing shaped balloon falling is going to have another force vector. The two venting holes and section collapses will be able to twist the balloon in the wind. |
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Are you suggesting that you vent some of the gas to reshape
the wing/balloon, go some direction you couldn't go with a
regular balloon then refilling the envelope? If you're talking
about emptying different sections of the balloon to somewhat
direct its fall I suppose you could have your plummeting
balloon move a bit to the left or right a couple of times before
it emptied of gas then turned into a paraglider wing. Maybe
I'm not clear what the goal it here. |
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The goal with most forms of aviation is to eventually resume
contact with terra firma in a way that does not cause an
unacceptable level of damage to the participant(s). |
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The goal is to use the aerofoil shape to give some directional control. The wing shape would alter flight characteristics of a ascending and descending hot air balloon. Collapsing/Sqeezing balloon sections as well as venting would change direction orientation. |
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An initial prototype would be enlarged paraglider with two pilots, poled out at either ends of the paragliding chute. |
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//Collapsing/Sqeezing balloon sections as well as venting
would change direction orientation.// |
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You might be able to change orientation but not
direction of movement. When you're lighter than air you're
either hovering or moving up. The shape of the envelope
might determine orientation but would have no effect on
direction of movement which would just be with the
prevailing wind. Think weather vane. |
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When you're heavier than air you can begin to act like a
glider, changing the configuration of your wing to change
direction but then you're a glider. |
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Put it this way. Take an airplane and attach a massive
inflatable hydrogen balloon to it. When it's flying it has
total control of wherever it's going but when you inflate
that balloon, it doesn't matter how the control surfaces are
oriented, assuming the engines of the plane are off, that
vehicle is a balloon and that balloon is going wherever the
wind is blowing. |
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As for the shape of the balloon, it could be Mickey Mouse
from the Macy's Thanksgiving Day Parade or a series of fully
manipulable flaps and ailerons, it's still substantially going
the direction the wind is blowing. |
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So without adding any force for that control surface to fight
against the wind with such as gravity (falling like in
steerable parachute) or an engine (as in a paraglider) you're
substantially at the mercy of the breeze. You might be able
to get a little movement but not much. |
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Also keep in mind, any reshaping of that lighter than air
envelope is just
going to get that aforementioned wind vane effect. It will
just turn into the orientation that puts the half of the ship
with the most resistance down wind. An aileron leverages
forward movement against oncoming air to change the
attitude of the plane. With a balloon you have no such
leverage. It would just turn until it hit the shape of least
resistance and then continue to float in the direction the
breeze is going. |
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Since it's a hybrid, and thermals are the bread and butter of a paraglider, I am thinking more paraglider flight dynamics than hot air dynamics. Which is what is wanted anyway. |
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Paragliders rely on aerodynamic lift, not buoyancy. They trade
height for forward velocity, which generates lift. A moving (rising)
mass like a thermal provides upward motion at a rate higher
than the glideslope loss. |
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Sorry wjt, let the idea die with dignity. Time to pull
the plug on this one. |
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First thing you want to do when inventing something
is ask "What am I trying to achieve?" not "What
happens if you combine a coffee pot with a football?" |
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//"What happens if you combine a coffee pot with a football?"// Rugby. |
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// let the idea die with dignity // |
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Why ? Just bludgeon it with a rock, then throw it in a shallow unmarked grave. |
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So, here's a crucial point of the idea. How large can you scale up a paraglider? |
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I know where you're going, you're looking for a use for the
football/coffee maker. |
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Ideas are like girlfriends, sometimes you just need to move
on. This one's doing your friends, stealing your credit cards
and probably has the clap. |
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Nonsense.
I worked out how to make this viable years ago. It's one of the few ideas I never posted because I would like to build the prototype some day. |
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You just take all of the negatives everybody has mentioned, flip them all on their heads and those negatives all become positives. |
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The thing about yachting is that you can only do it two ways: |
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(a) Go completely with the wind, in which case you can have a very low drag in the water, and travel almost as fast as the wind. |
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(b) Go at an angle to the wind, in which case you need drag in the water so that the wind has something to work against. |
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With an unpowered aircraft, you basically have three options: |
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(a) Go completely with the air (ie, be a cloud) |
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(b) Trade altitude for speed relative to the air (ie, be a glider) |
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(c) Tether yourself to something and use that tether as leverage to travel at an angle to the wind (ie, be a kite). |
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[wjt] seems to want to go for option (d). |
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If it helps in thinking about any of this, just do all your thought experiments in still air and imagine the ground rushing past instead. |
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//Nonsense.
