Forgot your password?
typodupeerror
Transportation Earth NASA Technology

Boeing's Hybrid Electric Airliner of the Future 152

Posted by Soulskill
from the flying-rice-burner dept.
fergus07 writes "Borne out of the same NASA research program that gave birth to MIT's D 'double bubble,' Boeing's Subsonic Ultra Green Aircraft Research (SUGAR) Volt concept is a twin-engine aircraft design notable for its trussed, elongated wings and electric battery gas turbine hybrid propulsion system — a system designed to reduce fuel burn by more than 70 percent and total energy use by 55 percent. The goal of the NASA supersonic research program is to find aircraft designs that will significantly reduce noise, nitrogen oxide emissions, fuel burn and air traffic congestion by the year 2035."
This discussion has been archived. No new comments can be posted.

Boeing's Hybrid Electric Airliner of the Future

Comments Filter:
  • Always 25 years (Score:3, Insightful)

    by sakdoctor (1087155) on Monday August 02, 2010 @05:24PM (#33116074) Homepage

    All the coolest technology is always now()+25 years away.

    • That's because most people have no idea how cool the now technology is. The Internet is absolutely amazing on pretty much every technological level, and yet to 95% of the world, its technology is indistinguishable from the magic of a radio.

      • Re:Always 25 years (Score:5, Insightful)

        by EdZ (755139) on Monday August 02, 2010 @05:48PM (#33116436)
        A few month ago, I sat in a pub watching (live) an Astronaut operating on the internals of the Hubble Space Telescope. On my phone.
        We live in the goddamn future!
        • Re:Always 25 years (Score:5, Interesting)

          by mangu (126918) on Monday August 02, 2010 @06:46PM (#33117212)

          A few month ago, I sat in a pub watching (live) an Astronaut operating on the internals of the Hubble Space Telescope. On my phone.
          We live in te goddamn future!

          Your future is happening 40 years after I sat at my home watching (live) an Astronaut walking on the Moon.

          I would gladly exchange all the cellphones in the world for being able to walk on the moon.

          • Re: (Score:2, Insightful)

            by Anonymous Coward

            I would gladly exchange all the cellphones in the world for being able to walk on the moon.

            You know, I'm thinking that the ability for *anyone* to communicate instantly with *anyone else* in the world by voice or text (or for a few, video) with just a tiny box about the size and shape of a "communicator" from Star Trek from—get this—40 years ago, is probably better than sitting at home watching on TV a couple of other guys bounce around hitting golf balls on a cold, dead rock that offers us no immediate chance for advancement beyond the psychological thrill of saying "someone else oth

          • The ability of a private person to go to space is getting better. Not worse... In a manner of speaking.

            The problem with the moon shot is that it was little more than a pissing contest with pork. Just like NASAs constellation, its not the path to the stars for joe anybody. So unless all you want to do is watch a special few do "future" things, it was and still is a bad metric to use. Just like the stupid phrase.."if they can put a man on the moon....."

            Compare that with how often the average person flew
    • Re: (Score:2, Insightful)

      by Anonymous Coward
      so currently, the coolest technology is 2035 years away? way to show off programming in communication.
    • Re:Always 25 years (Score:4, Insightful)

      by AdmiralXyz (1378985) on Monday August 02, 2010 @05:50PM (#33116482)
      This story is somewhat of a dupe (too lazy to look up the original, though it was less than a year ago), and this point was brought up then too.

      When you're talking about advanced aircraft, the "25 years effect" is not the same as it is for overhyped things like fusion power; here, there's actually a reason. Aircraft take a loooooooong time to go from concept to flight: recall that Airbus starting thinking about the A380 in 1988, made it an official project in 1994, and it started commercial flight in 2007. And that's for a conservative design that was just building on existing principles. For a radical, untested design it would be considerably longer. Looking at it from that point of view, 2035 is actually a very reasonable target.
      • Re: (Score:3, Insightful)

        by kestasjk (933987) *
        Yeah there's no good reason fusion power is taking such a long time to develop, not like there's an immensely powerful magnet, extremely rare fuel and an immense neutron flux to try and contain..
        • by hitmark (640295)

          the issue is not fusion itself, but a fusion reactor that produce more output then the input needed to maintain fusion.

    • Re: (Score:3, Informative)

      by PopeRatzo (965947) *

      All the coolest technology is always now()+25 years away.

      No, the coolest technology is now being used by off-the-books military "black" ops and weapons programs. It's always +25 years away for the rest of us, though.

