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Comment by hyperpallium | Hacker News Reader

In USA future, backpack carries you!

I was a skeptic, but this looks unbelievably cool (even though they could have done a lot more cinematically).

However, jetpacks seem fundamentally limited to me because of the energy required. Perhaps a nuclear powered one would solve this? Or, the mythical massively higher density battery.

An alternative for personal flight is the powered parasail (aka parapont). There's a local guy who cruises around the bay shoreline at about 20-30feet, for a couple of hours. It's not capable of jetpack acrobatics, but more like seagulls soaring along a ridge.

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Nuclear would definitely solve the endurance problem. Since there's no weight margin for shielding, a few minutes of fuel would suffice for a lifetime supply.

Ha. I suppose a lifetime warranty is not out of the question as well?

As someone who kitesurfs and is quite aware of how air moves around -- you wouldn't catch me flying one of those things in anything over 10mph, especially around tall buildings. Gusts, rotors, turbulence. Ugh. Scary enough when you're 20 foot above water. Deadly when you're over land.

Not to mention the potential annoyance of people trying to buzz you with their drones.

The vertical take off landing makes for a much larger operating enevelope for a vehicle. The challenge is how to efficiently hover with out burning to much energy.

Larger rotors can out perform jets for efficinecy, ie rotors move a large volume of air at a slower velocity which is fundamentally more efficient then moving a small volume of air at a high velocity. You can also squeeze some more efficiency out of the system if you put a duct around the rotors, a duct can in itself produce ~40% of the total lift.

The Hiller flying platform which was built and test flown in the 1960's is a good model for something that could fly for 30-60 minutes with todays technology. You can search Youtube to find videos of its test flights...

https://www.youtube.com/watch?v=GgNlumaVPDw

its sorta like this https://www.youtube.com/watch?v=Bfa9HrieUyQ

A nuclear powered jetpack? Wait, sorry, what? Has there been some incredible development regarding either nuclear reactors or propulsion engines that I've missed out on?

If you don't mind heavy radiation, you could have a pu pile to rapidly heat air and blast it from a nozzle. This sort of thing was how project Pluto (bought to you by coors, of all people) worked. Nuclear powered cruise missile.

Not sure if you could make it quite small enough to stick on your back, and again, heavy radiation.

Pluto is an interesting one. So destructive that the plan was to have it just fly back and forth across the Soviet Union after it ran out of bombs, killing and destroying with the radiation from its unshielded reactor and the shock wave from flying past at low altitude at Mach three.

One of the (many) reasons it was killed was the question of how you would test such a beast. If it went haywire, you'd have a weapon on the loose that killed just by flying around, and with an enormous endurance. Oh, and which was basically impossible to shoot down.

There seems to be precious little military utility to such a mode of operation. It sounds like any possible use of it would be a war crime.

It was a delivery system for strategic-scale nuclear warheads. Those are war crimes pretty much by definition.

Well, it was intended for use in a total nuclear war.

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