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I'm much less optimistic. Even when factoring in the poor thermal efficiency of gas turbines (~30-40%) compared to electric (>90%), the usable specific energy g
by bb123 5mo ago
I'm much less optimistic. Even when factoring in the poor thermal efficiency of gas turbines (~30-40%) compared to electric (>90%), the usable specific energy gap remains immense. Jet-A still delivers roughly 14 times more useful work per kilogram than modern batteries. Removing fuel plumbing and tweaking airframes won't overcome that fundamental physics. Also the issue with the high-altitude efficiency argument is that batteries, unlike liquid fuel, don't lose mass during flight meaning the aircraft to haul its maximum takeoff weight from departure to arrival. It's a double whammy.
- ericd 5mo agoWell, in this case, we don’t need to argue about theory. The Joby has a tested range of 150 miles. They also tested it with hydrogen fuel cells and got >500.
- nDRDY 5mo agoSounds about right. A plane of comparable max take-off weight, a Piper Malibu, has a range of ~1500 miles (with reserve remaining).
- ericd 5mo agoThis isn’t meant to slot into the role of other planes, though, it’s meant for rideshare. It can take off and land on my suburban lawn. There’s a lot to figure out before we can get to that point, so they’re just displace helicopters for the moment, but it can be a lot more. It’s basically the long awaited flying car, in nascent form.
- nradov 5mo agoNo, it can't take off and land on your suburban lawn. The wires and trees overhead would make that ridiculously dangerous, a last resort only for emergencies. Plus they need to recharge for the next flight. These e-VTOL aircraft will operate from dedicated pads.
- ericd 5mo agoJust talking about what they've talked about as goals in interviews. And I'm surprised you're willing to make definitive statements about my lawn, we have a large enough area with none of those obstructions you're talking about, we live on a few acres. And if it's running 20 miles here and there, it can do a few trips before it needs to go somewhere to charge or battery swap. That would cover our trip to our nearest international airport.
- flextheruler 5mo agoDoes your lawn come with an air traffic control tower?
- ericd 5mo agoHeh it doesn't have to be literally on one's own lawn, it could just be a little helipad per community. And my understanding is that the vast majority of private helipads don't have air traffic control - your hospital's roof doesn't have its own air traffic control. Pilots operate under "see and avoid" rules. Use your imagination a little. So much status quo bias here.
- nDRDY 5mo agoWho would want to privately own a community helipad? Sounds like an insurance and liability nightmare. This is an impressive enough achievement, but let's not kid ourselves this is going to revolutionaise suburban or semi-rural transport. Its maximum payload weight (450kg) barely covers 5 passengers with no baggage. It's for hopping from the country club to the golf course.
- nradov 5mo agoIf these e-VTOL aircraft get used for air taxi service at all it's going to be for short hops in denser urban areas. Not in rural areas where people have acres of open land.
- 5mo ago
- nradov 5mo agoRight, so when you factor in the legally required reserve flight time the battery powered Joby is only capable of very short hops. And that's fine, it's still potentially useful on a few routes and newer models will improve over time.
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