      I remember back in the 70's when people were being ridiculed for reporting sightings of large triangular craft which were very quiet and flew low over ranches out West.

      Of course, they were stealth aircraft, which were being used in all sorts of black bag missions overseas. Today, it's probably

      • by dave420 (699308)
        You are not a very rational person by nature, are you?
    • by evilviper (135110)

      All the coolest technology is always now()+25 years away.

      Of course it is. Once it's just around the corner, it's boring, since you've seen every tiny step leading up to it.

      Meanwhile, these days, I can just go out and buy an electric car...

    • by mbourgon (186257)

      When I first read about e-ink it was about 5 years away. That was the case from 1995-2001 or so.

  • Supersonic?!? (Score:2, Interesting)

    I thought the British and the French proved that to be unprofitable?

    The other planes....I just imagined the airline packing those suckers and having more than one middle seat. And you know they'll be charging extra for the window or the isle seat.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      Actually Concord was generating 25% of BOAC's profits.

      • by Moofie (22272)

        Operationally. The program overall never covered its costs. Developing airplanes costs a lot of money.

    • Re: (Score:3, Insightful)

      by NeutronCowboy (896098)

      The first car was unprofitable. The first version of the Internet was unprofitable. The first everything is generally unprofitable. Reduce fuel costs by about 50%, reduce sonic boom to match federal guidelines for land crossing, and you have a profitable supersonic airplane.

      • Re: (Score:3, Informative)

        by MBCook (132727)

        Don't forget, the Concord was '70s technology. Even 90s technology could have done better.

        The thing wasn't cheap, but there was no other option on Earth. There simply wasn't (and isn't) a way to get between NY and London faster. You can't buy a supersonic jet, and the military won't let you borrow one.

        • by EdZ (755139)

          You can't buy a supersonic jet

          There are one or two supersonic business jets, but they're so expensive (about as expensive as buying an ex-mil supersonic jet and getting it refurbished to the required standard) that "you can't buy one" essentially still applies.

          • by c6gunner (950153)

            There aren't any. Various manufacturers have looked at making them, and some may eventually be produced, but as of now there are no supersonic business jets on the market.

        • Re: (Score:3, Funny)

          by tehcyder (746570)

          You can't buy a supersonic jet, and the military won't let you borrow one.

          Supersonic jets want to be free, so if you got you hands on one, it wouldn't be stealing. I think.

      • by GooberToo (74388)

        reduce sonic boom to match federal guidelines for land crossing

        Currently, federal guidelines are mutually exclusive to any aircraft which breaks the sound barrier. This is something current aerospace biggies have repeatedly pointed out. We already have designs which can satisfy all reasonable super sonic noise demands. Meaning, you *might* occasionally hear a very distant boom but you would never have the associated window shaking.

        Besides, most (all?) studies indicate the vast majority of complaints associated with sonic booms never actually existed. More often than no

        • by Jeng (926980)

          If true then the lobbyists should have no problems changing the regulations.

          Since it hasn't been done either it is not that simple of an issue, or no one has put forth the money to have the regulation changed.

          I'm sure once an aerospace firm has a design in testing the regulations will be changed.

          • by GooberToo (74388)

            If true then the lobbyists should have no problems changing the regulations.

            They were actually well on their way of addressing it when super sonic transports were all but canceled because of fuel economics. So until economics make it politically viable to address it again, I don't expect it will change.

      • by drsquare (530038)

        So the Concorde was uneconomical when fuel was much cheaper, so all we have to do is make fuel half a cheap as it is now, even though it's only going to get more expensive in the future? American guidelines have nothing to do with it, the point of supersonic travel is transoceanic.

    • by h4rr4r (612664)

      Only when you can't fly it overland at top speed. Plus have to deal with a nose that dips to land and a bunch of other stuff that was neat in the 60s but crap today.

  • Obvious question (Score:3, Interesting)

    by Ryvar (122400) on Monday August 02, 2010 @05:26PM (#33116116) Homepage

    You say you want to save massive amounts of energy, and then you show me a design that is not a flying wing. Slashdot, you have some aerospace engineers lying around, so help me out: what gives?

    • Re:Obvious question (Score:4, Informative)

      by GooberToo (74388) on Monday August 02, 2010 @05:38PM (#33116292)

      Flying wings have many excellent characteristics but mass passenger transport isn't one of them.

