/diy/ - Do It Yourself

>>1182235
>Is there any way to leverage very high RPM to generate thrust?
Thrust, yes. /efficient/ thrust, no.
>Is there any configuration where small diameter ducted fans can generate efficient thrust?
No. It's physically impossible. Small is fundamentally inefficient. Ducts do help efficiency for a given diameter, but at the end of the day diameter/disk loading is king.
https://en.wikipedia.org/wiki/Disk_loading

>>980150
>And it is even smaller than OP's example or the arcaboard
Well... size really matters with these sort of things. Like you pointed out, it takes roughly 1000 equivalent horsepower just to keep one dude aloft with small jets, but the Hiller platform got by with just 80 and the sizable de Lackner Aerocyle made due with just 40. Can't cheat the physics:
https://en.wikipedia.org/wiki/Disk_loading#Power_required
>>980178
>Ok it's not fake but it's got 2 minute flight time.
10 minutes. Ten. By my reckoning, assuming the engines are crude non-afterburning turbojets, he should be burning ROUGHLY 5 pounds of fuel per minute (assuming ~1 lb/lb-hr TSFC).
>I just want to know how the fuck he managed to PID tune four turbojets into a quadcopter.
Well, judging from the statement:
>The problem is to create the algorithms, the right algorithms, to combine the intelligence in the board and in your brain
and the fact that it's predecessor (the water-jet flyboard) was fully-kinesthetic, I would venture to guess that their main issue was integrating a stabilized system that would supplement, rather than counteract, any intuitive kinesthetic control. Kinesthetic control works because the platform reacts naturally to the way you intuitively shift your weight (using the very same reflexes you use to stand). But if you throw a gyro-driven electronic stabilizer in there, it will resist this tendency unless you COMMAND it to respond to the way you lean. Realistically this means integrating pressure sensors into the footpads, similar to a Segway.

Additionally, their emphasis on the smaller auxiliary jets (and in particular, their steerable nozzles) suggests that maybe the role of the stabilizer is predominantly for yaw control (which doesn't fold so neatly into the kinesthetic control paradigm, hence the yaw vanes and tiller on the Hiller platform and probably something similar on the X-Jet as well), rather than for complete balance.