New "plane on a treadmill" controversy - wind-powered faster-than-the-wind cart?

[Auggie]

From BoingBoing (and elsewhere):

http://www.boingboing.net/2008...ectly-downwind-fa.html

Seems pretty impossible to me. The input energy isn't enough, is it?

Sorry if this is a repost - didn't see anything about it in searches.

 

[Vehemence]

Oh no. Oh....no.

 

[Jack Ryan]

*space for rent*

 

[A Casual Fitz]

Yes

 

[HardcoreRobot]

obviously true

the one thing they are leaving out though is that all the tests were done going downhill

 

[DarrelSPowers]

The plane takes off.

 

[ShotgunSteven]

Originally posted by: DarrelSPowers
The plane takes off.

What if the treadmill that the plane is on is moving, while the plane is on the belt of the treadmill, which is also moving? :Q

 

[HardcoreRobot]

Originally posted by: ShotgunSteven

Originally posted by: DarrelSPowers
The plane takes off.

What if the treadmill that the plane is on is moving, while the plane is on the belt of the treadmill, which is also moving? :Q

you mean, the plane is on a single treadmill, but that treadmill is on yet another treadmill? with a twist... the lower treadmill is infinitely long?

 

[randay]

easily with some gearing and a variable pitch prop.

 

[JulesMaximus]

Ridiculously impossible.

 

[Evadman]

Oh god.

 

[So]

Saw this the other day, and I'm really not sure...

 

[Gibsons]

Originally posted by: So
Saw this the other day, and I'm really not sure...

I'm leaning towards impossible, because once it hits the same speed as the wind, it can't get energy from the wind anymore... can it?

 

[Rufus12]

If they actually got that to work we'd be flying in those things some day.

 

[So]

Originally posted by: Rufus12
If they actually got that to work we'd be flying in those things some day.

Ah-ha. Here's our answer. It is impossible.

Remember, frame of reference is irrelevant (Newton said that) so if this were possible, a plane flying through the air would be able to extract energy from the air and travel faster. Perpetual motion as it were. Obviously, this makes no sense, so I'm voting no. Not possible.

 

[destrekor]

If it is a normal concept such as using an exposed fan, then no, it'll be limited to just under wind-speed, as when it hits windspeed, the tailwind would be neutral in comparison to air resistance from the front.

However, that concept drawing of a funnel that can draw in air from whatever direction the fastest air movement is coming from, leads me to believe it could result in 'faster than wind' travel.

Using that funnel, the tail-wind would push through and drive the fan, creating forward motion. Once the forward motion resulted in enough air movement from the front, directing the funnel to the front would continue to drive the fan, and theoretically, I'd say that air movement would keep pushing the wheels faster, which results in more air movement, etc.
Am I missing something? That funnel seems to make the whole concept seem very possible, and more-so on a low-wind day with a simple push to start. Now, as soon as elevation changes occur on the driving path, I'd stop unless the elevation changes were extremely gradual. On a flat surface with no wind, and a funnel that the rider can manipulate - and not one that would be moved based on wind direction - would seem to provide the best chances of success.

 

[destrekor]

Originally posted by: So

Originally posted by: Rufus12
If they actually got that to work we'd be flying in those things some day.

Ah-ha. Here's our answer. It is impossible.

Remember, frame of reference is irrelevant (Newton said that) so if this were possible, a plane flying through the air would be able to extract energy from the air and travel faster. Perpetual motion as it were. Obviously, this makes no sense, so I'm voting no. Not possible.

In practice it occurs to a limited extend. Turbo-jets work in that very way: it'll only go so fast, but as the speed increases, the pressure forces more air into the jet which is what drives the turbo. I'm fairly certain that is how it works, but it works pretty much from the start, not sure if it needs a certain speed to create the internal pressure to have more oxygen available for combustion.
But with that design, it cannot be expanded upon. There's one internal pressure and that's it iirc.

 

[MotF Bane]

I like where this is going.

 

[So]

Originally posted by: destrekor

Originally posted by: So

Originally posted by: Rufus12
If they actually got that to work we'd be flying in those things some day.

Ah-ha. Here's our answer. It is impossible.

Remember, frame of reference is irrelevant (Newton said that) so if this were possible, a plane flying through the air would be able to extract energy from the air and travel faster. Perpetual motion as it were. Obviously, this makes no sense, so I'm voting no. Not possible.

In practice it occurs to a limited extent(fixed - ed). Turbo-jets work in that very way: it'll only go so fast, but as the speed increases, the pressure forces more air into the jet which is what drives the turbo. I'm fairly certain that is how it works, but it works pretty much from the start, not sure if it needs a certain speed to create the internal pressure to have more oxygen available for combustion.
But with that design, it cannot be expanded upon. There's one internal pressure and that's it iirc.

All the energy in a turbojet comes from the exothermal reaction of jet fuel and oxygen in air. Some of that energy is bled off to force more air into the engine.

 

[SSSnail]

I got to the part where they spelled "propellor" wrongly and I stopped, though it is physically possible to use wind power to travel faster than the velocity of the wind, it is not in the sense that they're describing.

 

[zoiks]

<Michael_Scott>nooo god noo no god please no no no nooooooo</Michael_Scott>

 

[So]

Originally posted by: SSSnail
I got to the part where they spelled "propellor" wrongly and I stopped, though it is physically possible to use wind power to travel faster than the velocity of the wind, it is not in the sense that they're describing.

Well, yeah. If you have some sort of energy storage device (say, a windmill charging a battery).

Actually, A windmill powering a laser, firing at photocells on the cart would do it, but that's my solution to the Kobayashi Maru test.

Note: I mean a stationary windmill on the ground behind the cart.

 

[SSSnail]

Originally posted by: So

Originally posted by: SSSnail
I got to the part where they spelled "propellor" wrongly and I stopped, though it is physically possible to use wind power to travel faster than the velocity of the wind, it is not in the sense that they're describing.

Well, yeah. If you have some sort of energy storage device (say, a windmill charging a battery).

Actually, A windmill powering a laser, firing at photocells on the cart would do it, but that's my solution to the Kobayashi Maru test.

Sail boats.

 

[wnied]

If they actually got that to work we'd be flying in those things some day.

THEY once said the same thing about ultralight aircraft...

...Gravity Wins! Flawless Victory!

~wnied~

 

[Auggie]

The original idea and sketch doesn't have any energy storage from the slower-than-wind phase of its operation... I think the designer argues that the mechanics are sufficient to transition to above-wind speeds, passively.