Aviation future

Andre

In another thread we talked about converting to a durable economy that is not dependent on fossil fuel. Now flexibility on energy and mobility seem to be inverse proportional. In static plants you can use anything that's available. Cars are more limited although there is still a range of possible energy sources (gaz, gaseous, electrical). Aviation however seems to be fully dependent on liquid fuel.

Some remarks:

How are we going to continue to sustain Jumbo-jets and Air-busses with fuel. Synthetic fuels? Perhaps but any idea how much jet - air fuel A1 is consumed every second?

I see some 300-500 Airlines continuoisly airborne over Europe. That may amout to 1500 - 2000 worldwide perhaps? Average fuel consumption some 9000 liters per hour, say 3 liters per airliner per second. How are we going to produce 6000 minimum liters (1600 gallons) of synthetic fuel per second?
Aviation is an intrinsic part of the economy and booming business
-Aircraft propulsion is dependable on liquid fuel and lots of it.
-Liquid fuel in massive amounts is only available from fossil origine
-If that's no longer economical feasible what are we going to burn in the planes?
-A synthetic liquid fuel (alcohol?) may not be producable at the required rate.
So we need to think about something else and fast, since jets take a decade or so to devellop and three decades to mature and we don't know how much time we have.
Soving this issue seems to be an essential mission and the first to do that has excellent chances for a lead position in the future.

So are there devellopments in this direction. Any thoughts?

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FredGarvin

In terms of propulsion, the alternative fuel sources just are not there yet. So the direction has been and will be for quite some time, to get lighter and more efficient. The next big thing is the use of ceramics into what used to be metallic components. New sweep designs for blades is also helping the overall efficiencies. As far as synthetic fuels are concerned, the price per gallon is definitely cost prohibitive at this point.

Andre

Problem is that when peak oil production is reached, fossil fuel will get cost prohibitive too very soon.

wolram

Gold Member
Maybe the problem is that people "have" to be at certain places
at certain times, that is what guzzles un renewable fuel, in the years
before aviation sailing vessels took months to reach there destination,
so is it not our lifestyle becoming more and more hectic that is at
fault, so chill out and catch the next Super blimp and allow an extra
couple of days to your business, holiday trip.

Francis M

Maybe what we need to do is start by converting the easier stuff over to alternative energy sources. Thereby leaving more fossil fuels for the less easily convertible vehicles. Then perhaps as the alternative fuel/energy technology becomes more developed it becomes cheaper, more versatile and then gets implemented on the harder to convert stuff.

cronxeh

Gold Member
I think in terms of propulsion the only alternative for fighter jets and supersonics and space shuttles would be EM-based 'miracle' of some sort.

As far as petrochemical industry is concerned - they'll never go away. Oil is a hydrocarbon and we need oil to simply survive and sustain our organic heritage. From drugs to foods to nylon to polymers - we need the benzin rings and aromatics and the whole nine yards.

For big aviation - jumbo jets and so on - the alternative might become bubble-based fusion propeller-driven system. Its never going to be supersonic, but then again I dont think I'd want to fly supersonic in a jumbo jet.. its just never going to be safe. Going at 0.8 M is good enough for almost anyone.

Another alternative is hydrogen fuel.. this would be the best alternative since most of the universe is hydrogen.. and if we run out of it we can always "make more" through nuclear means.

FredGarvin

Aviation is just like anything else in this world. It is driven by the economy. The nanosecond it becomes cost prohibitive to do something one way, it gets changed. Plain and simple. Until this, what I call fictious, day of "peak oil" arrives, small steps will continue to happen like they are now.

cronxeh

Gold Member
It is plausible we will be living in another ice age before we run out of oil, and THEN we'll expend the oil reserves at exponential rate.

oldunion

i definately see the materials of the aircraft changing. Carbon fiber, new alloys, ceramics.

Now bear in mind that the plane is already developed. But back in the day (1911?) planes were just made, think of long it took to make them commerically useful and how much time was spent prior on fool's errands that never worked.

If the next energy source will fit in a plane, then fine. But something tells me we will have to wait for new technologies to go with the new propulsion systems.

ohwilleke

Gold Member

Aviation fuel is 1% of consumption. Fuel is 14% of airline costs. And, in Europe, the tax portion of fuel is a big part of the total cost, so prices don't fluxuate as rapidly in response to oil price hikes. An increase of oil prices from the current $50 a barrel to$400 a barrel would double the cost of an airline ticket. (By comparison, a passenger car now costs about $20,000 for a midrange model with lifetime fuel costs of ca.$10,000 at $2 a gallon, but at$16 a gallon, the car would still cost $20,000, but the fuel would cost$80,000, increasing the total cost of driving a car three fold plus, with an even bigger impact for freight trucks). Business travel and the rich leisure traveler would absorb this (and perhaps put up with coach class seating). Leisure travel by the middle class would fall off.

There would be far more impact in freight and leisure traffic, which would switch to far more fuel efficient rail and seaborn approaches for medium and long haul distances, and could use electric vehicles (which don't make sense now, but would if oil prices went up eight fold) for local transporation (they perform equally well, but cost a bit more for the vehicle (maybe 50%) which would come down in mass production-- fuel is already cheaper-- and they have limited range ca. 80-120 miles, which is fine for short haul trips).

If oil was gone, biofuels could replace the entire demand of the aviation sector which would be somewhat smaller that the current aviation sector at those prices. (Indeed, as long as oil became more expensive than biofuels, biofuels would replace mineral oil entirely). Rape seed oil can't easily supply all current fossil fuel demands, but it could meet the aviation sector's demands which are so small compared to total oil demand.

