Electrically Powered Ultralight Aircraft

Recently, Larry Dighera posted:

On Tue, 07 Aug 2007 17:51:27 GMT, "Neil Gould"
wrote in
:

Recently, Larry Dighera posted:
[...]
I'm thinking there would be necessity for some means of conducting
the heat from the engine to a remote heat exchanger, and the
resulting complexity and weight increase would negatively impact
the potential advantages of a Stirling aviation engine. In any
event, in addition to the Stirling engine and its fuel, a heat
exchanger of some type needs to factored into the weight, cost,
performance, and efficiency equations.

Of course, but I don't see a lot of reason why that couldn't be
incorporated into the overall design. My point is that heat
exchangers need not be heavy, and could probably double as
structural and/or aerodynamic components, further reducing (and
possibly enhancing) their impact.

How would you get the heat from the Stirling engine to the heat sink?
If you use liquid coolant, it would be heavy and prone to leaks.

I'm not a Stirling engine designer, so I can't answer that factually. I
have been reading up on it a bit since the article was referenced in this
thread, but I haven't seen such things as the required rate of dissipation
for the engine to work efficiently. If the heat sink needs to be large and
close to the engine, perhaps a design where the engine is mounted on or
even incorporated into the wing is a way to go.

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.

There are a lot of down sides to atomic power, but NASA uses it to
power Stirling engines in space.

Understandable, but their expectation is that catastrophic
destruction would disperse the nuclear material harmlessly. That
can't be presumed for light aircraft.

If the rocket detonated in the atmosphere, it might not be so
harmless.

I don't see why it would be nearly as bad as a "dirty bomb" would be, as
the material would be dispersed over a pretty large area.

I would guess the reactor is jacketed with sufficient
strength to preclude its destruction.

My guess is that NASA et al are just hoping for good fortune. Having a
reactor land from orbit intact in the middle of a city wouldn't be all
that desirable. ;-) So, my bet is on there being no good plan for
dealing with such a catastrophe *other* than wide dispersal of the nuclear
material or the luck of landing in the ocean. Not that *that* outcome is
desirable either...

Neil

"Larry Dighera" wrote in message
...

I would think that would be close to the bare minimum. I flew a fixed wing
hang glider on 10 HP for a while back in the 70s. A Manta Fledgling, and
it
was very underpowered. Maybe 100 fpm climb or so.


I would guess the rigid wing would have a higher L/D than a powered
parachute's 4:1, so it might require less power. Does that sound
correct in your experience?

Indeed, quite a bit less from my experience. I think my Fledge was supposed
to be around 10:1.

On Tue, 07 Aug 2007 14:58:07 GMT, Larry Dighera
wrote:

If a 14 HP electric propulsion system weighing 46 lbs could be
constructed, apparently it would permit the use of PPGs by pilots up
to 180 lbs.

A PPG is a LOT more efficient than a powered parachute (PPC), but
still far less efficient than a rigid wing. Still, several electric
PPG's have been flown. The primary goal here is noise and vibration
reduction, a worthy goal when the engine is strapped to the pilot's
back.

The major problem is the weight of the batteries, still far heavier
than gasoline. Also the lithium polymer batteries used are still
quite expensive (over $10,000 for enough for a half hour flight) and
somewhat dangerous (sort them out and they can explode!)

-Dana

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"Dana wrote
The major problem is the weight of the batteries, still far heavier
than gasoline. Also the lithium polymer batteries used are still
quite expensive (over $10,000 for enough for a half hour flight) and
somewhat dangerous (sort them out and they can explode!)

Damn straight! No way am I going to strap a bunch of lithium polymer
batteries to my butt.

Some of the newer Lithium iron cells, maybe, but they also cost a LOT more.

Still, electric flight, like many have said, still have a way to go.
--
Jim in NC

Morgans wrote:
"Dana wrote
The major problem is the weight of the batteries, still far heavier
than gasoline. Also the lithium polymer batteries used are still
quite expensive (over $10,000 for enough for a half hour flight) and
somewhat dangerous (sort them out and they can explode!)

Damn straight! No way am I going to strap a bunch of lithium polymer
batteries to my butt.

