Jet propulsion by microwave air plasma in the atmosphere

[YNM]

2 hours ago, mikegarrison said:

You may also hear about a "basket of measures", which is ICAO-speak for saying they are working on a bunch of different pathways toward reducing aviation climate impact rather than waiting for one magic bullet that will solve everything at once.

It is definitely relatively faster than solving the problems of using a different type of energy storage completely, yes.

I guess it'll be up to each individual countries/regions then. To the best of my knowledge here we at most use bio-jetfuel, but again how much is coming from those newly opened plantations one is left to wonder. Maybe in another country they can do it better from waste, in yet others they might have other biological sources that is less destructive in the creation/establishment process.

Electricity isn't necessarily made "cleanly" either - cue us banning export of coal then somehow went ahead and use it ourselves - although it is much more open to various sources than flamable fuel.

[magnemoe]

16 hours ago, mikegarrison said:

And thus you have just described SAF. (Sustainable Aviation Fuel.)

While everybody wants to talk about electric airplanes and hydrogen and whatever else, generally speaking most of the real focus of mitigating aviation climate effects are going into SAF efforts.

Another solution is to ignore it outside of short haul flights who can be done electrical and who also reduce maintenance for these flight who tend to be marginal anyway. 
Perfect is the main enemy of good enough. 
We reduce the co2 footprint to 10-20% or pay 5 times more to eliminating the natural gas surge power plants and get 0% and then  getting voted out after the blackout during an bad year. 
Yes if you can make methanol from wood waste cheaply this change stuff hard. 

Electrical cars was pretty common 110 years ago. While a bit low performance they was simple to use, no crank handle and double clutching and all the other stuff with 1910 engines.  
But as IC engines improved they fell behind. Today the only downside of an hybrid is the increased cost. Neighbor of my boss had the gasoline in his hybrid car go bad as it was too old  he charged all the time and mostly did short trips downtown, then he want to visit some relatives.  

[DDE]

14 hours ago, magnemoe said:

Today the only downside of an hybrid is the increased cost.

The most frequent opposition I hear is the reliability of batteries - especially modern high-capacity ones - in subzero conditions.

14 hours ago, magnemoe said:

short haul flights

Ah, the thing that makes me go choo-choo.

[sevenperforce]

Setting aside this microwave plasma jet, what about conventional props?

Propellers can reach 92% efficiency at converting shaft torque into thrust. For an ICE or turboprop engine, torque at the shaft is only a fraction of the available chemical energy due to friction and Carnot inefficiencies, but a direct-drive electric motor can exceed 95% efficiency. 

I've only ever flown two planes, one of which was the ever-popular Cessna 172 Skyhawk. Specifications for the Cessna 172R:

• Fuel capacity: 163 kg
• Engine: Lycoming IO-360-L2A, four cylinders, 120 kW
• Engine weight: 117 kg
• Cruise speed: 63 m/s
• Fuel consumption at cruise: 35 kg per hour
• Maximum cruise duration: 4.6 hours
• Theoretical max cruising range: 1000 km

A single Tesla Model S motor masses just 32 kg and pushes 270 kW shaft power. A linear downscale to 120 kW would require just 14 kg of engine. If we use that saved engine weight for more batteries then our new "fuel capacity" in the same plane becomes 266 kg. To account for 95% motor efficiency and 92% thrust efficiency, we can just act as though our battery weight budget is just 232 kg.

That mass budget gives us only 41 kWh of battery power, which will give us a pitiful 21 minutes of cruise and a range of just 80 km.

Of course, if you could use a lithium-air battery at an effective 18 MJ/kg (5 kWh/kg), that mass budget would get you 1,160 kWh which is enough for a theoretical 9.6 hours of cruise, more than double what a Cessna 172 can do. So that would be quite promising.

[magnemoe]

On 3/28/2021 at 3:48 PM, DDE said:

The most frequent opposition I hear is the reliability of batteries - especially modern high-capacity ones - in subzero conditions.

Ah, the thing that makes me go choo-choo.

That the batteries has lower capacity then cold is an well known problem, now this is not as much a problem on an hybrid as it switches to using fuel while an electrical car might not have enough charge to reach it destination.  Have not heard the cold harm the batteries, lots of electrical cars here in Norway so this would be well known. 

 

[mikegarrison]

4 hours ago, sevenperforce said:

Setting aside this microwave plasma jet, what about conventional props?

Propellers can reach 92% efficiency at converting shaft torque into thrust. For an ICE or turboprop engine, torque at the shaft is only a fraction of the available chemical energy due to friction and Carnot inefficiencies, but a direct-drive electric motor can exceed 95% efficiency. 

I've only ever flown two planes, one of which was the ever-popular Cessna 172 Skyhawk. Specifications for the Cessna 172R:

• Fuel capacity: 163 kg
• Engine: Lycoming IO-360-L2A, four cylinders, 120 kW
• Engine weight: 117 kg
• Cruise speed: 63 m/s
• Fuel consumption at cruise: 35 kg per hour
• Maximum cruise duration: 4.6 hours
• Theoretical max cruising range: 1000 km

A single Tesla Model S motor masses just 32 kg and pushes 270 kW shaft power. A linear downscale to 120 kW would require just 14 kg of engine. If we use that saved engine weight for more batteries then our new "fuel capacity" in the same plane becomes 266 kg. To account for 95% motor efficiency and 92% thrust efficiency, we can just act as though our battery weight budget is just 232 kg.

That mass budget gives us only 41 kWh of battery power, which will give us a pitiful 21 minutes of cruise and a range of just 80 km.

Of course, if you could use a lithium-air battery at an effective 18 MJ/kg (5 kWh/kg), that mass budget would get you 1,160 kWh which is enough for a theoretical 9.6 hours of cruise, more than double what a Cessna 172 can do. So that would be quite promising.

A lot of things are "quite promising" at very low TRL. That's how TRL works.

One thing to remember (and I'm not sure if you accounted for it) is that the Breguet Range Equation assumes that you burn fuel along the way, thus getting lighter and lighter. That doesn't happen with batteries.

[magnemoe]

1 hour ago, mikegarrison said:

A lot of things are "quite promising" at very low TRL. That's how TRL works.

One thing to remember (and I'm not sure if you accounted for it) is that the Breguet Range Equation assumes that you burn fuel along the way, thus getting lighter and lighter. That doesn't happen with batteries.

This is true, however metal air batteries are jackpot level gamechanger, so you want to try to make it. Low chance but high reward. 
And obviously the structure for needing to get air everywhere inside the battery will add weight and bulk. 

An metal air battery will be heavier as it charges out. Long range planes has to dump or burn fuel to land, shorter ranged ones does not. 
Was in one plane going from south to north of Norway, around 2000 km it could not retract its nose gear so it just landed and they fixed it and we left. 
But in an US to Europe flight they had problems with the navigation system, could not cross the Atlantic and had to return. They had to burn lots of extra fuel.
Now-day you don't dump fuel unless its something who make you need to land now like engine out you burn it in engine. 

[mikegarrison]

3 hours ago, magnemoe said:

But in an US to Europe flight they had problems with the navigation system, could not cross the Atlantic and had to return. They had to burn lots of extra fuel.