Slashdot Mirror
NASA Designs All-Electric Personal Flight Vehicle
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."
Well, let's see...
FTFA:
[...] the Puffin can cruise at 240 kilometers per hour [...] With current state-of-the-art batteries, it has a range of just 80 kilometers if cruising [...]
So it can stay up about 20 minutes.
It would work for me. I could get to work in about 15 minutes and plug it in. At the end of the day, it's all charged up and I take it home.
So, yes. I want one.
The other factor is that the typical propeller does become less efficient as the air gets thinner, so there is still a ceiling. Jets (turbofans) have less of an issue with this. From a quick Google, It appears that above Flight Level 240 (24000) the majority of the thrust of a turbofan comes from the jet exhaust, while at sea level most of it comes from the fan.
For me, the sheer fear factor of looking down from 9000 meters (30,000 feet) in not much more than my flight suit would be more than I'd be ready for.
But I think this could be the inspiration for the long-awaited personal aerial commuter vehicle - especially if operation can be automated, and if the redundancy mentioned in TFA can achieve no-single-point-of-failure. If routing were handled by a central traffic control system, and local traffic position were handled by an agent swarm, it could work pretty well. The VTOL capabiliy means you could land in a parking space, or on the roof. And the 80 mile cruising range would be sufficient for commuting.
It's easier to be a result of the past, but more fun to be a cause of the future! http://www.spacefinancegroup.com/
Not in any way, shape, or form. Getting to 20-30000 feet, if it was capable of that, with a very small payload, it essentially worthless in terms of orbital. To get into orbit the chief challenge is velocity. To get that (without other far more interesting technical breakthroughs) you need a HUGE rocket with very large amounts of fuel. So there is really no role at all for this teeny little helicoper/VTOL airplane.
Brett
I'm not implying they could get into orbit with this vehicle as it obviously will require atmosphere for the rotor blades to be effective, but in a general sense. Specifically getting a launch vehicle as far into the atmosphere as possible before switching to a different means of propulsion like a typical rocket.
Achieving orbit is about speed ('delta v'), NOT altitude. It takes much more energy to get the horizontal speed to the required level than to reach the required altitude. Getting above the atmosphere helps, but not all that much.
Your about 10,000 feet off.
Class "A" Airspace begins at FL180 (18,000 ft AMSL) and continues up to FL600 (60,000ft AMSL). AMSL = "Above Mean Sea Level"
To fly in class "A" airspace you must be following a filed IFR Flight Plan and have two way radio communication. These are the only requirements.
There is one instance where one is required to fly VFR in class "A" airspace. Look it up! I will give you a hint: FAR part 91 and AIM 6-x-x
yes I am a pilot.
Hey KID! Yeah you, get the fuck off my lawn!
At those altitudes, wouldn't the fact that the air be EXTREMELY cold? (I think -52c or so at 30k feet?)
The problem is that air is far less dense at those altitudes. There's roughly a third the air at sea level. For example, suppose you're trying to keep the engine below 80C. An air flow at sea level and 20C that barely does it, would be equivalent to a third the airflow at -100C.
From a quick Google, It appears that above Flight Level 240 (24000) the majority of the thrust of a turbofan comes from the jet exhaust, while at sea level most of it comes from the fan.
While possibly true in practice, it has nothing to do with altitude. Thrust comes from the mass flow rate, times the change in velocity. Aside from fighter jets on afterburner, the exhaust coming out of a jet engine will be subsonic. The speed of sound is proportional to the square root of temperature, so the hot core flow will be much faster than the relatively cool bypass flow.
So what relevance is this to anything? By 'sea level' the quote you saw probably meant 'take off', or zero forward velocity. FL240 would be cruise at 500-550 knots. You have high mass flow but low velocity through the bypass fan, and high velocity but low mass flow through the core. At cruise speed, the velocity differential of the bypass flow may only be 1/4 what it was static, while the much hotter and faster core flow still has more than half its differential. Modern high bypass turbofans have ratios of 9:1 or better, so the bypass will still be producing more thrust than the core even at the reduced efficiency.
Well Everest is just under 9km up, and people have scaled it without oxygen. However these were mountaineers, and not duty free guzzling pilots.
Also that's a totally different scenario. High altitudes like that without oxygen while mountain climbing are achievable only by letting the body acclimatize for several weeks at progressively higher altitudes during the climb.
You take anyone at sea level and put them immediately at 9km up without oxygen, they will pass out within minutes.