Future of Air-travel

[Turtle]

Originally Posted by Pyrotex

Hmmm.

Well, you're right, I sure don't understand the "Magnus" effect. Without spending some time studying it, I have to say I'm very skep-tickle.

As long as you're smiling & studying, all is right in the world.

Here's a primer from WickedPeedonita on the Magnus Effect: >> Magnus effect - Wikipedia, the free encyclopedia

[Roadam]

For the magnus effect to work you have to have wind and rotation of the sphere must be big enough. By gymbaling the force could be only steered up or down while still being perpendicular to the wind. But it sure would be a small force.

The sphere would have drag coefficient of 0.5. I guess if we want to be run by wind this is good to have relatively high coefficient.
At 10 kmh the force of drag is of about 1 Mega Newtons, at 20 kmh its already 3.5MN. Wind turbines then have to be 3MW and 21MW respectively.

I guess thats why moving in the wind is a good idea.

PS: If one would hoist 3 A380s to it it would be moving at about 12kmh

[Turtle]

Originally Posted by Roadam

For the magnus effect to work you have to have wind and rotation of the sphere must be big enough. By gymbaling the force could be only steered up or down while still being perpendicular to the wind. But it sure would be a small force.

Erhmmm...no; I disagree. Spinning a floating sphere in still air will cause it to move directionally. Moreover, properly gymbaled, any vector for the axis is achievable and so any direction of travel achievable as well.

[Roadam]

Originally Posted by Turtle

Erhmmm...no; I disagree. Spinning a floating sphere in still air will cause it to move directionally. Moreover, properly gymbaled, any vector for the axis is achievable and so any direction of travel achievable as well.

No, that is not the case. Both wikipedia article and the link you originally posted say that sphere has to be moving trough the fluid, or fluid flowing by it . If fluid has no velocity compared to the sphere, the problem has no reynolds number! And hence no wind, no magnus force.

To correct your first post, jet engines have better efficiency than piston ones. It says it in the same article you linked there. On page 22, there is a comparison between pistons and jets, it clearly shows that jet planes have lower energy per seat than piston ones. Thats why piston curve stops at 1970, as it seems piston engines haven't improved since.

[CraigD]

Originally Posted by Turtle

Here is where my proposal fits, and is perhaps yet not understood. By having the living space & mechanics attached rigidly but gymbaled, power is applied at the axes to cause the FBS to rotate and using the Magnus effect we achieve propulsion. Changing the axis of rotation steers the FBS.

There’s a major problem with this scheme.

The Magnus effect produces a force proportional to the square of the velocity of the airspeed of the rotating sphere or cylinder. Balloons and other unpowered lighter-than-air craft, however, move with the wind, and thus have effectively zero airspeed. So, no matter how much power is used to rotate the envelope/hull of the big airship, and how great its angular velocity, the resulting right angle force will be effectively zero.

When moving from between volumes of air with differing wind velocities, there is duration of time before a LTA craft matches the wind’s ground velocity, but it’s brief.

If you want to be able to move a LTA craft against the wind, you need either a thrusts-producing system, such as jets or propellers, a ground/water anchor, or some more exotic but still propulsive system. Due to a big LTA craft’s large frontal area, even if very aerodynamically efficient, it will have a high drag, so moving it at even a low airspeed will require a lot of power.

If the LTA craft can quickly, reliably and accurately change its altitude, and has good data about wind velocities at different altitudes (eg: via detailed doppler radar), it can potentially navigate effectively by selecting an air mass going the desired direction. This is how modern recreational hot air balloons navigate. Even without good wind velocity measuring systems, a good balloonist can, under suitable wind conditions, make round-trips accurately enough to land in the same field he/she takes off from.

[Turtle]

Originally Posted by Roadam

No, that is not the case. Both wikipedia article and the link you originally posted say that sphere has to be moving trough the fluid, or fluid flowing by it . If fluid has no velocity compared to the sphere, the problem has no reynolds number! And hence no wind, no magnus force.

Roger. Bummer. Sorry Pyro n' Freezy.

Originally Posted by Roadum

To correct your first post, jet engines have better efficiency than piston ones. It says it in the same article you linked there. On page 22, there is a comparison between pistons and jets, it clearly shows that jet planes have lower energy per seat than piston ones. Thats why piston curve stops at 1970, as it seems piston engines haven't improved since.

Well, you quote energy per seat and I quoted energy per load if I recall.

Originally Posted by Craigenator

There’s a major problem with this scheme. [of using the Magnus effect for propulsion]

Again, roger that as above. Gave it the ol' college try. As you say earlier anyway, not likely any one's going to actually do work on any alternatives soon, and as I say, people think satisfying their immediate desires are some kind of right because they can afford it and everbody else and the world be damned. People suck & then ya croak.

[Pyrotex]

Originally Posted by Turtle

Erhmmm...no; I disagree. Spinning a floating sphere in still air will cause it to move directionally. Moreover, properly gymbaled, any vector for the axis is achievable and so any direction of travel achievable as well.

Roadam is correct, Turtle. Sorry.

If the FBS has zero velocity with respect to the surrounding air that carries it, then the formulas say that the Magnus Effect is also zero.

Besides, old friend, spinning a sphere of 5,000 Metric Tons with a diameter of one mile would take more power than you could carry.

[Turtle]

Originally Posted by Pyrotex

Roadam is correct, Turtle. Sorry.

If the FBS has zero velocity with respect to the surrounding air that carries it, then the formulas say that the Magnus Effect is also zero.

Besides, old friend, spinning a sphere of 5,000 Metric Tons with a diameter of one mile would take more power than you could carry.

Roger. I acknowledged that in my last post. No harm, no foul.

[Roadam]

There is another thing to consider. At that attitude there is quite some radiation. So more shielding is needed...
All things considered, I dont think the concept would work very well in the end. The sphere wouldnt change its attitude much and you would still need some other type of transport to get onto it.

I think the future of air travel is in flying wings. No matter what kind of engine you use to propel yourself, its the aerodynamics that limits you to certain speeds and power requirements. Making a plane with less drag compared to what it carries it the way to go. And another thing. Flying wings have more or less flat top. So it would be easier to fir PVs onto it.
I think the specs could be generally inserted into an equation, which will wait for now I think.

[Turtle]

Nice to see someone is doing more than armchair speculating. Check this bad girl out!!

Originally Posted by Jonathan Skillings

Photos: The zeppelin flies again
...
The new-model zeppelins are also much smaller--246 feet in length, compared with around 800 feet in the olden days, and carrying just two crew members and up to 13 passengers, compared with a total of 80 to 100 or so for the big ancestors.

For now, Airship Ventures says, it has the one and only zeppelin in the U.S., and that's one of only three in the world.

As you might expect, flights won't come cheap--individual tickets start at $499 per person. (The glider ride, if I remember correctly, was somewhere in the neighborhood of $80. With the zeppelin, I'd be hoping for bit of legroom to go with the view.)

Photos: The zeppelin flies again | Crave, the gadget blog - CNET