Hacker Newsnew | past | comments | ask | show | jobs | submitlogin

> This seems exceedingly worthy.

Well, perhaps, though running several jet turbines... aside from the amazingly loud noise, that seems a lot of maintenance and fuel? EZ-fly's 5 engines, 280 lb payload, and 12 minutes duration, suggests something vaguely like JetCat P400-PRO 89 lb thrust engines. So say $3/min fuel. Running near max, so maybe low/mid-order 100hrs for minor/major teardowns? A $10k engine. So about the same cost/min for maintenance? Swap out an engine each shift. So several hundred dollars per hour operating cost? So like a light helicopter? But louder.

A similar but jetpack form: https://www.youtube.com/watch?v=Kh1x6q21-HU

Thus all the attention on electric and hybrid, and winged VTOL.



I confess, I'm waiting for an Xjet/WASP III. Can't help it. I do agree that there is room for improvement, notably with efficiency. Do you have any estimate of the decibel level of the WASP?


:)

Any estimate? Well... WASP was apparently a turbofan, and thus likely quieter than these small turbines - less high-frequency noise from shear. Quick googling turns up [1], which has a CJR900 small airliner as 78 SEL dBA @ 400 ft @ low 1k lb taxi thrust. So perhaps take that as a low bound. And [2] suggests an upper bound of 120 db at 9 ft for one of those small turbines. So...?

I was going to say "No idea, sorry", but when encouraging estimation and rough quantitative reasoning, I argue that one should never say "no idea", because its almost always untrue - one can almost always get some bounds. And surprisingly often, they are satisficingly narrow. Though perhaps not these.

One notable thought from [2] was the high-frequency noise attenuates rapidly with distance.

[1] https://www.nap.edu/read/22606/chapter/6#19 [2] https://www.rcuniverse.com/forum/rc-jets-120/9317226-need-de...




Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: