Electrically Powered Ultralight Aircraft

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

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

Oh, boy. Knowing first-hand the reliability of
electrical stuff...

Dan

On Mon, 06 Aug 2007 09:42:46 -0700, wrote
in .com:

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

Oh, boy. Knowing first-hand the reliability of
electrical stuff...


It's a prototype. The choice not to equip the automobile with brakes
demonstrates how effective the regenerative braking is, but apparently
you have to carry chocks when you park it. :-)

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;

This is significant at low airspeeds. At higher airspeeds overcoming
wind resistance takes much more power than maintaining 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,

It sure can, until it loses speed and stalls.

Bartek

On Aug 6, 3:16 pm, brtlmj wrote:
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;

That is why aircraft engines are so powerful and light; they're
depended-on to fight gravity as well as wind resistance.
Which leads us to the case of airships! They float. They don't
have to work to stay at altitude, they just hang there. Their engines
don't have to hold them up.
But, and it's a big but, since they are so big, they have more
wind resistance than airplanes. Since wind resistance is the log, or
cube? of wind speed, their hull-speeds are quite limited and their
engines remain relatively small as a result.
Enter the less-powerful electric motors! Enter solar photo-
voltaic cells! The big surface area of airships are ideal for mounting
solar arrays. And if you have a cloudy day and don't charge your
batteries up to snuff, well, you will not have to go to ground, as in
an airplane, because you are afloat in your element and you drift with
the breeze for awhile.
Words to the wise about the future of flight. High cheers from
Allen the airshipman

On Sun, 19 Aug 2007 09:53:32 -0700, dirigible designer
wrote in
. com:

On Aug 6, 3:16 pm, brtlmj wrote:

Actually, these are my words from earlier in this message thread. See:
Message-ID: .

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;

That is why aircraft engines are so powerful and light; they're
depended-on to fight gravity as well as wind resistance.
Which leads us to the case of airships! They float. They don't
have to work to stay at altitude, they just hang there. Their engines
don't have to hold them up.
But, and it's a big but, since they are so big, they have more
wind resistance than airplanes. Since wind resistance is the log, or
cube? of wind speed, their hull-speeds are quite limited and their
engines remain relatively small as a result.
Enter the less-powerful electric motors! Enter solar photo-
voltaic cells! The big surface area of airships are ideal for mounting
solar arrays. And if you have a cloudy day and don't charge your
batteries up to snuff, well, you will not have to go to ground, as in
an airplane, because you are afloat in your element and you drift with
the breeze for awhile.
Words to the wise about the future of flight. High cheers from
Allen the airshipman

Thank you for mentioning electrically powered airships.

Lighter Than Air craft are excellent candidates for electric power as
is evidenced by:


http://en.wikipedia.org/wiki/Airship
In 1883, the first electric-powered flight was made by Gaston
Tissandier who fitted a 1-1/2 horsepower Siemens electric motor to
an airship. The first fully controllable free-flight was made in a
French Army airship, La France, by Charles Renard and Arthur
Constantin Krebs in 1884 . The 170 foot long, 66,000 cubic foot
airship covered 8 km (5 miles) in 23 minutes with the aid of an
8-1/2 horsepower electric motor.




http://missilethreat.com/missiledefe...tem_detail.asp
...
In September 2003, the Missile Defense Agency (MDA) and the North
American Aerospace Defense Command (NORAD) awarded a $40 million
development contract to Lockheed Martin to build the High Altitude
Airship prototype. Lockheed Martin currently manufactures the
Goodyear blimps that can be seen over big sporting events. These
blimps are approximately 200 feet long with a volume of 200,000
cubic feet. By contrast, the HAA prototype will be 500 feet long,
160 feet in diameter, with a volume of 5.2 million cubic feet,
i.e. more than 25 times the size of the average Goodyear blimp.

MDA plans to deploy the HAA at an altitude of 65,000 feet where
the air is one-twentieth the density that it is near the ground.
One of the biggest challenges facing MDA and Lockheed Martin is
how to get the HAA from the ground to its area of deployment,
since the helium gas inside will expand more than fifteen times as
the blimp rises. To solve this problem, the HAA will be filled
mostly with air when it is close to the ground. As it rises, the
air inside the blimp will be forced out and helium from five small
inner balloons will replace it. This “balloon-within-a-balloon”
concept will allow the HAA to maintain its football-like shape
throughout all stages of flight.

