h a l f b a k e r yI never imagined it would be edible.
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The idea of a "jet" (or rather rocket) - pack has been around for years. The BIG problem is endurance, and our suggestion is to follow the advances in model RC true jet aircraft design, and use currently available "model 'plane" turbines as the power source.
Current technology big issues are not-so
great (but improving) power - to fuel consumption ratios, and noise. Suggestion would be to combine current Electric Ducted Fan turbine advances (Schubeler - carbon fibre multiblade turbine), with current straight - jet technology, to produce a "mini -RB211" high bypass engine, which would have the advantage of higher efficiency (= lower fuel demand), and lower noise levels - probably important if you live in a high-density area and work "unsocial hours" . . . .
The design is a standard twin - engine jetpack, and since the new models run on kerosene / 2-stroke oil mix, there would be no problems in fuelling up (visions of the local Service Station offering Unleaded, Premium Unleaded, Jet-A!). There are a LOT of suppliers in the Model Jet market, and I notice that JetCentral now market a turboprop (so far only 19lb static thrust). This will be the area to watch, and the competition out there is getting fierce (Wren, I-Jets, JetCat, KingTech, EvoJet, PST (Thailand), Hawk, PureJet and AMT): Fierce competition improves product specifications, so we would suggest that this idea is not just half-baked, rather it's well on the way to exiting the oven and appearing on a delicatessen shelf near you!
Jetpacks
http://en.wikipedia.org/wiki/Jet_pack
All the pretty toys ... [8th of 7, Dec 22 2009]
Homemade Leaf Blower Jetpack
Homemade_20Leaf_20Blower_20Jetpack
Been there, seen that, done the math ... [8th of 7, Dec 22 2009]
HIgh bypass "jet" pack
http://www.martinjetpack.com/
[MisterQED, Dec 23 2009]
Guanidine nitrate
http://en.wikipedia...i/Guanidine_nitrate
Lovely stuff [8th of 7, Dec 25 2009]
Model Jet Engine Pack
http://www.wired.co...an-richard-browning
[bs0u0155, Nov 02 2017]
[link]
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<links to the jet-guy and to the French 'Cri-Cri' which is basically a faired seat, itty bitty wings and 2 jet engines> |
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//so we would suggest that this idea is not just half-baked, rather it's well on the way to exiting the oven and appearing on a delicatessen shelf near you!// |
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[marked-for-deletion] on soo many levels |
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Thanks FT - but the proposal is NOT a "mini-plane": The device you mention has a power to weight ratio of <1, whilst my proposal would need a PtW ratio of >>1. The big issue is still fuel demand (for a net 80kg static thrust you'll be burning kerosene at a rate of 1.2kg/minute), and since the "arrangement" will be somewhat less than aerodynamic, even moving from the hover to translational flight would probably not improve burn rates significantly. So, 5kg (or about 1 imp. Gallon) would give four minutes flying time, which might be really good for an A320 on one engine, but which won't cut the mustard for your average commuter! [Further development required} |
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By bizarre coincidence, I was recently thinking about ways
to make a "personal jet pack" (a la James Bond), and
whether this was becoming feasible as a result of recent
developments. I was not looking for useful flight times,
just periods of up to a few minutes (as compared to
current "jet pack" durations of under a minute). |
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Ducted fans certainly seem to be the way to go, for many
reasons (including compactness, safety and noise). As for
power source, electrics begin to look very attractive *if*
you only want very short flights. As you note, electric
motors deliver higher power/weight than anything else,
and it's only the batteries needed for sustained running
that kill them. So, short hops with battery-driven electric
motors seem feasible. |
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[MB], a trailing power lead? |
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Indeed so. But seriously, you can get model electric
ducted fan units which weigh under half a pound
(integrated motor/fan unit; excluding batteries) and give
up to 8lb static thrust, and have a diameter of about
10cm. |
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Now assume that a 1lb battery pack will run the fan for 30
seconds. You therefore have a 1.5lb unit, leaving you an
excess static thrust of 6.5lb. |
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30 such units (total weight 45lb including batteries, plus
some more poundage for a mounting frame) will give you
about 200lb of net lift and, if packed side-by-side, would
fit
into a 60cm square. Thus, a 30-second-duration
lightweight human-lifting pack seems quite feasible. |
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With more batteries, of course, you get longer flight, but
you also need more units because the residual thrust
(after deducting battery weight) is less. |
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I was being serious; your 30 seconds flight time on batteries is not going to take you further than the range of an extension lead. The "fan-belt" plus trailing cable would work very nicely for streetlamp repair crews, gutter cleaners, and placing the fairy on top of the christmas tree. |
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Very true. But for maintenance work, there's already a very
good array of compact vehicles with lifting platforms. |
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I'm not after anything practical - I just want to be like James
Bond for a moment. Somehow, the extension lead would
spoil the effect. Plus an evil mountebank could unplug it at
the wrong time. |
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OK so how about a microwave projector on the ground, while your suit includes a receiveng dish? |
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You could use the 30 second battery life for a safe descent when Dr. Evil pulls the plug. |
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Anyway, for the James Bond version it has to have flames coming out the bottom |
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So, I'm going to be hanging off this belt thingy, 50ft off the
ground, and someone is going to fire a microwave beam at
me. I'm looking forward to that. |
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And, for the record, the James Bond version had no flames.
