Electric airliner ?

[glazbagun]

I wonder if it might be possible using two stage aircraft like they do when they're testing Hyper-X/a new rocket plane/whatever-

Plane has it's own blimp, floats up to 40K feet, then sperates and cruises to its destination on electric power. Mothership/blimp returns to take-off base on autopilot. Might be a solution for an energy scarce future.

[JuniorD]

Foliage said:

J4CKO said:

What happens when the fossil fuels run out,

We have 1000s of years of fossil fuels left, but that's an aside since we can also build engines that can burn vegetable oils.

But that doesn't get round the fact that we are spewing noxious gas into the atmosphere, whether mmgw is a thing or not.

Electric airliners would be a rather big challenge, a better approach would be to address shipping & industry first.

Private citizens and aircraft are the least of the problem.

I#m looking forward to when Jet A1 is replaced with vegetable oil. Airports will smell like a gaint chippy!

[uncinqsix]

JuniorD said:

Foliage said:

J4CKO said:

What happens when the fossil fuels run out,

We have 1000s of years of fossil fuels left, but that's an aside since we can also build engines that can burn vegetable oils.

But that doesn't get round the fact that we are spewing noxious gas into the atmosphere, whether mmgw is a thing or not.

Electric airliners would be a rather big challenge, a better approach would be to address shipping & industry first.

Private citizens and aircraft are the least of the problem.

I#m looking forward to when Jet A1 is replaced with vegetable oil. Airports will smell like a gaint chippy!

A few years back, I attended a talk given by a bloke from Boeing. From what he said, it very much sounded like the future is in biofuels derived from algae. Stuff that grows fast in what is basically wastewater. From memory, the figure he quoted was that an area the size of Belguim would produce enough fuel for the entire global airline industry. Fascinating stuff, and I think they've already at the flight trial stage.

[Simpo Two]

It seems an excellent use for Belgium.

[J4CKO]

JuniorD said:

Foliage said:

J4CKO said:

What happens when the fossil fuels run out,

We have 1000s of years of fossil fuels left, but that's an aside since we can also build engines that can burn vegetable oils.

But that doesn't get round the fact that we are spewing noxious gas into the atmosphere, whether mmgw is a thing or not.

Electric airliners would be a rather big challenge, a better approach would be to address shipping & industry first.

Private citizens and aircraft are the least of the problem.

I#m looking forward to when Jet A1 is replaced with vegetable oil. Airports will smell like a gaint chippy!

All those dodgy old blokes that do car boot sales in veg oil powered Peugeot 405's will be drafted in as consultants.

[Fugazi]

Simpo Two said:

Even if it was possible, what would the top speed of an airliner with electric ducted fans be?

The majority of the thrust from a high bypass ratio turbofan engine comes from the fan, with about 10% coming from the hot core engine exhaust. That fan could be driven by an electric motor and you'd see no difference in thrust as long as you provided the same power as the gas turbine. It would require a huge amount of electrical energy though and that's the problem, no current battery or power generation methods can match a kilogram of kerosene containing 43 million joules of energy, especially for aviation.

But that doesn't mean we shouldn't be working towards it. As much as I love them, and believe me I do, have been building them for twenty years, written engine simulations, designed them.... The modern gas turbine has gone about as far it's possible to go. The latest Rolls Royce turbofan engines are so close to the maximum possible thermal efficiency that huge amounts of research is being carried out to eek out a further fraction of a percent of performance. Simply put, the maximum power you can extract from a gas turbine occurs when the difference between the ambient temperature and the temperature of the flow through the turbines is at a maximum. So the turbines are having to operate in flows way above the material melting points, individual blades are grown from single crystals to ensure that they can withstand the stresses involved in high temperatures and rotational speeds, thermal ceramic coatings are required along with complex air bleed systems needed to cool each blade. The compressors are also sensitive to debris ingestion and dirt accumulation on the blades which can ruin the aerodynamic performance, fluctuating intake temperatures can also lead to compressor surging. I wrote a paper a few months ago on some of these issues surrounding maritime helicopters ingesting hot ship exhausts with subsequent drops in engine power, which has lead to numerous crashes onto offshore platforms. An electric motor would remove all these issues.

Also gas turbines (jet engines) can burn anything, diesel, oil, kerosene, wood, coal, (seriously, somebody once fueled a homebuild gas turbine with vodka, expensive way to make an expensive hobby more expensive).... All you have to do is add enough energy (heat) to the compressed air to generate enough power to drive the turbines and the easiest way to do this is with a combustible fuel. But you could also supply that energy via a heating element and electrical energy or a nuclear reactor. But that would be far more inefficient than driving the fan directly.

[hidetheelephants]

Brayton cycle turbines are likely to bring new levels of efficiency to electricity generation as and when the materials issues can be sorted; a brayton turbine and a molten salt reactor has a potential thermal efficiency of over 60%.

[Sireatalot]

williamp said:

Only with inflight refuelling. Like this:

1.21 gigawatts. Great Scott!

[Willy Nilly]

Fugazi said:

The majority of the thrust from a high bypass ratio turbofan engine comes from the fan, with about 10% coming from the hot core engine exhaust. That fan could be driven by an electric motor and you'd see no difference in thrust as long as you provided the same power as the gas turbine. It would require a huge amount of electrical energy though and that's the problem, no current battery or power generation methods can match a kilogram of kerosene containing 43 million joules of energy, especially for aviation.