Some of the newer Lithium iron cells, maybe, but they also cost a LOT
more.
Still, electric flight, like many have said, still have a way to go.

And as if we need more proof of this.

TOKYO: Japan's Toyota Motor Corp. will delay by one or two years the rollout
of new high-mileage hybrids with lithium-ion batteries because of safety
concerns, reported a newspaper.

Toyota's decision was prompted by worries that the batteries could overheat,
catch fire or even explode, the Wall Street Journal on Thursday reported in
its online edition, quoting unnamed Toyota executives.

On Thu, 09 Aug 2007 23:13:55 -0400, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote in
:

On Tue, 07 Aug 2007 14:58:07 GMT, Larry Dighera
wrote:

If a 14 HP electric propulsion system weighing 46 lbs could be
constructed, apparently it would permit the use of PPGs by pilots up
to 180 lbs.

A PPG is a LOT more efficient than a powered parachute (PPC), but
still far less efficient than a rigid wing. Still, several electric
PPG's have been flown. The primary goal here is noise and vibration
reduction, a worthy goal when the engine is strapped to the pilot's
back.

The major problem is the weight of the batteries, still far heavier
than gasoline. Also the lithium polymer batteries used are still
quite expensive (over $10,000 for enough for a half hour flight) and
somewhat dangerous (sort them out and they can explode!)

-Dana

That's interesting information. Thank you.


It sounds like you have quite a bit of experience in this area. Are
you able to provide links to any forums or web sites related to this
topic?

Are
you able to provide links to any forums or web sites related to this


Check this out: http://www.calcars.org/news-archive.html

David Johnson

On Aug 10, 5:12 pm, Dave wrote:
Are

you able to provide links to any forums or web sites related to this

Check this out:http://www.calcars.org/news-archive.html

David Johnson

Lithium Polymer batteries are widely used in RC planes, cars, etc and
are known to be potentially dangerous. Most runaway fires occur during
charging but it has also occurred to a lessor degree during discharge
and even storage. Vented charging safety bags are recommended for this
reason. There is a video on this link that shows the explosive power
of small LiPo's. Consider the size differance of these batteries to
the one hung under the trike in one of the first posts or those that
could be installed in the wings of a sailplane.
http://www.liposack.com/video.html

On Sat, 11 Aug 2007 06:59:02 -0700, wrote in
.com:


Lithium Polymer batteries are widely used in RC planes, cars, etc and
are known to be potentially dangerous. Most runaway fires occur during
charging but it has also occurred to a lessor degree during discharge
and even storage.

I would assume that the source of these Li-ion Polymer battery fires
is excessive electrical current flowing through the battery either
from too high a charging rate, too high a discharge rate, or a short
internal (as in the case of the Sony laptop cells) or external, or
being over charged. Perhaps it would be prudent to install a circuit
breaker of fuse to prevent too high a current and a timer to
disconnect a forgotten charger.

Vented charging safety bags are recommended for this
reason. There is a video on this link that shows the explosive power
of small LiPo's. Consider the size differance of these batteries to
the one hung under the trike in one of the first posts or those that
could be installed in the wings of a sailplane.
http://www.liposack.com/video.html

Thank you for the link. It is spectacular.


Here are some links relevant to the Sony Lithium laptop battery
recall:

Story: http://www.theinquirer.net/default.aspx?article=32550
http://news.com.com/Dell+takes+heat+...3-6105828.html

Video:
http://www.youtube.com/watch?v=WeWq6...lated&search=#

Explanation of cause:
http://reviews.cnet.com/4660-10165_7-6625980.html
http://www.prnewstoday.com/release.h...H05424082006-1
The recall arises because, on rare occasions, microscopic metal
particles in the recalled battery cells may come into contact with
other parts of the battery cell, leading to a short circuit within the
cell. Typically, a battery pack will simply power off when a cell
short circuit occurs. However, under certain rare conditions, an
internal short circuit may lead to cell overheating and potentially
flames. The potential for this to occur can be affected by variations
in the system configurations found in different notebook computers.

The thing that strikes me most in this thread is that so many people
just don't seem to understand...

1) weight

2) power

3) scale