Electrified wingsuit from BMW reaches 186MPH on first flight

Post by loeg » Sun, Nov 15, 2020, 6:04 PM UTC

throw0101a wrote: post #55

JKCalhoun wrote: post #53

Earlier quoted context omitted.

Allow me my cynicism (this is HN after all): the rise of electric R/C planes and "foamies" has been a fascinating change in the model-airplane hobby but at the same time it has shown that you can practically put an electric motor + lithium cell on anything and it will "fly". So much so that I feel like the art/science of aerodynamics in modeling has fallen by the wayside. Your run of the mill quadcopter is an ideal e…

> Your run of the mill quadcopter is an ideal example of just throwing together motors + batteries + tech and getting a flying machine out of it. There's the old saw that airplanes fly using lift, but helicopters fly by beating the air into submission.

Post by gorbypark » Sun, Nov 15, 2020, 6:12 PM UTC

JohnJamesRambo wrote: post #93

Robotbeat wrote: post #12

Lithium-based batteries (and associated tech) are to the 21st century what the internal combustion engine was to the 20th century and what the steam engine was to the 19th century. There’s a ~90% chance you’re using a device powered by a lithium chemistry battery to read this right now (laptop or tablet or phone). The smartphone alone (enabled by lithium based batteries) has transformed the world. Lithium-based batte…

>after another few decades of battery chemistry improvement How do you know we aren't near the end of what is possible with batteries already? I assume that people in the steam and internal combustion era thought things would just keep improving forever as well.

Post by melvinroest » Sun, Nov 15, 2020, 6:16 PM UTC

thimkerbell wrote: post #74

CrazyCatDog wrote: post #14

An electric ducted fan (EDF) is highly inefficient, had they put similar wattage through a gearbox to say a folding prop, efficiency may have doubled (albeit an admittedly more onerous form factor). This is just the beginning of electric assist single passenger flight! Reference: plenty of experience pushing 8KW+ through 2KG RC gliders (F5B) and far slower EDF models.

If someone wanted to learn all this stuff in a "for dummies" class, what course would they look for, among the MOOCs?

Post by Robotbeat » Sun, Nov 15, 2020, 6:20 PM UTC

Hnrobert42 wrote: post #79

CrazyCatDog wrote: post #19

Earlier quoted context omitted.

NiCd is actually more capable than NiMh, but suffers from memory issues (capacity decreases significantly if not carefully discharged and recharged; ie you cannot “top them off” without sacrificing capacity. Again, speaking from my lived experience, NiCd pushed to the limit resulted in many gnarly fires in high performance RC use, NiMh was never a contender given low output (again low discharge rates). LiPo is king h…

What about lithium and memory? Do lithium batteries have big memory issues, or is all the stuff rattling around in my head about batteries having memories mostly because I grew up when NiCd and NiMh were all the rage?

Post by Kye » Sun, Nov 15, 2020, 6:28 PM UTC

dmurray wrote: post #95

Someone wrote: post #84

Earlier quoted context omitted.

For insects, hummingbirds, and quadcopters of similar size, there’s no danger in dropping from the sky. J.S. Haldane in “on being the right size”: “You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes. For the resistance presented to movement by the air is…

> A rat is killed, a man is broken, a horse splashes. I had thought that cats could fall from any height safely, but that's not quite true: observational studies suggest [0] they have a 50% or 90% survival rate from terminal-velocity height onto hard surfaces, but not without injury. Still, I'd expect a rat could also "walk away". It's quite a lot smaller than a cat, though it may lack other evolutionary adaptations…