      In order to accommodate large passenger loads the flying wing shape becomes abused which leaves behind many of the characteristics which make the flying wing attractive in the first place. Once you modify the flying wing shape to accommodate large passenger loads, you more or less have a shape which is portrayed in the designs presented. And once you accommodate construction/materials issues, it almost exactly looks like the designs presented.

      In other words, I'm not really seeing a problem. But, as you mention, hopefully some designers won't be silent.

      • Another problem is turning. Right now sitting close to the center of gravity, when a plane turns you travel a few feet up or down. If you were sitting 20 or 30 feet from the center of gravity, you would travel much further. Most people would feel very uncomfortable doing this. Pilots would have to perform only flat turns, using the rudders. I don't know how practical this would be.

        • by Zerth (26112)

          Another problem is turning. Right now sitting close to the center of gravity, when a plane turns you travel a few feet up or down. If you were sitting 20 or 30 feet from the center of gravity, you would travel much further.

          I'd pay extra for a seat further out. Assuming I don't have the flu or something, that would be fun.

          Alas, my wife would insist on the CoG rows.

    • by Jeng (926980)

      I am no aerospace engineer, about as far from it as you can get, but I would think that wing = drag.

      Yes, some drag is needed for lift, but can you fit enough passengers in just a wing and then can you fit that wing on a runway?

      • Re:Obvious question (Score:4, Interesting)

        by magarity (164372) on Monday August 02, 2010 @06:40PM (#33117114)

        I am no aerospace engineer, about as far from it as you can get, but I would think that wing = drag.
         
        Congrats on accidentally making the wrongest statement ever on /. On an airplane, wing = lift. And since the purpose of the airplane is to go up, lift = good. The part the people sit in, that uniform shaped tube body, equals drag. An airplane shaped like a big wing could thus lift the most and drag the least. (see: Northrop YB-49)
         
        A tube body can actually produce some lift if it's shaped correctly but it's very expensive to manufacture and tricky to design (see: Super Constellation).

        • Re: (Score:2, Informative)

          by ogmundur (954110)
          Actually lift also causes drag, so called induced drag; Wikipedia article here: http://en.wikipedia.org/wiki/Induced_drag [wikipedia.org]
          • by magarity (164372)

            Well, duh, induced drag IS lift; and it's pretty clear from context this is NOT the type of drag the GP was talking about.

            • by Jeng (926980)

              No it was what I was talking about. It was pretty clear, but somehow you missed it.

            • by Moofie (22272)

              Well, on the free body diagrams I drew in my flight dynamics classes, Jeng is more right than you are.

              Induced drag is the component of the lift vector that opposes the thrust vector. Induced drag is a component of the net drag on the airframe. It's not generally useful to think of induced drag as a part of the lift force.

              You can draw your vectors however you want, but nitpicking other peoples' coordinate systems doesn't make you look like you know what you're talking about.

    • Re: (Score:3, Informative)

      by h4rr4r (612664)

      Passengers like pressurized cabins, tubes are easy to build and keep pressurized. Complex shapes are not easy to build if you want to keep them pressurized.

      • Re: (Score:3, Informative)

        by cynyr (703126)

        it's not a huge pressure differential. Less than a few feet of water in reality.

        • Re: (Score:2, Informative)

          by Pla123 (855814)

          You realize that "just a few feet of water" is more like 22 feet (7.5m) of water.
          At 35000 feet (10.5 km) cruising altitude for non-super sonic airplanes, air density is 25% of see level air density. 1 atmosphere is about the pressure of 10m of water column.
          Everest is "just" 8848 m, and yet very few can breathe easily without several days acclimatization.
          See altitude sickness. Even oxygen masks may not be enough at very low pressures.

          • Re: (Score:2, Informative)

            by dziban303 (540095)
            While I don't refute your point, Pla123, I feel I should point out that passenger aircraft are not pressurized to sea level pressure. I believe--and no, it isn't fact, but I bet it's pretty close--that airliners are pressurized to ~7000 feet above sea level. What is that, like, 800mb? Anyway, there it is.
            • You are right on. Wikipedia confirms this:

              http://en.wikipedia.org/wiki/Cabin_pressurization [wikipedia.org]

              Although to be honest, altitudes around 7,000' aren't that bad. I've been in aircraft with the doors open above 15,000' without noticing anything except my ears popping. I'm not sure I could comfortably jog at that altitude but then again that's not something you typically do on an airplane.

