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Is A Hybrid Aircraft Possible?  
User currently offlineERJ170 From United States of America, joined Apr 2004, 6761 posts, RR: 17
Posted (9 years 1 week 4 days 15 hours ago) and read 3195 times:

Just a thought.. nothing to flame me over.. but just a thought..

Could Boeing or Embraer build a hybrid aircraft, much like Toyota or Honda does? So that it could use fuel and energy cells? I was just thinking.. it could use fuel for take-offs.. a fuel/energy cell combo during flight while the aircraft is basically flying at a somewhat level plane.. and mainly energy cell for landing? Could it be used on larger aircraft like the 737 or E-Jet family?

Thoughts?


Aiming High and going far..
29 replies: All unread, showing first 25:
 
User currently offlineSsides From United States of America, joined Feb 2001, 4059 posts, RR: 21
Reply 1, posted (9 years 1 week 4 days 15 hours ago) and read 3184 times:

It's a long ways off.

First, the technology behind an internal combustion piston engine and a jet engine are very different. As far as I know, there is no known hybrid jet technology.

Second, the current hybrid vehicles do not use fuel cells; they have a hybrid gas-electric engine. Fuel cell technology is being developed, but is still a long ways away.

Third, the sheer power required to fly an aircraft is the biggest limitation. It would take huge fuel cells to perform up to today's standards. I think you'd see a nuclear-powered aircraft first.



"Lose" is not spelled with two o's!!!!
User currently offlineCV747 From Iceland, joined Jan 2000, 170 posts, RR: 1
Reply 2, posted (9 years 1 week 4 days 15 hours ago) and read 3170 times:

From an Engineering point of view I would say it is possible. I see the main problem in the weight of the cells and the weight pennalty in a dual propulsion system. This kind of development will only get serious if the governments start investing seriously into the development of alternate power sources and not just rely on fosils.


Olafur


User currently offlineSsides From United States of America, joined Feb 2001, 4059 posts, RR: 21
Reply 3, posted (9 years 1 week 4 days 15 hours ago) and read 3160 times:

Quoting CV747 (Reply 2):
This kind of development will only get serious if the governments start investing seriously into the development of alternate power sources and not just rely on fosils.

Government support isn't necessary. If the price of oil and, correspondingly, jet fuel, continues to increase, there will be more investment.



"Lose" is not spelled with two o's!!!!
User currently offlineVirginFlyer From New Zealand, joined Sep 2000, 4537 posts, RR: 41
Reply 4, posted (9 years 1 week 4 days 15 hours ago) and read 3150 times:

How exactly would you use electricity to run a turbine engine? I honestly think the future of commercial airliner propulsion lies in bio-diesel.

I can certainly see fuel cells being an option for generating the electrical power required by an aircraft, replacing engine driven generators. I was actually under the impression Boeing were planning this for the 787, though that could have just been a concept that hasn't got beyond the drawing board yet...

V/F



"So powerful is the light of unity that it can illuminate the whole earth." - Bahá'u'lláh
User currently offlineBmacleod From Canada, joined Aug 2001, 2259 posts, RR: 0
Reply 5, posted (9 years 1 week 4 days 15 hours ago) and read 3150 times:

So what happens when oil hits $100 and then $150? Will airlines just keep increasing the fuel surcharge?

Let's face it, oil will eventually run dry so engineers have to develop an alternative powerplant to be ready befiore this happens....  scratchchin 



The engine is the heart of an airplane, but the pilot is its soul.
User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 6, posted (9 years 1 week 4 days 15 hours ago) and read 3108 times:

Quoting Bmacleod (Reply 5):
Let's face it, oil will eventually run dry

He says, typing on a computer that's burning oil.


User currently offline727200er From Canada, joined Mar 2004, 318 posts, RR: 0
Reply 7, posted (9 years 1 week 4 days 15 hours ago) and read 3098 times:

Actually Turbine based hybrid technology is quite old. Look up Turbo Train. However this technology was of course for a land bound train. There are experimental small aircraft being propelled by electric motors. I don't see electrics being able to propel large aircraft for some time if ever. Alternative fuels such as biofuel and even hydrogen are FAR more likely. One of the great things about the gas turbine engine, is that it will burn anything as fuel. I have literally seen a turbine running on coal dust. I think we will see more investigation in this area soon, as it takes quite a bit of time to begin the certification process.


