Electrically Powered Ultralight Aircraft

cavelamb himself wrote:
wrote:

To carry more weight at the same speed and altitude takes more power,
so you have to account for the energy expended kiting you
deadweight electric takeoff system around the sky as well. Sizing
an engine for cruise has been done, if only backwards. Think JATO.
Most JATO's are actually RATO (rocket assisted takeoff). I expect
RATO would beat an electric system based on energy density and the
fact that when it is done you have reduced your weight by the fuel.
I also suspect for a given amount of thrust the rocket will be
lighter than an electric motor and associated clutches and gearing.
In my opinion, at this point in time it is just as practical for a
homebuilt as well as in not.


Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...


The original remark said "To carry more weight at the same speed and
altitude takes more power" -- which you have now taken the time to
substantiate with more detail. It never said it was the only factor,
and didn't need to, to rebut the earlier claim. I do not understand how
you arrive at it not being true. Frankly, I would expect any one
engaged in building or flying an airplane to understand those
relationships, and based on the FAA's published pilot exam questions and
other materials, it seems they agree.

Charles

wrote:
In rec.aviation.piloting cavelamb himself wrote:
wrote:
To carry more weight at the same speed and altitude takes more power, so
you have to account for the energy expended kiting you deadweight
electric takeoff system around the sky as well. Sizing an engine for
cruise has been done, if only backwards. Think JATO. Most JATO's are
actually RATO (rocket assisted takeoff). I expect RATO would beat an
electric system based on energy density and the fact that when it is
done you have reduced your weight by the fuel. I also suspect for a
given amount of thrust the rocket will be lighter than an electric motor
and associated clutches and gearing. In my opinion, at this point in
time it is just as practical for a homebuilt as well as in not.

Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?


No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.

Charles

wrote

Unless the added weight is enough to deform the tires, the increase
in rolling resistance in the total energy expediture can't be found.

Bull hockey.

Just because it is not noticeable, or measurable by the lack of sensitivity
with the instrument you are currently not using, does not mean that it does
not exist.

More weight on the bearings will cause more rolling resistance. That is
fact, not open to dispute. If you say it is, I want to buy the rights to
the bearings you are using, so I can patent them and make a fortune.
--
Jim in NC

In rec.aviation.piloting Charles Vincent wrote:
wrote:
In rec.aviation.piloting cavelamb himself wrote:
wrote:
To carry more weight at the same speed and altitude takes more power, so
you have to account for the energy expended kiting you deadweight
electric takeoff system around the sky as well. Sizing an engine for
cruise has been done, if only backwards. Think JATO. Most JATO's are
actually RATO (rocket assisted takeoff). I expect RATO would beat an
electric system based on energy density and the fact that when it is
done you have reduced your weight by the fuel. I also suspect for a
given amount of thrust the rocket will be lighter than an electric motor
and associated clutches and gearing. In my opinion, at this point in
time it is just as practical for a homebuilt as well as in not.

Well, that's true enough, but the above was about hybrid cars.



No, it's not true enough.

To carry more weight at the same speed and altitude requires more LIFT.

A higher CL - and/or more wing area.

THEN, to overcome the increased drag, THEN you need more power.

But more power by itself won't satisfy the constraints...

So if I add 1 pound to a 2400 pound gross aircraft loaded to 2300 pounds,
it would be impossible to cruise at the same speed and altitude without
the 1 pound unless I added wing area?

How about 50 pounds?


No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.


Gee, you mean all I gotta do is tweek the trim and throttle a bit?

Who'd have guessed it? :-)


--
Jim Pennino

Remove .spam.sux to reply.

On Aug 15, 8:18 am, Larry Dighera wrote:
On Wed, 15 Aug 2007 12:23:00 GMT, CanalBuilder
wrote in
:

How much of a fire hazard would a paper battery be?

http://www.energy-daily.com/reports/...oring_Power_In...

That is an interesting device indeed. Given these quotes from the
article:

Rensselaer researchers infused this paper with aligned carbon
nanotubes, which give the device its black color. The nanotubes
act as electrodes and allow the storage devices to conduct
electricity. The device, engineered to function as both a
lithium-ion battery and a supercapacitor, can provide the long,
steady power output comparable to a conventional battery, as well
as a supercapacitor's quick burst of high energy. ...

Along with use in small handheld electronics, the paper batteries'
light weight could make them ideal for use in automobiles,
aircraft, and even boats. The paper also could be molded into
different shapes, such as a car door, which would enable important
new engineering innovations.


IF these can be made practical, they sound ideal for use in an
airplane. They are light, and they can be shaped in just about any
way to fit inside the airframe. Suppose they were integrated into the
airframe and wings such that a large percentage of the airplane
consisted of battery. It might be possible to get enough capacity
there for a practical general aviation electric plane.

Charles Vincent wrote:

No. You can increase the angle of attack, which increases the lift ( to
a limit) and also increases the drag, which must be overcome with more
power. If your speed drops, so does the lift. If you could increase
your aspect ratio, you could get more lift at the same speed at the same
power I think. So I guess Richard is flying a swing wing texas
parasol.;') For the rest of us, we have to add power to carry more
weight at the same speed and altitude. Since most planes lose weight
while in flight in the real world, you actually have the opposite issue.