I worked out how to make this viable years ago.// |
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Well, time to build the prototype then. All I ask is that I get
to watch the videos. |
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Just remember the first law of aerodynamics: |
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"Keep your design scientifically sound,
or you'll end up a puddle of goo on the ground." |
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Orville Redenbacher, inventor of the modern airplane. |
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A gas pump & pressure tank arrangement as used in most
normal airships might be a better idea, then you don't lose
your gas & can restore lift. |
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You can then reduce lift (to below neutral buoyancy) so you
"can" glide & restore lift to
regain altitude when your thermals run out. |
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What you have then is a hybrid glider / (helium?)
balloon,
was that what you were aiming for? |
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// First thing you want to do when inventing something is ask
"What am I trying to achieve?" not "What happens if you
combine a coffee pot with a football?" // |
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Is that too long to be "marked for Tagline"? :)) |
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//Well, time to build the prototype then. All I ask is
that I get to watch the videos.// |
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It’s all about the money... and my lack there of.
Unfortunately you missed the opportunity to witness the
first lift-to-weight ratio experiment where my neighbours
got to wonder at the fifty foot black tentacle reaching over
my house and waving down the street like the coming of
Cthulhu or something. |
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Aw crap I won’t be the guy to build this thing anyway so I
might as well put in the public domain like the rest of my
brain-farts eh? |
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<stares thoughtfully into the distance> |
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Gather ‘round kids... little story time. |
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So like twenty years or so ago I was taking my private pilots
license course, I got to where I could solo and then my
instructor/buddy crashed his plane and died on a trip leaving a message on my
machine asking me to join him as copilot to get ten free
flying hours and knock about 1200 bucks off getting my
license.
It gave me the willies and I never completed
the course but it got me thinking about the safest aircraft
which could ever be made. |
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First of all, forget about lighter than air gasses and
compressors. Solar energy is all that is required. |
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Picture a black or clear parafoil but about half the size of a
football field which can be preheated to achieve vertical
take off but relies on solar energy alone to stay aloft.
the shape of the wing is important as the body of the craft fluctuates between slightly negatively buoyant and slightly positively buoyant while being able to undulate like a manta ray. |
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Once at altitude venting the heated air would cause
descent allowing for hang-glider like weight displacement
to control direction. If each of the tubes comprising the
parafoil are segmented in such a way that cold air rushing
in the front compresses the heated air through a series of
baffled chambers, decreasing in volume, creating a slight
passive solar jet then some substantial speeds might be
attained while travelling with the wind. |
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I believe that enough excess solar radiation can be
garnered while above cloud cover to power a UV light
focussed up through an aperature on the underside of the
canopy to keep the craft aloft at night. Elevation
determines wind direction. |
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First 2fries, very sorry about your friend but glad
you're ok. |
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What you're describing is sound but it's an airship.
A parafoil shaped airship makes good sense and
they've been around for a while. Here's the
problem with asking too much of your venting to
change the attitude, altitude and direction of your
craft: you're going to need motors to get the thing
moving anyway, so why not just point the ship
down to land using old fashioned control surfaces? |
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The solar heated envelope would work as well but
it's going to have to be very, very, very light so the
cost of saving a few dollars on a propane tank and
burners would be having to abandon any sort of
useful carrying capacity. |
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The solar jet thing just doesn't have the enough
going into the system to go out the other end to
provide any sustained, useful thrust at all. |
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Finally, as far a gliders go, there's a reason you
don't get on a glider at Heithrow bound for New
York. You're falling, or perhaps skiing is a better
analogy, along a slope of air looking for the next
updraft. You go where you find them and when you
don't find them, you land. |
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And also remember that you're making a deal with
everything you add to your design. Want to get rid
of that propeller? It'll cost you forward air speed.
Want to loose that weight and get lighter than air?