"they who dream by day are cognizant of many things which escape those who dream only at night" - Edgar Allen Poe
User currently offlineERJ170 From United States of America, joined Apr 2004, 6761 posts, RR: 17
Reply 8, posted (9 years 1 week 4 days 15 hours ago) and read 3092 times:

Perhaps the true Next Generation aircraft will be a hybrid.. Otherwise, it is still the current Generation aircraft.

A composite aircraft with alternative fuel source.. that can carry between 100 and 280 passengers between 1500 nm and 8000nm and travel as high as 50,000 miles..

Perhaps using nuclear thermal or nuclear fusion/fission engine that can fit inside a current car battery size devise?

Just thoughts..



Aiming High and going far..
User currently offlinePhollingsworth From United Kingdom, joined Mar 2004, 825 posts, RR: 5
Reply 9, posted (9 years 1 week 4 days 15 hours ago) and read 3076 times:

The biggest problem with hybrid airliners is the fact that the vehicle changes from a thrust limited system to a power limited one. The thrust required to fly an airplane trends upward with the square of velocity, i.e. thurst = drag. The power trends with the cube of velocity, i.e. power = drag * velocity. This changes the way you operate vehicles. Currently, you want to fly as high and as fast as you can, keeping the proper L/D, Mach limiting. This means that your endurance is relatively constant but your range increases. In power limited systems the speed-altitude relationship changes, range is relatively constant and endurance decreases with altitude.

That and finding 20-100 MW electric motors and power converters.


User currently offlineVirginFlyer From New Zealand, joined Sep 2000, 4537 posts, RR: 41
Reply 10, posted (9 years 1 week 4 days 15 hours ago) and read 3058 times:

Quoting 727200er (Reply 7):
One of the great things about the gas turbine engine, is that it will burn anything as fuel.

Yes, they are remarkable things turbines. I'm not certain how much embellishment there is in it, but I was recently told of a private jet (I think it was a gulfstream) which was in Iraq just prior to the war. When it was obvious the war was starting, the company wanted to get the jet out. The airport refused to refuel it. The crew apparently went to the local liquor provider, and bought his whole stock... They apparently got the aircraft to europe running on a mix of vodka, wiskey, rum etc. The engines apparently ran fairly hot, and had to be rebuilt after it, but hey, it flew...

On the issue of biodiesel, I have read somewhere that if jet fuel remains over US$35 a barrell, biodiesel is economically competitive...

Quoting ERJ170 (Reply 8):
travel as high as 50,000 miles

Um, that would be twice as high as geostationary orbit, and over a fifth of the way to the moon... Perhaps you mean 50,000 feet?

V/F



"So powerful is the light of unity that it can illuminate the whole earth." - Bahá'u'lláh
User currently offline777236ER From , joined Dec 1969, posts, RR:
Reply 11, posted (9 years 1 week 4 days 14 hours ago) and read 3041 times:

Quoting VirginFlyer (Reply 10):
On the issue of biodiesel, I have read somewhere that if jet fuel remains over US$35 a barrell, biodiesel is economically competitive...

And it becomes moreso as infrastructure builds up (as it is doing). Throw in a 'green tax' that may or may not appear, and you've got a good kerosene alternative...


User currently offlinePhollingsworth From United Kingdom, joined Mar 2004, 825 posts, RR: 5
Reply 12, posted (9 years 1 week 4 days 13 hours ago) and read 3010 times:

Quoting 777236ER (Reply 11):
And it becomes moreso as infrastructure builds up (as it is doing). Throw in a 'green tax' that may or may not appear, and you've got a good kerosene alternative...

Just don't plan on using it as your sole fuel source. It makes a lot of sense as one of many alternative fuels, but you couldn't plan enough crops in the US to cover the US's current Diesel and Kerosene needs. One of the problems of fast growing, renewable crops, is that their energy density is relatively low (damn photosynthesis and keeping the planet livable). I have read that using 5-20% soy kerosene could lead to dramatic reductions in certain emissions (just not NOx).

Quoting ERJ170 (Reply 8):
Perhaps using nuclear thermal or nuclear fusion/fission engine that can fit inside a current car battery size devise?

The passengers will love this, the only way to make these small is to get rid of the shielding. This can be done to some extend for RTGs, but they don't produce much power, and one of the fusion cycles. Everything else produces neutrons and all of their associated joys.

Quoting 727200er (Reply 7):
Alternative fuels such as biofuel and even hydrogen are FAR more likely. One of the great things about the gas turbine engine, is that it will burn anything as fuel. I have literally seen a turbine running on coal dust.