But that doesn't mean we shouldn't be working towards it. As much as I love them, and believe me I do, have been building them for twenty years, written engine simulations, designed them.... The modern gas turbine has gone about as far it's possible to go. The latest Rolls Royce turbofan engines are so close to the maximum possible thermal efficiency that huge amounts of research is being carried out to eek out a further fraction of a percent of performance. Simply put, the maximum power you can extract from a gas turbine occurs when the difference between the ambient temperature and the temperature of the flow through the turbines is at a maximum. So the turbines are having to operate in flows way above the material melting points, individual blades are grown from single crystals to ensure that they can withstand the stresses involved in high temperatures and rotational speeds, thermal ceramic coatings are required along with complex air bleed systems needed to cool each blade. The compressors are also sensitive to debris ingestion and dirt accumulation on the blades which can ruin the aerodynamic performance, fluctuating intake temperatures can also lead to compressor surging. I wrote a paper a few months ago on some of these issues surrounding maritime helicopters ingesting hot ship exhausts with subsequent drops in engine power, which has lead to numerous crashes onto offshore platforms. An electric motor would remove all these issues.

Also gas turbines (jet engines) can burn anything, diesel, oil, kerosene, wood, coal, (seriously, somebody once fueled a homebuild gas turbine with vodka, expensive way to make an expensive hobby more expensive).... All you have to do is add enough energy (heat) to the compressed air to generate enough power to drive the turbines and the easiest way to do this is with a combustible fuel. But you could also supply that energy via a heating element and electrical energy or a nuclear reactor. But that would be far more inefficient than driving the fan directly.

coming on here, knowing what you are talking about

[marksx]

Sireatalot said:

1.21 gigawatts. Great Scott!

I am pleased I am not the only person to have thought this!

[dvs_dave]

It's a question of being able to have an electrical storage medium sufficiently dense to do it, and electric motors that are sufficiently powerful, yet small and light enough to be feasible to mount on an aircraft. On a 777, each engine has the equivalent of about 100,000hp. There are electric motors already with that much power, but they weigh as much as a whole 777.

Until superconducting batteries/capacitors and motors are a reality, it's not going to be feasible.

[Fugazi]

Willy Nilly said:

coming on here, knowing what you are talking about

Don't worry I just pretend like I do...

[Richyboy]

Electric for air travel in our life times?

Go the other way and bring back concorde, I'm so jealous of people that flew in them.

[glazbagun]

Fugazi said:

The majority of the thrust from a high bypass ratio turbofan engine comes from the fan, with about 10% coming from the hot core engine exhaust. That fan could be driven by an electric motor and you'd see no difference in thrust as long as you provided the same power as the gas turbine. It would require a huge amount of electrical energy though and that's the problem, no current battery or power generation methods can match a kilogram of kerosene containing 43 million joules of energy, especially for aviation.

But that doesn't mean we shouldn't be working towards it. As much as I love them, and believe me I do, have been building them for twenty years, written engine simulations, designed them.... The modern gas turbine has gone about as far it's possible to go. The latest Rolls Royce turbofan engines are so close to the maximum possible thermal efficiency that huge amounts of research is being carried out to eek out a further fraction of a percent of performance. Simply put, the maximum power you can extract from a gas turbine occurs when the difference between the ambient temperature and the temperature of the flow through the turbines is at a maximum. So the turbines are having to operate in flows way above the material melting points, individual blades are grown from single crystals to ensure that they can withstand the stresses involved in high temperatures and rotational speeds, thermal ceramic coatings are required along with complex air bleed systems needed to cool each blade. The compressors are also sensitive to debris ingestion and dirt accumulation on the blades which can ruin the aerodynamic performance, fluctuating intake temperatures can also lead to compressor surging. I wrote a paper a few months ago on some of these issues surrounding maritime helicopters ingesting hot ship exhausts with subsequent drops in engine power, which has lead to numerous crashes onto offshore platforms. An electric motor would remove all these issues.

Also gas turbines (jet engines) can burn anything, diesel, oil, kerosene, wood, coal, (seriously, somebody once fueled a homebuild gas turbine with vodka, expensive way to make an expensive hobby more expensive).... All you have to do is add enough energy (heat) to the compressed air to generate enough power to drive the turbines and the easiest way to do this is with a combustible fuel. But you could also supply that energy via a heating element and electrical energy or a nuclear reactor. But that would be far more inefficient than driving the fan directly.

Laser beams!

http://uk.businessinsider.com/boeing-just-patented...

The old cancelled nuclear aircraft experiments worked on using the reactor to heat the gas in the compression chamber of a jet didn't they? They weren't electrically powered fans?

[Fugazi]

Off the top of my head I think it was called Project Pluto and involved a nuclear powered ramjet, it was unsurprisingly cancelled after some initial experiments. I think the huge amount of irradiation that would occur was one of the disadvantages . Ramjets are lovely things though, the Hiller Hornet helicopter with subsonic ramjets on the rotor blades is my favourite use of ramjet engines.