Established Member
I have some questions regarding post fossil fuel aeronautics.
1. Is viable commercial aviation free of fossil fuels possible?
2. When could we expect 100% non fossil fuel aviation to become a reality?
3. What are the most promising new fuels, or radical new concepts for this?
4. Would airfare cost more, or less in the future utilizing no fossil fuels?
Order of Kilopi
1) Dependent on the cost of alternatives, but probably "yes"; I think the price of hydrogen is almost close enough to that of Jet-A to be viable.
2) When it becomes cheaper to use non-fossil fuels than fossil fuels.
3) Hydrogen, biofuels.
4) Probably more, but fuel is not the major cost of air operations; it's labor costs -- the normal ratio is about 100 airline employees (including those whose jobs are outsourced to, for example, outside maintenance firms) per aircraft. Fuel is less than 10% of a commercial airliner's operating costs.
Established Member
Tere are already electric airplanes.
http://www.electraflyer.com/
http://www.sonexaircraft.com/research/e-flight/
(but since most electricity comes from fossil fuels......)
Order of Kilopi
If you want to build airships out of carbon fiber , you can push it around with electric , hydrogen fuel cells?
Well, there are ways.
" Ask....the rats. They have ways." Nicodemus from 'The Secret of Nimh '
Order of Kilopi
Gas turbine engines are pretty tolerant of their fuels, but hydrogen is probably the best gas turbine fuel. First, it doesn't have any carbon in it, which is a benefit as the microscopic soot particles transfer a lot of heat via radiation to the turbine blades and vanes, second it burns quickly, so the combustion chamber can be shorter, which has all sorts of benefits.Originally Posted by danscope
Why bother generating electricity to drive electric motors when it's easier to just use gas turbines fueled by hydrogen?
Order of Kilopi
The tanks would be pretty massive, and apparently fuel can not be stored in the wings. Still, it has been done.
Another idea, steam aircraft.
Order of Kilopi
Yes, liquid hydrogen is a low density fuel and you probably aren't going to do much cryogenic storage in the wings. Because of the bulk, hydrogen probably only makes sense for large aircraft. There are conceptual designs for large airliners with liquid hydrogen tanks in the fuselage and there's no doubt the technology could work.
Still, my bet is that the advantages of higher energy density, more easily storied hydrocarbon fuels would make them the preferred choice for most aircraft long after we stopped using fossil fuels. You can either produce them biologically:
http://en.wikipedia.org/wiki/Aviation_biofuel
or produce them chemically in a factory/chemical plant setting. If you're producing hydrogen, it's not that much harder to add carbon. Even when it takes more energy put in than you get out of it (the key difference from today's fossil fuels) it still is a convenient way to store and transfer energy.
I say there is an invisible elf in my backyard. How do you prove that I am wrong?
The Leif Ericson Cruiser
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The US Air Force has a rather strong program in the development of aviation fuels using GTL (Gas To Liquid) technology, using the Fischer-Tropsch process. This would convert either natural gas or "syn gas" made from other sources (like coal or bio) to liquid aviation fuel. I've been to several talks from those working on this and it is well along the development path.
Order of Kilopi
The problem with hydrogen, in addition to the difficulty of storing it in an airplane, is that the most practical way of getting it is by electrolyzing water. With electricity. From what is usually a fossil-fuel power source.
There's lots of work being done on bio-fuels in the past few years. The US Air Force is very interested. Unfortunately, considering how incompetent the USAF seems to be on its major development programs, that may not be a good thing.
Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.
Established Member
Fossil fuels gain their greatest commercial advantage in mobile applications, because the energy density of fossil fuels is so high. An indication that commercially viable fuelling of vehicles with energy of non-fossil source is becoming possible would be the prior abandonment of fossil fuelling for non-mobile applications.
So, when coal, oil and gas are so expensive in comparison to the alternatives we no longer find them to be commercially suitable for large scale generation of electricity and heating our homes, then we might start to find commercial solutions for the more challenging problem of commercially fuelling vehicles with energy forms of non-fossil origin.
Order of Kilopi
Where did you get that figure?
Delta's numbers are 36%.
Order of Kilopi
Order of Kilopi
How many years ago?
With the rise in oil the last few years, and the airlines going toward a minimal service model, I can see it having such a large impact.
