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  #31  
Old 03-03-2006, 01:06 AM
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drakkie drakkie is offline
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It is possible but utterly pointless. The coveyor belt starts running and the aircraft starts engines. The aircraft has then first provide enough force to counter that of the belt passed through by the wheels/bearings.Assuming these have a low friction level,the counter-force is also low. ABOVE that it also has to provide enough force for normal takeoff. So you get normal force with an extra ie. 120% of the normal forces applied. Seems that lots of money is wasted on that extra 20% of power through fuel and bigger engines.

If the conveyor belt is in the same direction as the aircraft is taking off,it will be:
1) a huge challenge to get a belt big enough and able to support a full-size aircraft.
2) a waste of money, because one of those mile-long conveyor belts run over various suport wheels and stuff. These have friction,the belt on the driveshaft has some slip etcetera. I think the gains using this system(little to no fuel usage by aircraft on takeoff) would eventually not be enough. In my logical thoughts-stream it seems that the power used to overcome all these supports and wheels plus the slip is much more as an aircraft with about 8special bearings(assumed 8 wheels) with little friction.
3) it would be very dangerous,cos an pilot has to time the powering of the engines exactly,cos when he lifts off,he would have to use them again. Im sure you can train on that,but an normal take-off is easier for the pilot,thus making less mistakes.
4) The funding. a airport or government would have to pay for it,while they dont gain a thing for it, only the airlines. If they would have to pay for something that they don't really need and is expensive,they will complain and avoid these airports.

It will never happen. It can be realized,but would have no real point.
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  #32  
Old 03-03-2006, 02:59 PM
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Looks like something for the Mythbusters to figure out.
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  #33  
Old 03-03-2006, 03:04 PM
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Quote:
Originally Posted by uh_huh
Looks like something for the Mythbusters to figure out.
It's not necessarily much to figure out.. in ideal conditions, being: friction not coming into play, unlimited loads of speed on the bearings/rubber, etc. Simply, the thrust from the plane would make it move forward in a normal matter, but the wheels would be spinning 2x as fast to counter the speed of the runway.

It's kind of like rollerblading on a 'conveyor belt', same kind of concept. The thrust would be gliding across with your legs, but the wheels would be spinning at 2x the speed.
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  #34  
Old 03-03-2006, 03:27 PM
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its gonna be like a huge treadmill
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  #35  
Old 03-03-2006, 04:47 PM
"Clevor" Angel "Clevor" Angel is offline
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My physics teacher gave us this problem 1st quarter. It's one of those questions where if you just think about it without actually "thinking" about it, you'll get it. It will take off.
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  #36  
Old 03-03-2006, 05:49 PM
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Quote:
Originally Posted by kingofthering
its gonna be like a huge treadmill
Not really, in the sense that treadmills keep the subject in place by counter-acting the velocity of the belt with their feet, keeping the person 'in place'.
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  #37  
Old 03-03-2006, 06:03 PM
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yes, it will
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  #38  
Old 03-03-2006, 06:07 PM
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i was going to say no but then if you think about it it's a jet so the jets will propel it of the runway right?
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  #39  
Old 03-03-2006, 06:08 PM
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Quote:
Originally Posted by The_Canuck
i was going to say no but then if you think about it it's a jet so the jets will propel it of the runway right?
Correct, read the posts above.
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  #40  
Old 03-04-2006, 09:17 AM
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It will only if the plane is attached to the runway before takeoff. Otherwise, it hits the tree's in front of the runway and everyone dies. You look out the airport and see ants scrambling away from a burning toy plane.
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  #41  
Old 03-04-2006, 10:48 AM
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Quote:
Originally Posted by Rockefella
Correct, read the posts above.
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  #42  
Old 03-04-2006, 11:21 AM
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The wheels arent driven and we can assume that there is no friction in them (though not the case). Therefore the plane will stay in one place untill the pointwhere the pilot inc the throttle when the plane will accel at the normal rate and take off in the normal distance, although with warmer wheels
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  #43  
Old 03-06-2006, 07:22 PM
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of course it will take, that took me all of 5 seconds to figure out
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  #44  
Old 03-06-2006, 09:36 PM
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Ok my argument may be a little hard to understand, but just try to picture it.

I say no because the jet engines simply can't produce enough wind for the plane to lift, if the belt is moving in the opposite direction of the plane at the same rate the engines are pulling the air. So in this case, even if the engines are powerful enough to produce winds that is enough to lift the plane, where the hell does the plane itself get airspeed? I mean, it's like a jet going straight up for a few meters just when somebody realizes that it's taking off at zero airspeed, then the weight of the plane brings it all back down to the runway. The result, in my opinion, would be a plane bouncing up and down like a basketball in slow motion. Pretty funny if you ask me.

EDIT: For example, look at how fighter jets take off from aircraft carriers. Even when they're locked in place at the beginning of the take off process for the engines to reach high powers, they still need that tiny runway to launch themselves, and if the carrier is at sea level, the planes would just launch into the ocean like boats. I think it would be more useful to experiment with a commercial aircraft based on the F-35, since its thruster points at the ground at takeoffs and slowly tilts so it can actually gain some airspeed and lifts at the same time.

EDIT #2: If the belt moves slower than the rate the engines are pulling the air, then the aircraft will be able to gain some airspeed.
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Last edited by NuclearCrap; 03-06-2006 at 09:47 PM.
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  #45  
Old 03-06-2006, 11:34 PM
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uhh.. just about a minute ago i thought "I dont care about the scientific answers, the plane will not fly!"

But suddenly, i think about how Harrier jets take off.... it may just be possible...
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