back to article NASA working on 'open rotor' green (but loud) jets

NASA and General Electric have teamed up with French industry to revive a type of fuel-efficient aircraft engine shelved in the 1980s, in an effort to tackle aviation carbon emissions and high fuel costs. The "open rotor" engines, despite their relatively green characteristics, will still be unpopular with many anti-aviation …


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  1. Anonymous Coward
    Anonymous Coward

    Catapult launch.

    Save loads of take off fuel (thus making the plane lighter as well) and potentially much quieter from lower take off thrust.

    Could be leccy as well so powered by lambs gambolling in fields or something.

  2. Matt Vernon 1
    Black Helicopters

    wouldn't it be possible

    to have both types of engine on the bigger planes? ie normal engines for take off / landing / flying over inhabited areas and then these for when you're flying over the atlantic where there aren't too many people to worry about the noise?

  3. The BigYin
    IT Angle

    But, but, but....

    ....jet planes are more efficient and green that trains. El Reg said so!

    So why are NASA wasting their time on this?

  4. A B 3
    Black Helicopters

    Use Air

    Combine it with tip jet technology.

    See YouTube vid of tip jet helicopter here:

    That BH is awfully quiet.

  5. Anonymous Coward

    A Title

    seems counter intuitive that more loss of energy as noise = better efficiency.

  6. James Hughes 1


    Some sort of hybrid perhaps - only engage the open rotor fans when out of earshot?

    Not sure the engine would then have enough power to take off of course...

  7. Andy 97

    You can't win

    If it's green - it's too noisy and people who *chose to live under the flight path* complain.

    If it's quiet - it burns more fuel and people who know have no ideas about the real world complain.

    Seems like an impasse..... of course until someone perfects the 'whisper mode' as featured on the helicopter (we are lead to believe that flew) on Airwolf.

  8. Anonymous Coward
    Anonymous Coward


    The other drawback of contra-rotating open rotors is that the engines look *really scary*

  9. Paul Tubing
    Paris Hilton

    also lethal

    These engines were primarily abandoned because of the risk of a blade detaching and penetrating the cabin, with the remaining off balance engine vibrating the structure to failure. More, smaller blades within a nacelle are significantly safer.

    Paris - b/c it vibrates, and costs a lot.

  10. Carl 1

    Whisper Mode?

    Blue Thunder surely, not Airwolf?

  11. Mike Richards Silver badge

    You just know... of those is going to play a prominent part in ending the career of a movie supervillain.

  12. BoldMan
    Black Helicopters

    @A B 3

    Tip jet helicopters are not new, check out this vid of the Fairey Rotodyne as built in the UK in the 60s but was scrapped for various political reasons (TSR2 anybody?)


    Fantastic bit of engineering!

  13. Spaz

    The Russians already did it first.

    Nothing to see here the Russians did it in the Cold war:

    This thing is fast, loud and efficient. Good old communist engineering.

    It is so loud that the americans could hear it approaching and not have to look at the radar.

  14. Fred 4
    Black Helicopters

    How about...

    a retractable (define in your own meaning) cowling over the blades??

    the cowling extends covering the blades - hence reducing noise - during landing and take off. Then retracts during flight to improve efficiency.

    The cowl might be able to be some lightweight plastic so that there are not huge weight penalties for carrying the cowl around, and possibly less worry that if the cowl breaks the fans blades would not be heavily damaged (?).

    black helicopters - what else would need to be silent :)

  15. breakfast

    Catapult launch?

    Surely we could just build enormous lamb-powered catapults to fling planes across their entire journey?

  16. Anonymous Coward
    Anonymous Coward

    @Fred 4

    Re-read the article. The proposed engine does not have a cowling because the blades are "so long that it would no longer be practical to fully enclose them and hang them beneath an airliner's wing".

    The cowling was not removed due to efficiency (as you suggest), but for practicality. If one could be built and attached, there would be no benefit to making it retractable.

  17. Anonymous Coward

    What open rotor designs need

    Is a way to feather the open rotors during low altitude & take-offs & landings, and to engage the open rotors when far enough off the ground to meet noise restrictions.

  18. Anonymous Coward
    Anonymous Coward

    Catapult launch?

    Shh.. there'll be none left for kebabs.

    >seems counter intuitive that more loss of energy as noise = better efficiency.

    There's heat too.

  19. RRRoamer

    Still going about this the wrong way...

    Vacuum tubes...

    Decades ago they demonstrated that a mag lev train in a vacuum tube (aka: REALLY long tunnel!) wold allow you to send a person from New York to Miami for the energy equivalent of a gallon of gas.

    Given that it would take my car about 45 gallons to do the same, that's not bad.

    You would also be able to make that trip in less than one hour. It would accelerate half the trip and decelerate the other half. The infrastructure would be expensive to build, but if they just built tunnels between major metropolitan areas, it would still replace over half the commercial air traffic (if not more) that we have today. It would also be zero carbon (assuming nuclear, solar or other "green" power technology) as the system it electric.

  20. Nexox Enigma


    It's a reasonably well-known fact that with the current combustion temperatures capable in turbine engines (limited by turbine blade materials) you can't get much more than 20-30% efficiency (Fuel energy to mechanical energy.) That's straight up thermodynamics, which I tend to trust. So when people claim a 25% fuel savings boost over whatever we've got now... I just don't quite see it. There's no change to the thermodynamic cycle, except minor temperature and pressure adjustments at each stage, derived from the new aerodynamics. Unless current engines are just wasting a fantastic amount of energy pressuring up the engine itseld... Well I'll believe it when I see it I suppose.

    And as for blades falling off... Same danger as your standard turbo-prop. Consider that if there are counter-rotating blades on a turbine, which typically has a single shaft, turning in all the same direction, then you have to assume the presence of gears. And that means that the outer blades can turn a whole lot slower than the turbine itself.

    Also, am I the only one that totally can't picture in my head an aerocraft with 2-4 of these things strapped on? Do the blades go behind the wing? Surely they're large enough that they can't just fit under the wing, right? How about mounting these on a flying wing / lifting body, which I swear was the ultimate flight solution last I checked.

    Whomever asked about multiple types of engines: That'd be expensive, and not many people will be interested in that sort of price for the sake of saving some fuel. It's got to make econonic sence before airlines will go for it.

  21. Anonymous Coward

    @Catapult launch?

    No, all the lambs are busy betting - online gambolling...

  22. Anonymous Coward
    Thumb Down


    ``And with recent research indicating that railways can actually hurt the environment more per passenger mile than airliners, flying less could even be a retrograde step in ecological terms''.

    And thus, a new, and disingenuous meme is born... Can't wait to see this repeated endlessly in the usual places, by the usual gang of idiots.

  23. Anonymous Coward

    shanks pony anyone?

    fuels itself, just it park in a field overnight.

    green emissions.... well sorta green, at least digested green stuff...

    spade and bucket only tools needed for carbon capture, and by products are resellable at profit.

    no road tax :)

    but low mph and even lower hp...

    ideal for short run abouts down to the shops...

  24. Anonymous Coward
    Anonymous Coward

    I like the idea of catapults!

    a set of linear induction motors of suitable size and these open rotor engines may well be substantially more efficient? Beefed up landing gear. Watch the lights dim all around Thiefrow as a plane takes off. Need the normal engines for those "backwoods" airports like Gatwick were the technology would be to expensive and complicated. The main energy consumption would be in take off. once the plane has reached programmed take-off speed then carriages can slow down and return down a service track. They did it for Fireball XL5 so why not?

  25. Steven Jones

    Peope no anti-aviation campaigners...

    "will still be unpopular with many anti-aviation campaigners as they are significantly noisier than ordinary turbofans."

    Have you ever thought that they might just be unpopular with people who happen to live near airports rather than your bogey men of "anti-aviation campaigners".

    Not that this technology is exactly new - it has been talked about for years, but the problems of noise and not being able to contain disintegrating blade parts have been stumbling blocks.

    These may be a bit more efficient than Turbofans, but that's more an issue of cost rather than, in the big picture, a huge contribution to reducing CO2 emissions.

  26. James Woods


    Andy 97, one things for sure, the 'flight plans' wouldn't be in the areas of the greenie weenies. The flight plans would be where low income people that can't afford to live anywhere else would be.

    You would never see anything like this near any of the global warming kooks, they don't want to have to pay price for being green, they just want to force things on others while having nothing to do with any of the repercussions.