Yup, you can run gas turbines on most any fuel. You just have to design them to routinely handle the fuel and deal with the associated maintenance issues. The problem with many alternative fuels is the substantial reduction in energy density without a corresponding increase in specific impulse. This hurts hydrogen, alcohols, coal, etc. Hydrogen looks the best if you get rid of drag, e.g.., upper stage engines on rockets.

Union Pacific railroad used gas-turbine locomotives in the 1950s. They burned surplus "bunker fuel" left over from WWII. The problem with this fuel is that it basically ate through the turbine blades due to all of the un-burnable particulates. This wasn't such a problem when fuel was cheap, but once the surplus ran out, the mtc. costs coupled with the gas turbines poor part power fuel consumption basically doomed them to being replaced by Diesels (which don't have the erosion problems and have better part power fuel consumption).

Just one last parting thought: There really is no such thing as an environmentally neutral form of energy. They all effect the local or global climate in some manner.


User currently offlineMrChips From Canada, joined Mar 2005, 927 posts, RR: 0
Reply 13, posted (9 years 1 week 4 days 9 hours ago) and read 2952 times:

Quoting ERJ170 (Reply 8):
Perhaps using nuclear thermal or nuclear fusion/fission engine that can fit inside a current car battery size devise?

Mr. Fusion is a long way off. With our current technology, we have yet to demonstrate a sustained fusion reaction that generates more power than is necessary to sustain it (yes I know, the governments of the world are primarily to blame for this).

As for fission, forget it...there are simply too many problems for it to be considered as a source aircraft power.

As for hybrid propulsion, I think that it is simply not possible with our current technology...using electricity in combination with conventional hydrocarbon power in an aircraft is simply not feasible, due to the huge weight penalty. However, fuel cells do show promise for light aircraft, as well as for auxillary power...in fact, these are not only feasible now, but they are cheap enough that the cost of such systems could be reasonable - it won't be as good as a conventional system, but it is getting closer every day.

As for alternative fuels, our most promising options for aviation, IMO, are as follows:

1) Ethanol-derived fuels - yep, the same corn alcohol that comes out of your stills can power a jet engine, given some modifications to the engine. Unfortunately, corn production takes up a HUGE amount of land.

2) Hydrogen - This is great...you can use electricity to break apart seawater, or alternatively, a chemical reaction to break apart natural gas (methane). Unfortunately, hydrogen has very low energy density (KJ/kg), you need to keep it under lots of pressure (heavy pressure vessels) or keep it very cold (using lots of energy), and you need lots of energy to just to make hydrogen in the first place...where is that going to come from? You might ask about safety, but I will counter with the fact that hydrogen has an undeservedly bad reputation.

3) Coal-based jet fuel - A promising alternative in which methane is combined with high-carbon coal to make a product similar to kerosene. The problem is that it has only been done on the lab bench thusfar.



Time...to un-pimp...ze auto!
User currently offlineBobster2 From , joined Dec 1969, posts, RR:
Reply 14, posted (9 years 1 week 4 days 9 hours ago) and read 2950 times:

Quoting ERJ170 (Thread starter):
hybrid aircraft

When I saw the message subject, I first assumed you were talking about a hybrid combining an airplane with a helium filled airship. A hybrid named Aereon was made famous in the book "The Deltoid Pumpkin Seed".

http://www.johnmcphee.com/deltoid.htm

Maybe you should look at that type of hybrid instead, although it hasn't been made economically feasable yet. It was intended for moving freight more than passengers.


User currently offlineKlaus From Germany, joined Jul 2001, 21442 posts, RR: 54
Reply 15, posted (9 years 1 week 4 days 6 hours ago) and read 2904 times:

The primary reasons why hybrid cars can be a good idea are:

• Better efficiency at stop-and-go than a continuously running combustion engine since electric motors have no startup penalty.

• Energy recovery by using the electric motors as braking generators, saving the energy in the battery.

• When you´re driving on the highway, a hybrid car will at one point actually become less efficient than a well-designed conventional car!

Commercial jets simply can´t use any of the advantages but would share the disadvantages of hybrid propulsion.

Beyond that, I have my doubts that even the motors alone could really compete with gas turbines of the same power/thrust class weight-wise, let alone the whole system of motors/generators/batteries.

