h a l f b a k e r yClearly this is a metaphor for something.
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There have been concepts where man has personal helicopter and a
lot of them have been abandoned due to the fact that having big
spinning metal blade near human flesh can be a problem.
So my idea around that would be a harness backpack something like
an outdoor camping backpack capable of
carrying large load.
Attached with a quick release mechanism to the frame of the pack
would be a telescoping, foldable carbon polymer frame where the
copter blades are mounted. Ideally it would be great to fold it all up
into a backpack but the engineering challenge would be difficult.
I think the ability to raise and lower the blades would make it easier
to maneuver getting in and out of the suit. The quick release
function would be for the oh shit moment where you need to bail,
and the remaining backpack would contain a parachute pack.
Like other quadcopter designs you'd want as much computer
controlled help as possible. If you could pre program a route over
gps that would remove the incredibly difficult challenge of learning
how to fly a helicopter.
[link]
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How big of a quadcopter do you need to lift a 200 lb
man? |
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// you'd want as much computer controlled help as possible. // |
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Errr, no. You'd eant the simpleat possible systemn with the minimum to go wrong. |
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You mean like in the latest military aircraft? |
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I think the idea as posted envisages a single huge
quadcopter. |
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What would also be cool would be to have a squadron
of small, cheap quadcopters, each capable of lifting
maybe 10kg, all tethered to a man-carrying harness.
Software would have to keep them in formation, but
failure of one or two of them wouldn't be disastrous. |
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Anyone know how much a 10kg-lifting quadcopter
costs? |
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Geese are cheap; also reusable or deliciously disposable. |
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//Anyone know how much a 10kg-lifting quadcopter costs?// |
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It'd end up a hex or octo. |
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Probably like $10k+ to put together a simplified one with just controller receiver chassis and drives. And maybe 5 minutes flight time. People are doing things with coaxial drives that get crazy lift density nowadays. With multicopters you're playing diminishing returns with net lift power, battery capacity and tare weight for the required lift - with the loser normally being flight time. So to double flight time you need a larger battery, which means more lift required, which means larger chassis, and now a bigger battery, etc etc ad nauseum. Even $5k+ quads, carrying maybe 1.5kg of cargo (DLSR or other flash camera) have flight times of maybe 10-15 minutes on average. ...But they're optimised for features other than max lift. |
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Either way, they would end up bigger than you think. Soon enough there'll be enough of them and they'll be large enough that you actually have to take into account the fact that some are so far off to the side that they have to pull on an angle to contribute lift to you.. Which is both less efficient and a control nightmare. |
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...There are some interesting things happening with swarm control, however. |
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If there's one thing cheap nowadays it's computing power. Some controllers have 5-10, 32-bit microcontrollers onboard and weight under 100 grams. The limit here is electrical power and strength of materials. |
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//So to double flight time you need a larger battery,
which means more lift required, which means larger
chassis, and now a bigger battery, etc etc ad
nauseum.// |
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At some point it must make more sense to use a
model aircraft engine to drive an onboard generator,
no? |
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Interesting you say that, you're not the first person to suggest it. The other approach is to use direct drive to the props from a central powerplant, and use variable pitch to achieve control. |
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Either way you're up against energy and power density issues. Modern LiPo batteries can be amazingly power dense, fully discharging in 2 or 3 minutes if asked to. A brick battery the size of a 250g block of butter, weighing say 350g, can be 14 ish volts, hold 5000MaH and can discharge at 200+amps without blowing up. Likewise modern brushless DC motors driven by specialised ESC's can use that power and weigh tens of grams. |
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That's a lot to compete with. I hear about at least two nitro-hybrid or gas-hybrid designs being developed commercially, but none to market yet. Likely to be low-ish power comparatively (with good burst capacity) but with very long mission times. |
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//direct drive to the props from a central
powerplant// |
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But that involves a lot of extra engineering.
Generators can be extremely efficient at turning
rotational energy into electricity, and the control is
then much simpler. |
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// energy and power density issues// So, your 350g
example gives you about 250kJ of stored energy, and
a maximum power output of about 3kW. |
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Typical model aero engines have outputs on the order
of a kilowatt, and I'd guess that you'd get the engine,
generator and ?50ml? of fuel in 350g. The 50ml of
fuel is going to contain about 2MJ of energy (ie, 8x
that of the 350g battery). So, unless you really need
the peak 3kW output of the battery, an engine +
generator would seem the better option. |
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Plus, if you occasionally need more power, a
supercapacitor capable of delivering a few kW boost
for a second or two wouldn't be too heavy. |
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clearly, the application calls for a powered umbrella with counter-rotating louvred canopies. Pretty good power:weight with turbines. |
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/You'd eant the simpleat possible/
Is this scottish? |
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The term is "Scotch". They hate it when you call
them "Scottish". |
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