That will make your craft big and fat and that too
will effect how fast your craft can go. Want to
break the speed of sound? You're going to have to
drop the lighter than air feature, etc etc. |
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This is what I mean by "Get your thinking back in
the box." Sometimes the box is right. You only
think outside the box when the box is wrong. In
this case, the box says "Engine equipped lighter
than air gas filled airship beats solar powered jet
flying wing.". |
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Maybe rather than thinking outside the box we
should just try to make
the box bigger. |
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Ok, that last line sounds like the kind of crap you
hear from eastern mystics that pisses me off, but
you get the idea. |
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hmmm, the solar jetting only needs to provide enough thrust for the camber of the wing shape to generate lift. If used in stages then descent equals forward propulsion with no motor or propeller, and ascent would also have slight forward propulsion. Though you'd need to follow existing wind patterns to get any great distance this solar hot-air parafoil would be far safer than ballooning and I could see corporate sponsorship substantially lowering the cost of your rig if you were willing to say, fly your 1/2 a football-field sized Harley Davidson billboard over Daytona beach at certain times of the year... or a Coca Cola wing above Fort Lauderdale at spring break, etc. |
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I just want one.
With a secondary chute it's the safest aircraft I could dream up. Almost no moving parts. Unlimited power supply if I am right about storing enough energy to shine a UV light all night long. |
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The question I have is; if you created four of these wings designed to pull against one another in four different directions, or perhaps a continuous ring-wing with inward venting, would individually controlling the solar jetting allow a platform to remain aloft indefinitely? Perhaps almost stationary even? |
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Well, there's just not any promise in the concept of
"solar jetting". Just look at the volume of airflow
through a jet engine then compare it to the
volume
of airflow through a passive solar balloon that
takes
cold air in one end, heats it up over a period of
time
using sunlight then spits it out the other end to
provide forward movement. You might have
enough
force to bump the ship foward a few feet every
few
minutes but that's about it. |
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As far as playing around with a couple of black
garbage bags taped into various shapes just to
experiment with various solar balloon designs, no
expense to do that. Might come up with some kind
of advancement of the art with some tinkering. |
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And by the way, there's nothing wrong with making
something work that's not as efficient as existing
designs simply because it's something new. That
can be very cool. |
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How about something where the payload
moves around to make the envelope shape move in
an advantagious manner? Maybe you've got a bird
wing shaped affair where the gondola moves from
one side to the other making the heavier "wing"
drop to provide forward thrust then raise as the
gondola moves along a cable to the other side.
Just spitballing here. I don't want to come off as
the "Solar Balloon Grinch" spoiling all the fun. |
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Spitballing is cool.
I question your evaluation of the passive solar jet given that the body of the craft fluctuates between slightly negatively buoyant and slightly positively buoyant while being able to undulate like a manta ray. |
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While we're spitballing there's another way as well.
It's pretty funky though and totally relies on no wind. |
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If you were to make tetrahedrons and connect them together on hinges if creates a Flexahedron, which is basically an origami torus ring. This shape would allow a solar hot air craft to propel itself by inverting.
