Applying Tesla technology to aviation - a 100 seat aircraft with propellers driven by electric motor

[Saghost]

We had sort of a preview of what to expect this week with the fatal Tesla crash in the Netherlands. The battery pack split open and shorting batteries caught fire on the road.

This would be an issue with a 787 crash today, but more batteries would mean a more serious danger.

As opposed to all the burning jet fuel? I'm not really convinced that the batteries represent an additional danger on top of the jet fuel, except for the fire department not having established procedures for handling it yet.

In the crash you referenced, the article I read said that the damage to the cabin from the fire was minimal and that the fire only really affected the situation in that it delayed the rescue folks getting to the driver (who I suspect may have had a heart attack to start the whole chain of events and was likely already dead.)

 

[GSP]

Years ago, when Tesla was working on the Roadster launch, Elon mentioned that he had an idea for a supersonic VTOL pure battery electric aircraft. I was pretty concerned. If Elon thought this to be possible, I thought he must be delusional.

Many years later, during Q&A at an aerospace conference, someone stated that a pure battery electric aircraft (or airliner?) was not possible. Elon interrupted and said it was possible with battery tech at the time. You just had to have a low mass fraction for payload, 10-20% IIRC, and get rid of unnecessary items that add mass and drag, including wings, tail, and control surfaces.

I must say that Elon is the master at thinking out of the box. His airliner would be like a battery electric ducted fan powered Falcon 9, or perhaps a lifting body type aircraft. Control by thrust vectoring (and grid fins?) and using the ducted fan for VTOL.

Intriguing.

GSP

PS. Note how some of these concepts are also used in Elon's hyperloop.

 

[wdolson]

As opposed to all the burning jet fuel? I'm not really convinced that the batteries represent an additional danger on top of the jet fuel, except for the fire department not having established procedures for handling it yet.

I said "more batteries would mean a more serious danger" in which I meant the larger the battery pack, the larger the fire risk in a severe accident compared to smaller battery packs like we have on the Model S today. Any kind of aircraft which got propulsion from batteries would require a much larger battery pack than any car in service today.

In the crash you referenced, the article I read said that the damage to the cabin from the fire was minimal and that the fire only really affected the situation in that it delayed the rescue folks getting to the driver (who I suspect may have had a heart attack to start the whole chain of events and was likely already dead.)

I read there was a small fire in the cabin, but some batteries spilled on the road were burning too and that was the larger fire. Though that was from an article yesterday, more may be known today.

 

[Peter Egan]

We had sort of a preview of what to expect this week with the fatal Tesla crash in the Netherlands. The battery pack split open and shorting batteries caught fire on the road.

This would be an issue with a 787 crash today, but more batteries would mean a more serious danger.

Aeroplanes are designed to evacuated in 90 seconds. Cutting high voltages in a minor crash, where the plane is largely intact, is an important issue. In a major crash, with cells spilled all over the place, the voltages of the cells are down to 3 to 4 volts - fire is caused by spilled fuel and sparks from the friction of the plane hitting the ground.

 

[Peter Egan]

Years ago, when Tesla was working on the Roadster launch, Elon mentioned that he had an idea for a supersonic VTOL pure battery electric aircraft. I was pretty concerned. If Elon thought this to be possible, I thought he must be delusional.

Many years later, during Q&A at an aerospace conference, someone stated that a pure battery electric aircraft (or airliner?) was not possible. Elon interrupted and said it was possible with battery tech at the time. You just had to have a low mass fraction for payload, 10-20% IIRC, and get rid of unnecessary items that add mass and drag, including wings, tail, and control surfaces.

I must say that Elon is the master at thinking out of the box. His airliner would be like a battery electric ducted fan powered Falcon 9, or perhaps a lifting body type aircraft. Control by thrust vectoring (and grid fins?) and using the ducted fan for VTOL.

Intriguing.

GSP

PS. Note how some of these concepts are also used in Elon's hyperloop.

NASA, Boeing, Airbus and small plane manufacturers are all working on electric aircraft. Range is the issue. The portion of the battery/payload capacity taken up by battery grows in proportion to battery range. As aircraft become lighter, more weight can be allocated to battery. It is the way of the world that countries compete to dominate/lead strategic industries. China has made EVs a national priority. Germany's Volkswagan is responding in the wake of dieselgate. China wants to be the third big aircraft manufacturer. It, and Japan, are developing regional jets in the first instance. China recently announced its standardised high-speed train. It's reasonable to expect China to add hybrid aircraft to its programme as it seeks, as in cars, a technological lead. Will the US and Europe resond??

