On Mon, 06 Aug 2007 00:14:14 -0700, James Sleeman
wrote in
. com:

On Aug 6, 4:52 am, Larry Dighera wrote:
Electrically Powered Ultralight Aircraft

It's a nice idea, but realisitically there are too many problems, not
the least of which is battery size, weight, cost and safety. I don't
really see batteries as a viable in the near future (I struggle to see
them as viable in the distant future either).

There is a fundamental problem with attempting to power an aircraft
with batteries: The propulsion system must not only move the vehicle
forward as it would with an automobile, but it must also
simultaneously maintain the aircraft's altitude; unlike an automobile
that only requires a small amount of energy to overcome rolling and
wind resistance once in motion, an aircraft can't coast without losing
altitude, so energy demands for powering an aircraft are considerably
more demanding than those for an automobile.

That said though, I recently saw an article somewhere about an
electric car with a stirling engine tucked away in the back (Deam
Kamen was in on it somewhere - he's the Segway and fancy wheelchair
guy).

Are external combustion engines as efficient as internal combustion
engines? Stirling engines are great for converting waste heat to
mechanical energy, but I'm not sure how appropriate they would be for
aircraft propulsion.

On the face of it, that seems like not a bad idea for how an electric
aircraft could be realistic - take your stirling engine, hook it
through a smaller, cheaper, lighter battery system to your electric
motor. The battery would act as a buffer (capacitor) to allow for
stored energy to do rapid changes in power to the drive motor, the
stirling engine would tick away at a constant rate feeding it's
generated electricy into the battery.

But then, I'm no engineer, I'm sure it's already been discounted as
impractical by the real engineers Maybe the stirling engine ends
up so big and heavy to produce the power required that it's useless.

The comparative light weight and high energy density of lithium-ion
polymer batteries makes them a potential enabling technology for
electrically powered aircraft as well as automobiles. All-electric
automobiles are entering the marketplace finally:

Our customers are a diverse group. All value the sports car
performance of zero to 60 mph in about 4 seconds and a top speed
of more than 130 mph, but many of our customers are also concerned
about the environment. Some, such as customer Stephen Casner, have
owned (and still own) older electric vehicles like Toyota's Rav 4.
(Read his Tesla Motors blog at:
http://cts.vresp.com/c/?TeslaMotors/...4be/9291be675f

Early customers include Google Co-Founders Sergey Brin and Larry
Page, actor George Clooney, comedian Jay Leno, and California
Governor Arnold Schwarzenegger. Tesla Motors continues to take
reservations for the 2008 model year Tesla Roadster at our website
at:
http://cts.vresp.com/c/?TeslaMotors/...4be/d99894a034

Tesla Motors is closing out July with another significant
milestone reached: We have now accepted more than 560 reservations
for the Tesla Roadster toward an anticipated first year production
total of 800 cars.
http://cts.vresp.com/c/?TeslaMotors/...4be/4ed5aad61f

And if this prototype is an indication, all-electric automobiles will
no longer suffer from an image of being slow and impractical:

http://www.gizmag.com/go/6104/1/
The 640 bhp MINI QED plug-in EV
(link to this article)

Page: 1 2

September 4, 2006 Q.E.D. is an abbreviation of the Latin phrase
"quod erat demonstrandum" which means, "which was to be
demonstrated". In simple terms, it indicates that something has
been definitively proven. Accordingly, the MINI QED electric
hybrid is aptly named as it dispels any doubts about the validity
of in-hub electric motors playing their part in the future of the
automobile. PML FlightLink designs and manufacture electric
motors, EV drive systems, joystick controls and controllers and
bespoke motors for specialist applications and the MINI QED was
built to showcase their expertise in wheelmotors, with a view to
supplying what we expect will be a booming market in electric
vehicle applications over coming decades.

The result is a MINI with four times the horsepower of a Cooper S,
supercar performance and the prospects of some very serious EVs in
the near future. The QED is a ripper, using four 120kW (160bhp)
wheel motors complete with invertors to convert momentum back into
stored energy under brakes. With one on each corner you have
Ferrari-like power and very controllable independent drive on all
four wheels.

In the MINI QED, this package offers a 0-60mph time of 3.7 seconds
and a 150mph top speed – supercar territory. An on-board petrol
engined generator offers enough electrons to run continuously at
motorway speeds without depleting the battery, and you can plug it
in at night and commute in full electric mode if you wish.

As the invertor can exert more retardation than brakes, the
conventional disc brakes have been discarded altogether.

The inwheel motors and magnesium alloy wheels, and tyres, have a
total mass of 24kg. The original assembly mass on the MINI One was
22.5kg. With so little difference in unsprung mass (the brake
hubs and discs have been removed), and full regenerative braking,
the ride is claimed to be no different.