[link] |
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// origami torus ring // // propel itself by inverting // |
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Cool idea, would look great in action :) |
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Or just do it like a jellyfish with a large flexible / elastic sheet
or diaphragm, stretch it out toward the desired direction of
travel & release (not sure (thinking about it, as you suck air in
the back as you stretch it forward) if that would work at all
though, how do jellyfish do it?). |
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// the craft fluctuates between slightly negatively
buoyant and slightly positively buoyant while being
able to undulate like a manta ray.// |
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I get the idea, it's clever but you're short of
horsepower to get any movement. |
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You should go back and put that description at the
very beginning. It's the clearest picture of what
you're talking about. |
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There are autonomous submersibles that alternate between bouyancy and sinkancy, working like underwater gliders on both ascent and descent. |
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I was thinking some kind of corkscrew movement
might be something to consider. This is going to be
really hard to describe. |
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1- Long spring shaped envelope devided into
multiple compartments. |
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2- Visualize the top half and the bottom half. At
any one time half the compartments are at the
top, half are at the bottom. |
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3- Now visualize the bottom half being black on
the top portion to absorb heat. |
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4- Visualize the top have of the current* top
portion being reflective to reflect light and reject
heat. *(current because the thing turns, top
becoming bottom, bottom becoming top) |
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So the idea is, the bottom half gets hot, rises and
rotates the spring giving forward motion like a
propeller. Once it gets to the top, it rotates into a
configuration that rejects heat and it cools off
while the now bottom section starts to gain heat. |
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It's a really simple idea but I don't know if I've
illustrated it to any useful extent. Anyway, on a
completely windless day this might move a little
bit. |
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You might need 3 sets of compartments to get the
rotation, not sure. |
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That is a cool idea, [doc]. |
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Thanks Max. At least whether or not it would work is
up in the air. |
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Could also put this on the ground and use it to make
the world's weakest solar powered motor. |
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You could also try it underwater. |
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Conversion efficiency. PV cells are only a few percent efficient at best, yet super high altitude solar-powered drones are under consideration and may be a viable technology. |
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Now, could a solar-heated ram turbine do better ? |
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Hollow, thick-chord, low speed wing - transparent upper surface, lower interior surface coated in vantablack, and insulation below. Turbine inducts air into wing interior, which is heated by solar input. Heated air exhausts via a second turbine, shaft-coupled to the intake. Temperatures won't be high, so the blades can be fabricated from composites. |
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There will be a small amount of thrust from the exhaust air, but the main propulsion would come from a direct-driven low-speed prop geared down from the turbine shaft. |
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//You could also try it underwater// |
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Problem is, the light wouldn't get to that bottom section
you want to heat up and make raise to turn the thing.
Some kind of inverted version might make an interesting
boat though. You've got cold water to provide a greater
temperature difference. No idea how you'd do it though. |
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8, sounds like you're doing real and practical engineering
there. I'm just spending some time in the "Dr Seus School
of Wildly Impractical Contraption Design". But the enemy
of that idea is the mass of the envelopes needed to cook
all this air. Would you get enought temperature
differential to get a prop turning fast enough to move the
thing? Maybe. I'm thinking long sausage shaped thing for
minimum drag with the prop at the front might work. |
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I was also thinking of a undulating serpent in the water
thing with the alternating heating / cooling
compartments idea before the corkscrew thing but a
propeller would probably be the way to go. |
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Frankly this sounds like it would make for an interesting
competition. Fastest non-photocell sun powered aircraft
design competition. |
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The breakthrough would be somebody actually getting
something to fly because of that catch 22. The more air
movement you get, the more horsepower you get but
with more air movement comes more air, bigger
envelopes and more drag and weight. |
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I'm going to go ahead and bun this idea because I like the
conundrum. Now I want to make a flying sun powered
balloon-plane thingy just because that nagging Jiminy
Cricket of practical engineering rules in the back of my
mind is telling me it can't be done. |
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How about one big ass propeller that works like
this: |
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It's got a series of sun blocking skirts that fall open
and
allow sun to enter and heat air on the bottom
blades but
when the blades float up (turning and pushing the
thing
forward) the skirts or shades fall down and block
the sun
allowing the thing to cool, lighten and continue
turning
but this time down where the sun blockers open up
again. |
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So in the down position, sun blocking venetian
blinds fall
open, in the up position they fall shut. Kind of a
variation
of the corkscrew thing but could be several
hundred feet
tall so at the outer edge of those blades even some
slow
turning propeller could result in some pretty fast
speeds
towards the tips resulting in a reasonable forward
thrust.
To give the thing some structural stability you'd
just have
them pumped very full of air. |
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Actually, just occurred to me you don't need the
skirts.
