h a l f b a k e r yBaker Street Irregulars
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JATO (Jet Assisted Take Off) is fun. Just look at all the
lovely pictures and try and imagine it with a whole lot of
noise and smell to boot. <link>.
Normally, this is provided by small, disposable rocket
engines which are jettisoned when they've done a short
amount of work. The final goal
being to get the aircraft
off the runway in a shorter distance and time or at a
higher takeoff weight than would otherwise be
permitted.
Now, can we do this another way? Yes. Lets use some
nice
big Electric Ducted Fans (EDF), with a nice rechargeable
battery pack. Now, batteries have a not so great energy
density but that's a problem that is being slowly solved.
We
only need a few minutes of power, it's workable now and
will improve in the future.
So, the traditional route is to attach JATOs, use them for
take off and then jettison them, forming a crater in a
nearby field/house. "Can we do better?" is the question.
"Yes probably" is the answer. How about we make the
jato
a small autonomous craft? Now we can use it for take
off,
jettison it whereby it happily quad-copters it's way on a
predetermined plane-avoiding route back to the charging
station.
There, aviation, improved a bit.
JATO
http://en.wikipedia.org/wiki/JATO
[bs0u0155, Dec 05 2014]
EDF
http://www.edfenergy.com/
[not_morrison_rm, Dec 06 2014]
Robert Goddard
http://en.wikipedia...iquid-fueled_flight
Crude, yet effective ... [8th of 7, Dec 06 2014]
[link]
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Or you could tether the vehicle to the ground, using a cable
to supply electricity. And it doesn't actually have to take off
as long as it provides the speed. |
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And then congratulations, you've invented the electric
catapult, in common use on air craft carriers. |
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The big plus points of JATO bottles are: |
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They require no support infrastructure. |
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They require no maintenance. |
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They are extremely simple devices. |
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They are extremely reliable. |
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They provide a high specific impulse in a relatively small, lightweight
form factor. |
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Electrical systems don't meet any of these requirements. |
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I was not able to find any video of these JATO
devices used as personal jet packs. |
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There's a good reason for that. |
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During WWII, the Germans evaluated the idea of a single-use rocket
pack to allow troops to "hop" over mined areas, barbed wire, or
difficult terrain i.e. marshland. |
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//the Germans evaluated the idea of a single-use rocket
pack to allow troops to "hop" over mined areas,// |
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And concluded that the mines were a faster, cheaper way of
launching their troops into the air and have them come
down in an uncontrolled manner. |
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Can we go back to Eclectic Duck Farms please? |
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Jet assisted hopping is such an attractive idea.
There must be insurmountable issues with keeping
the jet pointing down. Maybe spinning the fuel
reservoir for gyroscopic stabilization... |
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Good idea and a two-for-one thingy. Suspect the entire Iraq/Afghanistan conflict just in order that coalition forces get an edge at the next paralympics. |
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// insurmountable issues with keeping the jet pointing down. // |
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Not so; vide Robert Goddard's first liquid-fuelled rocket <link>, which
placed the venturi above the fuel tank, thus guaranteeing the centre of
mass is below the point of suspension. |
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Which would be great - except for the fact it doesn't work. |
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//venturi above the fuel tank, thus guaranteeing the
centre of mass is below the point of suspension// |
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The supposed advantage of that geometry is a
common misconception. Many early rockets had a
similar arrangement (nozzles at the top, so that the
rocket was "pulled up" from above rather than pushed
from below). However, it makes no difference to
stability, which is why later rockets always have the
nozzles at the bottom, where they can point straight
down. |
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//Many early rockets had a similar arrangement (nozzles at the top, |
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Surely that was because the test range was Woomera.. |
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