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Aircraft carrier catapults do that. When launching the aircraft, all the energy is expended from the ground. Looking forward to such gigantic machines on airpor

Aircraft carrier catapults do that. When launching the aircraft, all the energy is expended from the ground. Looking forward to such gigantic machines on airports, how much they would charge per flight, and problems like terrain slowly moving due to the gigantic forces at play.

smileysteve 7y ago
> Looking forward to such gigantic machines on airports, how much they would charge per flight It's actually an interesting supposition, because whether it's gasoline or electric, it should be cheaper and more reliable to run a ground operation than to pack fuel that is expelled before anything meaningful has happened.
hodgesrm 7y ago
Catapults accelerate aircraft to the point of generating enough lift for powered flight. They allow you to take off from a short runway like a carrier but don't get you to altitude. You can get a sense of how much power is being used to reach cruising altitude by listening to the engines on take-off. They don't fully throttle back until you reach a high enough altitude to permit level flight.
- pge 7y ago
  Good point - if you watch carrier launches, the planes actually fall a little as they go off the end of runway because they aren’t lifting yet. But presumably with a longer runway like you have at an airport, you could get to higher speed and truly liftoff. But having also launched from a carrier myself, I wouldnt want that g force everytime I fly commercially.
  - hodgesrm 7y ago
    I would love to launch from a carrier. Was in the Air Force but not flight crew. Saw a lot of great aircraft there...from the ground. :)
  - WalterBright 7y ago
    > the planes actually fall a little as they go off the end of runway If I was a carrier pilot, I doubt I'd ever get used to that!
- magduf 7y ago
  >Catapults accelerate aircraft to the point of generating enough lift for powered flight. Yes, but the reason they're used is because it's infeasible or too expensive to build an aircraft carrier long enough to have jets reliably take off from them without this extra boost. Even so, those catapults are fairly short: notice they're only a fraction of the length of the carrier. They're not used in regular airports because they're not absolutely necessary, the way they are on aircraft carriers. It's more expense, and planes can do without them. However, there's a cost to this: the planes need bigger engines and more fuel to take off reliably. And bigger engines are less efficient overall (as in cruising). So there would be a significant fuel savings if you could count on having catapults on the ground to help get the plane to takeoff speed: you could downsize the engines, and carry less fuel, saving a lot of money overall per flight (not to mention all the carbon pollution). Finally, the extra g-forces shouldn't be a big deal. There's high g-forces in a carrier launch because the catapults are very short. And until recently, they were steam powered. This needn't be the case with commercial aviation: they can use modern electromagnetic launchers, and they can make the catapults very long (as long as much of the runway), to have lower peak acceleration. Basically, the planes and passengers would not need to experience higher g-forces than they already do; they'd just be getting them from the catapult instead of solely from the engines.

smileysteve 7y ago

> Looking forward to such gigantic machines on airports, how much they would charge per flight It's actually an interesting supposition, because whether it's gasoline or electric, it should be cheaper and more reliable to run a ground operation than to pack fuel that is expelled before anything meaningful has happened.

hodgesrm 7y ago

Catapults accelerate aircraft to the point of generating enough lift for powered flight. They allow you to take off from a short runway like a carrier but don't get you to altitude. You can get a sense of how much power is being used to reach cruising altitude by listening to the engines on take-off. They don't fully throttle back until you reach a high enough altitude to permit level flight.

pge 7y ago
Good point - if you watch carrier launches, the planes actually fall a little as they go off the end of runway because they aren’t lifting yet. But presumably with a longer runway like you have at an airport, you could get to higher speed and truly liftoff. But having also launched from a carrier myself, I wouldnt want that g force everytime I fly commercially.
- hodgesrm 7y ago
  I would love to launch from a carrier. Was in the Air Force but not flight crew. Saw a lot of great aircraft there...from the ground. :)
- WalterBright 7y ago
  > the planes actually fall a little as they go off the end of runway If I was a carrier pilot, I doubt I'd ever get used to that!
magduf 7y ago
>Catapults accelerate aircraft to the point of generating enough lift for powered flight. Yes, but the reason they're used is because it's infeasible or too expensive to build an aircraft carrier long enough to have jets reliably take off from them without this extra boost. Even so, those catapults are fairly short: notice they're only a fraction of the length of the carrier. They're not used in regular airports because they're not absolutely necessary, the way they are on aircraft carriers. It's more expense, and planes can do without them. However, there's a cost to this: the planes need bigger engines and more fuel to take off reliably. And bigger engines are less efficient overall (as in cruising). So there would be a significant fuel savings if you could count on having catapults on the ground to help get the plane to takeoff speed: you could downsize the engines, and carry less fuel, saving a lot of money overall per flight (not to mention all the carbon pollution). Finally, the extra g-forces shouldn't be a big deal. There's high g-forces in a carrier launch because the catapults are very short. And until recently, they were steam powered. This needn't be the case with commercial aviation: they can use modern electromagnetic launchers, and they can make the catapults very long (as long as much of the runway), to have lower peak acceleration. Basically, the planes and passengers would not need to experience higher g-forces than they already do; they'd just be getting them from the catapult instead of solely from the engines.