In the long run we´ll probably see synthetic liquid fuels (not actually pure hydrogen) from renewable sources unless something really dramatic is being invented. (Hey, what about anti-gravitation? Or absolute thermo-electric conversion?  bigthumbsup  )

Even positively bizarre ideas such as silicon-based fuels have been proposed...


User currently offlineCloudy From , joined Dec 1969, posts, RR:
Reply 16, posted (9 years 1 week 3 days 21 hours ago) and read 2811 times:

Klaus is correct. Just about all of the advantage of a hybrid comes from stop and go city driving. It might be more of an advantage if you could charge the batteries from a wall outlet. This would essentially be an electric car with an auxiliary gas engine for long trips. None of the current mass market hybrids are like this. They get their energy entirely from gasoline. The only difference between them and a conventional car is that some of the energy from the gas engine and from the brakes goes to charge the electric motor. Like other alternatives to petroleum products for cars, they survive on flash and massive subsidies from governments and corporations. The price of gas has not gone nearly high enough (at least in the US) for them to survive on their own merits.

Some hybrids also "cheat" by using lighter materials than conventional cars. These materials cost more. If you look at hybrids that are converted versions of conventional cars(like the Civic) the difference is even less. It can be as little as 5 mpg even in the city. This is not much of an advantage when you consider how many complex new systems are needed, and how much more the car costs.

Much of the talk about the need to subsidize alternative fuels is based on the fallacy that the market will have no time to react if oil runs out. The market will have PLENTY of time to react. The economy will, without government meddling, produce more efficient vehicles and alternative fuels when we need them. People talk as if some day, we will suddenly wake up and find out that POOF! there is no oil. All the cars on the street will suddenly stop. There will be a new great depression, etc. This is nonsense. What will happen is that the price will slowly go up over time. We are talking decades, not years.

We know this because there are huge reserves of crude (in shale, for example) that are not economically exploitable with today's tech. As the price of oil goes up, it will become economically feasible to get to that stuff. Canada alone has huge reserves of shale oil.

The reason we are seeing higher prices now is because of politics, not because of any lack of the stuff in the ground. NIMBY's and leftist "environmental" organizations have made it nearly impossible to build any more refinery capacity the US or Europe - so there is a crunch in refining capacity. It also doesn't help that many different kinds of gas are required by different localities. Another factor is the growth of China - which is taking up much of the slack left in the system. Any alternative to oil-based fuel is likely to encounter factors like this from time to time. You cannot stop any commodity's price from fluctuating. Even if you fix the price, that will just produce a black market.

As for aircraft...... the main advantage of fossil fuels is that they have a high power/weight and power/volume ratio and they do not require much special handling. Natural gas or Hydrogen is a possibility, as is some kind of beamed electrical power. But oil would have to be OUTRAGEOUSLY expensive before these started to look good. They all have show-stopper problems. Aircraft will be the last mode of transportation to stop using fossil fuels.

IN SHORT.... There may be legitimate national security or environmental reasons to subsidize alternatives to petroleum use(though I am sceptical). But don't think we, as a society, have to find an alternative to it because we will otherwise run out. When the time comes, the alternatives will be able to win on their own merits through the market. Having government try to pick the winners now will only hurt things in the long run.


User currently offlineBoeing7E7 From , joined Dec 1969, posts, RR:
Reply 17, posted (9 years 1 week 3 days 12 hours ago) and read 2739 times:

Quoting Phollingsworth (Reply 12):
Just don't plan on using it as your sole fuel source. It makes a lot of sense as one of many alternative fuels, but you couldn't plan enough crops in the US to cover the US's current Diesel and Kerosene needs.

True, however... build a few nuke plants and eliminate fossil fuel dependence as a source for electricity generation/heat. With a strategically organized and more efficient power grid you eliminate the need for oil/natural gas in the home. This would save enough fossil fuel use to support Aviation alone. Move to Hydrogen or Electric/fuel cell Cars (about 10 years out from being able to have a full powered SUV), bio fuels for trucking, electricity for trains and the US oil supply alone would be sufficient for hundreds of years as all it would support is Aviation, by that time who knows what they'll be able to do in terms of aircraft engines and electricity. What's more, it would be cheap. Jet-A is baiscally a hybrid diesel which is less costly to produce. Much of our problem in price is production costs compounded by assinine additives which are mixed in and out every six months.

The irony is this is the likely outcome as soon as people get over the fear of a nuke plant.


