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What is the future for air travel given peak-oil, CO2 emissions, and the general world-wide enegy use?

 

I only seized on the topic a bit ago and I haven't done a lot of research yet, but maybe the commercial jet age is done for. :D Renewable fuels in piston engine planes? :confused: Airships? We don't need to fly anyway? I dunno. :bouquet: Whatcha think bink? :embarassed:

 

In the 5th edition of his book on commercial aviation John Frederick notes that jets “consume more fuel in relation to loads carried and distances flown” as compared with both piston-powered and turboprop-powered aircraft (Frederick 1961; p. 18).
http://www.transportenvironment.org/Publications/prep_hand_out/lid:398

 

Diesel? Aircraft diesel engine - Wikipedia' date=' the free encyclopedia[/url']

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Cool topic! :confused:

 

I like the idea of airships. Modified blimps with simple motors. It would obviously take a lot longer to reach a destination, but it could be CO2-free and very cost effective. What about a floating buckeyball made out of photovoltaic material? :embarassed:

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Cool topic! :)

 

I like the idea of airships. Modified blimps with simple motors. It would obviously take a lot longer to reach a destination, but it could be CO2-free and very cost effective. What about a floating buckeyball made out of photovoltaic material? :embarassed:

 

Ahhh the dreams...:confused: That's why I included airships, but alas it does not look promising. Geodesic sphere maybe :hihi:; stability of so massive a bag as required is a major hurdle with current designs. Some kinda gyro stabalization like Segue I suspect? Then there is the nasty fact Helium is a finite resource and Hydrogen is flammable. :xx: :naughty:

 

If we cut out the jets, then there go the contrails (do piston engine planes leave contrails? :doh:), and by all accounts the contrails are dampening the rate of global temperature rise. :D

 

Overall, I think we don't have a good reason to fly 60% or more of the time. Goll durn waste is all it is and efficient waste is still waste. :cussing: In my day....:doh: :hyper: :bouquet::

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I have two words for this topic:

 

~~~~~>>Maglev Trains>>

 

I think a comfortable high speed ride across the countryside sounds pretty good.

 

As long as we can figure our how to minimize frequent stops.

 

I'm with you on some kind of trains. :doh: Whatever the particulars, I think the computer control is the answer here to the general problem of controlling the flow.

 

Refits of existing highways and electric computer controlled buses and 'pods'? (I saw someone mention this here somewhere but can't find it for reference. :D)

 

So BOT, the future of commercial air travel is in the dumper then? :embarassed: If we were meant to fly we'd have grown wings by now. :confused: :bouquet:

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Ahhh the dreams...:) That's why I included airships, but alas it does not look promising.

 

It might be our only option once fuel gets low. :shrug:

 

Geodesic sphere maybe :hihi:

Righto :doh:

 

stability of so massive a bag as required is a major hurdle with current designs.

 

I must profess that I'm not too up to date on current designs, but I'll do some reading.

 

Then there is the nasty fact Helium is a finite resource and Hydrogen is flammable. :naughty: :naughty:

Yes, but I hold onto the hope that H can be used in some other way (economically)?

Overall, I think we don't have a good reason to fly 60% or more of the time. Goll durn waste is all it is and efficient waste is still waste. :cussing: In my day....:doh: :hyper: :iamsmiling::

 

Indeed. Get a webcam and get on skype. That could possibly eliminate 1/3 of all business travel.

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It might be our only option once fuel gets low. :hyper:
I'm thinking bio-fuel is fine, at least in the piston engines. I don't know about bio-jet-fuel, but I don't like the contrails in any case. :naughty:

 

Righto [on geodesic sphere] :doh:

That was inadvertant pedantism on my part. Gesundheit! :hihi:

 

I must profess that I'm not too up to date on current designs, but I'll do some reading.
Roger. Mostly cigar shape, but some delta-wing experiments I think as well as spheres. Let me know what you find.

 

Yes, but I hold onto the hope that H can be used in some other way (economically)?
Me too. Hope is all that's keeping me alive...that and a little breathing from time to time. :doh:

 

Indeed. Get a webcam and get on skype. That could possibly eliminate 1/3 of all business travel.

 

I'm not familiar with that Skype thingy, but if it saves energy and doesn't pollute as much as otherwise, then rock on. :shrug:

 

Then there is the over ocean jet travel. :) That's gotta go. :iamsmiling: Large piston planes, our airships or go by sailing ship (OT: some hybrid like Cousteaus Alcyone perhaps? )

 

In the mean time, we need to cut out all the uneccessary jet flights. Yeah, I'm talking to you John Travolta!! :naughty: :D) :cussing:

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One that I like:

Reaction Engines Limited :: LAPCAT A2 Facts and Figures

 

I recalculated the use of energy per seat per kilometre. Its high, its about 17 MJ.

Current jet airplanes have this figure somewhere around 1 - 1.5

Using about the same calculations, my car which uses 5l/100km gets 2MJ figure if I drive alone.

 

Jets vs pistons

Jets go at very high altitudes at high speeds (0.8 mach+) and are about as efficient as piston/propeller planes which go at lower attitudes at lower speeds(0.5 mach). By efficient I mean that they have about the same consumption per seat per kilometre. So which would you choose if you want to get somewhere?

 

I think that air-travel will stay course someone will always want to get somewhere very quickly. Although various maglev trains are possible, just to build a track for it requires massive amounts of of energy and materials.

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

 

I saw a detailed analysis of this once. Consider a geodesic sphere about 1 mile in diameter. The skin should be a flexible glass-like material that shares this property with ordinary glass: it reflects infrared light. This means that sunlight will heat the air within, making it less dense than the air outside. This sphere will float at altitudes between 8,000 and 28,000 feet, even though the entire structure will mass hundreds of thousands of tons!

 

On the interior of the sphere, where the "equator" would be, build a small "town" of buildings, homes, shops, restaurants and hotel rooms--extending all around the equator. This will house both the travelers and the residents who make their living maintaining the floating Bucky sphere (FBS). Also build a series of shelves that extend inward from the skin about 200 yards. This is where the helicopters will land and embark and disembark the travelers. (If you're metric, just translate 1 yard = 1 meter.)

 

At the bottom of the FBS, leave open a circular hole about 1/4 mile wide. This will not cause the FBS to fall, because hot air rises. At each destination, helicopters will ascend from the ground, enter the hole and land on the interior shelves and drop off their travelers. Then they would pick up those who are disembarking, take off and descend back through the hole and land on the ground.

 

Altitude control of the FBS would be via a series of electrically operated vents near the top (to drop the FBS); and via the photovoltaic panels that occupy 10% of the FBS surface. The PV panels can be temporarily swiveled to allow more sunlight in (to raise the FBS).

 

There is plenty of room on the FBS "equatorial shelf", as you have 3.14 linear miles of "equator" times 200 yards of width. This yields more than one million square yards of area. Even if 50% of this area was residential and commercial buildings , you would have plenty of room for the helicopters. This leaves room (and to spare) for 8 helicopter landing fields, each 400 yards by 150 yards.

 

The residential and commercial area of the equatorial shelf could be several stories tall, built just inside and against the outer skin. If we choose 3 stories, then we have about 1.6 million square yards of living space. If half of that was reserved for residents and passengers, 800,000 square yards would accomodate 8,000 people (at 100 square yards per person). This would reflect a resident population of about 4,000 -- sufficient for service trades in addition to the onboard maintainance necessary. The other 4,000 people would be the travelers.

 

The FBS would mostly travel with the jet streams, at speeds of less than 200 mph. It could descend out of the jet stream, bringing their relative speed down to local windspeed, transfer passengers by helicopter, then ascend back into the jet stream to continue its undending voyage. And unending it would be, for the FBS would never -- COULD never -- land. Once constructed and launched, it floats forever, until it crashes.

 

This would make intercontinental travel much slower, and you would have to begin and end your jaunts at cities near the jet stream. You would have to time your departure to the schedule of the FBS as it circles the globe. The FBS is powered entirely by solar energy and has no engines, no motive power of any kind.

 

But what a frakin adventure!! ;)

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Nice replies. :eek2:

 

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. ;) :hihi:

 

Pyro, the basic idea for the FBS is grand & beeeeautiful. :hihi: 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.....:read:) Got one! :hihi:

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. ;) :hihi:

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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.

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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).

 

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.

 

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 :jab:

 

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

 

:jab: 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. :earth: :read:

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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 [math]40 \mbox{m}^3/\mbox{kg}[/math], 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.

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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/Publications/prep_hand_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...

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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.

 

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. :)

 

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.

 

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.)

 

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. :hihi:

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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 :hihi:.

 

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. :)

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