Electrically Powered Ultralight Aircraft

Orval Fairbairn wrote:
> In article <orfairbairn-5D8336.11534806082007@news.west.**************>,
> Orval Fairbairn <orfairbairn@**************> wrote:
>
>> In article <1186384454.047870.95690@z24g2000prh.************. com>,
>> James Sleeman <bitsyboffin@**********> wrote:
>>
>>> On Aug 6, 4:52 am, Larry Dighera <LDigh...@att.net> 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).
>> Look at the problem this way: In an all-electric machine, you carry ALL
>> of your energy supply with you: fuel and oxidizer -- to make electricity.
>>
>> With any IC engine, you carry the fuel only -- the air is free (20%
>> oxygen), so, at 15:1 air/fuel ratio, you would need 90 lb of air for
>> each gallon of fuel.
>>
>> Therefore, for a nominal 50 gallon fuel capacity (300 lb), you would
>> have to carry an additional 7500 lb of air.
>>
>> That is a lot of weight for a 3000 lb aircraft!
>
> DUH! I meant 4500 lb of air! That is still a lot of weight penalty.


Well, to be fair Orval, you do get the 90% efficiency in an electric
motor, vs the 30% in an IC engine. You'd only have to drop 1500lb of
useful load with the electric motor.

Isn't the useful load of most light airplanes somewhere between 600 and
2000lbs?

Gattman wrote:

> I agree. It's on the way. Wasn't too long ago that terms like "lithium
> ion" and "nickle metal hydride" were unheard of to the common consumer.
>

It takes a lot of energy to manufacture those batteries ... and recycle
them when they are used up. You have to factor that into the equation.

These batteries have high energy per unit volume but they cost a lot
of money because it takes a lot of energy to produce them.

<jimp> wrote

> In rough numbers, you get about 1 kW/m^2 of energy from the sun on
> a clear day.
>
> Current conversion technology is about 22% at best.
>
> Technologies in the works are promising 50-60% (the check is in the
> mail and I will respect you in the morning).
>
> One presumes a sailplane is going to spend most of its time sailing
> and only using the motor (with batteries) to get off the ground
> and occassionaly cruise between thermals.
>
> So most of the time you are just charging the batteries.

That is why I specified cruising with the motor without thermals; to get a
feel on how the extra surface area and high aspect ratio (efficiency) would
mimic a cross country, motor cruise.
--
Jim in NC

Larry Dighera wrote:

>
>
> I have no idea if a one hundred
> horsepower motor of this type would weigh 100 lbs or not, but it seems
> reasonable.

That's why I showed the first 100HP electric motor I could find. They
obviously don't make a 100HP motor of the type you showed or you would have
quoted it's specs.

I doubt they add the extra 1000 lbs just for the fun of it.

On Tue, 07 Aug 2007 17:51:27 GMT, "Neil Gould"
<neil@myplaceofwork.com> wrote in
<zi2ui.56271$5j1.49021@newssvr21.news.prodigy.net> :

>Recently, Larry Dighera <LDighera@att.net> 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.

>>>> 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 would guess the reactor is jacketed with sufficient
strength to preclude its destruction. Presumably, that could be done
for a Stirling aircraft engine also.

Recently, Larry Dighera <LDighera@att.net> posted:

> On Tue, 07 Aug 2007 17:51:27 GMT, "Neil Gould"
> <neil@myplaceofwork.com> wrote in
> <zi2ui.56271$5j1.49021@newssvr21.news.prodigy.net> :
>
>> Recently, Larry Dighera <LDighera@att.net> 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" <LDighera@att.net> wrote in message
news:g99jb3pelo3uf51ln52mddrshorho14q3a@********...
>>
>>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.

"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
<gnlnb3d2ardprj3h02g9ve654uutvsri9a@********>:

>On Tue, 07 Aug 2007 14:58:07 GMT, Larry Dighera <LDighera@att.net>
>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?