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Electrified wingsuit from BMW reaches 186MPH on first flight

robbreport.com

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

#131

Post by bjornedstrom »

base698 wrote: post #128
bloaf wrote: post #77

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

It's more active jumpers over their jumping career than just people who try it once. It varies wildly jumper to jumper based on the types of jumps done (cliffs are more deadly than bridges) and how often. Most people jump for a period of 3-6 years and quit. My wife and I were pretty active jumping in the era of wingsuit videos on YouTube. In her first year we had one good friend die and 9 people we'd met or hung out…

Didn't expect to find one here at Hacker News. 698... so you must have started around the early 00:s or thereabouts?

Unfortunately I share your same statistics: I was very active in the early 2010:s and in that period I lost about 10 friends/acquaintances. Since then even more people I've hung out with are gone.

So yeah: wingsuiting is dangerous. But BASE itself can be done "reasonably" safely I think: personally I was always more fond of slider down (low) stuff, like buildings, and in my mind that's a safer sport than wingsuit BASE.

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

#132

Post by jononor »

CrazyCatDog wrote: post #49
Robotbeat wrote: post #28

Earlier quoted context omitted.

You’d be surprised. There are some high-C lithium ion cells, but they’re not as easily available as LiPo. If you need to dump your power over 4-10 minutes or longer at peak power, there are lithium ion cells available. Less than 4 minutes, LiPo is still better for now.

Totally agree. My use case: 3 seconds max (launch), 3 seconds in-flight would be out of sight— total power on time between charges is well below one minute. I’m tempted to guess that this would be the most efficient way of converting electricity in wing suit applications as well.

That is more supercapacitor territory than batteries, especially if you do not require long-term energy storage (can accept relatively high self-discharge). The energy recovery systems in Formula 1 racing (KERS) are examples.

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

#133

Post by tomc1985 »

lopmotr wrote: post #129
tomc1985 wrote: post #123

Earlier quoted context omitted.

> Modern advances in digital sensors/lenses/flashes/post-processing makes everyone able to take professional quality photos. For newspapers, maybe, but the tiny optics on phones rule out a lot of photographic techniques, to say nothing of sensor quality when trying to pull 20+ MP out of a sensor the size of a tab of acid My iPhone 11 Pro still takes crap pictures compared to my FX (or even DX) camera body, and that's…

Of course, otherwise those fancy cameras would have no market and disappear. Just like film is pretty much completely gone now, as are glass plate cameras. The truly inferior tech disappears and what's left fits some extreme niche where it surpasses the cheap consumer stuff in some way. There are things you can do with a PC that you can't with a smartphone too.

That's incredibly optimistic of you to call the PC dead. I really, really, hope (and am pretty sure) that you are wrong

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

#134

Post by dTal »

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.

It's true that big, slow things are, all other things being equal, more efficient than small, fast things. Momentum is mv, but kinetic energy is 1/2 mv^2, so that squared term means it's cheaper to move a lot of mass(m) slowly than a little of it quickly. You can build big, slow ducted fans, but you do hit size limits much earlier than with free props because of the shroud.

HOWEVER, efficiency is maximized when outlet velocity matches airspeed (or you have wasted momentum that will dissipate into heat, when your outlet stream mingles with the rest of the atmosphere). For your slow gliders, a small ducted fan with a high outlet velocity will indeed be quite inefficient. But this guy, traveling at hundreds of mph, needs a propulsion unit with a similarly high outlet velocity. A big, slow thing isn't going to cut it for that. A big, fast thing would, but would also blow their power budget. Within their design constraints, this is pretty close to the optimal solution.[1]

There's also the small matter of free props being horrifically dangerous :)

[1] They've helpfully given us enough information to work out some basic aerodynamics of their fans. At 7.5 Kw each, assuming 90% efficiency each of the motors and ESCs, and eyeballing the duct and hub diameters as 18cm and 8cm each respectively (could be off, here), we should expect an outlet velocity of about 230 mph. The guy reached an airspeed of nearly 190mph, or over 80% of the outlet velocity, so they aren't doing badly at all considering the drag.

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

#135

Post by FabHK »

palijer wrote: post #67
joosters wrote: post #60

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.

I don't think a quadcopter is controllable with 3 engines.

However, a drone designed to carry pax can be designed with redundancy - the Volocopter, for example, has 18 rotors and engines, and can withstand at least 3 failing.

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

#136

Post by FabHK »

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.

I thought efficiency of a fan < 2 counterrotating stacked fans < ducted fan?

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

#137

Post by FabHK »

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?

I liked this course: Introduction to Aeronautical Engineering, by Technical University Delft in the Netherlands, on edX. It assumes basic physics and maths, but then gives a nice overview about all the fundamentals - aerostatics, aerodynamics, propulsion, materials, structure of aircraft, etc.

https://www.edx.org/course/introduction-to-aeronautical-engi...

If you're specifically looking at autonomous flight of drones, then the Udacity Flying Car nano degree is not bad (it contains several mistakes, but takes you through quite some material with neat exercises). It presupposes a bit more maths and programming. I was free (for a month) during the early stages of the pandemic, now I think it's back to normal prices.

https://www.udacity.com/course/flying-car-nanodegree--nd787

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

#138

Post by m0zg »

Meanwhile, Tesla is gobbling up BMW's luxury car marketshare. I mean, this is exciting and all, but as a BMW owner with a 6 year old car, I'd appreciate if there were any non-dumb options in your lineup, BMW. Instead we're getting humongous grilles and wingsuits. How stupid do you think your customers are?

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

#139

Post by FabHK »

bbojan wrote: post #108

Batteries -> electric motors -> ducted fans seems inefficient to me. If I were building this myself I would go with a hybrid rocket engine.

Though electric motors are notoriously efficient (much more so than ICEs), and my understanding was that ducted fans are also efficient (particularly with 2 stacked counterrotating props).

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

#140

Post by FabHK »

peterwwillis wrote: post #44

Nice to see they aren't bothering with social distancing. I mean, sure, they might be spreading a deadly virus, but how else are they gonna talk about how bad-ass that wingsuit flight was? Totally worth killing immunocompromised people.

They're outside and (in the last congratulatory shot) almost all wearing masks. I think that is defensible.
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