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Modern aircraft are inevitably designed to naturally fall
from 0 air speed into a
front-down configuration that allows them to pick up
speed.
Exploiting this design feature it should be possible to
simply
lift fully loaded aircraft to a few tens of thousands of
feet
with a tethered hot
air balloon and release them. It
would
save a good deal of fuel and render airports very quiet.
EDIT: minor clarification
EDIT: now I'm thinking of just keeping a hot air balloon
aloft. Attached: a great pulley with a cable winding
'round and 'round powered at the ground.
Prior art from 2004
Lighter Than Air Landing Gear
elf promotion [pashute, Jul 04 2015]
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//It would save a good deal of fuel// |
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How are you keeping your hor air balloon buoyant, and how are you lowering it un-loaded. At a minimum, you are still expending a significant amount of energy, if not fuel. |
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//and render airports very quiet//
And landing aircraft? |
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landing aircraft must use the traditional method, but
that's still only half the noise... unless the pilot has
sufficient testicular mass to stall the airplane into
an attachable net. |
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I'm not sure about a hot-air balloon reaching tens of thousands of feet. A hydrogen balloon would be much better. Because you can compress the hydrogen into tanks after you have lifted/released the aircraft, so the balloon can descend to loft another aircraft. |
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Not sure about fuel savings (except on very short
flights, where take-off is a significant proportion of
the total fuellage). But it would let planes carry
more weight, just as in-air fuelling does. |
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One question: what happens to the passengers and
their lunch during the 10 seconds of freefall? |
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It's like a baby space elevator. |
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The fall would be fun, for me at least! |
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What happens to the pilot of the balloon / dirigible / blimp when the plane is released? |
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"Ladies and gentlemen, this is your captain speaking. We're about to release from the takeoff balloon and begin our flight. We'll be flying straight down at a rapidly increasing pace until we have enough airflow through the engines to fire them off, but don't let that worry you, it almost always works..." |
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Is a 747 even capable of a diving re-start from stall? I know
somebody managed to roll one a few years ago, but this
kind of repetitive stunt maneuver is not really what big
airliners are built for. |
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Dubious, but still launching my bun. I like the idea. |
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You don't need to do a ram air start, the APU will start the
engines. I would still want them running before cable
release. |
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So wind speeds can be pretty significant at aircraft
altitudes <link>. While not enough to sustain level
flight even with the flaps etc. deployed, the 50-70
knots would mean you'd only have to gain 20-50 extra
knots, which will happen pretty quickly once the
aircraft is released... especially if you've got the
engines nicely spooled up beforehand. |
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If the engines are spooled up and idling, even the minimal
thrust they're generating will noticably effect the flight
dynamics of the lift balloon. Keeping it located with that
lateral thrust pushing it off-course will burn more fuel. |
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Then we must consider when to run up the engines, before
release, or just after? |
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//repetitive stunt maneuver is not really what big
airliners are built for.// |
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If the launch altitude were sufficient, you
wouldn't need any radical maneuvers - certainly
not beyond the plane's limits. Bigger problems
would be: |
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(a) do you start with the plane horizontal, nose-
down, or vertical? The latter makes most sense,
but would interfere with the drinks service. |
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(ii) where you do attach the hook? You'd need
either a modified plane or a schnazzy cradle. |
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That's exactly the kind of thing I mean though; big jets
aren't built to withstand the strain of pulling out of vertical
dives on a regular basis, nor are they designed to by
suspended by the tail or dorsal fuselage. They are designed
to be suspended by their wings while in flight and
supported by their undercarriage when on the ground. The
kind of treatment that's being proposed here would have a
modern airliner coming apart at the joins within weeks! |
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//big jets aren't built to withstand the strain of
pulling out of vertical dives on a regular basis,// |
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There's no special strain (or stress, which is what you
mean) associated with pulling out of a vertical dive,
as long as it doesn't have to be done quickly. |
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Stress is what I mean. My structural-fab lingo is a little
rusty, I hope you'll forgive me. |
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I guess what I'm getting at is that this method might
necessitate redesigning airliners, or at least benefit from
it. |
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What if the jets rode _on top_ of the LTA lifter, and took
off as from an aircraft carrier, assisted by a catapult and
running down a slope? |
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//How are you keeping your hor air balloon buoyant, and how are you lowering it un-loaded.//
//I'm not sure about a hot-air balloon reaching tens of thousands of feet.//
//What happens to the pilot of the balloon / dirigible / blimp when the plane is released?// |
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I would go with solar hot air if possible.
The balloons have reached more than 100,000 ft.
The pilot of the aircraft could be the pilot of the balloon. The volume of heated air in the balloon could be rapidly vented and the balloon itself reeled into the aircraft's cargo hold during free-fall. |
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(+) I really like this one. |
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