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Order of Kilopi
Some interesting concepts
http://www.trendhunter.com/trends/al...batic-aircraft
http://www.earthtechling.com/2010/06...skies-by-2013/
Now I seem to remember reading about high flying craft that used propellers and carried both their fuel and their oxidizer somewhere. The propellers would push the air even above the level where air-breathing combustion could take place:
https://www.aiaa.org/PubDetail.aspx?id=1803 Lots of interesting concepts there.
Other books
https://www.aiaa.org/PubDetail.aspx?id=4002
https://www.aiaa.org/PubDetail.aspx?id=1425
https://www.aiaa.org/PubDetail.aspx?id=1450
https://www.aiaa.org/PubDetail.aspx?id=1355
High flying craft:
http://en.wikipedia.org/wiki/Grob_Strato
http://www.airliners.net/aviation-fo...d.main/137685/
Misc
http://www.alternatehistory.com/disc...d.php?t=198573
I am interested in the concept known as vacuum filled balloons/airships
http://en.wikipedia.org/wiki/Vacuum_balloon
Order of Kilopi
There are a lot of high-efficiency aircraft concepts, such as joined wing and high-aspect ratio, externally braced wings.
And, of course, propfans, which have significantly higher propulsive efficiency than turbofans. Propfans even look cool.
Established Member
Um, unless you're going with Scimitar, Sabre, or some other super high speed design there's really no need to do without fossil fuels. Only 7% of the oil used in america is used for airtravel. Considering the huge challenges in trying to engineer some kind of alternative fuel system (no way solar and batteries will ever power a passenger jet), why not spend those millions developing better batteries for passenger vehicles? If nanowire batteries can be economically produced, that would make a much bigger dent oil usage than fossil fuel free jets will.
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If you don't want to use fossil kerosene, use non-fossil kerosene.
Publiusr, I see a future for airships, but the concept of a vacuum balloon is probably unachievable and any increase in buoyancy is likely going to be mitigated by increases in structural mass... unless people start positing carbon-megacubes.
Et tu BAUT? Quantum mutatus ab illo.
Established Member
Airships are large, slow, and ungainly. Despite their massive size the largest, the Hindenburg class, could only carry 72 people. despite being 803 feet long.
Order of Kilopi
I wasn't suggesting them for public air transport. I'd use them for other roles. But an estimation on carrying capacity might need to be updated to reflect new materials.
Et tu BAUT? Quantum mutatus ab illo.
Order of Kilopi
If you didn't have sleeping quarters and pianos and the like, and simplified the food service, I feel sure that you could carry a much larger passenger capability. But service and schedules will always be a function of weather. It means the construction of enormous hangars, even floating hangars which doors always face downwind. It is possible and , given the
situation of difficult fuel access, more practical than ocean liners, if speed is considered. Air travel is comprised of
compromises. First class or steerage; you pick. DC-3 or Concorde ? It's a brave new world.
Best regards,
Dan
Order of Kilopi
We still fly DC-3, we don't fly Concordes.
What a world, eh?
Established Member
Ok, what other roles do you have in mind?I wasn't suggesting them for public air transport. I'd use them for other roles. But an estimation on carrying capacity might need to be updated to reflect new materials.
Several problems:
1.) Without those ammeneties a trans atlantic trip would be unbearable, it took the Hindenburg 2-2.5 days to go that far.
2.) Weather is unpredictable, and therefore it's better to have technology that depends less and less on it, not more and more.
3.) Fuel access is not really a big problem at all. As stated the oil consumption from air travel is only 7% of total use. If we really have to, it should be possible to use synthetic oil derived from coal, which we have plenty of and is a proven technology. And really, in this century we will see hypersonic passenger craft which use hydrogen, further reducing the oil usage by conventional jets.
We're not going to give up high speed air travel. At worst air travel prices will go back to what it was before deregulation.
Order of Kilopi
And an airship can't easily be used as a weapon against skyscrapers--unless you count Black Sunday of course.
Somewhere, there is a new legal department for an airship company waiting for another 9/11, so he can lobby for new laws permitting airship passenger travel only.