 

[wdolson]

Aeroplanes are designed to evacuated in 90 seconds. Cutting high voltages in a minor crash, where the plane is largely intact, is an important issue. In a major crash, with cells spilled all over the place, the voltages of the cells are down to 3 to 4 volts - fire is caused by spilled fuel and sparks from the friction of the plane hitting the ground.

Burning fuel is a more significant factor than battery fires in an accident with any plane flying today. I was talking about a hybrid plane that had a big battery pack for propulsion. A battery pack over 1 MWh is going to be way more dangerous from fire than the 787's battery pack which is less than 5 KWh. Boeing's design decision was to go with a few large cells rather than a large number of smaller cells. It's much easier to avoid thermal runaway with a lot of smaller cells than with bigger cells. Elon Musk has said that's why Tesla is sticking with the many celled battery pack solution for their cars, even though it makes them more complex.

The problem with battery fires is they are very tough to put out when they go into thermal runaway. The foam they use for aircraft fires will put out the flames, but the batteries will remain dangerously hot and someone can get severely burned stepping on one, or restart a fire by kicking some out from under the foam. It's a different type of fire than jet fuel.

 

[Jdcorbitt3]

The biggest issue would be an inflight fire. We now carry fire bags for fires in laptops and smaller electronics. It is very difficult to fight a class D fire in flight. Doing as previously posted by isolating cells may be an acceptable answer. The cells would need to be thermally isolated from each other. I would love to see it happen.

John

 

[Saghost]

The biggest issue would be an inflight fire. We now carry fire bags for fires in laptops and smaller electronics. It is very difficult to fight a class D fire in flight. Doing as previously posted by isolating cells may be an acceptable answer. The cells would need to be thermally isolated from each other. I would love to see it happen.

John

It seems like the Tesla pack would be a pretty good starting point - keep the individual cells small and individually fused, use an aggressive chemistry with active cooling both to manage cell life and to control/limit thermal events.

Might need to enhance the cooling system, and/or give some sort of cell level emergency cooling (thermally triggered cold pack? Lots of intumescent goo?) for runaway cases.

 

[Peter Egan]

Having proposed a counter-rotating electric powered propeller design, I have perhaps over-reached on the technology front.

http://www.aerospaceamerica.org/Documents/March 2010/Open rotor research revs up_MAR2010.pdf

 

[Peter Egan]

Having proposed a counter-rotating electric powered propeller design, I have perhaps over-reached on the technology front.

http://www.aerospaceamerica.org/Documents/March 2010/Open rotor research revs up_MAR2010.pdf

This link to a Boeing patent for VTOL 100 seat passenger aircraft would indicate that they are thinking of electric fans as a mechanical drive version would be too clunky/heavy, and the engine and motor housings are sized for turboshaft power and electric motor drive.
Patent Images

 

[Peter Egan]

This attachment of a Boeing patent for VTOL 100 seat passenger aircraft would indicate that they are thinking of electric fans as a mechanical drive version would be too clunky/heavy, and the engine and motor housings are sized for turboshaft power and electric motor drive.

 

[jkn]

The problem with battery fires is they are very tough to put out when they go into thermal runaway. The foam they use for aircraft fires will put out the flames, but the batteries will remain dangerously hot and someone can get severely burned stepping on one, or restart a fire by kicking some out from under the foam. It's a different type of fire than jet fuel.

I believe its even worse: When battery is burning reactions happen inside closed cell. No air needed. Foam will add heat insulation, so reactions will be faster. Some flammable gases exit and burn outside of the cell. Foam might stop that.

 

[Peter Egan]

I believe its even worse: When battery is burning reactions happen inside closed cell. No air needed. Foam will add heat insulation, so reactions will be faster. Some flammable gases exit and burn outside of the cell. Foam might stop that.

Hopefully, Telsa has this problem beat with the size of its cells - 21700. A runaway in one cell would be cause for module to be shut down, but it should not cause neighbouring cells to "burn" - only get hot.

 

[Saghost]

Hopefully, Telsa has this problem beat with the size of its cells - 21700. A runaway in one cell would be cause for module to be shut down, but it should not cause neighbouring cells to "burn" - only get hot.

I'm not quite sure how you're expecting a module to be "shut down" - they are generally hardwired together.

On the other hand, you're ignoring two different pieces of protection Tesla has for their packs:

Every cell has an individual fusible link ultrasonically welded between it and the rest of the pack. If the cell were to short (the only likely cause of thermal runaway I'm aware of,) the links will pop, isolating the cell from the pack and reducing the module's capacity slightly but leaving it otherwise unaffected.