Since it's a propeller blade that's twisted, you have
one
side absorb light, the other reflect it. Just have
the sun
hit it from the side. |
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// How about one big ass propeller that works like this // //
It's got a series of sun blocking skirts that fall open and
allow sun to enter // |
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Why not just use a solar mill (not that I think that would work
mind) ? |
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Solar mills (Crookes radiometer) operate only in near-vacuum
conditions and with ultra-low friction bearings. They don't work
at atmospheric pressure. |
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//Why not just use a solar mill, not that I think that
would work.// |
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Non-photocell... Can I use a focal mirror and a stirling
engine turbine? |
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We had one of those “Air Swimmer” toys that propelled
itself with a fish tail action. I see the big Manta Ray as one
of those turned sideways. |
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No, that would be a cetacean. |
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A ray does obtain propulsion from vertical movements, but of its
"wings". |
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Dolphins and sharks are both marine predators, one employing
up/down tail motion (causing constant pitch variation), the
other
using side-to-side motion causing variation in yaw. Clearly both
approaches are valid for the species concerned, since they
continue to exist. |
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They do not, however, require "lift", having approximate neutral
buoyancy. |
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Birds derive both lift and propulsion from their wings, usefully
gaining both from one set of muscles. If birds used tail motion
for propulsion they would need extra muscles, hence more
mass. This would be less "cost-effective", and no doubt the
forces
of evolution would have some input on such a design. |
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If birds were neutrally buoyant in air, then oscillating-tail drive
might be practical.This would mean that such a creature -
essentally a large, slow-moving bag of gas with a very small
brain* - would
need a means of generating and containing elemental hydrogen,
not a biological
impossibility. |
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This would be a fire risk, but helium would be impractical as an
alternative lift gas since, lacking grasping appendages, birds**
would be unable to operate the valves on the cylinders. |
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*very like Donald Tusk, but smarter and with more charisma, I.e.
some charisma. |
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**Some larger raptors might well have enough strength and
dexterity to work gas taps, but if using buoyant rather than
aerodynamic lift would most likely be unable to execute their
normal hunting techniques, resulting in starvation ; a classic
example of maladaption to technological change. |
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Sp. "**"
Gr. ")"
//nirmal hunting// This is now prohibited, except among those
indigenous people-groups whose totem animals find it amusing.
Ochre must be worn. |
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That's the problem with thought design , a vast gap between actual happening and the second and third design iterations. |
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May I suggest an oversized paraglider with the cells pumped with hot air, some small gas burners until scale gets exceptional, to see what the data says. Oh and the handling. |
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Well, I can give you that data right now. With the
addition of gas burners, you'd get a floating flying
wing shaped balloon. For it to be controllable
you'd need to add some way to control it. To
design this control system you'd have to ask "Where
do you want it to go?". If you want it to fly against
the wind, you need to loose the buoyancy and have
it fall or put some kind of thrust mechanism on it.
There's no 3rd option. |
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Gonna do one last quick review. First let's look at
what it's doing now. It's going
wherever the wind blows it. Put it next to the
Macy's Thanksgiving Day Parade Micky Mouse float
and let them both go, they're traveling in the
exact same direction. Each will turn into the wind
such that it will pivot on the center of pressure
such that the side that offers more resistance to
the wind will turn downwind and the side that
offers less resistance will turn upwind. To simplify,
a rocket shaped balloon will float away with the
pointy part facing into the wind that's blowing it. |
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Now with the deflating, inflating thing you're
talking about, you might change the shape and the
orientation, but to get useful movement out of it
you're going to have to start thinking about how
much energy you have to work with. When you
deflate a section between the two wings to have it
flap for instance, does it happen fast enough to
get any useful forward motion? Watch how fast a
hot air balloon takes to fill up. It's very slow. Not a
lot of promise in using the inflating and deflating
of one of those things to harness the difference
between a full and empty chamber to get some
kind of forward motion going. |
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My years of designing rockets when I was about 8
to 10 years old required me to spend many minutes
learning about thrust to weight ratios, center of
pressure, center of mass, angle of attack, control
surface design etc. I believe my entire academic
career spent on this subject took the better part
of a half hour, certainly at least 20 minutes so I
know about this stuff. Rocket scientist might not
be the right title, but I am qualified with this
extensive experience to save my fellow man from
bad aircraft design. I don't like to use the term
"hero" loosely but... well, in this case. |
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So, understanding that we're just having fun here,
this is this morning's idea to get one of these things
moving. |
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Flapping Flying Wing Balloon. |
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Have the wings set up such that there is a very
tight set of springs holding it in place in the up
position or the down position. To move from one to
the other would require a great deal of force but
not a lot of distance to be covered. |
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You have two sets of inflatable envelopes or
envelope sections, at the
tips of the wings, and at the middle of the craft. |
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To start the cycle, you have the wings in the down
position. You route your hot gas from the burners
to the wing tip envelopes and open the center
envelopes. This causes the tips to raise and the
center to fall. This wouldn't happen very fast on its
own but remember, you have those springs. As
soon as it reaches the point where the springs are
at maximum stretching, they cross over from
pullling the wings together into the down position
to pulling the wings together in the up position so
they "snap", thus giving you some useful forward
motion. You then reverse the process, empty the
wing tip bags while filling the center bags until you
"snap" into the downward position. |
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If there was absolutely no wind, like in a large
aircraft hangar or something, this thing
might be able to fly from one side to the other in a
few minutes using the "deforming of shape" thing
that I think you wanted to achieve. |
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//a rocket shaped balloon will float away with the pointy part facing into the wind that's blowing it. // |
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I don't think it will. A rocket shaped balloon moving with the wind will behave in the same way as a rocket shaped balloon in still air - the only difference is that the ground is moving past in one case and not in the other. The balloon will have no definite orientation. |
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However, if the wind is gusting, that would be different because the balloon's inertia will act as a drag when the wind speed picks up. |
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Springs are heavy though. |
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I was thinking that the pilot would be the spring.
