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comment by kleinbl00
kleinbl00  ·  2156 days ago  ·  link  ·    ·  parent  ·  post: Human Jetpack Aviation: The Future is Here

JB=9: "10 minutes plus, depending on pilot weight," says Mayman. "For the technically minded, it also depends a little bit on temperature, altitude and that kind of thing, but that's by no means as significant as the total pilot weight."

Flyboard Air: "and a maximum endurance of 10 minutes. "

Williams X-Jet: "Endurance: 30–45 minutes"

One of these was cancelled by the Army in 1983. The other two are "the future is here."





lil  ·  2153 days ago  ·  link  ·  

This article in The Guardian explains why they haven't "taken off" commercially so far.

kleinbl00  ·  2153 days ago  ·  link  ·  

It's a start. But what the article says is that nobody can get the 90% peroxide the Bell rocket belt needs to run. Here's James Bond escaping SPECTRE in one of those, by the way:

Sean Connery is in the air in that clip for 20 seconds. He's got 21 seconds of gas. Cutting it a little close but hey, when does Bond not cut it close. Really, the craft in your article are orders of magnitude more advanced; they can do "ten minutes" of flight... in ground effect (which means they're hovercraft, not aircraft - it's a lot easier to push against the ground than against a column of air). The real problem is that non-winged flight is a horribly inefficient way to get around. The high water mark, in my opinion, is the Williams X-Jet, and it'll lift a 150lb infantryman (or a 140lb infantryman and a rifle) as high as you wanna go and take you as far as you can get at 60mph in 30 minutes. So that's 12 miles of range, lofting your kid sister and her iPad, screaming so loud you'll hear it all the way. Turn that thing on its side and the same motor will loft a 300lb thermonuclear warhead 1500 miles at just this side of Mach 1.

Lift, if you're willing to use aerodynamics, can be had without too much drama. Here's a Nazi kite designed to be towed behind U-Boats. Get the sub up to 15mph, turn into the wind and the thing will pick itself up and autogyro up to the end of its rope, no motor needed:

...but if you want to omit the wings and rotors and lifty bits that have formed the basis of flight since Icarus, you're literally dumping fuel faster than you can pour it out of a jerry can.

Dreamers look at birds and say "why can't we do that?" without realizing that if people were birds we'd weigh about 30 lbs. Dreamers look at drones and say "why can't we make that bigger" without realizing that most quadcopters don't go more than a few minutes on a charge. And I love a dream and I love a dreamer but every journalist who says "we're almost there people!" is doing a disservice to science, engineering and the people who practice them.

necroptosis  ·  2152 days ago  ·  link  ·  

Even your high water mark is vastly optimistic. 95% of infantrymen weigh well more then 150lbs, and that’s before the 30lbs absolute minimum of kit required in addition.

I consulted a while back with a Silicon Valley type trying to outfit drones to carry soldiers into the battlefield. It took ages for him to realize that you’d need to transport a minimum of 12 300lbs soldiers to a location, and at that point how is it not just a stupidly risky divided helicopter?

necroptosis  ·  2152 days ago  ·  link  ·  
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