    Just look at the Kennedy Windfarms, oh wait they don't want those noisy windmills up there, they want them in your backyard instead.

  27. Anonymous Coward
    Anonymous Coward

    @shanks pony anyone?

    Your feet give off green emissions?

    (You do know that the phrase "get there by Shanks Mare" or "Shanks Pony" refers to walking, and not the use of a four-legged mammal with a tail?)

  28. Anonymous Bosch

    Bird Strikes anyone?

    All they have to do is sharpen the fan blades.....

  29. MD Rackham

    Blades behind wing?

    Seems like the counter-rotating blades would have to be behind the wing. I thought there were serious problems with pusher props at higher speeds?

    The air coming off the top of the wing is moving at a different speed than that coming off the bottom. The blades would have to slice through both layers, causing changes in the stresses on the blades at a rather high rate, depending on rotational speed of course.

    The original Northrop prop-driven flying wing turned out to be impractical for this reason as I recall.

    But then I hope that NASA, GE, and SNECMA have more knowledge of practical aerodynamics than I do, and that it isn't just a way to get grant money.

  30. A B 3
    Thumb Up

    Re: Disintegrating blade parts

    You could mount them aft of the tailrudder on a pylon.

    You could also put in fairings to channel the sound in one direction, i.e aftwards.

  31. Grease Monkey Silver badge

    Already Green

    Planes are already pretty green. A fully loaded passenger jet uses less fuel per passenger mile than the average car journey. The best way of making air travel green is to make sure that the planes are always fully loaded.

  32. Alan_Peery

    Noisy -- OK for smaller airports

    It may be non-intuitive, but using this engine only between smaller airports would make sense. If you're only impacted a couple of times a day by the noise, it's not really a problem. Where you don't want these planes is any airport with a large number of flights.

    Why do I think I have a right to say this? I live near Heathrow, and Concorde used to fly overhead... ;-)

  33. Anonymous Coward
    Anonymous Coward

    Aircraft design

    Easy way to deal with the oversized blade issue and the noise issue is to change the aircraft design.

    Don't put the engines on the wing - instead stick them where the tailfin currently is with a double tailfin that effectively means that the engines are enclosed underneath by the plane's body and on each side by a tailfin. Most of the noise is therefore forced upwards and thus away from people who are likely to moan about it!

  34. William Clark

    Passenger miles per gallon

    I read in the 70s that typical passenger miles per gallon were:

    Car:- 150 (I guess 4 passegners - 35-40 mpg)

    Jet airliner: - 90 - i guess a full 490 seat Jumbo - I am not sue how man of these there are.

    Diesel Train:- 800 - I presume this is also full, and I suspect that an empty passenger train uses only a little less fuel than a full one - I'd bet tube trains vary more full vs empty while express trains vary little.

    I also suspect that the figures should be revised for modern transport. Some modern cars are getting much better mpg and I do not know the quoted figures for more recent airliners. I suspect trains are much the same as man can go faster but probably return the same pmpg.

    (Imp gallons used here)

  35. Anonymous Coward


    Given that those space shuttles that haven't blown up are getting on for 30 years old, shouldn't Nasa be working on a space ship instead of a plane? Or are they booking their astronauts on Virgin Galactic?

  36. Adrian Esdaile
    Thumb Up

    Give aircraft noise moaners iPhones...

    ...with the volume set permanently to '11'. Solved!

    They won't hear the aircraft, and after a month or two, won't even need to use the iPhone! Result!

    Funny how you never hear aircraft noise protestors protesting about diesel engines - how else could they drive Portia & Xander to school without their freakin noisy, black soot-belching urban monsta-trucks.

  37. Cortland Richmond

    Loud? YOU WANT LOUD?

    Look no further than the Republic Aviation XF-84H, nicknamed (not by Republic) the "Thunderscreech."

    A development of the F-84F fighter, reports have it so noisy one pilot refused to fly it twice, and it was decided to tow the aircraft to the flight line with engine stopped, because of the effect its noise had on humans.

    A fair comparison of airliner noise might be made between jet aircraft and aircraft of the same weight, size and passenger capacity but with piston engines. Anyone know how much noise a Brabazon made? It's useful , to bear in mind that noise reducing techniques have improved.

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