Future of Air-travel

[Turtle]

Nice replies.

Roadam, the plane is cool what with Hydrogen fuel & all, but again I don't think we really need to get places fast for the most part. Sure if you got a time-constrained medical reason, but not to go from DC to visit Granny in Moses Lake Oregon and certainly not if there are more efficent means. Waste not, want not.

Pyro, the basic idea for the FBS is grand & beeeeautiful. I think rather than the inner ring deck directly attached to any great circle inside, that all needs to be gymbaled so the FBS is free to rotate on any (many?) axis/axes. It's going to want to tumble anyway, so we control that tumble and actually use it for motation because the pressure on opposite sides of a rotating sphere is differential. (looking for linkage on that.....) Got one!

Originally Posted by Springlink

From a detailed computation of the flow field around a rotational sphere in extended ranges of the Reynolds number and rotational speed, the results show that, with increasing the rotational speed or decreasing the Reynolds number, the lift coefficient increases. ...

SpringerLink - Journal Article

That's all I got...my brain is sore now on account of the thin air.

[Roadam]

Well I haven't heard of that idea before. But it sure looks interesting. As far as I looked into jet streams the speeds are between 100 and 400 kmh so a big sphere could travel with quite a speed. But the acceleration would probably be extremely slow for that giant mass.

And Turtle, that effect is actually Magnus effect. So it would be possible to use that to steer in the wind. Not to mention it would be better to have more than 2 spheres as balloons and whole residential complex as a weight.

As I see it, this particular project would be massive, actually one could compare it to Freedom ship. Vessel that big would move very slow and would only be able to quickly evade something with changing the attitude.

And I would rather fit a fusion reactor onto it. Just in case

Nonetheless, this way we would get a slow and expensive means of transport.

[Turtle]

Originally Posted by Roadam

Well I haven't heard of that idea before. But it sure looks interesting. As far as I looked into jet streams the speeds are between 100 and 400 kmh so a big sphere could travel with quite a speed. But the acceleration would probably be extremely slow for that giant mass.

I agree slow, but again I assert slow is more than fine for most transport and by all accounts more efficient in use of fuel(s).

Originally Posted by Roadim

And Turtle, that effect is actually Magnus effect. So it would be possible to use that to steer in the wind. Not to mention it would be better to have more than 2 spheres as balloons and whole residential complex as a weight.

Thanks for the name & yes I know it is possible which is why I proposed it. Not sure about twin FBS's, but this is where maybe we all ought to start producing some simple drawings or such a matter.

Originally Posted by Roadem

As I see it, this particular project would be massive, actually one could compare it to Freedom ship. Vessel that big would move very slow and would only be able to quickly evade something with changing the attitude.

And I would rather fit a fusion reactor onto it. Just in case

Nonetheless, this way we would get a slow and expensive means of transport.

Again...there is nothing wrong with slow!!!! And no reactor , as there is everything wrong with that in regard to Pyrotex's original FBS design proposal wherin solar energy supplies all the energy.

Expensive to build initially yes, but no less so than building a hydroelectric damn for example. And getting back to the OP here, the current means of air-travel are unsustainable and helping to pollute the atmosphere in a number of ways. Considering that a lot of jet air-travel is for vacations and face-to-face business meetings that can be conducted via the internet, it's a demoralizing scenario if not criminal.

[CraigD]

Originally Posted by Pyrotex

Trans-oceanic commercial travel -- Airships -- Hot Air….

Very cool

On the subject of solar-heated hot air balloons, actual ones like Dominic Michaelis's 1981 English Channel crosser shown at this webpage are, I think, a must-see/read.

I’d have to run a lot of numbers and sketches to have any idea how much one could scale these things up. From Michaelis’s balloons, we can get a rough volume to lifting capacity ratio of about , about 7 times the required volume of a gas burner-heated balloon. This gives Pyro’s mile-wide sphere a maximum mass of about 54,000,000 kg, about the same as the 250 m WWII battleship Bismarck.

A major design challenge in making a purely solar-heated balloon (Michaelis’s had gas burners for use in initial inflation and landing) is to designing something that doesn’t crash. - especially in real outdoor weather. Once a hot air balloon is cooled, and begins descending, you need to have a ready, controllable supply of heat to heat the gas and make it stop. Michaelis’s balloons handled by using their gas burners during landing – otherwise, their landings would have been abandon-ship-with-parachute-type crash landings. A pure solar balloon would need a better system. Over-design it so that you constantly vent hot air in level flight, and/or actively control its transparency and/or opacity are a couple of approaches that come quickly to mind.

Staying up at night is another. At night, obviously, you won’t get significant solar energy input (moonlight really doesn’t count). You’d need to either have super insulation, dump-able ballast, some sort of gas pressure creation and control system, etc. The controls in the previous paragraph would be useless (other than for descending, which is exactly what you want to avoid occurring at night), and all of the solutions mentioned have big drawbacks.

