81–90 of 203 posts
Base jumping has a ridiculously high fatality rate (~1 in 60 people who try it die). I wonder if adding engines makes it safer or less safe. https://en.wikipedia.org/wiki/BASE_jumping#Safety
in this vid he's jumping out at 10k ft which makes it closer to skydiving.
Something seems suspect here. There is just no way that small unit could generate near enough thrust to make a real difference. I think we need to look deeper into this claim
Earlier quoted context omitted.
It's a matter of scaling laws. You don't see insects or hummingbirds gliding anywhere, small things fly differently.
And dangerously. There is no redundancy.
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 proportional to the surface of the moving object. Divide an animal’s length, breadth, and height each by ten; its weight is reduced to a thousandth, but its surface only a hundredth. So the resistance to falling in the case of the small animal is relatively ten times greater than the driving force.
An insect, therefore, is not afraid of gravity; it can fall without danger, and can cling to the ceiling with remarkably little trouble.”
(These wing suits are man-sized, so they would break their wearer on impact)
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…
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…
I don't understand the lasting appeal of quadcopters in particular. We can build remote-controlled 'normal' helicopters that have fantastic performance and much greater efficiency (no need for 4x the motors and stubby blades). The only downside I understand is that R/C helicopters are very difficult to fly, but that should be straightforward to overcome by putting a basic computer + sensors between the controller and…
I saw this on the news a couple of days ago. It stated that flight time is about five minutes before the battery runs out. That time in "flight" doesn't seem much different than the time it would take to plummet to your death. The only material difference seems to be the not dying part.
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…
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…
You are not wrong. That is a valid lament.
But, this is the definition (or at least a very common result) of innovation/progress.
Tech/automation advances to the point that non-artists, non-experts can do a thing competently or even expertly. Photography use to require expensive equipment, skill, and knowledge. Modern advances in digital sensors/lenses/flashes/post-processing makes everyone able to take professional quality photos. There is, of course still masters and talented artists that surpass. But the floor for everyone has been brought up to expert level at least.
Same for film/video, driving, complex maths, and many more.
Does anyone know why it's not strapped at the back like a jetpack?
I guess extrados is much more important than intrados in terms of aerodynamics (planes "never" carry anything above their wings, only below them)
Earlier quoted context omitted.
I don't understand the lasting appeal of quadcopters in particular. We can build remote-controlled 'normal' helicopters that have fantastic performance and much greater efficiency (no need for 4x the motors and stubby blades). The only downside I understand is that R/C helicopters are very difficult to fly, but that should be straightforward to overcome by putting a basic computer + sensors between the controller and…
Having 4 weaker motors is generally safer than one big one if something were to hit it, and you can shorten the blades because the lift is spread across 4x as many blades. Multiple motors is good as well for any motor failures, as quads (if they're well designed) can fly after even multiple motor failures.