              I've spent countless hours on military cargo aircraft (that were sealed like a screen door), flying at cruising altitude, without

              • by bertok (226922)

                You are right on. Wikipedia confirms this:

                http://en.wikipedia.org/wiki/Cabin_pressurization [wikipedia.org]

                Although to be honest, altitudes around 7,000' aren't that bad. I've been in aircraft with the doors open above 15,000' without noticing anything except my ears popping. I'm not sure I could comfortably jog at that altitude but then again that's not something you typically do on an airplane.

                I've spent countless hours on military cargo aircraft (that were sealed like a screen door), flying at cruising altitude, without noticing anything. The only weird part is walking around a compartment that's twice as big as my house and few miles over the atlantic.

                -b

                That's coz you're a healthy young chap.

                Last flight I was on, I was sitting next to some old ladies, and several of them mentioned that they needed oxygen on longer trips after we saw an anaemic young girl faint. Her lips were blue!

                Low partial pressures of oxygen are hell on people who's lungs are already borderline capable of keeping them alive at sea level.

        • by DieByWire (744043)

          it's not a huge pressure differential. Less than a few feet of water in reality.

          Between 8 and 9 psi, typically. Almost 20 feet of water. It's not such a big deal when the structure is circular since the stress is all tension. Much tougher when you try to build large, flat surfaces.

        • by Moofie (22272)

          Yeah, and how big of a pressure vessel are you talking about? The strength of the pressure vessel does not depend only on the pressure differential, but also on the volume enclosed.

          It's harder than you think it is.

    • by EdZ (755139)
      To fit passengers comfortable into the wing, it needs to be a goddamn big wing. A wing that big could only be used on the most mass of the mass transit routes to be economical, would be expensive to develop, and would require airports to be rebuilt to accommodate them at the terminals (real deal-killer).
      Like any cool new thing, it's legacy compatibility that scuppers it.
      • Re:Obvious question (Score:5, Interesting)

        by dziban303 (540095) <dziban303@NoSpaM.gmail.com> on Monday August 02, 2010 @06:09PM (#33116752) Homepage
        Another problem with a flying wing passenger aircraft is the fact that there won't be many, if any, window seats. Okay, minor problem? What about the forces that would act on people towards the wingtips when banking? A relatively minor turn that would barely be noticed in a tubular airframe would be magnified into a fifteen foot drop or rise towards the edges. Now imagine trying to land in turbulent, stormy weather, and being really far from the center axis of the aircraft. Whatever money would be saved by the efficient wing design would be eaten up by barf bags and steam cleanings of the cabin after every flight.
        • Re: (Score:3, Interesting)

          by khallow (566160)

          A relatively minor turn that would barely be noticed in a tubular airframe would be magnified into a fifteen foot drop or rise towards the edges.

          Why do you think it'd feel like a 15 foot drop or rise? I doubt it would, if the turn were done smoothly. From what I'm reading, roll control (the control of rotation of the axis along the direction of travel) is not a serious issue with flying wings. That seems to indicate to me that the issue of storms and such (most which wouldn't generate a significant rolling motion in the vehicle) is a bit exaggerated.

          • by dziban303 (540095)

            Why do you think it'd feel like a 15 foot drop or rise? I doubt it would, if the turn were done smoothly. From what I'm reading, roll control (the control of rotation of the axis along the direction of travel) is not a serious issue with flying wings. That seems to indicate to me that the issue of storms and such (most which wouldn't generate a significant rolling motion in the vehicle) is a bit exaggerated.

            I didn't say it'd feel like, I said it would be. Obviously I have no way of knowing how many flights you've been on, but, next time you're on one, look out the window from right after takeoff until about fifteen minutes into the flight. Do the same thing at the end of the flight. Watch the wingtips in comparison to level reference, the ground or horizon or clouds. Note how the plane has to bank rather frequently after takeoff and before landing. Note how the wingtips of your plane go up and down several fee

  • For the pictures, it looks like the subsonic airplane is equipped with turboprop engines - or are these propfans ? If so, our next generations airliners might very well be equipped with propellers again: Airbus is also considering propfans [espacenet.com].
    • by h4rr4r (612664)

      Read the article, it seems to indicate that gas turbines are used to generate power which then powers electric motors that spin props. This would get you around lots of propfan issues.

      I base this on the following from the article:
      which includes an electric battery gas turbine hybrid propulsion system

      • I'm very surprised that a turbine driving an generator, powering an electric motor driving a fan is more efficient (including the extra weight) than a turbine directly driving the fan. Airliners usually cruise at altitudes where the engines are run at near max-efficiency power (at that altitude).

