5 ms·
> Powered entirely by batteries, X1 used approximately $5 worth of electricity during its first flight It's fun to look at the arithmetic behind this to pull o
by danans 1mo ago
> Powered entirely by batteries, X1 used approximately $5 worth of electricity during its first flight
It's fun to look at the arithmetic behind this to pull out the assumptions. To lift a 25000 lb mass 1100 ft in the air requires just over 10kWh, but that's assuming no air resistance or friction, so let's triple the energy needed to 30 KWh.
Let's add another 10 kWh for forward distance covered (assuming it was mostly gliding). Then let's pad it up to 50kWh for anything else. If they say that was $5 in electricity that implies an electricity price of $0.10/kWh, which is possible with utility scale solar.
I'd guess the actual flight time was only 10 of the 27 minutes, 30 kWh used over 10 minutes is 300kW of peak power.
300kW seems very low compared to equivalent jet powered planes, which output an order of magnitude more power for a 30 seater plane. Even if the electric drivetrain is far more efficient than a jet engine it stretches credulity.
Which of my numbers is off?
- learn_more 1mo agoI don't believe the $5 cost either.
- jmaw 1mo agoOoo, sneaky. Not being familiar with flight verbiage, I didn't catch the "27 minute mission" being different than a 27 minute long flight!
- coryrc 1mo agoThe jet planes are flying much higher and are loaded; I'm assuming this one was empty. That would account for the power discrepancy. Finally, I think you might be still high on the power cost. $.10/kwh is retail cost in the PNW, they might be, um, bullshitting a little and have purchased power at a very good rate at a particular time just so they could say $5. They didn't say every flight would be $5. So energy could have been 3x more than you estimated.
- SECProto 1mo ago> I'd guess the actual flight time was only 10 of the 27 minutes, 30 kWh used over 10 minutes is 300kW of peak power I would note this line from the press release: > its all-electric propulsion system delivered more than one megawatt of power. I assume this was peak during takeoff.
- quickthrowman 1mo agoPlanes still need like half throttle to maintain altitude, that’s why airplane engines are rebuilt every few thousand hours vs lasting hundreds of thousands of miles (tens of thousands of hours) for a car engine that only uses a small fraction of its power to keep a car moving.
- SECProto 1mo ago> Planes still need like half throttle to maintain altitude, Yes, bit less than half, but anyway that is exactly why I said takeoff would be the peak power output. > that’s why airplane engines are rebuilt every few thousand hours vs lasting hundreds of thousands of miles (tens of thousands of hours) for a car engine that only uses a small fraction of its power to keep a car moving. Ratio of max power to average power is very low on the list of reasons why a gas turbine engined plane needs maintenance more frequently than a piston engined car.
- quickthrowman 1mo ago> Ratio of max power to average power is very low on the list of reasons why a gas turbine engined plane needs maintenance more frequently than a piston engined car. I meant for the comparison to be between an internal combustion engine in a car and an air-cooled piston engine in a plane, I should’ve clarified in my post. I’m amazed we even figured out how to make reliable gas turbines (single crystal blades still astound me) so any required maintenance makes sense, they operate at the edge of engineering in a way that most machines don’t.
- deleted 1mo ago[deleted]