Posted on 09/19/2021 4:14:52 PM PDT by American Number 181269513
Rolls-Royce Aerospace makes jet engines that power many of the world’s airplanes. While they are state of the art in terms of efficiency, they also leave a lot of greenhouse gas emissions in their wake.
The company has been a leader in developing electric propulsion systems for airplanes in order to help lead the world forward into a future of zero-emissions flight. Getting there will involve lots of innovations. The major hurdle is that batteries have a much lower energy density per unit of weight than jet fuel.
Let’s dig into that a bit. According to JetPack Aviation, a liter of jet fuel has an energy density of 9.6 kWh and weighs about 0.8 kilograms. That translates to 12 kWh per kilogram. In comparison, some of the best lithium-ion batteries have an energy density of 265 Wh per kilogram. The net result? Jet fuel has almost 50 times more energy available per kilogram to power an airplane than batteries do.
But the analysis doesn’t stop there. While jet fuel is energy dense, even the best combustion engines are not all that efficient at converting that energy into forward motion. JetPack says the inefficiency of internal combustion means that 1000 pounds (453.59 kg) of jet fuel yields only about 14 times more power than 1000 lb (453.59 kg) of batteries. A lot of that wasted energy goes out the back of the engine and into the atmosphere.
The net result is the “fuel load” for an electric airplane will be much greater than it would be for a conventional jet aircraft. In point of fact, cramming enough batteries into an airplane to make it fly leaves precious little carrying capacity for cargo and passengers, let alone a pilot.
Rolls-Royce Aerospace has been hard at work developing an electric airplane that can fly faster than 300 mph (that’s 483 km/h for those who insist on using the metric system), making it the fastest electric airplane ever built. This week, the finished plane made its first sustained flight. It was in the air for 15 minutes. I leave it to you to convert that to parsecs if you wish. And if you think 15 minutes isn’t very long, remember Wilbur and Orville Wright’s first powered flight at Kitty Hawk lasted a mere 12 seconds and that led to some pretty amazing things.
Rolls-Royce Aerospace says the test flight is “the beginning of an intensive flight testing phase in which we will be collecting valuable performance data on the aircraft’s electrical power and propulsion system,” according to Engadget. The company claims the single seat airplane has “the most power-dense battery pack every assembled for an aircraft,” but gives no specifics. It uses a 6,000 cell battery pack with a three-motor powertrain that currently delivers 400 kW (500+ horsepower).
The flight comes about a year after the originally scheduled takeoff and about six months after taxi trials. Rolls-Royce is developing an air taxi with aircraft manufacturer Tecnam with the goal of delivering an “all-electric passenger aircraft for the commuter market.” It has also worked with Siemens and Airbus on another e-plane concept.
The project is being funded by the Aerospace Technology Institute and the UK government as a preliminary step toward creating all-electric passenger planes. “This is not only about breaking a world record; the advanced battery and propulsion technology developed for this program has exciting applications for the Urban Air Mobility market and can help make ‘jet zero’ a reality,” says Rolls-Royce CEO Warren East.
Eviation has already created a production prototype of a 9 passenger electric commuter plane with a range of 440 nautical miles (815 km) and a cruising speed of 220 knots (407.44 km/h, 253 mph, or 317 feet per second, if you prefer). United Airlines has also invested in Swedish startup Heart Aerospace and ordered 100 of its electric short-haul passenger planes to be delivered by the end of this decade.
Electric flight is coming, maybe not tomorrow, but soon. Batteries with higher energy densities will be the key that unlocks their potential. Air travel accounts for about 7% of global emissions, so anything that reduces the amount of emissions from aircraft is welcome. Our children will surely fly in electric planes and find nothing remarkable about doing so.
Propellers - is that the latest greatest invention?
Nothing like some govt gravy to keep your engineers on the payroll while commercial sales are sucking bilgewater.
No way I’m getting on an electric airplane, no way, no how.
“It was in the air for 15 minutes. I leave it to you to convert that to parsecs if you wish.”
