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Electrified wingsuit from BMW reaches 186MPH on first flight

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Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#111

Post by henrikschroder »

Robotbeat wrote: post #18
Hnrobert42 wrote: post #17

Earlier quoted context omitted.

If you are so inclined to answer, I’d live to know why lithium batteries and not some other form of battery? That is, do other elements not have the right properties? Are they too rare? Are they dangerous? You sort of answer a bit in your last paragraph. Why did it take until now to get to lithium batteries? Why way NiCad the thing before? Will lithium continue to dominate, or are there other competitive solutions ju…

The periodic table is limited. Of all metals, lithium is the lightest. It also has the highest mass-specific conductivity and the highest chemical specific energy of all the metals. Hydrogen is not a solid or a liquid at room temperature and is also too volumetrically in-dense.

I have never really understood the hydrogen hype train, because liquid hydrogen is terrible in so many ways.

A bucket of gasoline contains more hydrogen atoms than a bucket of liquid hydrogen, it contains more chemical energy, and you can actually keep it in a bucket at room temperature without anything terrible happening.

Sure, liquid hydrogen has a lot of energy by weight, but energy storage needs to be good by weight and by volume, and hydrogen is terrible by volume.

There are cases for using hydrogen as your energy storage, but if your thing is smaller than a truck, it's probably not one of them. There's just so much wishful thinking around.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#112

Post by chrisweekly »

Retric wrote: post #27
freeflight wrote: post #10

Earlier quoted context omitted.

Tho that was not what was tested, this is about having additional thrust to regain altitude and fly longer distances: > “I found the idea of being able to jump from my local mountain wearing the wingsuit and land in my garden fascinating.”

Sure, I just find it funny how in most cases 180MPH is fast, but that’s about the minimum speed for horizontal wingsuit flight. You really can strap a get engine to a brick and get it to fly, but you can’t stick a jet engine to a brick and get it to fly slowly. EX: F-15 landed safely with just one wing. A little cough propaganda, but still interesting: https://www.youtube.com/watch?v=M359poNjvVA .

IIRC terminal velocity for a skydiver in free-fall is approx 180mph. (It's at least in that vicinity.) So the direction of "flight" certainly matters a lot in making sense of numbers.

Also, when I was in 5th or 6th grade (over 30 years ago) I was obsessed with the F-15. Talk about thrust:weight ratio. The idea that you could take off, point the nose to vertical, and accelerate past the speed of sound, then level off and get to mach 2.4 or so... simply amazing machines.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#113

Post by 3princip »

JKCalhoun wrote: post #53
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…

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…

One could argue that the increase in hardware performance of computers has led to the art of software design falling by the wayside. Horribly inefficient software runs because the hardware performance hides the truth under the hood.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#114

Post by bargle0 »

joosters wrote: post #60
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…

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…

Most quad copter blades won’t go through your skull:

https://abcnews.go.com/US/minute-mechanical-error-led-teens-...

Proper helicopters also require a complicated control linkage on the main rotor and a separate tail rotor. Quad copters (and other multi-blade devices) only need to modulate power to the rotors for control.

I would never ride a quad copter, but they’re better for unmanned use.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#116

Post by robotresearcher »

Diggsey wrote: post #75
palijer wrote: post #67

Earlier quoted context omitted.

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.

With a helicopter, even if you lose the motor (lift) you still have control by adjusting the pitch, angle and ratio of the blades. A quadcopter depends on the motors for any control. While it is possible to regain control after a single motor failure on a quadcopter, it's extremely difficult and not something a human pilot could do, so you'd be relying on software. Also, if you don't detect the failure instantly, the…

Multirotor designs are not limited to 4 motors. You can add more for redundancy. Four is common because it’s the smallest number that has good control characteristics.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#118

Post by Technically »

JKCalhoun wrote: post #53
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…

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 have now met someone who would be unironically mad at Buzz Lightyear in Toy Story for merely "pretending" to fly.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#119

Post by robotresearcher »

henrikschroder wrote: post #111
Robotbeat wrote: post #18

Earlier quoted context omitted.

The periodic table is limited. Of all metals, lithium is the lightest. It also has the highest mass-specific conductivity and the highest chemical specific energy of all the metals. Hydrogen is not a solid or a liquid at room temperature and is also too volumetrically in-dense.

I have never really understood the hydrogen hype train, because liquid hydrogen is terrible in so many ways. A bucket of gasoline contains more hydrogen atoms than a bucket of liquid hydrogen, it contains more chemical energy, and you can actually keep it in a bucket at room temperature without anything terrible happening. Sure, liquid hydrogen has a lot of energy by weight, but energy storage needs to be good by wei…

You are absolutely right. The great appeal of hydrogen is that you can get it straightforwardly from water and it oxidizes back to water. Hard to imagine a cleaner energy cycle, subject to the extraction energy source but that’s in common with the alternatives.

Pretty much everything else about it is bad. Shame.

Re: Electrified wingsuit from BMW reaches 186MPH on first flight

#120

Post by jasonwatkinspdx »

weddpros wrote: post #23
wiradikusuma wrote: post #5

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)

No, that's not even remotely some sort of design rule. Business jets commonly have their engines mounted above the wings. Doing so can enhance lift in some situations. Here's one of Boeing's models using this idea to enhance the lift of a blended wing body: https://www.youtube.com/watch?v=28blrKKg0Uo
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