User currently offlineKlaus From Germany, joined Jul 2001, 21442 posts, RR: 54
Reply 18, posted (9 years 1 week 3 days 11 hours ago) and read 2700 times:

Quoting Boeing7E7 (Reply 17):
The irony is this is the likely outcome as soon as people get over the fear of a nuke plant.

Nuclear power as an infrastructure is neither safe nor economical - that´s just another convenient but false myth.


User currently offlineBoeing7E7 From , joined Dec 1969, posts, RR:
Reply 19, posted (9 years 1 week 3 days 9 hours ago) and read 2644 times:

Quoting Klaus (Reply 18):
Nuclear power as an infrastructure is neither safe nor economical - that´s just another convenient but false myth.

Cheaper and more lifesaving than potential wars over fossil fuel in 50 or so years.


User currently offlineMrChips From Canada, joined Mar 2005, 927 posts, RR: 0
Reply 20, posted (9 years 1 week 3 days 8 hours ago) and read 2615 times:

Quoting Klaus (Reply 18):
Nuclear power as an infrastructure is neither safe nor economical - that�s just another convenient but false myth.

Oh yeah? Nuclear power IS safe and economical - if it wasn't for the NIMBYs, we might not be in the bind we have now regarding oil.

Let's look at it from a pollution perspective:

Coal - Even with gas scrubbers in place, the burning of coal releases huge amounts of carbon dioxide, nitrogen oxides and sulphur oxides. Also, most of the mercury released into the environment can be directly attributed to burning coal in power plants.

Oil/Gas - Despite the fact that these plants can be built just about anywhere for very little money, they too release lots of greenhouse gasses and acid rain forming oxides. In addition to that, with fuel prices going up every day, these plants are becoming more and more uneconomical to operate.

Wind power - Dollar for dollar, the infrastructure for wind power is by far the most expensive of any kind of power generation. This percludes the creation of any large-scale wind power plants. Not only that, but you figure that there are relatively few areas of the world where wind power can be generated economically, and the fact that wind power plants can be a considerable eyesore.

Solar power - Of course it might seem like cheap energy, but consider this - we have no effective means of harnessing it cheaply. Even the most efficient solar power projects only have an efficiency in the neighbourhood of 10%...meaning you need a large amount of surface area to generate energy. Coupled to the fact that most of the world's energy demand is during the winter in the Northern Hemisphere, where days can be very short and often cloudy, and this very quickly becomes useless.

Tidal power - Very few areas of the world are actually suited to tidal power. Also, we have not fully grasped the ecological consequences of building a tidal power station.

Hydroelectric power - This is very expensive to build, and only a few bodies of water are suitable for hydro power. Also, studies are coming out that point to hydro plants as being huge greenhouse gas emitters. How? When the reservoir for the hydro plant is built, all of the biomass underwater dies and begins to rot, releasing huge amounts of methane over the course of five to ten years.

Finally, we get to nuclear power. Granted, there have been accidents, but those can be directly attributed to a combination of poor design, operator stupidity and lack of procedural training. A properly designed reactor, such as the CANDU series, is virtually fail-safe, yet produces cheap and clean power using less costly and less radioactive unenriched fuel. Having said this, nuclear power plants still pollute, but the amount of pollution is very little - they release heat, as do all other thermal power plants, and they release nuclear waste. How do we deal with nuclear waste? Well, we don't do it right at the moment. Currently, the best way to deal with nuclear waste is to mix it with sand, melt it, and form a pellet of radioactive glass that is extremely stable, and does not allow for leaching.

Better still than making these glass pellets is to use the waste for fuel in a breeder reactor. These produce power still, and utilize the waste as fuel, continuously making more fuel for itself.

If you need an example of a nuclear success story, one must look no further than France - most of that country's electricity is generated by nuclear power, they consistently run a profit on their system, and as yet they have a perfect safety record, attributable to good training and good design of their systems.



Time...to un-pimp...ze auto!
User currently offlineKlaus From Germany, joined Jul 2001, 21442 posts, RR: 54
Reply 21, posted (9 years 1 week 3 days 6 hours ago) and read 2552 times:

Quoting MrChips (Reply 20):
If you need an example of a nuclear success story, one must look no further than France - most of that country's electricity is generated by nuclear power, they consistently run a profit on their system, and as yet they have a perfect safety record, attributable to good training and good design of their systems.

Wrong.