Established Member
That's really the only answer needed. Barring unexpected technological changes or political interference that wont be for a long while, probably not by the end of the century.
most airlines reported fuel costs of between 30 and 40 percent of total expenses—exceeding the amount spent on labor. June 2008
- Fuel and air transport, A report for the European CommissionThe rise of fuel prices has increased its proportional contribution to airline costs. Fuel
costs used to represent the second largest part of airlines’ operating cost after the
personnel costs. The situation has been reversed since the fuel price rose rapidly from
2004, and other costs, especially distribution, have declined or increased only slowly.
Fuel represented less than 14% of total operating costs in 2003, but rose to more than
26% in 2007 (Figure 5) with the proportion likely to be even higher in 2008.
- InvestopediaAccording to the Air Transportation Association (ATA), fuel is an airline's second largest expense. Fuel makes up a significant portion of an airline's total costs
Order of Kilopi
Getting rid of the piano would free up enough mass for about 2 more people. The particular piano on the Hindenberg was built to weigh less than 360 lbs. It was removed when they refit the airship to make room for more passengers.
Et tu BAUT? Quantum mutatus ab illo.
Order of Kilopi
Not unless it was armed with weapons, but then it'd be a military aircraft instead of a civilian aircraft, if that's what you're getting at. I'd put lasers on some of them for ABM patrols at high altitude. Those might start fires in a skyscraper.
In addition to the above, they might be sensored for maritime and border surveillance and perhaps even armed for interdiction of smugglers and pirates. They might also be capable of performing Search-and-Rescue activities. While searching would be a strong capability, rescue would be less straightforward. Perhaps they would deploy a one-way rescue craft thatcoastsglides to the surface and contains survival essentials and/or medical kits for use on the ocean or various land wilderness environments. A rescue jumper may also be deployed.
They might also be used as science observatories at high altitude. I'm mostly thinking about long-duration flights (30-90 days) at stratospheric altitude for most of these missions. I was also thinking about designs that works both with lifting gas and aerodynamic lift powered by small, helium-cooled nuclear reactors.
Last edited by Ara Pacis; 2012-May-21 at 05:59 PM.
Et tu BAUT? Quantum mutatus ab illo.
Order of Kilopi
They would use a Yamaha keyboard (portable today) .There would be a revolution in weight savings across the board
in building and fitting out such a craft. It would make the Zepplin Company 's head swim of the wildest dreams of engineer's avarice.Imagine just how many functions would be handled by cell-phone/ wireless control? Air over hydraulic systems with 10% of the weight of another design are quite possible targets. Scimitar blade propulsion , Turbine/electric
propulsion and vectored thrust are just a few of the possibilities, and of course the tail would have a deployable castering wheel (swivel). The skin of couse would be leagues ahead of what they managed in 1937. Still, it's not all champagne and roses, but ......how elegant . And you seats adjust back another 12 inches for sleeping. Yesss! Yessss!
Dan
Order of Kilopi
Actually, I assumed they'd use an iPod. Even smaller.They would use a Yamaha keyboard (portable today) .
I'm not an engineer, unfortunately, but I assume there'd be quite a lot of mass savings in using fiberglass, carbon fiber & resin, aramid fiber cords, poly gas cells and plastics in other places over Duralumin.There would be a revolution in weight savings across the board in building and fitting out such a craft. It would make the Zepplin Company 's head swim of the wildest dreams of engineer's avarice.
I was thinking about the possibility of a nuclear thermal jet using the coolant loop for safety instead of routing through the core (as in Project Pluto). I think there's a name for this specific configuration but it escapes me at the moment.Imagine just how many functions would be handled by cell-phone/ wireless control? Air over hydraulic systems with 10% of the weight of another design are quite possible targets. Scimitar blade propulsion , Turbine/electric propulsion and vectored thrust are just a few of the possibilities...
For a passenger liner, sure, but for my purposes there would be no need for wheels since it would never land once launched.and of course the tail would have a deployable castering wheel (swivel). The skin of couse would be leagues ahead of what they managed in 1937. Still, it's not all champagne and roses, but ......how elegant . And you seats adjust back another 12 inches for sleeping. Yesss! Yessss!
Et tu BAUT? Quantum mutatus ab illo.
Order of Kilopi
I just meant that you can't collapse a skyscraper by ramming an airship into it. It would be bad for the airship, but the building would be fine apart from a few windows and what not.
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