        • by dave420 (699308)
          Maybe because the bits of the journey that aren't at cruising altitude use up a disproportionate amount of fuel, and the inherent qualities of electric propulsion means it might be better suited to the job?
    • Re:Props (Score:4, Interesting)

      by Marillion (33728) <ericbardesNO@SPAMgmail.com> on Monday August 02, 2010 @06:19PM (#33116858)
      Jet engines are already de-facto propeller engines. If you call it a "Fan" it doesn't sound as scary as "Propeller." In a high bypass turbofan engine such as those found in most modern aircraft, most of the thrust is produced by the fan part of the turbofan. For example, the CF-34 [wikipedia.org] jet engine has a bypass ratio of 80% or better. This means 80% of the thrust is produced by spinning a fan. Newer designs like the Rolls-Royce Trent 800 [wikipedia.org] get 84% thrust from the bypass fan. Basically, anything that can create radial motion can be use to turn that fan. Electric, steam, compressed air, .... {insert physics here}.
      • by h4rr4r (612664)

        http://en.wikipedia.org/wiki/Propfan [wikipedia.org]

        This takes that idea to the next level.

      • Re:Props (Score:4, Informative)

        by icegreentea (974342) on Monday August 02, 2010 @08:01PM (#33117952)
        The bypass ratio refers to the mass of air moved around the core to the mass moved through the core, not the ratio of thrust. For any given mass of air being put through the core, it will produce more thrust than the same ratio outside the core because it gets hotter/faster.
        • by Marillion (33728)
          I'm not really able to challenge your statement. I will, however, cite that years ago I read one the pilot manuals for the Bombardier CL-65 (aka Canadair Regional Jet) which uses CF-34 engines. The manual did indicate that 80% of the thrust came from bypass air. Manuals prepared by the manufacturer do seem reasonably authoritative. If that figure is wrong, I'm merely repeating a wrong.
      • Re: (Score:3, Interesting)

        by jbengt (874751)
        Jet engines are, by definition, not fans. They produce thrust by the acceleration of a jet of combustion products exiting the rear of the engine through a nozzle. Rockets are jet engines; but the term jet engine usually implies air-breathing and rockets are assumed to carry their own oxidizer. Propellers/fans produce thrust pushing air back by rotation of the fan blades/fan wheels/propellers .
        Fans can be propellers or otherwise. When talking about aircraft it's usually meant that a prop is un-ducted bu
  • Boeing's Subsonic Ultra Green Aircraft Research (SUGAR) Volt concept is a twin-engine aircraft design notable for its trussed, elongated wings and electric battery gas turbine hybrid propulsion system

    I think they just should have tried a less ambitious project, like building a Flying Car, instead.

    "Ultra Green?" So what's the superlative for that? "Giga Green?" "iGreen?" Or what?

  • by bill_mcgonigle (4333) * on Monday August 02, 2010 @05:41PM (#33116332) Homepage Journal

    I had 'jet fuel' as on my list of things that wouldn't ever likely get replaced with electric storage, and now this reduces the list a bit. Can we just start putting up some modern nuclear reactors and get out of the Middle East then? We've got plenty of sources here for real oil needs.

    No one has died of a radiation-related accident in the history of the U.S. civilian nuclear reactor program. [washingtonpost.com] but 10,000 or so Americans have died so far as a result of making war in the Middle East. [icasualties.org]

    • Re: (Score:3, Informative)

      by h4rr4r (612664)

      Plastics and lube can be made from plant materials, or hell with enough power you can make all the hydrocarbons you want from water and air.

      • by LoRdTAW (99712)

        Close. The Fischer-Tropsch process uses hydrogen and carbon monoxide (CO) and the catalyst used in reactors can be from cobalt, iron, ruthenium and nickel. Synthesis gas or water gas is another source of H2 and CO. It is derived by passing steam over a bed of red hot hydrocarbon fuel such as coke. The result is a CO and hydrogen mix. Biomass can also be used to produce CO as well (and possibly syn-gas.) So in theory we can produce carbon neutral hydrocarbon fuels from biomass and hydrogen from water. Plus y

    • Brilliant! Absolutely brilliant! The folks in the US got their drawers in a knot, when the Concorde wanted to fly over, "because it was too loud." What do you think they will say, when they have a Hiroshima or Nagasaki flying over their heads?

