Good for a laugh or a cry (Gravity Plane)
 

This is good for a laugh or a cry when you realize someone actually invested in it (or accepted money to do research on it).

The Gravity Plane

https://www.youtube.com/watch?v=tPbu5UeW4uk

Biggest problem I see... What use is it? The design has near nil passenger or cargo space, and using bouancy to generate lift would mean cargo mass would have to be tiny in proportion. It *may* work as a toy or a single seater but has zero commercial use

[QUOTE=inanitydefined;430 It *may* work as a toy or a single seater but has zero commercial use[/QUOTE]

"They" said the same thing about the airplane way back when. It does seem pretty far fetched but you never know, someone might be able to do something similar someday. We did go to the moon since then.:thumbup: Chumly

it is interesting, haven't done the math, but seems possible, am i missing something obvious (aside from wind drift)?

the basic question is how much energy does it take to compress the bouyancy fluid vs how much you can borrow on glide. if you arent in a hurry but still want distance made good, then maybe... using the compressed air for thrust before ascending is clever, i dont know if floating is fail safe if the compressed air leaks though. will need ground anchor if unattended

Im sure newtons laws will hold true regardless of the mode or travel. It cant be created or destroyed and you can never get more out than you put in.

Now solar or nuclear powered is another story. Nothing like a nuclear scram jet. :thumbup:

I imagine is has a very impractical top speed. And the slow climb up and descent glide down makes you wonder what purpose it would have.

Drone. Much like historical use of lighter than air craft for 150 years.

Yah probably, the energy to compress for descent is likely the same as the energy gained in climbing (minus many losses along the way). Wish I knew how to do that math.

My money is on solar impulse.

Another variation on the scam of the perpetual motion machine. Interestingly there is something similar to this currently operating in the world's oceans (google "underwater glider"), but underwater gliders don't make the claim of using no fuel. Underwater gliders use battery power to make the buoyancy changes to travel very efficiently for months through the ocean. Look up the Navy's Liberdade class underwater gliders.

Underwater gliders are pretty cool, using thermal gradients to compress/expand the working fluid. Though 1/2 knot is slow, that isn't the point. UNDERWATER GLIDERS

I guess the problem can be simplified a bit (and water is probably a better test medium)

http://ecomodder.com/forum/attachmen...1&d=1403199909

My money says the idea works... And probably well, but it's enormously impractical. And the cost of helium!

And having a rigid airframe light enough to be bouyant... I wonder how fast you'd be able to get on the dive going into a headwind...

The narrator is the same guy who makes those hack videos that don't work , and hardly anyone tries them to find out.

He says in the video , the plane(now high in sky) reaches a equilibrium and lets in *new compressed air* where is all this compressed air coming from ? They never say, not the new compressed air not the original compressed air.

Its a scam folks. That is why I placed it here. They are just trying to suck money for development of something that will never happen.

Its fun to figure out why it can't work. :)

Well I'm not talking about the narrators credentials, or the whole gravity plane either, nor the practicality of it, but the simplified problem in post 11. Assuming you recapture most of the compression energy when you release it into the balloon, and capture energy in the windmill on ascent and descent, is it feasible that the battery would "never" drain completely with the right equipment?

The whole FTTWDW debacle was eye opening enough that I don't want to dismiss it outright.

Nope. Most definitely not. But the idea of a gravity plane per se is probably workable.

With a paper thin unobtanium shell.

"If not, why not?" This is the basic premise behind the gravity plane, and a small tank made of unobtanium seems more plausible than two blimps worth...

It'd be nice if you can get it up into the mesosphere, but that aint realistic. It might be possible to take advantage of the temperature gradient of the stratosphere somehow.

One wonders... was Cloud City powered by thermal energy?

http://img2.wikia.nocookie.net/__cb2...Cloud_City.jpg

It looks like it is supported by a column of some sort, that might be cheating :) or perhaps a space elevator?