The french nuclear program is massively subsidized, not least for the benefit of the french nuclear weapons program, which is basically the same for most other countries: If you don´t think you "need" nuclear weapons (and thus subsidize nuclear programs from the defense budget), nuclear power is a big money loser if you consider the entire system including processing, long-term storage, cleanup, environmental damage and risk insurance (which no actual insurance company will cover fully - so it´s provided or subsidized by the state again).

France has a rather horrible processing plant in Cattenom which is known to release significant quantities of toxic nuclear waste into the sea and doesn´t have a stellar safety record. There is no viable long-term storage strategy, which basically means that the mounting waste management costs will have to be carried by the coming generations.

There are good reasons why even the power companies in Germany aren´t really keen on building new reactors even if they could - it´s simply not a profitable proposition.

Even the net power production rate is not very favourable as you´ll have to subtract all the power you´ll need for construction, management and post-processing of the entire infrastructure.

It only makes a modicum of sense if your first priority are nuclear weapons and the civilian program is basically a byproduct of that.

But we´ve discussed that aspect extensively in non-av already and we should go over there for the less aviation-related aspects of it.

Suffice it to say that there will be no easy solution; There are alternatives, but they will continue to be difficult and challenging.


User currently onlineStarlionblue From Greenland, joined Feb 2004, 17015 posts, RR: 67
Reply 22, posted (9 years 1 week 3 days 5 hours ago) and read 2542 times:

I'm all for orbital power, either solar or nuclear. If you can solve the power transfer problem (microwave beaming looks good) you have removed the polluting plants from the ecosphere (in the case of nukes) or gone up where the sun shines 24/7 (in the case of solar).

Ok, we won't be seeing this tomorrow, but...



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offline2H4 From United States of America, joined Oct 2004, 8955 posts, RR: 60
Reply 23, posted (9 years 1 week 3 days 3 hours ago) and read 2482 times:
AIRLINERS.NET CREW
DATABASE EDITOR




Quoting Klaus (Reply 15):
In the long run we´ll probably see synthetic liquid fuels (not actually pure hydrogen) from renewable sources unless something really dramatic is being invented. (Hey, what about anti-gravitation? Or absolute thermo-electric conversion?



What about ion propulsion?



...From http://science.nasa.gov/newhome/headlines/prop06apr99_2.htm:

At the rear of the chamber, a pair of metal grids is charged positively and negatively, respectively, with up to 1,280 volts of electricity. The force of this electric charge exerts a strong electrostatic pull on the xenon ions. The xenon ions shoot out the back of the engine at a speed of 100,000 km/h (60,000 mph). At full throttle, the ion engine will consume 2,500 watts of electrical power, and put out 1/50th of a pound of thrust. That's far less than the thrust of even small chemical rockets. But an ion engine can run for months or even years, and it's up to 10 times more efficient.






Obviously, it takes a tremendous amount of energy to generate a very small amount of thrust. Any chance the efficiency will be improved to usable levels? Also, is it only usable in space, or could it somehow be used in our atmosphere?

I know nothing about it....just read about it and am curious...



2H4





Intentionally Left Blank
User currently offlineKlaus From Germany, joined Jul 2001, 21442 posts, RR: 54
Reply 24, posted (9 years 1 week 3 days 1 hour ago) and read 2455 times:

As far as I´m aware, ion engines produce very little impulse but need very little fuel mass because the energy is not delivered through the fuel itself but electrically through solar panels or nuclear generators. The advantage in a no- or low-drag environment is that you don´t have to accelerate a huge amount of fuel on top of the vehicle´s own mass, but in the atmosphere (which is a high-drag environment by comparison) you´ll need high-impulse, low-speed engines for efficient propulsion instead. Mass acceleration is much less of a factor there than drag is.

25 2H4 : Thanks for the info, Klaus. 2H4
26 LeanOfPeak : What size is that, really? It looks about the size of a small-block engine, but I can't say there's a whole lot of reference for scale.
27 Post contains images PPVRA : This Crop-duster... Is powered 100% by Ethanol and is already selling like hot cakes in Brazil. Not just orders, but many farmers are modifying their
28 Post contains links PPVRA : Check out this old press release: http://www.cbc.ca/storyview/MSN/worl.../2005/03/15/Ethanoljet-050315.html
29 Post contains links and images Aviadvigatel : A converted Tupolev 154 aircraft first flew in April 1988. The centre and one outer engine used kerosene, and the other outer one, (a kuznetsoz NK-88
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