While gliding the weight of the pilot is distributed fairly equally across the entire span of the wing. By forcing all of the weight to momentarily be suspended slightly forward of middle and slightly to either side of the longitudinal mid-section of the wing, say by standing up from a seated position, thereby transferring all weight to the feet of the pilot to just those two points, and then sitting again, a wave will be created along the entire leading edge of the craft radiating outwards towards the wing-tips, This will have a whip effect, and placing more weight on one foot or the other will bank and turn the craft as well.
Once the pilot has found a rhythm to the oscillations the thing will move a lot of air rearwards, but still won't let you fly into anything other than a slight breeze. |
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The only way to travel distances is to find an altitude where the wind is blowing your way, otherwise I see the combination of buoyancy fluctuation, solar jet, and mechanical undulations allowing one to "tack" into the wind while finding the right altitude. |
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The coolest thing about actually pulling this off will be flying it with impunity until laws have been written restricting you from doing so.
It's not a motorized aircraft.
It's not a glider.
It's not a fixed wing aircraft.
It's not a hot air balloon.
It's not a parachute. |
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It's a big'ol' snub your nose at the FAA.
The ensuing court case would generate more media hype than you could ever afford for advertising. |
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//I don't think it will. A rocket shaped balloon
moving with the wind will behave in the same way
as a rocket shaped balloon in still air - the only
difference is that the ground is moving past in one
case and not in the other. The balloon will have no
definite orientation.// |
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Might want to rethink that Max, look at a weather
vane or an arrow or rocket shaped balloon. |
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We're looking at it from the direction the wind is
coming from. The arrow, rocket or weather vane
shaped ballon is at a right angle to us currently. On
the right side from our point of view are the fins.
On the left side is the tip of the arrow, vane or
rocket. |
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Now the wind hits this object. The area of the left
hand side of the object is X, the area on the right,
the fins or feathers part is several times X in
terms of area. Both areas are subject to the same
speed of wind. The section with greatest area is
going to have more force pressing against it, since
it's catching more wind and that will rotate the
balloon so the lesser area section turns up wind. |
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Put another way, take a toy rocket or arrow and
throw it. It will orient itself according to its center
of pressure/center of mass ratio. There's no
difference between you moving the fluid (air)
against this object via wind or throwing the object
into the fluid, it will orient itself based on which
bits offer the most resistance. |
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//Springs are heavy though.// |
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I meant to say rubber bands. |
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Very light in relationship to the vehicle and able to
store lots of potential energy. |
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//look at a weather vane or an arrow or rocket shaped balloon. // Those are tethered. I assumed you were talking about an untethered, rocket-shaped balloon. If so, it will move with the same speed as the wind, and hence experiences the same forces as it would in still air. |
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However, if you meant a *tethered* rocket-shaped balloon, then all is well. |
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Well, ask yourself, what happens to an un-
teathered
toy rocket or un-teathered arrow you throw into
the
wind? In fact, go ahead and throw it tail first.
