Randazzo

So, you have a plane on a conveyor belt...

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11 minutes ago, Mad Rocket Scientist said:

It's not super likely, but starting the runway in the other direction (or even better, on the properly curved area the KSC is on) would eliminate all possible errors.

This was part of why I did this on Eve in Alien Space Programs as well. Rotation speed is much slower (22h 22m) and gravity is higher (1.7g). The platform didn't have brakes turned on, and there was a 0.0 to 0.1 m/s idle speed measured on the nav ball. 

The original craft file is on Kerbal X if you want to try reversing the mechanism. I can make the Ubiozur version available as well but I wouldn't be able to put it on Kerbal X. In any case, I'm tired of this now. Anyone else can take the original craft and, like actual scientists, apply additional scientific rigor.

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1 minute ago, Gordon Fecyk said:

This was part of why I did this on Eve in Alien Space Programs as well. Rotation speed is much slower (22h 22m) and gravity is higher (1.7g). The platform didn't have brakes turned on, and there was a 0.0 to 0.1 m/s idle speed measured on the nav ball. 

The original craft file is on Kerbal X if you want to try reversing the mechanism. I can make the Ubiozur version available as well but I wouldn't be able to put it on Kerbal X. In any case, I'm tired of this now. Anyone else can take the original craft and, like actual scientists, apply additional scientific rigor.

IIRC, the rotation on the runways was not from the planet's rotation, but from the runway being flat, which makes the center of it closer to the planet. But if the speed was less than 1 m/s it's not that important.

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4 hours ago, Gordon Fecyk said:

here's a shout to @Shpaget for being the other brave fool.

Thank you for your kind words, however, I can't take the credit for the video, as I'm not the one who made the contraption.

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On 6/1/2018 at 10:13 PM, Gordon Fecyk said:

This was part of why I did this on Eve in Alien Space Programs as well. Rotation speed is much slower (22h 22m) and gravity is higher (1.7g). The platform didn't have brakes turned on, and there was a 0.0 to 0.1 m/s idle speed measured on the nav ball. 

The original craft file is on Kerbal X if you want to try reversing the mechanism. I can make the Ubiozur version available as well but I wouldn't be able to put it on Kerbal X. In any case, I'm tired of this now. Anyone else can take the original craft and, like actual scientists, apply additional scientific rigor.

The problem is inherent to the physics engine though.  It is not an "ideal" treadmill.  

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31 minutes ago, DAL59 said:

The problem is inherent to the physics engine though.  It is not an "ideal" treadmill.  

Nor do I think KSP adds the rotation energy of the wheels into the calculation just the drag who is fixed as long as you are rolling. 
You can look at this in an energy calculation. 
Put an fighter jet on an treadmill, full trust with afterburner, you are now doing say 0.7g on an 30 ton plane. Friction is an constant and its low compared to the jet engines so the only way to stop the plane is to use the energy elsewhere. I can not see any other sinks for the energy than the rotation energy of the wheels. 
So yes two jet engines is now used only to spin up three wheels with an total weight of say 60 Kg, just accelerating them would give 350g force, however the heaviest part of the wheels are metal rim and brakes. closer to the center of rotation while the outer rubber part is very light so it would probably over 1000 g acceleration. 

Obliviously you can not accelerate an  real world treadmill track with 350g, it would snap, you could not even spin up an superconducting electrical motor so fast. 
So assume an ideal treadmill, this would also assume ideal wheels who would not disintegrate because of centrifugal forces nor overheat. 
Same is true for the treadmill. But as the wheels has mass who must be accelerated so does the treadmill, the treadmill also has to accelerate an far higher mass. 

I can demand that the treadmill is either of the conveyor belt type or is an rotating plate so large the plane can takeoff from it with no problems. 
If so I win because of relativity :) 

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And here I am, thinking such a universal answer would stop the flood...

Doesn't really work isn't it.

standards.png

Edited by YNM

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@DAL59 @magnemoe I made sure the TWR and acceleration of both craft (platform and aircraft) were as close to equal as possible, which you can observe using the Kerbal Engineer display, to eliminate the 'accelerating treadmill' and 'ideal conveyor belt.' I used rockets instead of jets to eliminate jet spool-up delay. I tested the friction of the landing gear, and while it's non-zero it's still pretty low. I only needed 4g acceleration, not 350g.

How many iterations do I need to bust this myth? How may times will the goal posts get moved?

 

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53 minutes ago, Gordon Fecyk said:

@DAL59 @magnemoe I made sure the TWR and acceleration of both craft (platform and aircraft) were as close to equal as possible, which you can observe using the Kerbal Engineer display, to eliminate the 'accelerating treadmill' and 'ideal conveyor belt.' I used rockets instead of jets to eliminate jet spool-up delay. I tested the friction of the landing gear, and while it's non-zero it's still pretty low. I only needed 4g acceleration, not 350g.

How many iterations do I need to bust this myth? How may times will the goal posts get moved?

 

They won't accept it because they want the treadmill to accelerate to hundreds of gees.

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40 minutes ago, Gordon Fecyk said:

@DAL59 @magnemoe I made sure the TWR and acceleration of both craft (platform and aircraft) were as close to equal as possible, which you can observe using the Kerbal Engineer display, to eliminate the 'accelerating treadmill' and 'ideal conveyor belt.' I used rockets instead of jets to eliminate jet spool-up delay. I tested the friction of the landing gear, and while it's non-zero it's still pretty low. I only needed 4g acceleration, not 350g.

