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Airplane lifting hot air balloon

Eliminates runways
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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.

Voice, Jul 18 2012

How much fuel does it take to takeoff if you're a jumbo jet? http://answers.yaho...080415033904AASnd5T
[Voice, Jul 18 2012]

wind speeds at altitude http://www.classzon...02/es1702page09.cfm
[bs0u0155, Jul 20 2012]

Prior art from 2004 Lighter Than Air Landing Gear
elf promotion [pashute, Jul 04 2015]

[link]






       //It would save a good deal of fuel//   

       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.   

       //and render airports very quiet// And landing aircraft?
MechE, Jul 18 2012
  

       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.
Voice, Jul 18 2012
  

       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.
Vernon, Jul 18 2012
  

       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.
MaxwellBuchanan, Jul 18 2012
  

       One question: what happens to the passengers and their lunch during the 10 seconds of freefall?
MaxwellBuchanan, Jul 18 2012
  

       It's like a baby space elevator.   

       The fall would be fun, for me at least!
DIYMatt, Jul 18 2012
  

       What happens to the pilot of the balloon / dirigible / blimp when the plane is released?
RayfordSteele, Jul 18 2012
  

       "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..."
elhigh, Jul 20 2012
  

       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.   

       Dubious, but still launching my bun. I like the idea.
Alterother, Jul 20 2012
  

       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.
DIYMatt, Jul 20 2012
  

       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.
bs0u0155, Jul 20 2012
  

       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.   

       Then we must consider when to run up the engines, before release, or just after?
Alterother, Jul 20 2012
  

       //repetitive stunt maneuver is not really what big airliners are built for.//   

       If the launch altitude were sufficient, you wouldn't need any radical maneuvers - certainly not beyond the plane's limits. Bigger problems would be:   

       (a) do you start with the plane horizontal, nose- down, or vertical? The latter makes most sense, but would interfere with the drinks service.   

       (ii) where you do attach the hook? You'd need either a modified plane or a schnazzy cradle.
MaxwellBuchanan, Jul 20 2012
  

       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!
Alterother, Jul 20 2012
  

       //big jets aren't built to withstand the strain of pulling out of vertical dives on a regular basis,//   

       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.
MaxwellBuchanan, Jul 20 2012
  

       Stress is what I mean. My structural-fab lingo is a little rusty, I hope you'll forgive me.   

       I guess what I'm getting at is that this method might necessitate redesigning airliners, or at least benefit from it.   

       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?
Alterother, Jul 20 2012
  

       //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?//
  

       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.
  

       (+) I really like this one.   
      
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