A slight design change 6

[Sparweb]

Meet Alice. She's had a facelift and a new wardrobe. I guess she needed to look pretty for her date with DHL.

2018:

2021:

 

[Sparweb]

A quick sketch and scale gives a total wing area of 320 square feet, hence a wing loading of 52 pounds per square foot when loaded at MTOW. That's pretty normal for a "bizjet" or "bizprop" style plane. Don't take that too seriously, though - I just traced the marketing sketch, FWIW.
Roskam notes that higher wing loading translates into a smoother ride for passengers.

With no chemical fuel being burned, then MTOW = MLW.
With no fuel, only controls inside the wing, its internal structure might be very simple.

 

[rb1957]

I hope they put batteries in the wings ... replacing the inertia relief of the fuel.

great observation about MTOW = MLW ... this impacts conversion a/c significantly. Even worse, for conversions, is MTOW is limited MZFW (for wing fuel at least).

another day in paradise, or is paradise one day closer ?

 

[WKTaylor]

RE the large inlets as seen in the front-view photos... there are no corresponding aft view photos showing cooling air exhaust. IN must= OUT.

I wonder if small turbines are being employed on this prototype... to be replaced or made optional... to electric motors?

Regards, Wil Taylor
o Trust - But Verify!
o We believe to be true what we prefer to be true. [Unknown]
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation,Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", Homebuiltairplanes.com forum]

 

[rb1957]

typical engine intakes, there'll be an exhaust at the other end.

But that's "odd" .. aren't these electric engines ? or maybe they're doing a gas engine proof of concept. MagniX do some good work replacing gas engines with electric motors, so I guess space is similar ? oh, see MJ's reply (12th August) to this earlier question of mine. Ok, cooling air for electric engines, and similar exhaust (not shown).

another day in paradise, or is paradise one day closer ?

 

[rb1957]

maybe name should be changed to "Lorina" ... Alice's older sister

another day in paradise, or is paradise one day closer ?

 

[MintJulep]

https://www.thedrive.com/the-war-zo...-for-its-first-flight-in-these-awesome-images

Engine and taxi tests.

 

[rb1957]

Alice "specs" ... check the asterisk against the range ... "no payload".

I admit, a funky, interesting fuselage cross-section. I assume unpressurised.

another day in paradise, or is paradise one day closer ?

 

[RoarkS]

I'll chime in on the motor inlets... provided those are still electric motors in there:

I'll try not to say anything proprietary here but we're talking my game...I've been asked to bid on a few electric powerplants cooling systems. Electric motors get hot. Cooling them with other large current draw items seems to be where all the brainstorm projects started a few years ago, but it doesn't seem to make sense come production prototype designs.

There's a reason almost all aircraft powerplants have been and will probably continue to be air cooled. The air-cooled FW190 was considered "clean" compared to the liquid cooled ME109.

 

[3DDave]

Ultimately all aircraft are air cooled - the advantage of a liquid intermediary is that it allows a more compact power plant to depend on a larger/more effective heat transfer system that can be placed elsewhere.

Recall too that liquid cooling allowed the P-51 to use a radiator system to generate extra thrust, or so I understand. Apparently this was also used in the ME-109, which wasn't as effective due to less optimal flow control. It seems a waste to chuck heat out the back without taking advantage of it.

 

[GregLocock]

aka the Meredith effect.

https://reports.aerade.cranfield.ac.uk/bitstream/handle/1826.2/1425/arc-rm-1683.pdf

Cheers

Greg Locock


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[rb1957]

I wonder how much cooling they get on the ground ? without much airflow ??

but then maybe that's why they're so big ... at altitude it is less of an issue.

another day in paradise, or is paradise one day closer ?

 

[Ng2020]

Electric motors need not idle.

 

[verymadmac]

I guess the critical cooling case is max altitude since the power out is independent of altitude unlike typical piston engines.

