$1 billion BMS Ooops...

John Cochrane wrote on 3/3/2021 8:53 PM:
For the moment the big limitation seems to me to be weight. I looked hard at the AS33 electric. You get one launch to 2000' and then 9000' of climb to get home. For that, it's really hard to get off the ground at less than 10 lbs/ft2 empty, and 10.5 in 15 m mode. Gas has a wonderful energy density. I'm surprised some sort of hybrid doesn't make sense, gas to recharge a smaller battery, then eliminate the drive elements with an electric motor. But I presume they worked the numbers on this.

A hybrid system with a gas engine wouldn't have the pucker factor associated with starting a
gas powered motorglider to avoid a landing: if the hybrid engine doesn't start, it just means
your potential retrieve distance is shorter, instead of an imminent landing.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

2G wrote on 3/3/2021 6:11 PM:
On Tuesday, March 2, 2021 at 8:27:55 PM UTC-8, Eric Greenwell wrote:
2G wrote on 3/2/2021 7:25 PM:
On Tuesday, March 2, 2021 at 6:28:27 PM UTC-8, Andrzej Kobus wrote:
On Tuesday, March 2, 2021 at 4:10:48 PM UTC-5, ProfJ wrote:
On Wednesday, 24 February 2021 at 14:42:01 UTC-7, wrote:
https://insideevs.com/news/490300/hy...ll-82000-bevs/
Discus amongst yourselves...
Some comments:

- High current draw for VTO launches (Lilium) - IIRC they are planning to use supercapacitors to provide the current boost so that the batteries don't have to. A supercapacitor/LiPo combination makes a lot of sense for that problem.

- Electric vs. gas: a very experienced motorglider ferry pilot, who I am sure does not want to be named, once told me when discussing Stemmes: "I've had every known Stemme issue except the in-flight fire, I'm not looking forward to that one..." I side with Eric here - we have normalized all the hassle that goes with gas self-launchers. When we get mature technology electric self-launchers, they'll dominate. Current complaints about electric sound exactly like the complaints about electric cars, before Tesla got it right.
So how big is the electric glider market vs. electric car market? Things get done with proper research and funding. I don't see that happen for the glider market. I suggest you review David's presentation. He discussed this point.

ICO glider engines have been developed over the last 70 years or so. And, then, many of them have come from the 2-cycle engine applications such as snowmobiles and ultralights. The electric glider market is much more immature..

That immaturity means they have a lot of promise, compared to the ICE gliders. We know in 5
years the performance of the electrics will increase significantly; the fossil fueled ones -
not nearly so much. Even at the current immature stage, they are so desirable, all the major
manufacturers, and some of the second tier, offer at least two electric models in mast or FES
varieties.

I suggest that in maybe 5, but certainly in 10 years, the discussions will no longer be about
gas vs electric, but which electric to buy.
--
yhttps://sites.google.com/site/motorgliders/publications/download-the-guide-1

Wishful thinking duly noted. The development, deployment and long-term flight experience of aircraft takes time. Ten years is a good estimate for a single model such as the Antares. Its first flight was in 2003, so development must have started about 20 years ago. I think that in 5 to 10 years we will be thinking "Boy, those electric gliders looked promising at the time, but if we knew then what we know now I would never have bought one." Successful product development just can't be rushed.

It's not wishful thinking when there are four companies selling electric glider power systems:
Lange, Solo, Pipistrel, and LZ Design (FES). The glider manufacturers do not have to design
their own system, like Antares had to. That speeds development (even eliminates it in some
cases), reduces their cost, and increases reliability.

While the glider market is very small, the main component - batteries - is under intense
development by major corporations around the world. We will benefit from this investment,
without investing a dime in it.

As for glider pilots feeling sorry for their current electric choices in 5 or 10 years, well,
I'm going to suggest many glider pilots will be feeling sorry for their current gas engine
choices ;^)

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

On Wednesday, March 3, 2021 at 11:53:15 PM UTC-5, wrote:
For the moment the big limitation seems to me to be weight. I looked hard at the AS33 electric. You get one launch to 2000' and then 9000' of climb to get home. For that, it's really hard to get off the ground at less than 10 lbs/ft2 empty, and 10.5 in 15 m mode. Gas has a wonderful energy density.. I'm surprised some sort of hybrid doesn't make sense, gas to recharge a smaller battery, then eliminate the drive elements with an electric motor. But I presume they worked the numbers on this.