The worst case – and not an unlikely – scenario I can imagine is floating into a region of warmer air at night in the rain. Throw in a strong downdraft, and its even worse.

Of course, these are mere technical challenges – but they’re pretty daunting ones.

No one appears to have mentioned so far what I consider a very straight-forward and proven alternative approach for heavier-than-air craft: battery electric with or without solar photovoltaic. Thousands of sizable model airplanes are airborne as I write using LiPo battery powered electric motor-driven propellers, while some fairly ordinary-looking small manned airplanes have flown respectable distances on photovoltaic power alone. There don’t appear to me to be any major show-stopper barriers to, in the next few years, building a “plug-in solar” electric airliner in the 30-seat, 500 km/h, 1500 km range “regional” class (eg: the BAe Jetstream 41). Though cost will likely be high, major increases in fuel price – which, according to peak oil predictions, is inevitable – you just might be able to get rich selling such a plane.

Though I’ve not worked out even rough engineering details yet, I’ve got a pretty strong sense that we won’t be seeing the last of fast, heavy air travel anytime soon.

[Roadam]

Ok you got me interested and I am brainstorming. So just pull me back in the line if necessary. Maybe we should make a separate thread about this particular idea. Thanx to Pyro for throwing the bone.

The thing is supposed to be at the heights of tropopause where jet stream is. Apart from that I dont see many more advantages beside that there is almost no weather changes up there. No rain and no downdrafts . So that puts the height at about 10-12km. Temperatures up there are somewhat stable at -56°C and the pressure is about 1/4 bar.

After some calculations I think that if you raise the average temperature of the air by 100K the lift at that height is 16m3/kg. Which is ofc proportional to temperature difference.

Another thing CraigD pointed out is insulation. One mile diameter balloon has 8 square kilometer area. So say 0.5 mm metalized film of the density about 1kg/l (Its about the same as water allright ) weights 4,000 tons. Films can be thinner and I guess multilayer approach gives better insulation.

Why is geodesic structure even needed? Balloons are easier to inflate if not rigorous, thinking that light-weight ball shaped geodesic dome would be hard to stand up without support. Balloon would support its shape on its own. Any faults would be negated by many layers. Repairs can be made by moving along meshes between layers. Did I miss anything?

As there is no to any kind of reactor, maybe there should be a big battery stack to storage energy for the night.

A big boost for this kind of flying vessel would be adaptive plastic solar cells, say being able to change the % of transparency/reflectivity on either side.

And by the way, using helium instead of air gives about 250% increase in lift. 600% for hydrogen .


As far as electric planes go. Maximum thermodynamic efficiency of burning kerosene is about 90% (combustion temperature of about 2300K). As temperatures inside jet engines are somewhat comparable.And according to this: http://www.transportenvironment.org/...nd_out/lid:398
the efficiency of airplanes rises now very slowly. I guess the energy efficiency is about 60-70%, correct me if I am wrong. So mechanical propulsion would improve that by maybe 30% at best.

As drag increases alot by increasing speed and density of air, I say that one would get a nicely low fuel consumption with a airplane traveling at 10km and with the speed of about 300 kmh. The thing is that you need very big wings to create enough lift. That in way create more drag, for which you need bigger engines etc...

[Turtle]

Originally Posted by Roadam

Ok you got me interested and I am brainstorming. So just pull me back in the line if necessary. Maybe we should make a separate thread about this particular idea. Thanx to Pyro for throwing the bone.

The thing is supposed to be at the heights of tropopause where jet stream is. Apart from that I dont see many more advantages beside that there is almost no weather changes up there. No rain and no downdrafts . So that puts the height at about 10-12km. Temperatures up there are somewhat stable at -56°C and the pressure is about 1/4 bar.

While Pyro suggested flying in jet streams, I think that was a means for not needing propulsion other than changing altitude by venting hot air to drop or heating the air to rise. If the FBS has propulsion the the jet stream flight is optional.

Originally Posted by Roadam

Why is geodesic structure even needed? Balloons are easier to inflate if not rigorous, thinking that light-weight ball shaped geodesic dome would be hard to stand up without support. Balloon would support its shape on its own. Any faults would be negated by many layers. Repairs can be made by moving along meshes between layers. Did I miss anything?

It may be Pyro went with a geodesic sphere to accomodate Freezters suggestion for that, as well as that I am currently engaged in an in-depth study of Fuller's Synergetics. I see a geodesic sphere as just a closed geodesic dome and it would not collapse even sitting on the ground. If the machinery & occupants are located inside the craft, a rigid structure sounds preferrable to a flacid bag to me.

Originally Posted by Roadam

As there is no to any kind of reactor, maybe there should be a big battery stack to storage energy for the night.

A big boost for this kind of flying vessel would be adaptive plastic solar cells, say being able to change the % of transparency/reflectivity on either side.

Agreed on batteries to store PVC generated electricity.