Tesla also filed a patent for using an intumescent goo in the pack - a material that undergoes an endothermic reaction when heated, sucking the heat out of the shorted cell. I don't know for certain if they are using it or not.

 

[Peter Egan]

I'm not quite sure how you're expecting a module to be "shut down" - they are generally hardwired together.

On the other hand, you're ignoring two different pieces of protection Tesla has for their packs:

Every cell has an individual fusible link ultrasonically welded between it and the rest of the pack. If the cell were to short (the only likely cause of thermal runaway I'm aware of,) the links will pop, isolating the cell from the pack and reducing the module's capacity slightly but leaving it otherwise unaffected.

Tesla also filed a patent for using an intumescent goo in the pack - a material that undergoes an endothermic reaction when heated, sucking the heat out of the shorted cell. I don't know for certain if they are using it or not.

The aviation industry will surely love that approach to battery module protection. There are a lot of short range aviation applications for under 100 km with vertical. or very short runway take-off and landing. Pure electric aircraft with current technology surely have some significant applications capable of getting an all-electric aircraft industry off the ground.

 

[jkn]

I'm not quite sure how you're expecting a module to be "shut down" - they are generally hardwired together.

On the other hand, you're ignoring two different pieces of protection Tesla has for their packs:

Every cell has an individual fusible link ultrasonically welded between it and the rest of the pack. If the cell were to short (the only likely cause of thermal runaway I'm aware of,) the links will pop, isolating the cell from the pack and reducing the module's capacity slightly but leaving it otherwise unaffected.

Tesla also filed a patent for using an intumescent goo in the pack - a material that undergoes an endothermic reaction when heated, sucking the heat out of the shorted cell. I don't know for certain if they are using it or not.

We have seen that this is not always enough. I don't know, if it is safe enough aviation. Debris on runaway destroyed a Concord.

 

[voyager]

Wouldn't a lifting body type plane, in which the weight of the batteries are offset by the plane's superior lift capacities at relativey slow speed make sense? The only tradeoff would be slower speeds: 400 km/h maximum. But for short-distance flying, for instance in Western Europe, that wouldn't be that much of a problem. It would still beat the train and the car handsomely.

 

[Saghost]

Wouldn't a lifting body type plane, in which the weight of the batteries are offset by the plane's superior lift capacities at relativey slow speed make sense? The only tradeoff would be slower speeds: 400 km/h maximum. But for short-distance flying, for instance in Western Europe, that wouldn't be that much of a problem. It would still beat the train and the car handsomely.

Lifting bodies aren't inherently speed limited - actually, the wave-rider forms I've seen for hypersonic aircraft are pretty much lifting bodies. It's actually the other end of the spectrum that's the problem.

Traditional high lift devices for takeoff and landing are attached to the trailing edge of the wing, and generate large pitching moments (they tend to push the nose down when used.) A conventional aircraft has the wing trailing edge well forward, and a large horizontal tail aft to apply a nose up moment to compensate.

A flying wing or lifting body doesn't have that luxury - the trailing edge of the wing is much further aft, and there's nothing behind it. Thus, they generally don't use landing flaps at all, and have the resulting higher takeoff, landing, and stall speeds.

 

[ggr]

Lifting bodies aren't inherently speed limited - actually, the wave-rider forms I've seen for hypersonic aircraft are pretty much lifting bodies. It's actually the other end of the spectrum that's the problem.

Traditional high lift devices for takeoff and landing are attached to the trailing edge of the wing, and generate large pitching moments (they tend to push the nose down when used.) A conventional aircraft has the wing trailing edge well forward, and a large horizontal tail aft to apply a nose up moment to compensate.

A flying wing or lifting body doesn't have that luxury - the trailing edge of the wing is much further aft, and there's nothing behind it. Thus, they generally don't use landing flaps at all, and have the resulting higher takeoff, landing, and stall speeds.

I took him to mean like the Helium-filled semi-blimp lifting body.
Up Close: Lockheed Martin’s LMH-1 Hybrid Airship

 

[Saghost]

I took him to mean like the Helium-filled semi-blimp lifting body.
Up Close: Lockheed Martin’s LMH-1 Hybrid Airship

You might be right - that might explain the superior lifting at low speed comment that I didn't understand.

If so, it's totally different from the subject of the thread.

Since blimp type solutions are mostly fair weather flyers anyway, I tend to think one driven by electric motors would be a good candidate for solar power from the upper part of the outer cowling.