"alexy" wrote in message
...
You know, there is a fallacy in my reasoning that I am surprised no
one has called me on. We are used to aerodynamic drag, which increases
as the square of velocity. But if my memory of high school physics is
correct (and if Newton hasn't changed his mind in the last 40
yearsg) the friction between two bodies is a coefficient of friction
times the force normal to the motion (i.e., the weight of the plane).
No component for the relative velocities of the two bodies!

Hardly seemed worth it, given the opportunity to equivocate on the point.
In particular, while the idealized friction drag remains static relative to
speed, that ignores the possibility for change in the materials as the
friction heats them. Expansion may create a higher normal force (depending
on what part expands faster), and thus higher frictional drag. It also
ignores aerodynamic drag around the surface of the tire.

While I haven't bothered to calculate what these increases would be, it
seems safe to say that it's *possible* they would rise fast enough to offset
the available thrust before reaching the speed of light.

Basically, in an arm-chair, lay-person discussion like this, practically
*anything* is possible as you approach the speed of light. So why not just
invoke that, and ignore the details?

Pete