John Cochrane BB
Hybrid, at best, would provide no benefit in weight and the complexity of both solutions added together.
The problem the manufacturer's have is that they know the users expect to launch at max weight and have acceptable safety margins at launch.
This requires powerful motors having high consumption. Oh- and we want long range for retrieves.
All this adds up to big batteries.
Now insert this into an airframe designed for high wing loading and IGC specified maximum mass.
You end up with a glider not suitable for eastern US, nor most of Europe.
Waiting for new batteries that will solve this problem is a fools errand.
Maybe manufacturers should consider 2 options on batteries. 1/2 the battery in the '33 would save somewhere around 65 lb by my estimate. On a 107 sq ft glider, that is a big deal.
I'm looking now at electric 29E possibility. With the system I have in the '24E(L) I would expect a launch and around 3000 feet of additional retrieve climb from a system that would add about 40 lb to the weight of the 29E. With 25kw available at launch I see as a dry self launch only ship.
FWIW
UH

Hank Nixon wrote on 3/4/2021 8:56 AM:
On Wednesday, March 3, 2021 at 11:53:15 PM UTC-5, wrote:
For the moment the big limitation seems to me to be weight. I looked hard at the AS33 electric. You get one launch to 2000' and then 9000' of climb to get home. For that, it's really hard to get off the ground at less than 10 lbs/ft2 empty, and 10.5 in 15 m mode. Gas has a wonderful energy density.. I'm surprised some sort of hybrid doesn't make sense, gas to recharge a smaller battery, then eliminate the drive elements with an electric motor. But I presume they worked the numbers on this.

John Cochrane BB
Hybrid, at best, would provide no benefit in weight and the complexity of both solutions added together.
The problem the manufacturer's have is that they know the users expect to launch at max weight and have acceptable safety margins at launch.
This requires powerful motors having high consumption. Oh- and we want long range for retrieves.
All this adds up to big batteries.
Now insert this into an airframe designed for high wing loading and IGC specified maximum mass.
You end up with a glider not suitable for eastern US, nor most of Europe.
Waiting for new batteries that will solve this problem is a fools errand.
Maybe manufacturers should consider 2 options on batteries. 1/2 the battery in the '33 would save somewhere around 65 lb by my estimate. On a 107 sq ft glider, that is a big deal.
I'm looking now at electric 29E possibility. With the system I have in the '24E(L) I would expect a launch and around 3000 feet of additional retrieve climb from a system that would add about 40 lb to the weight of the 29E. With 25kw available at launch I see as a dry self launch only ship.
FWIW
UH

The JS3 RES batteries are set up like an FES glider, even though it's a mast mounted motor
system: two batteries can be carried in the motor bay, but only one is required for operation.
They are about 50 lbs each. Being able to remove and charge them elsewhere should be a great
convenience.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

Energy density is the "elephant in the room" that determines a lot about electric vs. internal combustion. The Tesla S uses a 100 kWh battery that weighs 1,375 lbs. 100 kWh is approximately the same energy contained in 2.1 gallons of AvGas. So, you have a 2 gallon capacity (about 13 lbs.) in a 1,375 lb. container. Makes perfect sense to me. NOT!

And we aren't even bringing up the environmental impact of producing the battery and then disposing of it when its life is used up.

A Electrical engineer once said to me:
If you got a battery you got battery problems.
I own 3 vehicles and 3 motorcycle's, it seems like I'm always buying batteries.
When the tug rolls up to me and the line boy runs up with the rope I smile and say to my self
" this is cheap"
I generally release right into a big fat thermal.
Fly safe in 2021
Nick
T

On Thursday, March 4, 2021 at 2:55:20 PM UTC-5, Mark Mocho wrote:
Energy density is the "elephant in the room" that determines a lot about electric vs. internal combustion. The Tesla S uses a 100 kWh battery that weighs 1,375 lbs. 100 kWh is approximately the same energy contained in 2.1 gallons of AvGas. So, you have a 2 gallon capacity (about 13 lbs.) in a 1,375 lb. container. Makes perfect sense to me. NOT!

And we aren't even bringing up the environmental impact of producing the battery and then disposing of it when its life is used up.


Has anyone in the SLS group been considering some FLYING?
the wave systems in the East have been awesome in the last few days (Mar02-04)
Not too cold at 10K (-10C) ; an eyeball dream suggested that Lk Placid to Bangor Me
and return (650KM) or much further south would have been possible.
Besides Lk Pl., there must be numerous airports with plowed runways and aprons.

enviously

John Firth (Ottawa)

PS cannot find how to start a new subject!

On Thu, 04 Mar 2021 11:55:17 -0800, Mark Mocho wrote:

Energy density is the "elephant in the room" that determines a lot about
electric vs. internal combustion. The Tesla S uses a 100 kWh battery
that weighs 1,375 lbs. 100 kWh is approximately the same energy
contained in 2.1 gallons of AvGas. So, you have a 2 gallon capacity
(about 13 lbs.) in a 1,375 lb. container. Makes perfect sense to me.
NOT!