Hello P-hack,
Naturally the design could be optimized to demonstrate the viability of the idea. For instance, make the gas envelope a torus with the wind generator-propeller in the opening and the various mechanicals underslung of the gas bag.
Consider the Goodyear blimp, Spirit of Goodyear. It has a gas capacity of about 200,000 cu ft which in helium provides 14,000 lbs. of lift (at sea level etc.)
The amount of power you can get out of the wind, that's during rapid descent, is:
P = 1/2 A*d*v**3
where v is the wind speed
d is air density
and A is the swept area of the blades
For modern designs, efficiency of the actual wind power mechanism is around
45% - that is 45% of the kinetic energy in the wind can be recovered as electricity.
A regular torus 120 feet wide with a hole 30 feet wide (R=45' and r=15') has a volume of 200,000 cu ft. The hole in the center has an area of 700 sq ft
Air density is 0.0023769 slugs/cu ft (sea level, 70 degrees F, etc.) The power produced is about:
P = .45 * .832 * v**3 (efficiency times area times density times speed cubed)
Now this gets a bit scary-
If you could descend at 125 mph (183 ft/sec) that would develop 9000 hp for 54 seconds (falling 10,000 ft) Assume a compressor-expander with round trip efficiency about 80% 9000 hp now is the difference between the power needed to compress the gas and the power you get back expanding the gas. You could run a compressor at 45000 hp for .91 minutes and compress 200,000 cu ft of helium in that time (3 stage compressor 15 psi to 215 psi helium adiabatic expansion coefficient=1.67). By the way that's about 8 Tesla S batteries worth of juice. That's about 100% of your gas bag volume. Assume the torus is actually streamlined for descent, and the Cd is just about the Cd of the windmill -- .5 at 700 sq ft. The drag on the airship falling at 183 ft/sec is 14,000 lb, so the ship is at terminal velocity for free fall.
The point is that you can fall fast enough to generate the power needed to recharge the battery. You don't need to completely deflate the bag to descend, but the faster you fall the better.

The airship could be scaled up to quite huge size so the load capacity would be sufficient to carry that big compressor and battery.
-mort

Attachment 15220
I think this is a job for Wonka

Lol well I'm still scratching my head on it, so I thought getting rid of all the aerodynamic razzle dazzle and making it a plain buoyancy/regen problem might help. The first thing that jumped out was the pressure change is definitely working against compression/expansion.

For a gross approximation, I would assume 100% regen efficiency in compressor and winch and battery, and ignore energy in reeling up slack/piston friction etc, just a pv=nrt and energy available in ascent and energy lost in compressing at top and expanding at bottom (less force for the same distance), with some arbitrary ascent height, and assume the cylinder/piston is insulated and neutrally buoyant when fully compressed at the bottom.

http://ecomodder.com/forum/attachmen...1&d=1403391567

I don't think there is free energy there, but havent done the math...

How much energy can you get out of something that is only slightly more or less buoyant than the surrounding water. It's like a balloon that has a pencils worth of positive buoyancy. It'll go up pretty high into the atmosphere, but you'll get very little energy generation from it.

It'll probably go on for a very long time underwater, because you don't need much energy to rise or fall if you're straddling the line of neutral buoyancy. It would rise slowly and slowly to turn a generator. The height it ascends or descends may be large, but not a reflection on how much power it could generate. If you used more energy for more positive lift, you'd fight against the drag of water going up.

It's like the drinking birds. They'll bob up and down forever, but there just running off of the heat differential. There's waste somewhere, and eventually it'll stop.

I was ruling out all the other losses, because even if the theoretical net compression losses perfectly equal the theoretical ascent gains, then it is *mathematically* proven to be a stupid idea. (yes, slow assumed under water, ignore the drag for now too. With a direct coupling via a tether the speed doesn't really matter, just force and distance).

I'm no Archimedes though. Apparently the compressiblity of air is a factor too, a ballon will be more buoyant on the ground, but a barrel in the water isn't more buoyant at depth, just a function of displacement...
http://www.physicsforums.com/showthread.php?t=322544

There's an additional factor: generator torque. You need to keep the main body from rotating to get the most out of the wind turbine.

counter rotating windmill, idea still seems a bit wack.