Re: Now all I need is my moonbase

In article <ItIhg.40391$4L1.8376@xxxxxxxxxxxxxxxxxxxxxxxxxx>,
Dean White <noone@xxxxxxxxxxx> wrote:
"Brion K. Lienhart" <brionl@xxxxxxxxxxxxx> wrote in message
news:PJ6dnUf38fmbqRrZnZ2dnUVZ_s-dnZ2d@xxxxxxxxxxxxxx
Peter Meilinger wrote:
Whatever happened to "real" jet packs, anyway?
[....] They seemed to fly well enough, though I'm sure
they only showed the very best of some carefully
controlled tests. Still, you'd think they'd have
gotten better by now. But nooooo!

They get really poor gas milage. As in flying for less than 30 seconds.

And noisy, as in extremely load, not something you can use to sneak up on
the other guy.

I think these are inherent problems, too, not just technological ones.
Since jetpacks/flying platforms are small, they need to work by moving
a small amount of air very fast. Helicopters can move a larger amount of
air --- the amount that passes through their rotor disc --- and so they
don't need to move it as fast. A fixed-wing aircraft moves an even larger
amount of air, presumably even less than a helicopter.

An aircraft stays up through conservation of momentum (m*v), but it pays
for it in conservation of energy (~ m*v*v). The lower velocity of air
you move, the less energy you need to expend for the same amount of
momentum.

Also, a thin fast-moving stream of air/exhaust is going to be more turbulent
and therefore more noisy than a large, slower-moving stream of air/exhaust/
wash/wake.

Also very hard to fly so all in all not useful enough for the military.

This I assume could be fixed with suffifiently advanced avionics.

--
Wim Lewis <wiml@xxxxxxxx>, Seattle, WA, USA. PGP keyID 27F772C1
.

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