I thot that was a very insightful response regarding 0 G environment effects on natural convection. Ever since it popped into my head one day that 'heat rises' is only true in a fluid within a gravity gradient, I have been getting funny looks when I replied, "Not on the space station" to that 'truism'. Your post provides many interesting ramifications. You have done more thinking on it than I, I think.
On the issue of rolling vs skiing I have done some thinking and rethinking trying to fit it within my experiential and intuitive base. Below are my thots worked into your reply: +++++++++ There also seems a disconnect about movement in response to thrust since I perceive you using it in self contradictory ways in your argument. I know you know this, but to recap pertinent physics; a) Thrust is Force, b) Work is Energy ..= F X Distance = MVV/2 etc, c) Power is how fast Energy is delivered... FD/Time or F multiplied by Speed or FV. In other form, Torque X revolutions is equivalent to FD or E... and thus Torque X Rev/min is power This is our most common and easily understood form. It says that continuous torque at increasing RPM requires increasing power. Extrapolating comfortably from this, one realizes that a continuous rate of acceleration requires linearly increasing power. [[Note that my [[ above quote from my previous post]] was incorrect. The conveyor must apply constant counter thrust, therefore required conveyor HP increases linearly with time and quickly exceeds the planes HP and keeps rising. The rate that energy is stored in the wheels increases with time.]] .... Making the move over to thrust, I think of it as torque applied in a line rather than a spin. In tractor or auto terms, torque applied at the axle yields thrust at the ground contact. The thrust available is limited to engine max torque as transmitted thru the gearing in each gear. Max thrust varies with gear and decreases as the ratio provides for speed increases. - - A jet or rocket engine operates differently - they produce a thrust by throwing mass out the back end. During the acceleration of this Mass the engine experiences a thrust forward - - F=MA. Regardless of speed, these engines throw mass[fuel] at about the same rate and with the same acceleration. This causes a constant thrust force and gives constant Acceleration [actually, as you make reference to later, A increases some since thrown mass depletes the mass of the vehicle]. Since its speeding up, the product of thrust X distance, FD, [delivered Energy] is increasing from one second to the next. Energy per second is increasing. Thus the power of the engine increases with speed. The tires would never slip if their coefficient of friction at the belt contact was greater than the thrust to weight ratio of the plane. If the plane has enuf thrust to overcome tire traction there is no way the conveyor can prevent the plane from moving. Once breaking quasi static friction conditions the traction lessens, the force at slip presenting, as I said, the upper limit that you can apply a CounterThrust to the plane via the wheels. With high hysteresis rubber compounds the traction can be increased somewhat at the point that quasi-slip begins and the tractive benefit can be extended into actual slip. This is the realm of racing tires, where a graceful balancing act exists between the traction benefit and unavoidable decreased rolling efficiency- since the retarded rebound of the rubber moving up away from ground contact [leaving the contact patch] gives an effect of running uphill. -- In tires made for normal load bearing situations such as ours there is no tractive benefit at slip. Slipping just makes heat without increasing the reduced CT. This is quite noticeable on ice and wet surfaces. Youre right about slip causing a blowout shortly but the plane still wouldnt take off due extreme rolling resistance of flats. No magic from the tires is necessary to hold the plane still for a limited time. The acceleration needed from the conveyor is the hard part. Agreed. Lots of power from the conveyor- just like the rocket going faster at constant thrust develops increasing power. However the only power the plane must use against this slip 'CounterThrust' is the small CT force times the planes speed in its own inertial frame. Plenty of power left for acceleration and takeoff regardless how much heat energy is generated by the conveyor slip against the skis. A continuous thrust rocket makes more power the faster it goes, just as a continuous slip force uses more power as slip speed increases. [Same thing, yet you seem to assert one and deny the other.] A rocket in space [or a jet neglecting air resistance] would accelerate forever against a fixed counterforce [such as low coefficient slip] less than its thrust. A rotating engine applying force by mechanically pushing against something cannot achieve this because as the rotating pusher[wheel] is geared to be driven faster the torque to drive it decreases. Thus with conventional engines driving wheels, any steady state drag will limit max speed. You expend the fuel as slowly as possible by reducing the rate to the point where every particle that leaves can be let go at a velocity near c. Truth is tho, I didnt say that you got more work done when expending fuel at a slower rate. I said that an engine producing constant [or non diminishing] thrust produces more power as speed rises. I didnt say there was any difference in HP-hrs derived from the fuel at a slower use rate. Not sure how you got there from ...... where? Oh darn. Sure would be nice to be able to defy the laws of Physics.
There are flaws in the way you are dealing with friction. I believe it is a reference frame problem.
Also, there are disconnects that I cannot follow in your extrapolation of what I have said.
larry