Maybe I'm not clear, but we're not talking about
anything but the orientation of the craft. All un-
teathered shapes will move with the wind, I'm just
talking about which direction they'd be pointing. |
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There actually is a kind of "tethering" taking place
because the object has mass, even though it's
lighter than air, it doesn't want to move. |
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When you hit it with wind, the part of that object
(with mass) that has the greater surface area will
collect more pressure from the wind. The area
(with mass) that has less area will collect less
pressure and it will turn accordingly. If you have an
oblong object and a weak man pushes in on the
left side and a strong man pushes it on the right
side, it will turn towards the weak man. |
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As far as your design 21, I'm not sure but I think
you're just using pilot weight to re-orient the craft
like with a hang glider. Well, ok I guess. Still
unclear on what's trying to be achieved here. |
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As to whether or not my snap wing design
would
work... ahdhunno. How could it be improved?
Throw the entire design in the garbage and get
yourself a piston engine powered dirigible. |
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Bottom line, I'm excited about entering into this
design competition, I just don't know what would
have to be achieved to win. "Balloony wingy thingy
that kind of moves around without power but is
jetty and reconfigury" is a little vague and
confusing. |
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When you throw something, it has speed *relative to* the air. That's important. |
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Likewise, if you release an object in a wind, it _initially_ has speed *relative to* the air, because its inertia means that it takes some time to accelerate up to the same speed as the air. |
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But, if you release a bouyant object (like a rocket-shaped balloon) into the wind, within a second or two it will be travelling at the same speed as the wind. At this point, there are no aerodynamic forces acting on it, and its shape will have no impact on its orientation about a horizontal axis. |
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Really, truly, this is how the world works. |
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For bonus points, tell me what happens to a balloon floating in still air if you decide to move the ground past underneath it. |
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With nature not being perfect, no wind is a uniform pressure. An object, I imagine, will orientate itself due it's shape and the changing on coming pressure variations in the wind. |
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// move the ground past underneath it//
The air closest to the ground will get nooked and be dragged along. This will cause layers of faster moving air, which is less dense, so the balloon will be sucked down? maybe. |
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Yes, as I mentioned earlier, a gusting wind will leave the
balloon momentarily slower than the surrounding air, at
which point it will experience drag orienting it. However,
when the gust finishes, the reverse applies and the
orientation will change. |
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My point was that, in a steady wind, no shape of
untethered, unpropelled balloon will orient itself in the
horizontal plane. |
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//a rocket shaped balloon will float away with
the pointy part facing into the wind that's blowing it.
// |
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False. It will start out (when you release it), pointy end
into the wind. After 1-2
seconds, it will be travelling at the same speed, and its
orientation will drift randomly. |
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Maybe I can simplify things a little. Suppose the wind is
blowing at 10mph. You've released the balloon a few
seconds ago, so it is also travelling at 10mph. The speed of
the air relative to the balloon is 10-10 = 0 mph. Now, what
forces are aligning the balloon in the horizontal plane? |
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//False. It will start out (when you release it),
pointy end into the wind.// |
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I think you meant to say "True. It will start out
(when you release it), pointy end into the wind." |
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Answer as above, if your balloon isn't tethered or propelled,
and once it has had a couple of seconds since release to be
moving at the same speed as the wind. |
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OK, we may be talking at crossed wires here. |
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If you hold the balloon by its pointy end, then yes, as long
as you hold it, it will trail like a streamer. |
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I thought you were saying that it would *keep* pointing
into the wind once you release it, which it won't - it's
orientation will wander about, effectively at random,
because there are no horizontal forces acting on it. |
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I understand what you're saying and you're correct,
but the point I was trying to make was that
changing
envelope shape (I seem to remember that was the
original idea way back there someplace) was
useless
as a method of getting this thing moving. You
release
the tether, it floats up and you change your shape
and then rotate a certain way but that's about it. |
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We're still trying to get this thing to move right? |
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I'm so vague on this design I don't even know what
I'm trying to critique. |
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Oh, well, I lost track of the whole make-it-move thing. |
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Basically, if you want to make it move, you have a few options (other than putting a propellor on it). |
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(1) Make it flap some wings
(2) Make it alternately float and sink, and ride the glideslope in both cases
(3) Make it throw some air backwards, for instance by having a wide bulge that travels backwards along the length of the balloon; or any other shape-change that throws air backwards.