Note also, that it doesn't even matter if biofuels are negative energy products (as critics, probably incorrectly, claim). The point of using biofuels for aviation is to convert energy you can easily produce with alternatives for electricity, into a liquid fuel that doesn't have good alternatives.

Of course, there would also be more of an incentive to make planes more fuel efficient per passenger, if prices went up. Sending your luggage ahead by rail, for instance, while you fly, would probably become more common, in addition to more cramped business class seating.

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Astronuc

Staff Emeritus
The key to fuel is "available energy per unit mass" of the fuel itself and of the chemcial-to-mechanical conversion system. That makes it hard to replace current fossil fuel based aviation with alternatives.

Solar Powered aircraft and terrestrial vehicles have been developed. However the specific energy of such systems is low compared to fossil fuel systems.

In fixed power plants, mass is not so much an issue. One does not worry about moving the fixed mass. Mass is a technical and economic constraint in propulsive systems.

As for fossil fuel based propulsive systems (alternatives are discussed in another thread), a by-product of the hydrogen economy would be continued, but limited reliability on fossil fuels. http://www.ecn.nl/biomassa/research/poly/ftsynthesis.en.html [Broken] is one possiblity to recycle CO2. Of course, economics will dictate how this would be implemented.

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physicsCU

As far as space applications go, they hardly use fossil fuels for that. Commonly we see solid chemicals or liquified gases used as propulsion. Also, hybrid rockets are coming into their own.

However, from what I read, aviation fuel can be converted to a non fossil fuel. I wonder if hydrogen could be a possibility? Probably not, but it is an interesting idea.

But I think converting aviation fuel and other high octane fuels should be put off since those are in use much less than fuel for cars, trucks, oil for engines, etc.

gschjetne

I'd say we stop using liquid fossile fuel down on the ground, and leaves it to the aviation business instead, if we can come up with good, convenient alternatives.

When it comes to saving fuel in the aviation business I'd introduce propeller-driven stirling-powered airliners. Not everybody needs to go at Mach .8 all the time. And this might also open up for more comfort instead. Plus, a stirling could burn Jet fuel, just like a turboprop or jet, only being more efficient, especially at altitude, with the increased temperature delta in the cold air.

Also, how feasable is it to power an axial compressor using a well-balanced stirling? Could this make a new efficient jet-like design? Kind of how recip engines power jetskis.

physicsCU

Propellor driven is a bad idea. You cannot go as high, meaning that your max altitude, where it is best for fuel economy, is in areas of high turbulence. Jet engines can fly higher than any propellor. It is the inherent nature of the two, no matter the fuel being used.

It also represents a step backward in aviation technology, and you will see the downfall of the industry if you try to use props again.

physicsCU

What is biodeisel made out of?

I know the busses around here use it, and I am wondering if that isnt a viable option.

lengould

Agreed that a bio-diesel could work as a jet-fuel, but as long as we're going to do a replacement, why not at least rationally investigate all the alternatives? IF liquid hydrogen tanks can be fitted onto new designs of aircraft, which I think should be do-able, (eg. take the added small frontal cross-section hit of a pair of tube tanks installed below the cargo deck for the length of the fuselage in return for a 60++ % reduction in fuel mass. I THINK any good aircraft engineer would go for that. Sure you've then got to add strength to the wings because the fuel mass isn't distributed along the wings but is concentrated at the centre, but that's a HUGE reduction in takeoff weight too).

Aircraft, rail locomotives, and heavy trucks should be the first items (in that order) converted to H2 fuel, all before automobiles, where the fuel use is so unpredictable, the quantities too small to make the tanks efficient, and the tanks need to be kept in people's garages. Save any bio-diesel for hybrid auto drivetrains.

gschjetne

physicsCU said:
Propellor driven is a bad idea. You cannot go as high, meaning that your max altitude, where it is best for fuel economy, is in areas of high turbulence. Jet engines can fly higher than any propellor. It is the inherent nature of the two, no matter the fuel being used.

It also represents a step backward in aviation technology, and you will see the downfall of the industry if you try to use props again.
I don't see why we have to use jets just because the technology is there. And when it comes to flying high with props, it shouldn't be a problem at all, just consider the Grob Strato 2C, designed for Flight level 790!
Just select a large prop disc area, because of the low indicated airspeed at high altitudes. This also gives the plane excellent STOL capabilities.

And for saving fuel, I wouldn't mind using twice the time to get to, say, Vancouver if I can travel in reasonable comfort without having to pay any more than what I would have to pay for the jet anyway. But of course, there will always be those in a hurry, so I wouldn't convert all the worlds airliners into props, that would be blowing the whole concept out of proportion.

And someone mentioned that the decompression of $H_2$ would serve as an intercooler. Wouldn't that just be part of the problem? Using energy to get rid of energy? We'd want to use as much as possible of the fuel's enthalpy to propel the aircraft, wouldn't we? And with todays technology the closest we could come to that would be a stirling prop.

ohwilleke

Gold Member
physicsCU said:
What is biodeisel made out of?

I know the busses around here use it, and I am wondering if that isnt a viable option.
Biodiesel is made out of plant and animal oils. The most common sources are soybean oil, rapeseed oil and restaurant grease. Biodiesel is compatable with existing diesel engines without modification.

lengould

gschjetne: Serious errors in physics re: your last para. Suggest studying harder.

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