Originally Posted by Roaddddam

And by the way, using helium instead of air gives about 250% increase in lift. 600% for hydrogen .

Agreed. Again though, Helium is a finite resources and Hydrogen is flammable and neither makes for a breathable atmosphere inside the Floating Bucky Sphere. (note: a geodesic 'sphere' is not a true sphere as it is faceted, so calculations of volume based on a sphere are going to be greater than the actual construction.)

Originally Posted by Craigerino

No one appears to have mentioned so far what I consider a very straight-forward and proven alternative approach for heavier-than-air craft:

I was waiting for you to mention it Craig. I think electric propulsion sounds great on a FBS as well as winged craft. The PV panels could power those motors, make electricity to store in batteries, as well as produce Hydrogen for either added lift by itself or for burning to heat the air in the balloon.

That's all I got.

[freeztar]

Originally Posted by Roadam

Why is geodesic structure even needed? Balloons are easier to inflate if not rigorous, thinking that light-weight ball shaped geodesic dome would be hard to stand up without support. Balloon would support its shape on its own. Any faults would be negated by many layers. Repairs can be made by moving along meshes between layers. Did I miss anything?
...
And by the way, using helium instead of air gives about 250% increase in lift. 600% for hydrogen .

The benefit of the geodesic structure is stability and strength. The structure will not be "closed" and filled with pressurized gases. It would be only air with openings above and below. Hence, I don't see any need to have an amorphous structure (such as a typical balloon).

Anyways, Hydrogen is dangerous and Helium is in short supply.

[Pyrotex]

You guys rock!
Thanks for taking my idea and running with it.

To answer some questions: the "town" within the FBS must be a rigid structure, and so it follows that the whole structure should be rigid.

You don't want to depend on the material strength of a single ginormous balloon. The geodesic structure is the strongest mass/volume structure possible. If the elements are carbon composites, then mass goes down even more.

Given a rigid geodesic structure, you have much more leeway and flexibility on the material used to construct the "skin". Multi-layer super-thin films with low thermal conductivity, high transparency to visible light, and high reflectance of infrared, with super low mass now become feasible.

A rigid geodesic structure enable maintenance and repair that would be impossible in a balloon.

Mounting "black" PV solar cell arrays INSIDE the skin would increase the amount of heat released inside the skin.

Light intensity, especially soft UV, increases dramatically above 20,000 feet, so we should design for the highest feasible altitude. This means that residences and shops will have to be within pressurized facilities. This adds weight.

Even with the jet streams, we have a problem. How to stay IN the jet stream, or how to get back in after we leave and descend to an altitude reachable by helicopters. As much as I dislike it, some form of propulsion is necessary. Maybe a few hundred electric prop-fans mounted on the outside. Given the cross-sectional area of the FBS, you're not going to get more than 10 or 20 MPH out of it all. Maybe that's enough.

Emergency power and heat--a valid criticism. Perhaps a small nuclear reactor (say 10 megawatts) to provide power to the prop-fans. This of course releases 10 megawatts of heat inside the FBS, which may (when added to the insolation) may provide more than enough heat to float the FBS. Which means constant dumping of heat for level flight. Which means a reserve for rapid climbing when necessary.

Just PLEEEEEZ don't suggest the FBS be propelled by burning fuel.

[Turtle]

Originally Posted by Pyrotex

You guys rock!
Thanks for taking my idea and running with it.

Hey! Who took our Bucky ball!

Originally Posted by Pyrotan

To answer some questions: the "town" within the FBS must be a rigid structure, and so it follows that the whole structure should be rigid.

You don't want to depend on the material strength of a single ginormous balloon. The geodesic structure is the strongest mass/volume structure possible. If the elements are carbon composites, then mass goes down even more.

Absolutely. We may yet tinker with the mile-wide size, but rigidity is demanded. Here is a geodesic sphere as a tensegrity structure per Bucky himself: >> Fig. 717.01

Originally Posted by Pyron

Even with the jet streams, we have a problem. How to stay IN the jet stream, or how to get back in after we leave and descend to an altitude reachable by helicopters. As much as I dislike it, some form of propulsion is necessary. Maybe a few hundred electric prop-fans mounted on the outside. Given the cross-sectional area of the FBS, you're not going to get more than 10 or 20 MPH out of it all. Maybe that's enough.

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.

Originally Posted by Pyrotax

Just PLEEEEEZ don't suggest the FBS be propelled by burning fuel.

Roger that...except for as I said, electolyzing water (gathered from the clouds? ) by means of electricity from photovoltaic panels and using the Hydrogen as a combustion fuel where prudent.

[Pyrotex]

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...

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.


[EDIT]-- The Magnus Effect will not provide any propulsion for the FBS.

For ME to work, the ball must be moving through the surrounding air. The FBS has no net velocity with respect to the surrounding air. So you could spin it all you want, nothing would happen. The FBS is carried along by the surrounding air and is motionless with respect to it. NOT like the golfball, which is has high velocity THROUGH the air.