(4) Variations on 1-3. |
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But what about my snap wing design? Yes? No? I think
it could make some moving movements. |
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I think in an aircraft hanger with no wind you could
get to... 1, 2 miles per hour average in little bursts. |
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Ah, OK. So, you're basically flapping, with rubber bands to accelerate part of the flap. Yes, sure, if everything's the right shape. |
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Wjt? Is this a solution that fits your design requirements?
It’s a reshapey movingish “flying” thing. |
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// when I was about 8 to 10 years old ... spend many minutes learning about thrust to weight ratios, center of pressure, center of mass, angle of attack, control surface design etc. ... better part of a half hour, certainly at least 20 minutes so I know about this stuff. // |
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// Basically, if you want to make it move, you have a few options (other than putting a propellor on it). |
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(1) Make it flap some wings
(2) Make it alternately float and sink, and ride the glideslope in both cases
(3) Make it throw some air backwards, for instance by having a wide bulge that travels backwards along the length of the balloon; or any other shape-change that throws air backwards.
(4) Variations on 1-3.// |
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(1) Check. Like a Manta ray.
(2) Check. Close flaps ascend, open flaps descend.
(3) Check. Passive solar jetting of expanding air able to be augmented with focussed heat lamp.
(4) Check. All of the above in one almost-no-moving-parts package. |
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I can build a working scale prototype by feel if the maths can be derived from a working model, and I volunteer to test pilot the man-powered contraption once it's past the initial stress-testing phase.
If any group could work all of the kinks out it's this one, we just need a financier or crowd source funding to be able to put that [Halbakery Against The Real World] category into practice. |
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Who's with me?!...
with me?!..
th me?
me?.
e?
? |
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<sound of crickets>
<tumbleweed rolls by in the distance> |
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//I volunteer to test pilot the man-powered contraption// That's a remarkable coincidence. I was about to volunteer you too. |
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I know, right?! It's perfect... |
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Wanna bet me I can't get a scale model prototype to fly? |
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Maybe if I put another 20 minutes into my aerospace
engineering studies* I can come up with some better
solutions. |
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*And I've seen the movie Apollo 13 twice. |
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//As far as your design 21, I'm not sure but I think you're just using pilot weight to re-orient the craft like with a hang glider. Well, ok I guess. Still unclear on what's trying to be achieved here. // |
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21 has not added an annotation to this idea yet. |
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Yes, but you need to remember that [21Quest] had his account hacked and many annos were lost. At that point the rest of us graciously assumed the responsibility for replacing those lost annos and links. |
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This idea would work much better if we spent our time looking for ways to improve inter-aircraft communication while looking at and voting up or commenting my ideas at (see link) |
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//Wanna bet me I can't get a scale model prototype to fly?// |
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No, because it's theoretically possible and technically reasonable. I'd put your chances at 1 in 10, depending on how much time and effort you put in. |
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I meant to type 2. Hit the 1 as well by accident. |
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Still have no idea what the goal is here. |
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/Wanna bet me I can't get a scale model prototype to fly?/ |
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//No, because it's theoretically possible and technically reasonable.// |
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Too bad. This is one I really want to see made real. Truth be told though I'm a bit relieved. I could make it work, but my time has already been stretched more than I thought possible. |
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// my time has already been stretched more than I thought
possible. // |
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That's just your own carelessness, for traveling at high relativistic
velocities in normal space - it's all clearly defined by Einstein's
theory. |
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Learn to slow down, take it easy. Don't go above 0.1 C. If you
need to cover long distances quickly, use a non-Newtonian
propulsion system with temporal distortion compensation. |
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I've tried those - rented ship, courtesy of Borg-U-Go. They're crap. You get there shortly before you've left, and then they double-charge you the rental because you're using two ships at the same time, only they don't yet have the record of your paying the first rental charge, you end up paying three times over. It's a scam - go with Rom-U-Like or Cardasshire. |
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I concede that the strongest current of energy change has the last say but await future discoveries of physical manipulation that could be used to harness energy into realistic, complex, counter intuitive flights of fancy. |
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