Charles


Don't be snotty, Charles.


Since the subject is an electrically powered aircraft, the weight issue
is not trivial. That's been my issue with this thread from the start.

The constraints given here were to fly at the same speed and altitude
but at a higher weright.

You can increase lift via increased angle of attack only as far as
CLmax. No Farther. (You seem to have that part right)

Beyond that any increased weight will require increased wing area.

Aspect ratio alone won't answer is most cases.

And - an electric powered plane would NOT lose weight in flight.

No electrons are "consumed" - no change in battery weight.

"Phil" wrote

IF these can be made practical, they sound ideal for use in an
airplane. They are light, and they can be shaped in just about any
way to fit inside the airframe. Suppose they were integrated into the
airframe and wings such that a large percentage of the airplane
consisted of battery. It might be possible to get enough capacity
there for a practical general aviation electric plane.

I can see the headlines, now.

Plane (or car) crashes, and the car's structure electrocutes the occupants.
g
--
Jim in NC

On Fri, 17 Aug 2007 11:28:06 -0700, Phil wrote
in .com:

It might be possible to get enough capacity
there for a practical general aviation electric plane.

It might indeed. But I'd have to know more about the paper battery
specifications before I could render any sort of judgment. I guess
we'll have to wait until more information is disclosed. Let's see
.....



http://www.eetimes.com/news/semi/rss...etimes_semiRSS

Paper battery is rechargeable

R. Colin Johnson
EE Times
(08/14/2007 9:42 AM EDT)

PORTLAND, Ore. — Rensselaer Polytechnic Institute researchers
said they have developed a paper-thin battery by immersing a
carpet of vertical nanotubes in an ionic liquid electrolyte. The
result is a cellulose paper that stores electrical energy.

The RPI team produced a supercapacitor by placing a second
nanotube electrode on the other side of the paper. They then added
a lithium electrode atop the paper, creating what they claim is a
paper-thin rechargeable battery.

"The carbon nanotubes are embedded in the paper, and the
electrolyte is soaked into the paper, so it really looks, feels
and weighs about the same as paper," said RPI professor Robert
Linhardt.

The supercapcitor and rechargeable battery are the result of a
year and half of collaborative research among three RPI labs. One
lab was making carbon nanotube-based structures, which were
adapted to serve as a battery electrode. By growing the nanotubes
vertically on a sheet, liquid cellulose was poured between the
"forest of nanotubes" to form the battery. Another lab added a
lithium-based top electrode to create either a rechargeable
battery
or a supercapacitor by adding a second nanotube electrode.

Ionic liquids first dissolved the cellulose, turning it into a
gel.
The fluids also serve as the battery electrolyte, carrying ions
from one side of the paper battery to the other.

Each sheet of battery-paper generated about 2.4 volts with a power
density of about 0.6 milliamps/cm2. For higher voltages, paper can
be stacked. For more current, the sheets can be expanded to larger
areas. The battery-paper operates from minus 100 degrees up to 300
degrees Fahrenheit, and can deliver quick surges of current, the
RPI researchers claim. It can also be rolled twisted or cut into
many shapes.

So far, the RPI researchers have only cycled their paper batteries
through 100 rechargings. But they claim no deterioration in
performance has been detected after recharging. Next, they plan
long-term testing of the batteries to determine the maximum number
of rechargings, and to optimize the design for higher power
densities. ...



http://www.uberreview.com/2007/08/fl...-institute.htm
It does not function better than existing batteries on the market
and at present it is extremely expensive to produce.


http://news.rpi.edu/update.do?artcenterkey=2280
Contact: Michael Mullaney
Phone: (518) 276-6161
E-mail:

“We’re not putting pieces together – it’s a single, integrated
device,” he said. “The components are molecularly attached to each
other: the carbon nanotube print is embedded in the paper, and the
electrolyte is soaked into the paper. The end result is a device
that looks, feels, and weighs the same as paper.”




Can someone make the necessary conversions to compare the power
density of about 0.6 milliamps/cm2 for the paper battery to secondary
lithium-ion Polymer batteries at 130 - 1200 Wh/kg*?



* http://xtronics.com/reference/energy_density.htm

The original paper battery article is available on-line:

http://www.pnas.org/cgi/content/abst...urcetype=HWCIT
Proceedings of the National Academy of Sciences of the United States
of America

Published online before print August 15, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0706508104


This Article

Full Text (PDF)
Articles by Pushparaj, V. L.
Articles by Ajayan, P. M.


Engineering
Flexible energy storage devices based on nanocomposite paper

To whom correspondence should be addressed.

Pulickel M. Ajayan, E-mail:

Morgans wrote:
"Phil" wrote

IF these can be made practical, they sound ideal for use in an
airplane. They are light, and they can be shaped in just about any
way to fit inside the airframe. Suppose they were integrated into the
airframe and wings such that a large percentage of the airplane
consisted of battery. It might be possible to get enough capacity
there for a practical general aviation electric plane.


I can see the headlines, now.

Plane (or car) crashes, and the car's structure electrocutes the occupants.
g

LOL!

These paper batterise are light because they are so small.

By the time they make a battery will a few megawatts capacity, it's NOT
going to be all that light.

Lighter than Lead/Acid? Probably.

But light enough to fly? It might be a while...