NASA Designs All-Electric Personal Flight Vehicle 276
MikeChino writes "NASA is currently working on a personal aircraft that will put jet packs to shame. The Puffin is an all-electric one-man airplane that could be the start of some new and amazing air travel technology. With two prop electric engines, lithium phosphate batteries and a top speed of almost 300 mph, the vertical take off and landing vehicle was originally designed for covert military insertions because it has a lower heat signature than combustion engines. The Puffin would also be super quiet – 10 times quieter than current low-noise helicopters, and since the engine is electric it has no flight ceiling and can fly up to 9,150 meters high, uninhibited by thin air."
"No flight ceiling" (Score:5, Interesting)
Re:"No flight ceiling" (Score:5, Interesting)
I'm not an engineer so I can't comment on the operating ceiling of the the thing but speaking as a former private pilot, 9,150 meters (FL 28, roughly) is already well above the point where the pilot-in-command would be allowed to operate without supplemental oxygen.In fact, up that high you'd be messing with the three-holer transport jets and would probably need a pretty high-quality heated flight suit.
Comment removed (Score:4, Interesting)
Re:thin air? (Score:5, Interesting)
Note well that the highest flying prop plane ever, the Aerovironment Helios [wikipedia.org], flew to 96,000 ft -- far higher than almost any other plane (probably the only one that could sustain that altitude was the SR-71). The Helios was powered completely by solar cells and electric motors.
Innumeracy? (Score:3, Interesting)
From TFA:
electric aircraft are much quieter than regular planes—at some 150 meters, it is as loud as 50 decibels, or roughly the volume of a conversation, making it roughly 10 times quieter than current low-noise helicopters.
I admit that I never have gotten a handle on math beyond algebra but am I wrong by being bothered by statements like 10 times quieter? Wouldn't be better to say "makes only one-tenth the noise?" Or am I being pedantic?
Re:"No flight ceiling" (Score:2, Interesting)
Well Everest is just under 9km up, and people have scaled it without oxygen. However these were mountaineers, and not duty free guzzling pilots.
I also am completely unqualified in aerodynamics, but I would assume (most probably incorrectly) that the ceiling would be limited by the speed the rotors turn and also the length/surface area they have (assuming the pilot is appropriately dressed for the occasion).
I'm quite interested actually in any responses that could shed some light on this... seems pretty cool.
On a side note, we had here (in Australia) on "The New Inventors" some dudes that actually made a battery powered helicopter. It was kind of like a gyrocopter - pretty light weight 1 seater kind of thing. It had a pretty shitty filght time, on the order of minutes, but obviously they only used bog standard batteries (ie they didn't develop any special batteries or anything, "just" hooked them up to a motor and modified the gyro).
For those not familiar, the show basically has random people that have invented something come and show it to a panel, and they decide on a winner each week. It's pretty cool, you get anything from automatic sheep tilters(yes, that) to stuff that automatically re-sheaths pneumatic hoses. Riveting stuff :) .
Battery powered aircraft:Completely unrealistic (Score:4, Interesting)
Li-ion-anything has an energy density equaling 1% of gasoline. Lithium phosphate batteries are worse than others in energy density, but safer.
So for the same fuel weight, instead of a 2 hour flight reserve, you would have 72 seconds.
Until there is a radically different battery, this is unrealistic.
Re:"No flight ceiling" (Score:1, Interesting)
My point was not the time it takes to get up there, more the fact that people can actually breathe up there, but only though training and acclimatisation. I believe it only takes a few minutes for hypoxia to set in. At those altitudes, even feeling lightly unwell can have deadly repercussions.
Re:"No flight ceiling" (Score:3, Interesting)
Most of a ~200 mile commercial flight is spent ascending and descending. Not so much time spent at cruising altitude. Props are significantly more efficient at low altitudes, compared to turbofans. Recall that we are talking about turbine engines in both cases! The 'burn fuel in air' part of the engine is *exactly* the same. The efficiency comes down to the type of blades you're spinning - a few very long unenclosed blades work great -- right up until you have to spin the blades so fast that the Mach-effects of one blade start interfering with the air around the next blade. The fan in the turbofan uses a bunch of smaller blades designed to avoid Mach-effects of this nature. So when those effects start to come into play you see the efficiency of turbofans stay the same (basically) while the efficiency (and eventually capability, if you keep climbing) of the turboprop plummets.
Of course there's all sorts of craziness regarding gear ratios and a bazillion other things that I completely ignored here. But as a high level overview, it's not worthless.
If you can do VTOL, you design for sea level -- a huge portion of your fuel/energy tends to go into getting you up and down. So how high can you CRUISE on a prop designed for optimal performance at sea level? At a guess, closer to 5km/12k feet than to 10km/33K feet, driven by the weight-cost of pressurizing the beast. But there are a bunch of variables:
- What speed do you want to cruise at?
- What is your range? Is it WORTH getting to 30k (40k, 50k, 12k) feet, only to start descending as soon as you do?