Once deployed, the HAA will generate its own power supply from
thin-film photovoltaic solar cells. It will require 10 kilowatts
of electricity to run its 4,000-pound radar system. The prototype
HAA will include batteries to keep the electricity flowing at
night, although the final version will most likely use lightweight
fuel cells. Four electrically powered engines will each drive two
30-foot-wide propellers that will provide the blimp’s forward
thrust. The propellers will allow the HAA to hover within a mile
of its assigned location, thus maintaining its fixed
“geostationary” nature. ...



http://www.aiaa.org/aerospace/images...es/pdf/LTA.pdf
Zeppelin Luftschifftechnik in Germany resorted to a unique method
of delivering its NT-07 airship to a Japanese customer. The
semirigid air-ship was flown to Italy and, fully inflated, was
put on board a BPDockship for the journey to Kobe, Japan. Tail
surfaces and forward engines were removed. Zeppelin is leasing
another NT-07 to the DeBeers diamond company for two years. It
also was delivered by ship, to South Africa. The air-ship will be
equipped to examine geological formations in southern African
countries. Zeppelin carried 11,000 passengers on sightseeing
flights in Germany during 2004. Work is proceeding on the
development of the 19-passenger NT-14. First flight is expected in
early 2008. Zeppelin has acquired the intellectual property of the
defunct CargoLifter organization.

This will become part of an LTAinstitute for coordinating
activities on scientific and predevelopment levels applicable to
all types of airships. It will be headquartered in
Friedrichshafen.

Japan’s Aerospace Exploration Agency completed its series of eight
flights with the above-mentioned 223-ft-long, 370,755-ft,
un-manned research airship. The objective of these flights was to
verify flight control, operation, and tracking technologies from
takeoff to landing. Geostationary flight at 13,000 ft was realized
with the aid of electrically powered propellers. Data obtained
will be applied to JAXA’s further research into high-altitude
airships.

Another approach to this subject, a “bal-loon robot,” was
investigated by Japan’s National Institute of Advanced Industrial
Science and Technology (AIST). A 92-ft-long model carrying a 3-kg
payload was launched to an altitude of 55,700 ft. Power for
propulsion was supplied by batteries. Data transmission failure
prevented verification of station keeping.

AIST has built a 43-ft-long nonrigid propelled by cycloidal
propellers driven by electricity supplied by batteries. This
unmanned airship can be used for aerial observation and
monitoring of hazardous areas.




http://mae.pennnet.com/Articles/Arti...&KEYWORD=blimp
Latest generation of military airships to use solar electric power
by J.R. Wilson

Peterson AFB, Colo. — The North American Aerospace Defense Command
(NORAD) has joined forces with the U.S. Army and other agencies to
develop the 21st-century High Altitude Airship to help defend U.S.
airspace, control its borders, and possibly provide global
surveillance capability to military theater commanders.

"It's an old idea with new technology applied," explains U.S. Navy
Cmdr. Pat Lyons, chief of ISR and NORAD J-5 Directorate. "This
airship is unmanned, untethered, and electric powered. We expect
it to be composed of solar cells, a fuel cell, and electrolyzer
for nighttime operations."

The new airship's command-and-control links most likely will
involve satellite communications channels. All of these
technologies will probably enable the airship to remain on station
for as long as one year, Lyons says.

Electric power
The airship will be electrically powered — possibly using a
hydrogen fuel cell — with DC brushless motors and propellers as
the likely propulsion system, although the final design will be up
to the contractor; Lyons says there are several other possible
concepts for program managers to consider. That includes the
number of motors, which also would determine the number of
propellers.

"The concepts we've seen show speeds up to 100 knots for the
objective airship," Lyons explains. "The winds at 70,000 feet are
fairly benign; you're above the weather and the jet stream, but
occasionally, depending on where you are, they can get up to 100
knots, building for 24 hours, peaking for a day, then diminishing
for a day. With a 100-knot airspeed, the airship can remain
geostationary," Lyons says.

A variety of sensors are being considered for the airship's
Advanced Concept Technology Demonstration (ACTD), including a
small communications relay. In operation, the vehicle could be
used to enable communications 600 or more miles apart, including
over a mountain. Currently, ground troops with handheld
communications must post a relay unit on a water tower or other
tall structure to avoid losing contact in the field. ...

Military & Aerospace Electronics August, 2002
Author(s) : J.R. Wilson

On Aug 7, 3:39 am, Larry Dighera wrote:
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.

In theory, I think that stirling engines are quite well suited to
aircraft, all it needs is a source of "hot" and a source of "cold",
the cold is in abundance (stick a heatsink in the wind, higher you go,
colder it gets, more power the engine can deliver, directly the
opposite of IC), the hot could be provided with any number of
combustables (and some oxygen delivery system).

I found yesterday after writing my initial post an article about
exactly this - http://www.qrmc.com/fourpartstirling.html "Why Aviation
Needs the Stirling Engine by Darryl Phillips" from 1993/1994.

Given what was said in the article, I'm kind of surprised that nobody
has come up with a working protoype actually.

James Sleeman wrote:

stick a heatsink in the wind, higher you go,
colder it gets, more power the engine can deliver, directly the
opposite of IC

What I didn't get from the article: Where does the "hot" come from? A fuel
burner, probably, which would have the same problems with altitude as an IC
engine, wouldn't it?

Ad-
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The mail address works, but please notify me via usenet of any mail you send
to it, as it has a retention period of just a few hours.

On Mon, 06 Aug 2007 18:22:41 -0700, James Sleeman
wrote in
.com:

On Aug 7, 3:39 am, Larry Dighera wrote:
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.

In theory, I think that stirling engines are quite well suited to
aircraft, all it needs is a source of "hot" and a source of "cold",
the cold is in abundance (stick a heatsink in the wind, higher you go,
colder it gets, more power the engine can deliver, directly the
opposite of IC), the hot could be provided with any number of
combustables (and some oxygen delivery system).

I see what you mean. Unfortunately, the highest power requirements of
aircraft engines are during the takeoff and climb phases of flight.
Power requirements are even greater when the ambient temperature rises
resulting in less air density or a higher density altitude. That is
when the most power is required for takeoff, but that would be a
situation where the Stirling engine would have its minimum power
production.

I would also like to see a comparison of the efficiencies of IC and EC
engines and their relative weight and size per horsepower compared.

Unlike electrical motors, that must be constructed with heavy iron, IC
and EC engines can be constructed of lighter materials like aluminum,
but electrical motors are usually 80% to 95% efficient. With the
Stirling aircraft engine there is a requirement for what I would
imagine would be a large heat sink or heat exchanger located in the
slip stream. The weight of this heat exchanger and its drag penalty
must also be considered.

I found yesterday after writing my initial post an article about
exactly this - http://www.qrmc.com/fourpartstirling.html "Why Aviation
Needs the Stirling Engine by Darryl Phillips" from 1993/1994.

Given what was said in the article, I'm kind of surprised that nobody
has come up with a working protoype actually.

The article is interesting; thank you for mentioning it. I am
e-mailing a copy of this followup article to the author Darryl
Phillips.

There might be one advantage to using Sterling external combustion
engines for aviation: the use of atomic energy as a fuel source if the
weight of the lead shielding were not too great. Imagine an aircraft
that effectively never runs out of fuel! There'd be no more fuel
exhaustion mishaps.

Recently, Larry Dighera posted:

On Mon, 06 Aug 2007 18:22:41 -0700, James Sleeman
wrote in
.com:

On Aug 7, 3:39 am, Larry Dighera wrote:
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.

In theory, I think that stirling engines are quite well suited to
aircraft, all it needs is a source of "hot" and a source of "cold",
the cold is in abundance (stick a heatsink in the wind, higher you
go, colder it gets, more power the engine can deliver, directly the
opposite of IC), the hot could be provided with any number of
combustables (and some oxygen delivery system).

I see what you mean. Unfortunately, the highest power requirements of
aircraft engines are during the takeoff and climb phases of flight.
Power requirements are even greater when the ambient temperature rises
resulting in less air density or a higher density altitude. That is
when the most power is required for takeoff, but that would be a
situation where the Stirling engine would have its minimum power
production.

If an engine's minimum power production is greater than the power required
for takeoff, would it matter? It would seem that if this could be
achieved, the operating conditions of the Stirling engine would be mostly
understressed.

I would also like to see a comparison of the efficiencies of IC and EC
engines and their relative weight and size per horsepower compared.

Unlike electrical motors, that must be constructed with heavy iron, IC
and EC engines can be constructed of lighter materials like aluminum,
but electrical motors are usually 80% to 95% efficient. With the
Stirling aircraft engine there is a requirement for what I would
imagine would be a large heat sink or heat exchanger located in the
slip stream. The weight of this heat exchanger and its drag penalty
must also be considered.

Why couldn't the heat exchanger be an integral part of the airframe? Wings
come to mind... ;-)

There might be one advantage to using Sterling external combustion
engines for aviation: the use of atomic energy as a fuel source if the
weight of the lead shielding were not too great. Imagine an aircraft
that effectively never runs out of fuel! There'd be no more fuel
exhaustion mishaps.

One downside would be the hazardous materials that could be dispersed in a
crash. I'd like to see a prototype Stirling using conventional fuels
before exploring more exotic options.

Neil