Tethered, Water-Powered Jetpack Provides Two Hours of Flight Time

arshadk writes "Unlike 'ordinary' jetpacks, the JetLev is actually two vehicles, tethered by a hose the thickness of your thigh. On the water is a small speedboat-like unit which contains a 250 horsepower motor and a pump. This is connected to the pack — into which you strap your frail body — by a 10-meter hose. The water is pumped from the sea or lake below up to the nozzles on the jetpack, providing a 1,900-Newton thrust, enough to lift a human weighing up to 150 kilos."

Re:could it be scaled up

[CosmeticLobotamy]

You're then pulling along a 20km hose behind your rocket, and that hose has to be strong enough to support its own weight. You're going to add more weight than you're subtracting.

Unless you built a 20km tall tower that the hose hangs down from and as the rocket ascends you retract the hose so the rocket doesn't have to carry the slack. But then you have to build a 20km tall tower that can hold an enormous amount of hose (still sturdy enough to be 20km long) and the weight of the fuel item you're moving, and since that weight is going to be on one side of the tower you'd have to counterbalance it on the other side. Tricky.

2 hours?

[binarstu]

Why is 2 hours of flight time an apparent selling point for this thing? Why would anyone need or want to hover a few feet above the surface of a lake for 2 hours nonstop? Granted, you can "fly" much longer than in more traditional jetpacks, but it seems a bit like bragging about a car that can go 600 miles on a single tank but is permanently tethered to the gas station.

That said, it sure looks fun to try.

Re:could it be scaled up

[vadim_t]

Ah, Slashdot!: Where no creative idea is too good to be voiced without being shot down by a dozen technical objections before it can even take flight.

Space flight was achieved by addressing technical objections, not by ignoring them and pretending "creativity" is all there is to it.

So for instance, if your creative idea requires a 20km high tower made of solid unobtainium, then you have a problem, until you actually succeed at coming up with a material with the required properties.

The OP's idea is speculative, but could be a good way of saving fuel in the first few seconds of rocket flight. But if the general community of engineers has the kind of attitude on display around here, I doubt anyone will even bother to do the calculations.

You're proposing the idea, it's your job to prove it can be done. So go provide some calculations.