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Cake day: July 15th, 2023

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  • The wheels are attached to the plane so they move at the same time as the plane. But, I get what you’re trying to say, that the wheels are effectively being dragged by the plane, they’re not powering the movement.

    no. I’m saying that by the time the wheel is rolling, the plane’s is already moving forward, the engines have already overcome the drag in the wheels. the treadmill is locked to the wheels, not the plane. The plane would continue accelerating even as the wheels reported weird rates of turning.

    As for the (very brief) time delay, that’s a function of the plane’s gear’s suspension that is quite well sprung.

    the rate of roll on the tire is, effectively, decoupled from the airspeed (and groundspeed) of the plane. which makes this:

    No, by definition it’s the same. The conveyor moves with however much speed is necessary to stop the forward motion of the plane.

    … entirely different. an affixed anchor does not allow the free motion that a wheel would.

    You don’t need to deflate the tires, you merely need to increase the speed at which the conveyor moves to match the speed of the wheels.

    And one of a few things happen. Either the plane has enough engine thrust to overcome the acceleration induced by the wheels, and therefore takes off, or it does not.

    In the case that it does not, the wheels would continue spinning in increasing RPM until the plane begins moving backwards. because, again, the airspeed of the airplane is not dependent on the wheel’s RPM. Assuming the airplane doesn’t crash from suddenly becoming incredibly difficult to control… eventually it would take off anyhow. because the airflow over the wings would still generate lift. (though they would become horribly inefficient.) and therefore take off.

    this is of course ignoring the whole “can a pilot actually control that and manage a take off like that” thing. If you don’t want to grant godlike piloting skills, we could then just make the treadmill irrelevant and leave the brakes on.









  • Just to clarify; you understand that because the engines are pushing on the plane itself and not the wheels, by the time the wheels start moving, the plane is already moving relative to ground and air alike.

    Which, said another way, this thought problem appears confusing because it’s being considered from otherwise irrelevant reference frames.

    An anchor sufficient to keep the plane from rolling forward is different because the force it is apply is significantly greater.

    Sure, you can deflate the tires and increase the rate of spin on the wheels. But at that point, you might as well ask “can we creat a scenario where planes can’t take off”

    To which the answer is definitely “Yes”,

    And as a side note, if we assume the wheels are indestructible, which I’d argue is only fair, then even if what you’re saying is true and we ramp up the drag induced by the wheels sufficient to counter the engines… then the wind generated by the rolling treadmill would be producing a sufficient headwind for the plane to take off. (Remember, the air resistance of the treadmill’s belt moving will accelerate the air some.)

    But again, the wheels have almost zero drag to begin with, the speed at which the roll is independent of both the actual groundspeed and the airspeed of the airplane.

    If it has the thrust to over come friction at take off speeds, and at standing, then it has enough power to get to take off velocity eventually.

    On the other hand, this entire conversation assumes the thrust to weight ratio is less than 1. If it’s more than one, well they just…. Go straight up.


  • Except it’s not like attaching an anchor. The plane isn’t physically attached.

    The wheels will just roll double whatever the current ground speed is. If the plane has enough thrust to take off with the treadmill moving an inverse of its take off speed, then it has enough force to start rolling, too.

    At most, the force applied by the treadmill would be sufficient over enough time to lengthen the take off roll, but given enough space to do so, the plane will take off.

    To keep the plane from rolling forward; the treadmill would have to be able to apply an equal force as the engines, it can’t do that through the wheels- the wheels can only apply a force equal to their rolling resistance and friction in its mechanics.






  • So, another way to think about it is with Kites.

    The air flows around it the same way it would any other kind of aircraft, though they have effectively zero ground speed.

    They do differ in that, being tethered, they’re pulled through the air, with the wind providing the energy to stay up.

    But they’re still moving through the air, and the airfoils are inducing drag to convert some of that energy into lift.

    In both cases, the important speed is relative to the air, not the ground and not the treadmill. The wheels might impart some drag while they’re on the ground, but they’re never going to impart enough to overpower the engines- 747s typically take off at about 75% of their rated take off power, which means a longer take off roll, but less wear and tear.


  • From the included article-

    When it’s time to mate, eels are very determined to make it to their breeding site at the Sargasso Sea. The Sargasso Sea, a two-million-square-mile span of ocean,  is the site in which all freshwater eels mate

    It’s way the hell down there in the article, though. Apparently they travel to freshwater as larva.

    Eels are freaking weird, man.



  • It’s the interaction between the air and water that does it.

    If, hypothetically, you were to move something through the water at that speed, it wouldn’t shatter or just be stopped. There is significantly more drag, so it would come to rest sooner than in air but it wouldn’t just stop.

    For example, many small boats have very high rpm propellers that survive just fine- until they start cavitating.

    The reason a .50 cal or .308 shatter is the shock of hitting the surface tension, and it’s the shattering that allows the fragments to be slowed down so quickly.

    It’s also the reason they were surprised- they forgot to include surface tension in their initial model.