It had clouds of condensation (CO2, I think) from the
compressed gas cylinders that powered it. |
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Just goes to show James Bond does not always get it right. |
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// I'm looking forward to that // |
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So are we. You have no idea how much ... |
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// James Bond version had no flames // |
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No, plain old water vapour. The Bell jetpack uses Hydrogen Peroxide <link> as its fuel. |
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If it's a man-lifting device, then what's needed is a real gas-turbine engine, not a model. We've done this one before. <link> |
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[FT] is right, this is baked and for sale, he just got the wrong link see mine. |
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Sorry, [MB], EDF (ducted fans) are really NOT efficient: for an equivalent 10cm diameter EDF unit (producing say 4kg ststic thrust), you can buy a model jet engine from, eg AMT which will produce 9kg static thrust. As a typical example, four AMT Olympus HPES engines right now (off the shelf) will provide 94 kg static thrust (and burn a healthy 2.6kg kerosene every minute), so the technology (including the control systems) exists right now, as "all off the shelf" modules. |
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The major impediment to literally "doing it oneself" would be the cost (about $ 10k for the engines and management system), and the fuel penalty - even assuming we were able to travel at the (unlikely) speed of 120 kph, you would still be burning roughly a gallon every 4 km, so for a "reasonable" duration trip the fuel bill would be astronomical. |
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As Model Jet RC starts to enter the mainstream of RC Aviation, it is reasonable (though not guaranteed) that power to consumption ratios will improve, especially if Wren (UK)'s proposed high-bypass turbine project comes to fruition. |
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The other issue is that of reliability - most engines require "Back to Base" servicing every 50 hours of runtime, and servicing is not exactly cheap . . . |
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The existing "Jet Packs" a la James Bond all rely on catalytic decompposition of hydrogen peroxide, so they are not "true" gas turbines, rather thay are liquid fuelled rockets. I seem to remember that no matter how large they become, the run time is no better than about 90 sec, since as the "fuel" payload is increased, so the thrust needed (= peroxide flow rate) increases also. |
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The former "Jetex" Company used to produce a peroxide - based JATO kit for the larger RC models but that's disappeared into the mists of time. |
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Final note: Model Turbines are right now providing the most thrust per $ spent (initial capital investment): second is the traditional piston engine (2 stroke > four stroke), with Electric bringing up the rear (Electric "traditional" Prop being more efficient than (current) ducted fan designs). The only real advantage of electric is the silent / quiet flight nature, and this is not the case with EDF! |
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//DF (ducted fans) are really NOT efficient://
I know. On the other hand, they are fairly cheap, very low-
maintenance compared to jets, and also fairly quiet
(comparatively). |
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//The major impediment to literally "doing it oneself"
would be the cost (about $ 10k..// Oh, come on, $10K is
hardly an impediment. If a rocket-belt isn't worth more
than a decent meal for your friends, then I don't know
what is. EDF works out about the same, by the way,
thrust-for-thrust. |
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I agree completely that jets are the way to go in terms of
thrust/weight and flight duration. But if you wanted to
knock up a personal flying machine for fun, then electric
EDFs are probably the way to go in terms of ease of use. |
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// "Jetex" Company used to produce a peroxide - based JATO kit for the larger RC models // |
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Jetex fuel was based on Guanidine nitrate, not peroxides. |
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