There is an interesting ARC report R&M 2498 "The Aerodynamics of the cooling of aircraft Reciprocating Engines" which summaries the UK's WWII experience (never found a digital copy online). One of my take aways from the report is that efficient cooling tends to require lots of space or get premium aerodynamic real estate. Liquid cooling may allow one to move that space to somewhere "cheaper".

in the Liquid verse air cooling discussion, the above report gives some interesting numbers
@100 ft/sec
11.5 lb drag for the air cooled Hawker Tempest II
13.0 lb drag for the Nose radiator for the Hawker Tempest I
11.0 lb drag for the Wing leading edge for the hawker Tempest I
Noting that the airframes just differ in the use of an aircooled engine (Tempest II) or liquid cooled engine (Tempest II).

Do the electric motors require to be warmed up before takeoff?

For an electric airframe with pressurization, are we likely to see engine cooling with venerable geometry inlets / outlets?

 

[BrianPetersen]

Electric motors ordinarily don't care much about their operating temperature, although they do require some cooling in operation. Lithium batteries do care about their operating temperature, best range seems to be 10 - 60 C, and in automotive applications, they require some cooling during operation and definitely during fast-charging. The motor inverter also requires cooling during operation. The cooling loads in terms of kW cooling relative to kW of mechanical power output are nowhere near those of a combustion engine, but also the temperature difference to the surroundings is also nowhere near those of a combustion engine ... it is entirely possible that the volume of cooling air required, and the size of a radiator required, is going to be same-ballpark. Smaller but not drastically so, is automotive practice.

Cabin HVAC and pressurisation is a different situation from turbine-powered aircraft. It's going to need active compression of outside air.

Outside air temp at high altitude is going to be way lower than the temperature the batteries want. It may turn out that during operation, waste heat from the motor and inverter supplies heat to the battery and that loses it to the outside air. Doesn't help with excess battery heat during fast-charging on the ground, though. That will still need active cooling.

 

[rb1957]

that was along my line of thought. ground cooling could be a ground cart.

another day in paradise, or is paradise one day closer ?

 

[rb1957]

I wonder how you ensure the remaining range ? the required reserves ??

sure, not awfully different to fuel but different none the less.

I find "range with zero payload" an interesting point. Payload of these electric planes is a small fraction of total weight (in this case 2500 lbs in a 16500 lbs plane). Does max payload reduce the range by 1/8th ?

another day in paradise, or is paradise one day closer ?

 

[btrueblood]

"I wonder how you ensure the remaining range ? the required reserves ??"

Especially with a 5 year old battery, if my phone is any indicator of the problem.

 

[Ng2020]

Dedicated reserve power supply.

 

[GregLocock]

Would you not come up against the lithium equivalent of peukert's law?

For instance, I can buy relatively cheap batteries that have maximum discharge current of 1C. If I want to discharge at 6C I pay more for my battery, or fit a bigger battery.

By all means reserve power in the main battery, but a separate small battery is tricky. OTOH, I suppose a reserve battery won't be being used for take-off/climb.

Cheers

Greg Locock


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[3DDave]

State of charge prediction has generally been pretty poor. Simple enough to check the voltage, but I've seen batteries that have a no-load voltage that vanishes under a tiny load. Testing under full load only indicates that for that amount of time the battery was able to keep up, but the test is destructive in that the charge that was there is no longer there.

The advantage to fueled aircraft is that generally fuel is burned at a constant rate regardless of the amount of fuel available; the energy per pound of fuel doesn't change if the tank is completely full or nearly empty, whereas in extracting energy from a battery the state-of-charge has a serious affect, both by being difficult to measure and as it is depleted the chemistry adds to the electrical resistance, further decreasing the rate at which energy is extracted. In aircraft that extraction is nearly constant for the cruise portion of the flight which includes running a race-track or diverting. To the advantage of fuel - that reserve is available when the plane is lighter, having lost weight due to fuel burn while batteries are literally becoming dead weight over that same period.

Regulation wise, I don't see that there will be a good method to deal with it. It will have to come from decades of flying and data gathering and all the time the chemistry and construction of batteries will be changing, generally rendering the previous data useless for further predictions. Offsetting that will no doubt be increased fidelity in electrochemistry simulation - similar to how thermal analysis is done now for complex shapes. It will look at ion transport in the battery and the effects of that and temperature and barriers due to already reacted material. There are probably initial studies now and more planned for even larger supercomputers to gnaw through.