More importantly, it means dynamic management of up to 750Nm
torque at each wheel, (3000Nm total) in either direction, to
ensure optimum use of available power. The system can also use
steering (driver intent and wheel alignment) and vehicle attitude
(gyroscopic sensors read pitch, roll and yaw) as inputs to the
traction control and vehicle stability systems. Put simply, the
vehicle stability system will be the key, and it will ultimately
be the software that determines what the optimum tractive
distribution will be at each instant - how the energy stored in
the 300V 70Amp Hour (700Amp peak) Lithium Polymer battery is most
effectively distributed.

...continued: http://www.pmlflightlink.com/archive/news_mini.html

So it would appear that high-performance all-electric automobiles are
viable and in fact being produced commercially now. And while there
have been some successful electrically powered, unmanned aircraft
demonstrated, such as those of Dr. Paul MacCready's AeroVironment:

http://www.avinc.com/uav_lab_project_detail.php?id=40
Pathfinder flew to 50,567 feet at Edwards September 12, 1995, its
first trip to the stratosphere. From there, it was improved and
taken to the Pacific Missile Range Facility (PMRF), Kauai, Hawaii
for test flights in 1997, where it flew to 71,504 feet on July 7,
before performing a series of science missions over the Hawaiian
Islands.

http://www.avinc.com/uas_dev_project_detail.php?id=115
Global Observer is the latest development in High Altitude Long
Endurance (HALE) UAS, being the first operational configuration
able to provide long-dwell stratospheric capability with global
range and no latitude restrictions. Global Observer's unique
combination of both extreme flight duration and stratospheric
operating altitude is designed to deliver advantages in cost,
capacity, coverage, flexibility, and reliability that make it a
compelling complement to existing satellite, aerial and
terrestrial assets.

Missions Communications Relay & Remote Sensing
Features High-Altitude, Long-Endurance platform (all latitude
capability)
Endurance/Range Over 1 week/global
Payload Up to 400 lbs. for GO-1 & 1,000 lbs for GO-2
Operating Altitude 65,000 feet
Expected Availability Within 2 years for U.S. government, with
funding

There are also manned, commercially produced, electrically powered
sailplanes available in the marketplace:


http://www.lange-flugzeugbau.de/htm/...tares_20E.html
Antares 20E

http://lange-flugzeugbau.com/pdf/new...%20issue01.pdf
Today Lange Flugzeugbau received the EASA type certification for
the Antares 20E. (EASA TCDS No. A.092). This is the first time in
the world that an aircraft with an electrical propulsion system
receives a type certificate.
http://www.nadler.com/public/Antares.html


http://www.dg-flugzeugbau.de/elektroflieger-e.html
DG-800E the uncompromised Motor glider with Electro-Power?


Here's a little history:

http://www.solarimpulse.com/the-hist...tion-en20.html
Solar aviation began with reduced models in the 1970s, when
affordable solar cells appeared on the market. But it was not
until 1980 that the first human flights were realised. In the
United States, Paul MacCready's team developed the Gossamer
Penguin, which opened up the way for the Solar Challenger. This
aircraft, with a maximum power of 2.5 kW, succeeded in crossing
the Channel in 1981 and in quick succession covered distances of
several hundred kilometres with an endurance of several hours. In
Europe, during this time, Günter Rochelt was making his first
flights with the Solair 1 fitted with 2500 photovoltaic cells,
allowing the generation of a maximum power of 2.2kW.

In 1990, the American Eric Raymond crossed the United States with
Sunseeker in 21 stages over almost two months. The longest lap was
400 kilometres. The Sunseeker was a solar motor bike-sail plane
with a smoothness of 30 for a tare weight of 89 kg and was
equipped with solar cells of amorphous silicon.

In the middle of the 1990s, several airplanes were built to
participate in the "Berblinger" competition. The aim was to be
able to go up to an altitude of 450m with the aid of batteries and
to maintain a horizontal flight with the power of at least 500W/m2
of solar energy, which corresponds to about half of the power
emitted by the sun at midday on the equator. The prize was won in
1996 by Professeur Voit-Nitschmann's team of Stuttgart University,
with Icare 2 (25 meters wingspan with a surface of 26 m2 of solar
cells.)
http://www.solarimpulse.com/the-solar-impulse-en5.html


And here's a glimpse at the futu

http://www.boeing.com/news/releases/...70327e_pr.html
MADRID, March 27, 2007 -- In an effort to develop environmentally
progressive technologies for aerospace applications, Boeing
researchers and industry partners throughout Europe plan to
conduct experimental flight tests in 2007 of a manned airplane
powered only by a fuel cell and lightweight batteries.

The Boeing Fuel Cell Demonstrator Airplane uses a Proton Exchange
Membrane (PEM) fuel cell/lithium-ion battery hybrid system to
power an electric motor, which is coupled to a conventional
propeller. The fuel cell provides all power for the cruise phase
of flight.

During takeoff and climb, the flight segment that requires the
most power, the system draws on lightweight lithium-ion batteries.
(Boeing graphic)



Photo of Sonex e-flight electric aircraft's electric power plant:

http://www.sonexaircraft.com/news/im...light_5947.jpg


More info:
http://en.wikipedia.org/wiki/Electric_airplane