- How much can you feather your prop blades? (Change their pitch, letting you spin the blade faster at high altitudes while decreasing blade turbulence)
- What is your L/D? (Lift to drag ratio) At sea-level, your optimal speed may be 200mph. At 30K feet you have to go 300mph for the same amount of lift. Lift to drag ratio tells you that the amount of energy required to overcome that induced drag is the same for 200 mph and sea level as it is for 300mph and 30K feet.
(But that doesn't take prop drag into account. If your prop flies apart because you have to turn it at 20K rpm to stay in the air at 30K feet, all bets are off.)
- more and more, and weather, and a lot about temperature, and how much does it cost to pressurize the cabin, etc).
As for ultimate limits, the difference between stalling and breaking the sound barrier was about 50 knots for the U2 flights. That may have been plus or minus 50', but I think it was actually +/-25. Memory fails. Anyway, 68K feet is a *seriously* nerve-wracking place to fly if your airplane can't do Mach.
The F-15 managed a zoom-climb 'somewhere in the region of' 70K (I've seen 80k cited) feet. That is 'go as fast as you can at the highest altitude that your engines stay lit, and then dive, to go even faster. Then, at a very exact point determined by guys with slide rules, kick on the after-burners and start climbing at a particular angle. Then your engines burn out, then you coast. If you are in the united states and flying an F15, you launch a missile that destroys a satellite. Then plummet back to earth completely out of control, because there is no air going across your control surfaces. And hope you don't enter at the wrong angle, because there are ways you can come back to earth which would preclude you re-lighting your engines in time to save the plane. Nobody WANTS to eject.'
Re:"No flight ceiling" (Score:5, Interesting)
Ask the fucking craziest of them all, http://en.wikipedia.org/wiki/Joseph_Kittinger [wikipedia.org] .
Personal experience is as good as it gets...
"Capt. Joe W. Kittinger achieved the highest and longest (14 min) parachute jump in history on August 16, 1960 as part of a United States Air Force program testing high-altitude escape systems. Wearing a pressure suit, Capt. Kittinger ascended for an hour and a half in an open gondola attached to a balloon to an altitude of 102,800 feet (31,330 m), where he then jumped. The fall lasted 4 minutes and 36 seconds, during which Capt. Kittinger reached speeds of 1142 km/h (714 mph) [9]. The air in the upper atmosphere is less dense and thus leads to lower air-resistance and a much higher terminal velocity."
Gives the phrase "No Fear" a whole new meaning.
Capt. 'Cannonballs' Kittinger (Score:4, Interesting)
Wow! And I thought I was nuts for loving HALO[High Altitude, Low Opening] jumps!
[With full equipment/kit load+body wt. @ around 275 lb./125 Kg] I was told that the max. velocity was around 130 mph/209 kph...compared to 714 mph, I guess I was a piker!
Offtopic side note:The highest we ever jumped from was around 17,000 feet altitude; I found my minimum altitude for releasing my chute was approximately 385 feet, but it hurt!
(we were advised that the minimum altitude was 500 feet...I had to test this)
[using the US Army version of the Ram Air-square type 'chute [wikipedia.org]]
That was also where I got over my fear of heights, once I was thrown out of a perfectly good airplane!
Re:And we'll never be allowed to have one (Score:2, Interesting)
The politicians would never allow common people to have that much freedom. No borders, no passports, no way of stopping people from going where they wanted, when they wanted. And that's without assuming any purpose more nefarious than a cheap weekend in Amsterdam.
I wonder if there was someone a hundret years ago, who said something like this about cars.... I think, if you put some technology into those thing - most of the problems you adress could be solved. Could be some kind of electronically "check-in" when entering special areas or such... come on... I realy _want_ this :-)
Re:"No flight ceiling" (Score:3, Interesting)
Hmm. Interesting point. Also, to some extent I think it is a matter of choice. I never had issues with height when I was a kid - climbed 200 ft. fir trees like a monkey, used to hang out in the top and read books. More recently I've had issues. But then I bought a sailboat. It took me a while to get myself to start climbing the mast but once I got up there (65+feet above ground at the time) and started appreciating the view, the fear went away. I still respect the height but I don't seem to have the fear like I used to. So in part maybe it's a mental habit.
Re:psst, NASA, just one little thing. (Score:1, Interesting)
It would if the charge logic had additional data lines to communicate if some of the lithium cells had been disabled.
This is the current problem with consumer electronics, is that the charge logic does not convey to the device that it has disabled some of the cells for safety reasons, and that thus, your 5000mAh battery is really only a 3200mAh battery. Thus, the device presumes it has more power remaining than it actually has.
If the charge logic properly reported what kind of cell it was attached to, how many cells were functional, and what the charge states were of those cells, it would result in a more or less accurate (to within a minute or so) of the actual charge time remaining.
The problem is that charge logic of that kind would increase the weight of the battery, increase the complexity of the battery, and increase the cost of the battery. All three things are subjects that consumer electronics bean counters dont want to even consider doing unless absolutely necessary.
Considering that this is being engineered for military purposes, I'd expect much better charge logic to be installed, and for the battery meter to be more accurate than the one for your 3oz cellphone.