And we aren't even bringing up the environmental impact of producing the
battery and then disposing of it when its life is used up.

Here are some free-wheeling thoughts inspired by what I've read about the
Aptera hybrid road vehicles: the prototype used an all-electric drive
chain connected to a battery with a 40 mile range when fully charged. It
also carried a small ICE generator pack - on ling trips the rig was said
to average 120 mpg.

So, how would a similar set-up work for us?

Say, use a pylon-mounted electric motor coupled to a battery capable of
take-off olus a 2000 ft climb (i.e. a somewhat higher than normal winch
launch) and carry a small ICE generator pack to be run during and after
launch to recharge the battery.

A modern 20cc 2-stroke can knock out 2.5 hp at 9000rpm (around 1.8 kWh,
so with a 40% efficient generator you can recharge the battery at a 0.7
kWh rate from a unit with a guestimated weight of 1.5 Kg (750 g motor
plus the same weight for the generator) plus fuel at around 9,7 kWh/litre
(thats 12 kWh/kg) so something like 1.2 kWh/liter of fuel can be put back
into the battery after launch (assuming motor efficiency 25% and
generator efficiency 40%). Now, scale the system up a bit and use a 200cc
generator set and you've got an equipment weight of 15 kg plus fuel and a
recharge rate of around 12 kWh. Time to recharge a 20 Kwh launch battery
is around 1.7 hours, so a fair time to be listening to the (muffled)
engine behind you, but a much lighter system than a pure electric system
(launch battery + 15kg generator set) would be.

What did I miss?


--
Martin | martin at
Gregorie | gregorie dot org

Mark Mocho wrote on 3/4/2021 11:55 AM:
Energy density is the "elephant in the room" that determines a lot about electric vs. internal combustion. The Tesla S uses a 100 kWh battery that weighs 1,375 lbs. 100 kWh is approximately the same energy contained in 2.1 gallons of AvGas. So, you have a 2 gallon capacity (about 13 lbs.) in a 1,375 lb. container. Makes perfect sense to me. NOT!

And we aren't even bringing up the environmental impact of producing the battery and then disposing of it when its life is used up.


There seems to be an anomaly with your numbers: The 100 kWh battery delivers about 400 miles of
range. How is it possible to go that far on the equivalent of 2.1 gallons of Av Gas?

And yet, wouldn't you love to have access to a Tesla S? I know I would! I was an engineer
during my working years, and even I don't buy energy density when I choose a car (or glider),
and neither do pilots looking for a self-launching glider. And obviously, they are finding what
they like, despite the energy density disparity.

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1

9,000 RPM makes quite a racket, no matter the muffler. Have a good
noise canceling headset...

Dan
5J

On 3/4/21 2:07 PM, Martin Gregorie wrote:
On Thu, 04 Mar 2021 11:55:17 -0800, Mark Mocho wrote:

Energy density is the "elephant in the room" that determines a lot about
electric vs. internal combustion. The Tesla S uses a 100 kWh battery
that weighs 1,375 lbs. 100 kWh is approximately the same energy
contained in 2.1 gallons of AvGas. So, you have a 2 gallon capacity
(about 13 lbs.) in a 1,375 lb. container. Makes perfect sense to me.
NOT!

And we aren't even bringing up the environmental impact of producing the
battery and then disposing of it when its life is used up.

Here are some free-wheeling thoughts inspired by what I've read about the
Aptera hybrid road vehicles: the prototype used an all-electric drive
chain connected to a battery with a 40 mile range when fully charged. It
also carried a small ICE generator pack - on ling trips the rig was said
to average 120 mpg.

So, how would a similar set-up work for us?

Say, use a pylon-mounted electric motor coupled to a battery capable of
take-off olus a 2000 ft climb (i.e. a somewhat higher than normal winch
launch) and carry a small ICE generator pack to be run during and after
launch to recharge the battery.

A modern 20cc 2-stroke can knock out 2.5 hp at 9000rpm (around 1.8 kWh,
so with a 40% efficient generator you can recharge the battery at a 0.7
kWh rate from a unit with a guestimated weight of 1.5 Kg (750 g motor
plus the same weight for the generator) plus fuel at around 9,7 kWh/litre
(thats 12 kWh/kg) so something like 1.2 kWh/liter of fuel can be put back
into the battery after launch (assuming motor efficiency 25% and
generator efficiency 40%). Now, scale the system up a bit and use a 200cc
generator set and you've got an equipment weight of 15 kg plus fuel and a
recharge rate of around 12 kWh. Time to recharge a 20 Kwh launch battery
is around 1.7 hours, so a fair time to be listening to the (muffled)
engine behind you, but a much lighter system than a pure electric system
(launch battery + 15kg generator set) would be.

What did I miss?