      Everyone can stomach a nuclear submarine or aircraft carrier, because, well, they aren't going to dock in their backyard. (Apologies to the folks in Groton, Norfolk, and San Diego). If an accident happens, only a few whales, and other sea critters will be harmed.

      • by rsborg (111459)

        Brilliant! Absolutely brilliant! The folks in the US got their drawers in a knot, when the Concorde wanted to fly over, "because it was too loud." What do you think they will say, when they have a Hiroshima or Nagasaki flying over their heads?

        Stop getting your panties all bunched up... You do realize that the comment you're replying to talked about "electric storage"? Noone is gung-ho about flying nuclear ('cept maybe Emmet "Doc" Brown)... but if you can generate electrical via Nuclear (and Wind/Solar) and

      • by Moofie (22272)

        Hey! You forgot Everett, WA! USS Abraham Lincoln hangs out here sometimes.

    • Re: (Score:3, Informative)

      by jonbryce (703250)

      These things are still going to be carrying oil of some description rather than charged up batteries for most of their energy requirements. The additional weight of batteries is not going to make sense for an aircraft.

  • So what is the advantage of a hybrid plane? Unless there has been some sort of breakthrough in battery technology, the extra weight your carrying around is going to use more energy. A discharged battery is not substantially lighter than a full one, whereas with liquid fuel tanks weigh a lot less when (nearly ) empty..

    I guess you can get a bit of energy back on landing with regenerative braking, but not enough to make up for the extra weight.

  • Battery weight could certainly be an issue. I suppose though that you could start off fully charged on the ground and use that for a boost to get you aloft.

    Something that comes to mind is that, AFAIK, in a hybrid system you try to keep the combustion engine turning at it's ideal RPM regardless of load. Assuming that's the case, would there be periods where you might have extra capacity beyond what's needed for the electric motors and other electrical systems? Let's assume there is - what do you do with i

  • Not to be pedantic, but... OK, I'll be pedantic.

    The long tube supporting the wing (on the ground) is called a strut, not a truss.

    What surprises people is that the strut actually holds the wing down in flight. Saves you the weight of designing for massive bending moments at the fuselage at the expense of more drag in flight.

    That was the trade off the Gossamer Condor made to become the first human powered aircraft to pass whatever milestone it did - rather than take the weight associated with an internally br

  • "The goal of the NASA supersonic research program is to find aircraft designs that will significantly reduce noise, nitrogen oxide emissions, fuel burn and air traffic congestion by the year 2035."

    Reduce air traffic congestion?

    What? Are they solar powered and only fly on the sunny side o' Earth?

    The article mentioned both air-speed decreases and fueling/loading times lowered. Both of those mean more airtime, which in turn means more planes in the air at any given time. How does that equate to "reduced air t

    • by Moofie (22272)

      NASA is taking an integrated approach to the problem. By carefully scheduling arrivals and departures to minimize loitering, you reduce fuel burn. You have to be clever in how you control aircraft that fly closer to one another than they're allowed to today. It's a complex problem.

  • by Solandri (704621) on Monday August 02, 2010 @11:42PM (#33119430)
    The press release is devoid of details, but a google search turns up that they're decoupling the jet engine (which generates the power) from the bypass fan (which generates most of the thrust) [aviationweek.com].

    For those not up to speed on jet engine technology, modern turbofans are essentially ducted propellers [wikipedia.org]. The engine itself occupies a small section in the center. It burns fuel and throws the air it consumes out the back at a higher speed. This generates about 20% of the total thrust. The rest of the energy goes into spinning the bypass fan blades. Just like a propeller, they grab large chunks of air which never goes through the combustion chamber, and push it out the back at higher speed to generate about 80% of the thrust.

    In current engine designs, the blades of the two are locked together (although some of the compressor blades inside the engine may rotate at a different speed). For the bypass fan blades to be spinning, the engine must also be on and spinning. The idea behind this hybrid is to decouple them so they can operate independently of each other. The bypass fan would be spun using an electric motor. I don't know the numbers involved, but theoretically that would mean you could always run the jet engine at its most efficient RPM to generate electricity, and even turn it off if there's little thrust required and the batteries have enough juice to run the bypass fan (e.g. descent).
  • Do the math: It is far faster, more energy efficient and easy on the environment, to fly out of the atmosphere in a suborbital trajectory, reentering near your destination. Oh, but we have to wait for NASA to develop that and they are mothballing the shuttle program so it must be a non-starter. Right?

"Out of register space (ugh)" -- vi

Working...