Parsecs is distance, not time.
“No way I’m getting on an electric airplane, no way, no how.”
Why not?
Not a Star Wars fan we see. Han Solo can make the The Kessel Run in 12 parsecs.
That pissed ne of when I was in engineering classes. I learned a parsec was 3.26 ly, and it ruined my Star Wars enjoyment...
Not close to Jar Jar Binks, or those woke that three dumpster fire movies.
’Cos I’m leavin’ on an e-planeNope; doesn’t work.
Don’t know when I’ll be back again …
The novel said “twelve standard timeparts” instead.
I wasn’t “in the know”.
Thank you.
No fuel fluid dynamics.
A thousand points of failure reduced to 4 connections to the drive motor.
Battery stability and charge analytics at near perfect reliability.
I’m in.
In fact, as a former hang glider pilot I would drop my fear of combustion engines and learn to fly one of these.
Want one.
Props in modern propfan configuration are twice as fuel efficient as turbines. At subsonic speeds the higher the bypass ratio the more fuel.efficient the engine is at cruising speed. This is why you are ever larger success fans on the fronts of turbines gas generators. This is also why the 737 max 8 with is much larger fans is so much more fuel efficient than the prior gen 737.
Propfans have a 50+ bypass ratio and can cause at mach .8 the same speeds as ducted fans do. So yes modern sweeped propellers are cutting edge technology. The challenge has been noise the blade tips at take off go supersonic and the thousands of sonicbooms per second are extremely loud. Duct fans also go supersonic at takeoff power you can hear this same effect as that loud droning sound from the engines at takeoff that’s tapers off as you get to cruising speed and the fan slows to subsonic tip speeds. 737 max engines have a very loud takeoff drone to them due to the much larger carbon fiber fan diameter the engine duct traps a good amount of this noise but not all of it.
Look at the specs on this vs a ducted fan of equal thrust.
https://en.m.wikipedia.org/wiki/Pratt_%26_Whitney/Allison_578-DX
“Look at the specs on this”
The picture looks like a conventional prop in back of a turbo engine. How’s this different from a turboprop, except for the fancy looking blades and a 2nd set of blades and the blades being in back of the engine like they were on the B36?
Let’s dig into that a bit. According to JetPack Aviation, a liter of jet fuel has an energy density of 9.6 kWh and weighs about 0.8 kilograms. That translates to 12 kWh per kilogram. In comparison, some of the best lithium-ion batteries have an energy density of 265 Wh per kilogram. The net result? Jet fuel has almost 50 times more energy available per kilogram to power an airplane than batteries do.
The same applies for electric cars too. Hauling all that weight around is not free. Also batteries put out less and less energy as they age. But they never weight less. Compare that to liquid fuel. As you use it up it weighs less and less.
Just one on many reasons why electric vehicles make no sense.
Electric motors have peak power at low rpms I bet the STOL performance of this plane is like a Tesla car off the line. Give me a ESTOL capable of a 300 to 500 ft take off run and I can change it from my roof panels for free vs $6.98 gal for 100ULL at local airport. A 400 mile IFR range with reserve puts all my favorite fishing and hunting spots a single hop away. Cover the wings with thin film solar panels instead of paint and also pack some thin film roll out solar panels and charge while you relax. It’s like taking a petrol pump with you to the bush.
https://flightaware.com/resources/airport/KADS/services/FBO/Atlantic_Aviation_Addison
Put another way, in order to "fill" (recharge) an electric car at anything like the rate that one fills the tank with liquid fuel, you would need the equivalent of a diesel electric locomotive engine for each pump at the station. For a station with eight pumps, that's 32,000 horsepower if they're all in operation at the same time.
That means that an eight-pump station would need a 15 megawatt electric supply for a maximum-load scenario.
That's if it were possible to charge a battery pack as quickly as one can transfer energy in liquid form.
Those numbers assume automotive gasoline engine efficiency of 30%, which is a bit optimistic.
Don't even ask about the size of the cables that would be required to carry the necessary amperage.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.