I came across this concept aircraft. How realistic is this design?
I have taken a quick look at the promotional material and while it is obviously dumbed down, it still contains enough jargon and acronyms to make it impossible for me to make any kind of assessment. Radical shape change, 12 engines, using H2 as a fuel and a coolant, radical change to engine design, superconductors used liberally.
Given that the aircraft industry is (rightfully) conservative, how likely is it that any of this concept design is (a) feasible, (b) likely to be developed further and (c) will ever make its way into common use?
I know that jets have been trending to higher and higher bypass designs, so I guess the next logical step if you don’t want to go back to/continue with a turbo fan design is a hybrid type approach like they’ve outlined. Although if it were that simple, you’d think that would have been done already so there must be issues with it. Maybe that’s why there’s an emphasis on superconducting electric engines.
I couldn’t really tell if it was a lifting body design, but if it is, having a solid row of air intakes at the rear should do a nice job of reducing drag.
There’s something vaguely … familiar … about that plane.
bump
I was hoping one of our aviation experts would check in. Maybe after the weekend.
J.
i) The shape makes a lot of sense from aerodynamic POW, however, most passengers are some way from the nearest door/window. This may slow down boarding and it would definitely slow down evacuation. Also, unlike current designs, the aircraft would be difficult to scale up/down to build a range of different sizes (like Airbus did with 318/319/320/321). It is certain to see more development, perhaps a business jet in late 2020s, regional airliner in 2040s, and boeing/airbus wide-body in 2050s?
ii) Superconductors are absolutely necessary for a turbo-electric setup in a commercial jet. With them, the power-plant is about the same weight as an equivalent turbofan. Without them, it would be 3-4x heavier. I haven’t heard much about superconducting motors/generators recently, so 2040+ would be my guess.
iii) Liquid hydrogen is a great fuel per unit of mass and absolutely awful per unit of volume. This is already a problem for fuel-cell powered cars. Perhaps the aerodynamic improvements can reduce the fuel consumption far enough? LNG might be a more practical alternative, especially if you also need to cool superconductors. Storage is another issue. Liquid hydrogen tank boils off about 1% of its content per hour to keep its cool. This is not a big issue for an aircraft that needs to fly 5-10 hours. However, it is a big issue for the airport that needs to store thousands of tons of fuel.
IMHO, something like biodiesel/ethanol is the future of aviation. Small modifications to existing jet engines may allow them to burn both kerosene and the new fuel. This would greatly simplify the transition. You would fill up with whatever the airport has in store. Just imagine the headache of trying to convince 100s of cash-strapped international airports to build liquid hydrogen storage/fueling facilities because you may want to use them 10 years from now.
Out of curiosity, I checked wikipedia for the current state of the art in hydrogen storage since i had recalled something about metal hydrides. It appears that this line of research continues apace along with several other promising avenues such as metal-organic frameworks and clathate hydrates.
The weight of an insulated fuel tank that can hold liquid hydrogen for a couple of hours is about 5-10% of the mass of fuel inside it. This has been driven down by advances in rocketry, the space shuttle in particular. However, the fuel tank is still very bulky because liquid hydrogen is 14x less dense than water. Hydrogen under high pressure has the same issues. [EDIT: bulk in an aircraft means drag!]
The above approaches try to store hydrogen in some matrix which would allow for higher density. However, the matrix itself adds mass. For example, hydrides consists of only 10% hydrogen. This means that weight of the fuel tank would be about 900% of the hydrogen being stored inside it. This does not matter for cars or stationary storage. Who cares if your car’s fuel tank is 20kg or 200kg when full. The important thing is that it fits somewhere out of sight. However, fuel is up 40% of aircraft’s take-off weight.
A quick look at the specific heating values will show that you need 33% hydrogen content to match kerosene’s energy density and 21% to match ethanol. AFAIK, none of the proposed technologies can achieve this even in theory, much less in practice. As long as there is a reasonably affordable supply of any hydrocarbon fuel, liquid hydrogen in aircraft is about as practical as solar cells.
If anything, a far-future carbon-neutral world might just manufacture hydrocarbons from scratch for the few cases where heavier-than-air flight is necessary. Use your fusion power plants on the ground to convert ambient carbon dioxide and water into hexane or whatever, then pour that into the plane’s fuel tanks. Of course, you’d want to replace airplanes with high-speed trains or boats whenever possible, so you don’t have to do much of this.
Unfortunately, trains and boats are not a replacement for heavier-than-air craft, and barring science-fantastical anti-gravity technology so some system of producing a workable propellant/fuel will be necessary. Hydrogen is problematic for all of the reasons previously mentioned, and even using proposed hydride storage methods doesn’t get to within a half an order of magnitude of the density of hydrocarbons, so some kind of synthetic hydrocarbon production will likely be necessary.
[POST=414318]Here[/POST] is an old thread on blended wing body (and flying wing) aircraft for commercial application, and some of the problems associated with it. There is no technical reason that it is completely infeasible, but it would require both substantial investment in novel technologies and a concurrent change in infrastructure, which the highly conservative commercial aircraft industry is notoriously unwilling to engage in. So the answer to the o.p. is:
[LIST=A]
[li]probably technically feasible given sufficient development[/li][li]will require substantial motivation (in the form of government/industry research, change in regulations, et cetera) to become viable versus tube-and-wing forms[/li][li]would require decades to overcome the inherently conservative attitudes of the commercial aircraft industry[/li][/LIST]
Stranger
There’s also the small matter that all existing commercial airports would have to be changed. A plane that wide wouldn’t fit at the gate structure of existing airports.
J.
I was trying to visualise the centre of lift and the centre of gravity. It seems to me that the plane in the pic would tip forward. And this would be made worse by having the jets on the top surface of the plane. Now I know that such things can be rectified by wing design and angling the exhaust gas flow and I also recognise that my estimates may be way off. However it seemed to me to be a counter-intuitive arrangement.
As my id suggests i live under the flight path of the listed facility on the pdf.
I would estimate the time of publication is the time of flight testing for the only time I witnessed the nx3 fly over. I would also guess that the data was accurate to the flight.
CLE airport has made the appropriate modifications to fit this plane. I am guessing at the numbers but i would estimate 300m wide with wings out and that it was close to 100m nose to tail. I can only estimate the speed at 25 to 30 miles out from the airport to be well under 200 mph and the elevation was below a very rainy cloud deck. I have heard it fly over a few times since. It has a very low pitch wine explaining the electric generators and electric motors.
I am so glad they have finally released the so called concept photos but examine well because this is a real photo of the bird in flight. It definitely has the 14 engine configuration. I could not hear the blower engines at all over the generators.
http://event.arc.nasa.gov/Green-Aviation/home/pdf/TurboElectric_GreenAviationWorkshopPresentation_04_25_2009.pdf
I would guess at least 100 passengers were on board the passenger deck in white suits meandering around the plane. I was out in my yard and as it broke the cloud deck behind me i did not ever hear it until it was almost directly over my shoulder.
She was very low, low enough for me to see the passengers wandering around. they killed the interior lights soon after breaking cloud deck. I was seriously concerned until I realized it had to be a NASA project and it was not alien. It only took about 15 seconds. Then i just stood and looked for any details i cloud get.
The bottom is the grey you see on the sides and the proportions were inconceivable until I was able to see the picture. what date was this picture (yes picture) released?
100m x300m it was huge.