Boeing Working on Fuel Cell Aircraft 163
"Boeing is working with development partners on a fuel cell-based small aircraft. It seems like a logical use of the technology. Now if they can come up with a quiet, personal-sized VTOL craft a la Paul Moller's Skycar (which is anything but quiet), we'll really have something." From the article "A Boeing research director was quoted as saying, "While Boeing does not envision that fuel cells will provide primary power for future commercial passenger airplanes, demonstrations like this help pave the way for potentially using this technology in small manned and unmanned air vehicles."
Re:Reliability? (Score:3, Informative)
The Wankel engines are much smaller and lighter for the same horsepower than piston engines. Their drawback for automobiles is similar to turbines - they don't like low RPMS (the rotor seals leak at low RPMS causing wasted fuel, seal wear, and pollution). This is not a drawback for aviation.
Of course, this design requires fly by wire computer control for everything, and you don't want your computer to fail (although the parachute could be manually deployed).
ha ha (Score:4, Informative)
You probably mean the external combustion engine, also known as the jet engine. Only small airplanes use pistons and such. And the answer is: of course not. This is yet another PR stunt aimed at the Gasoline Is Eeeeeeevil ninnies of the world who failed freshman chemistry.
If not, what about fuel cell powered dirigibles?
I don't think the problem with dirigibles is how to power them. I think the problem is that there's just about zero demand for a transport service that's about as slow as a ship or train but neither as efficient nor as reliable.
A big cargo ship carrying 70,000 tons of cargo can cruise at 15 knots with its 50,000 HP engines running at 80%. The EPA helpfully estimates [epa.gov] big marine engine fuel consumption as about 250 grams per kilowatt-hour, which lets you work out that a cargo ship consumes about 4 grams of fuel per ton of cargo per kilometer traveled.
Four locomotives pulling a hundred-car freight train at 60-80 MPH, with each car carrying 100 tons of cargo, will burn about 7.5 gallons [bts.gov] each per mile. That works out to 7 grams of fuel per ton of cargo per kilometer traveled.
There's no way any vehicle that flies can ever come close to that kind of fuel efficiency. So who would want cargo delivery that's just as slow, but much more expensive?
Re:More kinetic energy is bad (Score:3, Informative)
Given the relation p = m v, you do the math on that, and couple it with the fact that no non-military building I know of is built to withstand impacts from above. Anyone in a home or apartment that's hit by a falling, fast-moving aircraft is dead meat.
Re:time to educate the masses again... (Score:4, Informative)
Sounds like someone failed basic understanding-of-how-things-work class.
Oh I agree, definitely.
Somebody failed looking at pictures class. The combustion chamber in a jet engine is quite definitely in the middle of the engine. Combustion takes place inside the engine, between the compressor and the turbine.
Not all ICEs have pistons, nor are all piston engines ICEs.
Re:Use a compressor (Score:2, Informative)
Re:time to educate the masses again... (Score:2, Informative)
Your analogy is faulty; if you indeed look at "the nice picture" in the article you linked, you'll notice that the combustion actually takes place in the combustion chamber, between the compressor and turbine stages; the exhaust stream is produced as a result of this combustion. Furthermore, the article you linked to was for a turbojet engine, which is nothing but a sub-class of the jet engine.
A jet engine [wikipedia.org] does not specify that the energy source must be an internal combustion engine [wikipedia.org]; it only specifies that thrust is generated in one direction by expelling a fluid (usually air/exhaust or water) in the opposite direction. Having said that, most common jet engines do use internal combustion. It is simply a matter of type.
A common example of a jet engine that uses a reciprocating internal combustion engine (typically two- or four-stroke) for power can be found in Sea-Doos [wikipedia.org], where a standard reciprocating internal combustion engine (like you would find in most automobiles) is used to drive an impeller that expels a jet of high-pressure water rearward of the craft, propelling the craft forward.
A common example of a jet engine that uses a continuous flow internal combustion engine is a turbojet [wikipedia.org] engine, commonly found on military aircraft, or turbofan [wikipedia.org] engine, commonly found on commercial passenger aircraft. Both turbojet and turbofan engines share a similar design in that the incoming air is pressurized using a compressor, mixed with fuel and combusted in the combustion chamber, and then expelled rearward of the craft for thrust. In this exhaust stream you will find a gas turbine that is used to power the compressor. In the case of turbofan engines, this gas turbine will also power a large fan located at the engine intake, which is where the majority of the thrust in a standard commercial jet-engine comes from.
The important thing to note is that reciprocating and continuous flow engines are both types of internal combustion engines; the public is just used to thinking of the ICE as a two- or four-stroke cycle system using pistons and a crankshaft, which is just not true. The combustion chamber in a turbojet or turbofan (or turboprop, now that I think about it) engine is still a confined-space combustion chamber used to burn air mixed with fuel at high pressures.
While I'm sure that looking at pretty pictures helps grade-schoolers learn "the way of things", typically it is considered good practice to read up on a subject before putting someone else down about not understanding it.
And in case you were wondering, I am a 4th year Aerospace Engineering student at the University of Toronto. While I don't claim to know everything there is to know in the world of combustion engines, I have had a fair amount of exposure both from private study and from experts and researchers in the field.
Aikon-
p.s. No, Wikipedia [wikipedia.org] is not a reference I would ever cite in a research paper, though in this area its information is pretty good. I link to it only because it offers a great overall explanation of the processes involved. If you are sufficiently interested I suspect you will be able to get your hands on some real study material that goes into much more detail.
Re:ha ha (Score:3, Informative)
Re:Skycar (Score:3, Informative)
Like so many other things in the health and fitness industry, nobody wants to look for the shades of gray or give people answers that they don't want to hear. For example: To lose fat weight, you must eat less (fewer calories) and exercise more. That's it. No fancy diets, no Atkins bullshit, no seaweed wraps, vibrating belts or other crap. BMI is a classic example of that. It's a number that is easily compared to an arbitrary scale, with math that isn't hard enough to make Joe Sixpack's eyes glaze over. The effort involved in body composition testing (Dunk tank best, caliper measure less so but more convenient, circumference measurement about the same, body conductivity most convenient but least accurate) is too great for most people to even consider unless they're forced.
There's more to measuring appropriate weight than height vs. weight. But like so many other things, nobody wants to hear that. And there's no money in telling people what they don't want to hear, so you'll never hear the fitness media conglomerate talk about it.
(I have a degree in exercise science, but work in tech because I refuse to work in an industry that I've found to be based on scams and diet pills.)