How many iterations do I need to bust this myth? How may times will the goal posts get moved?

You misunderstood me, yes in KSP if plane and moving runway has equal acceleration the plane takes off pretty much as on an runway, same in the real world. 

This is something all agree on I think.
The problem is the ideal treadmill idea or an spherical cow who ignore air resistance, friction and gravity, its also has no break point so it will not break down at hyper-sonic speeds. 

 Then the fighter jet run at full power but stand still because of the treadmill the energy from the jet engines has to go somewhere. 
As I see it the only place the energy can go is to spin up the wheels, the plane does not have to do anything but the treadmill has to accelerate so fast the rotation energy of the small wheels eats the power from the jet engines this cause the idiotic acceleration requirements. 
No it would not work in practice, the acceleration it pretty much non solvable in an realistic faction, the second is the control requirement, you need to match the exact speed of the wheels at high acceleration and adjust your own power output. 

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3 hours ago, Randazzo said:

9Q0SSUl.gif

Impressive: very impressive, it looks like the bird play the wrong escalator game you sometimes see kids play. 
However its more likely that the pigeon don't understand that the handrail is moving, yes then it understand it might just play a bit. 

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9 hours ago, Randazzo said:

9Q0SSUl.gif

Very cute, and funny.

But *puts on nit hat*, Pigeons don't need forward speed to take off, they just flap their wings and go.  Some birds do run along the ground to take off, but these don't.  He's clearly trying to just land. 

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1 hour ago, Gargamel said:

He's clearly trying to just land.

So, the question is now: Given a downhill treadmill that matches the speed of a pigeon's wheels, can it land going uphill?

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So as I understand this topic, the premice is nonsensical- A plane on a treadmill that exactly matches the airplane wheel's dynamic friction with the foward prupulsion of at least one jet engine.

The first reason this is impossible, is that airplanes are, by design, extremely light, and friction (dynamic or otherwise) is dependant on weight. The treadmill could be going fast enough to melt the wheels, and it still wouldnt stop the plane from moving foreward.

But for the sake of the argument, lets skip that. Treadmill moving at trillions of miles per hour, plane stationary. The treadmill's friction with the air at that speed is remarkable, creating a blower. The exact effects on the plane depend on the size of the treadmill, but the moment the plane lifts from the ground, our nonsensical super-friction landing gear/treadmill combo doesnt work anymore, and the plane can acelerate normally into the headwind created by the treadmill.

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3 hours ago, Rakaydos said:

premice is nonsensical- A plane on a treadmill that exactly matches the airplane wheel's dynamic friction with the foward prupulsion of at least one jet engine.

No, it merely must match the tangential velocity.  

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9 minutes ago, DAL59 said:

No, it merely must match the tangential velocity.  

If the treadmill cannot create enough force on the plane through the landing gear bearing to oppose the plane's jet propulsion, the plane takes off. For there to be any debate at all, the landing gear has to be basically locked up to generate enough drag- and even then, it may well not be enough.

Edited by Rakaydos

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One last thing...because I'm tired and slightly loopy.

What if, instead of have a jet on a treadmill, you have a treadmill...on a jet. If you start the jet's engines, does the treadmill take off or remain stationary?

:)

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It's probably been said before, but all a aircraft needs is enough airflow over it's wings to get it off the ground. There are a few ultralights that can essentially take off with virtually no speed into a strong enough headwind.

I've always kinda wanted to stick a massive fan on top of a building and use it to land a conventional plane 'vertically'. I'd need a plane though, and a building, and a giant fan, and money.

None of which I have. :(

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13 hours ago, 55delta said:

One last thing...because I'm tired and slightly loopy.

What if, instead of have a jet on a treadmill, you have a treadmill...on a jet. If you start the jet's engines, does the treadmill take off or remain stationary?

:)

Did you tie the tradmill on a plane?

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7 hours ago, Xd the great said:

Did you tie the tradmill on a plane?

 

20 hours ago, 55delta said:

What if, instead of have a jet on a treadmill, *you* have a treadmill...on a jet.

I'm not the one who gets to decide what is attached to what. That's an exercise for the reader. :)

Edit: Just remember to include whether the treadmill is on top, inside, or attached to the plane (or similar) before you explain what might happen.

Edited by 55delta

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Impressive how long this discussion is.  I'll just toss in my own thoughts to extend it longer, if you have a front wheel drive car with the rear wheels on a treadmill and the front wheels on solid ground, could it drive away?

 

This may have been brought up but I gave up reading after the first few pages.

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2 minutes ago, Drethon said:

Impressive how long this discussion is.  I'll just toss in my own thoughts to extend it longer, if you have a front wheel drive car with the rear wheels on a treadmill and the front wheels on solid ground, could it drive away?

Of course not! Since no limits have been explicitly stated, the belt is physically forbidden from moving slower than c and the mass-energy of the system collapses the whole thing into a singularity. 

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On 6/22/2018 at 7:26 PM, 55delta said:

One last thing...because I'm tired and slightly loopy.

What if, instead of have a jet on a treadmill, you have a treadmill...on a jet. If you start the jet's engines, does the treadmill take off or remain stationary?

:)

If the treadmill is frictionless, and has no legs, the treadmill will slam into the back of the plane.

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